My New PV6 (Redirected)

[Tuggs]

New to the site and CJ membership. As I posted in my introduction thread, I bought a mint condition PV6. Came all the way from the right to left coast, thankfully unscathed. Running it in, I only noted two discrepancies.

First was a mildly microphonic tube in the phono left channel. Not discernable with music playing, but when I turned the balance or volume knobs or tapped the faceplate, I'd hear a glassy tink only from the left. Roberto was kind enough to provide some advice, helping to confirm what I was seeing on the schematic, btw courtesy of this site!

Gently tapping on each tube told me it was the 12AX7 in position V1. The only other markings on the tube were "Yugoslavia" and six cyrillic letters towards the base. From what I learned of the seller, these are most likely the original tubes.

The seller sent along a spare tube set from CJ. However, the "new" 12AX7 had a fairly noticeable tube rush in the right channel. So I went looking for my scrounge box of tubes to see what I had. Disclaimer: I don't have a very reliable auditory memory. The only time I'll fall on a sword is when I can hear differences during an A/B comparison.

First in was a Sylvania; it was okay, but didn't seem to have quite the liveliness of the Yugo. Next in was one of two GEs; not much different at all from the Sylvania. Neither of the above had any electromechanical issues I could detect, they just didn't wow me.

Finally I tried each of my two Mullards; neither was microphonic nor did they exhibit tube rush. One sounded great with a very light amount of hiss and hum evenly between both channels (ear against the speaker). The other sounded great as well, but was even quieter. Bingo!

The other discrepancy was the well-documented muting relay. I popped off the clear cover, put a strip of paper between the two contacts, then lightly saturated the paper with Deoxit, and went back and forth to clean the contacts. Topped it off with gently spraying the electromagnet and armature hinge point with Deoxit. Cleaned off the area, let it sit for a few, reinstalled the relay's cover, then powered up the preamp. Problem solved.

As I mentioned in my intro post, I find the PV6 to be quite revealing, realistic, with a "front row" presentation. It doesn't sound dated, sluggish, rolled off, bass-deficient, or excessively warm to me at all as it does to some others; kinda perplexing. Regardless, I'm loving this PV6.

[admin]

Glad to hear you got it all figured out and running up to spec. I find that with tubes it's going to be a lot of trial and error to find which ones sound the best.

[roberto]

Hola Tuggs,

Those are great news. As Admin said, good job!. I think that the tubes are very temperamental and some times microphonic. But, with all their issues, they are winners in warmth and detail. They are crispy and clear at the highs, a warmth in the midrange where the vocals, strings and solo instruments are. They are projected with a superb realism. Also, I love the bass. Conrad Johnson just sounds right!.

These CJ products use top of the line parts. I want to add one more thing: quality has no regret!

Happy listening!

[david1111]

New to the site and CJ membership. As I posted in my introduction thread, I bought a mint condition PV6. Came all the way from the right to left coast,

I have a PV-5 tuggs, and from what I've read, the 5 and 6 are very similar. And I also am loving the sound of it.
I just recently replaced my Adcom GFA 555ii amp with an Ayre V-3 amp, and I gotta say, the change really made my Kef 107s sing. The Ayre seems to be a very good match for the PV-5.
There's a bit of a mix of tubes in my PV-5, and at some point I'll roll in some other tubes to test, but it would be great to hear from some other PV-5 or 6 owners, and hear what they recommend.
I listen to older (real) classic rock, classical, jazz, and female vocal.
Anyway, happy listening.

Dave

[plurn]

...
First was a mildly microphonic tube in the phono left channel. Not discernable with music playing, but when I turned the balance or volume knobs or tapped the faceplate, I'd hear a glassy tink only from the left.
...

That glassy tink/ting sound can be normal for some older produced tubes due to their design they can be more susceptible to get this tink issue. Though it is more common with 6922 family of tubes rather than 12AX7. It is not necessarily microphonic though a lot of people think this is what a microphonic tube is. When a tube is microphonic it will get a feedback-like high-pitched sound just from sound in the air and is completely unusable.

If that tube otherwise sounds fine playing music you can probably still use it (or keep is as a backup or for testing/troubleshooting) unless it is really annoying for you. At least you won't be using it in the newer CJ preamps that have clacking relays for adjusting volume - with them you get tink tink tink tink tink constantly as you adjust the volume.

If you avoid all tubes that have this tink sound, you will be missing out on a lot of good vintage tubes.

I have found one thing that can help reduce the tink is using a bunch of those rubber tube rings around the base of the tube to sort of couple it to the tube holder in the circuit board. Might seem counterintuitive to couple it to the board rather than try and isolate it from the board but it seems to help.

multiple tube dampers

tubedampers.jpg (89.18 KiB) Viewed 1247 times

[roberto]

Hola Plurn,

When you tap a tube, it is microphonic. When you have a high pitch feedback, the tube must be replaced, because it is bad. Also, noisy tubes must be replaced. Great idea to isolate the tube from resonating with the rubber rings, including the tube base, (microphonic-slang).

This is what the electronic encyclopedia says about microphonic tube: Microphonics describes the phenomenon where a tube transforms mechanical vibrations into an undesired signal (noise or feedback). Due to the mechanical construction all tubes exhibit some inherent microphonic tendencies.

So, is you tap at the top cover or at the front of the preamplifier and you hear an undesired noise, you have a microphonic tube too. When you have a horrible feedback, of course you do have a microphonic tube, and this must be replaced.

Perhaps you are right saying that a microphonic tube is the one that makes a feedback, yes, this is a truth. With a tink/ting, maybe the tube is still usable, but you will be having a compromise. You can do the test with similar tube number and check if you have the problem...you might find the non tink/ting tube.

Happy listening!

[Tuggs]

I'd tend to agree with both comments, insofar as I have not thrown away the Yugo 12AX7, because it wasn't to the point of causing any feedback. It only made itself known when I turned a pot or accidently tapped the chassis. Because of that, I'm keeping it around for a rainy day, or troubleshooting as mentioned.

To david1111, the tubes that came to me in this PV6 are as follows:
V1 Phono – Yugo 12AX7 (now Mullard 12AX7 I61)
V2 Phono – GE JAN-5751
V3 Phono – 12AT7WC no name
V4 Line – GE JAN-5751
V5 Line – GE JAN-5751
V6 Line – 12AT7WC no name

[david1111]

I'd tend to agree with both comments, insofar as I have not thrown away the Yugo 12AX7, because it wasn't to the point of causing any feedback. It only made itself known when I turned a pot or accidently tapped the chassis. Because of that, I'm keeping it around for a rainy day, or troubleshooting as mentioned.

To david1111, the tubes that came to me in this PV6 are as follows:
V1 Phono – Yugo 12AX7 (now Mullard 12AX7 I61)
V2 Phono – GE JAN-5751
V3 Phono – 12AT7WC no name
V4 Line – GE JAN-5751
V5 Line – GE JAN-5751
V6 Line – 12AT7WC no name

Thanks for the tube info Tuggs. Sorry for the late reply, it's been a very busy August for me. I'll check these against my tubes.
Cheers.

Dave