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Mismatched Power Tubes - Better Sound Effects Pedals, Units & Accessories
Old 20th March 2017
  #1
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Mismatched Power Tubes - Better Sound

So I was changing tubes in my amp the other day. I mainly use old General Electric tubes because my grandfather worked there for 50 years and bought me a lifetime supply of 6L6, 6V6, 12A_7, etc... back in the 80s.

Anyway, these aren't 'matched tubes' like you buy today, just boxes of tubes.

So I stuck a couple in my tweed twin and they sounded great. I decided I would bias it, so I checked the voltage and measured them and they were off quite a bit - maybe 9% or so.

Anyway, when this happens I have to go look for another tube that's closer to what's in there. I find one that's really close and it just didn't sound as good. I put the mismatched tube in and it sounded great. I figured maybe the tube I was trying to match was bad, so I found another close match and that didn't sound as good either.

I tried adding a rectifier back in (I usually have one pulled) and a few other things, but at the end of the day the mismatched tube sounded better to my ears.

Just to double check I stuck in a set of Groove Tubes silver series 6L6s that came in the Twin. They sounded terrible - but they were perfectly matched.

Anyway, I was wondering if anyone else had run into this.

## EDIT - the GTs were not silver series they were the Fender factory premium tubes - whatever that means.

Last edited by noah330; 21st March 2017 at 01:03 AM..
Old 20th March 2017
  #2
Heh-heh-heh.......... <chuckle>.......


Wanna know a dirty little secret?

Tube matching is a HI-FI thing....

Draw your own conclusions.
Old 20th March 2017
  #3

Dammit, I'm agreeing with Eppstein AGAIN....



-tINY

Old 21st March 2017
  #4
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Thread Starter
Quote:
Originally Posted by John Eppstein View Post
Heh-heh-heh.......... <chuckle>.......


Wanna know a dirty little secret?

Tube matching is a HI-FI thing....

Draw your own conclusions.
My grandfather worked at GEs transformer division for 50 years. I asked him about matched tubes and he didn't know what I was talking about.

At any rate, I'm going to go with what sounds best!
Old 21st March 2017
  #5
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Matched tubes? A little odd order distortion never hurt anyone. At least not any guitar player. Back in the day, matched meant having two of the same brand.

With resistor tolerance at ±10% and capacitors at ±20%, the notion that you're going to improve your distortion by matching your tubes is kind of wishful thinking. It's kind of like changing your windows. They're mostly better because they're new - not because the window technology has improved.

Last edited by kafka; 21st March 2017 at 01:22 AM..
Old 21st March 2017
  #6
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Quote:
Originally Posted by noah330 View Post
So I was changing tubes in my amp the other day. I mainly use old General Electric tubes because my grandfather worked there for 50 years and bought me a lifetime supply of 6L6, 6V6, 12A_7, etc... back in the 80s.

Anyway, these aren't 'matched tubes' like you buy today, just boxes of tubes.

So I stuck a couple in my tweed twin and they sounded great. I decided I would bias it, so I checked the voltage and measured them and they were off quite a bit - maybe 9% or so.

Anyway, when this happens I have to go look for another tube that's closer to what's in there. I find one that's really close and it just didn't sound as good. I put the mismatched tube in and it sounded great. I figured maybe the tube I was trying to match was bad, so I found another close match and that didn't sound as good either.

I tried adding a rectifier back in (I usually have one pulled) and a few other things, but at the end of the day the mismatched tube sounded better to my ears.

Just to double check I stuck in a set of Groove Tubes silver series 6L6s that came in the Twin. They sounded terrible - but they were perfectly matched.

Anyway, I was wondering if anyone else had run into this.

## EDIT - the GTs were not silver series they were the Fender factory premium tubes - whatever that means.
You can damage an amp if tubes aren't matched and your amp is not biased properly. But Groove tubes are like any other tubes. There are only a couple factories in the world that make tubes. They all come for the same couple of factories. Small companies just rebrand them. If the tubes sound bad then it is probably more the amp or a biasing issue wit hthe amp. Or it could be the preamp tubes that you don't like. All tubes these days are made for guitar amps and they are all pretty good. It's not like the 50s, 60s and 70s where some tubes did actually sound bad in guitar amps, since many tubes were low quality and made for AM Radio and Televisions and home appliances. These older tubes made by GE and Westinghouse or RCA didn't care as much about tolerances . Today 99% of new tubes have great specs. NOS are the ones you have to worry about. However GE and RCA did make some good tubes, but you'll never know till you put them
in your amp so don't pay too much for NOS stuff.

