Dennis Had Inspire Amps

[Analog Addict]

A little speaker porn....

[Analog Addict]

Just getting started on a new project as well. Some of you may recognize the basic layout. I've had a 27/56 based preamp in the queue for quite awhlie, but it's taken Dennis' chassis man a good while to get it back to me. Not his fault, Dennis keeps him pretty busy. Who loves you Tony? ;-)

Anyway Dennis has signed off on the design and all the iron is painted and ready to go. My last two builds got powder coated with on of the Inspire runs, but not this one. Anyway, it will be my version of the LP-27. Dennis uses technical wizardry on his power supplies, i use a lot of chokes and capacitance. If you all are interested, I'll dig up the power supply and circuit schematic and post them....

EDIT: it would help if i posted the picture. All the parts ore out of my stash except the three position switch and the volume pot.

[x3workshop]

This is for the LP-27a owners:

With the volume down, I start up the preamp and let it warm up for about a minute and then fire up the amp. As the amp begins to conduct I get a very loud hum. I shut the amp down right away, but it continues until I shut the preamp down. Then it stops immediately. Volume does not affect it.

This happens sometimes, not always.

At first I thought it was a loose top cap on the 807's that I was running in the amp because it stopped when I touched it. Then it happened again but touching it didn't fix it, so I swapped in the KT120's that I had. Same thing. Swapped driver and rectifier and... same thing, but not always.

The last time it did this I was across the room and didn't get to it right away to shut it down so it hummed and then squeeled and... stopped. I thought I blew the speakers, but thought to try a source and beautiful music was playing.

I swapped all the tubes in the pre (running 56's not 27's) and still hummmmmmmmm...

This is emanating from the preamp, not the amp. Did all the usual connection/ground checks and all is normal. It doesn't happen with other preamps into the Inspire and I confirmed it with using another pair of amps.

Reached out to Dennis who said it sounded like the tubes hadn't quite biased up and to give it a good 5- 10 minutes warm up. Gave it 5+ minutes today driving a pair of MC30's and the same thing happened.

Wondering if anyone else has had this issue?

[Musica Amantem]

Originally Posted by x3workshop

This is for the LP-27a owners:

With the volume down, I start up the preamp and let it warm up for about a minute and then fire up the amp. As the amp begins to conduct I get a very loud hum. I shut the amp down right away, but it continues until I shut the preamp down. Then it stops immediately. Volume does not affect it.

This happens sometimes, not always.

At first I thought it was a loose top cap on the 807's that I was running in the amp because it stopped when I touched it. Then it happened again but touching it didn't fix it, so I swapped in the KT120's that I had. Same thing. Swapped driver and rectifier and... same thing, but not always.

The last time it did this I was across the room and didn't get to it right away to shut it down so it hummed and then squeeled and... stopped. I thought I blew the speakers, but thought to try a source and beautiful music was playing.

I swapped all the tubes in the pre (running 56's not 27's) and still hummmmmmmmm...

This is emanating from the preamp, not the amp. Did all the usual connection/ground checks and all is normal. It doesn't happen with other preamps into the Inspire and I confirmed it with using another pair of amps.

Reached out to Dennis who said it sounded like the tubes hadn't quite biased up and to give it a good 5- 10 minutes warm up. Gave it 5+ minutes today driving a pair of MC30's and the same thing happened.

Wondering if anyone else has had this issue?

I had the same issue the first time I turned my LP-27a on. After several tests, I found out one of the balloon type 27 tubes Dennis sent me with the unit was bad. It probably developed a failure during transportation because Dennis checked it thoroughly before sending it over. Swapped both 27's with the other stock pair of 56 tubes Dennis included and voilà, no more issues. After I received the 27 replacement pair I've been almost exclusively using those in the preamp due to slightly better sonics in my system with them over the 56's (which also sound wonderful, mind you).

I would double-check it is not one of the tubes in either unit, otherwise, call Dennis again for a trouble-shooting orientation.

[Musica Amantem]

Analog Addict ... A little speaker porn....


Beautiful-looking pieces! Could you elaborate on the specs of those beauties? I'm especially interested in their sensitivity ratings. Thanks!

[x3workshop]

Originally Posted by Analog Addict

A little speaker porn....

Morel Tweeters, but I wonder what the LF drivers are?

[x3workshop]

Originally Posted by Musica Amantem

I had the same issue the first time I turned my LP-27a on. After several tests, I found out one of the balloon type 27 tubes Dennis sent me with the unit was bad. It probably developed a failure during transportation because Dennis checked it thoroughly before sending it over. Swapped both 27's with the other stock pair of 56 tubes Dennis included and voilà, no more issues. After I received the 27 replacement pair I've been almost exclusively using those in the preamp due to slightly better sonics in my system with them over the 56's (which also sound wonderful, mind you).

I would double-check it is not one of the tubes in either unit, otherwise, call Dennis again for a trouble-shooting orientation.

Happened when I swapped another pair of 56's in. Wonder if it's the 6BX7 driver? Only tube I didn't change.

[Analog Addict]

If I remember correctly Dennis used two of the woofers to bring up the sensitivity 3db to somewhere in the low 90's, 92 or 93db/w/m I believe. I have a measured grew response curve somewhere I will post. The woofers may be Peerless. Dennis will remember....

[x3workshop]

The Morel CAT 378 tweeter is 93db out of the box.

[Analog Addict]

Yep. The idea was to march the tweeter....