The all DHT SET Headphone Amp - Page 43 - 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 February 2013, 07:20 PM   #421
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
If I built just like your last schematic except the Rod's Coleman heaters for 4P1L, wich voltages & current is necessary for both B+? I assume 307A heaters 5.5V 1A: simply using a LXXXX or something more sophisticated?
  Reply With Quote
Old 11th February 2013, 07:24 PM   #422
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
Quote:
Originally Posted by 12B4A View Post
Have you tried dialing down the grid leak resistor? Maybe it will pick up less radiated hum.
You mean going with a lower value? Have not tried that yet, but will do so. This prototype is so open air that it is bound to be picking up hum from all over the place.

For a speaker amp with a 25:1 OPT, not a big problem. For a headphone amp with a 5:1 or 4:1 OPT and a lightly driven tube, it's an issue. Gain structure again.
__________________
Take the Speaker Voltage Test!
  Reply With Quote
Old 11th February 2013, 07:40 PM   #423
iko is offline iko  Canada
diyAudio Moderator
 
iko's Avatar
 
Join Date: May 2008
Location: Toronto
Quote:
Originally Posted by merlin el mago View Post
If I built just like your last schematic except the Rod's Coleman heaters for 4P1L, wich voltages & current is necessary for both B+? I assume 307A heaters 5.5V 1A: simply using a LXXXX or something more sophisticated?
If you have the space you want quiet heaters.
  Reply With Quote
Old 11th February 2013, 07:44 PM   #424
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
I have space. Any suggestion?

Last edited by merlin el mago; 11th February 2013 at 07:47 PM.
  Reply With Quote
Old 11th February 2013, 07:45 PM   #425
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
I have seen some neat and simple battery charger curcuits .... why not use large dry cell battery, with a charger
  Reply With Quote
Old 11th February 2013, 09:33 PM   #426
iko is offline iko  Canada
diyAudio Moderator
 
iko's Avatar
 
Join Date: May 2008
Location: Toronto
Hm... I would not use batteries for the filament.
  Reply With Quote
Old 11th February 2013, 10:25 PM   #427
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Blog Entries: 18
This about the tribute 1:2. From Pieter Treurniet. Translated by me.

As you can read from Rob's story. 1:2 Interstages are critical. The source impedance (driver tube) and primary DC current determine the important part of the result.

Therefore it is important to know the application. If things don't go well you'll have drop of the highs below 20kHz and/or dropof of the lows as a result of the combination of Rp and induction of the primary of the IT.

With an 1:2 you have voltage gain; is this really necessary? And with a 1:2 IT you'll halve the current( do you then have enough drive for the final tube?)
With a 1:2 you'll run the risk of lesser results in a particular application.
1:1 IT's are easier in all aspects, especially wrt HF bandwith.

50mA IT's will cost € 240,- per pair ex VAT. They will be poured in an aluminium enclosure (powdercoat black or lightgray) Core material will be 0.05mm silicium iron c-core.

If this concerns a groupbuy some discount may be given. I'm swamped in work until the beginning of april. Somewhere in the middle of april I'll be able to plan in this work.
  Reply With Quote
Old 12th February 2013, 03:25 AM   #428
regal is offline regal  United States
diyAudio Member
 
Join Date: Jan 2004
Location: MD
Quote:
Originally Posted by ikoflexer View Post
I've changed the bias for both tubes. The 4P1L with 240V at about 35mA, and the 307A 360V across at about 38mA. There's been some discussions in other parts of the forum where people talked about the best operating point for the 307a.

Depending on the particular tube you have, the 4P1L may need around -21V on the grid.

For the 4P1L I show fixed bias just to keep the drawing simple, but I would use filament bias with a 32R resistor (650mA filament current). In my opinion it's impractical to do filament bias with the 307a. You'd a 38R resistor that would continuously dissipate 38W, for one tube. So, for the 307a you can choose fixed bias or self-bias as shown in the schematic.

Don't take the values in the schematic as absolutes. In the real world you may have to change some values to get the bias to what you want, especially around the DN2540.
One thing I would ask is the 4P1l isn't going to drive the 307a any where near the grid, so why use the mu output of the driver?

Is the intent that one would precede this headamp with a preamp? In that case we would really have a nice design that will cover all.

What is the Rp of the 307a in triode mode? Anyone know where we can find a spice model of a triode 307a ? The curves look like a mu of 6 which is a nice advantage over the 2a3 and 300b.
  Reply With Quote
Old 12th February 2013, 09:53 AM   #429
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Blog Entries: 18
Quote:
The real secret to the whole thing is the right output transformer. Headphones like Grados/Senns/AKG's will lose low level signals with a big 4 lb transformer. We are talking about the first milliwatt with these types of headphones. I hope this thread brings a few output transformer experts out of the woodwork
Pieter Treurniet has seen this thread. As you may or may not know. Pieter is the owner and winder of Tribute Transformers. He is willing to contribute with his ideas re an output transformer (for instance wrt multiple secundaries to make it more universal as a headphone amp)

But he does need a concrete schematic to be able to do the above.

Last edited by Bas Horneman; 12th February 2013 at 09:55 AM.
  Reply With Quote
Old 12th February 2013, 10:54 AM   #430
iko is offline iko  Canada
diyAudio Moderator
 
iko's Avatar
 
Join Date: May 2008
Location: Toronto
This is what I use for rough work.

* 307a LTSpice model triode strapped
.subckt 307a P G K
CPG P G 0.55p
CGK G K 15p
CPK P K 12p
*koren 8
Bp P K I=(0.01369103481m)*uramp(V(P,K)*ln(1.0+(-0.591620367)+exp((5.574041
845)+(5.574041845)*((6.396026735)+(-4.173415004m)*V(G,K))*V(G,K)/sqrt((-1.840130
29e-005)**2+(V(P,K)-(7.11503529))**2)))/(5.574041845))**(1.704405957)
*koren 5
*Bp P K I=(0.0130446811m)*uramp(V(P,K)*ln(1.0+exp((11.1397 9944)+(11.13979944)*
(6.559627252)*V(G,K)/sqrt((-0.6688132954k)+(V(P,K))**2)))/(11.13979944))**(1.713
912611)
*koren 4
*Bp P K I=(0.01184706113m)*uramp(V(P,K)*ln(1.0+exp((11.132 93476)+(11.13293476)
*(6.572692852)*V(G,K)/V(P,K)))/(11.13293476))**(1.73295172)
.ends 307a
  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
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 09:57 PM.


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