The No.1 Website for Pro Audio
 Search This Thread  Search This Forum  Search Reviews  Search Gear Database  Search Gear for sale  Search Gearslutz Go Advanced
SVT Classic Question
Old 21st August 2007
  #1
Lives for gear
SVT Classic Question

My local music store has agreed to give me a brand new SVT Classic Bass head since mine, under warranty, keeps blowing the same tube. The only catch is, according to the sales guy, is that all the new SVT Classic heads are built somewhere in Asia, not in the USA like mine. Does anyone know if Ampeg has cut cost anywhere or is the head exactly the same?
Old 21st August 2007
  #2
Lives for gear
 

i'ld sooner find out why that tube position blows and fix it.... it's an svt for gods sake it's not rocket science....
Old 21st August 2007
  #3
Lives for gear
Quote:
Originally Posted by dementedchord View Post
i'ld sooner find out why that tube position blows and fix it.... it's an svt for gods sake it's not rocket science....
And I'm a bass player, not an electrician....I've been to the store three times to have the same problem fixed, and had to borrow crappy loaner amps for months. The store gave me the option of sticking with my old head (which is a little beat up from the road) or a brand new SVT made in Asia. If the USA and ASIA models are identical in construction and parts, I'll probably take the new one at no cost. Does anyone have any experience with new SVT's?
Old 21st August 2007
  #4
Lives for gear
 
Wavebourn's Avatar
 

It is in the design: if something is wrong with a phase inverter tube's sockets sharp peaks damage output toobs, resistors in their filaments to ground (2 and 3 legs are too close for a spark), output transformers...

It is a well advertised amp, but has some design mistakes.
Old 22nd August 2007
  #5
Lives for gear
Quote:
Originally Posted by Wavebourn View Post
It is in the design: if something is wrong with a phase inverter tube's sockets sharp peaks damage output toobs, resistors in their filaments to ground (2 and 3 legs are too close for a spark), output transformers...

It is a well advertised amp, but has some design mistakes.
Are you saying that the Asian SVT model is different in design or that the reason my tube keeps blowing is because there's something wrong with the phase inverter tube's socket?
Old 22nd August 2007
  #6
Lives for gear
 

why are you picking on the phase invertor??? is this a documented issue???? which tube positionally is blowing repeatedly???? have you tried calling ampeg to see if there are known issues???? or better still you sound like you would prefer the new one so do it....
Old 22nd August 2007
  #7
Lives for gear
Quote:
Originally Posted by dementedchord View Post
why are you picking on the phase invertor??? is this a documented issue???? which tube positionally is blowing repeatedly???? have you tried calling ampeg to see if there are known issues???? or better still you sound like you would prefer the new one so do it....
The new one would be nice...but I want to make sure the new models built in Asia are built exactly the same with the exact same parts as they were in the USA. Some companies tend to redesign the internal components when they outsource and I want to make sure that they're the same before committing to the new model.
Old 23rd August 2007
  #8
Gear Guru
 
FFTT's Avatar
 

I would only trade that amp for an SVT VR model even if it costs you a bit more.
Old 23rd August 2007
  #9
Lives for gear
 
Wavebourn's Avatar
 

Quote:
Originally Posted by JB872 View Post
Are you saying that the Asian SVT model is different in design or that the reason my tube keeps blowing is because there's something wrong with the phase inverter tube's socket?
I am saying that the original SVT design has weak points.
I did not mention ground loops in the pre-amp module that cause hum and HF oscillations....

It does not matter who do you give your documentation for manufacturing; any nation will build what you've designed. And if your design has weak points no manufacturer will probably correct them, no matter are they German, Chinese, etc...

That's why I always spend more time on R&D, that's why I am unhappy with the current situation when together with mass production experimental manufacturing went abroad so cost of testing of new design is very high.

SVT is one of good designs, but it is not ideal. It has weak points. It is up to you, either to accept the fact, or to blame on current manufacturers.
Old 23rd August 2007
  #10
Lives for gear
 
Wavebourn's Avatar
 

Quote:
Originally Posted by dementedchord View Post
why are you picking on the phase invertor??? is this a documented issue???? which tube positionally is blowing repeatedly???? have you tried calling ampeg to see if there are known issues???? or better still you sound like you would prefer the new one so do it....


"Why are you picking on a bottle neck when it's bottom is so wide???"

Because I am Designer and Technologist. Because I've modified such amps for my friends and know what I am talking about.

