PCBs
I beleive it's for everyone. Visit the Wiki for some further info on past boards look and feel. Price is determined by supply and demand. Peter Daniel has agreed to make the order if 50 sets are ordered, A set is a stereo pair. I am just trying to facilitate the Wiki to get the ball rolling for all that missed out on F3-F4 clone build. You can search this thread to get an idea on original pricing, look etc. I think they are nice boards. I have some of the original F4's PD boards built up.
http://www.diyaudio.com/forums/showthread.php?threadid=99351&goto=newpost
😀
Nrik said:
I beleive it's for everyone. Visit the Wiki for some further info on past boards look and feel. Price is determined by supply and demand. Peter Daniel has agreed to make the order if 50 sets are ordered, A set is a stereo pair. I am just trying to facilitate the Wiki to get the ball rolling for all that missed out on F3-F4 clone build. You can search this thread to get an idea on original pricing, look etc. I think they are nice boards. I have some of the original F4's PD boards built up.
http://www.diyaudio.com/forums/showthread.php?threadid=99351&goto=newpost
😀
OK, , this is as close to a double blind test as I could (accidently) do. A couple of days ago I was thinking how GOOD my F4 amps sounded.
I've been listening a lot, and really enjoying them. Last night I thought to myself "these REALLY sound better than at first! , maybe they had to break in or something.."
Then the headslapper moment: "Duh! I had set the bias higher a week ago and not listened to them right after -I went to bed as it was late, then had a lot of work hit for a couple of days.
So, I think it is an unbiased 😉 test- I had first set the bias so that the measurement was 200mV. setting them to 250mV really made a difference. Nelson said I could try 300mV but I think I need to add a copper spreader under the MOSFETS because the extremes of my heatsinks aren't that hot , but within 3" of the MOSFETS pretty hot - can only touch the sink there for 5 sec.
Mark
I've been listening a lot, and really enjoying them. Last night I thought to myself "these REALLY sound better than at first! , maybe they had to break in or something.."
Then the headslapper moment: "Duh! I had set the bias higher a week ago and not listened to them right after -I went to bed as it was late, then had a lot of work hit for a couple of days.
So, I think it is an unbiased 😉 test- I had first set the bias so that the measurement was 200mV. setting them to 250mV really made a difference. Nelson said I could try 300mV but I think I need to add a copper spreader under the MOSFETS because the extremes of my heatsinks aren't that hot , but within 3" of the MOSFETS pretty hot - can only touch the sink there for 5 sec.
Mark
Variac said:
Mark, this brings up an interesting point.
I have seen an older schematic that biases to 250mv, and the newer one to 200mv. I am not sure what the initial reasoning is for this, or if I missed the boat completely. I have run them at the higher bias on the bench for hours without any heat or stability issues.
Mike
I did it kind of backwards. I put a thermocouple into the thermal paste right next to the fet in the worst cooling location. I then adjusted the bias up until the temp was stable at about 50 deg c. I think I ended up at about 280mv 
I think I even saw some reference to 300mV occasionally in Nelson's writings. It's confusing.
Now I could still be fooling myself. We all know that "break-in" can mean "getting used to the sound" , but from my experience, I think that the DaveM approach is best- get them as high as your heatsinks will allow. I've never seen any reference to getting them above 300 mV so I wouldn't go over that!
Now I could still be fooling myself. We all know that "break-in" can mean "getting used to the sound" , but from my experience, I think that the DaveM approach is best- get them as high as your heatsinks will allow. I've never seen any reference to getting them above 300 mV so I wouldn't go over that!
Been running mine at 300mv for 3-4 hrs a night for almost 6 months without any problems. I have some ex-computer fans on the heatsinks. Temps are in the low 90s C.
Now that the cold weather is coming to NE, I like the heater effect!
Very happy with the sound.
Now that the cold weather is coming to NE, I like the heater effect!
Very happy with the sound.
Oops. Not 90 C!! Even I know that would be too high.
More like 110 F.
