2254C build/support thread

[r2d2]

thanks "Jandoste"!
really kind of you,
unfotunately i have not yet taken pcb ...
for my pockets this project is a little expensive...
for now , i'm tryin to "understand" the project ,
and check if i may be able to "make" it .

peace  
(all over)

 

[jandoste]

you're wellcome I love the 2254c and I will build more... AWESOME ! 

 

[r2d2]

...found and posted -1

 

[r2d2]

...found and posted -2

peace
(all over)

 

[muffy1975]

IGOR,

just finished my first 2254c. Worked 1st time just likely the Sontec EQ.

Thankyou ever so much for giving the DIY community some quality/service and most of all......

AWESOME, QUIET and BEAUTIFUL SOUNDING GEAR

regards

michael de A
oxford
englend

 

[muffy1975]

team,

i was wondering what each of the trimpots do?

RV1 changes the bias
RV2 ????      ( um....is this the ouptut gain )
RV3 ?????    ( is this the meter trimpot )
RV4 ??????  ( maybe this is the one marked gain????? near the input transformer )
RV5 ????      ( is this the output gain aswell hahahaha )

In particular, what does the Gain trimpot do ( the one that has no RV designation )???

What I'm getting at is that I'm so unsure as how to set up a mono 2254c at the moment. It sounds great as is, however the St7 is behaving slightly strangely. I have unity gain when the compressor is IN ( with no makeup etc ) but it does seem to be compressing slightly with the threshold fully clockwise.........


Any help would be appreciated even though I am loving the sound of this box already  ;D

Michael de A

 

[haima]

Sounds cool doesn't it? 

Have you tried searching this thread? - i'm sure we've covered calibration... I know, because i've calibrated mine!  ;D

TIP: click on the "print" link on the right top/bottom of the page - then you can search every page using the command+F or control+F function.

 

[pacemaker]

hi guys,
i'm still struggling to find some 1N4153,
but i have some old neve diodes,BAX13
OA202 and AA144,
can i replace the 1N4153 by one those reference ?
regards,
francois

 

[canidoit]

I am considering doing this build.

Can someone please tell me the following to help me with my decision?
- Does this have the oscillation issue that the 33609 build is known for? I would like to use this unit for mastering also.
- Does this have any meters issues, like I have read regarding the Sifam AL19 on the 33609?
- Are there any alternative VU meters I can use which require little mods to it, like are any of Hairballs meters work on this?
- When Igor sais it is a simple version of the 33609, does he mean that this is a 33609 without the limiter or has he changed the 33609 somewhat? eg. So it would be like buying a Lamborghini, and the simplified Lamborghini version would be a volkswagon buggy with a Lamborghini shell?
- I have read that people are struggling to find certain parts, does this problem still occur now and if so, which parts are they?
- Which would you consider building for mix bus and maybe mastering purposes - the 2254 hybrid build or the 33609 build? Please explain why  

Thank you!

 

[haima]

I am considering doing this build.

Can someone please tell me the following to help me with my decision?
- Does this have the oscillation issue that the 33609 build is known for? I would like to use this unit for mastering also.

Not that i'm aware - my unit doesn't oscillate and I haven't heard of anyone else's doing that either.

- Does this have any meters issues, like I have read regarding the Sifam AL19 on the 33609?
- Are there any alternative VU meters I can use which require little mods to it, like are any of Hairballs meters work on this?

Hairball has meters that work with this project - and they are pretty cheap.

- When Igor sais it is a simple version of the 33609, does he mean that this is a 33609 without the limiter or has he changed the 33609 somewhat? eg. So it would be like buying a Lamborghini, and the simplified Lamborghini version would be a volkswagon buggy with a Lamborghini shell?

He has removed the limiter and re-used the front panel space for a sidechain high pass filter and attack control - both of which are very useful IMHO. He's changed the output amp to a single ended class A neve, like the output section of the 1073 etc - sounds good to me. He's changed the switches to be easier to find and cheaper - i've not had any problems with this. You may want to change the steps to be less coarse for very serious mastering... but for basic mastering you'll probably be fine stock.

