UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > Components and Circuits

Notices

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.

Closed Thread
 
Thread Tools
Old 15th Feb 2019, 9:16 pm   #1
Dave1000
Retired Dormant Member
 
Join Date: Feb 2019
Location: East Midlands, UK.
Posts: 36
Default "Audio" Valves

Forgive me, an audiophool, for seeking some information from the experts.

I use a valve pre-amp that uses ECC82 and ECC83 in the signal path and although the differences in sound are slight, they are nonetheless obvious. I can change things, or not, and ask my partner if she hears anything different, and if she does, what, and she hears what I hear, so my scepticism disappeared long ago.

As for paying more than something like £15 for a valve though...…………….

Anyway, to my question.

Many of the audiophools insist that the VAST numbers of NOS valves, not least ECC83, are coming from defence stocks across the world. I am far from convinced as most defence stocks, irrespective of what country is involved, usually have plain boxes and also a defence type designation/label - such as CV4004. The other favourite is that they are coming from pre 1970's radiograms and amplifiers, as opposed to radios/TVs.

Does anyone have a genuine grasp as to where the major volumes of ECC83, ECC82 (and other double triodes), were used at the time of their mass production?
Dave1000 is offline  
Old 15th Feb 2019, 10:16 pm   #2
M0FYA Andy
Nonode
 
Join Date: May 2007
Location: Preston, Lancashire, UK.
Posts: 2,510
Default Re: "Audio" Valves

Surely ECC82s and ECC83s were very much 'general purpose' valves used throughout electronics in their day, domestic, military, industrial, computing, just about everywhere. Totally commonplace.

Andy
M0FYA Andy is offline  
Old 15th Feb 2019, 10:43 pm   #3
evingar
Octode
 
evingar's Avatar
 
Join Date: Oct 2003
Location: Newbury, Berkshire, UK.
Posts: 1,770
Default Re: "Audio" Valves

Agreed!
A basic workhorse. I have many used ones hooked out of a wide array of equipment and a few new in box ones waiting for a project.
My ears are far too old to hear any subtle differences these days !
__________________
Chris
evingar is offline  
Old 15th Feb 2019, 11:14 pm   #4
vidjoman
Dekatron
 
Join Date: Jun 2013
Location: East Sussex, UK.
Posts: 3,315
Default Re: "Audio" Valves

Quote:
Originally Posted by evingar View Post
My ears are far too old to hear any subtle differences these days !
Perhaps it's to do with the colour of the print. Maybe, like me, your ears are not sufficiently tuned to colour.
vidjoman is offline  
Old 15th Feb 2019, 11:19 pm   #5
Dave1000
Retired Dormant Member
 
Join Date: Feb 2019
Location: East Midlands, UK.
Posts: 36
Default Re: "Audio" Valves

Reading between many lines, that was my impression - totally commonplace, but it cut no ice with "expert" audiophools who insisted that NOS were very largely ex military.
Thanks.

As for audible differences, it is likely that some amplifier designs are more prone to produce them than others. I have only used one valve amp', so I cannot say, except that my Croft does produce subtle but obviously different sounds depending on what valves are fitted, and my ears are far from young.... 1960's Mullards sound very laid back, (I am trying to avoid the usual word - warm), actually not to my taste at all. Modern Tung-Sol (Russian I believe) are incredibly clear and bright but bass very much takes back seat - stunning vocals though.
I have just bought a calibrated microphone and look forward to seeing what that says, when I have some time.
Dave1000 is offline  
Old 15th Feb 2019, 11:41 pm   #6
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,800
Default Re: "Audio" Valves

The government certainly used to have large stocks of spare valves. They bought them on price from any of a number of suppliers who met any special processing, special testing or sampled quality requirements they had for that type.

Many of these valves went onto the market at various times, I think the last big surge was in the mid 1980s. I bought quite a number at the time. They were in white boxes identifies with what looked like rubber-stamp printing with CV number and pro-electron type number. I don't know whether these were how they had been stored. I suspect they had been kept in bulk-packs and only after being sold to surplus traders did they go into individual boxes. The amount of identification information on the white boxes was too little for the inventory control systems they would have been kept under.

These valves would have been made and taken into stock long before the onset of audiophilia and the interest in the colour of the markings, the smoothness of the anodes. The government wanted working radars, comms radios, PA systems. Above all they wanted reliability and conformance with basic specifications... oh, and a paper trail of provenance.

Valve audio stuff employs in the vast majority of cases very simple circuits, and the characteristics of the individual valves do make a difference to the behaviour of the amplifier etc. What's worse, the effects are combinatorial,, so it depends on the combinations which are present.

People change valves around to achieve adjustments to the sound to suit their taste. Valves are plug-in things and easily changed (too easily?) and tone controls seem to have been excommunicated some time ago. It seems to me to be an expensive and awkward way to go about things, but it brings people pleasure and it's their money and time.

I wonder whether a 'good' amplifier should change the sound at all? I try to design mine so that the output is simply a scaled-up replica of the input. If I want to change the sound, I go for something designed for just that purpose rather than relying on unspecified parameters of devices and their side effects.

You describe the differences as slight, and this fits in with my understanding of the mechanisms involved and with my experiences. I get suspicious of all those articles/webpages where every change creates huuugh differences. Some of the pseudoscience trotted out to try to justify the statements is, frankly, hilarious. They lack any sense of scale, of knowing what size of effect should be created by that mechanism.

So, yes, I hear differences. Usually small ones. Quite often I can't make my mind up which option is right. Maybe they're 'differently wrong'? And very often I'm not sure which version I prefer.

The characteristic shapes of transistors are very different to those of valves, and they do not sound nice. The option of simple circuitry is no longer tolerable, complex circuitry and thorough design is needed to engineer the effects of device characteristics right down to vanishing level. This can also be done to valves, but the results are reviewed as clinical, sterile etc. It seems that there are plenty of people who prefer their music altered from what's on the recording. This is their free right.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline  
Old 16th Feb 2019, 12:32 am   #7
dave walsh
Dekatron
 
Join Date: Jan 2006
Location: Ramsbottom (Nr Bury) Lancs or Bexhill (Nr Hastings) Sussex.
Posts: 5,814
Default Re: "Audio" Valves

Well David that seems to me [as someone who could never design a "tailor made" amp up from the "noise floor" as it were] a very comprehensive and thorough description of all the factors involved in audio appreciation
I understand the desire for technical perfection in many quarters but where is that coming from? Sometimes the best or the very basic sound reproducing equipment can reveal something equally different. Beethoven on a wind-up Gramophone is still Beethoven! That's related to the affect on the listener overall. If it's measured any other way it's accurate but perhaps not so important. If anyone can detect a difference between different valves that's impressive but perfect pitch isn't so common either. The fact that we can listen to recordings at all [now] is the big advantage in my opinion!

Dave W
dave walsh is offline  
Old 16th Feb 2019, 1:07 am   #8
bikerhifinut
Octode
 
Join Date: Nov 2013
Location: Penrith, Cumbria, UK
Posts: 1,993
Default Re: "Audio" Valves

