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Modding a mixer to sound more vintage???
Old 26th March 2014
  #1
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dysenterygary's Avatar
 

Modding a mixer to sound more vintage???

I have been blessed with an abundance of Soundcraft Delta 200 strips and I've modded several of them with help from people on here. Most of the mods, however, make the strips sound much more modern, and clean. Is it possible to go the other direction, and make some strips sound more vintagey?

Since the channels are fairly simple anyway, I'm guessing the only way to do it would be to put dirtier/noisier transistors on the mic input, and maybe more primitive opamps? Is there anything more primitive than TL072's?
Old 26th March 2014
  #2
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Karloff70's Avatar
 

Maybe put some dirty ol trannies in there. Transformers, that is.

Or just sell it and get a vintagey sounding desk. Putting trannies on all the ins and main outs would get pretty bloody expensive.
Old 26th March 2014
  #3
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Hi
Load the outputs of some of the TL072 throughout the channel with say 1K8 resistors, maybe a touch lower resistance.
Increase the feedback capacitors to lower the HF response. Decrease some of the electrolytic capacitor values to lower LF rsponse and increase distortion.
Try input transistors with a lower Hfe and if you have a multimeter that can test Hfe, fit non matching pairs.
Transformers may help if cheap.
Matt S
Old 26th March 2014
  #4
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Ike Zimbel's Avatar
 

Hi,
You could try putting some slower op-amps in, like the 4558. I see there are several different versions with different specs. I would go for the lowest slew rate (1.2v/us) and see if it sounds like crud. +1 to Matt's suggestions, but all of those require soldering. As I recall, the feedback caps on that vintage of Soundcraft were already kind of conservative...like 100pf where others might have used, say, 22pf.
Best,
Ike
Old 26th March 2014
  #5
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JohnRoberts's Avatar
 

Just say no.....



If you lust for some vintage sound, buy a vintage console. With the popularity of digital, the old analog stuff is getting cheaper and cheaper.

I am not aware of what exactly makes a vintage console sound the way it does, they were generally trying to make them as clean and linear as they could.

JR
Old 27th March 2014
  #6
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increse c22,c23,and c24 to 100uf50V this will give it a darker sound like a studiomaster.

replacing metal film for carbon film resistors too, but watch out as in some places it will induce too much white noise.
Old 27th March 2014
  #7
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Record a vintage band in a vintage studio, using vintage mic techniques on vintage tape with a vintage engineer - at that point the console will be the least of your worries!
Old 27th March 2014
  #8
Gear Maniac
 

I wouldn't mess with the electronics if you have already done the work to make it better.

For a more "vintage sound" I would consider putting some steel core transformers on the outputs to start.

Mic input transformers are expensive because they need shielding and the circuit has to be ready to handle them. But line level 1:1 isolation transformers essentially will do the trick for line level signals like for summing/mixdown.

You can probably make a box to switch them in/out or just patch.

Edcor is probably the cheapest place to get steel core transformers. I know that Black Lion Audio is a fan. They definitely have more of a saturated low end like the classic transformers.

On the super cheap for line inputs, I considered getting ART 8-channel isolation boxes with transformers. They are cheap transformers but a review I read said it actually helped control the low end. I assume they are similar to their di box transformers and they sound fine to me. But that may be enough vintage saturation essentially you may be looking for.

When I modded a vintage Tascam console, my plan was to do this. But I moved to a smaller space and sold the console. Never got around to actually doing it.
Old 27th March 2014
  #9
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Hi
There is no such thing as 'just put a transformer in' as they are all different and they interact differently with the stage that 'drives' them, and to what follows which may depend on the variable 'cable length'.
Recapping 'like for like' is a process of getting the gear to sound close to how it did when it left the factory 10, 20, 30, 40 or more years ago and is not really making things 'modern' simply how they used to sound.
As JR observes the original aim of most companies was for clean and clear in their designs and added to the fact that it was nigh impossible to record frequencies above about 25KHz or below about 10Hz there was no need to try to do so and can cause problems if attempting it.
Matt S
Old 27th March 2014
  #10
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If Jim Williams still posted here he would be loosing his [email protected] mind right now...


But seriously folks....


I am not sure if modern transformers will mess up the sound enough to be worth the money. If you got some old UTC they would have the mojo you desire.

