Dennis Had Inspire Amps

[pechelman]

Originally Posted by bwilson51

I changed the5y3 to a 5u4 and I plugged the power cord into a quality power conditioner.I use highly modified Klipschorns with Volti horn upgrades with bms4592nd mids and I have to put my head un against the grill to hear a faint buzz.

Thanks.

Did you do all of this at once? Wondering if you were able to pinpoint this to a tube or conditioner change or if it's really all of them that needed to be done.

Before it was definitely a faint buzz but with more power it got less faint.
Dennis give you the OK on the 5U4 instead of the 5Y3? Looks like there's a slight difference in some ratings but notably a difference in Famp and Fvolt of 3 vs 2 and 44 vs 60, respectively.

[Bombadil]

Originally Posted by bwilson51

I changed the5y3 to a 5u4 and I plugged the power cord into a quality power conditioner.I use highly modified Klipschorns with Volti horn upgrades with bms4592nd mids and I have to put my head un against the grill to hear a faint buzz.

Did you try different 5Y3 rectifiers? Asking because I have two rectifier tubes which cause my Inspire power amp to hum a bit. I'm sure it is due to the specific tubes and not the tube types, as I have other rectifiers of the exact same tube type which do not create a hum.

[straitwire]

If you have a defective rectifier tube with only one section operating this will provide only half wave rectification and allow a considerable amount of AC ripple.
The circuit calls for full wave rectification.
Dennis had a fellow with an LP-3.1 that had a hum.
Dennis had him send the preamp back in.
All was well and the preamp was returned to the customer.
Once again the poor fella said he had a hum.
After much correspondence it turned out to be a defective Bendix rectifier supplied by the customer.
One section of the rectifier was defective and therefore the preamp was receiving only half wave rectification.

[pechelman]

have tried a few rectifiers including the sovtek one dennis included and one stamped GE all with the same result. currently have a bendix one in at the moment, but guess i will try rolling back to the sovtek.

[bwilson51]

Originally Posted by pechelman

have tried a few rectifiers including the sovtek one dennis included and one stamped GE all with the same result. currently have a bendix one in at the moment, but guess i will try rolling back to the sovtek.

I never checked with Dennis on using the 5u4 tube, I was online and saw one being used and I thought I would try it.My 3.1 has been sitting and I hooked it up tonight and played it with the 5u4 without the power conditioner and then with the power conditioner and the slight hum was still there.So I then installed the 5y3 RCA tube and still the same thing.I am using Primaluna EVO-300 amp and preamp and it is dead quiet,no hum no hiss,silent.I am going to play with the Inspire preamp tonight,I am keeping the 5y3 tube in the preamp evertything just opens up with the 5y3 .

[pechelman]

thanks guys. appreciate you looking at this for me.

I had learned to live with the hum on the 45 firebottle amp, it was hardly noticable, and was worth the beauty his pre provides. It was a little more prominent with a ~20wpc amp that made me step back.

[pechelman]

Went back to the sovtek 5y3 included by Dennis and the same hum. Unlike yesterday it doesnt seem that warmup has influenced the hum at all...maybe i was just listening to louder music yesterday that didnt have as much space between notes like I am today.

I do have the preamp plugged into a humx and the spectral analyzer on my phone shows a peak at/near 60Hz.

Was using some old RCA 6SN7s but then swapped in some old kenrads I had but worried one might have blown when it started to heat up . Really bad hum like what I had with some electroharmonix a while ago. Think I see a crack near the base. Switched back to the GE's Dennis shipped with it and the buzz is still present.

Is there anything I should check internally before I reach out to Dennis besides an obvious loose connection?

[FloridaBoy]

Originally Posted by pechelman

Went back to the sovtek 5y3 included by Dennis and the same hum. Unlike yesterday it doesnt seem that warmup has influenced the hum at all...maybe i was just listening to louder music yesterday that didnt have as much space between notes like I am today.

I do have the preamp plugged into a humx and the spectral analyzer on my phone shows a peak at/near 60Hz.

Was using some old RCA 6SN7s but then swapped in some old kenrads I had but worried one might have blown when it started to heat up . Really bad hum like what I had with some electroharmonix a while ago. Think I see a crack near the base. Switched back to the GE's Dennis shipped with it and the buzz is still present.

Is there anything I should check internally before I reach out to Dennis besides an obvious loose connection?

Read this: https://www.18watt.com/viewtopic.php?t=15926

The Sovtek 5Y3 is also indirectly heated. I suggest trying an old production 5Y3G ST/Coke bottle with closely matched sections. I had a similar issue when I tried a JJ 5Y3/S.

[pechelman]

Thanks.

That thread was one of the original reasons I moved away from the provided Sovtek in the first place. Thought I should go back to double check since it was what Dennis provided.

Either way, it's a good idea to try the bigger 5Y3G envelope first. Going to go find a couple. Thanks for the idea.

Similarly, anyone try the solid state plug in rectifiers here? Wondering if that could at least help me diagnose this further.

[FloridaBoy]

Originally Posted by pechelman

Thanks.

That thread was one of the original reasons I moved away from the provided Sovtek in the first place. Thought I should go back to double check since it was what Dennis provided.

Either way, it's a good idea to try the bigger 5Y3G envelope first. Going to go find a couple. Thanks for the idea.

Similarly, anyone try the solid state plug in rectifiers here? Wondering if that could at least help me diagnose this further.

The tube that worked best in my PSE is a Silvertone labeled 5Y3G with ribbed plates.