I am not sure if this is the right place to ask for this kind of advice.
I am currently running and managing a recording studio, which I have built myself. The studio is based around a Soundcraft 800B mixing desk which is the live counterpart to a Soundcraft 1600. The difference between the two mixers is only the configuration of the modules and the fact that the 1600 has an optional patchbay. Other than that, the input stages and channel strips are the same.
I do like the sound of the desk, and I am in no doubt that it's a high quality piece of equipment, but I do feel there is room for improvement. I do feel that the preamps on the console could use a bit tweaking. They do sound OK, but I suspect that there are some improvements that can be done to give them more life and maybe less noise. I know this is not a clean sounding console, neither is the purpose of the studio, since I mostly record the typical blues, rock and occasional metal bands. I have attached the schematich for the front end of the input modules. As you can see, the very front end is discrete, followed by a couple of opamp stages. The transistors are 2N4403 and the opamps are TL072.
I am willing to do major modifications, but I would like to ask you NOT to advice me to either scrap the console or buy outboard preamps. Outboard pre's are not that practical, both because of the price of a nice pre will be above the 1000$ mark, and 32 channels of nice pre's are not really anything I can afford... Ever...
Give me your suggestions for improvements. Maybe I could benefit from changing the resistors from carbon to metal film, other transistors, constant current source in the emitters of the first stage. Gimme all you've got!
The complete schematics are here: http://www.soundcraft.com/downloads/fetchfile.aspx?cat_id=user_guides&id=1282
I am currently running and managing a recording studio, which I have built myself. The studio is based around a Soundcraft 800B mixing desk which is the live counterpart to a Soundcraft 1600. The difference between the two mixers is only the configuration of the modules and the fact that the 1600 has an optional patchbay. Other than that, the input stages and channel strips are the same.
I do like the sound of the desk, and I am in no doubt that it's a high quality piece of equipment, but I do feel there is room for improvement. I do feel that the preamps on the console could use a bit tweaking. They do sound OK, but I suspect that there are some improvements that can be done to give them more life and maybe less noise. I know this is not a clean sounding console, neither is the purpose of the studio, since I mostly record the typical blues, rock and occasional metal bands. I have attached the schematich for the front end of the input modules. As you can see, the very front end is discrete, followed by a couple of opamp stages. The transistors are 2N4403 and the opamps are TL072.
I am willing to do major modifications, but I would like to ask you NOT to advice me to either scrap the console or buy outboard preamps. Outboard pre's are not that practical, both because of the price of a nice pre will be above the 1000$ mark, and 32 channels of nice pre's are not really anything I can afford... Ever...
Give me your suggestions for improvements. Maybe I could benefit from changing the resistors from carbon to metal film, other transistors, constant current source in the emitters of the first stage. Gimme all you've got!
The complete schematics are here: http://www.soundcraft.com/downloads/fetchfile.aspx?cat_id=user_guides&id=1282
The easiest thing would be to contact Jim Williams of Audioupgrades as he specialises in just this kind of thing.
Audio Upgrades
Personally I would get rid of the TL072s as a first step.
I replaced the ones which were in my active xovers with OPA2134s and got a significant improvement. Other and better opamps are available but would possibly need extra bypass caps to prevent them oscillating.
Talking about capacitors it might be about time to have your Soundcraft recapped.
That's all I've got, I'm crap at electronics.
Audio Upgrades
Personally I would get rid of the TL072s as a first step.
I replaced the ones which were in my active xovers with OPA2134s and got a significant improvement. Other and better opamps are available but would possibly need extra bypass caps to prevent them oscillating.
Talking about capacitors it might be about time to have your Soundcraft recapped.
That's all I've got, I'm crap at electronics.
Hi,
2N4403's are low noise, the TL072's not so much, I'd replace them
with 5532's as a matter of course, but try one or two channels first.
Quite probably changing IC1 only will make the biggest difference.
Years ago for a friend I installed quality transformers into half of his mic
channels of his desk. Not cheap but it worked noise wise, very well.
I only changed half (8 of 16) because they were mic / line level switchable.
Seem to recall though they they had no pre analogue front end to
the IC's, which could explain why the transformers worked so well.
rgds, sreten.
Changing IC1 to 5532 is the cheap obvious no brainer,
and must be done first before anything else, IMHO.
2N4403's are low noise, the TL072's not so much, I'd replace them
with 5532's as a matter of course, but try one or two channels first.
Quite probably changing IC1 only will make the biggest difference.
Years ago for a friend I installed quality transformers into half of his mic
channels of his desk. Not cheap but it worked noise wise, very well.
I only changed half (8 of 16) because they were mic / line level switchable.
Seem to recall though they they had no pre analogue front end to
the IC's, which could explain why the transformers worked so well.
rgds, sreten.
Changing IC1 to 5532 is the cheap obvious no brainer,
and must be done first before anything else, IMHO.
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PS: I would strongly advise you to hang on to that console.
They are very much overlooked gems and very tweakable, built like the proverbial tank and fully modular. A replacement in todays money would cost many thousands if you can actually find that build quality nowadays. To get an idea of the cost I think the closest you'd get would be an Audient console which is only semi-modular.
A Jim Williams tweaked Soundcraft would be better/cleaner than an SSL (that man really does know his business).
