pjccs or chokes

[kkcinc]

Is it one or the other? I know I already took out the 4k resistors for the pjccs. Now without thinking it through I ordered the chokes. Which sounds better?

[Dr. Toobz]

I've gone back and forth between the two rather extensively, and I have to say that the PJCSS is a lot better than the chokes for two reasons: a) it's more linear across the audio band (whereas the chokes have different amounts of influence at different frequencies, esp. as you get higher), and b) the PJCSS keeps the Quickie very quiet, whereas the chokes pick up hum from surrounding AC sources. The chokes sound more "tubey," leading to a warmer, more compressed sound (and soundstage) as the gain is increased. The PJCSS seems to give a predictable effect at all volume levels.

Both are better than the 4k plate resistors. Essentially, if you want a warmer, more compressed sound, I'd go with the chokes. If you want a clean sound that maximizes gain without adding distortion, the PJCSS is the way to go.

As always, YMMV.

[kkcinc]

Interesting. I don't want to offend anyone, but I immediately lost the magic when I put the pjccs in. Seems more clinical now. I guess I'll try the chokes.

[Dr. Toobz]

The "magic" of tubes seems to be increased second harmonic distortion, IMO. The chokes seem to cause the same effect. I am sort of opposite when it comes to the Quickie: I feel like the sound got overly warm, sludgy and indistinct with the chokes plugged in, even over the resistors, which themselves will have more distortion than the PJCSS. There's clearly some non-linearity at play here with the inductors, which is why I think they've fallen out of my favor.

I suppose one could throw in a DPDT switch and rig both plate loads up - and then switch between the two, depending on the recording, your mood, etc. It's nice to have some customizable options when it comes to sound (even if I'm normally squeamish about tone controls).

[kkcinc]

Great idea!

[Paul Joppa]

I have come to believe there are several dimensions to the "magic" of tube sound, none of which are well understood and many of which we have not identified yet. The virtues of a SE distortion spectrum are widely accepted, whether it is the warmer character or the ability to mask higher-order distortions or the naturalness of the distortion spectrum or some other explanation unknown to modern science is still an open question.

There are other virtues, notably for me an ability to hear low-level and subtle auditory cues. These virtues happen only at signal levels well below the maximum, in which case the distortion is very small and may not be relevant - I think there is something else going on as well. Recent experience with cathode followers (which do have feedback, though not a great deal of it) seems to point to some virtues and vices there sometimes they bring out more detail, and sometimes they muddy or mask subtleties in the music, which seems contradictory.

With respect to Quickie, it does not have a great deal of headroom, so the level of harmonic distortion would be a function of both the circuit components and the signal level. In other words, I'd bet that kkcinc and Dr. Toobz would agree with each other's perceptions if they could listen to each others' systems.

[Dr. Toobz]

More evidence to support the PJCSS over plate chokes: I recently put upgraded parts under the "hood," including low-ESR bypass capacitors (1000uF, 50V) and some unused Solens I had laying around (2.2uF, 400V) in the coupling position. I also realized that I had wired my D cells like the old manual had suggested, which is plainly wrong when looking at the schematic! The mis-wiring leads to obvious bass clipping and distortion much earlier than when the cells are wired in reverse, though this effect is worse with the plate resistors or PJCSS. Finally, I slipped in some NOS 1940's Raytheon tubes I bought online from Tube World. To see which plate load I liked best, I simply ran alligator clips until I had decided what would stay permanently.

Comparing the chokes to the PJCSS: the chokes didn't show much (if any) improvement from the upgrades, but the PJCSS did. The choke's thick sound seems to cover up any subtle improvements in soundstage, noise, etc., because they seem to be adding some hum, increasing harmonic distortion, and collapsing the soundstage (probably for reason #2). They won't be going back in, since experiment after experiment seems to lead me to the same conclusions.

So, the PJCSS it is. The preamp is now dead quiet, with no noise or hum, and it's essentially transparent when plugged in between the SEX amp and Seduction (or Squeezebox). The PJCSS clearly has the latent capacity to take this humble $99 line stage and turn it into something much more refined. FWIW, even though it increases transparency, I also can detect all of the DHT signatures I know: very fine micro-details, natural sounding strings and long decay of instruments like cymbals, and the uncanny ability to make the soundstage 3-D. I'm now hearing things behind my head in some recordings. The chokes seem to hide these details, and it took plate-to-grid feedback to bring them out previously. No, no feedback is needed, and the distortion is still very low.

The PJCSS is a no-brainer if you intend to use this little DHT preamp as a permanent part of your rig.