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Best Opamps to replace TL072's in TAC Scorpion-II
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#61
19th October 2011
Old 19th October 2011
  #61
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Quote:
Originally Posted by Samuelito View Post
- Crackling pots and faders. WTF?!!?! Didn't happen before...
So ... when it had the electrolytic capacitors in it, it worked OK... and now they are not there it crackles....

What a surprise...

Colin
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#62
19th October 2011
Old 19th October 2011
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Hi Jensenmann
I did not bother to look at the pictures since my answer did not rely on this information.
To others in general:
Capacitors are an important part of most if not all electronic gear and the choice of value and type has to be made with respect to function and to some extent cost.
Equipment designed for satelites for example can't use caps that will reed replacing every 5 years so the cost of alternatives is astronomical.
The mantra that you 'must not' use capacitors for audio is both false and stupid and in almost all cases, not possible.
Replacing some caps by using 'servo' technology is possible to an extent but you are replacing a component that does it's job reliably and cheaply with a handful of costly parts, also needing capacitors to make them function properly!
Remember that 'power rail' capacitors are as much 'in the audio circuit' as the more obvious ones between stages unless the whole unit is totally balanced and they are still important even then.
As stated, the caps are there for a purpose and unless you are clever enough to redesign or allow for their removal, they should be left 'as is'.
Matt S
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#63
19th October 2011
Old 19th October 2011
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The idea of replacing the fader amp and removing the el caps came from a suggestion that Jim Williams did in this thread.


Quote:
Originally Posted by Jim Williams View Post
I believe AML has sub boards for replacing the SSM2015 chip. In recent years new devices have been released that would be a fine addition to the Scorpion.

In the stereo sum stage of the 4000 module I use the National LME49720NA. That is a very low noise opamp with huge open loop gain at 10k hz. That will clean up a stereo mix quite well. Coupling caps can be yanked out, those are precision devices.

In the S1000/1001 inputs, the new BurrBrown OPA1642 fet opamp is a winner in the EQ section, very low bias current (no pot scratch) and very low 5 nv noise. Use LME49720 for the fader amp and remove all the el caps there.

And the preamp has no longer the SSM2015 as I replace it with the AML preamp upgrade which has 2 opamps, one is a TL072 and the other one can't rememeber now.

Audio Maintenance Limited Electronic Products


And basically I'm trying to share my experience for those coming after not to make the same mistakes I did.
It's a challenging task as I said before but still doable if u have certain soldering skills.
It only takes 10 min to put back all the el caps, remove the bypass caps and change again the opamp.

Quote:
Originally Posted by Matt Syson View Post
Hi Jensenmann
I did not bother to look at the pictures since my answer did not rely on this information.
To others in general:
Capacitors are an important part of most if not all electronic gear and the choice of value and type has to be made with respect to function and to some extent cost.
Equipment designed for satelites for example can't use caps that will reed replacing every 5 years so the cost of alternatives is astronomical.
The mantra that you 'must not' use capacitors for audio is both false and stupid and in almost all cases, not possible.
Replacing some caps by using 'servo' technology is possible to an extent but you are replacing a component that does it's job reliably and cheaply with a handful of costly parts, also needing capacitors to make them function properly!
Remember that 'power rail' capacitors are as much 'in the audio circuit' as the more obvious ones between stages unless the whole unit is totally balanced and they are still important even then.
As stated, the caps are there for a purpose and unless you are clever enough to redesign or allow for their removal, they should be left 'as is'.
Matt S
I understand perfectly. Thanks for the data.
I left on one of the strips all the el caps with the bypass caps aswell and the new fader amp on a previous testing and the sound changed dramatically. Was not as clear as with all the caps out and I still had all these crackling and unstability.
Heard somewhere that new componenets take a time to stabalize on a system before working properly.
Is this true?

Thanks again for all the help and aswers!!!
Cheers,

Sam
#64
19th October 2011
Old 19th October 2011
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Quote:
Originally Posted by slenderchap View Post
So ... when it had the electrolytic capacitors in it, it worked OK... and now they are not there it crackles....

What a surprise...

Colin
Audio Maintenance Limited

Hi Colin,

I never tested the new preamp with the original settings before modding, but I'm sure it did not crackle.
Maybe you can help me with the overload part. The 2.2uf cap in that section is the one preventing the strip from overloading with voltage?

