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   Home » Melquiades Amplifier » The DHOFT topology? Do not try it home. (4 posts, 1 page)
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  »  New  Single-stage Melquiades vs. DHT amps..  A hallucination?...  Melquiades Amplifier  Forum     397  2597843  11-22-2008
05-04-2009 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,545
Joined on 05-28-2004

Post #: 1
Post ID: 10426
Reply to: 10426
The DHOFT topology? Do not try it home.
fiogf49gjkf0d

I know – it idiotic even for my site but it us what it is. I do not think that I can generalize my observations as I have not a lot of experience with DHT tubes but one thing that I have been observing for the last week is really arouse my curiosity.

Well, it is funny to say but I think I “invented” a new “topology”- the DHOFT.

Let me to explain. During the last few days, cooing the MF DH Melquiades channel I have the MF channel better or worse operational. It use 10 feet horribly sounding Rat Shack cable running form my preamp and it used even more horrible 25 feet speaker cable to drive my S2 driver. The tube is plugged upside down, the part up to the last time were crap, so it was not the environment to access the “quality” of the tubes. Sure, I did not do it but… being sick audio retard I would lie to you if I say that I did not try a few “other” tubes to see “what thus straight people are raving all about.”. So, I plugged into it 2A3, Russian, Chinese, RCA, Sylvania, 6A3 RCA and Westinghouse, Telefunken RE604, Klangfilm KL71403, YO186 and few of off the wall tubes that I bought last week at MIT fleemarket. I intentionally did not comment on the sound as I am not at the state with this amp where would accept my observation seriously. However, during those experiments I go a very rudimental idea what those tubes stay in thir hierarchy of quality…

Two weeks ago I was experimenting with operational point of the output stage (during the experiments I use of course cheap test tubes). I did screw up some with ground and accidently connected the Chinese 2A3 with shunted cathode resistor. So, it was 400V on anode with no bias of any kind p you have an idea what currant it took. I turned the amp and then was distracted by something. In few minutes (!!!) I was observing gray smoke in my room and I run to the amp. The powers supplies 20W resistors on 400V were literally boiling. I would be hard to explain how the 2A3 looks like. The anode was not just red and hot but it was shining like “one million Suns”. I shut down the amp, replaced the burned restore and   tossed out the destroyed Chinese 2A3, reporting to my friends that one more tube fold to be the victim of my DIY efforts…

Yesterday, I cleaned up my room, trashed all the needles crap and I come across to that killed tube. Before disposing it I asked myself: way not to see if the type will work. I plug it is, and it give the right current. It is alive I figured and decided to listen. The tube sound unbelievably good – better then any of my other tubes – I am not kidding! I took another Chinese 2A3 with witch the “burned” tube were paired and sound identical before the “ignition” and they now sound like  day and high.

Well, I do not know what practical use this information would give but sine I “invented” the concept I will name it. I would call it the DHOFT topology or the “Direct Heated Over Fried Triode”. So, if some of you paid $800 for a new AD1 and if you like how it sound then try to put your AD1 to 600mA for 3 minutes and it sound might  go over the roof…

Despite that I was kidding in my last paragraph but the sound of the Chinese DHOFT 2A3 after the “ignition” does puzzles me….

The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
05-05-2009 Post does not mapped to Knowledge Tree
JJ Triode
Posts 75
Joined on 09-12-2007

Post #: 2
Post ID: 10427
Reply to: 10426
Stir-fried Shuguang 2A3C?
fiogf49gjkf0d
I thought already the Shuguang was a good-sounding and apparently well-made tube, probably quite rugged electrically, but I never would have thought it could survive what you just described, much less sound better!  It is a good thing the base is ceramic, as plastic would probably have melted and made a fine mess.  What did Koshka think about it?
05-06-2009 Post does not mapped to Knowledge Tree
cv
Derby, United Kingdom
Posts 173
Joined on 09-15-2004

Post #: 3
Post ID: 10449
Reply to: 10427
That fried 2A3C....
fiogf49gjkf0d
I have some theories...*please* keep this tube safe, we will have to run some curves on it...
More importantly, it's a good thing the output transformer wasn't damaged, though I'd imagine the tube would have struggled to pass more than around 600mA anyway.

Cheers
cv
05-06-2009 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,545
Joined on 05-28-2004

Post #: 4
Post ID: 10451
Reply to: 10449
A medley of slow-cooked triodes.
fiogf49gjkf0d

 cv wrote:
I have some theories...*please* keep this tube safe, we will have to run some curves on it...
More importantly, it's a good thing the output transformer wasn't damaged, though I'd imagine the tube would have struggled to pass more than around 600mA anyway

Yes, Chris, it would be interesting to expose this tube to some kind of  testing and to correlate it with it’s not-fried sister but it shell be done by not my mind as I would not be able to interpret the curves.  I have no idea what practical benefits it might have, unless you are willing to open a “tubes cooking” service. If you do them I would starts an insurance company… :-)

Sonically, the fried tube got a very interesting sound. The biggest difference is in a way HOW they approach HF – it is type Sound that I never heard in audio before. My “cooked 2A3” kind of enters the HF region “invisibly” and it is very difficult to say where the HF starts.  It is like you have some kind of MF pitch and in few seconds you realize that Sound moved up abut you do not have feeling “when” and “how”. It kind of very interesting feeling, not to mention that the HF themselves got WAY more extended and more sophisticated.

The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
Page 1 of 1 (4 items) Select Pages: 
   Target    Threads for related reading   Most recent post in related threads   Forum  Replies   Views   Started 
  »  New  DHT driver & input..  Effects of radiation...  Melquiades Amplifier  Forum     25  167801  02-01-2007
  »  New  The Melquiades bass channels: the coupling capacitor...  bias continued...  Melquiades Amplifier  Forum     11  85419  08-13-2007
  »  New  A contemporary AD1 Triode by Emission Labs..  Yamamoto, AD1 and no talk about time-alignment....  Audio Discussions  Forum     6  68144  10-12-2007
  »  New  Single-stage Melquiades vs. DHT amps..  A hallucination?...  Melquiades Amplifier  Forum     397  2597843  11-22-2008
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