Dennis Had Inspire Amps

[Bombadil]

Originally Posted by FloridaBoy

KT120 power tubes and a new Genalex GZ34 rectifier.

That tube complement is high energy. The 6SL7's extra gain may be too much or the Ken Rad may not be a good match.

Yes, it is. My Inspire is a high energy design. Whereas a standard Inspire SE HO KT88 amp with KT88 power tubes, 6SN7, and GZ34 rectifier and with 15 wpc output transformers, produces 12 wpc, mine has 20 wpc output transformers, larger power supply, and with the same tube compliment, produces 17 wpc. I like KT120s in this amp. Bass is strong and relatively tight for a SE tube amp. Nice detail, open & natural soundstage and midrange. Drives my mid-efficient towers very nicely.

I have three other 6SL7 tubes, but don't know if I will try them.

[Musica Amantem]

Originally Posted by Bombadil

Yes, it is. My Inspire is a high energy design. Whereas a standard Inspire SE HO KT88 amp with KT88 power tubes, 6SN7, and GZ34 rectifier and with 15 wpc output transformers, produces 12 wpc, mine has 20 wpc output transformers, larger power supply, and with the same tube compliment, produces 17 wpc. I like KT120s in this amp. Bass is strong and relatively tight for a SE tube amp. Nice detail, open & natural soundstage and midrange. Drives my mid-efficient towers very nicely.

I have three other 6SL7 tubes, but don't know if I will try them.

I believe power is determined by the output tubes whereas the trannies and power supply provide that extra capacity for these to extend in dynamic peaks.

[Comzee]

Originally Posted by Musica Amantem

...did you try the 5AR4 or 5Z4? Those two are low-voltage drops and in my case work very nicely with the larger tubes like the 6550/KT-88, etc.

Curious about some of your favorites, which I've never heard yet, as these are rated substantially higher than my current "goto" rectifier, the SE 274B mesh plate.

I have not tried any 5AR4 (gz34 sub?) or 5Z4 yet.
Might just be me, but I find design trumps electrical specifications.

For example, the JJ 5U4 isn't great, but I found this odd Philco ST shaped 5U4 with hanging filaments, that's exceptional. Same model type, different designs, different sounds.

I'm sure there is credence in matching electrical parameters of the rectifier to the output tubes, it can get a bit head boggling.

If you want to try a 5R4 out cheap, I'd get the "GE NOS 5R4GYA"
You can get it for around $10-$20, plenty of them on eBay.

It's a bit bloomy, a little less detail than my best 5R4's, but it showcases the flavor of 5R4 well.

The RCA (st shape) 5R4 single bottom getter can be had for cheapish too, around $30-$40. It's similar to that GE, but without the bloom. A little brighter tho. In general all the 5R4 add a varying amount of brightness.

The 596 tube I have is ultra bright, while tubes like my Psvane 274b is pretty warm. Not so much on electical paramers, I more so try and match tubes based on tone. Example: Warm power tubes + neutral input + bright rectifier ,and try to blend sound signature like that.

The Philco ST shape 5U4 I mentioned is exceptional detail for a 5U4, but keeps the neutral to warm feeling of that model type, which is great.

[Bombadil]

Okay, I decided to try out another 6SL7, this time in a different compliment of tubes all around, all 30-50 years old. Sylvania 6SL7, Russian military 6P3S-e output tubes, Tung-sol 5U4GB. Listening to Patricia Barber's Cafe Blue, just as yesterday.

If anything, this combo is a smidgen more aggressive in the upper midrange and highs than yesterday's arrangment. This is cured by substituting my Westinghouse 6SN7GTB back in for the Sylvania 6SL7, which results in a beautiful, smoother presentation.

With the 6SL7, the detail and clarity is immediate and remarkable. Even enticing, for a few minutes. At low volume levels it is nice, with all of the strings, piano, percussion, and vocals being more evident. But at moderate volume, it is overwhelming to me. I will add that with all of this extra energy & detail, the soundstage it throws up is excellent.

Perhaps someday I will haul out my Spica TC60 speakers, which have a darker overall tone, and see how that combination works.

[Bombadil]

Listening to my music this morning and reflecting upon how much I enjoy the combination of my Inspire amp with my Von Schweikert speakers has me thinking of when I purchased my first audio system, way back in 1974. A Sherwood receiver, BSR turntable, Panasonic cassette deck and Dynaco A25 speakers. Quality sound wise, it blew away every other stereo system on my college dorm floor.

I count my blessings that I can sit here today, 43 years later, still enjoying music and having a vastly improved system. My Von Schweikerts have been along for the journey for 21 of those years (although vastly upgraded about 15 years ago). I appreciate that Dennis came along and built a high quality SE amp which produces sufficient power to drive these speakers.

[Musica Amantem]

Originally Posted by Comzee

I have not tried any 5AR4 (gz34 sub?) or 5Z4 yet.
Might just be me, but I find design trumps electrical specifications.

For example, the JJ 5U4 isn't great, but I found this odd Philco ST shaped 5U4 with hanging filaments, that's exceptional. Same model type, different designs, different sounds.

I'm sure there is credence in matching electrical parameters of the rectifier to the output tubes, it can get a bit head boggling.

If you want to try a 5R4 out cheap, I'd get the "GE NOS 5R4GYA"
You can get it for around $10-$20, plenty of them on eBay.

It's a bit bloomy, a little less detail than my best 5R4's, but it showcases the flavor of 5R4 well.

The RCA (st shape) 5R4 single bottom getter can be had for cheapish too, around $30-$40. It's similar to that GE, but without the bloom. A little brighter tho. In general all the 5R4 add a varying amount of brightness.

The 596 tube I have is ultra bright, while tubes like my Psvane 274b is pretty warm. Not so much on electical paramers, I more so try and match tubes based on tone. Example: Warm power tubes + neutral input + bright rectifier ,and try to blend sound signature like that.

The Philco ST shape 5U4 I mentioned is exceptional detail for a 5U4, but keeps the neutral to warm feeling of that model type, which is great.

I see, thanks for the tips!

[Musica Amantem]

Originally Posted by Bombadil

Okay, I decided to try out another 6SL7, this time in a different compliment of tubes all around, all 30-50 years old. Sylvania 6SL7, Russian military 6P3S-e output tubes, Tung-sol 5U4GB. Listening to Patricia Barber's Cafe Blue, just as yesterday.

If anything, this combo is a smidgen more aggressive in the upper midrange and highs than yesterday's arrangment. This is cured by substituting my Westinghouse 6SN7GTB back in for the Sylvania 6SL7, which results in a beautiful, smoother presentation.

With the 6SL7, the detail and clarity is immediate and remarkable. Even enticing, for a few minutes. At low volume levels it is nice, with all of the strings, piano, percussion, and vocals being more evident. But at moderate volume, it is overwhelming to me. I will add that with all of this extra energy & detail, the soundstage it throws up is excellent.

Perhaps someday I will haul out my Spica TC60 speakers, which have a darker overall tone, and see how that combination works.

I really need to find the time to try a 6SL7 myself. Since the original T-S, I haven't cared for those until now, out of curiosity and the fact I have several 6SL7's on hand to try.

Last night, I was favorably surprised by the combination of VA 6550's and the Shug CV-181 T (black coating). Now I believe this combo beats the otherwise very good GL KT-88, even with the same input tube. What I liked the most about this configuration is the highs never went into edginess, as I found with the GL KT-88 in the recent past. Its sound is full of body and the bass relatively powerful.

I believe during my earlier sessions these 6550's had not burn-in enough. They are still green, mind you, but seem to have settled much more since then, in comparison. They did not take too long to reach this stage and I believe will continue to improve with the hours. When they do, I'll pair them with my more open-sounding Super-Radiotron or Sylvanya 6SN7's (GTA and GTB, respectively), and see if the combination reaches the sound levels I would expect from a controlled 6550 being pushed for maximum detail and transparency (my goal effect). We'll see ...

[FloridaBoy]

Originally Posted by Musica Amantem

I really need to find the time to try a 6SL7 myself. Since the original T-S, I haven't cared for those until now, out of curiosity and the fact I have several 6SL7's on hand to try.
Last night, I was favorably surprised by the combination of VA 6550's and the Shug CV-181 T (black coating). Now I believe this combo beats the otherwise very good GL KT-88, even with the same input tube. What I liked the most about this configuration is the highs never went into edginess, as I found with the GL KT-88 in the recent past. Its sound is full of body and the bass relatively powerful.

I believe during my earlier sessions these 6550's had not burn-in enough. They are still green, mind you, but seem to have settled much more since then, in comparison. They did not take too long to reach this stage and I believe will continue to improve with the hours. When they do, I'll pair them with my more open-sounding Super-Radiotron or Sylvanya 6SN7's (GTA and GTB, respectively), and see if the combination reaches the sound levels I would expect from a controlled 6550 being pushed for maximum detail and transparency (my goal effect). We'll see ...

Do it.

[FloridaBoy]

Originally Posted by Comzee

I have not tried any 5AR4 (gz34 sub?) or 5Z4 yet.
Might just be me, but I find design trumps electrical specifications.

For example, the JJ 5U4 isn't great, but I found this odd Philco ST shaped 5U4 with hanging filaments, that's exceptional. Same model type, different designs, different sounds.

I'm sure there is credence in matching electrical parameters of the rectifier to the output tubes, it can get a bit head boggling.

If you want to try a 5R4 out cheap, I'd get the "GE NOS 5R4GYA"
You can get it for around $10-$20, plenty of them on eBay.

It's a bit bloomy, a little less detail than my best 5R4's, but it showcases the flavor of 5R4 well.

The RCA (st shape) 5R4 single bottom getter can be had for cheapish too, around $30-$40. It's similar to that GE, but without the bloom. A little brighter tho. In general all the 5R4 add a varying amount of brightness.

The 596 tube I have is ultra bright, while tubes like my Psvane 274b is pretty warm. Not so much on electical paramers, I more so try and match tubes based on tone. Example: Warm power tubes + neutral input + bright rectifier ,and try to blend sound signature like that.

The Philco ST shape 5U4 I mentioned is exceptional detail for a 5U4, but keeps the neutral to warm feeling of that model type, which is great.

Phiclo did not make that tube. No matter. I had a NU 5U4G years ago that was just magic in the rig I had at the time. I have no idea why but it was.

[Comzee]

Originally Posted by FloridaBoy

Phiclo did not make that tube. No matter. I had a NU 5U4G years ago that was just magic in the rig I had at the time. I have no idea why but it was.

Most likely a rebrand then.
It's got an oldschool type getter:

I wish I could post a hotlink for an album, but per forum rules I guess I'll spam some images (sry).


There was actually a good article in Tube Collector about getters in last months issue.

You can see here an early getter design patent (looks like that 5u4g getter):


Some later getter designs: