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Inspire by Dennis Had Enjoying Vacuum Tube Audio

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  #6481  
Old 07-18-2021, 10:34 AM
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Default Some clarification from Dennis...

Dennis wanted to clarify the microphonics question and sent me a text with a quote which I will now share...


“In the final production design of the new Inspire LP-71a the issue of microphonic tubes is actually a non issue. One may use any of the 71A through 01A tubes without microphonic concerns. The production circuitry in the LP-71a the AF gain is controlled at the output. Thus at normal operating condition the LP-71a is actually one the quietest preamplifiers I am aware of. I just wanted to clear up this point.

The happening Isaacc7 experienced will not occur with the new Inspire LP-71a. Just an amazing quiet dark background with explosive dynamics only derived from the magnificent tubes of the roaring 20’s!!!!!!! Love this Hi Fi stuff.”


And so there you have it. Dennis may not post on this forum, but you can be sure he reads every word...

Last edited by Analog Addict; 07-18-2021 at 10:38 AM.
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  #6482  
Old 07-18-2021, 12:43 PM
Isaacc7 Isaacc7 is offline
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Originally Posted by Analog Addict View Post
Oh yeah, you can tap out a tune on the pre amp chassis if you want. Nothing in life is 100% perfect.

Mine uses a single 0A3, a 5AR4 rectifier, the two signal tubes, and a 6SN7 for the center channel mixer. The official LP-71A uses two signal tubes, a 5U4G rectifier and an 0A3 for each channel.
The oa3 looks cool! The preamp I ordered uses 6l6 tubes for shunt regulation. I wonder what advantages each choice has.
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  #6483  
Old 07-18-2021, 12:44 PM
Isaacc7 Isaacc7 is offline
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Quote:
Originally Posted by Analog Addict View Post
Dennis wanted to clarify the microphonics question and sent me a text with a quote which I will now share...


“In the final production design of the new Inspire LP-71a the issue of microphonic tubes is actually a non issue. One may use any of the 71A through 01A tubes without microphonic concerns. The production circuitry in the LP-71a the AF gain is controlled at the output. Thus at normal operating condition the LP-71a is actually one the quietest preamplifiers I am aware of. I just wanted to clear up this point.

The happening Isaacc7 experienced will not occur with the new Inspire LP-71a. Just an amazing quiet dark background with explosive dynamics only derived from the magnificent tubes of the roaring 20’s!!!!!!! Love this Hi Fi stuff.”


And so there you have it. Dennis may not post on this forum, but you can be sure he reads every word...
Good to know! I gotta say, when they put that preamp in this particular system it transformed it. If Dennis has managed to tame the microphonic issue I'm sure it's gaining to be amazing.
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  #6484  
Old 07-18-2021, 04:41 PM
Bombadil Bombadil is offline
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While I've experienced audible issues with highly microphonic tubes, for the most part they have been fine. Taping on a tube or the preamp and hearing it through your speakers does not mean that music will be affected. The impact of a pencil or finger tapping on a tube or chassis is many times greater than the vibration from sound waves out of your speaker.
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  #6485  
Old 07-19-2021, 10:35 PM
Isaacc7 Isaacc7 is offline
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My tube rolling adventure continues! Now using the Sylvania 7f7 with some tubes from my tube stash. I have a pair of Ken Rad black glass 6v6 and an RCA 5u4g. Sounds amazing! Dennis used to make parallel 6v6 amps in the past right? Wonder if he could be persuaded to do it again...
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  #6486  
Old 07-20-2021, 08:07 AM
bearcity bearcity is online now
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Quote:
Originally Posted by Isaacc7 View Post
My tube rolling adventure continues! Now using the Sylvania 7f7 with some tubes from my tube stash. I have a pair of Ken Rad black glass 6v6 and an RCA 5u4g. Sounds amazing! Dennis used to make parallel 6v6 amps in the past right? Wonder if he could be persuaded to do it again...


He does. They are marketed by Moon audio. QMB25.
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  #6487  
Old 07-20-2021, 02:39 PM
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Quote:
Originally Posted by Isaacc7 View Post
My tube rolling adventure continues! Now using the Sylvania 7f7 with some tubes from my tube stash. I have a pair of Ken Rad black glass 6v6 and an RCA 5u4g. Sounds amazing! Dennis used to make parallel 6v6 amps in the past right? Wonder if he could be persuaded to do it again...
I might suggest emailing Dennis through his radioman731 moniker on Ebay and asking him directly. Make him a good enuff offer and he might even sell you that one...
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  #6488  
Old 07-20-2021, 10:41 PM
Isaacc7 Isaacc7 is offline
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Originally Posted by bearcity View Post
He does. They are marketed by Moon audio. QMB25.
Yeah, that's what I have in mind, but I'd want a few changes. First I'd like the option to use 12v tubes too. I have a ton of 14c5 and 12v6 tubes. If I'm going to tube roll 8 output tubes at a time it's important to keep the price down! I'd also like the idea of using 6j5/12j5 instead of 6sn7 too. Lots of possibilities for different combinations there too.

The Moon audio page for that amp is a mess. It calls the input tube a 6sn7, 6sl7, and even 6n7 in different parts of the description. Also says it uses a 5ar4 and then 5u4g. I wonder if it has the same flexibility of input tube as the regular Firebottle amp. Anyway, 5k for this one is just outside my possible budget, adding my special mods would push it higher no doubt. Bummer.
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  #6489  
Old 07-21-2021, 09:51 PM
pcprincipal pcprincipal is offline
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Quote:
Originally Posted by Analog Addict View Post
Dennis has been perfecting an upscale version of a pre amp that we have been monkeying around with for the better part of 3 years, and as some of you may already know, is called the LP-71A.

Before I go any further, let me tell you all what Dennis has said about this new design, and I quote...

"Not only is this the best pre amp I've ever designed, but it is the best pre amp I've ever heard"

What more is there to be said?

One of the nice things is that it will run three different types of tubes interchangeably, the 12/112, the 01A and variants, and of course the 71A and it's variants. I won't try and describe how it sounds. Let Dennis' comment speak for itself...

Untitled by analog addict, on Flickr

Untitled by analog addict, on Flickr

Untitled by analog addict, on Flickr

Amps for today were a 45 SET and a PSE 6V6 prototype wired in pentode.

Untitled by analog addict, on Flickr

Here's my preamp, which I suppose one could call the original prototype on the bench. Check out that square wave... Perfect! Even with the gain turned up to 11, the sine wave is perfect and undistorted.

Untitled by analog addict, on Flickr

Finally a shot with some thoriated filament globes installed. These tend to be a bit more finicky because of the microphonics and the fragility of the innards, but they do shore look nice...
Untitled by analog addict, on Flickr
How does it differ from the CJ-5? I have one. How much better is it?

Also, do you recommend and particular tubes for the CJ-5?
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  #6490  
Old 07-22-2021, 02:49 PM
Bombadil Bombadil is offline
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Question about 6F6 tubes.

I have many 6V6GT tubes. I like how they sound in my PSE, but dislike them in my KT88 SE HO.

Would like to pick up a few 6F6 to hear how they compare.

Any recommendations of reasonably priced 6F6? (Not Fivre or Marconi)) There are many to choose from. Metal, 6F6G, 6F6GT. GE, RCA, Hytron, Raytheon, Sylvania, Tung-sol, Ken Rad, more.

I have 5 different brands of 6V6GT tubes but find that they all sound rather similar.
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