For someone starting from scratch and not having read the F1 thru F5 articles (or built one), what is the VA or p/n of the Antek power transformer? The cinemag transformer? Which N JFET is everyone using and voltage/number of leds for bias?
Which F6 pcb are you using? That changes the answer to half your questions... This thread is for the diyAudio boards, which will use mosfet output transistors and Jensen transformer.
To specifically answer your questions, choose an Antek transformer of 300 or 400 va, 18 or 20 volt secondaries, and preferably shielded (AS series)
CineMag cmoq-4hpc
SemiSouth R100 power jfet
1 Blue LED for bias
To specifically answer your questions, choose an Antek transformer of 300 or 400 va, 18 or 20 volt secondaries, and preferably shielded (AS series)
CineMag cmoq-4hpc
SemiSouth R100 power jfet
1 Blue LED for bias
Hi Jim,
Do you know the required input jfet grade? What's the idss range?
Reason for asking is pricing of p channel and limited quantities of N channel of the diyaudio.com store.
Thanks
Vince
Do you know the required input jfet grade? What's the idss range?
Reason for asking is pricing of p channel and limited quantities of N channel of the diyaudio.com store.
Thanks
Vince
6.5 -11.5 or thereabouts. It's not as critical as you might think. Essentially all the Pass DIY designs are centered on Jfet Idss of 8.0, which (not surprisingly) is the center of the BL range.
It's still easiest to buy matched pair from Spencer at fetaudio.com
It's still easiest to buy matched pair from Spencer at fetaudio.com
Thanks for the tip.
I have a bunch of N ch but not many P ch.
Wanted more for the LSK preamp.
Thx
I have a bunch of N ch but not many P ch.
Wanted more for the LSK preamp.
Thx
As stated I'm starting from scratch, so no bds, no transformers, no case/heatsink but I do have IRFP240 Fets. Are the boards and input xfmrs available yet? Has anyone tried P2P, all my tube gear is built this way?
It's a simple enough circuit, point to point will probably work quite well. You'll need something (perfboard) to hold the input transformer, but other than that, it's all easy.
Give it a try. 🙂
Give it a try. 🙂
Video update!
http://youtu.be/5gUv57xrID0
(Please excuse the mess on my bench - I can never keep tools organized while working)
This is a +/-20V test at about 1.1A total current. (It's as high as my baby bench PSU will go...) Things look and sound great. I needed a bit more bias voltage, hence why the LED has been put in series with the zeners. For the record, the Vgs of the IRF240 is 4.65V
The other PCB will be tested soon, perhaps even today. Once both are found to be happy, I'll attach a real amp PSU.
http://youtu.be/5gUv57xrID0
(Please excuse the mess on my bench - I can never keep tools organized while working)
This is a +/-20V test at about 1.1A total current. (It's as high as my baby bench PSU will go...) Things look and sound great. I needed a bit more bias voltage, hence why the LED has been put in series with the zeners. For the record, the Vgs of the IRF240 is 4.65V
The other PCB will be tested soon, perhaps even today. Once both are found to be happy, I'll attach a real amp PSU.
Looking good Jim, I don't recall seeing any specs, do we know if its the standard 25watts per channel or ... ?
With that PSU? Nope. It's too small. I'm just making sure the PCB layout is operative.
This amp has 2 separate PCB, in order to keep the signal transformers all the way to the back and keep the output devices low on the heatsink. I'm checking both PCB at this time. That video is of the first board.
Once the other is assembled and tested, then I'll make a real amp PSU, assemble the stereo amplifier and get some measurements. With 24V rails and some real current capability it should easily make 25WPC 8ohm.
This amp has 2 separate PCB, in order to keep the signal transformers all the way to the back and keep the output devices low on the heatsink. I'm checking both PCB at this time. That video is of the first board.
Once the other is assembled and tested, then I'll make a real amp PSU, assemble the stereo amplifier and get some measurements. With 24V rails and some real current capability it should easily make 25WPC 8ohm.
I am going to use fqp19n20 for this amp? Should I change any values of resistors in the schematic? How's about the bias point?