Dennis Had Inspire Amps

[Rosco65]

At least in my main rig, I think I am narrowing down. The LP-27a and PSE will likely serve for the foreseeable future. I've gathered all the parts for new speakers (Altec 414-8C's, 802D's, 32A horns, custom autoformers, vintage oil caps and WE wire) and need now to finalize the cabinet design and have them built and tuned. I also need to upgrade my phono stage (using a Stan Warren - modified Superphon Revelation Pro Basic ATM), and modify/tune my turntable (Kenwood KD550) and replace the arm (probably Jelco or SME). I have DAC's from Schiit (Gungnir MB) and DB Audio Labs (Tranquility and Tranquility SE).

I also have to rearrange and tune the dedicated room. It is only about 11' x 12', so this is a challenge but I am free to use room treatments.

[FloridaBoy]

Originally Posted by CoGT3

Think you nailed regarding the shift in tubes used. He shipped my 45 SET with the "tung sol" 6sl7gt. When I asked about rolling he implied the new production tube was awfully good but there where gains to be had at a $$$ and depending on preference. That may be the shift toward 6xx7s. When he wasn't making that many amps it probably wasn't too hard to track down NOS drivers,but the volume he is now making that has to be harder. He has already made it very clear how good he thinks the Russian GL KT88s are, especially compared to the price of admission for NOS output tubes. At least for the amps, you only need 1 6xx7 for rolling tubes isn't that expensive. Glad the PSE is using the 6xx7 driver also, will be picking one up to compliment the 45 SET when the timing is right.

You may want to ask Dennis if your 45 amp can also use 6SN7's.

My LP27a was sent with a 6BX7 and some one here posted that it can also use 6SL7 & 6SN7. Just gives more options.

[FloridaBoy]

Originally Posted by Bombadil

He does just whip them together. Frequent changes. He built my amp in May, but when I communicated with him, he needed pictures of the underside of it in order to know what he did with it.

Mine has the 20 watt output transformers, but is pentode wired to produce 17 wpc with KT88. Standard tube set of KT88, 6SN7, and 5AR4/GZ34 rectifier. I mix/match several output tube types and rectifiers, but always stay with 6SN7 driver tubes. Was told that if I use 5U4G rectifiers that I will get 15 wpc with KT88.

We probably have a similar amp but mine is triode wired so I get about 5 watts with 6V6's and 7 or 8 with 6L6's.

[Bombadil]

I don't see the 6SL7 and 6SN7 tubes to be optimally swapable.

They have different heater currents, max plate voltages, max plate dissipation, and have significantly different gain. The plate resistance within the tube is 44K in a 6SL7, it's just 7K in a 6SN7.

If a circuit is designed for one of them then substituting the other could behave quite differently, and have a significant effect on the sound of the amp. Just like subbing a 12AX7 for a 12AU7, it doesn't change just the gain but can throw the entire tone of the amp off.

[Rosco65]

I have a 421a amp that uses either a 6SL7 or 6SN7 as the driver tube. The 6SL7 has more gain and is the better sounding tube in the application to my ears, but the 6SN7 is valid in that position and had I not heard the 6SL7 I would be perfectly happy.

In this application - the driver tube of a single-ended amp - it would appear that the differences between the two tubes are within the realm of acceptability.

[Bombadil]

Some will say it is acceptable, others will say it is not even close.

I wouldn't do it.

[CoGT3]

Originally Posted by FloridaBoy

You may want to ask Dennis if your 45 amp can also use 6SN7's.

My LP27a was sent with a 6BX7 and some one here posted that it can also use 6SL7 & 6SN7. Just gives more options.

I have asked, he said they are all fair game. With the lower output 45s I have stuck with 6SL7s so far. Nice thing about them is they are way cheaper than there 6SN7 cousins. Have picked up 2 Tung sols (one a mid 40's NOS JAN blackglass, round plate, oval micas, same construction as the much sought after 6SN7 version), another USAF 6SU7GT, RCA 5691 red base/black plate, and recently a Sylvania chrome top.

Just picked up a Sylvania 6BX7GT to try. Dennis it would be a little more "nasty" compared to the 6SL7s.

Another reason I'm glad the PSE is using the 6xx7's, already have some tubes to role.

[Rosco65]

Well, the designer and builder both say it is acceptable, so I suppose I'll risk it.

[CoGT3]

Originally Posted by Rosco65

Dennis just finished and sent my PSE amp (awaiting FedEx). He installed Jantzen 1200v silver z caps. However, he may use something different in the LP27a.

I purchased my LP-27a with the DACT from the beginning, and believe that it has Audyn caps, so he may use Audyn True Silver as well.

He seems to like the German coupling caps, and frankly the price of Jantzen or Audyn caps are much less than other boutique caps. I trust his ears, but he also may be working to a price point as well (he didn't succeed in business by making products he couldn't sell). That being said, simply throwing money at boutique parts is no guarantee of good sound.

I may have seen "up the skirt" of your PSE. Dennis sent me a build pic of a PSE with Jantzen silver z's as coupling caps as well as in the power supply sections. We have been trading emails back and forth about the PSE as he thought it would compliment my 45 SET nicely. I had already asked about "hot roding" the PSE with "better" caps such as the Jupiter copper foils. He took a look and said it might make sense for the coupling caps, but the size of the caps in the power supply would be very expensive with the Jupiters. He basically said he thinks the Jantzen silver z's really fit his amps perfectly from a performance/sound standpoint. Kind of implied that they may be "too much" in something like a solid stamp amp. Read into that what you will.

Will be looking forward to your impressions of the PSE. This is how Dennis described it too me "The 45 amplifier presents one of the closest to a live performance presentations I have heard. This new PSE presents the performance closer to the studio performance. Speed, dynamics with an amazing jump factor. Two different listening venues with great emotional impact either amplifier." Went as far as calling the 45 SET an "old guy" amp.

[Rosco65]

That sounds like my amp - 800v Jantzen's in the PS and 1200v Jantzen's in the coupling positions. Changing the coupling caps is perhaps the easiest mod you can make, but getting Jupiters under the hood of the PSE might be pushing it; they are pretty big. The Humble Homemade Hifi Cap test (Humble Homemade Hifi - Cap Test - a must read in my opinion) rates the Jantzen's very highly, but implies a certain "German" character to the sound (i.e., not romantic at all). The Audyn and Mundorfs seem to share this characteristic.

I have no problem with a studio sound; the speakers the PSE will drive are an interpretation of a classic Altec studio monitor. My other main amp is a custom build of a Fi 421a circuit, driving Omega Super Alnico Monitors. This amp has a character somewhere between a 45 and 300B tube and has enough room under the hood to add Jupiter (or Red Astron or Vitamin Q) caps if I feel the need to "upgrade". The 421a (and the direct-coupled 45 amp I used to own) have an intimacy that works really well with less complex music and especially the human voice, but lacks some of scale I need for some of my more "produced" music. I hope the PSE will fill that need pushing 12" Alnico Altec's. "Speed, dynamics with an amazing jump factor" is exactly what I want.