Dennis Had Inspire Amps

[FloridaBoy]

Originally Posted by Bombadil

My chassis is 14.25" x 7.5" I've been under the impression that this is a bit larger than the standard. But don't really know.

My chassis is the same size. The amp runs hot with KT88's etc.

[Wgarcia]

The heat really can't escape from my HO, but since it hasn't melted I'm OK with it (I'll look inside for shrink wrap issues). Also, I'm a little confused as to which rectifier to run with KT77s…my options are a 274B, GZ34, and the supplied 5Y3S. I'm leaning toward the 274B from what I've gleaned from these posts, but advice is welcome.

[Comzee]

Originally Posted by Wgarcia

my options are a 274B, GZ34, and the supplied 5Y3S. I'm leaning toward the 274B from what I've gleaned from these posts, but advice is welcome.

I've tried many rectifiers, to name a few:

JJ GZ34, J 5U4G, RCA NOS 5v4g, JAN-Sylvania 5Y3WGTA, Mullard f31 fat base gz34, Preferred Series 274b, Bendix 6106 (5Y3 Variant), Sophia Electric 274b mesh, Psvane 274b treasure mkii, Sylvania 5931 (5U4WG sub), GE NOS 5R4GYA, Philco Sylvania 5U4G Hanging Filament, RCA 5R4GY hanging filaments single bottom getter, PHILIPS 5R4GYS (made in holland), NOS 596 (sub for 274A 5U4G 5R4), 1940s RCA Jan Crc 5R4GY hanging filaments double bottom getter

My favorite overall is the 596 rectifier (has same specs as 5u4g).
GZ34 boost low end in my experience, but decrement detail(resolution). I'd actually say the GZ34 I've tried are my least favorite type, and to extend that the GL gz34 severely decreases detail, sparkle, and air. (YMMV IMO)

Princess 274b is decent, but middle of the pack for me. I like 5u4 and 5r4 the best. There are ideal pairing I have that take into consideration the input and output tubes I'm using. In that vain what works best for the kt77 I'm not sure, it's one of the few output tubes I don't own.

I think gz34 has potential for me, but I'm not willing to spend $300+ on a metal base version from Mullard. The F31 fat base was superior to the GL for sure, at least for me, but still those are expensive.

I've found since gz34 are hyper common/popular, it's insanely hard to find good NOS variants for cheap, while 5u4 and 5r4 are easy to find the "holy grail" versions for a bargain if you look long enough.

To cap off, I think the 274b might be your best bet for detail, gz34 if you need low end, 5y3 idk. I own a few 5y3 including the Bendix, but I've never loved them like my 596.


p.s. @pstrisik

Thanks for the info. In that sense there's probably nothing wrong with my fire-bottle, and no reason for concern or vent mods.
The rubber baking off now makes sense, and the two resistors in the back probably only started melting for two reasons, #1 they were smashed against the resistors, #2 even tho the caps are rated for high degrees, the covering and adhesive the "hifi" brand used on them is probably cheap and came unglued from prolonged heat.

One last thing: I've read the U52 rectifier is exceptional, but again one of those holy grail tubes, I can't find one for under $400 myself. If I ever see one <$200 I'd snap it up.

[Bombadil]

I have a fair number, but not as many, rectifiers too. Maybe 15-17 or so. But my experience in hearing differences between them is much different than Comzee's. Within a rectifier type, I hear no differences between them. I can hear differences between 6SN7s, sometimes fairly significant differences. I hear differences between 6SN7 vs 6SL7 tubes. But between about 10 5U4GB & 274B rectifiers, they all sound the same to me. Switching between GZ34 to 274B to 5V4, I hear small differences.

A friend loaned me an expensive Psvane 274B and I compared it to my 1950s vintage Motorola 5U4GB and a Tubestore Preferred 274B (which Dennis supplied with my amp). I couldn't detect the slightest difference in sound.

The inexpensive JJ GZ34, which also came with my amp, is fine too.

I basically try to match my rectifier to my output tubes in order to maximize the strengths of each output tube type. Using my 5V4GAs with 6V6s, 5U4GB/274B with most output tubes, and GZ34 with KT88/KT120 (and occasionally KT66). As to which 5U4GB/274B or GZ34 I use, I pick the one which I think looks best with a specific output tube. Or if I'm feeling sorry for a particular rectifier tube which hasn't been used in a long time.

I am not alone in this opinion. When this has been discussed on the Audiokarma board, most people will say that they hear no differences. A few will claim that they do.

[Bombadil]

Originally Posted by Wgarcia

The heat really can't escape from my HO, but since it hasn't melted I'm OK with it (I'll look inside for shrink wrap issues). Also, I'm a little confused as to which rectifier to run with KT77s…my options are a 274B, GZ34, and the supplied 5Y3S. I'm leaning toward the 274B from what I've gleaned from these posts, but advice is welcome.

I would run a 274B or 5U4G/GB with KT77s. Well, that is what I actually do when I'm using KT77s. This would push another watt or two out of them, as compared to using a 5Y3S. But that doesn't mean you would like this combination better. In your system and using your music, you might prefer the KT77s running a little more relaxed. Given that you can pick up 274B/5U4G tubes for $10-$25, I'd grab one and run a comparison.

[Wgarcia]

I've heard differences among the little collection I now have, and as long as the Shuguang 274B continues to sound OK it gets to stay due to its general crazy look, and I'll try it with the 77s.

[FloridaBoy]

Originally Posted by Wgarcia

The heat really can't escape from my HO, but since it hasn't melted I'm OK with it (I'll look inside for shrink wrap issues). Also, I'm a little confused as to which rectifier to run with KT77s…my options are a 274B, GZ34, and the supplied 5Y3S. I'm leaning toward the 274B from what I've gleaned from these posts, but advice is welcome.

Try them all but I think you will prefer the 274B.

[BearCityUSA]

This in today from Dennis. Can't wait to hear it.
IMG_0942.JPG

[FloridaBoy]

Tell us more BC.

[BearCityUSA]

Well this is my 2013 vintage KT66/88/120 which I had Dennis do the IIPS to. Different than others, this chassis is as big as the PSE so there is a lot of space in there. Instead of transitioning to ss rectification which he typically does He had Straitwire drill a hole for a second rectifier tube. The rear right is still acting as a ac-dc rectifier. The front right direct heated rectifier tube is the IIPS "nasties" blocker. I can tell this pict shows its 'just wired' state. It is sitting directly on the table. No bottom plate and feet. Anticipation is killing me.