Re-tubing my PV-8

[grantn]

I just acquired a used PV-8 off eBay. I hook it up four days ago and thankfully it worked. It sounds good but I thought it had excessive bass. I openned it up and I think I found the problem the previous owner put 12AX7's in V4, V5 and V6 tube sockets. V4 is possibly a sovak tube, markings have been wiped off except for handwrtten "12AX7" in Sharpie. V5 V6 are electro harmonix and V1 V2 look like Chinese tubes but no markings I hope they are 12AX7. V3 is a US made 5751.

Does anyone have suggestions on tube types and brands for a PV-8? A have NOS 12AX7 Mullard, good used tungsgram, good used RCA tubes. NOS 5751 Amperex, good used GE, Sylvannia, and Philips. And NOS 5965 US made tubes.

Finally, I am wondering if new production Tungsol or JJ 5751 tubes are any good. I am wondering if there are any truly "NOS" tubes on the market anymore and should switch to new production tubes.

[jeffreybehr]

Vs 1 and 2 are 12AX7s, Vs 3 and 5 are 5751s, and Vs 4 and 6 (the cathode followers) are 5965s. See
http://www.conradjohnson.com/It_just_so ... a-PV8.html

If I were buying a complete set of new tubes for an '8 AND I used the fonostage, for a fine-sounding low-priced, New-Production 12AX7 I'd buy gold-pin JJs from TubeDepot...
https://store.tubedepot.com/products/jj ... acuum-tube
...selected for low noise. An upgrade from that MIGHT be the NP gold-pin Gold Lions...
https://store.tubedepot.com/products/ge ... acuum-tube
...again low-noise selected.

For 5751s, I'd buy the NP Tung-Sol...
https://store.tubedepot.com/products/tu ... acuum-tube
...again selected for low noise and microfonics since the linestage has so much gain (31dB).

I suggest you use the NOS 5965s you already have.

I'd also use Herbies tube dampers on the gain tubes (= all but the 5965s).
http://herbiesaudiolab.net/preamp.htm

I've been using these in appropriate sizes for decades; I find they reduce low-level edginess and microfonics very well. Here's my c-j MET1 with Herbies dampers around the three-front-channel Mullard M8080s. You would order SS-9s for the 12AX7-size tubes, as all of yours are.


Here's one of my former Antique Sound Lab Hurricanes with Herbies dampers embracing the front-end 6SN7s.


And here are my former ASL Explorer 805s with Herbies dampers around ALL tubes.


FWIW, I'd never substitute 5751s for 12AX7s in fono stages as that likely would foul the fono-eq, but if the linestage had more gain than I wanted, I'd sure start substituting 12AY7s, 12AV7s, 12AT7s, and/or 12AU7s for the 5751.