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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 17th Feb 2019, 6:40 pm   #61
barrymagrec
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Default Re: "Audio" Valves

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I think only the EB91 and 6H6 might be left. anything with gain will have been grabbed.
Not much call for either these days - needless to say I am not short of them.
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Old 17th Feb 2019, 6:45 pm   #62
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Default Re: "Audio" Valves

David, you have not mentioned EF80. They do have gain as made. I am therefore tempted to offer some used untested that I have at 10 a score!
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Old 17th Feb 2019, 6:57 pm   #63
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Not all NOS CV valves are necessarily genuine. One of the old hands at GEC mentioned that they had once had a number of CV valves returned under warranty that had turned out to be fakes. MOD had bought them cheaply from a dealer rather than directly from Marconi. The experts at Marconi could tell that they had actually been made in Russia, I think by Svetlana, without needing to dismantle the valves, by the distinctive markings made by the crimp tools that were clearly visible though the envelope. They could tell from these exactly which production line they had been made on. Naturally, they were not replaced for free!

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Old 17th Feb 2019, 7:15 pm   #64
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David, you have not mentioned EF80 ...
I'll mention the EF184. The valve museum says they were "purpose designed" and quotes Mullard's description: A frame-grid sharp cut-off pentode for use as an IF amplifier in television receivers. Sadly, there's been an awful case of "audio aficionados trying anything they can get their hands on" which has resulted in these being used NOT as IF amplifiers in television receivers !!!

Fortunately the audio aficionados (i.e. beasts) who perpetrated this wickedness have been identified. Their names were Arthur Radford and Arthur Bailey (there's another pair of Arthurs for you Andy). The scene of the crime was the phase-splitter of their STA100 amplifier, which dates from 1967 I believe https://www.radfordrevival.co.uk/literature/sta100/.

Since neither man is still with us I'm not sure how retribution can be exacted. Does anyone think we might, um, just this once, let it go ?

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Old 17th Feb 2019, 7:40 pm   #65
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Default Re: "Audio" Valves

I am no valve audio authority, but I strongly suspect that any valve that can be turned to amplifier use has been used by one company or another over recent years, and manufacturers will state what can be used as substitutes.
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Old 17th Feb 2019, 10:45 pm   #66
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Default Re: "Audio" Valves

I Don't think the price will ramp on the EF80 until just about everything else has been used up.

It's rather a good valve and definitely a success story, but it has a bit of an image problem, and in a market where image is everything......

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Old 17th Feb 2019, 11:17 pm   #67
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Default Re: "Audio" Valves

Quote:
Originally Posted by GrimJosef View Post
Quote:
Originally Posted by robinshack View Post
David, you have not mentioned EF80 ...
I'll mention the EF184. The valve museum says they were "purpose designed" and quotes Mullard's description: A frame-grid sharp cut-off pentode for use as an IF amplifier in television receivers. Sadly, there's been an awful case of "audio aficionados trying anything they can get their hands on" which has resulted in these being used NOT as IF amplifiers in television receivers !!!

Fortunately the audio aficionados (i.e. beasts) who perpetrated this wickedness have been identified. Their names were Arthur Radford and Arthur Bailey (there's another pair of Arthurs for you Andy). The scene of the crime was the phase-splitter of their STA100 amplifier, which dates from 1967 I believe https://www.radfordrevival.co.uk/literature/sta100/.

Since neither man is still with us I'm not sure how retribution can be exacted. Does anyone think we might, um, just this once, let it go ?
Ah, but Arthur and Arthur already had form. Bailey had used the ECF82 in his new audio phase-splitter design that Radford then used in his STA25 amplifier.

ECF82 was the Pro-Electron designation for the 6U8, developed by Tung-Sol in 1951 for use as a VHF TV triode pentode mixer-oscillator, but also said to be suitable for many other TV receiver functions.

The similar early TV triode pentode from Philips was the ECF80/PCF80, primarily a mixer-oscillator, but also said to be suitable for various other functions that were specifically delineated. The other applications for the pentode section included audio output.


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Old 18th Feb 2019, 1:01 am   #68
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Oh dear. And now I learn that Harold Leak was also guilty of taking a valve meant, primarily at least, for a higher calling and diverting it into one of his audio amps. The ECC33 in his TL/12 Point One was, according to the Mullard data sheet http://www.r-type.org/pdfs/ecc33.pdf, 'intended for use in flip-flop, scaling and computor (sic) circuits' .

One by one all my heroes are turning out to have been rogues ...

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Old 18th Feb 2019, 1:31 am   #69
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It gets even worse. Baxandall designed his famous tone control around the Mazda SP61, a high-slope TV RF pentode, although he concded that where less exacting results were acceptable, lesser valves such as the ECC40 could be used.

The SP61 was predecessor to the Mazda 6F13 which was followed by the 6F1. These two were broadly similar to the EF42 and EF80 respectively in the Philips series. I think that means that the EF80 now has its invitation to the audio party!


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Old 18th Feb 2019, 6:54 am   #70
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Default Re: "Audio" Valves

Wasn't the EF80 used as the audio output valve in some HMV TVs ?

A very versatile largely unsung hero of the valve world

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Old 18th Feb 2019, 9:45 am   #71
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The Thorn 980 used a PCF80 as the audio output valve.