Thanks for your help again!!!
Cheers,

Sam
#65
19th October 2011
Old 19th October 2011
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Hi
You have to remember that Jim is a 'terrorist' and although I am not doubting that the mods he makes by using different chips works he is NOT providing a 'do this and it will work properly' instruction to cover all applications of a particular mod. He could, on a specific chip on a module he has worked on state what the benefits would be. He can also 'speculate' that on other units he has not worked on that a given mod will PROBABLY work but unless he has actually done it and proven either by complicated mathematical models or actually trying it can he say that it WILL work.
Would you fit alternative size tyres on your car and perhaps put diesel into a petrol engine?
No, the 2.2uF cap does not affect the overloading, go back and work out what it might do, then work out what functions the other capacitors are actually doing THEN decide whether they should stay in, come out or have a value changed AND REASON WHY? It is called learning, not copying.
Electrolytic capacitors do take a short time to 'form' in the circuit they are fitted into as the chemicals in the electrolyte stabilise. Typically the 'leakage' current will be higher than it should be for a short while. This effect may take several hours from 'brand new out of the box' but with frequent use (daily) the time taken will be a matter of minutes.
Matt S
#66
19th October 2011
Old 19th October 2011
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Quote:
Originally Posted by Matt Syson View Post
Would you fit alternative size tyres on your car and perhaps put diesel into a petrol engine?
LOL !!!!! Did the tyres change ones...

Thank you for the encouraging words. I really appreciate!!!

Indeed, learning it is. I've already learned a lot doing this mod and I hope I can learn some more. As I always say, knowledge doesn't take out space in the brain...
Still, there're a lot of things I do not understand how they work. I could never design a circuit. It's more a trail/error thing that I'm capable of right now.

One more. Jim Williams has a S1000/1001 mod listed in his website so I believe he knows what he is talking about.

Thanks again!!!!

Sam
#67
19th October 2011
Old 19th October 2011
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Hi
Ah but, he doesn't necessarily tell you ALL that you need to do (or bits you shouldn't), it is not a hand held, 'here's the parts list and some pictures' experience.
OTOH AML's instructions for fitting their sub boards is far more instructive, just needs an 'attractive assistant' though!
Matt S
#68
19th October 2011
Old 19th October 2011
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I changed my 32" tires on my Jeep Wrangler Unlimited to 35". That helps a lot if you are into rock climbing and off-roading as I do when not working.

I've been called a lot of things over the years, but terrorist is a new one for me. That word is not thrown about lightly in this country, it could lead to a visit by the authorities. We don't joke about that stuff here for good reason.

My posts are guidlines intended for knowledgable and capable souls willing to do their own work. It is not intended as a step by step paint by numbers solution. As they say in Amekville, "if in doubt, ask".

Yes, precision opamps allow direct coupling in many cases. It is done on a stage by stage basis. The fact that only 2 capacitors are left in my console proves the fact daily. Much of my analog outboard is also direct coupled, EQ's, compressors, power amps, etc. People all over the world are using this stuff every day. It works if it's done properly. If not, expect a world of pain.
#69
19th October 2011
Old 19th October 2011
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Hi
Perhaps I should have said 'extremist', in the sense that things are taken to an extreme.
I presume the 'authorities' you refer to are the ones keen on meddling in OTHER countries where they don't actually have any 'authority' as they are not elected or eligible for election at all. Big boots and bigger guns.
Have you done a full 'risk assesment' of the effect of fitting non standard tyres, which can invalidate insurance claims?
Matt S
#70
19th October 2011
Old 19th October 2011
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Quote:
Originally Posted by Matt Syson View Post
Hi
Perhaps I should have said 'extremist', in the sense that things are taken to an extreme.
I presume the 'authorities' you refer to are the ones keen on meddling in OTHER countries where they don't actually have any 'authority' as they are not elected or eligible for election at all. Big boots and bigger guns.
Have you done a full 'risk assesment' of the effect of fitting non standard tyres, which can invalidate insurance claims?
Matt S
What the hell is this?

I thought this was a console modification thread?

FWIW No, I am not a right wing republican either.

Gotta draw the line somewhere however, and that statement was crappy my friend.

Those big boots seemed to help in 1942 well enough no?

Stick to consoles and gear, politics ain't your forte.

Please, remember where you come from.

Good day,
john

PS: I thought political discussion was prohibited here?

Last edited by NEWTON IN ORBIT; 19th October 2011 at 05:59 PM.. Reason: Took J R's advice...a little.
#71
19th October 2011
Old 19th October 2011
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Inappropriate choices of words like this is why we have EDIT buttons.

Discussions of audio should be more fact based than trading opinions about world politics where the facts are not widely available, and discussion os often fueled by biased selective reportage.

I don't mind chewing on politics, just not here, not now. lets stick to things that can (almost) be proved.

