Hifi, why bother?

[Amie]

Mike.

If the amplifier that you were working on had modern prodution valves then are any of the Russian/Czech/China products marked as 84's actually the guts of something generic just marked for familiarity?

6BW6 is a beam tetrode similar size/spec to the EL84....other valve  could be a "modern" production 6L6G... Original production at Brimar were identical structure just in different envelopes.

Yet another deception of the punters?

Thanks
Amie.

[Amie]

Hi

Just fact checked myself in above post, the 6BW6 is identical to the 6V6GT NOT the 6L6 also JJ the valve manufacturer in the Slovak republic makes current versions of the 6L6 and 6V6.

Amie.

[Kalee20]

The next step is to build amplifiers with "high-but-nice" distortion. That's much harder, but he's done it!

I could probably come up with a solid-state amplifier with 8% distortion. But I guarantee it will sound horrible. So, Andy has done something that I can't do. And if Andy and I were running hi-fi amplifier companies, he'd be able to sell amps for huge sums, whereas I'd be selling at much more modest prices - his amplifiers will stand out as being different and interesting, but mine will be merely "ordinary". That will cause me great pain because I know my amplifiers are better by any technical description, but he'll have the luxury company car and I'll still be struggling to put food on the table. Joking aside, you might actually be onto something with this!

That's the sad bit, to engineers - how to even aspire to the 'nice' sounding amplifier, and how to know, from measurements, that you're there? And then, to make money from it to buy components, instruments, and engineering time to make the next 'bad' amplifier?

And the people who can, and do, design amplifiers as precision pieces of analogue circuitry - their products aren't wanted!

Whereas Andy's bad amplifier - it's so bad that it's good!

I mentioned in passing that some amps have a triode/pentode mode switch - they achieve a similar thing.

You did indeed. I should have acknowledged it!

If the amplifier that you were working on had modern prodution valves then are any of the Russian/Czech/China products marked as 84's actually the guts of something generic just marked for familiarity?

6BW6 is a beam tetrode similar size/spec to the EL84...

Good point - Mike's "EL84" could be another valve, remarked. Which would explain it looking like a BT.

It couldn't actually be a 6BW6, because the pinout is different from EL84. Unless... it not only had the 6BW6 guts, but was then pin-connected like EL84 before fusing the envelope on and sucking out the air. In which case, the deception was obviously intended at the factory!

Though, if that was the case, I'd rather like one to do a trial swap...

[Mike Watterson]

Good point - Mike's "EL84" could be another valve, remarked. Which would explain it looking like a BT.

It couldn't actually be a 6BW6, because the pinout is different from EL84. Unless... it not only had the 6BW6 guts, but was then pin-connected like EL84 before fusing the envelope on and sucking out the air. In which case, the deception was obviously intended at the factory!

Though, if that was the case, I'd rather like one to do a trial swap...

I didn't examine the valves closely at all. It was definitely labelled EL84. You can't easily see the construction of an EL84, certainly from the top due to the mica support.
https://www.radiomuseum.org/tubes/tube_el84.html

Amie, the 6BW6 is maybe more like 4W to 4.5W and the EL84 about 5W to 6W (both optimistic Class A actual output power. The EL84 might give nearly 20W class B push-pull as the dissipation is a bit over 12W. ). The Audio transformer was certainly smaller than most valve radios. It seemed like a mad Guitar amp. The spring line reverb was just like in an old Marshall and had open circuit transducers. I gave him an old one from a marshal.
The Octal was certainly a KT6x, but not the big one, the one more like an EL33 shape.

The 6BW6 (noval) is similar to an Octal 6V6, but obviously not the same valve. The B7G 6AQ5 = EL90 was maybe more popular in USA radios and used in some early 1960s smaller German sets. I'm not sure if the 6AQ5 and 6BW6 are exactly the same valve in a different package. They are similar and possibly either can work in a 6V6 circuit with an adaptor.

Anyway my original point was that the amp was an example of fashion and style more than a sensible valve guitar amp that would have been better with 2 x EL84 rather than 2 valves with a changeover switch. Why not even a centre off switch rather than a printed warning not to changeover while the amp is on?

The guitar player eventually admitted that he couldn't hear the difference between the two valves when I said I couldn't. Not as if one was Triodised either!

Edit:
I think the 6BW6 / 6AQ5 are shorter than an EL84?
https://www.radiomuseum.org/tubes/tube_6bw6.html
The B7G version looks tall as the envelope is skinny. It's actually obviously shorter in real life. I have an AEG Bimby with an EL90. Gets hot but not as hot as an EL84!
https://www.radiomuseum.org/tubes/tube_6aq5.html
https://www.radiomuseum.org/tubes/tube_el90.html

[valvekits]

Anyway my original point was that the amp was an example of fashion and style more than a sensible valve guitar amp that would have been better with 2 x EL84 rather than 2 valves with a changeover switch. Why not even a centre off switch rather than a printed warning not to changeover while the amp is on?