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Old 18th Feb 2019, 10:22 am   #72
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The book; "Designing High Fidelity Valve ( or Tube ) Amplifiers by Merlin Blencowe is well worth a look. It gives a very detailed analysis of a whole range of E------- series valves together with lots of information of what is significant in most passive components.

ISBN 978-0-9561545-3-8

I ordered my copy from by local independent bookseller with no problems.
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Old 18th Feb 2019, 10:29 am   #73
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Default Re: "Audio" Valves

The same thing goes with semiconductors today. They develop a new device, maybe for a specific purpose or maybe to fill in a gap in a range then the marketing people take over.

Datasheets have a bullet list of features and applications. Marketing likes to claim every possible application and especially the latest fashionable ones.... you want to see the miscellany of semiconductors claimed to be just the thing for "The internet of things"

It wasn't quite as brazen same in the valve era, but they knew that a sale was a sale was a sale.

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Old 18th Feb 2019, 2:44 pm   #74
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Default Re: "Audio" Valves

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Originally Posted by Cobaltblue View Post
Wasn't the EF80 used as the audio output valve in some HMV TVs ?
The EF91 was used as an output valve in at least one model of TV!

[Now to start promoting EF91-based audio (headphone?) amps: And do EF91s with the blue coating on the inner of the glass sound 'better' than those without? And do Mullard EF91s sound better than Brimar's blue-bandless equivalent the 6AM6?]
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Old 18th Feb 2019, 6:30 pm   #75
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They still haven't reached a consensus on which ECC83 sounds best, and look how long diligent listeners have been working on that.

EF91, 6AM6, Z77.... hmm, anything with a Z or a Q in it sounds exotic or special. Mind you Zs and 7x are a bit angular and pointy. The Z77 isn't going to sound smooth, is it?

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Old 18th Feb 2019, 7:27 pm   #76
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Marconi Z77s were used in the record / replay amplifier of the EMI TR50 and TR51 tape machines - I never tried the blue Mullard EF91s to see if they were better though...
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Old 18th Feb 2019, 7:30 pm   #77
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You seem to be confusing guitar amp's and audio amp's (although I suppose both are audio amp's, but you know what I mean).

I have never seen anyone suggest any valve swapping in audio amp's outside of what equipment manufacturers or websites such as the Valve Museum suggest, or very close equivalents with different pin-outs (which require adapters or rewiring).

So far as colours go, go back enough decades and the Mullard white and yellow printing presumably provided some fun because they were variously believed to show different spec' ranges, different tolerances etc. etc. etc.. Nowadays I think that the concensus was that yellow print were sold largely to OEMs, everyone else got white, but that was not infallible. I have never heard anything mentioned about significance of print colour except for Raytheon valves (IIRC) - older valves (including long plates) were printed in yellow, but the company changed to red printing towards the end of their making valves.

As for what is "best" - just like beauty, beer, and even music, would you believe, that really is down to the beholder/drinker/listener, even ignoring amp design to amp design differences.

All of this micky-taking is 20(+) years too late for anyone serious about hifi, rather than valve-collecting sheep.
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Old 18th Feb 2019, 7:57 pm   #78
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Odd comments.

I have a very large and heavy Solartron (?) PSU, 0-500V at 500mA, that uses five EL34's in the series pass, and these were XF1's!

I do hope the market stays healthy, I have a good pile to pass on.

You would be surprised just how often valve based equipment turns up for sale. I bought a test set from Westland Helicopters, 33 valves in it. Also oscillators and similar by old British manufacturers. Oscilloscopes of course, buy the valves by the hundred there.

With miniature switching PSU's I can't see why the TV versions, PCCxxx, of audio valves can't be used in amplifiers. Prices suggest that this doesn't happen.
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Old 19th Feb 2019, 1:17 pm   #79
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Originally Posted by Dave1000
I have never seen anyone suggest any valve swapping in audio amp's outside of what equipment manufacturers or websites such as the Valve Museum suggest, or very close equivalents with different pin-outs (which require adapters or rewiring).
Have you never visited an audio website? Some people encourage valve swapping (in audio i.e. not guitar amps), other go in for capacitor swapping or cable swapping. In a sufficiently poor circuit it might even have some effect.

Quote:
Originally Posted by woodchips
With miniature switching PSU's I can't see why the TV versions, PCCxxx, of audio valves can't be used in amplifiers. Prices suggest that this doesn't happen.
Some DIYers use TV valves for audio. Commercially it is less likely for two reasons:
1. commercial audio mainly wants to use valves still being produced
2. it might not look good in an advert to say that the valves used in this expensive audio amplifier were originally designed 60 years ago to act as a sync separator or multivibrator in a TV, and we found some in the back of a warehouse
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Old 19th Feb 2019, 3:57 pm   #80
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With miniature switching PSU's I can't see why the TV versions, PCCxxx, of audio valves can't be used in amplifiers. Prices suggest that this doesn't happen.
Even silicon in the PSU, where it's safely out of the audio path, is too much for some people.

I know I used a semiconductor-stuffed inverter PSU (with MOSFETs! and a CMOS IC!) in my "PPA-80" design; but a mechanical vibrator would have required a bigger transformer (for the lower frequency), a more powerful valve (to drown out the sound of the vibrator) and a bigger battery, so I plead mitigating circumstances!
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