If I were you I would just buy an old tube preamp and be done with it.
Old 27th March 2014
  #11
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Hi
It is not necessarily the transformer. It is the drive circuit as well and many hours are spent by designers getting it 'right'. A 'Vintage UTC' will still not sound 'right' unless FED from the circuits used in the past. Gear using ICs for the output can add 'current limit distortion' when the transformer 'saturates' unless it is finely tuned not to do so.
Matt S
Old 27th March 2014
  #12
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Quote:
Originally Posted by Matt Syson View Post
Hi
It is not necessarily the transformer. It is the drive circuit as well and many hours are spent by designers getting it 'right'. A 'Vintage UTC' will still not sound 'right' unless FED from the circuits used in the past. Gear using ICs for the output can add 'current limit distortion' when the transformer 'saturates' unless it is finely tuned not to do so.
Matt S
Absolutely true, however when I suggested that I was thinking of a direct box I built from a very old utc ls transformer and whatever goes through it comes out with a very strong color (better sounding and more output than a radial). This requires no circuit at all. I was thinking along the lines of a 1:1 transformer on the outputs of his mixer (or perhaps a buss if he only wanted it at certain times).

Basically don't run out and buy a handful of modern transformers and expect sonic nirvana.
Old 27th March 2014
  #13

Carbon comp resistors

a little DC on the primary if you add a xfrmr

replace gyrators in the EQ with inductors

....



-tINY

Old 27th March 2014
  #14
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vince @ speck's Avatar
 

Quote:
Originally Posted by dysenterygary View Post
Is there anything more primitive than TL072's?
Of course... plenty of old monolithic IC opamps still available.... but not necessary as a drop-in replacement.

Get a 8 pin DIP adapter like this Single-to-dual Op-AMP Adapter - DIP version (p/n 021001) and try two LM741 IC's as a replacement for one TL072. In strategically placed locations in the audio circuit they will give you that ye-olde-vintage-sound.
Old 28th March 2014
  #15
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Karloff70's Avatar
 

Quote:
Originally Posted by vince @ speck View Post
Of course... plenty of old monolithic IC opamps still available.... but not necessary as a drop-in replacement.

Get a 8 pin DIP adapter like this Single-to-dual Op-AMP Adapter - DIP version (p/n 021001) and try two LM741 IC's as a replacement for one TL072. In strategically placed locations in the audio circuit they will give you that ye-olde-vintage-sound.
Out of interest, what other gear has these little old buggers in them (for a semi misguided tone reference type job...)?
Old 28th March 2014
  #16
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Ike Zimbel's Avatar
 

I'm working on an Eventide Instant Flanger...it's FULL of 741's.
iz
Old 28th March 2014
  #17
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Karloff70's Avatar
 

Quote:
Originally Posted by Ike Zimbel View Post
I'm working on an Eventide Instant Flanger...it's FULL of 741's.
iz
Cool, thanks. Any more anyone? Just curious here.....
Old 28th March 2014
  #18
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I am generally a "customer is always right" kind of guy but are you guys seriously suggesting that you replace a TL072 with 741s?

In the first place you wouldn't need to use an adapter because they made dual LM741s. They were called LM1458, but please do not swap out your decent TL072s for the much lower performance early mass market opamps.

The 741 was actually high tech for it's time, but that time passed 40+ years ago.

As some have suggested there may be some euphonious colorations to be found in old transformers, but even this is not as simple as dropping some in.

If you want to ride a horse, buy a horse, don't take the motor out of your car and hitch a horse to the front bumper. It is not the same.

Carry on...

JR
Old 28th March 2014
  #19
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Karloff70's Avatar
 

Quote:
Originally Posted by JohnRoberts View Post
I am generally a "customer is always right" kind of guy but are you guys seriously suggesting that you replace a TL072 with 741s?

In the first place you wouldn't need to use an adapter because they made dual LM741s. They were called LM1458, but please do not swap out your decent TL072s for the much lower performance early mass market opamps.

The 741 was actually high tech for it's time, but that time passed 40+ years ago.

As some have suggested there may be some euphonious colorations to be found in old transformers, but even this is not as simple as dropping some in.

If you want to ride a horse, buy a horse, don't take the motor out of your car and hitch a horse to the front bumper. It is not the same.

Carry on...

