Dennis Had Inspire Amps

[Bombadil]

Originally Posted by Comzee

An interesting quote from the Moon Audio write up.

"the rectifier tubes should be of the direct heater type like the 5Y3, 5U4, 274B or NOS and factory fresh direct heated filament types. The indirect filament type like a 5AR4 are fine to use but to his ear they do not even come close to a directly heated filament type."

My Fire-Bottle shipped with 5AR4/GZ34, which I can assume is "indirect filament type" based on the above quote.

I'm wondering why Dennis would say indirect filament rectifiers are bad, then use one in his Fire-Bottle. Thoughts?

That's a good question. My guess is that he was maximizing the output power in your amp. In my communications with Dennis, he never recommends the 5AR4 / GZ34 for best sound. My amp, the 17 watt KT88 one, also is shipped with a GZ34 as stock, as that is the only way it can produce 17 watts. It makes 15 watts with a 5U4G.

[Bombadil]

Originally Posted by nhparrot

you can use a 5U4G with the 6V6GT tubes, but need a 5Y3 for the vintage 6V6. I produced somewhat of a guide for the amp I have, which was built on 1/2/15. There is a tube chart in it

https://drive.google.com/open?id=0Bw...EYza1l5SDhQNzA

That link doesn't work for me.

[CoGT3]

Try this:

https://drive.google.com/open?id=0Bw...EYza1l5SDhQNzA

[nhparrot]

Originally Posted by Bombadil

That link doesn't work for me.

Try this https://drive.google.com/file/d/0Bwg...ew?usp=sharing

[nhparrot]

Originally Posted by Comzee

This is another thing I'm trying to find out.
Dennis refers to the "5U4G" as being an option for the rectifier.

Although, he linked me a "5U4GB" which is a sub version.

I was thinking of buying the Emission Labs 5U4G mesh, but it says:



Psvane makes a decent looking 5U4G, but again not B version.

The best 5U4GB option out there seems to be an RCA NOS.

Tube# - Base - Fvolt - Famp - Vdrop - MaxPmA - MaxPv - notes
5U4-G - 5T - 5.0 - 3.0 - 44 - 225 - 450 - octal 5Z3
5U4-GA - 5T - 5.0 - 3.0 - 44 - 250 - 450
5U4-GB - 5T - 5.0 - 3.0 - 50 - 275 - 450

[Comzee]

Originally Posted by nhparrot

Try this https://drive.google.com/file/d/0Bwg...ew?usp=sharing

Originally Posted by nhparrot

Tube# - Base - Fvolt - Famp - Vdrop - MaxPmA - MaxPv - notes
5U4-G - 5T - 5.0 - 3.0 - 44 - 225 - 450 - octal 5Z3
5U4-GA - 5T - 5.0 - 3.0 - 44 - 250 - 450
5U4-GB - 5T - 5.0 - 3.0 - 50 - 275 - 450

Both quite helpful, thanks for the info!

[Bombadil]

Dennis seems to never list the 5V4 rectifier in his list of different rectifiers to use in his amps. I suspect it is because it isn't very common. I happen to have 3 that I got out of a big bag of tubes several years back. I like them. I'm using one to drive 6V6s in my amp right now. It pushes those tubes a little harder than a 5Y3GT, but less than a 5AR4. It's indirectly heated, like a 5AR4.

I had my amp and the 6V6s running for about 6 hours today. Quite enjoyable. With those lower wattage power tubes, the output transformers were only slightly warm even after 6 hours.

[robert_kc]

Originally Posted by nhparrot

Try this https://drive.google.com/file/d/0Bwg...ew?usp=sharing

Nice documentation! Thanks

[robert_kc]

Originally Posted by Bombadil

Dennis seems to never list the 5V4 rectifier in his list of different rectifiers to use in his amps. I suspect it is because it isn't very common. I happen to have 3 that I got out of a big bag of tubes several years back. I like them.

After additional tube rolling this summer, the 5V4 is now one of my favorite rectifiers. (And they’re cheap.) I have a variety of USA 5V4G and 5V4GA, with more on the way.

One of my favorite combinations is now KT150 / 5V4 / 6DJ8.

The 5V4 also sounds good with the 6L6GC tubes. A particularly good looking combination is the new production Tung-Sol 6L6G (large ST shaped 6L6GC) and 5V4G (ST shape).

My other favorite sounding combination is: GT6L6 GE (performance rating 5) / 5AR4 / 6DJ8.

These results are based on my Inspire “Fire Bottle” SE Stereo Tube Amplifier HO (originally equipped with KT88 / 5U4 / 6CG7), Klipsch RF-7II, and Klipsch R-115SW sub, playing a wide variety of classical music, plus some big band music.

I have some vintage 6L6GA (ST shape) arriving tomorrow …

[Analog Addict]

Originally Posted by Comzee

Thanks for the info @Bombadil

Here's another curious thing to me.

I know these amps are somewhat related, my "Fire-Bottle" and the "Inspire IHA-1"

An interesting quote from the Moon Audio write up.

"the rectifier tubes should be of the direct heater type like the 5Y3, 5U4, 274B or NOS and factory fresh direct heated filament types. The indirect filament type like a 5AR4 are fine to use but to his ear they do not even come close to a directly heated filament type."

My Fire-Bottle shipped with 5AR4/GZ34, which I can assume is "indirect filament type" based on the above quote.

I'm wondering why Dennis would say indirect filament rectifiers are bad, then use one in his Fire-Bottle. Thoughts?

I'm not sure that you can infer that statement from the Moon Audio Quote. Dennis will use whatever sounds good and doesn't red plate the outputs or arc the rectifier. Our last listening session we rolled everything from a 5R4, 5Y3, 5U4 and a 5AR4 through the amp. The main thing is that each of these different rectifiers have a different voltage drop effect on the B+/Plate voltage, and it would be possible to over power some tubes, especially older 6V6 variants with the smaller voltage drop variants. Another consideration, although not in these amps, is not using a rectifier with a filament current draw higher than the filament current rating of the power transformer. For example, a 5U4 draws 3 amps and a 5AR4 draws 2 amps. If your PT is only rated for 2.5 amps/5V, you can burn out the filament winding, or overheat the PT....