DIY F2 clone - Page 41

Nelson Pass · 11th November 2011, 10:44 PM

It's always something.

Zen Mod · 11th November 2011, 10:58 PM

Quote:

Originally Posted by ZUM911

Found it, it was the C2 1uF bypass cap. Many thanks all.

Cheers
Rick

use a hammer on a bugger !

bluewater · 16th November 2011, 08:01 PM

Could I replace gate resistor of the Semi JFet with a 56ohm with out making any other adjustments besides the Pot adjustment?

generg · 16th November 2011, 08:29 PM

I think that is no problem!

bluewater · 17th November 2011, 04:15 PM

I think I was a little rude not introducing myself before asking for anything.
I've read a lot on the different forums on Diyaudio and try to contribute when I think I could be helpful. I have to say this is the
best hobby I've ever gotten into. I'm not a techie or even very smart but there is enough info on these forums where if anyone "really wanted" to achieve building one of Mr. Pass's kindly donated schematics it is truly achievable with in that persons capabilities. There is so much to learn and understand(this one might take a while) but the end result is very satisfying. I'm constantly browsing the sight and studying on what I would like to build next or just read. I'm very thankful to all who contribute to Diyaudio because with out this site I would have never had the confidence to get into this wonderful hobby. I don't talk much but I'm on here almost every day. I usually don't speak because if I do, it will most likely be questions and 99% of the time it has been ask already. Thank you in advanced for any help.

Eric

Tea-Bag · 17th November 2011, 08:18 PM

Eric,
What are your remaining questions?
Generg gave you a good answer. Gate resistor mod is okay.

bluewater · 10:18 PM

Oh! didn't realize... thank you generg and thank you Tea-Bag for pointing that out to me.
Well, the reason I am curious is I'm purchasing some naked vishay resistors from a gentleman on the swap meet. This would be my main reason why I wanted to know. Well since I'm here, would it be almost as critical to have quality resistors on R6, P1 and R4? I was also curious about turn-on thump. For my F5 I used thermistors on both the hot and neutral for turn-on surges(works great by the way). He mentions this in the Zen 5 article but would this work for the F2J? Thanks again

Tea-Bag · 17th November 2011, 11:37 PM

C4 will bias up the board slowly, so no turn on thump. I use a 27k uf panasonic cap.
I would say R3 and R6 are most critical.

wicked1 · 19th November 2011, 07:14 PM

Quote:

Originally Posted by Tea-Bag

I changed R4 to 3.32K, able to bias up to 16v.
I still settled for 12V, seem to agree with the heatsinks a bit more.

Hello,
Sorry to bring up an old post, but I just got out my old SemiSouth F2 amp and was checking things on it..

Basically, isn't the bias supposed to be exactly 1/2 the voltage of the amp? So, for me, I've got exactly 22v coming from the PS feeding the amp, and I've got my bias at 11v.
I thought it had to do w/ keeping the signal square and balanced.
Or, am I wrong, and the bias is only adjusting how hot we're running things, so a bit more, if the heatsinks can take it, might be better?
I'm wondering because I've got huge heatsinks, and can definitely run things hotter. The amp barely gets warm the way it is. I like the idea of running things hotter if it could help.
(I don't have test equipment for this, so I want to go for whatever is generally considered best practice)

Thanks

wicked1 · 18th December 2011, 06:02 PM

Bump, for above question. I let it go for a while 'cause I thought maybe it was just a dumb question.. but I re-read this thread and there is conflicting info it. One of the early pages says to do it the way I have it.. exactly 1/2 the input voltage (I usually work w/ tubes, so 1/2 b+).
But later in the thread there is talk about pushing it to run hotter, implying higher bias is better if your heatsinks can take it.
Which is it?

Thanks

16th November 2011, 08:29 PM	#404
generg diyAudio Member Join Date: Jul 2009 Location: Near Frankfurt	I think that is no problem! __________________ and the First Wtt is......a really First Class PSS Idea !

17th November 2011, 10:14 PM	#407
bluewater diyAudio Member Join Date: Apr 2009 Location: Seattle,WA	Oh! didn't realize... thank you generg and thank you Tea-Bag for pointing that out to me. Well, the reason I am curious is I'm purchasing some naked vishay resistors from a gentleman on the swap meet. This would be my main reason why I wanted to know. Well since I'm here, would it be almost as critical to have quality resistors on R6, P1 and R4? I was also curious about turn-on thump. For my F5 I used thermistors on both the hot and neutral for turn-on surges(works great by the way). He mentions this in the Zen 5 article but would this work for the F2J? Thanks again Last edited by bluewater; 17th November 2011 at 10:18 PM.

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11th November 2011, 10:44 PM	#401
Nelson Pass The one and only Join Date: Mar 2001	It's always something.

16th November 2011, 08:01 PM	#403
bluewater diyAudio Member Join Date: Apr 2009 Location: Seattle,WA	Could I replace gate resistor of the Semi JFet with a 56ohm with out making any other adjustments besides the Pot adjustment?

17th November 2011, 04:15 PM	#405
bluewater diyAudio Member Join Date: Apr 2009 Location: Seattle,WA	I think I was a little rude not introducing myself before asking for anything. I've read a lot on the different forums on Diyaudio and try to contribute when I think I could be helpful. I have to say this is the best hobby I've ever gotten into. I'm not a techie or even very smart but there is enough info on these forums where if anyone "really wanted" to achieve building one of Mr. Pass's kindly donated schematics it is truly achievable with in that persons capabilities. There is so much to learn and understand(this one might take a while) but the end result is very satisfying. I'm constantly browsing the sight and studying on what I would like to build next or just read. I'm very thankful to all who contribute to Diyaudio because with out this site I would have never had the confidence to get into this wonderful hobby. I don't talk much but I'm on here almost every day. I usually don't speak because if I do, it will most likely be questions and 99% of the time it has been ask already. Thank you in advanced for any help. Eric

17th November 2011, 08:18 PM	#406
Tea-Bag not politcally affiliated diyAudio Member Join Date: Feb 2006 Location: Kennebunk Blog Entries: 7	Eric, What are your remaining questions? Generg gave you a good answer. Gate resistor mod is okay.

17th November 2011, 11:37 PM	#408
Tea-Bag not politcally affiliated diyAudio Member Join Date: Feb 2006 Location: Kennebunk Blog Entries: 7	C4 will bias up the board slowly, so no turn on thump. I use a 27k uf panasonic cap. I would say R3 and R6 are most critical.

18th December 2011, 06:02 PM	#410
wicked1 diyAudio Member Join Date: Jan 2008	Bump, for above question. I let it go for a while 'cause I thought maybe it was just a dumb question.. but I re-read this thread and there is conflicting info it. One of the early pages says to do it the way I have it.. exactly 1/2 the input voltage (I usually work w/ tubes, so 1/2 b+). But later in the thread there is talk about pushing it to run hotter, implying higher bias is better if your heatsinks can take it. Which is it? Thanks