2254C build/support thread

[juniorhifikit]

@Haima: all the best! How old you become?
@king-rb: can you please explain the problem in other words to let me a try to help?
What is your comp's gain without compression? (I.e. can you get to unity gain without
compression/makeup?)
Which 820R you mean and at which calibration stage you can't get down
the gain?

For me, when trying to adjust for unity gain with compressor in; no compression and no make-up gain added; the gain trim pot is all the way down and I'm still almost 5 dB above unity.  Should I just change R"19 (in series with the gain trim pot) from 820 Ohms down to something smaller?  Or is there possibly something wrong elsewhere causing the gain to be too high?  With a 5K trim pot, I don't imagine changing the 820 Ohm series resistance will change much (it's only 16% of trimmer value).  Anyone else have trouble trimming down to unity gain?

 

[Igor]

i turn 31 years young tomorrow

HURRAY!!!!!! Happy happy birthday!!!!!! All the best, wish you be happy and good health!

i'm planning a nice day in the workshop stuffing my 2254 boards!

That's cool. Don't forget to take some beers after all this works!

>i changed the R``19 to 715R
>input gain is 0.775V AC
>with the gain trim i can get to 1.150V AC minimum
>i have to trim RV2 Controller Voltage to get the gain down to 0.775V AC
>but then i dont have enough space to get the voltage down to 0.308 with the 3v on the Link
aso...
i used bc177 instead of bc214

Changing r"19 lower will give higher gain.
Check if gain trimpot is 5k. Check the signal flow,
maybe, somehow transformers are connected 1:4 instead of 1:2 etc.
Maybe, wrong resistor somewhere. Which transformers did yuy used and how did you connected them?
/this was discussed in this thread/

I have read this whole thread, and I am sorry
if I missed what I am about to ask.
For a mono unit, I need a 15VA 2 x 12V toroid.
30 VA is only needed for a dual version. So far so good?

Yes, 15VA will be OK.

Re: availability of BC214 - i found futurlec has them for a pretty good price:

http://www.futurlec.com.au/price1.jsp?part_no=BC214

i just ordered a batch. remains to be seen what brand etc they are... i'll post my results here

TELL US!!!!!!

For me, when trying to adjust for unity gain with compressor in;
no compression and no make-up gain added; the gain trim pot
is all the way down and I'm still almost 5 dB above unity. 

That's right...except 5db

Should I just change R"19 (in series with the gain trim pot)
from 820 Ohms down to something smaller? 
Or is there possibly something wrong elsewhere causing the gain to be too high? 

Higher r"19+trimpot less gain.
I have a strange feel that somehow transformers connected 1:4 instead of 1:2
or there's a wrong resistor somewhere....

Anyone else have trouble trimming down to unity gain?

Yes, some tens posts ago, lower gain....IIRC it was solved, good luck and tell us!

 

[Rybow]

Thanks Igor! I just wanted to make sure on that one. Can't wait to get started.  ;D

 

[haima]

Re: availability of BC214 - i found futurlec has them for a pretty good price:

http://www.futurlec.com.au/price1.jsp?part_no=BC214

i just ordered a batch. remains to be seen what brand etc they are... i'll post my results here

TELL US!!!!!!

OK - the BC214 package arrived from futurlec (it was delayed due to them not being able to source another part of the order - which they didn't tell me untill a week later... after i asked them when to expect the package - to their credit they did fedex it to me when i asked them to hurry up)

the transistors i was sent are marked with a "f" (Fairchild) and "BC214LC" - notice the "L" which means they have the ECB pinout, rather than the more common CBE. but they will fit the 2254C boards easily if you fit them at an angle, just follow the nice legending igor has put on the top screenprint!

igor - i'm glad you used "staggered" pins on the transistors, rather than all in a line - makes these kind of pinout substitutions easier!

i've tested a few of these BC214LC with my cheap DMM and they are coming up 400-500 hFE - mostly around 450.

here's a link to the fairchild datasheet: http://www.vakits.com/datasheets/Transistors/BC214LC.pdf

BTW - haven't got much time right now for DIY, so it might be a few weeks until i can post results of these transistors in circuit  :'(

 

[Igor]

Cool! If these are BC214LC, they will work perect.

notice the "L" which means they have the ECB pinout, rather than the more common CBE. but they will fit the 2254C boards easily if you fit them at an angle, just follow the pcb legending

This is absolutely right.

 

[Igor]

The build manual from Reanimatorstudio is here:

http://twin-x.com/groupdiy/thumbnails.php?album=409

 

[Rybow]

Thanks Igor! Got the docs. Just waiting for the mail man.

 

[Igor]

Just waiting for the mail man.

??
Mail about-what? Maybe it gone to spam or not received. Can you please mail again?

 

[king-rb]

today i changed the bc177 to bc214 b. now i can callibrate the unit and everything is in specs! great compressor and stereo matching is really good. im now working on the perfect attack & release....
thanks to igor!

 

[Igor]

Please tell us more about BC177.

 

[Rybow]

Just waiting for the mail man.

??
Mail about-what? Maybe it gone to spam or not received. Can you please mail again?