- I have read that people are struggling to find certain parts, does this problem still occur now and if so, which parts are they?

I had no problems getting parts from mouser. I think Igor includes some matched diodes - which was probably the only tricky bit.

- Which would you consider building for mix bus and maybe mastering purposes - the 2254 hybrid build or the 33609 build? Please explain why 

the 2254 is awesome, and easy to build. my favorite DIY compressor - i like it a lot on all kinds of signals and subgroups - and if i wanted to compress the mix bus i would use the 2254. I don't think there's much reason to consider the old 33609.

 

[Biasrocks]

hi guys,
i'm still struggling to find some 1N4153,
but i have some old neve diodes,BAX13
OA202 and AA144,
can i replace the 1N4153 by one those reference ?
regards,
francois

As I understand it, the 1N4153 is a tighter tolerance version of the 1N4148. I would suggest replacing with those as opposed to your other choices. You may have to sort through a few more to find a match.

1N4148 150mA Iout, 75V Vrrm Fast Recovery Rectifier Operational temperature range from 0°C to 200°C.
1N4153 150mA Iout, 75V Vrrm Fast Recovery Rectifier Operational temperature range from 0°C to 200°C.

http://www.datasheetcatalog.org/datasheet/fairchild/1N4153.pdf
http://www.datasheetcatalog.org/datasheet/fairchild/1N4148.pdf

Mark

 

[Biasrocks]

Can someone please tell me the following to help me with my decision?
- Does this have the oscillation issue that the 33609 build is known for? I would like to use this unit for mastering also.

It's not know for oscillating. Never encountered that problem on my build. If you're talking about the guy that kept bugging Igor about distortion on the build thread. Let's just say you'd never use the extreme settings that he was using to demonstrate the problem.

- When Igor sais it is a simple version of the 33609, does he mean that this is a 33609 without the limiter or has he changed the 33609 somewhat? eg. So it would be like buying a Lamborghini, and the simplified Lamborghini version would be a volkswagon buggy with a Lamborghini shell?

The limiter is left out of the 2254 because it requires another expensive transformer, the 33609 however does not have this problem.

- Which would you consider building for mix bus and maybe mastering purposes - the 2254 hybrid build or the 33609 build? Please explain why  

33609 is more versatile IMO, especially since this project lacks the limiter section. But you do gain a variable attack control not present on the 33609.

But, if you're looking for transparent, look elsewhere.

Mark

 

[canidoit]

Thanks guys

Hairball has meters that work with this project - and they are pretty cheap.

Haima, do you know which VU model it is? I looked through all the VU Hairball has and he hasn't written anywhere, AL19 substitute or equivalent from what I can see.

 

[haima]

the following two meters should work:

http://hairballaudio.com/shop/product_info.php?cPath=25&products_id=64
http://hairballaudio.com/shop/product_info.php?cPath=25&products_id=61

see this thread:

http://www.groupdiy.com/index.php?topic=28923.660

 

[dmp]

Can someone please tell me the following to help me with my decision?
- Does this have the oscillation issue that the 33609 build is known for? I would like to use this unit for mastering also.

My 33609 build is great. It doesn't have problems if it is built correctly, to my knowledge. I lent my unit to a studio for the past month and they gave it high marks. They commented that it was easy to use and easy to make sound right. They were using it side by side with an original metal knob 33609 and found them to sound and behave almost exactly the same. I think the idea that the 33609 project has problems should be put to rest. 
That said, I wouldn't think it is particularly suited for mastering use, as it isn't transparent, in my experience. Even for mixbus compression it has it's own character.
I'm just starting a build of the 2254, so I can't say if it would be better or not. I'm building both, that is what I recommend 

 

[mbdonna]

Thanks to Igor and all you guys for sharing all this precious information on these pages!

Just following your posts and Reanimator's guide, assembling my unit has been a pleasure, with no troubles at all.
Only the power supply is not completed yet,  the toroid still has to come, so I used an AMS rack PSU  to test the unit.

The important thing is that, connected yesterday IT WORKS FINE!! and I'm very HAPPY!!

My 2254c has Carnhill transformers, the aluminum case and frontface are from Grand Master Audio and the VUs are the Hairballs,
I hope you like it.
I need to find some Marconi knobs soon, finish the PSU and calibrate it and that's it ..a DREAM.

Thanks to Igor and all of you again!!
Max ;D

 

[Igor]

Woa. Cool! Congrats! Thanks again to Reanimator!
Passed test pro, all fine?

 

[bruno2000]

Greetings Folks,
A little help, please.  I am working on one of these 2254's assembled by a friend that doesn't work quite properly.  First, I believe that the input trans is wired backwards.  The input trans should be a step-down transformer, right, with a loss of 6 dB, and the interstage a step-up, with a gain of 6 dB?

Second problem, even with the input trans backwards, and adding 6 dB rather than cutting 6 dB, I cannot get the unit to unity gain, even when I ground the control voltage test point.

Any ideas will be appreciated!

Best,
Bruno2000

 

[Igor]

I am working on one of these 2254's assembled by a friend that doesn't work quite properly. 

Ohho))) Who doesn't work properly, friend or compressor?)))
Now, without certain degree of black humour: good luck, and let's fix'em both!

First, I believe that the input trans is wired backwards.  The input trans should be a step-down transformer, right, with a loss of 6 dB, and the interstage a step-up, with a gain of 6 dB?

Exactly. Which trafos are used?

Second problem, even with the input trans backwards, and adding 6 dB rather than cutting 6 dB, I cannot get the unit to unity gain, even when I ground the control voltage test point.

Easiest way, FIRST, check every possible resistor/capacitor/wire/etc. Than, check what is the signal amplitude after interstage trafo.
Measure with DC voltmeter right at input trafo's secondary, do not refer to GND.
Check the out trafo wiring as well. Than, ground CV signal and get audio working properly.

In general, after the input traf, there's -6.5 db (add trafo loss); after the interstage traf, should be -25...26db; at collector of 2N3055, should be -3.8db, if we take input/output zero db between pins 2/3 of XLR's as reference.

 

[bruno2000]

I am working on one of these 2254's assembled by a friend that doesn't work quite properly. 

Ohho))) Who doesn't work properly, friend or compressor?)))
Now, without certain degree of black humour: good luck, and let's fix'em both!

First, I believe that the input trans is wired backwards.  The input trans should be a step-down transformer, right, with a loss of 6 dB, and the interstage a step-up, with a gain of 6 dB?

Exactly. Which trafos are used?

Second problem, even with the input trans backwards, and adding 6 dB rather than cutting 6 dB, I cannot get the unit to unity gain, even when I ground the control voltage test point.

Easiest way, FIRST, check every possible resistor/capacitor/wire/etc. Than, check what is the signal amplitude after interstage trafo.
Measure with DC voltmeter right at input trafo's secondary, do not refer to GND.
Check the out trafo wiring as well. Than, ground CV signal and get audio working properly.

In general, after the input traf, there's -6.5 db (add trafo loss); after the interstage traf, should be -25...26db; at collector of 2N3055, should be -3.8db, if we take input/output zero db between pins 2/3 of XLR's as reference.

Thanks Igor,
Maybe it is I that is not working properly ;-)
The transformers are Carnhill, and right now I'm getting about a 6 dB boost from the input, which is wrong.  Assuming an input level of 0.775 VRMS (0 dBr) into the input transformer primary, I should expect about -25, -26 dBr at the secondary of the interstage trans, but what level should I expect to see at the junction of R27 & R64 of the B193.112 block?
Just trying to work forward.
Thanks in advance for your time and brain power!
Best,
Bruno2000