DB54 - 2254 style compressor {update 22.10.19}

[slipperyflax]

Twentytrees have you summed up what your total project cost was?  Or maybe an estimate

 

[TwentyTrees]

Hey Slippery,

I’ve not got exact figures to hand as I spread the orders over a long period, but I’d estimate maybe £4-500 per channel for a stereo build - of which a large part was transformers (6 Carnhills for two channels) and the panel, which was powder coated and engraved by Frank.

Not cheap, but probably my favourite build so far. Wish I could get the meters to track again reduction accurately over the whole range, but no matter, it forces me to use my ears!

(The meters on my unit track g/r accurately to about 4dB but then the scale goes way out - no matter how I set them up I couldn’t get them accurate across the whole meter range).

Cheers,
Andy

Twentytrees have you summed up what your total project cost was?  Or maybe an estimate

 

[mrdarwin]

Please, what resistor value did you use for lightning 8027 meter?

 

[mrdarwin]

Finished unit, same problem with meter...
probably due to sifam's clone meter, range is ok with another 1mA scale meter... but which doesnt fit in the unit...

Hey Slippery,

I’ve not got exact figures to hand as I spread the orders over a long period, but I’d estimate maybe £4-500 per channel for a stereo build - of which a large part was transformers (6 Carnhills for two channels) and the panel, which was powder coated and engraved by Frank.

Not cheap, but probably my favourite build so far. Wish I could get the meters to track again reduction accurately over the whole range, but no matter, it forces me to use my ears!

(The meters on my unit track g/r accurately to about 4dB but then the scale goes way out - no matter how I set them up I couldn’t get them accurate across the whole meter range).

Cheers,
Andy

 

[frederickalonso]

I have 2 working units but for some reason I have in Bypass the original sound at same levels as source.
Once I switch to compressor ON > leds all work, sound is there and compression settings work. The problem at Compressor ON = I hear 20% compared to original level and If I tweak the 5K I can make it a little louder but on both compressors I have too much noise that the unit is basically not ready for use in the studio. Can it be the 2N3055G is defect?

Update: While searching for problems I touched by accident the pins from my Carnhill VTB9045 and now one of the two units has a very loud hiss noise.

Bit frustrated here. I ordered 4 new 2N3055G's to match them and a bunch new BC109C's to replace BC550C's.
I hope this fixes the issues.
Will keep you updated If this make sense. Based upon 109 vs 550 there should be less noise on the opamp stage.

 

[frederickalonso]

A small shot from the Unit when Compressor mode is on..

https://www.instagram.com/p/BoJYfeOnn-I/?taken-by=alonso.frederick

 

[frederickalonso]

Most issues are fixed now. So I replaced both 2N3055G's and on the bad ones of the two I replaced the R7 (47R/1W) resistor.
For some reason this was the guy that gave all those issues.

When calibrating I had 2.3Vdc but after 30 second it started to rise like hell.
That gave the 2N3055 probably too much voltage which caused this hiss/hum noise.

To be sure I also replaced the matched pairs on BA185 with new BC109's.

Long story short. I have a nice sounding unit now.
Just the volume in compression mode is not yet right.
Maybe this is the difference in tranfo setup. I used all Carnhill's stages. (9045, 9046, 1148)

Happy I finally can start using it. 8)

 

[dirty1_1garry]

Hi folks!
Did I miss something?)
If you need my help - feel free to contact me directly.

Igor

 

[frederickalonso]

Hi folks!
Did I miss something?)
If you need my help - feel free to contact me directly.

Igor

Hi Garry,

I just want to ask if you have an idea what can be the problem in volume drop when the compressor is switched in.
Bypass vs comp in = 40% difference in volume at this moment.
No hum or hiss, all the rest is working fine and I love the units.

Maybe transformer related? I used all Carnhill transformers on all 3 stages.

I could PM you but on this forum it could help other people here as well.

 

[dirty1_1garry]

Hi Garry,

I just want to ask if you have an idea what can be the problem in volume drop when the compressor is switched in.
Bypass vs comp in = 40% difference in volume at this moment.
No hum or hiss, all the rest is working fine and I love the units.

Maybe transformer related? I used all Carnhill transformers on all 3 stages.

I could PM you but on this forum it could help other people here as well.

Check transformer wiring first. Then I can recommend to measure signal level during signal chain, as originally you should not get a such level drop.

 

[frederickalonso]

Check transformer wiring first. Then I can recommend to measure signal level during signal chain, as originally you should not get a such level drop.

I followed the numbers from the Wiring Guide correctly. The only thing that I can try is switch the output transformer so the used input side becomes the output and vice versa. But don't think this will make much difference and is a good idea.
I took a good look on the Carnhill transfo pdf and from their numbers vs yours it's just the same.


