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Old 9th January 2012, 09:47 AM   #4111
galeb is offline galeb  Spain
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Hi,

Respect to the output stage, just an impression. I've been testing for several months all the resistors available on the market, at least, all the ones that I could buy. I'm currently using the brand Takman, carbon series of 0,25w for all the positions of the circuit. Please, do use complete aikido design, it works incredible fine. I/V resistor is extremely important, it gives the final and correct character to the DAC. I'm using 39 ohms for th I/V. These resistors made the noise to quasi completely dissapeared, gave a neutral tone, correct bass, sweet voices, and ver very fine highs, after some hours of use. I use 6N2P and 6H23. I still have to test 12AX7 vs 6N2P, but for now, it works very fine. I'm using too 4x"duende criatura" rings for the tubes. I'm using for the output cap "oil Vcap", 4x4,7uf. I'm bourning now a pair of Clarity caps of 10uf ESA series and a pair of 4,7uf MR series to test them late, in some days. Supply voltage is 200vdc, choque filtered. Be very careful with the wire you use to connect all this. I use VDH D102 MKIII, the internal wires. A new stage of silence is obtained.

Hope this helps someone.
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Old 9th January 2012, 11:30 AM   #4112
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Thanks for sharing Galeb.

Have you tried John's self-made resistors?
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Old 9th January 2012, 11:44 AM   #4113
galeb is offline galeb  Spain
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Hi Studiostevus. I didn't because the time to build a pair. I can asure you that Takman work incredible. When I have some time and wire, I'll build a pair, then share with all the listening results. But now, with this set-up, I can easily win practically all the brands I've heard.

regards,
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Old 9th January 2012, 11:58 AM   #4114
brubeck is offline brubeck  Netherlands
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I had the change to visit ECdesigns to listen to the latest masterclock (re)design in a prototype setup. On the way to Beringe i cracked my brain how it could sound even better? The Mk7 dac which i play with at home on batteries, seems almost unsurpassable to me. John continues to improve the circuit, but are these improvements worth an upgrade again ? After listening some audiophile tunes i had to conclude that the new masterclock seems to add more (bit)resolution and more secure timing. With good recordings the tones are more round with more natural extinction. It improves the depth experience and comes closer to a analog like representation of human voices and instruments. It is a little shift to more music instead of good sound. To get the potential of these improvements it is imo a strict condition to follow the dac with a very, very clean and secure amplifier and sensitive speakers. Otherwise the potential profit will get lost in the noise treshold or losses in the circuit.
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Old 9th January 2012, 12:11 PM   #4115
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Hi Hans, thanks for sharing your thoughts. I was wondering already whether you were still involved in the project.
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Old 9th January 2012, 02:08 PM   #4116
roger57 is offline roger57  Canada
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Quote:
Originally Posted by galeb View Post
Hi,

Respect to the output stage, just an impression. I've been testing for several months all the resistors available on the market, at least, all the ones that I could buy. I'm currently using the brand Takman, carbon series of 0,25w for all the positions of the circuit. Please, do use complete aikido design, it works incredible fine. I/V resistor is extremely important, it gives the final and correct character to the DAC. I'm using 39 ohms for th I/V. These resistors made the noise to quasi completely dissapeared, gave a neutral tone, correct bass, sweet voices, and ver very fine highs, after some hours of use. I use 6N2P and 6H23. I still have to test 12AX7 vs 6N2P, but for now, it works very fine. I'm using too 4x"duende criatura" rings for the tubes. I'm using for the output cap "oil Vcap", 4x4,7uf. I'm bourning now a pair of Clarity caps of 10uf ESA series and a pair of 4,7uf MR series to test them late, in some days. Supply voltage is 200vdc, choque filtered. Be very careful with the wire you use to connect all this. I use VDH D102 MKIII, the internal wires. A new stage of silence is obtained.

Hope this helps someone.

Hi Galeb,

With just 39 ohms for the I/V resistor, you must have fairly high gain, or are you using a 2 gain stage - you did mention the Aikido? I'm using 2x 120 Mills MRA05 in parallel for 60 ohms. Without cathode bypassing, I can get about 1.85V p-p, which can adequately drive the Aikido preamp.
For the I/V resistor, did you ever try the TX2575? I plan on trying one just to compare to the Mills NI WW.

Gary
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Old 9th January 2012, 02:12 PM   #4117
roger57 is offline roger57  Canada
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Quote:
Originally Posted by roger57 View Post
Hi Galeb,

With just 39 ohms for the I/V resistor, you must have fairly high gain, or are you using a 2 gain stage - you did mention the Aikido? I'm using 2x 120 Mills MRA05 in parallel for 60 ohms. Without cathode bypassing, I can get about 1.85V p-p, which can adequately drive the Aikido preamp.
For the I/V resistor, did you ever try the TX2575? I plan on trying one just to compare to the Mills NI WW.

Gary
Err....that should have been 3.6V p-p !!

Gary
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Old 9th January 2012, 02:30 PM   #4118
brubeck is offline brubeck  Netherlands
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Quote:
Originally Posted by studiostevus View Post
Hi Hans, thanks for sharing your thoughts. I was wondering already whether you were still involved in the project.
Hi, yes 100% I drove 370km yesterday. It’s always pleasant and has great educational value to discuss and audit John’s latest inventions.
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Old 9th January 2012, 03:18 PM   #4119
galeb is offline galeb  Spain
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Hi, roger 57.

Yes, I've tested this and even a 15W 1k5 resistor, removing the nicrom wire and making a pair of 39 ohm resistors, matched to 0,5%. All those kind of resistors give to the sound a very metallic character, and being very defined, it's too bright. For me, now, the Takman are the best. I use 39 ohms to obtain 156mVpp, and with the amplification factor of the 6N2P, I have 2 V RMS at the output. I use 2 stages, the first is the gain one, and the second is a current buffer. All "a la" Aikido way. I don't recommend to use any other configuration, this includes the "Lampizator". This circuit, that existed a lot of years ago doesn't have enought current to drive a preamp correctly, at least with this high mu triodes only.

Values of resistor above 40 ohms are bad because the distorsion factor is too high. It's better to chose a high gain tube, and lower the resistor value. I'm in the limit of this value.

regards,
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Old 9th January 2012, 03:34 PM   #4120
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What is a current buffer?
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