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Old 23rd March 2012, 11:16 AM   #11
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Quote:
Originally Posted by nullbyte View Post
Haha, sweet! Looking forward to seeing what else you do with it, the 10uF cap mod seems pretty great. What transformer do you think will work with a regular sized heatsink? I might have a larger one lying around too, so I might emulate your setup a little. Also, bought it!
Nice one, nullbyte.
I'd have been happier trying a 30/0/30 200va first; that might not have tripped-out the speaker-protect, but I'm happy with the sound at 35/0/35.
Let me know if you face any problems.

One last time, to be clear. Link across C18 to disable trip-latch-off, then take C19 up to 15uF to avoid triggering the speaker-protection circuit.

WORDS OF CAUTION. THESE ACTIONS MAY VOID YOUR WARRANTY!!!

But in my case, I don't care.
What I like is that I've got a piece of kit that now scares me before I break it.

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Old 23rd March 2012, 09:20 PM   #12
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Is that 30-0-30 ac and 35-0-35 ac?

If yes, the LM3886 and 4780 peek to peek is supposed to be maxed at 80Vdc max...

30Vac = +/- 42Vdc and 35Vac = +/- 50Vdc which would bring you to 84Vdc and 100Vdc respectively on 120Vac or 240Vac primaries...

I guess you're playing with fire here...

I bought a PCB and stuffed it myself. It is running two LM4780 with an X10 buffer. Sounds really good but the LM4780 seem to be oscillating since they get pretty hot quickly... And the heatsink is way adequate... I've been looking at the 4780 spec sheet on what to do in that case but have not implemented anything yet...

Here it is

Click the image to open in full size.

Click the image to open in full size.

Every single parts in there is good quality and sourced through Mouser. Digikey and Parts Connexion.

If anyone is interested in fixing it (I don't have time, too many projects right now), just PM me!

Ciao!
Do
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DACs : TPA Buffalo II + OPC's NTD1 I/V | TPA OPUS + IVY III | Moon 380D DSD Speakers : Jim Holtz Statements | Astasia SD | Tubasson Mark 2

Last edited by pinnocchio; 23rd March 2012 at 09:22 PM.
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Old 23rd March 2012, 09:37 PM   #13
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Quote:
Originally Posted by pinnocchio View Post
Is that 30-0-30 ac and 35-0-35 ac?

If yes, the LM3886 and 4780 peek to peek is supposed to be maxed at 80Vdc max...

30Vac = +/- 42Vdc and 35Vac = +/- 50Vdc which would bring you to 84Vdc and 100Vdc respectively on 120Vac or 240Vac primaries...

I guess you're playing with fire here...

I bought a PCB and stuffed it myself. It is running two LM4780 with an X10 buffer. Sounds really good but the LM4780 seem to be oscillating since they get pretty hot quickly... And the heatsink is way adequate... I've been looking at the 4780 spec sheet on what to do in that case but have not implemented anything yet...

Here it is

Click the image to open in full size.

Click the image to open in full size.

Every single parts in there is good quality and sourced through Mouser. Digikey and Parts Connexion.

If anyone is interested in fixing it (I don't have time, too many projects right now), just PM me!

Ciao!
Do
Sweet, seperate tube buffers, high power output stage... whats not to like?
I think my meter is an auto-RMS; the DC is 35 across the caps!
And is yours oscillating, or are they passing Res-Cap-drained-rectified-DC?
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Old 23rd March 2012, 11:04 PM   #14
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"I guess you're playing with fire here... "

Um, yeah, that's my job.
Give me an envelope...

Last edited by copperweed; 23rd March 2012 at 11:18 PM.
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Old 23rd March 2012, 11:47 PM   #15
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Hey copperweed,

I'm not getting the last part of this

Quote:
And is yours oscillating, or are they passing Res-Cap-drained-rectified-DC?
Thanks!
Do
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PREAMPs : AMB α10 + JC-80 clone | Balanced DCB1 | LDR3x | AMPs: AMB β24 | Aleph 5 | FirstOne | ML-2 | TSSA | Telos 390 Clone | My_Ref FE
DACs : TPA Buffalo II + OPC's NTD1 I/V | TPA OPUS + IVY III | Moon 380D DSD Speakers : Jim Holtz Statements | Astasia SD | Tubasson Mark 2
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Old 24th March 2012, 01:47 AM   #16
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Quote:
Originally Posted by copperweed View Post
"I guess you're playing with fire here... "

Um, yeah, that's my job.
Give me an envelope...
Hi copperweed,

Not familiar with that expression... Sorry if I have insulted you.

Do
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Old 3rd April 2012, 08:32 PM   #17
Pemo is offline Pemo  Mexico
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Hi Copperweed, what do you think about the PSU is it enough. Are the caps big enough?

RGDS

PEMO
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Old 3rd April 2012, 09:27 PM   #18
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Originally Posted by pinnocchio View Post
Hi copperweed,

Not familiar with that expression... Sorry if I have insulted you.

Do
Not insulted at all. I admit I was pushing the SOAR envelopes of the chips. I'd be happier if it was 30/0/30 volts.
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Old 3rd April 2012, 09:42 PM   #19
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Originally Posted by pinnocchio View Post
Hey copperweed,

I'm not getting the last part of this



Thanks!
Do
Sometimes, if the output stage has gone short-circuit, it can sound like it's oscillating at 50 or 60 Hz. The power has been transformered, rectified and smoothed, but then, if the smoothing caps are shorted to ground through the speakers, it can sound like a full-power oscillation. I need to know aprox frequency to be sure. Whistling or whining could be osc., but loud buzzing could be a blown chip.
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Old 3rd April 2012, 09:56 PM   #20
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Originally Posted by Pemo View Post
Hi Copperweed, what do you think about the PSU is it enough. Are the caps big enough?

RGDS

PEMO
Hi Pemo.
When it's loud (like, 75/80wpch), there is some compression, but if I had a regulated 30/0/30Vdc PSU @ 10A, or even 35/0/35 @ 10A, instead of a Tx on the end of the supply chain then I'd be a lot more satisfied.
You just CAN'T HAVE too much power supply...
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