Dennis Had Inspire Amps

[oldominion]

Originally Posted by bwilson51

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 .

Weird that it's only right channel. I assume you've tried swapping tubes, etc, etc.

I actually had a weird thing happen recently: I was having issues in my phono chain, a 60 hz hum then a channel dropping out. After tearing my hair out I realized that one of my cables, an AQ of all things, was shorting out. Tested it w multimeter. It had lost its ground wire! Then I remembered that that's actually the second time that's happened to me, that is, a problem being traced to a cable going south, something I don't really think about that often. You've probably done this, but try different cables?

I have a set of super sounding cables made by Crimson UK that are totally unshielded. I can use them in digital chain but phono? Fuggedaboutit. HHUUUUMMMmmmmmmmmm....

[oldominion]

Now that things are warmed up with the 5691 in place of the 6bx7, I cannot hear any noise through the speakers. That is good.

However, strangely I can still hear a very slight mechanical or operational noise coming from the preamp itself. A tiny, almost inaudible buzzing or tinkling if I lean down and put my ear next to the preamp. Clearly this noise was being amplified by the 6bx7 in a way it's not being amplified by the 5691.

This is weird because I thought the 5691/6sl7 family (mu of 20) of was HIGHER gain than 6sn7/6bx7 (mu of 10); I know it's being used as a buffer in the circuit but it still seems odd. Any thoughts?

On one hand I'm happy that I'm not hearing the noise through the speakers, but on the other I wonder why the noise exists at all.

With the 6bx7 in place, the sound is much more forward, more "gainy", a bit more in your face; move the vol knob a mm and you'll hear it. A lot more sensitive, obviously. With the 5691 in place the sound is very pleasant, more laid back, less gainy and actually quite nice. Not sure it has the same "grab you by the lapels" factor, but maybe this will end up being a good thing.

I have an email in to Dennis and will report back.

[bwilson51]

I have tried multiple 6SN7 gtb nos tubes and current production tung sol,the hum comes and goes I thought I had it solved but I have had no luck.I thought it was issues with my wiring in my home.I just tried an nos tung sol 6sl7 tube and that did not help.I thought of taking the bottom plate off and see if any wires were touching causes this problem.

[bwilson51]

I am enjoying my Inspire LP-3.1 preamp with out any unwanted noise or hums and I am a happy camper.I have always enjoyed the sound of this preamp and I just lived with the noise between tracks.Now it is quiet and the sound of my system is outstanding.Now if I just had a remote control.

[oldominion]

Mine was silent as the grave for the first few months. I switched to 6cd7 tubes at Dennis's recommendation. They sounded fantastic, super lively, clear as water, really great, but soon the tinkling sounds began. Sort of a tinkling, fizzling sound that can go from being barely audible to quite annoying. I do think it has something to do with microphony, as in, it's in the microphonic family--lol--and not an issue with a cap or resistor or whatever. I can tap the tube with a piece of soft wood, a shim I have handy, and the sound will go away for a period of time. Puzzling thing is that I've used a bunch of different tubes and the same thing will creep back no matter what tubes I'm using.

I'm waiting form some heavy duty dampers I bought, will report back ASAP.

[maro]

I had a similar problem on my 6SN7 preamp. I would put in a new pair of tubes and it would sound great and have no noise. Then slowly the right channel would become noisy and if I touched the tube a loud pop occurred. In would go another pair of tubes and all would be well, then the cycle of noise would return. I was convinced the preamp was wrecking my vintage 6SN7's. Took the bottom off and started checking connections around the right socket. Found a capacitor connection that was slightly loose. Moving the tube would make it tight then over time it would relax and become noisy. Re-soldered the connection and it has been fine ever since.

[pechelman]

Originally Posted by oldominion

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!).

Did he happen to suggest any 6bx7 substitutes besides the 5691? Thought a 5691 was pretty similar to a 6sn7? Maybe I should reach out again to Dennis.

[FloridaBoy]

Originally Posted by pechelman

Did he happen to suggest any 6bx7 substitutes besides the 5691? Thought a 5691 was pretty similar to a 6sn7? Maybe I should reach out again to Dennis.

The 5691 is a 6SL7. The link below is for the tube substitution handbook. The second link is for A Taste of Tubes.

http://www.smcelectronics.com/DOWNLO...SUB%201980.PDF

http://ken-gilbert.com/images/pdf/taste_of_tubes.pdf

[PSE45]

@x3workshop

X3workshop, any further thoughts about your PSE45? I have an inspire 45 SET and PSE with IIPS. Have pretty efficient speakers (used 45 SET for quite a while), thinking about replacing both or at least 45 SET with the PSE45. Curious how it’s matured no that you’ve had it for a while?

[Masterlu]

PSE45... Welcome to AA!