Buy a PSU board from TeaBag. Simplify the PSU section, eliminating most of your internal wiring and complication. I have used this exact setup that I am recommending and it is no harder than an F5 to build. You must also make sure you haev valid components. This may have been discussed, but needs to be reiterated. I would only buy Jfets from one source. Spencer. Output fets are easier to come by and should not be a problem. You can do this, i tihnk you are just overcomplicating the process with the custom PSU, which also makes it difficult to help,as we are not working with a known standard.
It does look good. We really like the way you have the gain board between the output boards and are hoping to have holes in the new boards that will allow us to make that easy for those with the pre-drilled (UMS) heatsinks to do the same.
Considering im no electrician but that its just a fun hobby I think I Did pretty well
Cheers, well Ive been offered more money possibly will continue
So Im trying to find where those PSU boards are, guess ill message him direct.
BTW : when the amp blew i turned it on once and heard a tightening sound, then turned it off then back on same tightening sound then it sounded like it just snapped and saw some smoke, not on resistors anywhere it seems but from the Mosfets which all 4 seem dead in one go.
I understand you can tell whats going on better if Im using those Tea bags boards, cheers
So Im trying to find where those PSU boards are, guess ill message him direct.
BTW : when the amp blew i turned it on once and heard a tightening sound, then turned it off then back on same tightening sound then it sounded like it just snapped and saw some smoke, not on resistors anywhere it seems but from the Mosfets which all 4 seem dead in one go.
I understand you can tell whats going on better if Im using those Tea bags boards, cheers
Hi Buzz,
I dont know if its a problem. Still on experimental mode.
Turn On - I have about 50mv DC offset then after awhile it will drop to 30mv then after 5 to 10min will be stable on +/-1mv.
Turn off - I will have a DC offset swing of about 400mv at the speaker terminal.
Im using jfets from Spencer at 7.3ma. Im not yet using the FETS from yours.
My bad, I was not able to buy some extra Fets from you for experiment purposes.
Just trying to understand first the behavior at the terminal that will not damage my speaker in future.
Cheers.
I dont know if its a problem. Still on experimental mode.
Turn On - I have about 50mv DC offset then after awhile it will drop to 30mv then after 5 to 10min will be stable on +/-1mv.
Turn off - I will have a DC offset swing of about 400mv at the speaker terminal.
Im using jfets from Spencer at 7.3ma. Im not yet using the FETS from yours.
My bad, I was not able to buy some extra Fets from you for experiment purposes.
Just trying to understand first the behavior at the terminal that will not damage my speaker in future.
Cheers.
Hi Buzz,
Thanks for the input. Yes I can get a transformer that can deliver enough
current.
That means, I will go with 32V rails without cascode.
Next is the Heat Sinks, I mean Huge Heat Sinks...
Cheers.
I think what Buzz meant, you need a total bias of 1.8 amps or higher to supply the current for 100 watts peak Class A at that voltage. I believe 100 watts peak equates to 50 watts average class A power.
Rush
Hi Rush,
Thanks for the clarification.
Pardon me if my question might be offshoot...Does this mean I can reach 100W without going into clipping at same time with out leaving class A?
Whats bothering me about this power thing is I have currently an 80W Accuphase Class AB, thus I dont want to go the opposite direction reducing power.
However, looking on the economic side, Im highly considering also to go down
to 50W Class A instead of the 100W.
Cheers.
Hi Buzz,
Thanks will take note of these numbers.
With these bias level, what transformer rating per channel would you recommend without even having a slight hum.
Currently I have 400VA for V2 single channel, bias at 0.3V, there is already a slight hum....
For the Heat Sink, yes, we need pay respect to the heat that will be generated. With the current Heat Sink I have, I can visualize how huge
I need if I go with the recommended bias.
Cheers.
With rails of 32 volts, you may get 28 volts of swing, this gives you MAX 50 watts Class A with 100 watt peak. If you bought this amp it would be listed as a 50 watt amp. That is a lot of class A power, but less power than an 80 watt Accuphase class AB. You are lacking rail volts to get higher wattage. I suspect you will not notice any lack of power between the two amps, the class A may even sound more powerful due to better control, etc.
You would have to go to 44 volt rails to get to 100 watts average class A power and your total bias current would need to go up to 2.5 amps. That's a lot of heat for you to get rid of.
Rush