Soundcraft transamp conversion

[Chrome Heart]

Im interested to know if anyone has a diagram of the input transamp mod/conversion that Jim Williams does on the 200B fixed EQ module.
TIA

 

[Eliani]

I've been researching this for a while now. I've got two 8ch Soundcraft 200 consoles, one with sweepable eq, one without. I've just started making a small list of upgrades/mods which could get a little extra out of these consoles. I just can't seem to find my way around thousands of posts about everybody trying this and that, but nobody really has made an effort to clearly write down his findings. Except for the Eddie Ciletti star grounding concept, which I believe should be the first thing to do when modding a 200b.

Here's what I would like to find out/discover/research...

What does Jim Williams do to these consoles to make them perform so well?
I know the channels sound extremely clean when Jim modded them, but maybe that's what I'm after. Everybody recommends the Jim Williams master section mod, so I would really love to find out more about his findings, and if he's willing to share his information with us. I'm not an electronics genius, but still I would like to do this myself, because i like doing it.

I've read on multiple threads that removing/bridging all the capacitors (except the coupling caps) in the signal path of a channel really sounds great. But does it sound fatter, cleaner, better in what way?
On the downside of this modification would be the DC build-up, which would cause clicks and pops when using switches, can I reduce this with some kind of DC-Servo circuit? (I only know about this because I've been building That1510/1512 preamps, and they needed a DC-servo to cancel DC...)

I've experimented with a couple of Burr-brown opamps before (opa2134), but modded only one channel. I noticed a big difference, especially in output levels to the summing bus which makes it a cleaner console!! But I'm aware of the consumption of power over the TL072 opamps and I need to know if I can just switch opamps, are there any other mods I need to perform to have a channel accept other opamps, do I need to attenuate the signal to the summing bus, I do not want to drive it to hard...

I would like to make a small list with proven mods to the 200b, or 400B/800b if they apply.
This could be a list that could tell you if you need clean channels, or fat channels, or special sounding channels. With sound-files comparing them to the original, and to each other!!
Anybody helping out with this would be much respected, and of course end up in the credentials of my biographic memoires!!

Eli-Audio.com

 

[living sounds]

I've started a number of threads here and got very helpfull advice regarding modifications of the 200b. I ended up with significant changes, resulting in superior performance. Using the line ins there is no cap in the signal path (except the one in the DC servo), very little noise, distortion and the EQs sound great.

Modifications include the ground mod mentioned before, changing grounding to have a seperate signal ground and a power ground, changing the input circuit around the servo, upgrading many parts to higher quality, modifying the EQ range, upgrading the PSU, using better op amps in most places, adding PSU bypass caps.

It's been A LOT of work, and looks rather messy, but worth in in terms of sound, which is now very clear, transparent, balanced, punchy,.... uncoloured, but it sounds much better than what I could ever get ITB.

 

[JohnRoberts]

Im interested to know if anyone has a diagram of the input transamp mod/conversion that Jim Williams does on the 200B fixed EQ module.
TIA

I have seen a discussion of that mod, perhaps on geekslutz forum. As i recall it was reconfiguring the opamps and NF paths in the mic preamp so the preamp transistors are held constant current by the opamps (just like TA, AKA  Cohen topology).

If you are adventurous study the 200B schematic and the TA/Cohen schematics to see the differences and roll your own. What's the worst that could happen? 

JR

 

[Eliani]

I've started a number of threads here and got very helpfull advice regarding modifications of the 200b. I ended up with significant changes, resulting in superior performance. Using the line ins there is no cap in the signal path (except the one in the DC servo), very little noise, distortion and the EQs sound great.

Modifications include the ground mod mentioned before, changing grounding to have a seperate signal ground and a power ground, changing the input circuit around the servo, upgrading many parts to higher quality, modifying the EQ range, upgrading the PSU, using better op amps in most places, adding PSU bypass caps.

It's been A LOT of work, and looks rather messy, but worth in in terms of sound, which is now very clear, transparent, balanced, punchy,.... uncoloured, but it sounds much better than what I could ever get ITB.

I did encounter a lot of your messages on the forums!! Do you still have some of the information available, something you used to modify your 200b?
I'm a electronics enthusiast, sadly I'm not a college degree student... So I'll need rather exact information, something like: if you remove C8, and switch C9 with a 220pF film cap, and replace R11 with a 1%... blahblah... (I can just hear all of you thinking: use the search engine!!!) I did... and will continue to do so, but I'm ready for some clear pointers, something to work with, not first have to think about....

The best thing that could happen would be for Jim Williams to add something here... a small guideline, a link to a hidden wealthy page of how to's... ore some adapted schematics... Anyway, that's my plan. If I end up modding my Soundcraft 200 consoles, and end up with something like yours! I want everybody to know how I did it!!

 

[Eliani]

Im interested to know if anyone has a diagram of the input transamp mod/conversion that Jim Williams does on the 200B fixed EQ module.
TIA

by the way, I did find something about the trans-amp of a 600 console, might this imply to a 200b?
http://www.gearslutz.com/board/geekslutz-forum/262911-trans-amp-mic-pre-mod.html

 

[JohnRoberts]

That may be the thread I was thinking of...

JR

 

[Eliani]

We actually went on with the research!! We've made it as far as a Bill of materials for the Master Section R/H Circuit Diagram. We found some of Jim Williams notes, and Jef Deff's posts...

read more about it here: Eli-Audio.com