API 312 Thread!

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Hi Rob, here's another thread with some opamp tweaks, if you need to do more troubleshooting (hopefully not):

http://www.groupdiy.com/index.php?topic=4796&postdays=0&postorder=asc&highlight=sound+2%2A5%2A2%2A0&start=75

... i think Fabio recently changed a few values on parts list due to the thread... hope this helps, Paul
 
hi Rob:

I just read through that thread, and it seemed that the main change for the Melcor was to use C2=10p and R5=43K9. I'll be getting my parts order in today and I'll be finishing up 4 Melcors ASAP and get them in my API boards (they look so lonely just sitting there with no opamps in them). I think these values were based on simulation, as I didn't see any response by anyone who had made the changes. What values are you using?
 
Hey Greg,

R5 at 43K9 seems quite a jump from the 2K marked as R5 on Peter C's schem for the melcor... where u see this change?

Peesh
 
Hey Rob,

m-e-l-c-o-r--1-1-7-3 yes :)

I was referring to PeterC's layout tho (havnt seen/didn't know Bauman done one too)...
 
I have been using the layouts/components from Peter`s site.

I`ve just been messing with the Zobel network on this & have got the lump a bit smaller, but its still there. I`m fairly sure that its coming of the i/p transformers because if I inject the signal after that point I don`t suffer from it.

I have some serious treble roll off as well. I`m not really sure if the Parmeko transformers have no frequency response, or whether it the Zobel thing.

Will have to investigate further.
 
I noticed that the relay ground was kept seperate from the rail/48V ground on Fabio's PCB. I haven't actually used relays before, so I'm assuming they should be kept seperate. Is this correct?
 
alo
i`m connecting my boards,but now i have a doubt:in the main boards there is a connection named ground,which i supose it`s the ground of the circuit,that`s suposed to go to the chassis ground.am i rigth?
best regards
pedro
 
OK. Consider this being an experimentation report...

btw, Peter C. did the layout, those Melcor boards I´m sending are the same layout with wider tracks...

I just tried bench testing an API setup that I made using Fabio`s board design & the Melcor op amps. I have Sowter output & Parmeko input transformers.

If I feed a sine wave into it I`m getting a lump on part of the cycle.

Has anyone had this sort of thing happen ? Got any ideas ?

Is that the same lump that Fabio had?
I think he has some piccies on his 312 site
http://www.thediypill.phx.com.br/diy_api312.htm
Hafl way down the page - some sine wave oscillation

Rob Flinn
Click to expand...
-
Melcor really seems to need a bigger feedback cap that 2.5.2.0 amps. This makes the waveform look right :) IIRC I have seen some Melcor schemo where this cap was really bigger (maybe I saw 470pF ?)

Using the Profile out trafo here.


... i think Fabio recently changed a few values on parts list due to the thread... hope this helps, Paul
Click to expand...

-
In Melcor C2=10 pF. We found out that this is also good in 2.5.2.0 so...
Remember C1=1000pF, not 630pF. I read somewhere that maybe raise R2 to 220R or so (?) can help (at least on 2.5.2.0).

I noticed that the relay ground was kept seperate from the rail/48V ground on Fabio's PCB. I haven't actually used relays before, so I'm assuming they should be kept seperate. Is this correct?
Click to expand...
-
Greg, I did this because I believe it´s better to joining all those grounds at the PSU. How better is it? I dunno yet :)

You can try to connect it locally with the amp GND, sure. They are all the same at the PSU...

One more thing... when the relays switch on, R10 gets REALLY hot. Has anyone else experienced this?
Click to expand...

-
Are you getting as input the juction between R1/C1 or the original spot?
I think if you´re getting from R1/C1 you don´t need R10.

i`m connecting my boards,but now i have a doubt:in the main boards there is a connection named ground,which i supose it`s the ground of the circuit,that`s suposed to go to the chassis ground.am i rigth?
best regards
pedro
Click to expand...
-

The GND spot between the transformers? Is the analog ground.
I´m using just the GND on the power connector at right, and all the ground will join in the PSU...


what fuse value to four channels?
best regards
pedro
Click to expand...

I use 1A for a 35VA power trafo...

:sam:
Fabio
 
Another question... not using relays here...
Saw relay layout on DiyPill, but in Portugese... to be sure...

'Pos A = closed'
'Pos B = open'
'Wire in pairs 1&2, 3&4, 5&6...'
 
alo
The GND spot between the transformers? Is the analog ground.
I´m using just the GND on the power connector at right, and all the ground will join in the PSU...
sorry fabio,but i don`t get it.
also,how did you grounded the xlr`s?.
pin 1-chassis
pin2-hot
pin3-cold
best regards
pedro
 
Melcor really seems to need a bigger feedback cap that 2.5.2.0 amps.

Can you specify exactly which cap you are talking about here please.
Click to expand...

Rob, C5 in this schemo:
http://www.thediypill.phx.com.br/forumfiles/R312sch_rev3.pdf

Paul, I ground Pin 1 on the chassis.

:thumb:
 

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