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Old 25th June 2007, 03:12 PM   #1
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Default The Aikido or Moskido??

I've been seriously thinking of building one of these. The schematic on glassware for the aikido says its a 13 watt amp. I know tube amps are much different then solid state when it comes to wattage. But my question is will it be enough to power something like a DIY MTM? Like the Natalie P's or the Statements which are a larger WMTMW with a Fountek ribbon tweeter. Do you think it would be better to use the Moskido. I'm not sure what kind of power output the Moskido has though. In the thread the he says it disipates about 130watts. Does that meant it outputs 130 watts?

Another thing I was wondering is if someone had BOM (bill of materials) for the Moskido. I didn't really see where it said what mosfets it used and what not or what extra parts over the Aikido it uses.

Thanks in advance for any help.
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Old 25th June 2007, 03:29 PM   #2
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Ok just looked again and the schematic on the glassware site is the Hybrid amp and it says it does 16watts (thought it said 13) so what does the basic Aikido amp output? Honestly it doesn't matter I just want to know if it will drive larger speakers to 80-90db?
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Old 25th June 2007, 05:33 PM   #3
Klimon is offline Klimon  Belgium
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The aikido is a preamp and needs a dedicated power amp to make music. I quickly checked the moskido; power dissipation is said to be 130watt/channel; actual output power will be only part of this. The author speaks about powering esl's so my guess is you'll have around 50 watts or more.

Simon
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Old 25th June 2007, 06:45 PM   #4
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This is what I'm referring to. http://glass-ware.stores.yahoo.net/aikampocboar.html
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Old 25th June 2007, 07:25 PM   #5
Klimon is offline Klimon  Belgium
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Although it's called an 'amplifier' in those pages, it actually is a pre-amp (even on first sight: no output transformers, only small-signal tubes etcetera). If you're still not sure; build one and connect it to your speakers. If that doesn't work out well, no loss, you can still use it as a preamp

Simon
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Old 25th June 2007, 07:27 PM   #6
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Long story short - the Moskido is a mosfet amplifier using an Akido circuit as the front end.
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Old 25th June 2007, 08:07 PM   #7
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I've built a couple of Aikido-based amplifiers. The Aikido is a preamp, that is, it takes a low-level high-impedance (10k) input signal and multiplies the voltage. The 6SN7 design I am using provides about x10 voltage multiplier (gain). I'm using a 300V power supply, so the output swings can be large.

I also use the 6SN7 as the second valve (V2) and the output impedance is around 600 Ohms. This will only provide milliwatts if you connect it to loudspeakers, and it probably won't sound too good. It's even a bit too low for headphones. It has plenty of output voltage, but it needs more "oomph" (expressed as lower output impedance or high output current).

However, a 600 Ohm output impedance is plenty to push a bigger output triode's grid (such as a 300B SET amplifier), an interstage transformer (for either SET or push-pull amplifiers), a MOSFET's gate (a Pass Zen or source-follower), or a solid-state push-pull output stage.

With the beefy output stage providing the hefty current and the Aikido providing the voltage gain, this makes a good combination.

I'm using an Aikido driving a MOSFET source follower for my amplifier now, into the Triangle Acoustics Solis.
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Old 26th June 2007, 02:46 AM   #8
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I thought I would give a recap of a few things, to make this Aikido/Moskido thing more understandable.

John's original post gave two designs, one a push pull, the other a single ended. Both are power amplfiers which comprise an Aikido voltage amp stage with a mosfet current amp.

The push pull design was rated at 16W (into 8 ohms) and ran at about 1 amp standing current.

The SE design, which is half as efficient, was also rated at 16W, but ran 2A standing current.

My friend built the PP design, and we were amazed at the sound quality.

I corresponded with John on the subject, and he suggested building a more powerful version with paralleled output devices and a higher rail voltage. I wanted to drive my Magnepan 3.6, which are 4 ohm.

So I built a bigger version push pull, with parallel output devices and a 65V rail. This produces easily enough power to drive my maggies. I coined the name "moskido" for this amp (which John liked).

The lower voltage, lower cost BUZ900/905 mosfets were used (160V instead of 200V breakdown) .

The standing current on my amp is 2A (1A per device) and this means that each channel dissipates 130W. It is my understanding that it will produce about 64W into 4 ohms.

John has recently posted some new 'moskido' designs here

Note that it's perfectly normal for him to change designs. In fact I think if you asked him to draw the same circuit twice he would not be able to

On his latest post he has altered the output stage, making it asymmetrical. I queried him about this and he said:

Quote:
I should have explained the mismatched devices. N-channel MOSFETs have more transconductance than Plate-channel MOSFETs, so the bigger resistors balance the transconductance by swapping some of the N-channel MOSFET's transconductance for increased linearity. The devices do not match in input capacitance, so some extra capacitance can be added to the N-channel MOSFET's input.

Dougie085 : if you have any more questions feel free to post here or email me directly. I'm keen to see how other people find this design works out for them.
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Old 26th June 2007, 03:03 AM   #9
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As soon as this moderation thing goes away I'd be happy to email you Alright its not there anymore!
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Old 26th June 2007, 11:53 PM   #10
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Ok so is this Moskido truly a hybrid tube/ss amp? Or is it a ss amp with a tube pre? Little confused. Is an active pre something thats like built into an amp? I want to use these as integrated amps will the Moskido be good for that? And would I still get the benefits of a hybrid amp going this route?
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