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The Kuartlotron - keantoken's simple error-correction superbuffer
The Kuartlotron - keantoken's simple error-correction superbuffer
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Old 7th April 2021, 04:57 AM   #1001
Cney is offline Cney
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I came across your buffer and I like the simplicity of it and the idea behind it. Also the compact size makes it a good candidate for my Soekris DAM1941 build.

I had a question though. Could 2 Kuartlotrons be modified to be used as a balanced to single ended converter after a quad of Kuartlotrons behind the balanced signal of the DAM1941?
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Old 7th April 2021, 08:38 AM   #1002
keantoken is offline keantoken  United States
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Is there a need to combine balanced phases to cancel common mode noise? If not I would just buffer one phase and use it as unbalanced. I'm not sure if there is a better way if you intend to use Kuartlotrons.
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Last edited by keantoken; 7th April 2021 at 08:46 AM.
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Old 7th April 2021, 10:05 AM   #1003
Zoran is offline Zoran  Serbia
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@Cney
there will be more issues to consider.
.
diskrete DAC has 1/2+V of the offset at the output? That is +1.65V if power supply is 3.3V most lightly. So the coupling C will be necessery?
.
Another thing is output resistance of the DAC that is tipicaly R value (from the R2-R ladder net). That is probably 2K to 5K? I dont know?
So there will be some attenuation because of 10K input at the buffer?
I have R value of parallel R2R net 10K-5K so 2.5K is equivalent generator resistance in my case. So 10K to ground at input was small value in my case and I had to move to higher values to avoid atenuation and LowPass analog filter needed higher R load to get proper Fo cut off... The output resistance og the dac is pretyy high i think.
.
And third thing - If You plan to use diferential mode 2 buffers and transformer after that to acheive SE, that transfprmer should have some sufficent inductance of primary. Because I think that output resistance of the buffer is not too low?
.
I tried JFET at the "input" branch, to increase Rin to several hudred Kilos. And Germanium AD161 at the output. With 340ohms series resistor from output tap to -V. To drive very low primary inductance transformer to get good LF bandwidthh...
I will post the shematic
.
Next - some small offset probably will be present at the output when power off buffers
and that offset probaly would not be tha same so the slight magnetization of the transfrmer will be present. That may not be very good?
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Last edited by Zoran; 7th April 2021 at 10:15 AM.
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Old 7th April 2021, 11:36 AM   #1004
Cney is offline Cney
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There's not really a need to cancel common mode noise before it goes to the RCA output. it's only a short lead inside the case so it is an option to just use one out per channel from the balanced section. Though I would only use half of the dac then. I would like to combine these so I would use both resistor ladders for the RCA as well. It's merely because I would like to have that. I could do it with an opamp after the Kuartlotrons but I would like to have the full output stage discrete.
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Old 7th April 2021, 11:47 AM   #1005
Cney is offline Cney
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Join Date: Sep 2015
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Quote:
Originally Posted by Zoran View Post
@Cney
there will be more issues to consider.
.
diskrete DAC has 1/2+V of the offset at the output? That is +1.65V if power supply is 3.3V most lightly. So the coupling C will be necessery?
.
Another thing is output resistance of the DAC that is tipicaly R value (from the R2-R ladder net). That is probably 2K to 5K? I dont know?
So there will be some attenuation because of 10K input at the buffer?
I have R value of parallel R2R net 10K-5K so 2.5K is equivalent generator resistance in my case. So 10K to ground at input was small value in my case and I had to move to higher values to avoid atenuation and LowPass analog filter needed higher R load to get proper Fo cut off... The output resistance og the dac is pretyy high i think.
.
And third thing - If You plan to use diferential mode 2 buffers and transformer after that to acheive SE, that transfprmer should have some sufficent inductance of primary. Because I think that output resistance of the buffer is not too low?
.
I tried JFET at the "input" branch, to increase Rin to several hudred Kilos. And Germanium AD161 at the output. With 340ohms series resistor from output tap to -V. To drive very low primary inductance transformer to get good LF bandwidthh...
I will post the shematic
.
Next - some small offset probably will be present at the output when power off buffers
and that offset probaly would not be tha same so the slight magnetization of the transfrmer will be present. That may not be very good?
The output is SE 1.3V, Balanced is 2.6V RMS, Zout 625R. I would like to not use a transformer for Bal/SE if I can. I'm a mechanical engineer so I have some skill regarding electronics but I can't design or alter a stage in these kind of ways. The dac now has a simple buffer with 3 OPA1678, 2 directly at the output of the dac to the XLR and one performing the bal/SE conversion after that stage.
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Old 7th April 2021, 08:10 PM   #1006
Zoran is offline Zoran  Serbia
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Sorry I didnt know that You already have some analog stage after DAC
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Old 8th April 2021, 04:50 AM   #1007
Cney is offline Cney
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Quote:
Originally Posted by Zoran View Post
Sorry I didnt know that You already have some analog stage after DAC
It's just a simple opamp stage that you can buy with the Soekris DAM1941 as a test. But I'd like to replace it with a good transistor output for the XLR to drive longish cables in my studio and RCA to use it in my hifi set also.

I thought of Nelson Pass B1 but the Kuartlotron looked promising. I might try it for just the balanced section and I will see if I can sum the outputs for the RCA using an opamp or transformer and see how that works.
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Old 8th April 2021, 06:48 AM   #1008
TNT is offline TNT  Sweden
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The Kuartlotron - keantoken's simple error-correction superbuffer
1941 has no offset on output. Output impedance is 560 ohm per half.

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Old 20th April 2021, 04:15 AM   #1009
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Is it still possible to get PCB's for the Kuartlotron?
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Old 20th April 2021, 07:56 AM   #1010
keantoken is offline keantoken  United States
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Yes.
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