Balance in CCS Long Tailed Pairs - Page 4

planet10 · 31st January 2010, 07:43 AM

Quote:

Originally Posted by Geek

It's what Planet10 has in his living room now.

Indeed

And thourougly enjoying it.

Next i gotta get Duo to stop MooseFET from being MooseFART. Manual change of inputs is a bit of a pain, and daunting for all but me (or i could get off my butt, put 6H23pi in Fornaco and use it. MooseFET is cuter thou.

dave

Geek · 31st January 2010, 07:49 AM

Quote:

Next i gotta get Duo to stop MooseFET from being MooseFART.

It's under lifetime warranty for you, Dave... I'll do it.

All he has to do is pull the muting transistors with vise grips and done!

That's the **only** diff between yours and mine (besides the PS) and since I can't duplicate it on mine, it has to be it.

Cheers!

Duo · 31st January 2010, 10:35 AM

The Vreg still sucks...

Geek · 31st January 2010, 11:24 AM

The Vreg is straight off the National datasheet... blame them

Cheers!

Duo · 31st January 2010, 11:26 AM

With that big cap slugging the feedback loop down?

Geek · 11:32 AM

What big cap?... 10uF to ground after the 317 is nominal

You looking at the main filters?

The 10uF across the Vadj resistors? Nominal too (page 9, LM117 DS).

Cheers!

Duo · 31st January 2010, 11:30 AM

Can you show me the schematic for moosefet? Maybe email it to me?

Geek · 31st January 2010, 11:35 AM

Done!

Duo · 31st January 2010, 11:56 AM

I don't think the mute circuit is causing the problem. The exhibited sound was a hum, 120Hz, which occurred during brownouts as the line voltage rose back to normal. This is normally indicative of regulator dropout. Are you certain the transformer voltages are as listed in the schematic? I notice you list 30V after the rectifier but you have 15VAC and 12VAC being stuck in series after rectification which should be more like 38V.

The only beef I have with the 10uF cap on the FB loop node is that the response of the regulator to load changes is going to be on the order of 2ms although I don't think it would cause the problem we're experiencing.

As for the mute circuit, a pull-down on the bases of those transistors might be a good idea just in case. A far better mute would be implemented with a mercury wetted reed relay or JFETs (if the circuit impedance isn't too low).

Geek · 31st January 2010, 12:22 PM

I think we've drifted wayyy OT...

No relay for this particular model. Wetted relay would be more than the entire unit anyway. FFT didn't show issues with the bipolar.

FET, sure!

Maybe there's a bum cap or the reg's borked

Vin-Vo should be within the regs ability...

(I'm sure SY or Dave can split us off into our own MooseFET topic)

Cheers!

31st January 2010, 11:29 AM	#36
Geek diyAudio Member Join Date: Sep 2004	What big cap?... 10uF to ground after the 317 is nominal You looking at the main filters? The 10uF across the Vadj resistors? Nominal too (page 9, LM117 DS). Cheers! Last edited by Geek; 31st January 2010 at 11:32 AM.

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31st January 2010, 10:35 AM	#33
Duo diyAudio Member Join Date: Jun 2002 Location: Victoria, BC, Canada	The Vreg still sucks...

31st January 2010, 11:24 AM	#34
Geek diyAudio Member Join Date: Sep 2004	The Vreg is straight off the National datasheet... blame them Cheers!

31st January 2010, 11:26 AM	#35
Duo diyAudio Member Join Date: Jun 2002 Location: Victoria, BC, Canada	With that big cap slugging the feedback loop down?

31st January 2010, 11:30 AM	#37
Duo diyAudio Member Join Date: Jun 2002 Location: Victoria, BC, Canada	Can you show me the schematic for moosefet? Maybe email it to me?

31st January 2010, 11:35 AM	#38
Geek diyAudio Member Join Date: Sep 2004	Done!

31st January 2010, 11:56 AM	#39
Duo diyAudio Member Join Date: Jun 2002 Location: Victoria, BC, Canada	I don't think the mute circuit is causing the problem. The exhibited sound was a hum, 120Hz, which occurred during brownouts as the line voltage rose back to normal. This is normally indicative of regulator dropout. Are you certain the transformer voltages are as listed in the schematic? I notice you list 30V after the rectifier but you have 15VAC and 12VAC being stuck in series after rectification which should be more like 38V. The only beef I have with the 10uF cap on the FB loop node is that the response of the regulator to load changes is going to be on the order of 2ms although I don't think it would cause the problem we're experiencing. As for the mute circuit, a pull-down on the bases of those transistors might be a good idea just in case. A far better mute would be implemented with a mercury wetted reed relay or JFETs (if the circuit impedance isn't too low).

31st January 2010, 12:22 PM	#40
Geek diyAudio Member Join Date: Sep 2004	I think we've drifted wayyy OT... No relay for this particular model. Wetted relay would be more than the entire unit anyway. FFT didn't show issues with the bipolar. FET, sure! Maybe there's a bum cap or the reg's borked Vin-Vo should be within the regs ability... (I'm sure SY or Dave can split us off into our own MooseFET topic) Cheers!

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