JR
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#72
19th October 2011
Old 19th October 2011
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Quote:
Originally Posted by JohnRoberts View Post
Inappropriate choices of words like this is why we have EDIT buttons.

Discussions of audio should be more fact based than trading opinions about world politics where the facts are not widely available, and discussion os often fueled by biased selective reportage.

I don't mind chewing on politics, just not here, not now. lets stick to things that can (almost) be proved.

JR
Thank you!

John
#73
19th October 2011
Old 19th October 2011
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I have a s4000 master module on the bench now. It has 2 caps left, blocking tiny amounts of DC to the CR monitors. The master mix, fader amps, returns and studio outputs are sans electrolytic capacitors. The 2 mix/fader opamps are Analog Devices ADA4898-2, one hell of an opamp (look it up and be impressed).

Analog Devices | Semiconductors and Signal Processing ICs

Changes were made to lower the fader amp gain to unity so the master fader is now set all the way up for "0". The 47k resistor from the non-inverting input of the playback opamp was shorted, that lowered the source noise and DC offsets are still below 1 mv. Bandwidth was raised several octaves on the opamps as they roll-ed off too early for 192k recording.

BTW, the Jeep dealer also installs lift kits and larger tires/rims on new for sale Wranglers.

As we say, "It's a Jeep thing, you wouldn't understand"...
#74
19th October 2011
Old 19th October 2011
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Hi Jim
I understand where you are coming from with the mods but others don't necessarily keep up and your reference to 'only 2 caps' might suggest you pull all the others out.
My original reference was that you tell part of a 'story' and run away.
I had a go in a CJ5 ? Jeep in Canyonlands about 15 years ago. While it was fun it somehow lacked something.
Matt s
#75
19th October 2011
Old 19th October 2011
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If I explained every little detail I'd never get to work. As I mentioned, the info is for those that can understand it and don't need the paint by numbers step by step instructions. If I were not qualified, I would not attempt to rebuild my Jeep engine even if I see guys on TV doing it.

Guys like you and John get this stuff, if you don't, expecting to is delusional without study or help.

For those folks, "don't try this at home". Guess I need a disclamer like those "Jack Ass" guys have. That's the world we live in today, you got to cover the morons in this world so they don't go out and fulfill Darwin's theory.
#76
19th October 2011
Old 19th October 2011
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I was thinking of replying tomorrow with an audio sample and a 3rd test with fresh ears but I see a lot has been happening here.

2nd test:

Put back the 2.2uf on two of the modules. Run them as OH preamps with two Rode NT-5. Liked them much better before. Crackling still there.

Compared them with two strips with the current mod just to A/B them.

No crackling, no distortion?????? Pushed them to +10db. Nothing. I could even see the meter in PT like compressing the signal. WTF!!!!

Quickly patched BD - SD - R Tom - FL Tom to random modules. PADs off having good level in PT and the board fader at 0db. Gain at 1/3 of the way No distortion. Pushed BD and SD faders to +10db and +5db and nothing.

Back to the test modules.... No..... Crackling again. Let them run for a while and one of the modules became clean. No crackling, nothing. Still not the same sound as with the current mod.


3rd test up tomorrow. I expect it to be better than the 2nd one.
I would like to thank Mr. Jim Williams in advance for the tips. There were clear and straight foward to me.

Cheers,

Sam
#77
19th October 2011
Old 19th October 2011
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Quote:
Originally Posted by Matt Syson View Post
I had a go in a CJ5 ? Jeep in Canyonlands about 15 years ago. While it was fun it somehow lacked something.
Matt s
I recall driving a M151A1 1/4 ton utility vehicle, in an old day job I was drafted into back in 1970. It was 4WD and better off road than on (no rear sway bar so they had a bad tendency to roll over on pavement)... Mine was lacking most of the creature comforts in the modern consumer Jeeps, but mine had a cool 2 way radio with a big whip antenna.

Fun? No, not much. Maybe it needed bigger wheels.

JR
#78
19th October 2011
Old 19th October 2011
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IMHO....We all start by putting things into pieces without exactly nowing what are we doing... ???

You can call me a terrorist. When I was 4 (I thnk) I used to build bombs with batteries. It's impressive how the blow when u really heat them up....

By the age of 7 I was putting into pieces my first remote control car.
Ones spent 15 hours repairing sectors of an HD that was under the rain for months with windows 95 (98??) in DOS mode. From 30gb I think I got 3gb running.
That's how I started with computers and although I make half of my living from that now I still keep learning everyday.