Ok cards on the table.
I am an audio enthusiast, and given my chosen username it's kinda obvious!
I'm with RW David on a lot of points, and I do like my valve power and preamplifiers but am under no misapprehension that what I am enjoying is a particular "colour" to the sound.
However it doesn't stop me from trying to get any home brewed gear working as "right" as I can get it and recent experience with a particular cathode follower circuit seems to back it up. This circuit claims to compensate for the valves changing characteristics as it ages, this is an effect that happens with valves but not as far as I know with transistors.
I got a lot of my inspiration from the series of books on valve amplifiers by Morgan Jones and he goes to great lengths to explain how valve characteristics affect (mainly) distortion. This to me is the "Elephant in the room", what the audiophile seems enthusiastic about is, in fact, the effects of "benevolent" distortion and i assume that means even harmonics.
Hence the enthusiasm for triodes over pentodes, again based on my perception on things.
Anyway in the MJ book, he has a design for a valve RIAA preamplifier and he uses various techniques, including the use of semiconductors to keep the amplifying valve working inside a set of tight parameters so that the correction filtration and frequency response stay constant over the valves useful lifetime and its properties alter.
So back to the OP and his hearing of differences between valves.
I believe this is the reason, and also I am ultra suspicious of much "NOS" stock that seems to be on the market at ever inflating prices. This opens the flood gates to the less than scrupulous and you see knackered mullards on Auction sites going for silly money. Or even more valuable stuff like Telefunkens with the diamond logo on the base which gives them magical properties.
I agree with David that theres a lot of ex military stock out there but don't think they were ever "Specially selected/manufactured". All they had to be was within specification and function in their designed application. Also these valves may not have had the CV (common valve) numbers, sometimes you'll see them with standard "Civvy" numbers. And again it wasn't unheard of for "CV" valves to be sourced from overseas sources, including the "enemy" in eastern Europe. So you may not always be getting what you thought you were.
I've just put away a prototype of a valve driven transformer coupled output preamplifier. This uses a 2 stage ECC82 circuit, nothing at all special and no negative feedback so the valve characteristics will be pretty dominant. I'm not surprised that initial listening seems to suggest that the brand new pair of unbranded chinese jobs from RS are the better set compared to what may be tired mullard ECC82 and GE 5814 (equivalent) and strangely the multimeter suggests this could be the case as the new valves are bang on what they should be and the older ones are all over the place.

Mind you I did commit heresy and listen to it through a nice 1980s Mitsubishi silicon power amp as well as various valve jobs.................... and you know what they all sounded really nice.

A
bikerhifinut is offline  
Old 16th Feb 2019, 7:32 am   #9
ricard
Octode
 
ricard's Avatar
 
Join Date: Mar 2006
Location: Lund, Sweden
Posts: 1,631
Default Re: "Audio" Valves

I'm always intrigued by the fact that the coveted ECC83 / 12AX7 was introduced to the world in 1947, yet is still considered more or less the pinnacle of perfection in terms of audio amplification in some circles. How many other components are based on a 72 year old design are still viewed in the same way?

I'm not really trying to debate whether or not this is indeed valid; as noted above in this thread valve technology leads to simpler circuits, so the technology itself possibly does not need a lot of development past a certain point. It's more that I'm amazed at this "in the 1940s they knew something that we don't so nothing better has come since then" type of thing.

Personally I'm convinced that at least half of what we perceive in terms of audio comes from other sources than our ears. A large portion of the audiophile industry preys on this fact, or rather the fact that their customer base has not (yet) come to that realization. The OP's mention that a large number of valves today would allegedly stem from ex military stocks would seem to add to the mystique of 'high grade ultra specified components', feeding the hype.

Don't want to start a flame war here. When I bought my portable Minidisc recorder in 1999, I was initially very souped up about the artifacts of the MP3-style ATRAC compression used to bring the digital data down to manageble levels, making recordings of CD's and listening hard for potential artifacts (and jumping to compare with the source whenever I noticed the slightest awkwardness in the sound). A short while after I did a double-blind test together with a friend of mine, and the statistics clearly showed that I could not here any difference between the Minidisc and source, and we tried quite a varied selection of musical styles. After that my mind was laid to rest and I never worried about it since. Whether this indicates that my ears were already then past the point of saving is beside the point, really. But I'm drifting off topic here. Valves are great. I can only say that they are cool when they are battery operated though.

Last edited by ricard; 16th Feb 2019 at 7:41 am. Reason: Added last paragraph.
ricard is offline  
Old 16th Feb 2019, 7:45 am   #10
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,637
Default Re: "Audio" Valves

Where are these NOS ECC8*'s? Links? Every big valve toob seller I've come across in recent years have only new Russian or Chinese made valves or when you look up NOS ECC83 you get N/A. Of all the NOS valves I have, I've never seen a ECC83 in it's original box, though I am lucky enough to have a few NOS 81's and 82's in original manufacturers boxes.

