Matched pairs?

Drikus

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Got a pair of NOS RCA Electron 805 tubes but they aren't matched. Didn't find a matched pair anywhere. Will there be a sound degradation using an unmatched pair?

UZ6SCgA.jpg
 

microstrip

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Got a pair of NOS RCA Electron 805 tubes but they aren't matched. Didn't find a matched pair anywhere. Will there be a sound degradation using an unmatched pair?

View attachment 43793

You have to check the gain of the amplifier. Your amplifier has no feedback, gain will depend on the trans-conductance of the tube - typically you risk up to 2dB variation using non matched tubes.

You can do it easily with a cheap multimeter and a test track or even an online generator - it can be easily sourced from many sites.
 

Drikus

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I have no idea how to do these measurements. Stupid question and I think I know the answer already but is a 2dB difference audible?
 

microstrip

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I have no idea how to do these measurements. Stupid question and I think I know the answer already but is a 2dB difference audible?

Surely it is audible. The measurements are very simple to carry. Can you listen to online tracks in your system?
 

microstrip

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Thought so. Yes I can, my MacBook Air is connected to my system.

So, all you have is going to the Wave Corrector site http://www.wavecor.co.uk/testdisk.html and play the adequate tracks in your system while measuring the output of the amplifier. Be careful some of these signals can damage your speakers!

I would use track 33 - 100 Hz at -30dB. Although I usually carry tests at 1000 Hz, but as some cheap meters intended to measure mains voltage are inaccurate over 200 Hz I recommend 100 Hz in doubt. I would carry this measurement with an amplitude around 1.5V AC (RMS) - enough to have a good resolution and not enough to disturb anyone. But you can also carry it with the speakers disconnected. What matters is how close the values of left and right channel are.

BTW, we can download the whole compilation for autonomous use - see the bottom zone.
 

Drikus

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So, all you have is going to the Wave Corrector site http://www.wavecor.co.uk/testdisk.html and play the adequate tracks in your system while measuring the output of the amplifier. Be careful some of these signals can damage your speakers!

I would use track 33 - 100 Hz at -30dB. Although I usually carry tests at 1000 Hz, but as some cheap meters intended to measure mains voltage are inaccurate over 200 Hz I recommend 100 Hz in doubt. I would carry this measurement with an amplitude around 1.5V AC (RMS) - enough to have a good resolution and not enough to disturb anyone. But you can also carry it with the speakers disconnected. What matters is how close the values of left and right channel are.

BTW, we can download the whole compilation for autonomous use - see the bottom zone.

Thanks for trying to help but isn't all this work pointless? I mean I'm not going to use the tubes anyway if you say the difference is audible in unmatched pairs. Also got a new factory matched pair of 805-T/2 Psvane's, wouldn't it be better to use those instead and sell the RCA's?

iway0NI.jpg
 

microstrip

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Thanks for trying to help but isn't all this work pointless? I mean I'm not going to use the tubes anyway if you say the difference is audible in unmatched pairs. Also got a new factory matched pair of 805-T/2 Psvane's, wouldn't it be better to use those instead and sell the RCA's?

View attachment 43797

Not without trying first IMHO - it is very simple to do and perhaps they are close enough or even well matched by chance. Remember that preceding tubes in the amplifier (input and driver) can also have small imbalances and some times swapping tubes between channels allows us too get an excellent result in the end.
 

Drikus

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OK, it's worth giving it a try if you put it like that but I need to get a multimeter first, which one do you recommend?
 

microstrip

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OK, it's worth giving it a try if you put it like that but I need to get a multimeter first, which one do you recommend?

Audiophiles should get a Fluke - it increases our status. :) Can I suggest a Fluke 113? You can get it at Amazon.de.

Although you can get any cheaper multimeter, Fluke's will stay accurate for a long time, something that does not happen to the cheap ones. Recently I have seen that my almost 40 years old Fluke 77 (old version, not the current one) is still measuring accurately!

BTW, Vladimir Lamm states clearly in his manuals that we should use a Fluke multimeter to bias his amplifiers!
 

Ron Resnick

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Can a fluke be reliable? :confused:
 
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Empirical Audio

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I used the PSvane 805A-T (no top anode) for several years in my monoblocks, but they kept dying. I eventually changed to the ShuGuang Nature series. This is an amazing sounding tube. Highly recommended. I changed the filament circuit in my amps by adding an inrush limiter and now the filaments come up slowly. Tubes never die prematurely anymore. Extremely fast and phenomenal bass.

Unfortunately, only the 805A is available from ShuGuang. The 805 must be PSvane.

I think the design of the amplifier drives the requirement for matched tubes. Some will require it.

Steve N.
Empirical Audio
 

microstrip

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A Fluke 113 is on it's audiophile way! :cool: Will be delivered tomorrow.

Great - but now in order to use your 113 to calibrate your system you should add a few inexpensive accessories :


https://www.amazon.de/BestPlug-Verb...1537485141&sr=8-15&keywords=cinch+adapter+bnc

https://www.amazon.de/SIENOC-BNC-St...F8&qid=1537485184&sr=1-6&keywords=adapter+bnc

https://www.amazon.de/MagiDeal-Mult...77&sr=1-2-fkmr2&keywords=Magideal++cable+4+mm

One black and one red cable, preferably!

Using these parts you will easily measure the output voltage of cinch outputs and will be able to calibrate your system. After you got them I promise I will start a thread on it!
 

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Drikus

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Cool, will be ordering these accessories today. I've installed the RCA's yesterday and they're a huge improvement over the stock Chinese Electron 805 tubes already, I'll do the measurements because I'm curious too but they will stay in place whatever the outcome is.
 

Drikus

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Sep 28, 2012
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Ordered the accessories but the delivery time for the cables can take up to one month it says because they are not sold by amazon themselves so no prime delivery available.
 

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