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Old 22nd March 2011, 10:19 AM   #21
sajti is online now sajti  Hungary
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I'm over the first test. Not yet listening, just some measurements. Ther will be some major, and minor issues, I have to solve. The DC offset is is liitle higher than I expected, and the adjustment is not possible. So I have to replace the trimmer, to get wider range for the offset compensation.
Another issue is the stability. The amplifier oscillate if I put more than 1uF capacitor across the 8ohm dummy load. There are some ringing on the square wave output with 1uF. So I have to replace the compensation network.
The output is little over 400W/4ohms.

Sajti
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Old 14th August 2012, 02:31 PM   #22
sajti is online now sajti  Hungary
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There was some different version, to listen, and test. What I found, that the KSC/KSA series transistors have not as good sound as the 2SC/2SA types. I have changed the protection little bit.
The solid state buffer finally based on Marantz SM11-S1, but with more output devices, and approx. 150W/8ohm output power.
Some pictures attached.

Sajti
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Old 14th August 2012, 03:41 PM   #23
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Quote:
Originally Posted by sajti View Post
There was some different version, to listen, and test. What I found, that the KSC/KSA series transistors have not as good sound as the 2SC/2SA types. I have changed the protection little bit.
The solid state buffer finally based on Marantz SM11-S1, but with more output devices, and approx. 150W/8ohm output power.
Some pictures attached.

Sajti
Doesnt what you call the buffer have voltage gain ?? I think it does from what I can remember from the marantz. Marantz must have contracted the designer from pioneer as the schematic is identical to the late 80s early 90s high end series pioneers.

In those days the european and american markets didnt regard the design good, now that marantz produces it its highly rated ???
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Old 14th August 2012, 04:12 PM   #24
sajti is online now sajti  Hungary
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Quote:
Originally Posted by homemodder View Post
Doesnt what you call the buffer have voltage gain ?? I think it does from what I can remember from the marantz. Marantz must have contracted the designer from pioneer as the schematic is identical to the late 80s early 90s high end series pioneers.

In those days the european and american markets didnt regard the design good, now that marantz produces it its highly rated ???
Yes it has the voltage gain of 2. You can check the schematic on the 1st page of this topic. There is some minor changes since the 1st version, but this are not serious.
This Marantz is a new design, I don't think that it's related to the amplifier form the 80s.

Sajti
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Old 14th August 2012, 04:51 PM   #25
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I have the service manuals, just did a quick peek some time back. New its not, consult pioneer schematics from that era. In fact it was pioneer which developed that voltage gain stage and at the time it was very much talked about.
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Old 14th August 2012, 06:48 PM   #26
sajti is online now sajti  Hungary
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OK I will check it! For me it's no problem, because it's sounds quite good. I use feedback only in the buffer, the tube stage has only local feedback. The gains gives some flexibility to try different tube types in the 1st stage.

Sajti
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Old 16th August 2012, 03:37 PM   #27
sajti is online now sajti  Hungary
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The input stage will be E88CC two half connected parallel, common cathode.
Expected output power 140W/8ohm, 220W/4ohm, 400W/2ohm (simulated). Option is the bridging to drive my 4ohm subs (2xBeyma 18G550 bassreflex).

Sajti
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Old 18th September 2012, 10:38 AM   #28
sajti is online now sajti  Hungary
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I did some listening tests, and the result was quite good. The amplifier sounds fast, with rock solid bass, and it has some sweetness usually associated with the tubes.
I was quite satisfied, but I had an idea, due my CD olayer has balanced output. So I bridged the two amplifier, and made some listening, only in mono. And it was absolutely different! Another amplifier, like the dirty window compared to the clean...
I set up the another channel, due I have 4 panels, and it was amazing. Strong, detailed and sweet, same time!
So I planned another driver stage, which is under construction. It contains E88CC long tailed, with cascoded DN2540 as ccs at the tail.
So it will be truly balanced amplifier input, to output.
Finnally the measured output power:530W/8ohms, 970W/4ohms before clipping.
The only issue I have to solve is a stronger driver, as I use 2SC5171/2SA1930 currently, and I don't sure that they can handle the current.

Sajti
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Old 18th September 2012, 10:58 AM   #29
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You can use 2sa1837 and complement, although a little slower they have higher SOA. Another option is to use onsemi drivers (mje1503x series) but again speed penalty. Best way is what Pioneer used to do, parralell two 2sc5171/2sa1930 with a current sharing resistor of around 3 ohms.
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Old 18th September 2012, 01:27 PM   #30
sajti is online now sajti  Hungary
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Quote:
Originally Posted by homemodder View Post
You can use 2sa1837 and complement, although a little slower they have higher SOA. Another option is to use onsemi drivers (mje1503x series) but again speed penalty. Best way is what Pioneer used to do, parralell two 2sc5171/2sa1930 with a current sharing resistor of around 3 ohms.
Thanks the idea! I used 4793/1837, but the 5171/1930 has better sound. Paralell driver can be option! I will check. With 4ohm resistive load the maximum driver current in 190mA (simulated).

Sajti
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