Moskido - Hybrid Aikido/MOSFET amplifier

[Mush]

Hi,
I've just discovered this wonderful thread and am now convinced to build a DC Moskido. Thank you, Mr. Pragnell, for such an elegant design and your generosity.

And now, I have a few questions.

1) Do the IRF fets work as well as the Buz?

2) The new amp is using +/- 30vdc on the rails. I am running 4 ohm and sometime 8 ohm speakers. I need up to 30 watts of power. What is the best voltage for a fairly universal choice.

3) Are there an PCBs available for the DC version. I saw Minhtreit's in post #589. It's quite lovely but I don't have the software and skills to separate the layers.

4) Is a speaker delay really necessary with this amp?

I am sure I will have more questions as I have never built any kind of solid state or hybrid amp before.

Thanks for patience and kindness.

Ciao -- Mush

[athos56]

JB at Tubecad said that he thought the Buz sounded better. To-247 case Buz Mosfets can be had at Farnel. I used 50w heat sinks, 1 each, for the 16w Tubecad version (2 Mosfets per channel). The heatsink came from digikey (HS117-ND). Its for a to-3 case but I just used one of the mounting holes. There is a new revision of the mono-akidio boards that has the pads for the diode biasing so they might help.

[kacernator]

Originally posted by Mush
Hi,
I've just discovered this wonderful thread and am now convinced to build a DC Moskido. Thank you, Mr. Pragnell, for such an elegant design and your generosity.

And now, I have a few questions.

1) Do the IRF fets work as well as the Buz?

2) The new amp is using +/- 30vdc on the rails. I am running 4 ohm and sometime 8 ohm speakers. I need up to 30 watts of power. What is the best voltage for a fairly universal choice.

3) Are there an PCBs available for the DC version. I saw Minhtreit's in post #589. It's quite lovely but I don't have the software and skills to separate the layers.

4) Is a speaker delay really necessary with this amp?

I am sure I will have more questions as I have never built any kind of solid state or hybrid amp before.

Thanks for patience and kindness.

Ciao -- Mush

1 - BUZs mosfets sounds better than IRFP, they also have negative temperature coeficient, but they are more expensive.

4 - At startup (turn on) in my both two DC coupled moskidos, DC on the output rises to the full rail voltage for some time - cca 1-2 seconds. I think it is very wise to use some speaker delay and DC protection of speakers. In my country I boought completed small PCB which does both - speaker delay and DC protection, simple, easy, cheap and works like a charm. And I am way more calm, when I know I have some protection for my speakers.

[nigelwright7557]

Originally posted by beau2317
http://www.tubecad.com/2006/04/01/ai..._amplifier.png

I hope that URL works...

That's what it's based on, but I need to draw up the actual circuit and PSU I used...give me a day..

I designed my own hybrid using an SRPP ECC82 front end and a MOSFET 900watt power stage.

It gives very good results.

[kacernator]

Hi there moskido builders. Does anyone of you have pictures of your finished amplifier too?
Have you already compared your amplifier to another hi-end amps?

My cca 30W moskido beated some 7 years old Denon 7ch 200W, which then costed new about 3000 dollars.
Thats the only better amp I could find in my neighbour to compare with. I hope in future I will have opportunity to make contest with other amps as well.

[Francois G]

Thanks for getting the ball rolling on comparisons and listening tests again. Could you describe in more detail what differences you heard? Obviously the Denon has more power; what did it do better than your Moskido.

My listening test are still a few weeks of, but they are coming closer. Can’t wait to hear my Moskido DC. I have several highly regarded tube amps to compare it to – all push-pull.

Cheers,
Francois

[kacernator]

Originally posted by Francois G
Thanks for getting the ball rolling on comparisons and listening tests again. Could you describe in more detail what differences you heard? Obviously the Denon has more power; what did it do better than your Moskido.

My listening test are still a few weeks of, but they are coming closer. Can’t wait to hear my Moskido DC. I have several highly regarded tube amps to compare it to – all push-pull.

Cheers,
Francois

Hi,

yes Denon has more power, but my moskido felt like it was 150W instead of 40W when compared to Denon. What Denon did better were mids - distorted guitars in metal music were more clearly heard - I will come to this later in this post.. But that was the only thing where Denon was better. In imaging, depth, dynamics, presence, details, natural voice of instruments, sounds stage, speed etc. my moskido beats Denon without any doubts!

Now for the mids, today I was still feeling, that something is missing when playing my moskido. So I started to mess with my PSU. Before I had 47 Ohm - 220uF - 180 Ohm - 470uF in aikido PSU. Now I have 220uF - 47 Ohm - 470uF. So I ripped off one resistor and lowered the other one. Sound stage is much bigger, instruments are more separate and clearer and mids are definately back! I tried to lower the 47 Ohm to 0.2 Ohm, just to try, and it was better, but I got hum as it was not enough filtering.

Tomorrow I will mess with resistors in mosfet PSU.

Now I am totaly happy, for now I am missing nothing in my sound.

I know that very similiar effect, as lowering the PSU resistors, have grid stoppers. Now I have everywhere 330 Ohm. I would like to lower it to 100 Ohm in aikido stage, but I would must to dissasemble some pieces, it would take me an hour. If someone have easier acces to grid stoppers in aikido and would like to try it lower them to 100 Ohm and share about the result I will be very glad.

Thats all for now!

Cheers!

[Francois G]

Excellent post. Thanks. Interesting that you percieve 150w sound from your 40w Moskido. Wonder why?

Are you using resistors in the Aikido PS to lower the voltage or to aid ripple smoothing?

If it is the latter (and depending on your PS output also the first) I would recommend using a choke instead of a resistor. I have consistently found that my tube amps sound better with chokes.

I know John Broskie said that "heroic efforts" are not needed on the Aikido PS, but it sounds to me that you might benefit from CLC, LCLC power supply. I always try to use a separate choke in the last leg of the supply for each channel. That increases the separation and imaging for me.

For my Aikido PS I have a shunt regulator that I got from over at Group Buys. Have not tried it out yet.

Francois

[kacernator]

Originally posted by Francois G
Excellent post. Thanks. Interesting that you percieve 150w sound from your 40w Moskido. Wonder why?

Are you using resistors in the Aikido PS to lower the voltage or to aid ripple smoothing?

If it is the latter (and depending on your PS output also the first) I would recommend using a choke instead of a resistor. I have consistently found that my tube amps sound better with chokes.

I know John Broskie said that "heroic efforts" are not needed on the Aikido PS, but it sounds to me that you might benefit from CLC, LCLC power supply. I always try to use a separate choke in the last leg of the supply for each channel. That increases the separation and imaging for me.

For my Aikido PS I have a shunt regulator that I got from over at Group Buys. Have not tried it out yet.

Francois

Why? I think as moskido is so clean and so dynamic - everything stands out with ease, but Denon also amplifies lots of noise, so the music gets kind of lost - like a dirty,blury wall.

I tried CLC before, but to my ears resistor sound more natural, better flow of music, more relaxing to me and also is a lot cheaper, smaller and lighter .

[JackieTang]

Have any nice guy used Mr. John Broskie's Janus and/or PS-1 as the power supply regulator for Aikiko Stage?

If yes, does Moskido sound better?

Regards
Jackie