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Is it necessary to...............

icehockeyboy

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Use matched pairs of valves? As a valve virgin i assume its so as to ensure both channels sound identical, or have i got it all wrong.

Obviously i am talking about kit that only uses 2 valves.

 

enjoy_the_music

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Well you want valves that measure the same don't you? From my viewpoint if they're not measuring correctly you could get different performance in each channel.

I had this with a dual mono shindo preamp..it had two volume control knobs, one for each channel...you could tell one of the tubes in one side was on it's way out as it required 'more volume'...replaced them with a matched pair everything was cookie.

 

Davewhityetagain

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icehockeyboy wrote:

Use matched pairs of valves? As a valve virgin i assume its so as to ensure both channels sound identical, or have i got it all wrong. Obviously i am talking about kit that only uses 2 valves.
its good practice to use match valves, but if you haves biased your amp correctly I doubt that with some amps it would make much differance

 

Kev

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Depends on the circuit and valves. I have a pre that uses 2 valves, but they are dual triodes and each valve runs the 2 channels, one channel on each half of the triode. So in that case it'snot an issue.

Kev

 

Tel

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My pre amp uses four valves, the advice I had was buy all new at the same time and just bung em in.

My power Amp is a bit different, four 6550C in that one, normally a good idea to use matched valves , but the Conrad Johnson has a manual bias arrangement which is easy to use.

Other Amps auto bias.

I understand that some of the Chinese Amps (AVC)need to be changed by someone who knows what they are doing.

 

mrwippy

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Kev wrote:

Depends on the circuit and valves. I have a pre that uses 2 valves, but they are dual triodes and each valve runs the 2 channels, one channel on each half of the triode. So in that case it'snot an issue.Kev
In many cases the 'matching' will be suspect anyway, unless they are matched to perform within the parameters of the circuit they are intended to be used for. I've tried both matched(?) and unmatched pairs of the same tubes and not heard any difference whatsoever. Certainly I've never found it an issue with small signal tubes, and I wouldn't buy an amp that specified you needed matched tubes on principle. But with all these things follow the manufacturers guidance in the first instance. In the above case it's more beneficial to have both sides of the individualvalve matched.

Oh, you might want to question what the seller is matching anyway, after all this can mean as little as they have visually matched them for their structure - yes this does get done and called 'matching'.

I have a pair of really unmatched 12AU7's (one over 100%, the other on its last legs - or should that be pins)but they actually perform fine. Now, minimal grid leakage (but well in spec and never usually checked)on one of the tubes in my phono stage and its a different story. Plays havoc with the output, but the tubes can be well matched electrically.

 

Tel

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:sw:

I love valve threads!

No matter how straight forward the question in the OP, you just know there will be nothing straight forward in the replies!
biggrin.png


 

mrwippy

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Tel wrote:

:sw:I love valve threads!

No matter how straight forward the question in the OP, you just know there will be nothing straight forward in the replies!
biggrin.png
But just soooooooooo much more fun than cable debates.
wink.png


I wonder what interested parties would have made of this type of question in back when valves were the only option.

Valves would have been made to meet a specific specification and a circuit would have been designed to work with a specific valve - plug in and go. If something different was required, a new valve would have been developed to meet the need and - plug in and go. Obviously stereo would have forced a change of pace, but then again most high end (?) manufacturers of the day would have told you to buy two mono units. I'm not an aficionado of vintage kit, but does the likes of Leak Stereo 20 manual get you to use matched valves - or is it plug in and go?

Of course we are so much more technically advanced and aware these days and don't get taken in by marketing hype and snake oil products and of course all those Prima Luna owners went on to buy matched quads of EAT KT88's at £599 for their £999 amp because the distributor recommends them and they got great reviews.:raoflmfao:

Craig, if you'd like to give it a try, I'll measure up some ECC88's, put together a poorly matched(?) pair for you to try out and see if it makes a difference.

 

jonjin

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Jul 22, 2005
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Good thread... I had a similar thought in my head. Still somehow knowing that the valves are wildly out of matching makes me psychologically more worried.
shock.gif.7732780fe7e208b945ce79ca96402fca.gif


JJ

 

mrwippy

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jonjin wrote:

Good thread... I had a similar thought in my head. Still somehow knowing that the valves are wildly out of matching makes me psychologically more worried.
shock.gif.7732780fe7e208b945ce79ca96402fca.gif
JJ
Obviously, it does make sense to have matched tubes if possibleand if there is no cost or a minimal premium then why not. I just question the absolute need in many instances. Also, how long do valves stay matched? I suspect that few if any wear at the same rate, but of course if they start out at the same 'standard' then maybe that should help.

A while back I ordered of 8 new production ECC83, 3 from one UK supplier and paid a premium for a pair to be matched (but all were tested prior to dispatch)and got 5 others of the same make, but random selected white boxed and unprinted, shipped over from the US at half the cost (inc shipping) of the the 3 UK ones. Absolutely no audible performance difference between any of these tubes that I could hear.

Also bought a batch of 6, 13D5's from a very reputable UK dealer a few years back, all tested prior to dispatch - now I test all my valves prior to use and failed 4 of the 6. Had a discussion with the suppliers tech'y about my testing, they never answered how they test, anyway 6 more were sent out and this time only 1 was bad, so I got my 6 in the end, trouble was this was a preliminary trial to see if was going to order a batch of 30 for myself and 4 other members of the "13D5 appreciation society" - didn't bother in the end as I felt it was too much effort.

As you may gather I'm rather sceptical about sellers matching and testing claims and take it all with a pinch of salt.

 

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