API 312 Thread!

[AnalogPackrat]

[quote author="smallbutfine"]It would lower the pop but should not be optimal however... Fighting with a similar problem with lorlins at my greens. I will definately order shorted types to get rid of that...[/quote]

Thanks for the help. I guess I'll be ordering a couple of shorting CTS switches from Digikey (I was planning on flying leads to the switch anyway). In the meantime I might try the nonshorting with large parallel resistor just to hear how bad the pop is.

A P

 

[Zee1usa]

[quote author="Greg"]I did the mod suggested by JLM. Read back... I think it's in here somewhere. I also added diode protection to the 5V regulator.[/quote]



Greg,

what diodes and what did you do to add this diode protection to the 5V regulator?

Thanks,


z

 

[Zee1usa]

FYI:

Greg said: "Take a quick look at the schematic Fabio posted for the PSU. It's the same two diodes he for protection on the other regulators. I'm not exactly sure why he didn't put them on the 5V. You can also look at the JLM Audio website and Joe posted the schematic for his power supplies. He also uses two diodes on each regulator for protection... just for additional reference. "

Hope this helps.

_________________
Greg Stein




Thanks Greg !

z

 

[Tungstengruvsten]

anyone here think of a reason I couldn't use a 4pdt switch and switch the whole output stage after the opamp/at the xlr between servo/tranny? might mean another 4-8" of leads but I haven't been able to think of a reason not to try it yet....

 

[DAN_000]

I noticed some noise (humm) when relays are working. This noise is anyway below opamp noise but I like to ask if anybody noticed the same thing.
There is more humm if you activate more relays.

anyone ?

 

[Zee1usa]

[quote author="Greg"]Fabio: I also have problems at low gains with the Melcor 1731. I usually have my gain very high so it's not a huge problem. Sorry to make you repeat yourself, but I think might have missed the talk about changing the feedback cap with the Melcor. So you added a 100pF cap in parallel with the existing 120pF... ie 220pF now? Did this help out with the stability issue?[/quote]


Greg,

Did adding this cap fix your oscillation issue?

I seem to be experiencing this too at low gain. I gotta check to see if I need to add this extra capacitance.

z

 

[Xopek]

Hello, gentlemen!
I build my variant API 312 (without the output transformer, at us they cannot be got ) and at me have arisen a pair of questions...
Probably, they were discussed here, but I badly know English what to analyze the information from this forum in such volumes...
So:
1. I use the relay on 12V, PSU from Fabio... at him the relay on 5V... As I understand, I should change 7805 on 7812, and replace R10 and R11... what about values at them (R10, R11)?
2. I use OEP input transformer ... What values RL, RC, CC should be?
Actually all.
Thanks for your attention.
:guinness:

 

[Bauman]

Hello Xopek,

Well after trying some different values RL=27k sounds cool. RC = 21k and CC = 800pf according to Chrissugar (right?).

R11 is 5k1 and R10 is not used. Just use a 7812 and connect its input pin to the junction of R1/C1.

Which opamp are you trying. I like Melcor with OEP :wink:

:guinness:
Fabio

 

[DAN_000]

No more problems here, the problem was the power trafo are a little close to boards.
0% humm now.

Epoxy time right now...

 

[kdawg]

Should Cinemag CMOQ-2S output be wired as 1:2 or 1:1 for Bauman's v3? And if it's 1:2, do you parallel the secondaries, or just one one set disconnected?

diypill is down again?
-kdawg :sad:

 

[Greg]

[quote author="Zee1usa"]Did adding this cap fix your oscillation issue?[/quote]
For me, it did not.

 

[Zee1usa]

[quote author="Greg"][quote author="Zee1usa"]Did adding this cap fix your oscillation issue?[/quote]
For me, it did not.[/quote]


Thanks !

I saw in the "Melcor Deconstructed" thread some possible mods that could potentially minimize some of the oscillation issues. It seems to be an ongoing topic of discussion.

z

 

[Xopek]

Hello Xopek,

Well after trying some different values RL=27k sounds cool. RC = 21k and CC = 800pf according to Chrissugar (right?).

R11 is 5k1 and R10 is not used. Just use a 7812 and connect its input pin to the junction of R1/C1.

Which opamp are you trying. I like Melcor with OEP

Thanks Fabio!
A few my API PCB photos from your permission.

http://ft.fotoplenka.ru/ft/99/82/48299/111216/360f7141.jpg

http://ft.fotoplenka.ru/ft/99/82/48299/111216/008b1c13.jpg

 

[Xopek]

Still pair questions about 2520 (bc550-bc560)
They are represented in figure
For what these apertures in PCB are necessary?
TnX :guinness:

http://ft.fotoplenka.ru/ft/99/82/48299/111216/e335d244.jpg

 

[mick]

Hi there, This seems to be related to the previous post, I'm working on some of Fabio's BC opamp boards, I know there are some links that need to be put in but I can't find any information about how many or where they go, help anyone.

Mick

 

[Bauman]

Looks like I need to make a update on the 312 page to get the info we got here and organize, hard to find even for me

So... looking at this pic

http://ft.fotoplenka.ru/ft/99/82/48299/111216/e335d244.jpg

C5 is OK
V- link is OK
N1 I use to ground the opamp case
N2 and N3 dont have any use.

hope this help
:sam:
Fabio

 

[Jonkan]

Fabio,

have you potted the opamp to the case with expoxi or not? Is it running hot inside the case?

I have built a small copper case for my melcor opamp, but im afraid that they will get too hot, since i run my rails at +/-24.

What do u think?

And btw, where would be a good place to ground the case on a melcor opamp?

thanks!
/J

 

[Greg]

[quote author="Jonkan"]And btw, where would be a good place to ground the case on a melcor opamp?/J[/quote]
There's a ground pin on the opamp... how bout there?

 

[Bauman]

There's a ground pin on the opamp... how bout there?

Yep, there! That's what I do.

:guinness:
Fabio

 

[CJ]

Anybody know what this came out of?
I believe it's an API input, but different.
Thanks!