Re: Channel Strip Project (API+Pultec+1176)
« Reply #20 on: May 18, 2020, 03:56:12 PM »
Take an 1176, convert it to ICs and you get a distressor.  It definitely changes the sound,  but wouldn't say it's not worth doing. The fet smack is still similar.

Really?? Oh damn.... now that's interesting... I need to find out more about that...


TwentyTrees

Re: Channel Strip Project (API+Pultec+1176)
« Reply #21 on: May 18, 2020, 05:50:22 PM »
And if you're interested in how tiny an 1176-type circuit can get...

https://store.louderthanliftoff.com/products/implode-colour-module

(Caveats: they describe it as the full preamp and detector circuitry of the Rev F, though I've not compared schematics; assembled only, no kits; and I expect there's a ton of SMD parts on the bottom of the board. Still pretty good though, for smaller than a credit card!)

Re: Channel Strip Project (API+Pultec+1176)
« Reply #22 on: May 18, 2020, 05:55:26 PM »
And if you're interested in how tiny an 1176-type circuit can get...

https://store.louderthanliftoff.com/products/implode-colour-module

(Caveats: they describe it as the full preamp and detector circuitry of the Rev F, though I've not compared schematics; assembled only, no kits; and I expect there's a ton of SMD parts on the bottom of the board. Still pretty good though, for smaller than a credit card!)

Holy damn! That quite the achievement ahah! In fact this point in the right direction....

And yes you're right the bottom is pretty filled!

That's great to get a sense of what's possible though...
« Last Edit: May 18, 2020, 06:00:23 PM by Dyonight »

squarewave

Re: Channel Strip Project (API+Pultec+1176)
« Reply #23 on: May 18, 2020, 08:48:50 PM »
API312 clone -> Harrison High/Low pass filter clone -> Solid State Pultec -> 1176

In short, I want to eliminate the transformers of:

Api 312 Output
Pultec Input and Output
You mean like this?

  https://groupdiy.com/index.php?topic=65032.0

Are you located in the US lower 48? If yes, here is a PCB for the Pultec:

  https://groupdiy.com/index.php?topic=74351.0

But I I'm only giving out 5 / person (and I don't have 16 of any one board anyway). But it might be worthwhile to play around with them just to help you figure out things. I also have similar boards for the API and 1176 but I didn't include them in the post because I believe there are errors and I don't recall what they are. They're probably minor. Something that is easily fixed by cutting a trace and jumping something with a little piece of bus wire. But it might not be fun to debug.

Otherwise, what you describe is perfectly doable (obviously). There are a few concerns however:

One is that if you make one giant board and there's a problem (and there always is - I don't think I've ever made a PCB that didn't have an error the first time around), it could be very disappointing and expensive to fix. That's why I made lot's of little boards so that if (when) there's a problem I can just swap out the one board. Many early console designs where the same way. There was a frame with edge connectors that cards would mount to. A little different from my "stac" of PCBs separated by standoffs but the same conceptually. If you just don't like the whole prototype-ish vibe, the next step up would be to make a backplane with several daughter boards.

The second concern is matching levels. The API gain is only 40dB. If I'm not mistaken, in a real API console, the "output" transformer is actually for interfacing with the mix bus. Then there would be an output that amplifies more. Also, the 1176 cannot handle a lot of signal on the input. So you could use the 40dB, run through the pultec and 1176 and then add another fixed 20dB on the output stage. But that might not be the best for noise performance. Generally, for the best noise performance, you want to make all of the gain up-front. So the alternative would be to put an extra fixed 20dB right after the API pre, put a trimmer in front of the 1176 followed by a makeup stage just for the 1176. That's what I did in my "Channel Strip 1".

The final concern would be scaling up to 16. The thought of building 16 channel strips like that makes me twitch a little. That I don't have a solution for but I would imagine the procedure for building 16 efficiently and correctly is not that different from building 1,600 so I assume you have some serious time and money to burn.
« Last Edit: May 18, 2020, 08:52:13 PM by squarewave »

Re: Channel Strip Project (API+Pultec+1176)
« Reply #24 on: May 19, 2020, 12:12:52 PM »
You mean like this?

  https://groupdiy.com/index.php?topic=65032.0

Are you located in the US lower 48? If yes, here is a PCB for the Pultec:

  https://groupdiy.com/index.php?topic=74351.0

But I I'm only giving out 5 / person (and I don't have 16 of any one board anyway). But it might be worthwhile to play around with them just to help you figure out things. I also have similar boards for the API and 1176 but I didn't include them in the post because I believe there are errors and I don't recall what they are. They're probably minor. Something that is easily fixed by cutting a trace and jumping something with a little piece of bus wire. But it might not be fun to debug.

