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I have GE 12BZ7s in my six pacs..is there a better version of this tube than GE? Where can I purchase? Thanks
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Regarding the use of AC vs DC for indirectly heated tubes, bear in mind that DC heating provides constant temperature based on constant voltage. With AC heating the *average* amount of heating is the same, for sure, but the *peak* heating power is twice the average. You can think of there being small 120Hz "waves" of heat, on top of a constant flow of heat, flowing from the heater wire through the insulator to the cathode sleeve and thence to the coating. These will be small, to be sure, based on the thermal inertia of the heater wire, insulation and cathode sleeve, but the peaks of these waves will result in some small increase in the space charge around the cathode. This may explain why some folks notice an increase in "drive" from AC heating, since the increased space charge would result in a higher Gm and make the tube sound "newer" (in the sense of age, not date of manufacture).
and did find the Telefunken smooth plate an interesting listen. Mine are totally reworked though. All tantalum resistors, NOS, upgraded caps and I don't use the onboard power supply caps but an array of off board poly and oil caps. I also converted it to balanced input and all wiring is high purity dead soft silver. I also changed the driver tubes over to regulated heaters vs to ac. It is quieter that way but sometimes you get better dynamics with AC heaters.
The Elaborate DAC=Johnny's Balloon Meshplate 27 Balanced Preamp=Balanced Six Pacs=Newform Research 645
iRiver H140/MB Balanced dac/amp/Ultrasone Ed. 9/JH13 Pro IEM's
see images at: www.pbase.com/jamato8
Edits: 06/11/12
"I also changed the driver tubes over to regulated heaters vs to ac. It is quieter that way but sometimes you get better dynamics with AC heaters."
I am looking at the owners manual for the Cary Audio Six Pac amplifier.
It shows that all the tubes are in-directly heated (meaning that the heater supply is not part of the signal path).
Can you explain how the amplifier can have better (or worse) dynamics depending on how you heat the heaters (as long as they are heated to the correct temp and not adding noise to the audio path)?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
disperses the electrons. I don't know for sure but I have read it often that AC heaters produce better dynamics. I spoke to Dennis once and he felt this, which is why the Six Pac had/has the AC heaters. You could ask Cary I would think.
The Elaborate DAC=Johnny's Balloon Meshplate 27 Balanced Preamp=Balanced Six Pacs=Newform Research 645
iRiver H140/MB Balanced dac/amp/Ultrasone Ed. 9/JH13 Pro IEM's
see images at: www.pbase.com/jamato8
6.3 volts AC RMS is another way to say how much AC voltage is required to get the same amount of heat into the cathode as you would with 6.3 volts DC.RMS, as a way of measuring AC, was invented for that very reason.
A cathode will be heated to the same temp. using 6.3 volts AC RMS as it would for 6.3 volts DC. (BTW, 6.3 volts AC is 17.766 volts peak to peak)
With direct heated tubes (45, 2a3, 300b, etc.) the heater (filament) supply can be part of the signal path and there is good reason to think that the sound might be different between AC and DC heating.
This is where the idea that AC vs. DC makes a difference comes from, but not with in-direct heated tubes.
In-direct heated tubes have no way of telling the difference between AC and DC heating.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 06/11/12 06/11/12
as this is what Dennis mentioned to me as have a few other. I read what you wrote but thee still seems to be a difference of opinion.
The Elaborate DAC=Johnny's Balloon Meshplate 27 Balanced Preamp=Balanced Six Pacs=Newform Research 645
iRiver H140/MB Balanced dac/amp/Ultrasone Ed. 9/JH13 Pro IEM's
see images at: www.pbase.com/jamato8
I gave no opinions. Only facts.
You have been given mis-information.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
that the filament remains more constant with AC. It has been postulated that with DC there is metal migration.
The Elaborate DAC=Johnny's Balloon Meshplate 27 Balanced Preamp=Balanced Six Pacs=Newform Research 645
iRiver H140/MB Balanced dac/amp/Ultrasone Ed. 9/JH13 Pro IEM's
see images at: www.pbase.com/jamato8
I have the found that the telefunken smooth and Ribbed plated 12ax7s work well and the GE or RCA 6072 black plates in those amps...I have also found the 5751 Raytheon windmill to work well in the six pack amps.I haven't found a big difference in 12bz7s, other than maybe a black plate if you can find them.I have a pair of a pair of CBS branded black plate 12bz7s,and I have not found them to be a step up from the gray plates.
When problems become increasingly difficult,we can always rely on our collective knowledge and seek relief.
Edits: 06/11/12
Michael,
Thanks for your help...my six pacs has the stock GE 12BZ7 tube I assume this is not the NOS GE 12BZ& tube some people have recommended? Do you know if the 12BZ7s at upscale audio are NOS or new production?
What Jim said.
Anyway,did you try some 12ax7s or 5751s or 12ay7s or 6072s in the amp? I think you will be mighty surprised and find it to your liking.
When problems become increasingly difficult,we can always rely on our collective knowledge and seek relief.
There are no 12BZ7s in production anymore. ALL 12BZ7s are old stock.
Tung Sol 12BZ7s are nice if you can find them. Try Radio Electric Supply.
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