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The all DHT SET Headphone Amp
The all DHT SET Headphone Amp
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Old 2nd February 2013, 08:07 PM   #171
andyjevans is offline andyjevans  United Kingdom
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Well, I've built quite a few line stages with DHTs by now. All different kinds - 10Y, 46, 01A, 3a5, 71A, 12A, long list. My preference swings between the 4P1L and 26 depending on the implementation. I'm a very big fan of Anatoliy's work - he's a pioneer - and I haven't built and heard his circuit. But I can't agree with "zero advantage of DHTs". My current favourite input stage has swung back to the 26, as shown in the schematic. If I was to build right now, I'd use this stage into a 4P1L stage in filament bias. It really has a bit of magic about it for me - the 26 can do that.
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Old 2nd February 2013, 08:22 PM   #172
Wavebourn is online now Wavebourn  United States
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The all DHT SET Headphone Amp
I mean zero advantage when maximal swing of anode voltage required is about 20 volts, and the tube will never go into cut-off region because output tube will saturate way before that happens.
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Old 3rd February 2013, 05:23 AM   #173
regal is offline regal  United States
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Quote:
Originally Posted by Wavebourn View Post
I mean zero advantage when maximal swing of anode voltage required is about 20 volts, and the tube will never go into cut-off region because output tube will saturate way before that happens.
Correct that is what I am saying about the fact that we want this DHT headphone am to have an advantage over what I call the "spud" SET headamp.

I conside the spud the "competition" as it remains an excellent performer, several of us on this forum built variations on the them when the SSHV came out.

Bassically just a common cathode stage with a super tube (WE417, 6c45pi, d3a,or cg3, etc). Uses LED bias and an SSHV and there literally are no caps in the signal path, about the purist SET sound you can get, but they tend to start to have too much distortion around half a watt.



Now we are "back" to DC coupling make sense with our the DHT SET, Wavebourn hass done an excellent job explaining why the preferred method here is to DC couple.

I found a "negative" version of the SSHV that could make this easier (attached). Also looks like a gyrator mu output loaded 4p1l can drive a 4p1l into A1. One could install a switch to where high efficient phones get the plate output and the inefficient phones get the mu output. (sort of like the p-p guys with their triode/ultra-linear switch.)


What are the thoughts of using two 8 ohm windings on the opt transformer's winding to give 5k:32 ratio balanced ouput? Its a way to get away from the high DCR/inductance of a headphone secondary.

Could have several outputs: high efficient phones/speakers get the two 8 ohm secandaries in parallel, while the low efficiency jack could be a "balanced" 32 ohm output.

Also check out the loctal sockets I found on ebay. Can the 4P1L re run upside down?
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File Type: png MirrorSSHV1.png (33.4 KB, 300 views)
File Type: jpg $(KGrHqZ,!qgE-y+Ppm)yBP1PgICK0Q~~60_12.jpg (26.2 KB, 291 views)

Last edited by regal; 3rd February 2013 at 05:35 AM.
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Old 3rd February 2013, 11:03 AM   #174
merlin el mago is offline merlin el mago
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Originally Posted by regal View Post
Also check out the loctal sockets I found on ebay. Can the 4P1L re run upside down?
It seems can run upside down, inside locatal sockets are the same that I have on hand.
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Old 3rd February 2013, 01:45 PM   #175
Stixx is offline Stixx  Germany
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Quote:
Also check out the loctal sockets I found on ebay. Can the 4P1L re run upside down?
Rather uncommon to run a tube upside down I understand horizontally mounted, but pointing down? What about the heat issue?

And those are ugly loctal sockets... hiding most of the tube although I doubt that the 4P1L will fit inside. When you need good loctal sockets... Germany has a good supply of them new. Can send you some...
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Old 3rd February 2013, 01:50 PM   #176
45 is offline 45  Italy
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Quote:
Originally Posted by andyjevans View Post
If I was to build right now, I'd use this stage into a 4P1L stage in filament bias. It really has a bit of magic about it for me - the 26 can do that.
I think it is a good idea for low power SE amp because the 4P1L is quite efficient and does not need a big swing like the 45 (which is better used in PP for me! )
Have you tried the 4P1L at full power, something like 250V/32 mA into 5K OPT and the 26+IT?

Last edited by 45; 3rd February 2013 at 01:53 PM.
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Old 3rd February 2013, 01:57 PM   #177
dennis h is offline dennis h  United States
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Regal says...
"Correct that is what I am saying about the fact that we want this DHT headphone am to have an advantage over what I call the "spud" SET headamp.

I conside the spud the "competition" as it remains an excellent performer, several of us on this forum built variations on the them when the SSHV came out.

Bassically just a common cathode stage with a super tube (WE417, 6c45pi, d3a,or cg3, etc). Uses LED bias and an SSHV and there literally are no caps in the signal path, about the purist SET sound you can get, but they tend to start to have too much distortion around half a watt."

Regal,
Are there any discussions of this here @ DIY that you could pont me too ?
thanks in advance,
dennis h
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Old 3rd February 2013, 02:16 PM   #178
Pano is offline Pano  United States
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The all DHT SET Headphone Amp
Quote:
Originally Posted by 45 View Post
Have you tried the 4P1L at full power, something like 250V/32 mA into 5K OPT ...
Yes - see the other thread. Today I will try to determine what the optimal load is for the 4P1L triode strapped SE. 8K? 5K? 3K?
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Old 3rd February 2013, 02:18 PM   #179
Rod Coleman is offline Rod Coleman  United Kingdom
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I make it at about 5300 ohms -

please see:

http://www.diyaudio.com/forums/tubes...ml#post3352853
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Old 3rd February 2013, 04:18 PM   #180
regal is offline regal  United States
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Quote:
Originally Posted by dennis h View Post
Regal says...
"Correct that is what I am saying about the fact that we want this DHT headphone am to have an advantage over what I call the "spud" SET headamp.

I conside the spud the "competition" as it remains an excellent performer, several of us on this forum built variations on the them when the SSHV came out.

Bassically just a common cathode stage with a super tube (WE417, 6c45pi, d3a,or cg3, etc). Uses LED bias and an SSHV and there literally are no caps in the signal path, about the purist SET sound you can get, but they tend to start to have too much distortion around half a watt."

Regal,
Are there any discussions of this here @ DIY that you could pont me too ?
thanks in advance,
dennis h
http://www.diyaudio.com/forums/headp...plifier-2.html

Spud amps

http://www.diyaudio.com/forums/tubes...rmal-tx-7.html

Most moved to LED bias the cathode, a lot of us have sort of secretly built these high gm shunt regulated spud headamps. You learn the hurdles of creating that black background required for sensitive phones like grado and beyer. These readings are a good pre-requisit for this DHT project. Note I don't think there was ever a consensus between para-feed vs single feed. Adamus had one of the nicer builds.

They generally run out of steam with much more than 1/4 to 1/2 a watt. But sound absolutely top notch with high end Grados, Beyers, and Senns.

Attached is mine ( I wonder if E-print would rewind my 5k:32 OPT's with a bigger gap for a DHT output?)
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