Andy.
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline  
Old 16th Feb 2019, 8:42 am   #11
Dave1000
Retired Dormant Member
 
Join Date: Feb 2019
Location: East Midlands, UK.
Posts: 36
Default Re: "Audio" Valves

NOS/NIB ECC8*s are all over eBay. Rather few older Mullards in boxes, unless military grades, it has to be said, but I have bought Valvo, Toshiba, Adzam, Brimar and Raytheon tubes from the late 50's and early 60's NIB within the past year or so, Distributor-labelled NIB valves are also available - I have CVC valves made by Ei in the 1950s, RSD and others are also available.

At the very simplest level, I do not see why valves of, sometimes radically, different mechanical designs should behave identically, and I remain unconvinced that the same design from different factories or vintage sound different - I have Adzam-labelled valves made in Blackburn and Heerlen (spelling) that look and sound identical to me, for instance.

As for reproducing EXACTLY what is (intended to be) on any CD or record - for that you'd need EXACTLY the system used to master what was embedded in the disc.

P.S. - David - many thanks for the thoughts from one who has experimented as a designer/builder and "audiophool"
Dave1000 is offline  
Old 16th Feb 2019, 8:54 am   #12
Dave1000
Retired Dormant Member
 
Join Date: Feb 2019
Location: East Midlands, UK.
Posts: 36
Default Re: "Audio" Valves

Apologies for a string of replies, but as a newbie I do not have edit facility.
The differences are, in my amp', not what you would get from tone controls. Getting into the unexplainable now, but how the music appears, how it is presented, how instruments appear relative to one another is what is altered.

The microphone will POSSIBLY answer a query or two, but at the moment I unconvinced that the tonal balance is altered much, if at all.
Dave1000 is offline  
Old 16th Feb 2019, 9:17 am   #13
Craig Sawyers
Dekatron
 
Craig Sawyers's Avatar
 
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
Default Re: "Audio" Valves

Mullard in 1962 published two papers on microphony in valves

https://www.thevalvepage.com/valvete...ophony_pt1.pdf
https://www.thevalvepage.com/valvete...ophony_pt2.pdf

Craig
Craig Sawyers is offline  
Old 16th Feb 2019, 9:44 am   #14
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,800
Default Re: "Audio" Valves

Back in the day, the valve manufacturers were in it for the MONEY. The BVA had been as nasty a monopoly as any. We've had ripoff record pricing and Microsoft's era of monopolistic shenanigans and hated them for it. WWII and the arrival of lots of American toobs scuppered the BVA and it couldn't have happened to nicer people.

Post-WWII there was a much more open market and the valve firms were having to compete, with each other and with other countries. They employed good scientists and engineers in both developing new products and improving existing ones. Their holy grail was getting design-in in big-selling consumer goods. To do this they had to be able to show advantages to radio and TV designers, the valve firms were also the technology leaders, putting out applications notes and books to show set designers how to use new devices. Think of those Mullard and GEC published amplifier designs, Mullard's articles on TV circuit design, Philips Technical Review continued into the 1980s. A big step for the valve firms was something like a wider angle, shorter TV tube and new deflection circuit bottles to handle its scanning and EHT requirements or lower noise triodes for UHF tuners.

Granularity, authority and soundstaging hadn't yet been invented. There were plenty of people around with good hearing. More people back then were exposed to a greater proportion of live, unamplified, music. Not everyone worked in a dark satanic noisy mill. Deep Purple hadn't yet given us rock concerts turned up to twelve. They knew what good sound was... mostly, I remember the scattered pitches of our school orchestra (shudder!) as enthusiasm tried to make up for accuracy.

Also, back then, valves were seen as wearing items. You got a year's warranty on that radiogram or telly, but only 90 days on the valves. The set makers told their customers that valves were crap. Valve makers worked on reliability. They had an incentive to not make things too long-lived, but they were under an awful lot of pressure to get infant mortality rates down. What they did to achieve this also improved the long term as a side effect.

The Mullard factory at Blackburn was the biggest on the go, and with their turnover they had the money and the statistical data to fine-tune their product and their production processes. We now know that the life expectancy of valves is a lot better than was thought at the time, though we seem to have forgotten the rates of them dying young through some manufacturing defect. Statistical quality control really got going in this area.

