[OctavianH]

Since I see that different tube types are biasing at different currents, my suggestion would be to write in the table you prepare also the current draw for each tube type. If different tube types draw different currents in the circuitry of this amp, this means you have variable output power? On my amp with manual grid bias things are differently. I always keep output stage on the same 200V/20mA which for me means 4W dissipation. For curiosity, a 6V6 at which current biases? Because the elephant in the room here is the anode power dissipation. If you have different currents on different tube types it is not easy to determine via a datasheet if a tube will work or not. Of course, maybe I am wrong.

PS. Tube parameter variation is quite big. I have here tubes of the same type measuring 90%, 100%, 140% of the nominal values. The stronger one will bias at the same value as the weakest? Is this a risk if you are close to max 60mA allowance?

 

[UntilThen]

I cannot answer any of the technical questions. Eric can but question is whether he wants to share it. What I'm interested in is if a tube is safe to use in Ultimate - whether it will shorten the tube's life or damage the amp. In all of the tubes I've rolled, I've consulted Eric and he has check the tube datasheet and also the TP's reading. Most of all I'm interested if a tube sound good in Ultimate. However this can be subjective. Depends on who hears it and with their setup. Personal preference.

I see no reason to record any of the bias readings because the normal user wouldn't be too interested in it. Even if they know, they can't alter the bias. I post it only to show that it's not over the max 60mA. Furthermore most Ultimate have the TP installed for free. It will give the owners something to do for themselves.

What is important for Ultimate users is that they need to consult Eric if they are going to try a new tube that is not already recorded in Zachi's spreadsheet. Remember Eric said the amp is design for 6Y6. Any other tubes that can be used are a bonus - and we know already a lot of them can be used safely.

 

[UntilThen]

Pretty sure power does not vary. It is 3w into 8 ohms. However changing tubes affect the gain and some tubes will definitely sound louder. Gain isn't power as we know.

I am sure the 'Man' himself will reply to me when he gets the chance to look into his email.

This morning Eric told me that the plate voltage on Ultimate is 180v. You can consider it as 200v.

 

[UntilThen]

After a few hours of KT170 and KT150, it is quite clear they sound like integrated amps do. I know it's cliche to say that just because they are very big power tubes but that's what they sound like especially when powering Susvara.

My 3 words to describes these tubes:-

BIG, BOLD and BEAUTIFUL. BBB !

 

[UntilThen]

Since I see that different tube types are biasing at different currents, my suggestion would be to write in the table you prepare also the current draw for each tube type. If different tube types draw different currents in the circuitry of this amp, this means you have variable output power? On my amp with manual grid bias things are differently. I always keep output stage on the same 200V/20mA which for me means 4W dissipation. For curiosity, a 6V6 at which current biases? Because the elephant in the room here is the anode power dissipation. If you have different currents on different tube types it is not easy to determine via a datasheet if a tube will work or not. Of course, maybe I am wrong.

PS. Tube parameter variation is quite big. I have here tubes of the same type measuring 90%, 100%, 140% of the nominal values. The stronger one will bias at the same value as the weakest? Is this a risk if you are close to max 60mA allowance?

Here is Eric's answer:-

Hi Matt,

As you have known, this UltimatE is designed for this particular low working voltage but high current tube 6Y6G / GA / GT. and the amp could deliver about 3 to 4W power. very suitable for headphone & sensitive speakers applications. Incidentally you guys try to plug in other tubes, no problem, these tubes may not be in their best / optimal possible performance. But take care not to damage the amp AND the tubes..

To protect the amp is just using tubes with the voltage measured from the TPs not over too much on 60mV ( equivalent to 60mA current, Why? How? ... Omitted 200 words here OK ).

To protect your tubes - having the voltage measured on the TPs ( representing mA), multiply 180V giving you roughly the plate dissipation, check against this with the datasheet, and not to over that in the datasheet of the tube...Most big tubes have high plate dissipation usually not a problem, only those small tubes, we need to take care and check.

I understand you guys had experimented with many tubes and made a list that would be helpful for others... Well Done.

Cheers

Eric

 

[UntilThen]

So true to the standard of a professional amp builder, Eric state his case and remind you that the amp is designed for 6Y6G. So those of you who have bought exotic tubes, you can go and sell in ebay for peanuts prices.

