The Kuartlotron - keantoken's simple error-correction superbuffer

[lgabco]

I have built the first Keanotokens Kuartlotron in January this year. I liked the sound very much so I decided to build it one more time with better power supply and better parts.
My present reference preamp is based on Erno Borbely module EB325. I have bought it from Erno few years ago. Erno made it and tested by himself and then he sent it to me. Together with Salas voltage shunt regulator as a power supply I use it for many years.
Since that time I have tested about 4 another preamps but I always concluded that EB325 sound is better than any other preamp.
Since I have excellent experience with Salas voltage shunt regulator I decided to use it together with Kuartlotron too. Here is the result.
Salas+Kean1.JPG

Salas+Kean2.JPG

[Destroyer OS]

How does it compare?

[lgabco]

As you could see I use as a basic power supply two SMPS. They are 24V/15W modules from Mean Well. I have bought it from Mouser.
Then the voltage is regulated by Slalas regs and it is used as a power supply for 4 Kuartlotron modules. In this time I use only two modules.
The sound:
The sound is really excellent. I had a prejudice that only JFET input transistors could do the work properly. All my previous experience was showing that the bipolars at the input do not sound good. But this time it is different. There is absence of any kind of aggresiveness and the low level details are more pleasant then in my reference preamp from Erno Borbely. Beside this the sound is really musical and full of joy and far away from opamp preams I have ever heard.
For the completeness, my system: CD player/DAC Audiolab 8200CD, Kuartlotron vs. EB325 as preamps, HYPA 17 power amp, Ellam flex 3W speakers, ClearAudio interconnects and Chord Odyssey 2 speaker cables.

Ladislav

[lohk]

Received your boards, nice and tiny! That was quick, thank you!

One question: In your paper about the Kuartlotron you write that Q1 should be thermally coupled to Q3, and Q2 to Q4. On your boards the transistors are not arranged like that. What did I miss here?

[lohk]

Originally Posted by Destroyer OS.

Heatshrink worked really well to thermally couple the TO-92 transistors.

I'm trying the onboard inductor even though I have a couple other ones. I used a piece of lead to bridge them because I found my kester 44 didn't want to without a massive glob.

What 470uF caps did you use?

[Destroyer OS]

They're 16v Panasonic OSCON, SEPF series. Nichicon FP would be a real snazzy choice as well. I wanted something to try and match the performance of the circuit, and these are the best non-film things I've used.

[lohk]

Ok, thanks. But, are you sure? The Panasonic data sheet for the SEPF Oscon does not show any 470uF cap with 16V, only 560uF.

[Destroyer OS]

Sorry, SEPC in this case, same sort of family. http://www.mouser.com/ProductDetail/...%252bwW3LDI%3d

[keantoken]

Good to hear you are having good results lgabco.

The capacitance isn't critical as long as it fits the pad.

The benefits of the alternate coupling are theoretical, the board is designed like my prototype which I used for all the testing. Either way works.

[lohk]

While waiting for some "boutique" parts to arrive (I know they are not really necessary, but...) I would like to ask you guys for your experience with input potentiometers: I want to use no coupling capacitors if possible. Will there be any significant offset change if I - say - connect a 10k pot and change R8 to - say -100k?