Personally I'd tweak some channels myself with OPA2134s or 5532 as sreten suggested, some by Jim and possibly leave some alone. That way you'd have a choice of flavours to cover nearly all eventualities. Jim's mods would get noise down to about -132dB or so and I'd seriously consider having the master module done by him. At $275 it is a bargain.
They are very much overlooked gems and very tweakable, built like the proverbial tank and fully modular. A replacement in todays money would cost many thousands if you can actually find that build quality nowadays. To get an idea of the cost I think the closest you'd get would be an Audient console which is only semi-modular.
A Jim Williams tweaked Soundcraft would be better/cleaner than an SSL (that man really does know his business).
Personally I'd tweak some channels myself with OPA2134s or 5532 as sreten suggested, some by Jim and possibly leave some alone. That way you'd have a choice of flavours to cover nearly all eventualities. Jim's mods would get noise down to about -132dB or so and I'd seriously consider having the master module done by him. At $275 it is a bargain.
Thank you for the suggestions. I will be ordering some OPA2134's. I do already have a couple of hundred 5532's and I do have other different dual-opamps and I have some tubes of IC-sockets too, so there is room for experimenting.
Well I guess there is no reason to change the transistors in the front end then, if they are already a low noise type. Could there be any design changes done there? What about adding a transformer on a couple of channels?
Yes I could send a module to Jim Williams, but if I could do the work myself, I could save some money.
Well I guess there is no reason to change the transistors in the front end then, if they are already a low noise type. Could there be any design changes done there? What about adding a transformer on a couple of channels?
Yes I could send a module to Jim Williams, but if I could do the work myself, I could save some money.
On another forum Jim was very generous with giving out information on what he does to the modules but for some reason he has started to delete all his posts over the last two weeks. May be it cost him business, I don't know.
What I do remember is that he used Linear Technology opamps and favours Panasonic caps. His mods make the modules as transparent as is technologically possible which is why I suggested may be having the master module done by him.
What I do remember is that he used Linear Technology opamps and favours Panasonic caps. His mods make the modules as transparent as is technologically possible which is why I suggested may be having the master module done by him.
Jim uses very high speed opamps. One of my favorites he turned me on to is the LT1358/9. He also puts current sources on the outputs for class A operation. Biasing Op-Amps into Class A
I have found non-polarized capacitors at RS at the right values, in sized that could be mounted on the board.
At first I will try to do the upgrades on a few channels, so I can compare them to the stock channel strips.
I am well aware about the problems of changing opamps and the power consumption. I am fully capable of making a more powerful powersupply, at least for the +/- 17 Volt audio supply myself, out of components and materials from my work. Many of these standard components (Low-ESR caps, resistors and opamps) I can either get from my work, or order relatively easy. So cost is less of an issue.
Would there be any point in maybe having a couple of transformer coupled channels? Could that have any sonical benefits?
I also found this post at Gearslutz from Jim Williams about the Soundcraft 1600 (which is basically the same as 800B but with a patch bay):
And thank you for all your great advice. I am very happy about this desk, and since it is entirely built upon standard components, it will serve me well for many years. I fortunately have a couple of extra channel strips and a group strip lying around.
At first I will try to do the upgrades on a few channels, so I can compare them to the stock channel strips.
I am well aware about the problems of changing opamps and the power consumption. I am fully capable of making a more powerful powersupply, at least for the +/- 17 Volt audio supply myself, out of components and materials from my work. Many of these standard components (Low-ESR caps, resistors and opamps) I can either get from my work, or order relatively easy. So cost is less of an issue.
Would there be any point in maybe having a couple of transformer coupled channels? Could that have any sonical benefits?
I also found this post at Gearslutz from Jim Williams about the Soundcraft 1600 (which is basically the same as 800B but with a patch bay):
And thank you for all your great advice. I am very happy about this desk, and since it is entirely built upon standard components, it will serve me well for many years. I fortunately have a couple of extra channel strips and a group strip lying around.
Off the top of my head, that preamp looks very much like the 400B I used for quite some years. Nevertheless, I don't think you will gain much in terms of noise by changing the opamps, as it is the two input transistors that sets the noise level. 5532s should be OK in terms of power consumption. I'm not really sure you'd get much lower noise by changing the transistors either, as 2n4403 is concidered being quite good in that respect, and getting any real improvement with other transistors may need a total redesign. Maybe shopping for some used external mic preamps is a better choice.
True, reducing noise for the micpre amp will be nearly impossible. But lower distortion and better bass - generally a more open sound can be obtained. Upgrade the power supply, then opamps and caps AND ADD A CURRENT SOURCE TO BIAS THE OPAMP FURTHER INTO CLASS A OPERATION. At least do this to the opamp associated with the mic pre circuit. A lm334 set to even ONE MILLIAMP (62ohm set resistor if memory serves me) will help with low level detail linearity. I learned this from Jim Williams.
Glad you still found a suitable Jim Williams post at gearslutz since he has been deleting a lot of his posts there as I previously mentioned.
I wasn't sure if its cool to mention other fora by name here, some moderators at some fora can get quite touchy about that kind of thing.
-129.6 EIN is not to be sniffed at if you can get that or close to it.
Output transformers should give you a different flavour sound which is/can be a good thing. Output transformers can have more influence on the sound than valves do. In my experience solid state mics with output transformers sound more like vintage valve mics than modern transformerless valve mics.
Enjoy your console and the fiddling with it.
May all your recordings be hits!
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