If you are affiliated with Ampeg design or manufacturing, my e-mail address and phone numbers are well known. Why are you posting this message on a worldwide forum?
Old 23rd August 2007
  #11
Gear Addict
 

I heard that they were moving the B series stuff overseas, and the eventaully plan was to move everything overseas. I was told it was going to be years before the classics would be built overseas. Call ampeg, theyll tell you.
Old 23rd August 2007
  #12
Lives for gear
 
Wavebourn's Avatar
 

Quote:
Originally Posted by bluestarbass View Post
I heard that they were moving the B series stuff overseas, and the eventaully plan was to move everything overseas. I was told it was going to be years before the classics would be built overseas. Call ampeg, theyll tell you.
There are always 2 options: either to improve production quality, or to save on costs of manufacturing. Choosing both options together is called "optimizing".
Old 23rd August 2007
  #13
Lives for gear
I'll probably end up trading it in for the new one since nothing has been changed about the amp except where it's built or maybe try upgrading to the SVT-VR. Does anyone know what the difference are between the SVT-CL and SVT-VR?
Old 23rd August 2007
  #14
Lives for gear
 

no i dont work for ampeg... unless you count @15yrs of doing warrantee repair at an independent facility... and while i think we would both agree that all design work is a compromise... i dont see what your generalizations about this particular piece accomplishes... this amp in various forms has been among the best bass amps ever produced.... where's yours?????
Old 23rd August 2007
  #15
Lives for gear
 
Wavebourn's Avatar
 

RMS Power Output (2 Ohms): 300-Watts
RMS Power Output (4 Ohms): 300-Watts
Preamp: Tube (2 x 12AX7, 1 x 12AU7)
Driver Tube(s): 2 x 12AU7, 1x 12AX7
Power Amp: Tube (6 x 6550)
Tone Controls: 3-Band
Mid Tone Control: 5-Position Selector
Ultra High/Low: Yes
Balanced Line Out: Yes
Preamp Out/Power Amp In: Yes
Slave Output: Yes
Dimensions (W x H x D inches): 24 x 11.5 x 13
Weight: 80 Pounds

Preamp: Tube (2 x 12AX7, 1 x 12AU7)
Driver Tubes: (1 x 12AX7, 2 x 12AU7)
Power Amp: Tube (6 x 6550)
RMS Power Output: 300-Watts @ 2 ohms
RMS Power Output: 300-Watts @ 4 ohms
Tone Controls: Bass, Mid, Treble
Mid Tone Control: 3-Position Rocker Switch
Ultra Low/High Boosts: Yes
Speaker Connections: Neutrik Speakon® and 1/4"
Balanced Line Out: Yes (Transformer)
Preamp Out/Power Amp In: Yes
Dimensions (W x H x D inches): 24 x 11.5 x 12.75
Weight: 85 pounds

Play with both then let me know what do you like in them and want to combine, what to change, what to add.

I am designing one currently with end results in mind (tone, tone, and tone, depending on whispering, pianissimo, piano, mezzo-piano, forte, mezzo-forte, forte, forte-fortissimo, crushing rocks, the bass have to cry, speak, whisper, i.e. transfer emotions).
It will have a "clean" channel with classical Fender-style controls, and Wavebourn-specific channel that simulates a concert piano bass strings (extended in dynamics) for better dynamic articulation. The latest one will have EQs, digital delays, controlled dynamically to give more tone flexibility depending on how you touch/kick your strings for the sound. I've started to develop it for my friend John Pursel, but I lost contact with him after he left his job in AMD so e-mails don't go through. So, if anybody knows John please tell him I remember his style of acoustic and electric bass playing and still working on a new design inspired by his sounds.
Old 23rd August 2007
  #16
Lives for gear
 
Wavebourn's Avatar
 

Quote:
Originally Posted by dementedchord View Post
this amp in various forms has been among the best bass amps ever produced.... where's yours?????
In the future (I mean mass production) :D

I'm looking for partners to start manufacturing of a real high end gear. I don't mean better then Fender did; I mean about a gear of a modern age, using parts available thanks to mass production of computers and cars. Fender did not have them.

Now, please look at schematics and see what happens when some contact gets loose. How the resulting peak is related to a normal signal? How transients will go through the amp? Can you calculate voltages, currents, powers, depending on what is implemented? How contacts in a phase splitter can be loose? Can a tube socket be a "cold-soldered"? The owner switches the amp on and off, on and off, so the toob will for sure expand and decrease the size depending on a temperature damaging a solder, so cathode followers will for sure some day generate a sharp peak damaging the amp. It was designed from the beginning. It is the bug, it is the mistake, it is what I was saying about.

Do you understand me now?

If not, I will continue...

