different volume between KT88s

[sumotan]

Hi Guys
I was swapping my older GL KT88 to much newer Psvane KT88 tii suddenly I noticed that the Psvane is less loud playing the same music at the same volume.
So I thought could it be different bias requirement that's causing this but then again my Primaluna Dialogue 7 has this so call auto bias circuit that's suppose to automatically adjust bias to get best performance. What's your thoughts Gents ?


Thks

 

[JonSnell Electronic]

The KT88s have got different parameters. That is natural, especially with copied valves from China.

 

[Osvaldo de Banfield]

New tubes surely differ in their transconductance, a manner in which gain can be measured. And there may be a discrepancy of transconductance even at the same current.

 

[DF96]

Different valves will have different optimum bias, different gain.

Not everything labelled 'KT88' is actually a real KT88, but could be some rough approximation.

Extra distortion makes things sound louder.

If you have a good circuit (e.g. well-chosen bias point, adequate feedback) and good valves then you are very unlikely to hear any difference.

 

[sumotan]

Thanks guys. Given the higher price of Psvane Tii over GL KT88, I was not expecting this.
Aside for this issue, the Psvane do sound very very good though.

Thanks again

 

[DF96]

It would be very naive for someone to think that in audio you get what you pay for. About the only component where this might be usually true is transformers.

 

[sumotan]

Wrong DF96 since KT88's is already an old & established tube, Im naive in thinking that it would be as good if not better even in reproduced form with the help of modern technology.

Cheers

 

[Kay Pirinha]

Are you sure that all that PSVane (or any other company) tells you about their products is plain truth? Can you exclude any marketing blahblah?
Best regards!

 

[sumotan]

You referring to my comment Kay ?
It it is true in context on my system it does sound very good.
GL sounds more hifi, Psvane more even handed. I guess its also system & room dependent as well.

Cheers

 

[DF96]

In general modern valves are likely to be worse than NOS valves; at best they are similar in performance, lifetime etc. 'Modern technology' does not have access to the skills from the past (almost all of the people have now died), and does not have the supply chain of appropriate materials which existed back then.

 

[sumotan]

True too Df96 but the cost of NOS tubes are so prohibitively high its rather scary & given their age who knows if they would perform or last as it should.

Cheers

 

[DF96]

Perhaps that is a good reason for not choosing KT88 nowadays. Genuine KT88 are very expensive, and modern copies are not as good.

 

[Mark Tillotson]

Wrong DF96 since KT88's is already an old & established tube, Im naive in thinking that it would be as good if not better even in reproduced form with the help of modern technology.

Cheers

Unfortunately electrons in a space charge know nothing of "modern technology", they just behave according to basic physics and the geometry of the electrodes.
There's not much you can do to tweak the performance of a vacuum!

 

[DF96]

But you can do a lot to tweak the performance and life of a cathode. It seems that cathodes were very much a matter of trade secrets, which may partly be why Mullard had such a good reputation. Also, modern valves are often not evacuated to as low a pressure as in the past - not because the technology is lacking but because it takes time and so costs money.

 

[sumotan]

Well like it or not we're now stuck with either Russian or Chinese tubes.
Any tubes that's popular in NOS form will cost an arm & a leg.

 

[petertub]

Well like it or not we're now stuck with either Russian or Chinese tubes.
Any tubes that's popular in NOS form will cost an arm & a leg.

don't forget slovakia JJ as tube maker, it's a modern plant and it's operating
in EU.

 

[sumotan]

Aaah forgot about that thks for the heads up Peter.
Modern tubes aren't really cheap either if like my amp needing 4 power tubes per channel.
Sigh, looks like I better go low power instead. Lol

 

[kodabmx]

Well like it or not we're now stuck with either Russian or Chinese tubes.
Any tubes that's popular in NOS form will cost an arm & a leg.

That's why i design with NOS Soviet tubes instead of Western ones...

 

[sumotan]

Off topic Kodabmx, are Svetlana Sv 811-3 worth collecting ?

Thks

 

[kodabmx]

I couldn't really tell you about the 811* as I have never used transmitting tubes, but Svetlana (Winged C) are quite well made tubes in my experience.