I'm into gear now. Probably when I finish this board I'll go with something else. I'll keep reading and every time I'll learn something new. This is not intend to make a living out of it, but for LEARNIING!!!!!

Anyway, this was all at my cost. I knew what I was putting into risk as I was mostly starting from 0 knowledge. No disclaimer needed.

As for fulfilling Darwin's theory, the world doesn't need morons... We are going there all by ourselves.

Thanks again to everyone!!

Cheers,


Sam
#79
20th October 2011
Old 20th October 2011
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Quote:
Originally Posted by JohnRoberts View Post
I recall driving a M151A1 1/4 ton utility vehicle, in an old day job I was drafted into back in 1970. It was 4WD and better off road than on (no rear sway bar so they had a bad tendency to roll over on pavement)... Mine was lacking most of the creature comforts in the modern consumer Jeeps, but mine had a cool 2 way radio with a big whip antenna.

Fun? No, not much. Maybe it needed bigger wheels.

JR
Yes and more. I'm on my 3rd Jeep. Older models swayed and you felt like you rode a stagecoach for 10 hours. Not fun.

The JK model is larger and wider. Mine is 4 doors with the longer wheelbase. The anti-sway design is great now, and you can disconnect it for maximum articulation of the front axil. 35" tires add a bit more cushy-ness to bumps in the road. Creature comforts abound. I have adjustable gas shocks, G2 gears, Banks Power high intake system and other goodies. The 300 watt stereo has navigation, plays DVD's, uses a 8" subwoofer in the back and has a stereo line input to plug in stuff, even guitars and bass for car jammin'.

The ride quality rivals my old 2002 Ford Explorer. Crank up that stereo, crank up the air conditioner and it's like your not really off-roading, but floating over the earth. Once there, throw an air mattress in the back and snooze until all the stars come out. It's an amazing world out there.

As to crackling, it may be time to buy a cheap scope. You won't know what or where that problem comes from without more insight. It could be on the power supply, usually a defecting bypass cap. Could be an ittermittant pcb trace you broke but can't see. Clean the pcb with flux remover, be super careful not to splash any on the polystyrene caps in the EQ. Any silicon can generate noises if damaged. Pull out all the opamps and replace them with fresh ones (hope you put in sockets). If there are peak lite transistors float the power to them to remove them from the stew.
#80
20th October 2011
Old 20th October 2011
  #80
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Thank you!

I got a weller station with a sucker solder removal tool and a lamp with a scope, so the work was pretty clean.....on the table. My wife wasn't so happy founding all those black cylinders all over the floor.
Good cleaning is always a good start.

I'll clean them up and do some more tests tomorrow.

Cheers,


Sam
#81
20th October 2011
Old 20th October 2011
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5.333V is offline
just a thought...


why the hell is talking politics in the forum a big no no

while talking CARS is totally ok?


hate when people compare audio products with car modells.


when is it going to stop
#82
20th October 2011
Old 20th October 2011
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There are actually parallels between consumers modifying cars, and modifying audio products. The parallel is so obvious, they call it "hot rodding" audio gear.

With cars, unlike politics the facts can actually be determined, so every disagreement doesn't degenerate into ad hominum name calling and abusive comments.

Cars are not on topic, but a more pleasant diversion than where we were headed.

JR

PS: Jeeps aren't cars, or at least they weren't very car like back in the day.
#83
20th October 2011
Old 20th October 2011
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Technically the Jeep is a truck. They are also used in the EU military in place of Humvee's. The Border Patrol also uses them. Once after I got mine I was in the Borego Desert and stopped at the Border Patrol checkpoint on county road S2. All the guys poored over my new Jeep as they had the smaller, older TJ models. I showed them all the features and space in back. They really liked it and said they could patrol and pick up a couple illegals too. Now they all have them.

There is also a bumper sticker on the back that shows a glorious picture of our exalted leader. It reads: "Does this ass make my truck look big?"
#84
20th October 2011
Old 20th October 2011
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i give up..!
#85
20th October 2011
Old 20th October 2011
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Quote:
Originally Posted by 5.333V View Post
hate when people compare audio products with car modells.
"What the best mod for my '75 Pinto Hatchback to get sub-10 second quarter miles?

I read that I can mod the motor with twin-turbos and nitrous injection and tried that, but I was still in the 20's. Plus, the extra weight made the tires rub on the wheel wells. Then I took it to this guy who does mods for all my friends and he said that what I really need was to add a supercharger to the mix, and all would be right.

In my first run, I was doing great, I knew I could make it now! Then there was this knocking sound.

They found one of the pistons over 500 yards away.

