Home Tube DIY Asylum

Do It Yourself (DIY) paradise for tube and SET project builders.

Re: Interesting.

Hi c-J,

Before you 'jump into conclusions' as I did when I first saw these graphs, maybe it is good to read part of a private e-mail conversation I had with TL about this (which he told me I could share).

Thorsten wrote:

First the graphs from the above, the perspective makes it difficult to see, but the peak at the 5th Hamrmonic at lower power levels on 417A and EL84) is from output valve (not sure why it did that, but it sure did), so if you do not see a distinct peak-up to the 5th it means the driver produces more 5th than the output did.

The 6SN7 cascade always does more distortion even at high orders than the 300B, in effecting swamping out the 300B's distortion, but it adds some more of it's own at the 5th causing that peak in the 2.5W graph.

When comparing the spectra I felt that the EL84 (and C3m) provided the most evenhanded (and low high order) distortion overall, arguably the 6SL7 SRPP is second and IMHO better than the 417A (same trend with 437A) purely from a harmonic profile.

That said I liked the various pentode driven 300B Amp's I have build about equally well as the 417A/437A/6S45/E180F/E810F/D3a TWGC Amplifiers (TWGC - Triode With Gridchoke), all BTW using rather low anodic current, usually around and below 10mA in the driver, feeling they offered a similar overall performance levels.

No, they do not sound alike, either between Pentode or Triode nor among the different types, but they share some overall charateristics, with the Pentodes offering more "Tone" and "Delicacy" while the Triodes tend towards "Detail" but also directness and notably greater macrodynamic robustness (maybe gridchoke plays a role here, they are not easily used with pentodes).

Compared to that the 6SL7 SRPP (with or without gridchoke, also when connected as mu-follower which I thought best) seems a little "further away from the music" sorta like "through a glass, darkly", giving a certain sameness to varied music, more so than the others).

The 6SN7 cascade seemed to combine the worst of all worlds, managing to sound opaque, without variation in the music (making all sound the same) while giving me headaches with edgyness at the same time. Didn't care for that at all.

A cascade with 6072A & 5687WB sounded more balanced and had more immediacy and directness, but not quiet up to the single pentode or triode levels.

Not sure if any of this of use.

I'm currently working (extremely slowly) on a topology provisionally called "Bushido" which aims to combine the best sonic features of the pentode driven amplifiers (the "delicacy", "lightness of touch", "speed" (whatever we want to call it) and the nice "tone" with the macrodynamic cojones of the "TWGC", it might see the light of day at some point.

Ciao T

Regards,
NC


This post is made possible by the generous support of people like you and our sponsors:
  Amplified Parts  


Follow Ups Full Thread
Follow Ups


You can not post to an archived thread.