Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

The all DHT SET Headphone Amp
The all DHT SET Headphone Amp
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 7th February 2013, 01:13 PM   #281
Rod Coleman is offline Rod Coleman  United Kingdom
работник
diyAudio Member
 
Rod Coleman's Avatar
 
Join Date: Jul 2004
Location: Warwickshire UK
The all DHT SET Headphone Amp
Serving suggestion for 4P1L - 2A3 dc coupled.

to keep Anatoliy happy, the 2A3 anode current servos the operating current of the shunt cascode, to give dc-stabilised operating point.

2A3 needs -100V bias supply (10mA), but this does give a startup voltage of -100V, to be kind to the 2A3.

Darlington connected PNP shown. NXP Semiconductors PBHV9040Z assumed for main PNP. others are -T package (SOT23) - so yes, PCB needed for correct layout.

To keep the 400mV (pk) sensitivity, the gain of the shunt cascode is increased to 62, to allow for the low mu of the 2A3. It's the beauty of shunt cascode - you can set the gain independent of the stage's triode current.
Attached Images
File Type: jpg 4p1L_2A3_dc.jpg (148.7 KB, 308 views)
Attached Files
File Type: zip 4P1L_2A3_dc.asc.zip (144.3 KB, 33 views)
  Reply With Quote
Old 7th February 2013, 01:53 PM   #282
jpak is offline jpak  United States
diyAudio Member
 
jpak's Avatar
 
Join Date: Jun 2007
Location: CT
I'm interested in the 4p1l-4p1l amp. The tubes are much cheaper than 2A3, and some of us don't really need more than .5 w.
  Reply With Quote
Old 7th February 2013, 03:11 PM   #283
cotdt is offline cotdt  United States
diyAudio Member
 
Join Date: Oct 2005
Send a message via AIM to cotdt
very cool...
  Reply With Quote
Old 7th February 2013, 04:27 PM   #284
Stixx is offline Stixx  Germany
diyAudio Member
 
Stixx's Avatar
 
Join Date: Sep 2003
Location: Southern Germany
Quote:
I'm interested in the 4p1l-4p1l amp. The tubes are much cheaper than 2A3, and some of us don't really need more than .5 w.
I second that...
There is also two 71A lurking in my drawers...
although I'm sure a basic schematic from this thread could be adapted to use other output tubes, as different transformers suiting different headphone impedances could be employed (has been said before).
  Reply With Quote
Old 7th February 2013, 04:38 PM   #285
Radium is offline Radium
diyAudio Member
 
Join Date: Feb 2012
Location: Hyperspace
The thread is most interesting, almost a perfect match with what I have in mind. There is one unusual option not considered yet (unless I missed it). Sorry if it crosses some unseen lines in the sand or is plain silly.
If the DAC is made an integral part of this design, and its I/V conversion circuit (with HV OPAMP) set to swing the required grid voltage precisely, the DHT part could be reduced to a single 2A3. Also the interstage capacitor could be eliminated.
What do you think?
  Reply With Quote
Old 7th February 2013, 04:57 PM   #286
merlin el mago is offline merlin el mago
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
Originally Posted by jpak View Post
I'm interested in the 4p1l-4p1l amp. The tubes are much cheaper than 2A3, and some of us don't really need more than .5 w.
Quote:
Originally Posted by Stixx View Post
I second that...
There is also two 71A lurking in my drawers...
although I'm sure a basic schematic from this thread could be adapted to use other output tubes, as different transformers suiting different headphone impedances could be employed (has been said before).
If can drive Sennhs HD 600 me too.

jpak
Stixx
merlin el mago
  Reply With Quote
Old 7th February 2013, 05:10 PM   #287
iko is offline iko  Canada
diyAudio Moderator
 
iko's Avatar
 
Join Date: May 2008
Location: Toronto
The all DHT SET Headphone Amp
I thought that's been covered. A classic two stage 4P1L->4P1L should be fine for most headphones, provided you use the right output transformer. The first stage can use a gyrator load like I showed earlier, or a choke load, or the primary winding of an interstage transformer if you have the financial motivation to buy a good one. The output stage is simple, a 4P1L and the output transformer. The operating points are easy to calculate once you decide which parts you want to use. If you want it DC coupled, that's doable too, as I've shown earlier in a schematic. I've left some details out, but it's easy enough to figure those out.

To improve on that, keeping it simple, one can use 2A3 or 6S4S in the output. Or, if you can find it, the 307A. That's what I'm planning to build 4P1L->307A, first gyrator load, AC coupled, output transformer, and then later try an interstage transformer.
  Reply With Quote
Old 7th February 2013, 06:20 PM   #288
45 is offline 45  Italy
diyAudio Member
 
45's Avatar
 
Join Date: Dec 2008
Location: UK
Quote:
Originally Posted by Radium View Post
The thread is most interesting, almost a perfect match with what I have in mind. There is one unusual option not considered yet (unless I missed it). Sorry if it crosses some unseen lines in the sand or is plain silly.
If the DAC is made an integral part of this design, and its I/V conversion circuit (with HV OPAMP) set to swing the required grid voltage precisely, the DHT part could be reduced to a single 2A3. Also the interstage capacitor could be eliminated.
What do you think?
I think that the 2A3 in general is not linear enough for this application. Regardless of the overall gain, at low output level distortion will always be a bit too much in you don't use feedback. Maybe you can find some 2A3's that are better than average but this means you cannot buy just two of them or two of them without tight selection. More likely you will get a colored sound. Pleasant as you want but not truly High Fidelity. 4P1L is better.
The urge for a Pout of 1W or more is not reasonable if you cannot have more important characteristics...
  Reply With Quote
Old 7th February 2013, 06:27 PM   #289
cotdt is offline cotdt  United States
diyAudio Member
 
Join Date: Oct 2005
Send a message via AIM to cotdt
2A3 are extremely linear! I've seen such beautiful curves measured of them!
  Reply With Quote
Old 7th February 2013, 06:39 PM   #290
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
The all DHT SET Headphone Amp
Quote:
Originally Posted by cotdt View Post
I've seen such beautiful curves measured of them!
sexy things sorry, couldn't resist it
  Reply With Quote

Reply


The all DHT SET Headphone AmpHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
High end Ortho Amp on a basic Russian Tube DHT SET DIY design regal Headphone Systems 2 7th December 2012 11:46 AM
300b all-DHT SET andyjevans Tubes / Valves 16 24th August 2012 08:06 PM
Help on designing full DHT SET power amplifier milen007 Tubes / Valves 56 11th August 2011 09:38 PM
Class A, DHT driven, headphone amp iko Headphone Systems 100 26th March 2011 02:54 PM


New To Site? Need Help?

All times are GMT. The time now is 01:51 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki