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Old 28th June 2008, 02:50 PM   #1
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Default Hi power Moskido with A/B output Bias

Hi Guys
Im looking for some ideas of making a Hi Power Hybrid amp. Since I need Hi Power, class A output biasing is out of the question.
I own a hafler DH-500 and the Aikido pc board that I wish to use.

1. Will the Aikido supply the output voltage to to bring the mos fet output stage to clipping. About 52 volts peak to peak.

2. Since the output stage will be run in class a/b I want to add some negitive feedback , but the amp would be inverting. What would be the best way to work this.

3. I am using a hafler dh-200 that is using a paralle 5687 driving the output with no feedback. I has some great qualitys at lower listening levels , but falls apart at higher levels. On the bench it measures less than 2.0% thd @ 100 WPC into 8 ohms.

4. You ask why does this guy need so much power.
I have magnepan MMG's . They need some power to get off the ground. Was using a diy afterburner that worked well with 30 wpc of tube power. This is a Whole new world . Both loud Speakes are fun to listen 2 but they do there magic in different ways.

Thanks for any Feedback.
Fred
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Old 10th August 2009, 02:54 PM   #2
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Freddymac,

Did you ever build that DH500 hybrid? I'd be interested in sharing this and the DH200 project information with you. I have two DH500s I'd been toying with the idea of doing the same thing to. Not sure about NFB, etc. A friend has a DH200 and is considering the same. We are in the same boat as you with Maggies.

Stuart
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Old 11th August 2009, 12:50 AM   #3
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I gave up on the thought of using the Aikido.
I am working on a tube driver stage that is non inverting and has good current for driving the mos-fets. It is a ground up amp.( Not built from a past amplifier)
As a past employee of hafler when they were in NJ I can give some updates to the pc-6 or pc 19 to let your amps open up .
Nothing more than reducing and flatning open loop responce and reducing Negivive feedback. Harry Klouse did not like it because it did raise distortion a little.
I also tried musical concepts pc boards in the DH-500 and while it does bass well it misses on the mids and top end where I needed it with the mags. Smooth but not transparent.
My current comprimize is a adcom gfa-555 mk 2.
It is OK but Not magical and it does not image very well compared to a good tube amp or hybrid for that matter.
As long as we are talking power and Magnepans have you done any updates to your x-overs? Peter Gunn of magnestand uses a revised SMG series design that will bring the sensitiviy up to 92 db @ 4 Ohms and sounds great. I like Peter Gunn as he follows his soul to the music and he is willing to share some of his design with the diy people.
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Old 11th August 2009, 12:54 PM   #4
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Freddymac,

Thanks for the input. Eventually, I will get around to building hardwood frames for my speakers, possibly as soon as this winter. I have upgraded the internal crossovers using flat conductor inductors, improved caps, eliminated fuses, Cardas 17.5 in multiple runs and much better connectors. I do biamp. I use a home built amp on a Citation II chassis for midrange treble; it provides ~80WPC and while it will eventually be replaced with either a multiple pair EL34 amp or an OTL, it is not my current weakest link.

Internal to the Citation, between drivers and output tubes, I have added switchable small value caps and resistors to provide -6dB/octave at ~360Hz so I can avoid going through an electronic crossover for the upper frequencies. The bass goes through a home built 18dB/octave low pass filter, then on to the DH500.

I bought two of the DH500s with the idea of each amp powering one bass panel per channel, since each panel is 8 ohms. So, while I will build a hybrid on at least one of the chassis, I expect to do it to both.

There was an Audio Amateur article in the early 90's if memory serves, about a hybrid built around a complex iniput stage using an EF86 and a couple of 12AU7s. The EF86 sounds wonderful, but I'd have to use anything but a 12AU7, perhaps a 6SN7/6FQ7. The output stage is pretty simple and uses the Hitachi laterals that are already in the DH500, just one less pair. This is the approach I've been contemplating for some time.

The power really is needed, although new frames with triangulated support may help, it's not going to get me to where I can listen with 100WPC, so I still will need a powerful amp for up to ~300Hz. And, unfortunately, there is enough output into the lower mids that amplifier quality is really obvious on the bass panels. Before I changed some internal wiring and the input coupling, feedback and a few other P/S caps, the 500 was so slow/mushy I thought it would never be useable.

Stuart
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Old 20th February 2010, 06:27 PM   #5
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Default DH200 Hybrid

Quote:
Originally Posted by freddymac406 View Post
Hi Guys
Im looking for some ideas of making a Hi Power Hybrid amp. Since I need Hi Power, class A output biasing is out of the question.
I own a hafler DH-500 and the Aikido pc board that I wish to use.

3. I am using a hafler dh-200 that is using a paralle 5687 driving the output with no feedback. I has some great qualitys at lower listening levels , but falls apart at higher levels. On the bench it measures less than 2.0% thd @ 100 WPC into 8 ohms.

Thanks for any Feedback.
Fred
Hey Fred

Am I hearing you correctly, you have built a tube front end for the DH200? If so can I get a schematic? Thx so much for any help you can provide as I have been thinking about doing this for some time and have several pairs of 5687's.
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Old 30th May 2013, 02:23 PM   #6
Zigis is offline Zigis  Latvia
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Does anyone built Moskido amp with IRFP240/9240 instead of original BUZ ?
How it sound, can it work with biasing like in this DD amp?
TUMOS, the MOSFET current amp modul with real Tube sound
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