Just kidding. If Ultimate cannot use KT88, EL34, etc, I wouldn't be buying it because when you hear the amp with KT170, there is fire in your belly and Christmas come early.

What I am hearing now with Susvara and Lory's Super Silver Ultimate with Raytheon 6j5gt and KT170 fills me with gratitude that music can be so involving and intimate. So powerful and transcendent, heaven is just one floor above. So sweet you're wondering if someone added Manuka honey to it. So personal you're going to write a 200 page essay to describe it.

So without further ado, I'll leave it to Ultimate owners to give their impressions while I listen to Mark Knopfler's 'Telegraph Road'.

 

[LoryWiv]

Alright forget about boxing for a moment. Both tubes are supremely powerful. KT170 is a bit more powerful but both will drive Susvara like a doll. Incredible immense power and this is in Ultimate.

EL156 biased at 41.8mA while KT170 biased at 54.1mA.

These tubes are not exactly neutral but they definitely lean more to neutral than warmth. So if you're looking for rosy romantic glow, they are not it. They are very powerful, masculine tone. Try some Metallica songs and be blown away.

Question about bias measurements, Matt: Do you need to wait a specific period of time after tubes are powered on (EG - 30 minutes) before steady state bias occurs and accurate test results can be obtained?

 

[UntilThen]

Question about bias measurements, Matt: Do you need to wait a specific period of time after tubes are powered on (EG - 30 minutes) before steady state bias occurs and accurate test results can be obtained?

You don't need to wait 30 mins. 10 mins is sufficient. You can always test again after an hour if you want.

 

[UntilThen]

For your info, EL156 has always measured lower. Even on Odyssey, I can see it's less than 50mA. In both amps though, the sound is beautiful and does not appear to be under driven to my ears. You can hear it for yourself.

 

[UntilThen]

KT170 is not just for hard rock and heavy metal. It's beautiful with 'Yesterday once more'. I connect very well with my departed friend @pctazhp because he love these kind of songs.

 

[UntilThen]

Oh wow I just discovered a whole new group of vocalist that sing like angels. Thanks to @Lorspeaker for bringing them to my attention. I'm like 8 years too late.

 

[Deleeh]

Greg the 'Jensen' xlr input transformers are not the same as the Jensen caps company. It is some chinese made transformers and they call it Jensen. However don't underestimate made in china stuff. Just like the timE o/p transformers used in your Ultimate, that is from china made according to Eric's spec.

Yes, the translator sometimes makes pranks for me.
And is sometimes translated in a funny way.

I didn't know that there is also a Chinese manufacturer called Jensen.
I thought it was the US company that made it.

And yes, there is certainly no bad stuff from China.
All my Dac's and DDC come from there.
The only thing I'm a bit picky about is amps .

 

[UntilThen]

I didn't know that there is also a Chinese manufacturer called Jensen.

The XLR transformer name is Jenson and not Jensen. A mistake when Eric first type it out to me or my eyes is having double vision when I read it.

 

[UntilThen]

TP readings of my tubes

Tube	mA
Ken Rad 6y6g	64.4
GE 6y6g	62.5
National 6y6g	66.8
Philco 6y6g	66.1
Radiotron 6F6G	43.7
Fivre 6V6G	42.5
Sylvania 6Y6GA	59.6
Tung Sol KT150	58.1
Tung Sol KT170	54.1
Siemens EL81	57.2
Telefunken EL12 spez	35.4
Siemens EL12	32.5
RFT EL12N	36.5
Philips Miniwatt EL34 metal base	43.1
Tung Sol 6550	55.1
Mullard EL32	42.7
La Radiotechnique EL39	43.2
Telefunken EL156	41.8
China 350b	41.2

 

[UntilThen]

Don't be alarm at the 6y6g readings above. I'm recording this for my own info, so I can store it in my signature.

When I point out to Eric that the 6y6g are much higher than 60mA, he said within a tolerance of 10% is ok. When I point out to him that the GE 6y6g is more than 10%, he said...

If the power and filter transformer is NOT hot, and the amp works OK. no problem..
Actually the power transformer is with higher capacity than what is needed, Only the filter choke is designed to handle 150mA... Your big Silk output can handle even higher.