For the PCB's. They arrived last week, so no more waiting! Your email arrived no problem. Thanks for passing along that file.

Just a quick question. Does anyone have a front panel designer file that they wouldn't mind sharing? I really don't want to mess up the control placement.

 

[king-rb]

the bc177 i ordered at Farnell "Coil BC 177C nx" is the writing on it. with this transistors the unit was working and sounding good but way out of specs..

 

[loopermc5]

Anyone one use anything beyond the standard fair for transformers? I'm getting ready to order mine figures id ask?

Thanks

 

[Rybow]

Most of the builds I've seen use Carnhill transformers. In fact, I have yet to see a build that used anything other than Carnhills. I would be interested to hear about if anyone has used another transformer type in their build. I know transformers are a huge part of the sound. So the "Neve" sound is in the Carnhills. I wonder what Lundahls or Cinemags would do in this circuit.

 

[king-rb]

The unit is working great now for two days ;-) But i have some concerns with the psu. The regulator gets really hot (after 30 minutes around 55^C) i useed on secondary of a 25V 2x0,6A Power Transformer. Should i use both secondarys in parallel so its 2x 0,6A or should this be no problem?

 

[haima]

you should be fine. the LM317 is rated to around 125°C AFAIK, and they also have thermal shut down protection.

but out of interest, what voltage do you measure on the input pin of the regulator? does the regulator have a nice big heatsink on it? where exactly did you measure the 55 degrees?

if anything, paralleling the secondaries of your power transformer might slightly increase the voltage at the regulator input due to less current being pulled thorough the transformer, i.e. less "sag". it might cool the transformer a bit if that's the problem. but you are talking about the regulator heating up, not the transformer... yes?

 

[king-rb]

thanks for this fast answer!
transformer is ice cold.
regulator heat messured direct on the regulator not on the heat sink.
i will add a much bigger heat sink to be save then.
voltage on the input pin of regulator is: 39,5V

 

[haima]

i think you'll be fine.

but if it worries you, up-size the heatsink or bond the regulator to the case - make sure you use insulating washers + thermal paste, or those rubbery adhesive insulators that do the job of both.

anyway, glad to hear your compressor's working  8) post some pictures or samples!

mine's almost done - i'll probably be running some audio through it this weekend... then i need to get a nice case happening!

 

[Igor]

Just a quick question. Does anyone have a front panel designer file that they wouldn't mind sharing? I really don't want to mess up the control placement.

Feel free to mail about .cdr (Corel) files. It is possible to take the PCB dimensions
in .ps or .plt than import them into FPD. Check for conversion units, BTW, sometimes PLT
converted as 1000 and not 1016 units.

the bc177 i ordered at Farnell "Coil BC 177C nx" is the writing on it. with this transistors the unit was working and sounding good but way out of specs..

Hm... Strange. I used NOS BC179 in one unit, worked fine.

Anyone one use anything beyond the standard fair for transformers?

Me
TF10015/16, my outputs (Hi-B, gaped C-core).
Gave an attempt to wound input/interstage on DU2023 lams, 84% Ni,
loved them more for sound than 31267+Carenhill interstage.
Too many time investment, but worth this.
Less disrorted low-mid, still huge sound. Again, all these sound talks is matter of taste.

Input/interstage transformers IMHO better to wound on DU or UI laminations
(two symmetric coils), copper shield between windings must. Some trunny' woodoo as well
TF100XX are wound on EI laminations, BUT for me, sounded good.

The unit is working great now for two days ;-)

HURRAY!!!!!

But i have some concerns with the psu. The regulator gets really hot (after 30 minutes around 55^C) i useed on secondary of a 25V 2x0,6A Power Transformer. Should i use both secondarys in parallel so its 2x 0,6A or should this be no problem?

Use bigger heatsink, as it was suggested. 40-50deg C is OK.
The windings are in parallel or one half is used, but not series connection.
Yes, right, see it from your later post

if anything, paralleling the secondaries of your power transformer might slightly increase the voltage at the regulator input due to less current being pulled thorough the transformer, i.e. less "sag". it might cool the transformer a bit if that's the problem. but you are talking about the regulator heating up, not the transformer... yes?

Just...my $0.02, paralleling the windings is better for transformer. Less power going to heat etc.

i will add a much bigger heat sink to be save then.
voltage on the input pin of regulator is: 39,5V

Absolutely fine.

mine's almost done - i'll probably be running some audio through it this weekend... then i need to get a nice case happening!

Yummmm... Again, feel free to mail about .cdr file.

 

[ultra-alex]

mine's almost done - i'll probably be running some audio through it this weekend... then i need to get a nice case happening!

keep it coming.  ;D
i started my second unit today.
cheers, alex

Just a quick question. Does anyone have a front panel designer file that they wouldn't mind sharing? I really don't want to mess up the control placement.

i have a .fpd file kindly translated by frank (frontpanels.de) from igors corel file. email me if interested. of course you have to tweak it for your taste, as i think my idea of frontpanel style is different... at least that´s what my discussions with frank shows.  ;D