With valves the only game in town, they had to be used in submarine telephone cable repeater amplifiers. To say this is an incentive for high reliability device development is an understatement. ST and C worked in this field. They hadn't got Mullard's information flow from bulk turnover, but they did have the resources to do much deeper testing (sorry!) on their smaller numbers. Western Electric and Bell Labs were active here as well.

So, back in the day, there was a lot going on. People were just as bright then, maybe fewer were dulled by staring at phones all their waking hours. People weren't cloth eared. The big jobs for the valve makers were getting design-in and upping reliability.

Governments wanted valves. Reliable valves for the cold war. Valves that could sit in stores until 'It' happened, and then could be trusted to save those who'd survived the first onslaught. Easy to write about now, but it was deadly serious then. They wanted Geiger counters, planes, missiles, manpack radios, crypto gear and it all had to work when needed.

Standard consumer bottles were very good on reliability, and were fine for a lot of military uses. Some CV numbers meant that the parts were just like commercial ones but had been tested on a higher sampling rate, or some added tests. It's unlikely that these processes affected the sound of the valve other than psychosomatically. Other military valves might have structural changes to enhance their durability under vibration. Extra micas, spot welds, braces and things like that. Do these make a difference to the sound? Some might, but is the difference good or bad? Some were screened to tighter specs. Some even had looser specs to encompass a wider environmental range.

Are mil-spec devices better than civvy devices? Well, they most probably are for military activities. For civilian activities, your mileage will certainly vary. Mil-spec binoculars might be your preference out birding in the rain. Toughened valves can be worse for microphony. Have you ever tried doing your suopermarket run in a Ferret scout car? But remember recent debacles about standard issue army boots coming apart and soldiers buying better civvy ones from hikers' shops?

If you get offered an ex-military valve, you can rely on it being better controlled in quality in terms of reliability, but that's about it.

It's the thought that counts

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline  
Old 16th Feb 2019, 10:01 am   #15
Craig Sawyers
Dekatron
 
Craig Sawyers's Avatar
 
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
Default Re: "Audio" Valves

Agreed to all of that. Tektronix did their own 100% screening of valves, with massive burn-in racks to (a) eliminate infant mortality and rapidly changing characteristics and (b) allow their characteristics to stabilise. They then allocated a Tektronix part number, stuck a label on the valve, and boxed it with The Tek part number on that too.

Test conditions for all the valves they used are here http://w140.com/tekwiki/images/1/14/..._procedure.pdf

And the racks they used are here
http://w140.com/tekwiki/images/0/0a/Tek_tube_aging.pdf

Craig
Craig Sawyers is offline  
Old 16th Feb 2019, 10:22 am   #16
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
Default Re: "Audio" Valves

The ECC82 is a B9A version of the older octal based 6SN7. A totally reliable work horse that will function in practically any small signal triode circuit. It was extensively employed in television receivers from around 1952.

The ECC83 was designed as an 'audio' valve primarily as a second stage amplifier or driver stage for a push pull output circuit, often driving a pair of EL84 valves.

Again a very simple incredibly reliable double triode manufactured in millions to a high consistency. I doubt if there is much if anything to choose between examples from the quality manufacturers.

The ECC81 hides in the background. Often employed as a mixer/oscillator in BBC only television receivers just prior to the introduction of Band 3 in 1955.

I have never encounted microphonic ECC82/3 valves but have had the odd problem with the EF86 operating under starvation current conditions. Once a good example has been selected, no further problems should arise.
Regards, John.
Heatercathodeshort is offline  
Old 16th Feb 2019, 10:42 am   #17
woodchips
Octode
 
Join Date: May 2010
Location: Grantham, Lincolnshire, UK.
Posts: 1,172
Default Re: "Audio" Valves

I will put my cards on the table now.

Since the late 90's I have attended and bought piles and piles of stuff from the ex-military sales, and not once have I come across these fabled boxes of spare valves. Even when Stafford closed 15 (?) years ago there was nothing.

Why is this important?

When communism collapsed the military on the continent, BAOR, was essentially redundant. All the stuff on the military bases, mainly Germany, was sold off in auctions and I have heard stories of a tank going for £100 or similar silly amounts. The government rightly concluded that this wasn't acceptable and changed the way all government surplus was sold on. This was the mid-90's.

This involved companies such as Anchor, MVS, Ramco, Withams etc. You may remember all the series Land Rovers being sold by MVS in the 00's, Fradley was it? There were hundreds of them.

It is these companies I have bought from.

Secondly, just what valve based equipment was still being used by the armed forces in the 80's that would come up for sale in the 90's? None. If these boxes and boxes of valves were around then they, by definition, would have come from high volume use, typically the army. The RAF and navy never possessed enough assets that required more than, say, 200 of one thing. And when did army comms equipment change to transistor? I am no expert but Clansman died decades ago, what about Ptarmigan? What was before that? In any case this stuff had a life time of 20 years and by the 60's transistors were in, they were lighter and smaller.

The exception to this, in my experience, is test gear. When Stafford closed it seemed that every RAF station had at least one of everything to test any aircraft that could possibly arrive. I know, I bought stillages of it. This was almost always partially valve based, with ECC83's being quite common. I bought a pile of some test sets in the early 00's that had ECC83's in them. I was offered £3 each for these, which I accepted thinking it was a good price, something like 50 of them from memory. At that time I didn't see them as valuable to keep.

It must be mid 00's at another sale there was a huge pile of stuff from, probably a deceased persons shed, that I bought. In it were a couple of hundred valves including boxed KT66's, EL34's plus lots of others. The interesting thing is that I saw these as just something to increase the bid price a little, what I was after was an engineer's microscope plus lots of other interesting little odds and ends. It filled the trailer up. From memory I paid about £300. Again, I didn't see valves as a source of lots of money, but more interestingly neither did anyone else at the auction.

So, from my first hand experience of buying ex-military stuff, basically anything that could be turned into money, valves have been notable by their absence. And as I have said, no one else could have bought these valves other than through the appointed disposal agents. There was always a good crown at the viewing, remember Anchor at Coalville in the late 90's, early 00's? Bought about 300 theodolites from them!

I have long thought that the description NOS needs to be challenged in court because it is simply impossible to guarantee. Even my KT66's, in nice white GEC boxes, aren't NOS, I can't guarantee that. About the only valves for which NOS is possibly accurate are the millions of ex-TV valves, no one wants them, so no fraud. But, as has been said here many times, the old valve was put back in the box when replaced, so even that might not be true.
woodchips is offline  
Old 16th Feb 2019, 10:48 am   #18
cathoderay57
Nonode
 
Join Date: Oct 2017
Location: Bristol, UK.
Posts: 2,364
Default Re: "Audio" Valves

No wish to be insulting but I take it Dave1000 that you are not swapping an ECC83 for an ECC82 or vice versa? If you are then it is highly likely that there would be an audible difference because the characteristics notably the grid biasing are considerably different. Cheers, Jerry
cathoderay57 is offline  
Old 16th Feb 2019, 10:48 am   #19
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
Default Re: "Audio" Valves

As John says, the ECC82/3s were workhorse valves used in a vast range of consumer, industrial and military equipment. There were very large stocks of them globally at the end of the valve era. Some NOS brands are now in short supply and expensive because various people have decided they sound better and buy any they come across - valve hifi people are only one of the factors here, as these are very widely used in guitar amps, and guitarists love to swap out their Chinese ECC83s and replace them with NOS Mullards.

British military valve stocks were largely sold off to dealers in the 1980s after the last valved military equipment was retired in the 70s, though as has been said some lightly used test gear did soldier on for longer so some stocks may have been retained for this.
paulsherwin is online now  
Old 16th Feb 2019, 11:00 am   #20
Dave1000
Retired Dormant Member
 
Join Date: Feb 2019
Location: East Midlands, UK.
Posts: 36
Default Re: "Audio" Valves

All very interesting - thanks.

I am unsure how many people regard mil spec' valves as being "better" in any sense, different perhaps more than better.

Having seen quite a few mil spec's over the years (none for valves), I know all too well that it means no one thing in particular. Some spec' details you look at and see that they are nonsense for one reason or another, others leave you puzzled when you think that it would be difficult to manufacture something that badly outside of a normal spec'.
Dave1000 is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 9:05 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.