[hypnos1]

As I acclimate to the wild and wooly world of tube amps at times it seems much of my prior "knowledge" is obsolete or even counterproductive. As an example, I pulled the TS 7581A data sheet just for fun and was struck by the operating characteristics as a triode including 5% THD. In my solid state days that would have me running for the exits! Can anyone explain why that is not an audibly negative factor in this context?

Hi LW.

Fear not, mon ami...tubes will always have higher THD figures especially than solid state! This is, in fact, precisely why such users as for guitar amps love 'em.... however, we hi-fi nuts do NOT want too much lol! Tube 'distortion' is also precisely what we love about tube amps vs SS!!

So what is 'too' much? Well it would appear that anything below 10% (Total) - for tubes - is likely to be perfectly OK and unnoticeable to most folks. And so 5% is, actually, not a bad figure at all lol. And don't forget, this will be with the tube driven much harder than it ever is in our amps! And so I would imagine that if it were indeed at all intrusive in any way, @ZRW0 's four, pushed much harder in his power amp would certainly show itself! ...(and he just loves them).

And looking around at some other specs, even well established top class tubes can have this sort of figure...some a good bit higher!

Plus, apparently a more important figure than Total Harmonic Distortion is, in fact, Intermodulation Distortion.

But at the end of the day, the only thing that really counts is, of course...how it sounds!! And I myself have experienced nothing untoward whatsoever from the two I now have running...on the contrary, as I mentioned a while back, turning the volume up to unlistenable levels pushed my EL39 into bad distortion, while the 7581A stayed completely trouble-free .

And so hopefully, LW, this puts your mind at rest a bit more...and hopefully hasn't given you indigestion (as I'm wont to do sometimes lol! )...CHEERS!...CJ

 

[hypnos1]

Well folks, much to my bemusement, the 7581A IS A TYPE OF 6L6 / 6V6 and is also interchangeable with KT66. I believe KT77 and KT88 are interchangeable as well! So don't go out and try this just yet, but my working theory is that your 7581 adapters should also work for 6L6 / 6V6, KT66 - and maybe even KT77, KT88 and EL34. Perhaps @gibosi can chime in?

Furthermore it looks like the 7581A's must indeed hold their weight extremely well amongst counterparts. Interesting read, thanks to @leftside - Also let folks here know what are some other good options to try among these?
https://forum.audiogon.com/discussi...-with-the-tung-sol-7581a-vs-el34-kt66-kt88-6l

Yo DL...the 7581A is basically a 6L6, but with more rugged internals/plate that can be pushed harder, if wanted. Hence I asked Mrsx to list her adapter as for 6L6/7581.

Specs are similar for the KT66, and pinout is the same (being, basically, the European version of the American 6L6 versions - the more powerful ones that is - but in a different bottle...with other differences also...hence its name Kinkless Tetrode [KT]).

Now, whether these European tubes will sound the same as the Russian reissue Tung Sol 7581A is another matter of course - especially in our amps, and not specifically configured-for. Only trial and error will give any meaningful answer...CJ

ps. @connieflyer did in fact already point out 5 days ago (page 452) that the 7581A is the same family as 6L6 versions...

 

[LoryWiv]

Hi LW.

Fear not, mon ami...tubes will always have higher THD figures especially than solid state! This is, in fact, precisely why such users as for guitar amps love 'em.... however, we hi-fi nuts do NOT want too much lol! Tube 'distortion' is also precisely what we love about tube amps vs SS!!

So what is 'too' much? Well it would appear that anything below 10% (Total) - for tubes - is likely to be perfectly OK and unnoticeable to most folks. And so 5% is, actually, not a bad figure at all lol. And don't forget, this will be with the tube driven much harder than it ever is in our amps! And so I would imagine that if it were indeed at all intrusive in any way, @ZRW0 's four, pushed much harder in his power amp would certainly show itself! ...(and he just loves them).

And looking around at some other specs, even well established top class tubes can have this sort of figure...some a good bit higher!

Plus, apparently a more important figure than Total Harmonic Distortion is, in fact, Intermodulation Distortion.

But at the end of the day, the only thing that really counts is, of course...how it sounds!! And I myself have experienced nothing untoward whatsoever from the two I now have running...on the contrary, as I mentioned a while back, turning the volume up to unlistenable levels pushed my EL39 into bad distortion, while the 7581A stayed completely trouble-free .

And so hopefully, LW, this puts your mind at rest a bit more...and hopefully hasn't given you indigestion (as I'm wont to do sometimes lol! )...CHEERS!...CJ

No indigestion, only appreciation, more knowledge and a bit better perspective.

It's easy to get lost in specs. but with the exception of assuring that tube choices are compatible and won't blow up the amp., I believe that given the very similar design with the exception of ability to push total volts a bit higher in Euforia, what is safe for Euforia is safe for Elise, correct?

In any case, I agree "the ears rule." Thank you, @hypnos1, as always.
-LW

 

[connieflyer]

My order from the tubestore came in a day early. Tubes look to be nos and boxes are perfect, no damage. Three hole plates just like they advertised. Matched pair. Just have to wait for adapters now.

 

[mordy]

At the moment, the best price for the 3-hole 7581A on ebay.com ($47 the pair, with just $7 shipping in USA) seems to be : https://www.ebay.com/itm/Matched-Pair-of-Tung-Sol-7581A-6L6-type-amp-tubes-Brand-NEW-in-Box/143024926181?

I do want to point out that this listing has a best offer feature. Nothing wrong in throwing in a low ball offer - a good seller will counter offer and you can save money. And sometimes the seller responds positively to a real low ball offer and accepts it.

Re the defective adapter from China: A reputable seller wants to keep the feedback good and will offer free replacements or money back. I have had several adapters fail from different sellers. One seller refused to replace an adapter where one of the octal pins fell off - no more business from me....

Deyan will do his best to keep people happy and he will tackle any specific project and enjoys challenging and unusual adaptions.

 

[triggsviola]

I know we're all going crazy over the 7581a situation, but I wanted to say that I left music running through the Feliks for a couple days with my EL38s. When I came back to them, holy crap! I get it. The bass control, the bass detail. Before, I though bass was just bass. But now the bass has detail, especially with my Utopia headphones. Like, the difference between a bass clarinet and a tuba has never been so apparent. Also the difference between a bass clarinet playing with a tuba, vs a bass clarinet playing with a bari sax. Wow. I've been missing so much! I'm very happy for now. Of course, I have 4 7581a tubes coming in. How could I not? They're so inexpensive.

 

[hypnos1]

No indigestion, only appreciation, more knowledge and a bit better perspective.

It's easy to get lost in specs. but with the exception of assuring that tube choices are compatible and won't blow up the amp., I believe that given the very similar design with the exception of ability to push total volts a bit higher in Euforia, what is safe for Euforia is safe for Elise, correct?

In any case, I agree "the ears rule." Thank you, @hypnos1, as always.
-LW

Yes indeed LW...I see no reason at all why the 7581A tube shouldn't do wonders for Elise also...in fact, given her slightly 'lighter' presentation than Euforia, I personally would relish the extras lol!

And yes again, it can't be emphasised enough that in this world of 'hi-fi' it is indeed one's own ears that are all that counts at the end of the day!! ...

 

[hypnos1]

I know we're all going crazy over the 7581a situation, but I wanted to say that I left music running through the Feliks for a couple days with my EL38s. When I came back to them, holy crap! I get it. The bass control, the bass detail. Before, I though bass was just bass. But now the bass has detail, especially with my Utopia headphones. Like, the difference between a bass clarinet and a tuba has never been so apparent. Also the difference between a bass clarinet playing with a tuba, vs a bass clarinet playing with a bari sax. Wow. I've been missing so much! I'm very happy for now. Of course, I have 4 7581a tubes coming in. How could I not? They're so inexpensive.

Hi triggs. Glad you too have discovered the magic of the EL38...a superb tube...(you should hear the EL39 lol! ...a shame supplies at a reasonable price have dried up).

Mind you, with the 7581A performing as it is in my own system, and with plentiful supplies at silly cheap (considering) prices, I have to admit this tube is the better buy...(but I'm not getting rid of my 'special' Mazda EL38/EL39 combo just yet!! ...CJ

 

[hypnos1]

And just a quick further update on you-know-what guys...finished an adapter yesterday (so I don't have to keep using my modded EL39 one with anode wire flapping in the breeze lol! ), and popped in a 7581A as driver to 2x as powers...and...yeuch!... However, it simply reminded me to take some of my own medicine and NOT take it at face value straight away...especially when following on from a totally different tube family. Anyway, after several hours' cooking things were (thankfully) much better. But as a driver its output is not quite as high as the EL11, so can't yet assess it properly with such a volume imbalance. But already it's now sounding very promising...will have to get a move on with the other adapter!! ...'Bye for now...CJ

ps @connieflyer ...the faint blue glow has actually got a bit brighter, so will try to get a long exposure shot with the Nikon some time soon. But nothing like yours @ZRW0 ...merde!! )...CHEERS!

 

[connieflyer]

While waiting for the 7185 adapters, thought I would roll some old favorites. Very nice combo here, "Joybringers" and El 38 clear. UT you might remember these, I got the 6n7G's from you back in the old Elise days. Still a great sounding tube, first time pairing it with the El 38's and this combo wants for nothing. Thanks again "old man"!

 

[hypnos1]

OK guys...a few more hours on one of the 7581As as driver to those as powers, and unless things change dramatically in the days to come, it's looking like my mesh plate EL11s have nothing to worry about lol! Although still early days of course, it has a long way to go to match the Valvos...bass especially is still rather boomy, and not hitting anywhere near as solidly or with the same detail. I had expected it to develop a bit more than this by now, but I can't give a definitive finding just yet...this is in my own system of course. As usual, more time will tell......BFN...

 

[connieflyer]

Hello CJ, good to hear about the driver tube so far. Not sure I'm going to follow down that road yet or not. It sounds interesting but I have so many driver tubes, of course if this turned out to be the equal 11 mesh plates oh, of course that would be entirely different. But I also wonder how much the adapter has to do with the sonics. I have ordered a pair of adapters from mrs. X and they are on the way in. I'm thinking with the adapters that you build using the good silver wire how much difference that would make if any. Time will tell I suppose but good luck with that driver tube hope it straightens itself out soon. All the best

 

[hypnos1]

Hello CJ, good to hear about the driver tube so far. Not sure I'm going to follow down that road yet or not. It sounds interesting but I have so many driver tubes, of course if this turned out to be the equal 11 mesh plates oh, of course that would be entirely different. But I also wonder how much the adapter has to do with the sonics. I have ordered a pair of adapters from mrs. X and they are on the way in. I'm thinking with the adapters that you build using the good silver wire how much difference that would make if any. Time will tell I suppose but good luck with that driver tube hope it straightens itself out soon. All the best

Yo cf...I'm still holding out hope that the 7581A as driver improves in the days to come. Even if it can't match the EL11 (especially the mesh-plate ones!), if it can come somewhere near then at the price it could well be a contender for folks who don't have an arsenal of top rated drivers to choose from .

And I am indeed looking forward to seeing if my own adapters, using OCC silver and copper wires are any better sounding than Mrsx's ...I should certainly hope so lol!! But nothing's ever guaranteed in this hobby of ours lol!!

 

[Johnnysound]

..

 

[UntilThen]

4 x RFT EL12N powers, TFK ECC801S drivers, Mullard CV4004 as “B” preamp

Hi Johnny, nice to meet you. Don't think we've met. Soon as I finish dinner I'll reply. Btw, that's an impressive looking preamp with those EL12N tubes. You obviously are into this hobby. I'm on the other hand trying to get out of it. The harder I try to get out of it, the deeper I go. Strange logic isn't it?