Would love to know some measure levels on the BA card pins for example from a working unit so I can dig deeper.
Strange enough I have it on both units > same voltages and levels on both.

 

[dirty1_1garry]

I followed the numbers from the Wiring Guide correctly. The only thing that I can try is switch the output transformer so the used input side becomes the output and vice versa. But don't think this will make much difference and is a good idea.
I took a good look on the Carnhill transfo pdf and from their numbers vs yours it's just the same.


Would love to know some measure levels on the BA card pins for example from a working unit so I can dig deeper.
Strange enough I have it on both units > same voltages and levels on both.

Yes, if tranformers wiring is Ok, next step would be check signal level during sound path.
Send 1Vac to the input trx and measure level at points:
1) after input trx (pin7)
2) before (pin2) and after(pin7) of interstage trx
3) output pot pin3
4) BA283 card pin F
5) output trx secondary

 

[frederickalonso]

Yes, if tranformers wiring is Ok, next step would be check signal level during sound path.
Send 1Vac to the input trx and measure level at points:

1) after input trx (pin7) = 0,1Vac
2) before (pin2 = 0,1Vac) and after(pin7 = 0,1Vac) of interstage trx
3) output pot pin3 = 0,1Vac
4) BA283 card pin F = 0,1Vac
5) output trx secondary = 0,1Vac

I also have put 1Vac on the interstage to test a little bit more...
on pin 2 and after pin 7 of interstage trx and then I have these results:

1) after input trx (pin7) = 0,5Vac
2) before (pin2 = 1Vac where I feed 1V) and after(pin7 = 1Vac) of interstage trx
3) output pot pin3 = 1Vac
4) BA283 card pin F = 1Vac
5) output trx secondary = 1Vac

 

[dirty1_1garry]

I also have put 1Vac on the interstage to test a little bit more...
on pin 2 and after pin 7 of interstage trx and then I have these results:

1) after input trx (pin7) = 0,5Vac
2) before (pin2 = 1Vac where I feed 1V) and after(pin7 = 1Vac) of interstage trx
3) output pot pin3 = 1Vac
4) BA283 card pin F = 1Vac
5) output trx secondary = 1Vac

Hi!
31267 as input trx here wires for stepdown, so that's Ok that you get less Vac on secondary.
10468 as interstage transformer here is wired for 1.2K:4.8K, step up.  So it will gives more Vac on output then on input. But as it connected as balanced on input with center tap,  you could not just send 1V on pin2 (yes, I was wrong that you can), or you should disconnect all primary winding for making a measure.
Check that screen from 3/4 pin do not connect to ground.

Do you already adjust gain trim pot?
like described on page 18 of assemble guide:
https://drive.google.com/drive/folders/0B7-dE6xaVqWXUlNHREw1ZlJkWUE

Check and let me know again.

May be I just will assemble one more DB54 by my self and check what Vac's I have.

 

[frederickalonso]

Hmmm, this was interesting.

So I disconnected the ground wire as it normally should be like but this made a huge difference on the
47R voltage which should be 2.3VDC.

I removed the ground on pin 3 and 4 at the interstage transformer and adjusted (calibrated) the 47R again.
This fixed my issue.

So before the modification I had 2.3VDC  on R7 (47R) and after the ground removal I had something like 5VDC that needed a calibration again to 2.3VDC.

Why this fixed the issue, I cannot get it.  :

But It's working fine now! So happy! 1/3 more gain then input volume now, and a nice low end.
Thanks Igor!

 

[dirty1_1garry]

Hmmm, this was interesting.

So I disconnected the ground wire as it normally should be like but this made a huge difference on the
47R voltage which should be 2.3VDC.

I removed the ground on pin 3 and 4 at the interstage transformer and adjusted (calibrated) the 47R again.
This fixed my issue.

So before the modification I had 2.3VDC  on R7 (47R) and after the ground removal I had something like 5VDC that needed a calibration again to 2.3VDC.

Why this fixed the issue, I cannot get it.  :

But It's working fine now! So happy! 1/3 more gain then input volume now, and a nice low end.
Thanks Igor!

Well, I cant say that I understand everything what you've done, however I'm happy that it helps)

 

[dirty1_1garry]

News for today.
9 kits left from third batch, with or without cases.
Contact me via PM or via email in profile.

 

[dirty1_1garry]

Hi guys!
I’m in the process of assembling one more DB54.
So if anyone want to clarify any build aspects - welcome!) I can not just answer your questions but also check them twice on new real device.

 

[dirty1_1garry]

And one more news!
Black Friday Sale!
Contact our DB54 kit reseller till Monday and get your kit cheaper!)

 

[dirty1_1garry]

One more DB54 was born!
Will post some video samples during a week.