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 Post subject: Moskido Amplifier
PostPosted: February 25th, 2019, 10:27 am 
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Joined: February 28th, 2013, 1:19 pm
Posts: 252
Just finished assembling a tube/MOSFET hybrid amp based on John Broskie & Bob Prangnell "Moskido" concept, using a 6CG7 gain stage, a 6N6P White cathode follower, cap coupled into a Pass Burning Amp complimentary output MOSFET source follower stage. I had originally considered an octal based tube front end (6SN7 + 6BX7), but did not have space or heater current for the 6BX7. This was a rebuild of my Pass First Watt F-4 clone (same chassis and LV power supply), but with new output/bias boards, mono HV B+ and heater supplies for each driver stage channel, and a point-to-point wired Aikido board.

I am still letting the amp settle in before pushing the bias hotter, but figure I should be getting around 30W Class A into 8 ohms, 60W Class A into 4 ohms. Hooked it up to speakers and a source this morning before work, and it plays music just fine! Planing to put it into the system in the next few days on the bass cabinets, but would like to listen to it full range with a pair of Aria 5R speakers to see how they sound together. These are 4 ohm speakers that really never worked well with SET amps.

David
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 Post subject: Re: Moskido Amplifier
PostPosted: February 26th, 2019, 9:29 am 
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Joined: March 12th, 2013, 11:12 am
Posts: 475
You got a lot squeezed in there! I don't remember hearing the 5Rs, how low do they go?


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 Post subject: Re: Moskido Amplifier
PostPosted: February 26th, 2019, 11:58 am 
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Joined: February 28th, 2013, 1:19 pm
Posts: 252
The Aria 5Rs go down to around 60Hz, as I recall. They are a 2-way D'Appolito design with a pair of Focal 5K013-L woofers and a Raven R-1 ribbon tweeter. Needs subwoofers (which of course I have). I did hook up the Aria 5R speakers to the amp, and on first listen, they seem to sound alot better than they did with a SET amp powering them. I remember finding that a PP amp (PP2A3) worked better with them than a SET 300B or even my GM70 SETs, but I think both were with the 8 ohm tap instead of 4 ohm. But this is with only 1 hour worth of playing down in the basement and not in the listening room, and near field besides. Need to let the amp cook a while longer to get the bias setting as hot as I dare (nice to finally have a temperature probe and an multi-meter that reads temperature).

David


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 Post subject: Re: Moskido Amplifier
PostPosted: March 6th, 2019, 10:58 am 
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Joined: February 28th, 2013, 1:19 pm
Posts: 252
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I have the Moskido amp in the listening room along with the Aria 5R speakers and subs. Although I originally intended the amplifier to drive a bass cabinet as part of the horn speaker setup of recent posting. I was curious on how it would do full range, particularly since it was sound so promising in the basement with just the Aria 5R close field. Overall sound is very clean, detailed, yet still having tube warmth. The speakers do disappear well, particularly if arranged so the tweeter is ear height, and the focal point is slightly in front of the listener. I had started with a GE 6CG7 in the voltage amplifier position, but found a Russian 6N1P seemed to give more life to the sound. Currently using a 1965 Novisibirsk 6N1P-B VI instead of the Svetlana version (Voshod?) of a more recent vintage (which I tried first).

I am still tuning the system, but the Aria 5Rs sound SO much better on this amp instead of tube amplifiers in the past. I am finding myself making excuses TO listen, rather than excuses NOT to listen (which, I am afraid, was the case with the horn setup). But this is probably due to novelty, so will see what happens in a few days or weeks when I start being bothered by a fault.

David


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 Post subject: Re: Moskido Amplifier
PostPosted: March 6th, 2019, 11:56 am 
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Joined: January 15th, 2015, 7:19 am
Posts: 788
Location: Baltimore MD
Wow that's a great looking room
would love to hear it too


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