Dennis Had Inspire Amps

[Bombadil]

Philco did manufacture some of their own tubes, tube code of 260. However they contracted most of them out, with the majority being manufactured by Sylvania. There was a Sylvania-branded 5U4 which had hanging filaments, so perhaps it was made by them. I don't have a list of tubes manufactured by Philco, but they had a plant in Lansdale, PA.

[Musica Amantem]

Originally Posted by Bombadil

Philco did manufacture some of their own tubes, tube code of 260. However they contracted most of them out, with the majority being manufactured by Sylvania. There was a Sylvania-branded 5U4 which had hanging filaments, so perhaps it was made by them. I don't have a list of tubes manufactured by Philco, but they had a plant in Lansdale, PA.

Excuse my ignorance: What is a hanging filament design and what is it supposed to achieve? The limited things I learn in this hobby are usually carried over to my rig's improved sound trends ...

[Bombadil]

They had center filament supports.

[Musica Amantem]

Got it. Thanks!

[Comzee]

I know I've seen many people use these, but I wanted to ask to be safe.
Is the EL34 ok to use in the SE HO Fire-Bottle?

I know it's a pentode instead of beam tetrode, so pins 1 and 8 have to be connected on the tube socket for this to work.

[Musica Amantem]

Relative to its cousin KT-88, the 6550 displays a slight roll-off in both frequency extremes. This offers a tradeoff: It is robust enough to handle the most demanding input tubes (usually tapping the latter's transparency) without the burden of low frequency boldness or potential stridency in its high freq extension.

The cited characteristic makes the 6550 an all-around tube which sounds good in most cases, but ultimately cannot compete with a more extended output tube alternative when the latter is driven by the ideal input tube. Such is the case of the KT-88 (harder to match optimally, but surely paying off in sound quality of detail and neatness when duly controlled, which I have yet to achieve), the KT-66, and the best IME, the KT-77 (another hard to optimize tube alternative, which I finally managed to control harvesting an awsome payoff).

Having apparently settled down, my VA 6550's can now take on the demanding Psvane CV-181 T-II, which pushes hard for over-extension in both ends, but its radical behavior is neutralized by the aforementioned 6550 roll-off. This output tube offers great detail but is not as neat sounding as others, especially when compared to the KT-77 given its slightly limited tail extension. However, the 6550's overall presentation is very good, offering nice soundstage, detail, controlled bass and presence.

I have been listening to my KT-88's for over a year now, and I still cannot dial it-in optimally, whereas the 6550 is already my "pet", which confirms the former's hard to manage overextension demands a "surgical" input tube approach, an even tougher proposition than the KT-77, which is saying a lot.

Next is keep hammering on the KT-88 with other input tube alternatives and then reivindicate my former favorite, 6P3S-E's.

[FloridaBoy]

Originally Posted by Comzee

I know I've seen many people use these, but I wanted to ask to be safe.
Is the EL34 ok to use in the SE HO Fire-Bottle?

I know it's a pentode instead of beam tetrode, so pins 1 and 8 have to be connected on the tube socket for this to work.

Yes, you can use EL34's but you may be disappointed if you have GL KT77's. YMMV.

[Comzee]

Originally Posted by Musica Amantem

The cited characteristic makes the 6550 an all-around tube which sounds good in most cases, but ultimately cannot compete with a more extended output tube alternative when the latter is driven by the ideal input tube.

Next is keep hammering on the KT-88 with other input tube alternatives and then reivindicate my former favorite, 6P3S-E's.

I agree with all of this. 6550 is great, but doesn't have kt88 extension.
I find the 6P3S-E has ridiculous detail retrieval, (like 6L6), but even less extension than the 6550.

Originally Posted by FloridaBoy

Yes, you can use EL34's but you may be disappointed if you have GL KT77's. YMMV.

Thanks, and interesting, I don't have either EL34 or KT77, those are the last common type of power output tubes I could get, I pretty much own everything else. Although, I haven't delved into adapters for power tubes yet...

[Bombadil]

As noted above the EL34 is perfectly safe. It is the favorite tube for many tube amp lovers. Perhaps the most popular tube in the world. Mostly due to its midrange. But mostly used in push pull designs.

[Musica Amantem]

Comzee: I find the 6P3S-E has ridiculous detail retrieval, (like 6L6), but even less extension than the 6550.

Precisely because the 6P3S-E is so detailed and transparent, I find it extended in the highs but particularly limited in the lower frequencies. This translates into a lack of sound body/texture that my SUB can only partially address ... I'm hoping to mate it with a more synergic input tube while using 27's in the preamp (thicker sounding than my 56's, which are quite open and airy) to try and get the most out of an otherwise outstanding tube. I like 6L6's in this amp, but after listening to the Kink-Tetrode alternatives (66z and 77) the former would need to be pushed more into the low-mids and lower frrequencies by a suitable (if feasible) input/rectifier tube combination while preserving their dynamic transparency.