What is the theoretical advantage of direct heated triodes?

[Chris Hornbeck]

If you want to try 'em for yourself, and are concerned with the twice line frequency modulation by AC filament heating, run two valves in parallel with their filament connections opposing. The real challenge with DHTs is getting enough isolation from AC power line garbage, while still making the "cathode" unipotential to signal. Lots of folks have given up and gone to DC heating. But never say die!

All good fortune,
Chris

[Tony]

why is it that i find my EL34 pp amp sounding better than a 45 set? mi had a chance to listen to both of them side by side at a recent hifi show...

[cotdt]

Originally Posted by Tony

why is it that i find my EL34 pp amp sounding better than a 45 set? mi had a chance to listen to both of them side by side at a recent hifi show...

could be many reasons, personal taste, 45 clipping at volume, etc. there is a huge difference in output power between the amps.

in my system, all my friends and family prefer the SET. i could not find a single person prefering the PP EL84 amp. could be many reasons, such as cosmetics or something.

[Shoog]

Originally Posted by cotdt

could be many reasons, personal taste, 45 clipping at volume, etc. there is a huge difference in output power between the amps.

in my system, all my friends and family prefer the SET. i could not find a single person prefering the PP EL84 amp. could be many reasons, such as cosmetics or something.

Was the PP EL84 run in Triode class A with ZNFB, otherwise the comparison is not fair. This is the problem with comparing totally different topologies - people rarely build the PP amps to the same standards as the SET amp and then wonder why they sound different.

Shoog

[TVC]

Originally Posted by Tony

why is it that i find my EL34 pp amp sounding better than a 45 set? mi had a chance to listen to both of them side by side at a recent hifi show...

---------------------------

I also had this experience before, SE tube amp had rich 2nd harmonic, the EL34PP I heard had very fast ,detail sound which different than other PP amp I heard was the same with rich second harmonic.

[Vinylsavor]

Hi!
With all plate curve measurements I did, DHTs have been more linear than IDHTs. Especially in comparison to triode strapped pentodes. There had been some experiments done by S. Bench, comparing IDHTs to DHTs and DHTs with oxide and thoriated tungsten filaments. He measureed the change of mu with signal ampltitude. In this test the DHTs had mroe constant mu and among DHTs those with thoriated tungsten filaments had been better

Best regards

Thomas

[Tony]

Originally Posted by cotdt

could be many reasons, personal taste, 45 clipping at volume, etc. there is a huge difference in output power between the amps.

in my system, all my friends and family prefer the SET. i could not find a single person prefering the PP EL84 amp. could be many reasons, such as cosmetics or something.

i find sets too whimpy for my tastes....the speaker we used was a modified Sony 4 inch FR in a transmission line box......we played Joe Morello's take 5 at volume and one guy came up to me and asked me, where did you put your subwoofer? he was flabbergasted to find out that all we had was a 4incher.......

[Tony]

Originally Posted by TVC

---------------------------

I also had this experience before, SE tube amp had rich 2nd harmonic, the EL34PP I heard had very fast ,detail sound which different than other PP amp I heard was the same with rich second harmonic.

with a Broskie CCDA line preamp, the EL34 pp amp sounded better than the 45 set with plenty of volume to boot....

[Tony]

Originally Posted by Shoog

Was the PP EL84 run in Triode class A with ZNFB, otherwise the comparison is not fair. This is the problem with comparing totally different topologies - people rarely build the PP amps to the same standards as the SET amp and then wonder why they sound different.

Shoog

ultralinear pp shuguang EL34 shuguang tube amp.....with global negative feedback......i do not know what the standards for SET amps are, but i do know what i heard and i liked it.....

[SY]

Originally Posted by jlsem

What is the standard for measuring microphonics and where can the data for commonly used tubes be obtained?

Data and procedures are generally only given for tubes with specified low microphonics. It's sorely lacking for others. As far as I'm aware, there is no one universal standard.

edit: Here's an example of one where the procedure is specified and data are given:
http://tubedata.milbert.com/sheets/138/6/6111WA.pdf

Here's an example where the claim is made, but with zero supporting data:
http://tubedata.milbert.com/sheets/079/5/5879.pdf