You can technically use unmatched tubes but you would have to be able to rebias the amp for each tube individually which is pretty tough to do with out great electronic measurement tools and know how. A 50 watt head for example wants 2 power tubes to have optimal idle current running to the plate voltage. If you have two tubes within a tighter variance with less current drift this is much easier to attain. That is the point of matched tubes. They are within a certain spec. However none of this guarantees they will sound good. It ultimately just means your amp will be more stable, the tubes will last longer and your amp will subsequently last longer.
Old 21st March 2017
  #7
Quote:
Originally Posted by chrischoir View Post
You can damage an amp if tubes aren't matched
Total, absolute nonsense.

Hogwash, balderdash, poppycock.

Back when the designs used in tube guitar amps were developed and more or less finalized there were no commercially available matched tube sets. They didn't exist.

Matched tube sets came about when audiophile DIY enthusiasts centered around publications like The Absolute Sound figured they could lower the distortion of their power amps by replacing all the resistors with 1% metal film and all the caps with 5% plastic types of various composition (standard caps at the time were often wax and paper, 20% or worse) and hand matching tubes on a Hickok mutual conductance tube tester they could reduce harmonic distortion by a measurable percentage. This stuff started catching on in the early 1970s. The power amp designs used in guitar amps were developed in the '50s. When I was a service tech starting in thew early '70s we were supplied output tubes from Fender in flats of 100. Out of these we had a rejection rate of 10% to maybe 25-30%, depending on the lot. We replaced tubes when they were bad or when they showed obvious signs of becoming worn out (getter turning grey instead of silver-black). There was no "mat5chingt of tubes" in guitar amps until Aspen Pittman started Groove Tubes in the late '70s, pushing the idea that you could get more power from a matched set.

Quote:
and your amp is not biased properly.
This is true - if your amp is not biased correctly it can be very destructive. But that doesn't have much to do with matched tube sets unless one of the tubes is really deviating from published spec. However some (mostly boutique) companies in recent years have taken to dangerously underbiasing their amps, because an amp on the verge of losing bias and going into destructive runaway tends to sound really good right before it blows. Such amps require more attention and care to tube selection due to the irresponsible design decisions.

Quote:
But Groove tubes are like any other tubes. There are only a couple factories in the world that make tubes. They all come for the same couple of factories.
It's more than a couple - there are that many in Russia alone.; Around 3 in China IIRC, and maybe 3 more in Eastern Europe. But there have never been THAT many tube companies. The biggest difference is that all the US companies are gone and the machinery scrapped, while in Europe at least some of the old machines were resold. Some of the old metallurgy has been lost, however.

Quote:
Small companies just rebrand them.
Rebranding has been around since the '50-s, if not before. By the late '60s/early '70s there were so many different rebrander4s it was ridiculous - far, far mo0re than today. Every electronics chain and mail order house had its own brand of tubes, and several brands were sold in groceries, drug stores, and variety stores, most of which had (really crappy but impressive looking) tube testers in cabinets containing large stocks of common tubes for TVs, radios, Hi-Fi sets, whatever. If your amp blew a tube you could get a replacement at the nearest Safeway or Rexall Drug. If you were lucky it might even last a while - or not, because many of these off-brand tubes were seconds or rejects.

Quote:
These older tubes made by GE and Westinghouse or RCA didn't care as much about tolerances
Not true, if you stuck to the top brands.
Quote:
. Today 99% of new tubes have great specs.
Also not completely true. One big problem is that much of the metallurgy of the original top brands has been lost - a lot ofg it was treated as trade secrets so there is no available documentation, plus there are problems with environmental issues in many areas (which is why there are no US tubes now.)

Quote:
NOS are the ones you have to worry about. However GE and RCA did make some good tubes, but you'll never know till you put them
in your amp so don't pay too much for NOS stuff.
You have to really know your NOS tube dealer. NOS tubes are a constantly dwindling resource, and some of the tubes hitting the market now are still around because they were rejects back in the day. Since NOS tubes are now often absurdly expensive ($200 for a 12AX7 that originally cost $1.50-$2!) you need to be sure of a dealer's return policy and guarantee.

Quote:

You can technically use unmatched tubes but you would have to be able to rebias the amp for each tube individually which is pretty tough to do with out great electronic measurement tools and know how.
Er, no. Not really, unless you have something like a Fender 400PS,which has an absurd 30 step alignment procedure

Most guitar amps don't even have provisions for biasing tubes individually.

Quote:
A 50 watt head for example wants 2 power tubes to have optimal idle current running to the plate voltage.
Huh? Idle current running to the plate voltage? That doesn't exactly make sense, but maybe you're just not expressing yourself clearly. And, of course, the number of tubes required for a given wattage depends on tube type. You could have 2 6L6s or EL34s, 4 6V6s, or 6 EL84s for 50 watts.
Old 21st March 2017
  #8
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When I got the amp I took out the Groove Tubes and put in some old NOS RCA 12AY7s because I had them around. I pulled out the rectifiers and put a pair of NOS GE 5U4s and NOS GE 6L6s.

The sound was better right away. The 12AY7s made a difference and it's what would have been in this originally. I remember my grandfather and his friends from GE thinking I didn't know what I was talking about when I asked about 'matched tubes'. I sent him an ad from Guitar Player or something and he had never heard of such a thing.

Since he fixed my amp when it was broken I trusted him. Like I said, he did work in probably one of the most advanced electronics places in the world at the time (GE's Pitsfield, MA plant) and since nobody there seemed concerned I really wasn't.

At the end of the day I hear with my ears. Things sound a lot better like this. I won't intentionally mismatch tubes, but I'll use the combination that sounds better over the ones that measure better.

Someone should create 'harmonically mismatched tubes' and sell them over on TGP.
Old 21st March 2017
  #9
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Quote:
Originally Posted by tINY View Post

Dammit, I'm agreeing with Eppstein AGAIN....



-tINY

Me too. It's a sign of the end days......
Old 21st March 2017
  #10
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John is a living national treasure.
Old 21st March 2017
  #11
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I found there are few rules when it comes to tube amps. My 78 Princeton had new $20 Tungsols in it when I bought it. It sounded great so as I have lots of nos tubes here, I put my 50's RCA's $130 in there and it didn't sound as good.
I suspect that if it had a bias pot, I could bias the RCA's to perhaps even sound better but it doesn't.
The lesson I learned over the year is if a tube amp sounds good, don't mess with it until you have to.
Old 21st March 2017
  #12
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Quote:
Originally Posted by norfolk martin View Post
Me too. It's a sign of the end days......
It's safe because we are on hallowed ground - talking about tubes and not digital stuff.
Old 21st March 2017
  #13
Quote:
Originally Posted by grannis View Post
It's safe because we are on hallowed ground - talking about tubes and not digital stuff.
Hey, I like digital stuff - if it's GOOD digital stuff...
Old 21st March 2017
  #14
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kafka's Avatar
Now if only you could swap the tubes in your amp sim, we'd have something to argue about.
Old 21st March 2017
  #15
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Quote:
Originally Posted by chrischoir View Post
You can damage an amp if tubes aren't matched...
Dude. Where do you get your info?
Old 21st March 2017
  #16
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Quote:
Originally Posted by kennybro View Post
Dude. Where do you get your info?
Apparently, where the sun don't shine.
Old 22nd March 2017
  #17
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Thread Starter
Quote:
Originally Posted by kafka View Post
Now if only you could swap the tubes in your amp sim, we'd have something to argue about.
They actually are called 'toan capsules' and one is for the Robben Ford sound and the other for the Eric John Stone sound. I kid you not.
Old 22nd March 2017
  #18
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Quote:
Originally Posted by John Eppstein View Post
Total, absolute nonsense.

Hogwash, balderdash, poppycock.

Back when the designs used in tube guitar amps were developed and more or less finalized there were no commercially available matched tube sets. They didn't exist.

Matched tube sets came about when audiophile DIY enthusiasts centered around publications like The Absolute Sound figured they could lower the distortion of their power amps by replacing all the resistors with 1% metal film and all the caps with 5% plastic types of various composition (standard caps at the time were often wax and paper, 20% or worse) and hand matching tubes on a Hickok mutual conductance tube tester they could reduce harmonic distortion by a measurable percentage. This stuff started catching on in the early 1970s. The power amp designs used in guitar amps were developed in the '50s. When I was a service tech starting in thew early '70s we were supplied output tubes from Fender in flats of 100. Out of these we had a rejection rate of 10% to maybe 25-30%, depending on the lot. We replaced tubes when they were bad or when they showed obvious signs of becoming worn out (getter turning grey instead of silver-black). There was no "mat5chingt of tubes" in guitar amps until Aspen Pittman started Groove Tubes in the late '70s, pushing the idea that you could get more power from a matched set.

This is true - if your amp is not biased correctly it can be very destructive. But that doesn't have much to do with matched tube sets unless one of the tubes is really deviating from published spec. However some (mostly boutique) companies in recent years have taken to dangerously underbiasing their amps, because an amp on the verge of losing bias and going into destructive runaway tends to sound really good right before it blows. Such amps require more attention and care to tube selection due to the irresponsible design decisions.



It's more than a couple - there are that many in Russia alone.; Around 3 in China IIRC, and maybe 3 more in Eastern Europe. But there have never been THAT many tube companies. The biggest difference is that all the US companies are gone and the machinery scrapped, while in Europe at least some of the old machines were resold. Some of the old metallurgy has been lost, however.

Rebranding has been around since the '50-s, if not before. By the late '60s/early '70s there were so many different rebrander4s it was ridiculous - far, far mo0re than today. Every electronics chain and mail order house had its own brand of tubes, and several brands were sold in groceries, drug stores, and variety stores, most of which had (really crappy but impressive looking) tube testers in cabinets containing large stocks of common tubes for TVs, radios, Hi-Fi sets, whatever. If your amp blew a tube you could get a replacement at the nearest Safeway or Rexall Drug. If you were lucky it might even last a while - or not, because many of these off-brand tubes were seconds or rejects.



Not true, if you stuck to the top brands.


Also not completely true. One big problem is that much of the metallurgy of the original top brands has been lost - a lot ofg it was treated as trade secrets so there is no available documentation, plus there are problems with environmental issues in many areas (which is why there are no US tubes now.)



You have to really know your NOS tube dealer. NOS tubes are a constantly dwindling resource, and some of the tubes hitting the market now are still around because they were rejects back in the day. Since NOS tubes are now often absurdly expensive ($200 for a 12AX7 that originally cost $1.50-$2!) you need to be sure of a dealer's return policy and guarantee.



Er, no. Not really, unless you have something like a Fender 400PS,which has an absurd 30 step alignment procedure

Most guitar amps don't even have provisions for biasing tubes individually.



Huh? Idle current running to the plate voltage? That doesn't exactly make sense, but maybe you're just not expressing yourself clearly. And, of course, the number of tubes required for a given wattage depends on tube type. You could have 2 6L6s or EL34s, 4 6V6s, or 6 EL84s for 50 watts.
john you took nearly comment out of context...for one I stated you can
damage your amp if it is NOT BIASED and your tubes aren't matched... That was complete sentence.. You cherry picked a few lines and skew it to try and be a internet tough guy
Old 22nd March 2017
  #19
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Quote:
Originally Posted by kennybro View Post
Dude. Where do you get your info?
if your tubes aren't matched AND THE AMP IS NOT BIASED PROPERLY

re-read the original sentence

everyone knows that an amp that is improperly biased can cause lots of issues. My recommendation is to take a basic electronics class and you will get the info you need clownboy
Old 22nd March 2017
  #20
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kennybro's Avatar
Quote:
Originally Posted by chrischoir View Post
if your tubes aren't matched AND THE AMP IS NOT BIASED PROPERLY

re-read the original sentence

everyone knows that an amp that is improperly biased can cause lots of issues. My recommendation is to take a basic electronics class and you will get the info you need clownboy
Yes, an "out of bias" amp can reek some havok; but vastly out of bias. Tubes definitely do perform at best with matching idle plate current. In reality, most players amps run unmatched/out of bias.

Most players use the same tubes for years, and never check bias. I'm not a tube guru, but my tech manages the APS for Argonne (BIG Klystron tubes; this dude knows tubes), and his take is that if you buy a matched set and play a few gigs, you very likely no longer have a matched set.

