DB54 - 2254 style compressor {update 22.10.19}

[Ry]

Hi All,

At first this is a great project the boards are great. Thanks for that.
There is only one thing I see in the bom at the resister value. On 1k2 and 1k8 is both BA283R19 written which is the correct one?

Thanks for the info.

 

[dirty1_1garry]

1K8 - correct value

 

[dirty1_1garry]

Hi!
We are preparing for 4th pre-order kits of DB54!

More information here:
https://www.diystudiotoys.com

 

[Undos]

Hi
First this is a very nice project and I want to thank Igor for a  great kit and you guys for the helpful comments in the forum. Finally I have 2 perfectly sounding and working units.

This might be helpful for others with REV 1.0 boards =>

One thing I noticed is when I turned on the COMPRESS switch, the polarity of the signal flipped at the output. In BYPASS mode the polarity didn’t flip. Igor did help me sort it out (see also the original 2254 schematic online). Actually the TRX OUT numbers 5+8 are interchanged on the pcb rev 1.0 at least on my pcb's.  To fix it => Just flip wires on output pins of the output transformer and the polarity should be correct afterwards. So PIN 5 of output trx should go to  TRX OUT 8 on pcb2 and PIN8 of 1166 trx should go to TRX OUT 5 on pcb 2.
Hope that makes sense and please correct me if I’m wrong.

Other thoughts:
- I used Sowter 1717 (Lead version) as output transformer for my unit and it fits perfectly in the 1U case. (See picture)
- Units work perfect with my external Five Fish PSU
- The jumper is for output termination. With the jumper in place the 620 ohm resistor is active and without the jumper 620 ohm resistor is not used.
The compressor sounds awesome and the additional attack and release times are great.
I can recommend this project.
Happy building

tim

 

[dirty1_1garry]

Hi
First this is a very nice project and I want to thank Igor for a  great kit and you guys for the helpful comments in the forum. Finally I have 2 perfectly sounding and working units.

This might be helpful for others with REV 1.0 boards =>

One thing I noticed is when I turned on the COMPRESS switch, the polarity of the signal flipped at the output. In BYPASS mode the polarity didn’t flip. Igor did help me sort it out (see also the original 2254 schematic online). Actually the TRX OUT numbers 5+8 are interchanged on the pcb rev 1.0 at least on my pcb's.  To fix it => Just flip wires on output pins of the output transformer and the polarity should be correct afterwards. So PIN 5 of output trx should go to  TRX OUT 8 on pcb2 and PIN8 of 1166 trx should go to TRX OUT 5 on pcb 2.
Hope that makes sense and please correct me if I’m wrong.

Other thoughts:
- I used Sowter 1717 (Lead version) as output transformer for my unit and it fits perfectly in the 1U case. (See picture)
- Units work perfect with my external Five Fish PSU
- The jumper is for output termination. With the jumper in place the 620 ohm resistor is active and without the jumper 620 ohm resistor is not used.
The compressor sounds awesome and the additional attack and release times are great.
I can recommend this project.
Happy building

tim

My double congrats!

 

[evil grill]

Does anyone know where to get the needed transformers in Europe?
Are there any Lundahl versions that can be used?

 

[Rob Flinn]

Does anyone know where to get the needed transformers in Europe?
Are there any Lundahl versions that can be used?

www.audiomaintenance.com

 

[dirty1_1garry]

www.audiomaintenance.com

exactly!

 

[evil grill]

Thanks guys!

 

[Spencerleehorton]

Does anyone have a schematic which details the steppes attack switch pot please?

 

[dirty1_1garry]

Does anyone have a schematic which details the steppes attack switch pot please?

I have)
attack controlled by R16 on BA191 card. Originally it's fixed on 270R but can be changed for less or more resistance.

 

[Spencerleehorton]

Ah ok, so changing the 270R in between the two transistors on the ba191, I can see you have suggested 1k for 0.5ms going up to 2.7k for 50ms, does this mean that 270R was faster attack than 0.5ms?

 

[sintech]

So this project has just Compression and no limiting? It has the 185 card that has the limit side chain, guessing that's half loaded, just for the gain element.

On the original 2254 schematic, the meter is fed from R12 (6.8k) What values are people finding this to be for a standard GR meter/or does the front panel PCB contain another meter drive circuit?

 

[dirty1_1garry]

So this project has just Compression and no limiting? It has the 185 card that has the limit side chain, guessing that's half loaded, just for the gain element.

On the original 2254 schematic, the meter is fed from R12 (6.8k) What values are people finding this to be for a standard GR meter/or does the front panel PCB contain another meter drive circuit?

Hi!
yep, only compressor, no limiter. For limiter you need 191 card, DB54 don't have it.
DB54 use 10mA meter and original drive circuit. Meter drive circuit contain trim pot for adjusting.

 

[Zergonion]

If anyone's interested, I'm selling my non-working unit:
https://groupdiy.com/index.php?topic=74547.0

 

[dirty1_1garry]

If anyone's interested, I'm selling my non-working unit:
https://groupdiy.com/index.php?topic=74547.0

what happened? we can find a bug

 

[mrdarwin]

Hi there!
During this special confining period, I decided to try to make this machine full operationnal.
Here are the problems:
1. Unity gain is impossible for me... still +1.4dB when comp engaged without gain, and trimpot is set on max. Anyway...
2. Really poor meter tracking... meter shows 12dB when there is 4dB compression. I use the classic ssl meter 1mA. Trimpot does anything right...
3. Oscillation appears after 14dBu gain make-up.

Is there some solutions to solve these problems?

 

[dirty1_1garry]

Hi! Lets see

1. Unity gain is impossible for me... still +1.4dB when comp engaged without gain, and trimpot is set on max. Anyway...

There is R52 near VR3 trim that limit minimum gain of BA283NV amp. Standart it should be 220R. For making less gain you should use higher values, 270R or 330R may be.  Or there is R39 on face board that serves as a limitation for make-up pot minimum position. You can make it lower.

2. Really poor meter tracking... meter shows 12dB when there is 4dB compression. I use the classic ssl meter 1mA. Trimpot does anything right...

you can experiment with VR1 which is meter calibration trim or with R12 on BA185 board which limit VR1. I think you should make it lower... but may be not.

3. Oscillation appears after 14dBu gain make-up.

Hmmm, that's strange. Not as typical problem. I think that's  bad  transistor on BA283 board. If you have one more BA283 (may be) try it and if there is no oscilations with new boards you should find bug in bad one.

 

[Spencerleehorton]

I’m using a 0.5w meter, so should I use a meter gain pot?
I think the audio maintenance schematic has one but I might be wrong?
Do you have a schematic you could share so I could check my build please?
As I seem to be having some of the same problems mentioned here

 

[mrdarwin]

I’m using a 0.5w meter, so should I use a meter gain pot?
I think the audio maintenance schematic has one but I might be wrong?
Do you have a schematic you could share so I could check my build please?
As I seem to be having some of the same problems mentioned here

Can you describe all your problems please?