Dennis Had Inspire Amps

[Bombadil]

Finally got around to trying some EL84s in my Inspire. Purchased a couple of octal to EL84 adapters some months ago but never tried them out. The pins in the adapters were super tight, had to use another old 9-pin tube to wedge them open to get the EL84s in.

Sounds nice. The bass isn't as well defined as with my KT88/KT120/KT150 tubes or as powerful, but a reasonable amount is there. Far more bass than my Inspire EL84 SE amp, which has puny, commercially-available (off of that auction site for around $30 each) output transformers, which start rolling off around 80Hz.

Surprising amount of punch driving my 91dB speakers. My Inspire drives tubes hard, producing 17 wpc from a single KT88 per channel. So I'm sure it is pushing the EL84s to their max. I backed down from a GZ34 rectifier to a 5V4GA to give them a little relief. It is easy to drive them into clipping but I don't listen at loud levels much anymore.

Overall a pleasant sound with nice vocals and clear string instruments. I like it better than I do when running 6V6s.

[oldominion]

So funny, in my Inspire Firebottle Universal SET I just swapped out my KT150's and Sophia 274B for Haltron 6V6 and a Sylvania VT244 (5u4G) and it sounds absolutely wonderful!

Might have to try the el84's. I've never cottoned to that tube like so many others in our hobby have. In fact, I've sold every el84 amp I've ever purchased, and somewhat quickly. I love it as a guitar amp tube but, again, have never really fallen in love with it as a hifi/audio tube. Still, I have a bunch of el84's that are gathering dust, including a quad of Mullards, so may have to give it a shot...

I was convinced I'd never take the KT150's/274B out but, as happens during the quarantine, was procrastinating and avoiding work so decided to mix things up. Man, am glad I did. On mellower stuff--listening to Brazilian Gal Costa right now--there is a smoothness, subtleness and, dare I say it, delicacy to the presentation that I guess I was sort of missing with the 150's.

ANyhow, good advice: keep as many tubes on hand as you can!

Would love to hear anyone's thoughts about 6V6 vs. 6L6. I have some of the metal ones and the cheap Russians that Dennis recommended me.

BTW, the Sophia 6SN7's are definitely settling down. Thus far, I like them but am pretty sure I've got plenty of vintage 6SN7 that sound just as good. They do appear to be stable--I'm not having much microphony UNLESS I touch the tubes while playing, which thankfully I don't often do!

[decooney]

Originally Posted by oldominion

..So funny, in my Inspire Firebottle Universal SET I just swapped out my KT150's and Sophia 274B for Haltron 6V6 and a Sylvania VT244 (5u4G) and it sounds absolutely wonderful!..

Excellent! KT150s sounded okay in my Inspire Hot Rod, and reportedly less romantic than 6V6 and other 6L6 tubes frequently mentioned here on AA over the past 2 years. However, not sure why, KT150s do sound quite different and operate warmer to touch in my current other brand monoblock tube amplifiers. Periodically noting references on other DIY forums about "needing to run KT150s hotter" at recommended ESA or at least Class A1 average ranges in order for them to sound their best, fwiw, YMMV.



...

[Bombadil]

I believe my amp runs 6V6s too hot. They sound shrill and give me headaches in a few minutes. By far my least favorite tube in my Inspire. I've tried 4 different brands, all vintage. They all sound about the same.

Even when I pair them with 5Y3 rectifiers they are still shrill and harsh.

Now I do like the 6L6GC in my amp,producing a nicely balanced, smooth sound across the board. As well as 5881 (but not quite as well) and KT66. But the Russian 6P3S-e is also on the bright side, great for detail and imaging but tiring after a spell. Should try those KT66 again, haven't listened to them in a long time and I remember having liked them a lot.

The "mellowest" tubes in my setup have been certain EL34 and 6CA7. Some to the point of sounding "veiled" and dark. I do have some vintage USA fat boy 6CA7s which sound good, not as detailed as other tubes. I like playing the blues through them, gives me the impression of listening in a night club.

[Bombadil]

Originally Posted by oldominion

So funny, in my Inspire Firebottle Universal SET I just swapped out my KT150's and Sophia 274B for Haltron 6V6 and a Sylvania VT244 (5u4G) and it sounds absolutely wonderful!

Does that Inspire run in triode mode? Mine runs in ultralinear. The label says "SET Fire Bottle" which implies it is configured for triode operation, but it isn't. One could never get 17 watts out of a KT88 running in triode. This certainly makes a difference.