Everything in perfect adjustment is best practice, but almost never reality.

Last edited by kennybro; 22nd March 2017 at 04:17 AM..
Old 22nd March 2017
  #21
Quote:
Originally Posted by chrischoir View Post
john you took nearly comment out of context..
I don't see how.

Quote:
.for one I stated you can
damage your amp if it is NOT BIASED and your tubes aren't matched...
As I said,if your bias is very badly off spec or you bias circuit is defective it can damage your amp. However if you bias isn't exactly optimum - like it you change tubes in a functioning amp without rebiasing - you are not going to damage the amp unless the amp was biased wrong (too hot) to begin with. It should be noted that it's something of a fad to bias amps just as hot as possible without them going into runaway and cherrying the tubes. This is a very BAD IDEA.

Running mismatched tubes will not damage any properly designed, normal tube amp. There have been a couple of badly designed amps that are3 running their power tubes way out of spec that can be damaged by not running tubes that conform to the manufacturer's stated spec. These are not normal amps and should not be serviced by anyone other than a factory authorized service facility. Fortunately these amps are extremely rare For example the infamous Fender 400PS requires a 30 step alignment procedure when changing tubes and can only use one particular type of GE 6550A power tube which is extremely rare and prohibitively expensive. You can't use any other tube and have the amp remain stable unless you do specific modifications, after which the amp won't meet spec - and still isn't stable. Even then the amp does not require a matched tube set - because there are individual adjustments for each of the output tubes.

The idea that running unmatched power tubes will damage your amp is a lie promoted by vendors of matched tube sets so they can sell expensive matched sets to people who don't know any better. I've worked on tube amplifiers for over half a century and I've NEVER encountered any guitar amp that was damaged by using unmatched tubes, ever. (I have encountered a 400PS damaged by using substandard - non GE - tubes, but that's a different story. I hate the 400 PS, BTW, it was an extremely bad design created by a guy with no previous experience with guitars amps and no understanding of typical working conditions.


Quote:
That was complete sentence.. You cherry picked a few lines and skew it to try and be a internet tough guy
No. I'm not a "tough guy". I just object strongly to people who spread myths, sales hoopla, and other bad "information" as fact.
Old 22nd March 2017
  #22
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I don't want to beat a dead horse but the mot common output tubes, 6L6s will in most cases operate on a bias anywhere from around - 35vdc to around - 70vdc without harm. Some designs under certain loads won't handle the lower limit well but that will immediately make itself known by cherry red plates. By raising to around -38 to -40 virtually all designs will operate without harm. This isn't plus or minus 10 or 20 or even 50 percent! The usable window is extremely forgiving with tubes. It has been tube sellers that have tried to employ FUD to make it's potential customers fear otherwise.... apparently with some success

Last edited by enorbet2; 23rd March 2017 at 11:10 AM.. Reason: typos
Old 22nd March 2017
  #23
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kafka's Avatar
Quote:
Originally Posted by enorbet2 View Post
I don't want to bet a dead horse
This is good advice. Never bet on the dead one. They rarely win.
Old 23rd March 2017
  #24
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Quote:
Originally Posted by kafka View Post
This is good advice. Never bet on the dead one. They rarely win.
OMG. Sorry for typos. Fixed now. Thanks for your humorous notification.
Old 23rd March 2017
  #25
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'Stop, your both right; tubes are two mints in one!'

Interesting thread...excellent observations and very entertaining!

One of the wisest men I ever knew, Dick Rosmini, who was both an amazing musician, a Tiffany photographer, and also a self taught tech genius who was in part responsible for the launch Tascam Porta-Studio (Dick wrote the manual) which begat the 'home studio' craze and changed our industry inviting musicians into the production process, use to say this; 'there are a lot of things we can measure that don't matter, and there are a lot of things that matter that we can't measure.'

I think this discussion illustrates that.

The post starts w/ a 'musician type' saying one set of tubes 'sounds better' than another set of tubes...and that changing tubes makes a big difference. And that a matched set didn't sound as good as his old unmatched NOS GE set that his Grandfather gave him (GREAT grand dad BTW!) .

Of course this is a subjective measurement...proving 'there are things that matter we can not measure'. And he is absolutely right!