JR
Not about to stick a dog full of 741's and expect it to turn into a horse. Just curious in what they were used.
Old 28th March 2014
  #20
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Quote:
Originally Posted by Karloff70 View Post
Just curious in what they were used.
3M model 79
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Old 28th March 2014
  #21
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Quote:
Originally Posted by Karloff70 View Post
Not about to stick a dog full of 741's and expect it to turn into a horse. Just curious in what they were used.
The primary limitation of 741 level technology is speed/gain bandwidth (and noise, and...).

FWIW the speed limitation is mainly a problem for high level high frequency signals. Low frequency and/or low level signals will be handled unmolested. The slew rate for 741 technology opamps is around 0.5V/uSec so you can do the power bandwidth math yourself (hint, it's not 20kHz for +/-15v signal)..

Little appreciated, the much maligned -10dBV bedroom recording, semi-pro gear standard, was actually a reasonable nominal 0VU operating point (300 mV or so) especially in light of the popular opamp technology's limited power bandwidth.

IMO there is nothing remotely good sounding about slew rate limiting. While the lower gain bandwidth could result in a loss of HF in very high gain sockets.

The 741s were widely used at lower rail voltages and perhaps lower bandwidth applications where the slew rate was not an obvious audible limitation. If you inspect old schematics look at the PS rail voltage, and application. I would not expect to see many 741s in premium, wide band, +/-15V path applications (there were faster, albeit more expensive opamps even back then).

Since the '70s we've had economic opamp choices without the speed/gain bandwidth limitations.

JR

PS: Back in the '80s I did a comparison between -10dBV and +4dBm audio paths for general audio quality, for my magazine column and the -10dBV path did respectably well as long as noise floor was well managed. FWIW back then typical media dynamic range was much lower than today.
Old 28th March 2014
  #22
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mjrippe's Avatar
 

Quote:
Originally Posted by Karloff70 View Post
Cool, thanks. Any more anyone? Just curious here.....
Trident Fleximix consoles were shipped with 741 types.
Old 28th March 2014
  #23
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Karloff70's Avatar
 

Thanks guys!
Old 28th March 2014
  #24
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Hi
Worked on 2 Fleximixes recently and they both has TL071 and they are bad enough.
Matt S
Old 29th March 2014
  #25
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S2udio's Avatar
 

I Just don't get this............?
Strange audio behavior indeed ,
Are we going Backwards to go Forward ?
Lets Reinvent the wheel.
Spent many a day using the 741,
The implementation of a downgrade depends on "whats around" it...
Far more interesting things To Do !

The OP appears to have left the building..
Old 29th March 2014
  #26
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mjrippe's Avatar
 

Quote:
Originally Posted by Matt Syson View Post
Hi
Worked on 2 Fleximixes recently and they both has TL071 and they are bad enough.
Matt S
Matt,

I have a soft spot for Fleximix boards, as the first board I owned was one! It had original 1741 chips, as seen on the schematics. With a bit of love they can be quite decent, though not as nice as the bigger Tridents for sure.

Mike
Old 29th March 2014
  #27
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Karloff70's Avatar
 

Quote:
Originally Posted by S2udio View Post
I Just don't get this............?
Strange audio behavior indeed ,
Are we going Backwards to go Forward ?
Lets Reinvent the wheel.
Spent many a day using the 741,
The implementation of a downgrade depends on "whats around" it...
Far more interesting things To Do !

The OP appears to have left the building..
Didn't you know, grunge and filth is the new clarity.
Old 29th March 2014
  #28
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dysenterygary's Avatar
 

Quote:
Originally Posted by S2udio View Post

The OP appears to have left the building..
Nope, I've just been enjoying the thread. I'm definitely not going to drop any money on transformers, but I might try some of the 1458's and some carbon resistors.
Old 29th March 2014
  #29
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JohnRoberts's Avatar
 

Quote:
Originally Posted by dysenterygary View Post
Nope, I've just been enjoying the thread. I'm definitely not going to drop any money on transformers, but I might try some of the 1458's and some carbon resistors.
I was not suggesting that I thought slow-old opamps had an ounce of merit. Forget I mentioned them.

JR
Old 30th March 2014
  #30
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Geoff_T's Avatar
 

Quote:
Originally Posted by Karloff70 View Post
Out of interest, what other gear has these little old buggers in them (for a semi misguided tone reference type job...)?
Hi

HH TPA professional power amplifiers used by the BBC and scores of recording studios (see photo of an AIR Neve console on my pictures ppages) had a 741 as the input stage then driving the transistor output stages...

http://auroraaudio.net/wp-content/ga...-oxford-st.jpg
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