BTW, it was 120-125 F before the fans at 225 mv. The fans are slow turning and quiet and were used as a stopgap until the Group Buy heatsinks arrive.
More like 110 F.
BTW, it was 120-125 F before the fans at 225 mv. The fans are slow turning and quiet and were used as a stopgap until the Group Buy heatsinks arrive.
Big Bias on F4
Maybe we can take this in slightly different way.
I am sure it's been discussed before.
With the Peter Daniel boards and closer PowerFets, what's the desireable FET temp, Sink Temp near FET, and the grab the outside of the sink temp? I generally get 65c on Fets, 60c between FETs and 50c on outside of heatsink fins with my temp probe @ 225mv. I wouldn't mind a discussion on reasonable limits here for all these measurements points.😕
Maybe we can take this in slightly different way.
I am sure it's been discussed before.
With the Peter Daniel boards and closer PowerFets, what's the desireable FET temp, Sink Temp near FET, and the grab the outside of the sink temp? I generally get 65c on Fets, 60c between FETs and 50c on outside of heatsink fins with my temp probe @ 225mv. I wouldn't mind a discussion on reasonable limits here for all these measurements points.😕
As I recall, Nelson mentioned that 50 C was the target temp to shoot for. If that is the case and my memory is correct. I would assume that you want to see 50 C at the devices. Of course you can run hotter than that, but you will likely see reduced fet life.
My F4 is ~45C with Peter's boards on the big Conrad heatsinks at 250mv and sounds terrific at that level. I could probably go higher without problems but it seems fine right where it is.
Oooohhhh!!!! That means I can likely get up to 300 mV of bias. Now I just need to get the smoke back into them that I let out this weekend.😱
DaveM said:
just curious, how do FETs die? short or open, or...... if it's a quiet death, why not run 'em hard and replace them when the go?
Let's see. I have never lost a JFET.
Come to think of it, I have never lost a tube.
I hardly ever lose a Mosfet, but their deaths are usually pretty quiet
if you have an AC line fuse. Over the years there have been a few
speaker drivers lost, small in proportion to the Mosfet failures, and
quite small compared to the not-failed Mosfets in product we have
made.
😎
Come to think of it, I have never lost a tube.
I hardly ever lose a Mosfet, but their deaths are usually pretty quiet
if you have an AC line fuse. Over the years there have been a few
speaker drivers lost, small in proportion to the Mosfet failures, and
quite small compared to the not-failed Mosfets in product we have
made.
😎
Did some measurements last night.
Ambient temp 12-13 C.
Heatsink 28-30 C.
Fets (on Peter Daniels boards) 33 C.
Bias is at 310 mv.
This is using 8.5 x 11 "ebay" heatsinks with 1 slow computer fan on each sink.
Cold NE weather giving me effective cooling it seems.
Should I be concerned and lower the bias? Its been rock solid for months.
Ambient temp 12-13 C.
Heatsink 28-30 C.
Fets (on Peter Daniels boards) 33 C.
Bias is at 310 mv.
This is using 8.5 x 11 "ebay" heatsinks with 1 slow computer fan on each sink.
Cold NE weather giving me effective cooling it seems.
Should I be concerned and lower the bias? Its been rock solid for months.
Nelson Pass said:
As the line from H.M.S. Pinafore goes:
"Never, well hardly ever"
I guess you missed the excitement of ham radio.
Nelson Pass
I finally have the funds to purchase a few tubes of Fairchild fet's for my F4, Could you please comment on the part number which won't exhibit the distortion as mentioned before.
Thank you
Nelson Pass said:
I finally have the funds to purchase a few tubes of Fairchild fet's for my F4, Could you please comment on the part number which won't exhibit the distortion as mentioned before.
Thank you
Guys,
I received all the parts for my F4 last couple days and have every single parts checked today. I got the PL431 instead of TL431. Are they the same? or otherwise I return them.
Thanks
Albert
I received all the parts for my F4 last couple days and have every single parts checked today. I got the PL431 instead of TL431. Are they the same? or otherwise I return them.
Thanks
Albert