I've swapped my KT150s back in, with a 274B, and I think it sounds great. The bass is deeper and tighter than with any other tube, while still producing very good vocals, details and imaging. But not the very best on details & imaging, close though.

My speakers go down clean and flat to 32Hz, with some output in the mid-20s. The KT150 is the only tube I've found that can go really deep while still maintaining some detail. Not as good as a SS amp but decent. The KT120 and KT88 do okay, with somewhat less presence.

In terms of clean highs and big soundstage, perhaps the best I've tried has been the Gold Lion KT77. Not overly bright like the 6P3S-e or 6V6, but clear & open with great vocals. Maybe a little edgy if one likes a more mellow tone or has forward-leaning speakers or a hard room. I've known people who hate them and consider them to be "SS-sounding." In my system & room they work well.

[bearcity]

Originally Posted by Bombadil

Does that Inspire run in triode mode? Mine runs in ultralinear. The label says "SET Fire Bottle" which implies it is configured for triode operation, but it isn't. One could never get 17 watts out of a KT88 running in triode. This certainly makes a difference.



I've swapped my KT150s back in, with a 274B, and I think it sounds great. The bass is deeper and tighter than with any other tube, while still producing very good vocals, details and imaging. But not the very best on details & imaging, close though.



My speakers go down clean and flat to 32Hz, with some output in the mid-20s. The KT150 is the only tube I've found that can go really deep while still maintaining some detail. Not as good as a SS amp but decent. The KT120 and KT88 do okay, with somewhat less presence.



In terms of clean highs and big soundstage, perhaps the best I've tried has been the Gold Lion KT77. Not overly bright like the 6P3S-e or 6V6, but clear & open with great vocals. Maybe a little edgy if one likes a more mellow tone or has forward-leaning speakers or a hard room. I've known people who hate them and consider them to be "SS-sounding." In my system & room they work well.

Bombadil,

Did you rewire your inspire to ultralinear? Never heard a nice word from Dennis about ultralinear. Surprises me he would build one in his “retirement”. Back in his Cary days yes. He had payroll to make. Now he pretty much seems to stick to his favorite circuit type. SE. Anyway, I’m curious.

[Bombadil]

Originally Posted by bearcity

Bombadil,

Did you rewire your inspire to ultralinear? Never heard a nice word from Dennis about ultralinear. Surprises me he would build one in his “retirement”. Back in his Cary days yes. He had payroll to make. Now he pretty much seems to stick to his favorite circuit type. SE. Anyway, I’m curious.

Dennis built it for someone, who then sold it to me. I sent him a photo of the underside and he said it was in original condition, just as he built it.

There are single-ended ultralinear, or SEUL, amplifiers.

It is possible that my amp is a SE-pentode or SEP, pushed to its absolute max. I think a KT88 might be able to produce 17 wpc at around 10% THD.

[Bombadil]

Mistake - delete if possible.

[nhparrot]

Originally Posted by oldominion

So funny, in my Inspire Firebottle Universal SET I just swapped out my KT150's and Sophia 274B for Haltron 6V6 and a Sylvania VT244 (5u4G) and it sounds absolutely wonderful! ....

Would love to hear anyone's thoughts about 6V6 vs. 6L6. I have some of the metal ones and the cheap Russians that Dennis recommended me.

I am a fan of 6V6 tubes in my system/room. I have tried 6L6, KT77, KT88, EL84, and 6F6; and to me the 6V6 has been the goto tube type. I have various 6V6, 6V6GT, and 5992 types I have tried (GE/Radiotron 6V6; Hytron, RCA, Pope, Visseau, Fivre 6V6GT; and Bendix 5992) and the Pope 6V6GT gets the most rotation in my Inspire amp.

[Bombadil]

Originally Posted by Bombadil

Dennis built it for someone, who then sold it to me. I sent him a photo of the underside and he said it was in original condition, just as he built it.

There are single-ended ultralinear, or SEUL, amplifiers.

It is possible that my amp is a SE-pentode or SEP, pushed to its absolute max. I think a KT88 might be able to produce 17 wpc at around 10% THD.

Looking at his currently posted for sale amps. They are described as SE Pentode (SEP) designs. And their output is 10 wpc.

As mine is rated at 17 wpc, it would seem that it would have to be SE Ultralinear. At least that's how I see it.