[OctavianH]

I can say with certainty that EL34 metal base, GEC KT66, 88 and EL12spez together with Tung Sol 6550 sound great with Ultimate.

Yes, I was not necessarily refer to UltimatE and it makes sense to clarify that, I was speaking in general, as "theory". I know that some of us who could do that (not me) tried the same tube at 250V/300V/350V plate and found some "sweet spots" for specific tubes at a specific operating point. At that point a tube was sounding optimal or better with another specific tube. That I was wanting to say, that not all tubes are optimally biased on my amp. I do hope one day I will have an amplifier who will allow me search for such sweet spots and listen with my own ears. At the moment I just read what others have tried. Of course, many work fine, many sound spectacular, some "meh" tubes are in fact not "meh" but I cannot obtain a sweet spot for them on my amp.

As I said, in theory. Not blaming any amplifier, nor mine. Just saying that this is how I see it.

 

[g0ldl10n]

This is true. Not only plate current, but also plate voltage, is important to obtain the best from your output tubes. This is the reason I avoid recently to use tubes with very high ratings, which are considered as "normal" operation much above what my amp is keeping them (200Vp/20mA). In my view the tubes which sound the best are those with max ratings around 250-300V plate. Most probably those are the ones I use efficiently. Of course, there are exceptions, but my next amp will have for sure variable Vplate.

Last night I was able to get the plate current stable at 65mA with 6AS7 plates paralleled.. unfortunately, still had unwanted distortion with higher volumes, so these likely a no go. It isn't all bad news though - I learned a few things along the way.

 

[mordy]

Last night I was able to get the plate current stable at 65mA with 6AS7 plates paralleled.. unfortunately, still had unwanted distortion with higher volumes, so these likely a no go. It isn't all bad news though - I learned a few things along the way.

I would not be surprised if you found a way to avoid that unwanted distortion- what does Eric say?

 

[g0ldl10n]

I would not be surprised if you found a way to avoid that unwanted distortion- what does Eric say?

Well, provided him my results + a few live measurements with the tubes in place and negative bias switch and he thanked me for testing it out on my end, but said he couldn't comment/advise much until he does his own investigation/testing on his end - which may or may not happen, lol.

 

[g0ldl10n]

Here is another input that shine in the Ultimate paired with the right output.
Mazda 30L17 and 30L15 (thanks to @TLO for finding these) twin triodes. Currently, the 30L17 is driving a pair of 6AH4GT triode sweep tubes.

 

[triod750]

Here is another input that shine in the Ultimate paired with the right output.
Mazda 30L17 and 30L15 (thanks to @TLO for finding these) twin triodes. Currently, the 30L17 is driving a pair of 6AH4GT triode sweep tubes.

Oh, the horror!!

 

[Dogmatrix]

Last night I was able to get the plate current stable at 65mA with 6AS7 plates paralleled.. unfortunately, still had unwanted distortion with higher volumes, so these likely a no go. It isn't all bad news though - I learned a few things along the way.

It would have been good to expand the already absurd flexibility of Ultimate
Eric builds an excellent parallel 6as7 amp but it must be reserved for headphones with sensitivity 90dB or lower to avoid noise

 

[g0ldl10n]

Last night I was able to get the plate current stable at 65mA with 6AS7 plates paralleled.. unfortunately, still had unwanted distortion with higher volumes, so these likely a no go. It isn't all bad news though - I learned a few things along the way.

Will add something here that might be beneficial to someone out there, possibly save a few bucks.

When placing the new cathode resistors for the 6AS7 I needed to change out the cathode bypass caps for higher voltage rated ones as the voltage they were going to see was going to be right on the edge of the maximum voltage the caps I had in there were rated for and as many of you know, I previously swapped in Jupiter Cosmos caps to perform this role.

Well, if I wanted to stay with the Cosmos line it would have cost me $40 for suitable caps, which I didn't feel like spending that much money here with a mod that I did not know if it was going to work or not, so I decided to go with Nichicon KZ MUSE caps (the Cosmos caps still reside on the input) which were significantly cheaper, and lo and behold I like them more performing bypass duties on the output tubes. So there's that

 

[triod750]

I like them more performing bypass duties on the output tubes.

What do they do better?

 

[g0ldl10n]

What do they do better?

Highs sound a lot more articulate, details enhanced and the imaging/separation is notably better, while losing nothing from the lower end of things. Thankfully, I find it a very enjoyable and preferred change.

 

[LoryWiv]

Here is another input that shine in the Ultimate paired with the right output.
Mazda 30L17 and 30L15 (thanks to @TLO for finding these) twin triodes. Currently, the 30L17 is driving a pair of 6AH4GT triode sweep tubes.

Does the 30L17 heater current of 7.2 cause any issue?

 

[TLO]

Does the 30L17 heater current of 7.2 cause any issue?

7.2V is the heater voltage, current is 0.3A. Below is taken from Ediswan databook.
30L17 / PCC806 is the frame grid version of 30L15 / PCC805 with slightly different specs.

Anyway, I cant find the detailed datasheet for 30L17 / PCC806 but only 30L15 / PCC805, http://www.r-type.org/pdfs/30l15.pdf
For your reference, I have tested both at 6.7V heater voltage and 210V plate voltage (as measured on my amp) with no issue. They run very well with great sound.

P.S. It is advisable to connect both K1 in and K1 out together to prevent unwanted noise.

 

[albertmuc]

A tone to die for, listened with the HD800s:

Miflex, 6BW4, 6060T Brimar, EL12 Spez.

6BW4 makes the sound smoother (vs EZ81), which fits very well

 

[triod750]

A tone to die for, listened with the HD800s:

Miflex, 6BW4, 6060T Brimar, EL12 Spez.

6BW4 makes the sound smoother (vs EZ81), which fits very well

Who made the EZ81?

 

[triod750]

Here is another input that shine in the Ultimate paired with the right output.

Important, as always. Few, if any, tubes I have tried have make it or break it qualities on their own.