Moskido - Hybrid Aikido/MOSFET amplifier

[cjkpkg]

OK, I am about to ask a really dumb question. The diagrams I have seen for all the various schematics seem to not be consistent for the Source and Drain connections.

Is the audio output supposed to be on the drain or the source?

[beau2317]

They all look consistent to me. Can you point out what you mean?

The output stage is a source follower, so the output is on the source.

[cjkpkg]

here's one for example...

I realize its the irfp version but here is another


and the original...for reference

[regal]

Has anyone scaled down the dc coupled schematic shown above for headphones, the biggest problem with the Aikido Hybrid headamp is the large electrolytic on the output, the above servo'ed scheme is a big step in the right direction.

[beau2317]

CJKPKG : I referenced the third schematic on page 1 of this thread. And it's consistent with my AC and DC coupled moskidos (and with actual reality). The first schematic is someone else's mistaken efforts and the second one is another Broskie design that doesn't bear much resemblence to the moskidos on this thread.

Unless you are an expert you're not advised to simply build things that John Broskie draws on his blog -- he often leaves things out and/or simplifies things.

[kacernator]

Originally Posted by regal

Has anyone scaled down the dc coupled schematic shown above for headphones, the biggest problem with the Aikido Hybrid headamp is the large electrolytic on the output, the above servo'ed scheme is a big step in the right direction.

I have 5W DC moskido. Sounds very good. But for headphones I recommend just aikido preamp cap-coupled to output transformer (10k/150 Ohm). Output transformer sounds best to me compared to SE or PP buffer. And also you can swap the phase easily back with output transformer, because aikido inverts the phase.

[cjkpkg]

OK

I need some help...I completed one channel and the aikido stage is all within spec voltages. I hooked up a test speaker and my ipod and with the ipod cranked all the way up it is barely audible.

The BUZ901 is still not getting warm at all but both source resistors are conducting. I only measure about 0.68A per resistor bank though. The BUZ906 gets really hot.

I would really just like to get the basic circuit going before I start modifying it.

[beau2317]

Are you using an Aikido PCB from John Broskie? What tubes are you using? Are you getting the same current through both source resistors? What voltage are you getting before the output capacitor (ie where the source resistors join). Is it half the supply voltage? Does the sound you get thru the speakers sound distorted?

Basically you need to break the problem in two. Is the Aikido part working? And Is the output stage working?

You could try driving the output stage directly with an iPod. You could try listening to the output from the aikido stage with some headphones.

[cjkpkg]

OK...

I dont feel so bad now since no one else caught the error in my schematic...I knew something had to be there...

But, Beau, to answer some of your questions...
-I am wiring the aikido front end P2P
-New issue Tung Sol 6sn7 and 6sl7
-Yes - same current
-Yes, now roughly half
-No distortion (however there is a buzz now I have to chase down coming from the Aikido section - once I clean up the wiring it should go away.)

So, now to the fun part...can anyone guess where the error is in my schematic? I'll give you guys a hint...and it does not have anything to do with differing values or the diode string(s)...


I discovered it when I went back through all the tubecad blogs about the moskido...


Thanks again for all your help guys! A little persistence and a lot of whining finally got to the bottom of it...

[beau2317]

cjkpkg : I don't know which schematic you are referring to. You have not drawn any that I can see before, just linked to copies.