12ax7 srpp dac output - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 11th December 2008, 08:10 PM   #11
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Quote:
Originally posted by Eli Duttman



Kevin,

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.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 11th December 2008, 08:22 PM   #12
devas is offline devas  France
diyAudio Member
 
Join Date: Mar 2004
Location: anywhere out of the world
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.
  Reply With Quote
Old 12th December 2008, 12:32 PM   #13
JC951t is offline JC951t  Taiwan
diyAudio Member
 
Join Date: Sep 2006
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 ?

Thanks
  Reply With Quote
Old 12th December 2008, 03:47 PM   #14
devas is offline devas  France
diyAudio Member
 
Join Date: Mar 2004
Location: anywhere out of the world
Hi,

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.
  Reply With Quote
Old 12th December 2008, 04:05 PM   #15
JC951t is offline JC951t  Taiwan
diyAudio Member
 
Join Date: Sep 2006
Hi devas,

Thanks for your reply. So, you're still running
OS with the Satch & not in NOS mode ?
  Reply With Quote
Old 12th December 2008, 05:06 PM   #16
devas is offline devas  France
diyAudio Member
 
Join Date: Mar 2004
Location: anywhere out of the world
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...
  Reply With Quote
Old 12th December 2008, 10:27 PM   #17
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

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....

Cheers,
__________________
Frank
  Reply With Quote
Old 13th December 2008, 09:57 AM   #18
diyAudio Member
 
Join Date: Nov 2004
Location: Udine
Hallo,
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.
Ciao
Guglielmo
Italy
  Reply With Quote
Old 4th February 2009, 12:30 PM   #19
diyAudio Member
 
Join Date: Sep 2004
Location: hong kong
Default Devas, any new insight into the new UTS option on Satch?

Grateful if you could share....
  Reply With Quote
Old 28th April 2010, 02:42 PM   #20
diyAudio Member
 
Miniwatt's Avatar
 
Join Date: Nov 2004
Location: Den Haag
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
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
SRPP with FETS, what output stage? davidallancole Solid State 18 4th January 2008 05:39 PM
SRPP decoupling cap vs. output transformer matejS Tubes / Valves 4 30th July 2007 10:59 PM
How to figure output Z of SRPP? smbrown Tubes / Valves 13 12th January 2007 03:15 PM
6as7 SRPP output stage Molloy Tubes / Valves 4 15th September 2006 05:39 PM
Lowering gain in 12AX7 SRPP preamp net-david Tubes / Valves 26 23rd December 2003 05:55 PM


New To Site? Need Help?

All times are GMT. The time now is 01:16 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2