Tube Channel strip

[APL]

I am interested in building a tube channel strip (preamp, compressor and EQ)  I can see the advantage of one unit instead of 3 separates,  saving on 2 psu’s and additional input/output transformers plus space saving. I don’t have a clue how to design my own but I was curious whether any of the projects here could form the basis of the channel strip and adding the missing components.

I realise this is probably totally impractical or require extensive redesign but if I don’t ask I’ll never know.

Compressor Route
I read a post which said an LA2A can work as a Preamp/compressor by simply adding the usual mic inputs, phantom, phase circuitry etc before an input transformer. Is that correct? Is it that simple?
Would that work with other compressors eg D-AOC?

Preamp route
This is my preferred route.  Could a simple opto compressor circuit be integrated into a G9 pramp? I only want a simple vactrol based compressor (one knob) with a HPF side chain and possibility of stereo link. I’ve seen some circuits described here, but how easy would it be to integrate them into a G9?

EQ
In either case could you simply add EQ eg EZ Helios or passive section of G-Pultec before or within the output stage or does it all have to be carefully matched? Inter stage transformers or circuitry or even another amplification stage?

 

[G-Sun]

I guess I'd look at something like the Ians tube + eq combo, then something la2a maybe.
http://www.ianbell.ukfsn.org/EzTubeMixer/

 

[APL]

Firstly I just noticed I posted this in wrong topic I meant to put it in Drawing board. Sorry.

Thanks for the reply. Ive been watching Ians work for a while its always interesting. I know there are plans for compressors and the lunchbox psu could be a good basis.

I did like the idea of G9 route with an integral compressor if it had been practical idea .  I recently finished my first build a G- Pultec  and I like Jacobs designs.

Im looking for basic compressor The LA2A is nice but probabley not what i need

 

[gyraf]

Preamp route
This is my preferred route.  Could a simple opto compressor circuit be integrated into a G9 pramp? I only want a simple vactrol based compressor (one knob) with a HPF side chain and possibility of stereo link. I’ve seen some circuits described here, but how easy would it be to integrate them into a G9?

Yes, that would be possible. Best option would probably be to have an opto-ldr attenuation stage just before the output trim potentiometer - although this may (will) mess up high-pass-filter frequencies (but who needs those..)

EQ
In either case could you simply add EQ eg EZ Helios or passive section of G-Pultec before or within the output stage or does it all have to be carefully matched? Inter stage transformers or circuitry or even another amplification stage?

No, not really possible, as most EQ stages requires medium-to-low drive impedances, and we do not have that much driving power available.

jakob E.

 

[APL]

Thanks for the reply Jacob. Sorry to ask more questions but for my education:

1 opto-ldr attenuatior - I  will look into that I found a silonex NSL32sr2 which seems a possibility

2. When you say it may mess up high pass frequency. Do you mean it will always effect frequency due to variability as it operates or do you mean the filter values would need to recalculated( once) to take account of fitting attenuator and then it could operate ok.

3. EQ I assume you mean you would need to basically connect a complete pultech  with valve output section, onto G9 output. If so which, if any, of the transformers could be left out G9 o/p, Pultec i/p or O/P

4. As I suspected its not turning into the easy build I envisaged there is at least 4 different voltages required for a start.

Actually what set me off was reading a review of a tube channel strip which had pre/compressor and EQ all within 2 tubes/4 active stages with a semiconductor HPF side chain on compressor. But I guess something like that would need to be designed from scratch.

 

[APL]

one last idea before I give up on this g9 channel strip idea.

We have the possibility of puting a compressor in place of HPF, but you cannot have eq.

The G9 is dual channel ,therefore is you use it as a single channel you have have 2 tubes spare. to use for eq amplification with a bit of rerouting. No additional PSU voltages.
Perhaps the first stage of the spare channel could be converted into a more complex Compressor.
Just a thought .