Otherwise, what you describe is perfectly doable (obviously). There are a few concerns however:

One is that if you make one giant board and there's a problem (and there always is - I don't think I've ever made a PCB that didn't have an error the first time around), it could be very disappointing and expensive to fix. That's why I made lot's of little boards so that if (when) there's a problem I can just swap out the one board. Many early console designs where the same way. There was a frame with edge connectors that cards would mount to. A little different from my "stac" of PCBs separated by standoffs but the same conceptually. If you just don't like the whole prototype-ish vibe, the next step up would be to make a backplane with several daughter boards.

The second concern is matching levels. The API gain is only 40dB. If I'm not mistaken, in a real API console, the "output" transformer is actually for interfacing with the mix bus. Then there would be an output that amplifies more. Also, the 1176 cannot handle a lot of signal on the input. So you could use the 40dB, run through the pultec and 1176 and then add another fixed 20dB on the output stage. But that might not be the best for noise performance. Generally, for the best noise performance, you want to make all of the gain up-front. So the alternative would be to put an extra fixed 20dB right after the API pre, put a trimmer in front of the 1176 followed by a makeup stage just for the 1176. That's what I did in my "Channel Strip 1".

The final concern would be scaling up to 16. The thought of building 16 channel strips like that makes me twitch a little. That I don't have a solution for but I would imagine the procedure for building 16 efficiently and correctly is not that different from building 1,600 so I assume you have some serious time and money to burn.

I mean like this indeed!

I live in Quebec, Canada so unfortunately no I'm not it the US.

I plan to build each piece on its own, test them individually, test them togheter and then see if it make sense to integrate everything on a single board or not. The answer will probably be no but I'll see at that time what make sense to be grouped and what does not.

Indeed, the way to interface each board togheter while maintaining the best noise ratio will be a major concern. Thanks for your input on that!

Fitting 16 channels in one enclosure and using one common psu is indeed the ultimate goal. I don't have infinite money and I need to spend my time where it count. I'll see where that whole thing takes me. There's a lot I need to figure out before scaling that chimera to 16!

Cheers!

john12ax7

Re: Channel Strip Project (API+Pultec+1176)
« Reply #25 on: May 19, 2020, 05:42:43 PM »
A typical api style pre might have 40 dB gain from the opamp.  But don't forget the input transformer adds another 18-20 dB. So you still get close to 60 dB gain even without the output transformer.

But it's definitely good to consider the overall gain staging as it can help cut down on parts and overall cost.  You may not even need the typical makeup gain stage after the pultec filters if they are always feeding an 1176 style compressor.

Re: Channel Strip Project (API+Pultec+1176)
« Reply #26 on: May 19, 2020, 08:37:43 PM »
A typical api style pre might have 40 dB gain from the opamp.  But don't forget the input transformer adds another 18-20 dB. So you still get close to 60 dB gain even without the output transformer.

But it's definitely good to consider the overall gain staging as it can help cut down on parts and overall cost.  You may not even need the typical makeup gain stage after the pultec filters if they are always feeding an 1176 style compressor.

That's the kind of thoughts I'm having. Since it will be one "unified" device there's probably a couple of stages that won't be required, at least that would be great.

I've also read somewhere (and heard it here from you) that the output tx only add 6db, so I guess that won't matter that much. We'll see.
« Last Edit: May 19, 2020, 11:35:11 PM by Dyonight »

fazer

Kim Re: Channel Strip Project (API+Pultec+1176)
« Reply #27 on: May 20, 2020, 01:20:28 AM »
The output transformer in a 312 is a part of the sound and provides the drive for the pultec along with balance.  I would keep it.  The 1176 does not need the input transformer (pad UTC 08) so I would loose that.  Also compression on everything all the time is not necessary for me if the artist has a nice touch so bypass is as important as the processing.  But I like breath in the sound or dynamics and a pop world may not live there. Anyway I’m just saying that pounding everything is not as important as say the bass kick snare and LV.  But other things I like weaving around the foundation elements.  Opinions vary.  Also it’s nice having a few preamps with different character.   Mind you I have a 24 channel API and I find the quick transient mid sound (in your face), is not what I’m after on all instruments.  The avid pres I have in one of my I/Os sound great on a acoustic guitar with a 1/2 in  condenser like a 451 or km84.  Anyway a neve preamp On a few channels and a couple of green pre would be good also.  1176’s are nice but every channel?  Mind you I’m old and so old school.  Anyway,  What do I know. I like 3A’s on vocals and api 525’s on guitars way better than modern 527’s. Just saying ???

squarewave

Re: Channel Strip Project (API+Pultec+1176)
« Reply #28 on: May 20, 2020, 02:56:22 AM »
I could see leaving the 1176 in all the time but with the usual input level control so that you can engage it more or less or not at all.  That will give the channel a fairly predictable upper limit on output level which could be nice. Not sure I would use the transformer in between. It's just not going to be fully appreciated there as opposed to on the output with another 2520 using whatever the usual API output circuit is. That's what I did in my channel anyways (although I just used a regular op amp driving the tranfo).

 

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