Moskido - Hybrid Aikido/MOSFET amplifier

[athos56]

I've made 3 Aikido stages, 1 preamp, 1 SE front end, 1 moskito front end. My first PSU worked so well I tend to use it for everything, but it takes up space and money. Its a C-LC-LC-RC, I've also used just one LC section. I think with the cost of the parts for the regulators and the space for the boards I think it might be a wash. I can't hear the noise from my sitting position which is really all I can expect from speakers in the high 90's in sensitivity.

[Stef]

I also have two Aikido stages:

Line-amp that uses 0.5mf - 25H(270r) - 60mf - 45h(950r) - 30mf - 330r - 30mf. All caps are motor runs. Sounds pretty good - but not as good as my Borbely line-amp..... yet.

A pre-stage for my moskido uses 0.5mf - 35h (350r) - 100mf - 500r - 100mf - 500r - 30mf. Caps are electrolytic except the last one. Also sounds pretty good but there is room for improvement here I feel. Sounds as good as my Legacy 300b (in a different way).

Ideally I'd like to go regulated but can't work up the enthusiasm, at least until someone tries it out and then raves about it.

[kacernator]

Hi,

what is the voltage needed to drive the mosfets to full power with +-30V DC voltages and 1.2A bias current?
I am wondering if I can use lower mu tube at first position and still get the full power out of moskido.

Thank you.

[beau2317]

Hi, I just checked this thread and although I am subscribed I have missed the previous few messages. Not sure why.

Anyway I'm still here and will check back more often. My moskido is runnign just fine still.

I noted a few messages ago about the lack of mids; I'm wondering if this was on the AC or DC coupled moskido. The DC coupled version does have better mids. And bass and treble :-)

[beau2317]

Originally Posted by kacernator

Hi,

what is the voltage needed to drive the mosfets to full power with +-30V DC voltages and 1.2A bias current?
I am wondering if I can use lower mu tube at first position and still get the full power out of moskido.

Thank you.

It depends on the speaker load, 8ohm or 4ohm. Also it depends on how much voltage the input source is providing.

[Her_lennon]

Hi Beau,

How are you?

This is the first time I write but I have read the entire thread several times . I'm building your last version without output cap and bias control. My transformer is 25-0-25 and i'm thinking to set Bias in about 1.2A for each. My question for you is: I have only one pair of BUZ990P/905P for each channel. This is the only difference compared to yours. Can i have any thermal problem by using only one pair?

Thank you!!
Hernan.-

[ben62670]

I hope I have a very simple question. I have an Adcom GFA-545 and it has a 2SC2344 and 2SA1011 drivers, and 3 each 2SC2581, and 2SA1106 output trannies that operate on +-55vdc rails. Can I use the Moskido input and driver stage to drive the output stage of the Adcom. I want to do the same thing to my Adcom GFA-565's if the 545 experiment works

[Francois G]

Originally Posted by ben62670

I hope I have a very simple question. I have an Adcom GFA-545 and it has a 2SC2344 and 2SA1011 drivers, and 3 each 2SC2581, and 2SA1106 output trannies that operate on +-55vdc rails. )

I have a 555II and had similar thoughts. However, it is not a simple question - I believe a lot of redesign will be necessary to make it work in any acceptable manner.

My 555II has relatively small heatsinks - far too small to run with any current on +55/-55 rails. So, you will not be class in A - an important feature of the Moskido. You will need to do the calculations to see how much current you can use based on heatsink capacity, but my guess is it will be less that a 1/4 amp.

The Moskido does not use loop feedback; you will also have to deal with adjusting the feedback since Adcom used feedback - I don't know how much but I guess a lot.

The other problem is the voltage output of the Aikido - you will need to check it's behavior and drive abilities at high output (to drive the output transistors anywhere near +55/-55, if they are followers without gain) . This "new" amp has unpredictable sound performance unless tweeked just right, with feedback and all.

I am not expert enough to do this type of redesign and resolved to follow beau's published design.

Good luck!

[Francois G]

Originally Posted by Her_lennon

Hi Beau,

How are you?

My transformer is 25-0-25 and i'm thinking to set Bias in about 1.2A for each. My question for you is: I have only one pair of BUZ990P/905P for each channel. This is the only difference compared to yours. Can i have any thermal problem by using only one pair?
Hernan.-

Hi Hernan,

beau must be away somewhere - I will give you my opinion.

In order to answer the question one needs to know the capacity of the heatsinks you are using. So, if you are also using the giant heatsinks beau used you might be OK, but to be safe start with no more than 1 amp and increase if the heatsink temps are acceptable. Best would to learn the calculations to size heatsinks properly.

[Her_lennon]

Francois,

Thank you!!

I think to buy some of the "medium powered" line here INTERNATIONAL ALUEL. What do you think? Or do you think that is better some of the "High Powered" line. I'm trying to get a heatskins that works and and which is not so big.