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Old 17th December 2011, 04:15 PM   #1
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Default Kumisa III Amp

Hi, anyone build the Kumisa III PreAmp?

How it sound? Better than a global feedback preamp?

I will work in a PCB for this preamp, and I like some opinions before.

Click the image to open in full size.
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Old 19th December 2011, 05:48 PM   #2
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Hi, the amp sound very good.

This is the 1st PCB prototype, what do you think?

Some resistor are in the botton side. Links are only GND or +/-Vcc.
Size 5cm x 7cm, DC servo included.
Attached Images
File Type: png preKUM PCB.png (26.3 KB, 593 views)
File Type: png preKUM PCB1.png (23.5 KB, 600 views)
File Type: png preKUM sch.png (27.2 KB, 789 views)
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Old 20th December 2011, 01:43 PM   #3
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You can get boards for the opgraded version here AMB audio shop
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Old 22nd December 2011, 12:53 PM   #4
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Hi burgunder, I know this page. Very interesting proyects. But I want to make my own design.

This is the last version. Opamp is soldier like SMD, on the bottom side. Less than 5cm x 7cm.
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File Type: png ver2b.png (28.9 KB, 118 views)
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Old 5th January 2012, 10:19 PM   #5
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This is the final amp. Size of PCB 5cmx7cm

It sound very good!
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File Type: jpg 1.jpg (13.9 KB, 228 views)
File Type: jpg 2.jpg (13.4 KB, 217 views)
File Type: jpg 4.jpg (13.9 KB, 243 views)
File Type: jpg 3.jpg (19.5 KB, 260 views)
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Old 6th April 2012, 03:57 PM   #6
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Most ppl built the CK (Cavalli Kan) version, but i prefer the design of the original (except maybe for the servo), provided that the result is free of oscillations.
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Old 20th August 2012, 04:13 PM   #7
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Hiya,

I did some output devices evaluation test on the CK2III.
I'm thinking now to try an EF output stage on the pcbs i have (AMB ones). The rest of the changes don't bother me.
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Old 14th January 2013, 01:48 PM   #8
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I see I'm the only one following this thread, but I'll post anyway

Work in progress of my second CK2III board, which will be adapted to EF output stage using the original Toshiba drivers and Rohm output transistors (the latter are sounding great in the CFP stage of my other CK2).

ATM I'm awaiting delivery of the psu and a batch of Rohm 2SB1186A/2SD1763A from which I'll match a quad.
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File Type: jpg ck 001s.jpg (430.8 KB, 154 views)
File Type: jpg ck 002s.jpg (484.2 KB, 136 views)
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Old 19th January 2013, 08:45 AM   #9
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No denigration of Cavalli or Kan but if you get a working Kumisa3 preamp board going, I am sort of interested.
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Old 19th January 2013, 09:51 AM   #10
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Quote:
Originally Posted by ericj View Post
No denigration of Cavalli or Kan but if you get a working Kumisa3 preamp board going, I am sort of interested.
I understand. I have no plans to etch a pcb of the original schematic, at least not in the near future. I will post about my impression of using the original drivers/output transistors on the CK2III pcb (with just some cable extensions) and after comparison, I'll move on to different projects.
Then, if and only if the CK2III (either version) will still sound better to my ears than the other amps on my to build list, I can go as far as making the original pcb, the main differences being the bipolar input stage and the configuration of the servo opamp (I think the CK mod is better on this regard, but I'm open to discussion).
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