Hi Mike

The amp that you describe sounds a bit like an amp I repaired about 15 years ago. I think it was called a THD Univalve (single ended class A) and was an amp that you could swap the octal valve using an adapter to give you whatever sound made you feel warm and fuzzy or whatever. It had a tendency to run some valves cherry red, - a bit of a fad really.

Eddie

[Kalee20]

The 6BW6 (noval) is similar to an Octal 6V6, but obviously not the same valve. The B7G 6AQ5 = EL90 was maybe more popular in USA radios and used in some early 1960s smaller German sets. I'm not sure if the 6AQ5 and 6BW6 are exactly the same valve in a different package.

I made an amplifier some years ago using a pair of 6AQ5's. It works well (dunno if Andy would think it sounds 'nice'). But they do run stinking hot. The chassis runs in open air...

I don't think the 6AQ5 is a 6BW6 in a B7G bottle - the 6BW6 that I have nearly fills the B9A diameter so wouldn't fit in B7G.

And although I have 6V6's, they are blackened on the inside. I have never opened one - but doubt that the guts are small enough to fit in a B9A-sized jar. (Well, the 6V6 was first, in the days when B9A and B7G weren't even thought of, so why would they not take advantage of the nice big Octal glass?)

Although they all have just about identical characteristics, I reckon there are 3 different electrode geometries.

[Amie]

Hi all.

The 6BW6 (noval) is similar to an Octal 6V6, but obviously not the same valve.

And although I have 6V6's, they are blackened on the inside. I have never opened one - but doubt that the guts are small enough to fit in a B9A-sized jar. (Well, the 6V6 was first, in the days when B9A and B7G weren't even thought of, so why would they not take advantage of the nice big Octal glass?)

http://www.r-type.org/exhib/aaa0343.htm

http://www.r-type.org/exhib/abh0037.htm

Just for comparison.

Valve museum states of the 6BW6 that it is the same valve stuffed into noval glass. brimar specs are the same, even if structure is different.

Thanks.
Amie.

[Mike Watterson]

Although they all have just about identical characteristics, I reckon there are 3 different electrode geometries.

I would think so. Shrinking was done of the first Sylvania 1.4V valves from loctal/Octal button base to RCA B7G button base. Some nearly identical characteristics. Octal valves actually switched from pinch to button bases. Typically the tube sits deeper into a collet rather than on a higher Bakelite surround, though the wires are still soldered into the pins.

The DL92 was mentioned earlier (1948?). Either a copy or likely licenced 3S4 (November 1940) designed by RCA based on the Sylvania Octal 3Q5 (= DL33). That's why the DL92 is a Beam Tetrode.
https://www.radiomuseum.org/tubes/tube_3q5.html

The 1C5 is the 1.4V only 100mA version, the DL2 is the P8 Edge connect version. The 1S4 = DL91 is the B7G version (1940 and 1948).

Probably all these were Beam Tetrodes.

Philips did rimlock 8 pin base valves before the 1.4V B7G. Telefunken had slightly lower filament voltage and parallel only Y8 base (for NiCd) from during WWII up to early 1950s when the last makers switched to B7G.
Early 1.4V valves had nickel filaments due to accuracy issues with tungsten for series operation. The later Philips 25mA series have tungsten filaments, which might be spring loaded. The Russian rod tubes have spring loaded filaments. The DK40 was roughly 1LC6 performance so used on some UK SW sets as the DK91 was poor. US makers used the US version of the DK91 only till the 1L6 was available. The DK92 is similar performance for SW. The DK96 is poor at higher SW, so the DK92 was used virtually till battery valve radios ceased.

[Mike Watterson]

People have made power amps using up to 60 op-amps in parallel.
Allegedly the noise is lower (correlation) and it's in TI and ADI tech notes about paralleling two op-amps for more power, or four for lower noise and lower offset.
There is a unity gain buffer amp for op-amps. Given the excellent high power National/TI parts with cheap kits on ebay I'm baffled.
I'd go for the "perfect amp" and adding in distortion as or if required.

[Kalee20]

http://www.r-type.org/exhib/aaa0343.htm

http://www.r-type.org/exhib/abh0037.htm

Just for comparison.

Valve museum states of the 6BW6 that it is the same valve stuffed into noval glass. brimar specs are the same, even if structure is different.

I think the structures are different - but yes, agree the characteristics are the same.

Measuring as accurately as I can, through the envelope:

6V6 anode support pins (visible on top mica) are 19.5mm apart, so wouldn't fit the B9A.

6BW6 anode is approximately hexagonal, 14mm across-flats, so isn't going to go in the B7G envelope.

6AQ5 anode is circular, 12.5mm dia.

The 6AQ5 and 6BW6 electrode structures look the same height. The 6V6GT isn't visible (though I may have a 6V6G, which hopefully will be).

They're definitely different dimensionally.

What is surprising, is that the three valves have the same heater rating, 6.3V 0.45A. Somehow, I'd have expected the small B7G version, with its anode enclosing things more, to need less power. Bit it doesn't.