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 Post subject: Re: Moskido Amplifier
PostPosted: April 7th, 2019, 9:48 pm 
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Joined: April 22nd, 2013, 12:58 pm
Posts: 177
Thanks for the posts David. You always bring a good story to the boards..... :thumbup:

That amplifier-to-speaker interface is one of the toughest to predict. I've got electrostatics now and while they have a very flat impedance curve at ~ 6 ohms (until you hit about 10kHz... when it plummets), they definitely play hard to get with amplifier pairings. Glad to hear that you found a good match with your MOSkido.


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 Post subject: Re: Moskido Amplifier
PostPosted: April 8th, 2019, 10:31 am 
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Joined: February 28th, 2013, 1:19 pm
Posts: 264
Just following up from last night on a couple of points. You can use the F4 boards instead of the BACO boards, these have the bias circuit, but you need to bypass the JFet driver stage. I mention this since the DIYAudio Store is out of the BACO boards. They will likely reorder, but just in case they are still out.

Second, as a point of further experimentation. An Aikido/White Follower front end is just a convenient way of having a tube circuit with enough drive for the capacitive input of MOSFET source follower output. Any other tube circuit with a gain of around 25dB would work as well. I could easily see ditching the White Follower and using low mu power tubes, either SE or PP, with a 6SN7 voltage amp. Pay attention to noise and distortion in the design. You can get more current drive using a beefy power tube and stepdown transformer, avoiding the coupling cap, but with the MOSFET input load being so high (7Kohm), it might limit the stepdown ratio. There are all different ways of accomplishing a tube/MOSFet hybrid amp, and it is really convenient to use the source follower output boards based on the Pass First Watt series as a current amplifier (output transformer), and think of the rest of the amp as tube. Nice thing is, no phase splitters, just a simple two stage input section, the output of which can be either SE or SRPP (White Follower being a variant).

This opens up a lot of ideas.

David


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