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Old 11th December 2008, 08:10 PM   #11
kevinkr is offline kevinkr  United States
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Originally posted by Eli Duttman


Would choke loading a 'SN7 SRPP with something like a MagneQuest EXO-99 and buffering it with an IRFBC20 alter the calculus? All possible gain would be realized and linearity is (naturally) a given.

Hi Eli,
I have actually used a very similar circuit to drive 2A3 without the mosfet, it actually behaves like a mu-follower, but bass performance is very dependent on the available inductance. I was using 100H MQ chokes and found that something higher than that would be better still - I don't think 200H is overkill, but since I also used the dcr of the choke to bias the upper tube high value chokes aren't that practical. The gain however is still only 20 (even with a mosfet buffer) which is useful for driving a 2A3, but not enough here.
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
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Old 11th December 2008, 08:22 PM   #12
devas is offline devas  France
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thanks indeed Karsten for the link !

I'll try it as soon as possible and will report about the result and the diysupply option too.
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Old 12th December 2008, 12:32 PM   #13
JC951t is offline JC951t  Taiwan
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Hi Devas,
Could you tell me the sound of the 6n2p pls.
Also did you bypass the dac pin with 2.2uf caps
as Lukasz suggested ?

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Old 12th December 2008, 03:47 PM   #14
devas is offline devas  France
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I haven't done mods in the Satch Dac but for the output caps, as I consider that it works well enough as it is. The only thing I had in mind was to implement a Tentlabs Dac clock.

As I said before the 6n2p circuit sounded to me crispier and thinner than the other tubes I had tried, perhaps even crispier that the op-amp option. All my tests were made with EZ80 tube rectifier of different brands, the change of this latter affects the sound a lot.
With a classic i/u resistor of 22/33 ohms I had to put the darkest ez80 (Siemens or Sylvania) to get the balance right.
With 100 ohms I had to put the brightest ez80 (Tungsram) and it was still on the dark side.

It's not bad but I don't consider it worthwhile on my system for sense of detail,balance and tone appeared better to me with the d3a or the op-amp configuration. But this is just my opinion.
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Old 12th December 2008, 04:05 PM   #15
JC951t is offline JC951t  Taiwan
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Hi devas,

Thanks for your reply. So, you're still running
OS with the Satch & not in NOS mode ?
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Old 12th December 2008, 05:06 PM   #16
devas is offline devas  France
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Yes I tried in NOS configuration and found that there was less air between instruments and definitely prefer the soundstage in OS.

Before the Satch I had a tda1545 Monica with a tube output stage and tried to convert with all my heart to the religion of NOS but I think I'm still a non believer of unique truth and rather always open to enlighted contradictions...
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Old 12th December 2008, 10:27 PM   #17
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If you want to use an SRPP circuit for this kind of application the 6DJ8 is a pretty good candidate.

It does I/V conversion nicely and still has enough gain left (considering the SRPP topology).
Load it so you force current flow with say a 1K bleeding resistor at the output , or determine by circuit analysis if you can and you should have low enough Zout with reasonable distortion figures.

After that I'd recommend (as usual) a well regulated, neutral sounding PSU, for best results since all SRPP circuits have low PSRR.

The TDA 1541 provides good symbiosis so results should be sonically pleasing...for a DAC.

Another option is to use a //ed 6DJ8 and CCS that with a J-Fet or similar constant current diode around 30ma with a regged B+ of 24VDC.
Zout will probably be higher than the SRPP circuit but gain will higher too.
One of the advantages of this circuit is that you won't need a raw B+ higher than 40V which allows for used of top of the bill SS* components in the rails. (* Did I just write this?)
I'd need to look at the actual numbers as I'm just writing this from long term memory storage....

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Old 13th December 2008, 09:57 AM   #18
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anyone have experience with AD1865?
Any suggestion?
My best result was with Aikido with 6n1 and 6h6, but I need a bit more gain.
My best result with Tda1545 was with active I/V with ECC86 and LM334 CCS but the current of AD1856 is too low.
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Old 4th February 2009, 12:30 PM   #19
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Default Devas, any new insight into the new UTS option on Satch?

Grateful if you could share....
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Old 28th April 2010, 02:42 PM   #20
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Google brought me here: I'm looking for a new output stage for my TDA1541. I'm using a 28 Ohm I/v resistor with a 6211 SRPP. I am deeply in love with the sound but seriously lack gain. The 6211 is extremely microphonic btw. I was looking for tubes with a mu of around 100 and the 6N2P seemed a good candidate. After reading this the D3a seems a better choice, but I haven't made up my mind yet
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