MyRefC build guide - Page 96

Milos P. · 10th April 2012, 07:33 PM

Thank you. I'll google for the "howland current pump". I'll just order 0.5R caddocks.
Best

Milos P. · 28th May 2012, 05:19 PM

I made MyRefC, DC coupled, a couple of days ago, sounds great, thanks to everyone who took the part in development of this very nice amp.
What is the best solution to make it unity gain or close to unity (don't need much gain from it my preamp delivers a lot of gain)?
Thank you

AndrewT · 28th May 2012, 08:25 PM

You can't reduce to unity gain.
Throw away your pre-amp.

Milos P. · 29th May 2012, 07:24 AM

"Throw away your pre-amp."
That is easy enough, thank you

.
I just realized that I asked the question, a wrong way.
What is the best value for the input pot, bearing in mind that my amp is DC coupled?
I see the values of 10k - 22k- 50k- 100k mentioned, but could not find any data DC coupled design specific. I think 100k is obvious choice but wanted to hear another opinion.
Thank you

AndrewT · 29th May 2012, 09:25 AM

10k is the obvious choice. The others are options to allow poorly designed Sources to drive the vol pot.

Milos P. · 29th May 2012, 10:44 AM

Thank you. R13(100k) to be taken out now ?

Milos P. · 9th June 2012, 02:05 PM

Hi
After about a week of good sound and no problems at all from the first power on, my amp developed strange sibilance effect. I use audio grade parts, like PRP,Takman, Nichicon etc. Tried to increase C9 to 1000uF(C1 2.2uF/ R13 100k) and a different capmaker, but sibilance stayed.
Now, one channel does not work (relay will not click) and I killed 3pcs of LM 318 so far.
If I take out LM 318 there are no voltages on its socket pins apart from +/-12VDC(pin4 -vdc, pin7+vdc) as it should be. With 318 taken out amp will power on relay will click and there is no DC on the output. If I put LM 318 in the socket there will be various +/- voltages around 12V on all of it's pins that are used and there is ~-25VDC at the output pin of the 3886.
No smoke, no heat, at all. I made a simple circuit on the proto board and it showed me that any 318 is dead after I put it in the socket and power on the amp. I'm not sure if 3886 is dead I can't see anything wrong with the voltages its showing with 318 taken out (no DC on the output).Only thing that is strange, its mute pin is getting less than a volt. I've spent several hours staring at the board, no shorts, wrong value parts, lifted pads etc- the amp was working about 10 hours per a day, moderate power, for a week or so- hard that I misswired something. I use TF chip with HUGE HS. Any ideas? Dead 3886?
Thank you

AndrewT · 9th June 2012, 02:08 PM

Could the 3886 be Fake? If it has failed, it could take out the 318.

Milos P. · 9th June 2012, 02:13 PM

Quote:

Originally Posted by AndrewT

Could the 3886 be Fake? If it has failed, it could take out the 318.

I doubt very much, it is from farnell or DK can't remember.

Milos P. · 9th June 2012, 02:17 PM

Strange thing is that amp powerd on with 1000uF installed, I listened to it for about 15min.
to make sure if sibilance is gone or not, powerd it off to put it back in it's place switched it on but only one ch. came alive.

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10th April 2012, 07:33 PM	#951
Milos P. diyAudio Member Join Date: Mar 2008 Location: Belgrade	Thank you. I'll google for the "howland current pump". I'll just order 0.5R caddocks. Best

28th May 2012, 05:19 PM	#952
Milos P. diyAudio Member Join Date: Mar 2008 Location: Belgrade	I made MyRefC, DC coupled, a couple of days ago, sounds great, thanks to everyone who took the part in development of this very nice amp. What is the best solution to make it unity gain or close to unity (don't need much gain from it my preamp delivers a lot of gain)? Thank you

28th May 2012, 08:25 PM	#953
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	You can't reduce to unity gain. Throw away your pre-amp.

29th May 2012, 07:24 AM	#954
Milos P. diyAudio Member Join Date: Mar 2008 Location: Belgrade	"Throw away your pre-amp." That is easy enough, thank you . I just realized that I asked the question, a wrong way. What is the best value for the input pot, bearing in mind that my amp is DC coupled? I see the values of 10k - 22k- 50k- 100k mentioned, but could not find any data DC coupled design specific. I think 100k is obvious choice but wanted to hear another opinion. Thank you

29th May 2012, 09:25 AM	#955
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	10k is the obvious choice. The others are options to allow poorly designed Sources to drive the vol pot.

29th May 2012, 10:44 AM	#956
Milos P. diyAudio Member Join Date: Mar 2008 Location: Belgrade	Thank you. R13(100k) to be taken out now ?

9th June 2012, 02:05 PM	#957
Milos P. diyAudio Member Join Date: Mar 2008 Location: Belgrade	Hi After about a week of good sound and no problems at all from the first power on, my amp developed strange sibilance effect. I use audio grade parts, like PRP,Takman, Nichicon etc. Tried to increase C9 to 1000uF(C1 2.2uF/ R13 100k) and a different capmaker, but sibilance stayed. Now, one channel does not work (relay will not click) and I killed 3pcs of LM 318 so far. If I take out LM 318 there are no voltages on its socket pins apart from +/-12VDC(pin4 -vdc, pin7+vdc) as it should be. With 318 taken out amp will power on relay will click and there is no DC on the output. If I put LM 318 in the socket there will be various +/- voltages around 12V on all of it's pins that are used and there is ~-25VDC at the output pin of the 3886. No smoke, no heat, at all. I made a simple circuit on the proto board and it showed me that any 318 is dead after I put it in the socket and power on the amp. I'm not sure if 3886 is dead I can't see anything wrong with the voltages its showing with 318 taken out (no DC on the output).Only thing that is strange, its mute pin is getting less than a volt. I've spent several hours staring at the board, no shorts, wrong value parts, lifted pads etc- the amp was working about 10 hours per a day, moderate power, for a week or so- hard that I misswired something. I use TF chip with HUGE HS. Any ideas? Dead 3886? Thank you

9th June 2012, 02:08 PM	#958
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Could the 3886 be Fake? If it has failed, it could take out the 318.

9th June 2012, 02:17 PM	#960
Milos P. diyAudio Member Join Date: Mar 2008 Location: Belgrade	Strange thing is that amp powerd on with 1000uF installed, I listened to it for about 15min. to make sure if sibilance is gone or not, powerd it off to put it back in it's place switched it on but only one ch. came alive.