Then an obviously experienced 'amp tech type' replies that in his years of experience fixing amps matching tubes makes no 'technical' (measurable?) difference AT ALL (or words to that effect), and that mismatched tubes can not damage an amp (albeit if the amp is not seriously under biased).

This is an objective observation based on years of real bench experience, and I believe he is absolutely correct as well.

But I also think this proves 'there are things we can measure that do not matter'.

IMNSHO, the secret to unraveling these kind of mysteries, and or reconciling these contrasting (totally valid) opinions is finding ways to make 'meaningful measurements'. That can also lead to making a valid product that 'those with ears' can appreciate. But you must also understand that not everyone has those pesky musician 'mosquito ears' like Eric Johnson (who ONLY wanted 4 1/2 rated early Chinese 'coke bottle' 6L6s in his amps...and he COULD clearly hear the difference).

In general, I would agree with much of what has been said here on this very interesting post, proving the issue may never be 'settled' either way!

But mostly I side with the comments here that the actual tube design, and execution of that design in the manufacturing processes down to the purity of the cathode Nickle, makes a FAR bigger difference than matching can ever make. I think that most musicians will prefer the NOS RCA Black plate or the Clear top GE 6L6 to the early Russian 6L6 types...although the distance is closing with many of the newly developed types now made in China and Slovakia for example. "Matching", however you may choose to do that, falls into achieving that last 20% of result (or more like 10% really, as compared to the difference of manufacture). So, IMNOHO pre selection of preamp tubes, and/or matching power tubes 'can' make a noticeable improvement (to some) in both sound and reliability. But I don;t think it is not a 'huge' difference. Kind of like fine tuning an engine with balanced pistons...important to the top drivers, but not so much for the daily commuter,

I also am a life time believer in the 80/20 rule; you get 80% of the result with 20% of the effort, and that that last 20% of 'result to find 'perfection' will take (at least) another 80% of your time and investment.

So this 'tube talk' discussion divides along those lines.

For most 'musician types' seeking the ultimate tone...the goal is 100%, nothing less will do...a constant 'tone quest'. And of course, since sound is so subjective...not every musician will agree on what 100% actually is. But they can usually agree that tubes sound better (in guitar amps), and that various tubes (matched or mis matched and/or brand specific) sound VERY different!

For most the 'amp tech types' I have known (and loved), I think they fall into the more forgiving 80% goal orientated category, knowing that 'close' (with regard to biasing amps) is good enough, but also knowing thru frustrating experiences they will never please a musician type seeking that last 20%.

For most 'product designer types' (like me), I think how we approach the task depends on if you are in this for the music, or the business of it...and also if you are employed by bean counters, musicians, or out on your own.

If you work for Fender on the amp QC Line (or in the engineering department) the wide range of tube performance quality (and reliability, and sound) is a paramount consideration. So you MUST be in the pragmatic 80% group or you would never be able to consistently build or sell an amp for reasonable money!

But if you one of the many new self employed amp builders out there (so called boutique hand builders) then you MUST live for achieving that last 20%...using the best of the best...and your amps will be priced accordingly.

When I finally got around to building my own tubes after 15 years of selecting and matching everything on the market (new and old), and as I began to design and built 13 exclusive original types over the following 15 years at 4 of 6 of the receiving tube factories still in existence when I started 40+ years ago (now down just 3 1/2), I quickly realized that building tubes is all about the 100%. If you don't get EVERY DETAIL just right, you got nothing. If you just get 'close' you wind up with lousy sounding tubes...like the ones we always compare to NOS tubes and generally agree to be sub par (to be kind). But that's a subject for another time...it's off to work I go...great clients coming into the studio today...which is far less challenging, and much more fun than building tubes!

Just my 2 cents, and worth about what I am charging...
Old 23rd March 2017
  #26
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Thread Starter
Aspen,

Thanks so much for chiming in. I've been a big fan of yours for years. I have the first edition Tube Amp Book and spent my teenage years lusting after the combinations of guitars/amps in the center.

When I found my 57 6120 and 6160 (like the one pictured in your book) I was thrilled to finally play the amp I had read about.

You're right. The sound is subjective. To my ears things sound better now. Maybe someone else would disagree.