Leg 2 is a filament, leg 3 is anode (speaking American it is a Plate).
A voltage between them is high.
If a phase splitter has a loose contact it generates enough voltage peak to cause a spark between legs 2 and 3 of an output tube (no matter which nation manufactured them),

...if you don't answer I can continue my educational session later.
Old 25th August 2007
  #17
Lives for gear
 

Quote:
Originally Posted by Wavebourn View Post
Do you understand me now?

If not, I will continue...

...if you don't answer I can continue my educational session later.

yes i understand you... and perhaps better than you think... you see nothing you offered will help the OP's problem.... back under the bridge troll...
Old 26th August 2007
  #18
Lives for gear
 
ulysses's Avatar
You can bet the SVT Classic is NOT identical in build and layout to the original SVT, so the "weak points" are most probably different. Whether the Asian-manufactured SVT Classic is a redesign from the US-manufactured SVT Classic is another good question. On top of that, are there component differences between them? This is what the OP needs to know, and I'd like to see his question answered. Unfortunately, I don't think this is the place to find out.
If you ask Ampeg, I guarantee they'll say "Oh yeah, it's the same amp." But they'll say that about the SVT Classic vs. the original SVT as well, and we know that isn't going to be strictly true. Your best bet is to bring your US-built SVT Classic into the store and talk them into letting you open up both amps and look at them. Promise not to touch anything, you just want to see if they look the same. As in, was the circuitboard redesigned? Have parts moved around? You may discover some capacitors are a different color (different brand) or the transformers have a different finish on them, which may or may not be meaningful. Those kinds of differences could exist between US specimens as well.
In the end, I think you may decide you should take the Asian-built unit. After all, you don't want it to be EXACTLY the same as the US-built unit. For example, you don't want it to blow that tube repeatedly. Try it out and see if it sounds as good as the other one, that's what matters. Just as long as the warranty is still valid.
Old 26th August 2007
  #19
Lives for gear
Quote:
Originally Posted by ulysses View Post
You can bet the SVT Classic is NOT identical in build and layout to the original SVT, so the "weak points" are most probably different. Whether the Asian-manufactured SVT Classic is a redesign from the US-manufactured SVT Classic is another good question. On top of that, are there component differences between them? This is what the OP needs to know, and I'd like to see his question answered. Unfortunately, I don't think this is the place to find out.
If you ask Ampeg, I guarantee they'll say "Oh yeah, it's the same amp." But they'll say that about the SVT Classic vs. the original SVT as well, and we know that isn't going to be strictly true. Your best bet is to bring your US-built SVT Classic into the store and talk them into letting you open up both amps and look at them. Promise not to touch anything, you just want to see if they look the same. As in, was the circuitboard redesigned? Have parts moved around? You may discover some capacitors are a different color (different brand) or the transformers have a different finish on them, which may or may not be meaningful. Those kinds of differences could exist between US specimens as well.
In the end, I think you may decide you should take the Asian-built unit. After all, you don't want it to be EXACTLY the same as the US-built unit. For example, you don't want it to blow that tube repeatedly. Try it out and see if it sounds as good as the other one, that's what matters. Just as long as the warranty is still valid.
All very good points. A friend of mine that works at the store said an Ampeg rep came in to talk to all the employees to insure them that the only thing different about the unit is where it's built. I wanted to see if anyone here at GS, with some technical background, had openned one up or fixed one. But I will have the store's electrical guy open both up to see if they're the same...very good advice.
Old 30th August 2007
  #20
Lives for gear
 
Wavebourn's Avatar
 

Quote:
Originally Posted by JB872 View Post
A friend of mine that works at the store said an Ampeg rep came in to talk to all the employees to insure them that the only thing different about the unit is where it's built.
I would definitely believe your friend. My point was and is, outsourcing manufacturing they would rather copy all design mistakes than change anything. Production people are usually religiously stubborn against changing anything in famous models...
Old 31st August 2007
  #21
Anyone with a SVT should go to each gig with a multimeter to reset the output bias as it shifts around all the time. I had to do this many times in the past, a meter should be built into these things.

On another note, keep in mind this is not a bass amp, it's a guitar amp. It rolls off below 90 hz just like a guitar amp. This is a result of the preamp section using small coupling caps. Anyone can do the test to confirm how much low end you are losing. Use an external preamp with good low end and jack it into the power amp input jack. Now, there's that missing low end!

It's possible to modify the preamp for better low end, this requires replacing all the coupling caps with larger units. Then one needs to cut the B+ lines which share all the preamp stages with RC networks to decouple the B+ voltage. Ampeg went on the cheap here sharing all tube stages from a single power line which will cause motorboating if larger caps are installed without the RC networks.

