I did and did not find one that really stood out. I have the LP27a and used a 6sn7 instead of a 6Bx7. I'm not sure if you can with the LP 3.1a. The pinging and ringing is usually from microphonic tubes. Have you tried silicone dampers?

Is the 5R4GY a direct replacement rectifier for the 5AR4 within the same parameters, I wanted to try the KT150 on my inspire amp and Dennis recommends the 5AR4 but was wondering if the 5R4GY could be used with the same effect

The 5R4GY has more voltage drop than a 5AR4.

Tube# - Base - Fvolt - Famp - Vdrop - MaxPmA - MaxPv - notes
5AR4/GZ34-5DA - 5.0 - 1.9 - 17 - 250 - 450 - low Vdrop 5U4/5Y3
5AS4-A - 5T - 5.0 - 3.0 - 50 - 275 - 450 - improved 5U4
5AT4 - 5L - 5.0 - 5.5 - 30 - 800 - 550 - higher power 5U4
5AU4 - 5T - 5.0 - 3.75 - 50 - 325 - 400 - high power 5U4
5AW4 - 5T - 5.0 - 3.7 - 46 - 250 - 450 - long life 5U4
5AX4-GT - 5T - 5.0 - 2.5 - 65 - 175 - 350 - high power 5Y3
5AZ3 - 12BR - 5.0 - 3.0 - 44 - 275 - 600 - compactron 5U4
5AZ4 - 5T* - 5.0 - 2.0 - 60 - 125 - 350 - loctal 5Y3
5BC3 - 9QJ - 5.0 - 3.0 - 53 - 300 - 500 - compactron
5CG4 - 5L - 5.0 - 2.0 - ? - 125 - 400
5DJ4 - 8KS - 5.0 - 3.0 - 44 - 300 - 600 - redesigned 5U4 (higher volts)
5R4-G/GY- 5T - 5.0 - 2.0 - 67 - 250 - 750 - high voltage 5U4
5R4-GYA - 5T - 5.0 - 2.0 - 67 - 250 - 750 - high voltage 5U4 (ruggedized)
5R4-GYB - 5T - 5.0 - 2.0 - 63 - 250 - 900 - high voltage 5U4 (ruggedized)
5T4 - 5T - 5.0 - 2.0 - 45 - 225 - 450 - metal 5U4
5U4-G - 5T - 5.0 - 3.0 - 44 - 225 - 450 - octal 5Z3
5U4-GA - 5T - 5.0 - 3.0 - 44 - 250 - 450
5U4-GB - 5T - 5.0 - 3.0 - 50 - 275 - 450
5V3 - 5T - 5.0 - 3.8 - 47 - 350 - 425 - higher power 5U4
5V3-A - 5T - 5.0 - 3.0 - 42 - 415 - 550 - 5V3 reduced filament current
5V4-G/GA- 5L - 5.0 - 2.0 - 25 - 175 - 375 - octal 83-V
5W4-G/GT- 5T - 5.0 - 1.5 - 45 - 100 - 350 - low power 5Y3
5X4-G - 5Q - 5.0 - 3.0 - 58 - 225 - 450 - 5U4 diff pinout
5X4-GA - 5Q - 5.0 - 3.0 - 47 - 250 - 450
5Y3-G/GT- 5T - 5.0 - 2.0 - 60 - 125 - 350 - octal 80
5Y4-G/GT- 5Q - 5.0 - 2.0 - 60 - 125 - 350 - 5Y3 diff pinout
5Z3 - 5T - 5.0 - 3.0 - 58 - 225 - 450 - 4pin 5U4
5Z4 - 5L - 5.0 - 2.0 - 20 - 125 - 350 - low drop 5Y3
80 - 4C - 5.0 - 2.0 - 60 - 125 - 350 - 4pin 5Y3
82 - 4C - 2.5 - 3.0 - 15 - 115 - 450 - lower power type 83
83 - 4C - 5.0 - 3.0 - 15 - 225 - 450 - 4pin mercury vapour
83-V - 4C - 5.0 - 2.0 - 25 - 175 - 375 - 4pin 5V4
1641 - 8E - 5.0 - 3.0 - 44 - 250 - 450 - rabbit ear 5U4
5931 - 5T - 5.0 - 3.0 - 47 - 300 - 600 - industrial 5U4
6004 - 2AJ - 5.0 - 2.0 - 60 - 120 - 375 - rabbit ear 5Y3
6087 - 5L - 5.0 - 2.0 - 50 - 125 - 350
6106 - 5L - 5.0 - 2.0 - 60 - 125 - 350
6853 - 8HE - 5.0 - 1.7 - 60 - 125 - 350
RK60 - 8E - 5.0 - 3.0 - 44 - 250 - 450 - rabbit ear 5U4

I have always been a cheapskate so I've used rubber washers (which don't melt, I promise!) from the hardware store for ages. But they don't seem to do much with the 6sn7.

Cheap as I am, I may pony up the dough for some Sophia 6sn7's. The Sophia 274 rectifier is magnificent in my Inspire with the T-S KT150's. A highly recommended pairing.

Thank you

The Sophia blue 6SN7's are excellent, pricey but worth it. :thumbsup:

Well, I've reached a point where the noise in my Inspire 3.1 preamp is unacceptable. Something is clearly amiss. There is a very high buzzing or "tinkling" sound that does not sound like normal tube microphony, which I've heard a zillion times. It comes and goes, which is puzzling.

I do note that in this preamp application the 6sn7 is incredibly microphonic, whereas it's never been a particularly troublesome tube for me in the past, going all the way back to my Conrad Johnson MV60SE that I had a bunch of years ago, and is currently the first stage of amplification in my Radio Craftsmen RC2's (which are wonderful and overlooked amps, especially if the first stage of the 6j5 is taken out of the circuit as I've done).

I've tried scads if different tubes in all positions in the 3.1 except for the driver 6bx7, so that may be the culprit...

In any case, Dennis has not answered my last three or four emails, so I'm coming to this forum, and to Straitwire in hopes of directing attention towards my queries. The preamp sounds wonderful, very forward and alive, definitely a "first row" presentation, none of this middle of the hall baloney, and I'm happy to ship the preamp to Dennis if, in fact, there might be an issue.

I could just buy a new 6bx7, but there's something that tells me we might have a more serious problem.

Many thanks, Straitwire. I know DH is awful busy making the world a better place through his excellent designs--my life has been better since purchasing the 3.1 and Inspire FireBottle, two pieces I will never part with--so I'm looking forward to getting to the bottom of this.

I have had the same issues with my updated Inspire LP 3.1,I tried current model tung sol 6sn7 tubes and that helped but then I get the same hum but only in the right channel.Great sounding preamp,but the noise between tracks are a pita .

I commented a while ago having an audible between tracks buzz and was told this was a known design compromise to provide greater staging depth. I tried rolling all the tubes, including the 6bx7 with really no difference. The one exception was a terrible set of electro Harmonix that created extremely loud feedback in the preamp at normal listening levels with no signal.

I also tired moving cables and components around a little just in case there was something going on there. No change.

Either way, would be interested to know what you find out to see if anything might apply to me.

Dennis answered my email and suggested trying another tube in the 6bx7 position. I put in a 5691 tube I had (6sl7 variant), and initial listens allow me to think that the 6bx7 tube was the problem. I'm getting much quieter operation with the 5691. Will continue to listen and report back, but I'm thinking that tube was the problem. If it was, I guess I'll need to figure out whether to buy another 6bx7 (they're cheap) or continue to use my 5691 (not cheap!).