Anyone try DHT 33 or 1Q5 Pentodes wired as Triode? - diyAudio
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Old 2nd April 2013, 05:26 PM   #1
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Default Anyone try DHT 33 or 1Q5 Pentodes wired as Triode?

Can get some from a local electronic surplus store.
They would be set up as SE for a preamp.
How would it compare to 1H4 or 30?

Thanks
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Old 27th May 2013, 03:56 AM   #2
TheGimp is offline TheGimp  United States
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Triode strapped I get a Mu of about 4.45 at 18mA. At 3ma it drops to 4 even (ande voltage 180, current source loaded).

Right now I can't drive it much beyond 11Vrms out as my source only goes to 2.56Vrms.

Distortion at these levels looks encouraging.

I have no 1H4 or 30s to compare to.
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Old 30th May 2013, 02:46 PM   #3
TheGimp is offline TheGimp  United States
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I took some distortion measurements last night after I finally got my ground problem corrected.

With 120Vp-p out (good enough to drive a 6A3) I measured 0.278%THD


3rd harmonic was about 22dB below 2nd Harmonic. Nice waterfall fall off in harmonics.

Ia=6ma
Vak=179V
Vgk not measured.
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Old 18th November 2013, 02:40 AM   #4
HeyBill is offline HeyBill  United States
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Default 1Q5 measurements

Hello all,

I'm working on a 1Q5 triode strapped driving a 45 SE. The original idea came from an article in Glass Audio regarding harmonic cancelation. The author was Larry Lisle (sp). The coupling is RC rather than IT in the original design. Not sure I'll have the drive needed.

Batteries for the 45 and 1Q5 heat and fixed bias). All without the help of 1Q5 triode curves. The 1Q5 bias is adjustable to cancel distortion in the 45.

I picked up some W8-1808's for an open baffle that should be able to work with the flea power, assuming the amp works.

My last (second) build was a pair of 6A3 A2 monoblocks that used to be on the ElectraPrint site. Lots of power, very nice. Best Regards, Heybill
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Old 18th November 2013, 01:00 PM   #5
TheGimp is offline TheGimp  United States
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How are you measuring harmonics?

My experience with harmonic cancellation was: (1) that odd harmonics were more difficult to cancel ( Iiirc math can be used to show this), (2) cancellation was very bias dependant, especially on the bias of the output tube, (3)Amps sound better with a nice watterfall of harmonics rather than disjoint decaying amplitudes (supported by psychoaccoustics).

I was using a 6P41S SE in triode mode as well as UL mode.

I'll be interested to see how your results compare to mine.
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Old 19th November 2013, 12:02 AM   #6
HeyBill is offline HeyBill  United States
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TheGimp,

Think I'll spend the money on a 339A. Just did the listen test on my last build. If this experiment does nothing else, I'll learn something about SE, fixed bias, and measuring harmonics. Thank you for the wisdom.

Regards, HeyBill
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Old 30th April 2014, 07:02 PM   #7
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I tried the 1Q5 in triode mode recently...
Very nice sound... clean, clear and "sounds" natural. All this after you get them to stop ringing like a Hollywood haunted house recording... Now I know how they did those sound effects in the movies
According to the data sheets... 5-6.5% THD in pentode mode.
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Old 30th April 2014, 07:25 PM   #8
HeyBill is offline HeyBill  United States
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Default 1Q5 triode mode

rcollege,

Just about to finish up on the 1Q5 breadboard. I recently ordered a used Keithly analyzer (Parts Connexion) so that I can see how the harmonic cancellation works. Thank you for the feedback on the ringing. Can't be much worse than my ears.
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Old 30th April 2014, 10:19 PM   #9
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Quote:
Originally Posted by HeyBill View Post
rcollege,

Just about to finish up on the 1Q5 breadboard. I recently ordered a used Keithly analyzer (Parts Connexion) so that I can see how the harmonic cancellation works. Thank you for the feedback on the ringing. Can't be much worse than my ears.
LOL!

Well, they went from ringing a fine crystal glass to a siren singing from the depths of an abyss. Smooth as silk all the while.

I will have to check the Plate voltage... I fear they may have been crying from too many V's on their plates and screens
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