[guest1632]

Hi Frank,

Just curious why you are using 12AT7 versus a 12AU7? Also, why not 5751 or the 5814 tubes? The latter from what I read fairly consistently are better sounding tubes.

Ray

[avahifi]

Actually we are using 6N1P tubes in the line stages of our hybrid and tube preamps and DACs now.

The 5751 is essentially a ruggedized version of the 12AX7 and typically has lower gain and thus is not as good a choice in a phono circuit where you need all the open loop gain you can get to close the RIAA equalized feedback loop.

Long ago, before the resurgence of good quality 12AX7 tubes again, we had access to a good supply of new old stock 5751 tubes that were better performing than most then available new 12AX7 tubes and we used them for a while.

In the line section, we want a high current tube and there the 6N1P is hands down better than the others you mentioned.

Regards,

Frank Van Alstine

[guest1632]

Actually we are using 6N1P tubes in the line stages of our hybrid and tube preamps and DACs now.

The  5751 is essentially a ruggedized version of the 12AX7 and typically has lower gain and thus is not as good a choice in a phono circuit where you need all the open loop gain you can get to close the RIAA equalized feedback loop.

Long ago, before the resurgence of good quality 12AX7 tubes again, we had access to a good supply of new old stock 5751 tubes that were better performing than most then available new 12AX7 tubes and we used them for a while.

In the line section, we want a high current tube and there the 6N1P is hands down better than the others you mentioned.

Regards,

Frank Van Alstine

Hi Frank,

So how does this apply to your Fet Valve power amps? Are you also using the 6n1p there too?

Ray

[avahifi]

We are using 12AT7 (ECC81) tubes in the Fet Valve amplifiers.

We have tested 6N1P tubes in this application, but at this time it does not appear to be cost effective to change over to them.  It would require a different power supply board, much revised audio boards, and even a different power transformer winding to make a complete changeover.  There are small sonic benefits, but not in the same ballpark as with our new differential systems.

With a complete differential system, the amplifiers seem not to make as much difference as before.   I have an OmegaStar differential amplifier up and running now, and nobody would ever guess it has any solid state components in it at all.  Just pure and utterly transparent.

Regards,

Frank Van Alstine

[guest1632]

We are using 12AT7 (ECC81) tubes in the Fet Valve amplifiers.

We have tested 6N1P tubes in this application, but at this time it does not appear to be cost effective to change over to them.  It would require a different power supply board, much revised audio boards, and even a different power transformer winding to make a complete changeover.  There are small sonic benefits, but not in the same ballpark as with our new differential systems.

With a complete differential system, the amplifiers seem not to make as much difference as before.   I have an OmegaStar differential amplifier up and running now, and nobody would ever guess it has any solid state components in it at all.  Just pure and utterly transparent.

Regards,

Frank Van Alstine

Hi Frank,

Wow! so you are saying then that there isn't as much difference now between your Fet Valve amps, versus the OmegaStar amps? Is this new differential system also in the FetValve amps too? Is this same system able to be applied to your preamps as well?

Ray Bronk

[avahifi]

Ray, take a look at the thread just below this one, AudioKarma Audio Festival.  Many of the questions you have asked are answered there.

A pair of Ultra hybrid amplifiers run as differential pairs still have an advantage over the solid state differential amplifier, but both raise the bar a whole lot.

Lets put it this way, I would rather listen to our complete new solid state differential system than a stereo two channel Ultra hybrid system.

And yes, the differential mode is done from the output of the DAC chip all the way to the speakers (requiring four separate channels of filtering and amplification all the way).

Tube aging effects?  We have two separate Ultra differential DACs and Ultra differential preamps up and running for some time now.  Obviously that is a lot of 6N1P tubes (16 of them) and of course they are not perfectly identical new out of the box and we have made no attempt at careful matching except to reject obviously poor performing ones.  We hear no differences between the units so suspect that normal tube aging won't be a significant issue.  I can't tell you just why at this time.

Regards,

Frank Van Alstine