- Loved your studio tour on YouTube!
Old 23rd March 2017
  #27

I think we can come up with measurement regimes that will quantify the "subjective" parts of "good sounding guitar amps". Let's face it: Guitar amps distort things and people like particular distortions. Up to now, the most sophisticated measurements of distortion have been X-order harmonic distortion vs frequency. And, you mostly see that in PA speaker specs.

Transient distortions? You're lucky to get the waveform response to a step-function or square wave in anything outside of high-precision devices (where any ringing is a detriment). To quantify the frequency and damping of the transient response is a waste of time if you are selling to guitarists (or nearly anyone else).

So, the "magic" happens by trial and error and people hope it's repeatable...



-tINY

Old 29th March 2017
  #28
Quote:
Originally Posted by Aspen Pittman View Post
Interesting thread...excellent observations and very entertaining!

One of the wisest men I ever knew, Dick Rosmini, who was both an amazing musician, a Tiffany photographer, and also a self taught tech genius who was in part responsible for the launch Tascam Porta-Studio (Dick wrote the manual) which begat the 'home studio' craze and changed our industry inviting musicians into the production process, use to say this; 'there are a lot of things we can measure that don't matter, and there are a lot of things that matter that we can't measure.'

I think this discussion illustrates that.

The post starts w/ a 'musician type' saying one set of tubes 'sounds better' than another set of tubes...and that changing tubes makes a big difference. And that a matched set didn't sound as good as his old unmatched NOS GE set that his Grandfather gave him (GREAT grand dad BTW!) .

Of course this is a subjective measurement...proving 'there are things that matter we can not measure'. And he is absolutely right!

Then an obviously experienced 'amp tech type' replies that in his years of experience fixing amps matching tubes makes no 'technical' (measurable?) difference AT ALL (or words to that effect), and that mismatched tubes can not damage an amp (albeit if the amp is not seriously under biased).

This is an objective observation based on years of real bench experience, and I believe he is absolutely correct as well.

But I also think this proves 'there are things we can measure that do not matter'.

IMNSHO, the secret to unraveling these kind of mysteries, and or reconciling these contrasting (totally valid) opinions is finding ways to make 'meaningful measurements'. That can also lead to making a valid product that 'those with ears' can appreciate. But you must also understand that not everyone has those pesky musician 'mosquito ears' like Eric Johnson (who ONLY wanted 4 1/2 rated early Chinese 'coke bottle' 6L6s in his amps...and he COULD clearly hear the difference).

In general, I would agree with much of what has been said here on this very interesting post, proving the issue may never be 'settled' either way!

But mostly I side with the comments here that the actual tube design, and execution of that design in the manufacturing processes down to the purity of the cathode Nickle, makes a FAR bigger difference than matching can ever make. I think that most musicians will prefer the NOS RCA Black plate or the Clear top GE 6L6 to the early Russian 6L6 types...although the distance is closing with many of the newly developed types now made in China and Slovakia for example. "Matching", however you may choose to do that, falls into achieving that last 20% of result (or more like 10% really, as compared to the difference of manufacture). So, IMNOHO pre selection of preamp tubes, and/or matching power tubes 'can' make a noticeable improvement (to some) in both sound and reliability. But I don;t think it is not a 'huge' difference. Kind of like fine tuning an engine with balanced pistons...important to the top drivers, but not so much for the daily commuter,

I also am a life time believer in the 80/20 rule; you get 80% of the result with 20% of the effort, and that that last 20% of 'result to find 'perfection' will take (at least) another 80% of your time and investment.

So this 'tube talk' discussion divides along those lines.

For most 'musician types' seeking the ultimate tone...the goal is 100%, nothing less will do...a constant 'tone quest'. And of course, since sound is so subjective...not every musician will agree on what 100% actually is. But they can usually agree that tubes sound better (in guitar amps), and that various tubes (matched or mis matched and/or brand specific) sound VERY different!

For most the 'amp tech types' I have known (and loved), I think they fall into the more forgiving 80% goal orientated category, knowing that 'close' (with regard to biasing amps) is good enough, but also knowing thru frustrating experiences they will never please a musician type seeking that last 20%.

For most 'product designer types' (like me), I think how we approach the task depends on if you are in this for the music, or the business of it...and also if you are employed by bean counters, musicians, or out on your own.