Then there's that nasty sounding mid range inductor...

Jim Williams
Audio Upgrades
Old 31st August 2007
  #22
Lives for gear
 
Wavebourn's Avatar
 

Quote:
Originally Posted by Jim Williams View Post
Anyone with a SVT should go to each gig with a multimeter to reset the output bias as it shifts around all the time. I had to do this many times in the past, a meter should be built into these things.

On another note, keep in mind this is not a bass amp, it's a guitar amp. It rolls off below 90 hz just like a guitar amp. This is a result of the preamp section using small coupling caps. Anyone can do the test to confirm how much low end you are losing. Use an external preamp with good low end and jack it into the power amp input jack. Now, there's that missing low end!
Good point.

Quote:

It's possible to modify the preamp for better low end, this requires replacing all the coupling caps with larger units. Then one needs to cut the B+ lines which share all the preamp stages with RC networks to decouple the B+ voltage. Ampeg went on the cheap here sharing all tube stages from a single power line which will cause motorboating if larger caps are installed without the RC networks.

Then there's that nasty sounding mid range inductor...
Motorboating occurs in a first preamp stage when one pot is all the way down (or up? I don't remember), and one switch is on (I don't remember exactly, look at the schemo when a ground loop on HF occurs), I got rid of that adding couple of resistors and moving one ground wire.
The nasty hum can be eliminated without any RC networks in B+, just one more ground wire needs to be resoldered. Cheap mistakes, much cheaper than tube-and-transformer-killing phase splitter design, but nobody fixed them since the beginning...
Old 2nd September 2007
  #23
Gear Guru
 
FFTT's Avatar
 

Having played an original '73 SVT for many years, I can tell you with no reservation that
the SVT Classic sounds nothing like the original.

The output on the Classic was no where near as powerful at all my standard settings.

The SVT-VR is the closest thing, unless you buy an old original and have it refurbished.
Old 6th September 2007
  #24
Lives for gear
Quote:
Originally Posted by FFTT View Post
Having played an original '73 SVT for many years, I can tell you with no reservation that
the SVT Classic sounds nothing like the original.

The output on the Classic was no where near as powerful at all my standard settings.

The SVT-VR is the closest thing, unless you buy an old original and have it refurbished.
I got a call from the music store saying my new SVT CL had come in. So I pick it up, bring it home, take it out of the box, and what do you know... they gave me the new SVT-VR instead. I'll try it out and compare it to my old CL and see which I like better. I already like the idea of having a second channel on the VR for mixing in some dirt when needed.
Old 6th September 2007
  #25
Quote:
Originally Posted by dementedchord View Post
no i dont work for ampeg... unless you count @15yrs of doing warrantee repair at an independent facility... and while i think we would both agree that all design work is a compromise... i dont see what your generalizations about this particular piece accomplishes... this amp in various forms has been among the best bass amps ever produced.... where's yours?????
My design will be out next year. Maybe I'll have a prototype at Namm. It's going to be a Basson Sound product, 1000 watts, class AB solid state outputs. The preamp has a 4 band sweep EQ with shelving hi band, the low EQ has a bell/shelf switch. The comp is a dbx based design with gain, threshold, ratio. The tube stage is a 12AX7A design with adjustable drive and recovery controls. The loop is a balanced ground compensated design that avoids ground loops and can adjust to any level of send and return. It has balanced, unbalanced and DI outputs. All switching is via sealed relays and all are foot switch selectable. The input preamp is a hybrid design with a very fast low noise rf jfet in the corrective loop of a very high speed, high current opamp. It has an active/passive gain select and a high 2 meg ohm input impedance. The noise of this stage is -115 dbu.

Bandwidth is -1 db at 200k hz, -3 db at 2 hz to avoid phase shift in the audio band. THD is below .001% in the preamp stage if the tube and compressor are switched out. This will be a concert head with enough power to fry Ampeg 8x10 cabs, it's a great match for the Basson Sound 2000 watt 8x10 cabs.

Jim Williams
Audio Upgrades
Old 6th September 2007
  #26
Lives for gear
 

wayyyyyyyyyy kewl dude
Top Mentioned Products
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Similar Threads
Thread
Thread Starter / Forum
Replies
perx / So much gear, so little time
13
Jim Kerr / So many guitars, so little time
2
Jim Kerr / So much gear, so little time
0
Bassoon / So much gear, so little time
1
Soundscape / So much gear, so little time
11

Forum Jump
Forum Jump