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Old 16th March 2015, 01:09 PM   #1
Eldam is offline Eldam  France
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Default 6072A as DAC outputstage

Hi,

I have some pain to source at good (reasonable) price a NOS 6072A !


Are there please any reasonable NOS model and serious shop in Europe for this ?

Look at at Jan Music with no success !


I would like to try first this tube as I'm beginner before jumping to some more problematic tubes like the 3DA (easier to source) and expensive because the layout !
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Old 16th March 2015, 01:41 PM   #2
Stixx is online now Stixx  Germany
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D,

NOS 6072a seems very expensive nowadays...

Then there is EH ones here --> EH 12AY7 / 6072A Electro Harmonix / Russia - Vorstufenröhren:
or EH 6072A/12AY7, 15,80 € or
12AY7/6072A TAD Premium Selected - TAD Vorstufenröhren SELECTED Tube

D3A I have at home... unused. You can have them
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Old 16th March 2015, 04:52 PM   #3
Eldam is offline Eldam  France
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HellO²,

Sound slike you gave up the idea of tubing a 1541 ? Or Family's baby doesn't enjoy to see lighted bottle feeding in the living room!

PM me please !

Thank you for the link ! If too expensive I will beginn with brand new Electro Harmonix 6072A instead NOS one !

cheers,

D
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Old 16th March 2015, 06:05 PM   #4
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Hello,

basically you could use nearly every tube as a output stage, as long as it is suitable for audio use ( linear characteristics, check datasheets ). You will have a strong negative feedback anyway which would take care of distortion ( though it will be higher than that of a Opamp ).

Balanced-Ouput DACs and Tubes and Aikido

Have a look at the " Balanced DAC & Filtered Broskie cathode follower ".

Be sure to chose a operating point with enough headroom ( about -4V UG1 if your DAC has a output of each +- 2,5V ) to make sure that you don´t draw grid current..

I wanted to build a tube output stage myself but it is pointless for me since I already use DIY tube amps with my DAC. If you intend to use a transistor amplifier with your DAC and hope for some tube distortion, you may build your tube output buffer

But remember, most tubes require a high voltage in order to operate properly, DC heater ( you might need to elevate the heater potential of the upper tube ) and a clean power supply.

In terms of output distortion, noise it will perform worse than a Opamp though..

Best regards,

Last edited by Gorgomat; 16th March 2015 at 06:09 PM.
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Old 16th March 2015, 11:01 PM   #5
Eldam is offline Eldam  France
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Thank you,

Great paper!

Basicly I wanted to make a tube(s) pre with an unity gain 12ax7 tube and a sota traffo output... And yes to add some H2 and nice distorsion before a solid State amp (85 db speaker ).

Because both I'm beginner and it's a too costy project, I would go for a good output with a TDA1541 chip. I'm sure a oap amp is quieter! Btw have a lot of pleasure listening an Audial AYA 2014 TDA1541 dac.

For some reason I don't want to go for a balanced dac chip.

I would like to try a not too much expensive 6072A to make it à la Thorsten Loesch, this tube is easier for a beginner; Even a 6922 à la Zanden would be an hassle for me for a diy project and a first one with tubes ! So not talking yet of a 3DA whic is a good tube for a tda1541 if you know enough about wild horses and layout .

I can buy a brand new 6072A Electro Harmonix and should do (20 euros - with shipping-Stixx's link)). But if I can find a no too bad NOS 6072A adding a little plus money... (60 to 80 euros?) why not. If too rare at this price or not worth to pay x3 or x4 for the a too little added quality in relation to the brand new one: better to forgett the NOS ?

Last edited by Eldam; 16th March 2015 at 11:06 PM.
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Old 17th March 2015, 12:31 AM   #6
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I would forget about "NOS" tubes...leave them for the guys who like to pay a lot of $$$ because they believe in their religion..

If you want to build a catode follower output stage, don´t forget that the max. gain is <1 ( nearly 1, unity gain ). You have a strong negative feedback through the catode resistor which will barely make a difference if you compare eg. a super expensive Telefunken E88CC or a cheap E88CC from JJ.
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Old 17th March 2015, 01:08 AM   #7
Eldam is offline Eldam  France
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Find a store with a new 6072A from EH at 1.5 hours from where I live ! Believe I would beginn with this tube.

Thanks G.
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Old 17th March 2015, 09:50 AM   #8
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Well, if you really want a exotic ( and expensive ) NOS tube, buy it I made some calculations and designed a catode follower with a more common tube How about a ECC99 ?

Best regards,
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Old 17th March 2015, 03:32 PM   #9
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Quote:
Originally Posted by Gorgomat View Post
How about a ECC99 ?
That would be an excellent choice: high transconductance, medium gain, and linear.
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Old 17th March 2015, 09:51 PM   #10
Eldam is offline Eldam  France
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Thorsten Loesch uses the 6072A for basic mods with tda1541 ! 6922, D3A are goods but problematics for beginners ! because too high high transconductance ?

T. Loesch use the "drift" of the dac chip current output than passive i/v of the TDA1541 to load the tube and one of the easiest to do that is the 6072A according to him and many experienced diyers with both this dac chip and tubes ! Though with experiences you can uses any good tubes :cd-77 is 5687 iirc and a Mulard ??? !

Could an ECC99 a good competitor or in the same family than the 6922, 3DA ?

The new EH 6072A is 17 euros here, so why not follow T. Loesch shematics and advices ?
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