If you work for Fender on the amp QC Line (or in the engineering department) the wide range of tube performance quality (and reliability, and sound) is a paramount consideration. So you MUST be in the pragmatic 80% group or you would never be able to consistently build or sell an amp for reasonable money!

But if you one of the many new self employed amp builders out there (so called boutique hand builders) then you MUST live for achieving that last 20%...using the best of the best...and your amps will be priced accordingly.

When I finally got around to building my own tubes after 15 years of selecting and matching everything on the market (new and old), and as I began to design and built 13 exclusive original types over the following 15 years at 4 of 6 of the receiving tube factories still in existence when I started 40+ years ago (now down just 3 1/2), I quickly realized that building tubes is all about the 100%. If you don't get EVERY DETAIL just right, you got nothing. If you just get 'close' you wind up with lousy sounding tubes...like the ones we always compare to NOS tubes and generally agree to be sub par (to be kind). But that's a subject for another time...it's off to work I go...great clients coming into the studio today...which is far less challenging, and much more fun than building tubes!

Just my 2 cents, and worth about what I am charging...
Hi Aspen, great to see you in this thread. I believe that I'm the "experienced amp tech type"* you referred to. I'd like to clear up a couple of points.

First, I never said that matched tubes "make no 'technical' (measurable?) difference AT ALL ", I said that mismatched tubes will not damage a properly designed amp and that back in the old days (the period that most basic amp designs were developed) nobody paid any attention to that. Matching tubes DOES make a difference, you can see it on a scope at least in more extreme cases and it will definitely show up on a distortion analyzer. My point was that it's not actually necessary and it's really up to the musician whether the difference in audio quality is more desirable one way or the other. Audiophile types will always go for matched power tubes as it lowers distortion, but guitar amps are a different matter and often design choices are made (in this case I'm counting tube choice as a matter of "design", for lack of a better term) that don't follow the "rules" of formal amp design. When you get right down to it, tube choice and how it affects tone is up to the musician.

"But I also think this proves 'there are things we can measure that do not matter'."

Absolutely. There are also things that we can measure that DO matter, but we don't fully understand HOW they matter because human taste is not fully quantifiable and when you're dealing with artistic types, well, they're weird beasts! You can have two amps with identical distortion specs that sound very different. You can have one amp and one guy will love it and another will hate it. You can have an amp tone that sounds horrible in isolation but fits the track and song perfectly (which is why the solo button is often NOT your friend.) It's these thing that make working at the interface between tech and art so wild, wonderful, and fun. (And I do know that you like your fun..l.)

And you CAN please a musician seeking that last 20% - for about 30 minutes, give or take.

When I was touring I worked for a band with a Boogie endorsement and since our lead guitar player was a "golden ear" type who could definitely detect when his power tubes were more that 3 days old (at one 45 minute set per day) I had a big Anvil trunk full of Boogie 6L6s to keep him in fresh tubes. Every week or so the guitar tech from BOC, who were headlining, would come by and grab a bunch of our used tubes for their amps - they apparently liked them a little "broken in". Go figure.... (I wish I had just half of the perfectly good tubes we threw out with that band...)

I've found that having worked on both the guitar amp side of things and the sound reinforcement/recording/hi-fi side of things gives a perspective that can be somewhat lacking in those techs with a less broad range of experience. It can bhe difficult to hold two somewhat contradictory viewpoints in mind and understand and believe in both of them...



* "Experienced amp tech type"..... <chuckle> You may or may not remember it (it was a long time ago and ended in one of those nights that are not necessarily conducive to good memory) when I was the service tech at the late lamented Don Wehr's Music City in SF, you, my good friend Joey Swails (who was running the keyboard department at the time) and I spent an evening that started at the store, proceeded to a restaurant on Fisherman's Wharf for dinner and drinks, and culminated at the south of market apartment of our friend Electra, who was the other sound engineer at The Mabuhay Gardens at the time. I remember having a long discussion with you about various matters concerning tubes of which the high point (at least as far as I can remember) was a discussion of VF-14 tubes. Wish I could remember the details of our conversation that night.... That would have been around 1980, give or take a year or two. (Ah, youth...)

I should also thank you for the bar trick you were demonstrating at AES about 10 years ago - the one with the "round metal ball" and the copper tube. I put that one to good use....
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