GroupDIY Bridge compressor.

[plumsolly]

Interesting! So, do you take a measurement at every octave or so? Have you ever confirmed that your generator is flat? I believe mine rolls off a bit at around 20hz. I suppose I could make a curve of my generator output, and subtract it from my measurement. I have used various free computer programs, but your approach is tempting because it cuts the converters, patch bay, etc out of the equation.

Best,

Ben

 

[DaveP]

Ben,

I do 20,30,40,50,70, 100, 200, 500, 1k, 2k, 5k, 10k, 15k, 20k,25k 30k, 40k, 50k.

Its basically every octave in the mid-range but more detailed at both ends where the problems usually manifest themselves.

The sig gen was expensive (my company's) and is accurate according to the scope from 1Hz to 2MHz

I like simple!

best
DaveP

 

[DaveP]

I have equalised the DC output of the CV over the whole frequency range so that it's flat whatever the frequency.  It raises the possibility of having some kind of "tone control" in the side-chain which might have interesting effects, but that's for another day.  It would also be possible to fit send and return sockets to fit say a Pultec to use as a de-esser too.

Anyway, I have finished the design work now, the next posts will be pics of the metalwork and construction.

best
DaveP

 

[JayDubrek]

Nice one with persevering on this Dave...looking forward to seeing your build!
Jay

 

[DaveP]

Here we go:-

From these simple ingredients..............................................

Including, 57 Resistors, 35 Capacitors, 8 Tubes, 5 Transformers, 16 diodes and 1 MOSFET......

I will attempt to...... (better not say cook)....... assemble a redesigned version of a Collins  26C Bridge Compressor, originally designed in 1938.  It will be a 3u, 19" rack unit.  Made old school Point to Point, so help me God!

I started this project back in last October tryinging a mock up of a 26W, I could not make that work satisfactorily so I tried the 26C with more success.

This is the plan:

When its finished I'd like a pro UK studio to try it out, volunteer required!

If that goes ok, I will ship it to a volunteer in the US for appraisal.  He must undertake to ship it to the next person who wants a go and so on.  When this process is complete the final person must undertake to auction it on the forum.  I don't want anything for making it but I want to re-coup the shipping costs, the proceeds will then go to the Forum.  If anyone wants to make their own then they should make a suitable donation when they download the schematics and parts list/BOM.

Thanks to all for your support, let me know if you want to go on the audition list.

best
DaveP

 

[plumsolly]

You are a champion, Dave.

Best,

Ben

 

[ruairioflaherty]

When its finished I'd like a pro UK studio to try it out, volunteer required!

If that goes ok, I will ship it to a volunteer in the US for appraisal.  He must undertake to ship it to the next person who wants a go and so on. 

Exciting stuff Dave!  I nominate Mr. Strangeandbouncy Andy as the UK ear.  I'd love to be on the list for a U.S. listen at some point.  Anyone in L.A. who's interested in checking out the unit is welcome come by my room. If Doug EMRR is interested I'd nominate him as first on the U.S. list.

Everything about this project has been the very definition of what this forum came from - from the educational spirit to the generosity.  I've got to say I was coming here less and less but projects like this give me hope.

Cheers,
Ruairi

 

[DaveP]

Ruairi
Thanks for those kind words, I do my best.

I'll put you on the list,

All the best

Dave

 

[Joechris]

Yah, thanks Dave, its been a joy to follow this project, with all its ups and downs.
I hope the compressor will take a scandinavian tour as well..

 

[letterbeacon]

Just want to chime in to say that this thread has been a hugely informative thread.  Really enjoyed reading through, while learning a lot.  Can't wait to see the build progress!

 

[JayDubrek]

If your other offers fall through I'd be happy to test it out at Dubrek!
Cheers
Jay

 

[DaveP]

Thanks,

Ben, Jay, letterbeacon, Joechris.

Watch this space!

best
DaveP

 

[emrr]

of course.  Lassoharp is right up the road, too. 

 

[DaveP]

Doug,

I was hoping you'd be the main man.

I didn't know Alan was close by (probably means less than 500 miles in the US!).  If he can help too it would be great, he has been very supportive.

I know your opinions about packing gear for transit, so rest assured it will have a case that will be up to the job.

I don't want to get too far ahead of myself, its just bits at the moment, but its good to have something to aim for.

best
DaveP

 

[lassoharp]

um, you know I will be up there for some A/B tests.  ;D  8) ;D

Looking forward to it!

 

[DaveP]

I'm counting on it Alan!

Dave

 

[shabtek]

What Ruairi said...


top notch all around

 

[DaveP]

I've been away for a week but now construction has begun.

Back panel: Should be enough tube sound to satisfy anyone

...8 tubes and 3 audio transformers in a 3u......?!

Bought some Vintage meters off ebay.

I'll need to print new scales and I'll try for the big one if there's room.

Cut down coffee cans make good diy transformer screens!

More next week.
DaveP

 

[emrr]

Right on.

Was thinking (sorry!); simple to build so that corrective EQ networks are easy to disconnect?  That way the audition committee can compare?

 

[DaveP]

Doug,

I think there are three choices....

1.  A simple bypass as in the original schematic.

2.  A simple on/off to the side chain amp.

3.  A bypass to the correction network on the bridge transformers (coil/caps/res).

I don't think option 3 will be very audible as it mainly affects >20kHz and square wave ringing.

I am about to drill the front panel so I will incorporate a switch position so that guys can wire it to their preference,  I can show options in the manual if you like?

best
DaveP