I tried another guy who also does mods and he said "What did you expect? It's a '75 Pinto Hatchback. You're lucky to be alive. And you ruined a perfectly good car with all that nonsense."

Hope this helps!


DC
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#86
21st October 2011
Old 21st October 2011
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Quote:
Originally Posted by dcollins View Post
"What the best mod for my '75 Pinto Hatchback to get sub-10 second quarter miles?

I read that I can mod the motor with twin-turbos and nitrous injection and tried that, but I was still in the 20's. Plus, the extra weight made the tires rub on the wheel wells. Then I took it to this guy who does mods for all my friends and he said that what I really need was to add a supercharger to the mix, and all would be right.

In my first run, I was doing great, I knew I could make it now! Then there was this knocking sound.

They found one of the pistons over 500 yards away.

I tried another guy who also does mods and he said "What did you expect? It's a '75 Pinto Hatchback. You're lucky to be alive. And you ruined a perfectly good car with all that nonsense."

Hope this helps!


DC
Frank Zappa owned a Pinto hatchback. Frank didn't drive so Gail would run him down to the office on Ventura Blvd. Seeing Frank in a Pinto was disturbing.

Next time you see a guy in LA crossing all the curbs and using the sidewalks, it's just me in my Jeep. It's a great traffic avoider as sidewalks are extra lanes.

Meanwhile, try some of those BB OPA1612/1644 fet opamps in the Scorpion.
#87
21st October 2011
Old 21st October 2011
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MOdding cars is very like modding audio gear.


Fix the thing to work properly before you start modding.

And Change one thing at a time.

peace.
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Quick mention, please no ssl humping snoot telling me this and that about mp3s, this ain't the emo forum.
#88
21st October 2011
Old 21st October 2011
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Or u can just tear it apart, put new engine, new gearbox, new differential and extras and make a monster out of it.




Scorpion is working good. Only 4 modules are a bit unstable. Ordered the flux remover and I'll start from there. For the time being I just moved them to the back of the starting grid.

Cheers
#89
30th October 2011
Old 30th October 2011
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Quote:
Originally Posted by manzini View Post
sorry for the offtopic.



Hello John
Basically because I don't understand some issues and somethings on the circuit and satisfy my curiosity and learn:

Yes, that I thought.
This is not in the signal path and apparently should not affect, however I did this test and I was surprised by my curiosity:

With a 180ohm resistor and near cranck maximum gain (position 75db, output at 4pm).

With the LME49990, I have not been exhaustive testing because I'm more than a month with all my gear apart and began with acoustic treatment in my bedroom-studio.

I do not have the full test with pictures but in a quick test, observed (listening) noise spikes, but with the same noise floor than opa2134. LME49990 it seemed bit clearer, flat, but showed a strong 20dB peek distortion near 100Hz. I could not put the opamp bypass to ground before dismantle all my gear.

Only a bit: I have a ground Issue on the PSU board to solve (you can see at 50Hz with harmonics).

I explain the pictures:

Pre73 MKI (not new unit) Stock. TL072



Pre73 mk-I Stock (TL072) after little changes on PSU board ground. Not complety solved.



Pre73 MK-I with 2sc3329BL and TL072



Pre73 MK1 with 2sc3329 and OPA2134



Now I am searching the picture with the LME49990 (same noise level, but little better, flat noise but with a 20dB peak at 100Hz).

Opamp not in the signal path ? I don't know, but with some effect on performance. 5dB - 7dB less noise floor.

In the coming weeks, when I have finished the acoustic treatment, I will continue investigating this issue (LME49990 and Opamp effect in pre73) and learn to solve the remaining HUM.

I think that -120dBs are the noise inherit for pre components and card, cables, etc. I received the scope but is still in the box.

Kind regards.
It's strange that the OP amp for the meter change the noise that much. I guess that the noise is feed trough the PSU. The upcomming DLX version should have separated internal stabilizers for signal and meter. Can it be that they target the same problem with that? 5-7 dB in the signal path pretty huge tough.
#90
4th December 2011
Old 4th December 2011
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Hi
I presume you have also refurbished the master / monitor sections?
Electrolytics should be used witjh typically 70 Percent of their maximum DC rating although it is not a hard and fast rule. You must never run them above their maximum DC rating however. Most in this desk will have next to no DC across them.
Balancing could be an expensive or tedious excercise but you can gety excellent results if you are careful with the physical routing and grounding of insertable gear.
One possible 'solution' could be to have a few 1:1 transformers available on the patch or 'nearby' that you can use if a particular piece of gear gives you grief.
Matt S
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