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Old 24th November 2005, 05:22 PM   #1
Tyimo is offline Tyimo  Hungary
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Default Cascaded Amps

Hi!

I found somewhere the attached schematic and I would like to know about it a bit more....
Is there anybody who know this amp?

Greets:

Tyimo
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Old 24th November 2005, 05:45 PM   #2
hihopes is offline hihopes  South Africa
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Its all Greek to me. (Sorry, couldn't resist that!)
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Old 24th November 2005, 05:47 PM   #3
Tyimo is offline Tyimo  Hungary
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Quote:
Its all Greek to me
Sorry, but it is russian.... :-))

Tyimo
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Old 24th November 2005, 06:38 PM   #4
Allexx is offline Allexx  Ukraine
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Hi Tyimo,
It says that output power is 30W, power consumption is 160W.
Alex
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Old 24th November 2005, 08:21 PM   #5
djk is offline djk
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The 2SK77 was made by Yamaha and used in the B1 amplifier, a 150W/8R class AB push-pull unit.

They are un-obtainable, and were a non-standard case style.

It would be possible to cascode the Lovoltec power J-FETs and duplicate this device.
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Old 25th November 2005, 04:38 AM   #6
Tyimo is offline Tyimo  Hungary
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Thanks Alex!

Quote:
They are un-obtainable
Thanks DJK! Not a very good news.......

What is this design? Where is it from? Is it Yamaha???

Tyimo
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Old 25th November 2005, 06:01 AM   #7
djk is offline djk
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The design with the Lovoltec part is from Nelson Pass.

http://www.passdiy.com/pdf/ZV8_power_jfet.pdf

The pdf also has a block diagram of the Yamaha B1.

If you made the amp push-pull instead of single ended you can get much higher power out. It is all a matter of choices.

The Lovoltec parts are subject to a $1000 minimum order, DIY audio members are getting together a group buy right now.

http://www.diyaudio.com/wiki/index.p...ec+Power+jfets
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Old 25th November 2005, 05:56 PM   #8
Tyimo is offline Tyimo  Hungary
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Hi DJK!

Thanks for the infos, but I know them already, because I am coming from the Pass forum too. :-)

I was asking about the attached schematic from me and not about the B1.
I meant with my question: is that schem realy an existing amp or only a theoretical plan?

Greets:

Tyimo
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Old 25th November 2005, 07:33 PM   #9
djk is offline djk
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Hi Tyimo!

That was from Michael Kosarev:

http://www.k-amps.8m.com/circuits.htm

I don't know if it is a real amp, I think not.

The FETs were only available as a replacement part for the Yamaha B1 amplifier, only made for a few years in the mid 70s. I was an authorized service center at that time.

The 100W/8R rated B2 used the smaller TO-3 case FETs. Yamaha told us they lost money on the sale of every B2 at $850. The replacement cost for a set of FETs was around $250, and they came mounted on the heatsinks.
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Old 26th November 2005, 07:56 PM   #10
Tyimo is offline Tyimo  Hungary
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Hi DJK!

Thanks a lot!!!
So, I will stay by the Pass JFetamp.

Greets:

Tyimo
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