[Dobrescu George]

I posted my in-depth analysis video about Feliks Euforia!!

There's a full written review incoming as well

 

[mordy]

Hi h1,
I still have my Euforia. If I wanted to sample the latest developments in improving the sound of it, what should I get?
1) A pair of KT66 as drivers and a pair of KT88 as powers
2) Quad of KT88
3) One KT66 and one KT88 as drivers and a pair of KT88 as powers
Which brands would you recommend for the KT66 and KT88? All Gold Lion reissue?
Four adapters - I assume that they all are the same? Can't seem to find the adapters listed.

 

[DecentLevi]

It happens to be the "7581 instead 6AS7" adapters from eBay (6L6 series) adapters that work for all of the above. It looks like the answer you will get is leaning towards Quad KT88 Genalex, but wait for others to chime in. Also I read something recently on either this or the Glenn thread that KT series tubes are generally not acclaimed very well on most other OTL tube amps, however they pair especially well with the Elise/Euforia due to something about its' unique pinout or something to that effect. So they may/not sound just as good in your Glenn OTL amp but I may be wrong.

 

[connieflyer]

HI Mordy, the adapters are available here. https://www.ebay.com/itm/193142155772?ViewItem=&item=193142155772
I have tried the 7581a's and the KT66 quad, KT66 and KT88 and now the quad of KT88, and of them all the quad of KT88 is by far and away the best I have heard in Euforia. I bought the KT66 and 88 from Upscale Audio, the US distributor for Feliks Audio. Prices are a little, a few dollars more than other places, but they offer tube matching and for power tubes, the KT88's for about 3 dollars a 72 hour burn in. Well worth it in my opinion, great service and no problems at all. I corresponded with Kevin and he is very prompt with replies and info. https://www.upscaleaudio.com/collections/power-tubes/products/gold-lion-kt88
This is my opinion with my equipment. Others hold other conclusions.

 

[mordy]

Thanks for the help.

 

[LoryWiv]

Headfi user @Deyan makes 6L6 --> 6AS7 adapters that also work very well with the 7581A / KT tube family. I have used them with the former, and have 4 more to use when nmy KT66's and KT88's arrive.

 

[hypnos1]

Hi h1,
I still have my Euforia. If I wanted to sample the latest developments in improving the sound of it, what should I get?
1) A pair of KT66 as drivers and a pair of KT88 as powers
2) Quad of KT88
3) One KT66 and one KT88 as drivers and a pair of KT88 as powers
Which brands would you recommend for the KT66 and KT88? All Gold Lion reissue?
Four adapters - I assume that they all are the same? Can't seem to find the adapters listed.

Hi mordy.

Well done for keeping hold of your Euforia...you're in for a real treat with these KT tubes lol!

And as @connieflyer said (beating me to it, but I don't mind one bit!! ), the best combo will in fact be QUAD 88!!...and yes again - by far! And another yes, the 6L(V)6/7581 adapter is the same pinout. As for which 88s, I myself - and others here - are finding the Russian reissue Genalex Gold Lions to be extremely good. Most other folks using these tubes also sing their praises, with the occasional problem turning up. I suspect the latter are possibly down to unreliabe sources, and/or plain bad luck lol! Hence cf's good advice for sticking to a reliable supplier such as UpscaleAudio in the US, or anyone else who offers pre burn-in and testing of tubes before shipping. I'm also quite sure that we will be much less likely to encounter any problems, with these tubes not being driven anywhere near as hard as would be in a power amp

And so folks...................... an update from me on said KT88 quad combo..........................

My fourth GL KT88 arrived today, eagerly awaited after cf's findings re the quad - (well done for going straight in, mon ami!). To tell the truth, with the one as driver along with a KT66 I wasn't expecting a great deal more...wrong! Even with just a couple more hours on the 20 hr pre burn-in from HotRox UK, all I can say is...cf is absolutely right.

I'm still not quite believing the difference coming from replacing the 66 driver in the left channel with another 88. Basically, all the qualities I've described so far go up yet another notch (or 2!), the most obvious ones being even more 3D enhanced stage; even more detail/solidity/punch/definition and clarity to the bass (in my system); sharper attack to notes, and with subsequent greater sustain and decay; voice even more contained within its own space - as are instruments - and with more precision still in pronunciation. Overall is a sheer mastery of control, balance and cohesion...and all this is just for starters lol! Can't wait for more hours on this last KT88...not to mention the full works on converting them as opposed to sitting in my adapters...(shall be praying extra hard for this final surgery!). Speaking of scalpels, these KT88s simply cut through to the music like I've never heard before...but not in any way 'dry' or (negatively) clinical...again, in my own system at least.

And another - very important for some! - bonus...NO HUM from my HD650s!!!..and total, deathly black background from the Empyreans. The lower gain from the 88 compared to the 66 means turning up the vol knob a bit more, but brings this wonderful benefit. And even with the vol knob turned up quite high, I get no distortion whatsoever.

And so another pic of my current setup, but will be glad when I can get the 2 as drivers converted using the larger gold plated bases, to match the powers lol



ps ...cf, female voices are now simply gorgeous - or, rather, even more so than before! I'm falling in love all over again with Loreena, Mim Grey ('Purple Sky'), Joan Collins ('A case of you')...and this is just for starters...(sshhh, don't tell 'She who must be obeyed'!! )...CHEERS!...CJ

 

[connieflyer]

CJ, those gold adapters are perfect size looks like they were made for them!

 

[hypnos1]

CJ, those gold adapters are perfect size looks like they were made for them!

Actually cf...they are lol!! ...thank goodness! ...(but the shallower base makes it just a bit more interesting in use!)...CJ

 

[LoryWiv]

The lower gain from the 88 compared to the 66 means turning up the vol knob a bit more, but brings this wonderful benefit. And even with the vol knob turned up quite high, I get no distortion whatsoever.

Hi @hypnos1. Glad you're enjoying the KT88 quad incrementally more than other tube combinations. Can you elaborate on the difference in gain (amplification factor) between the GL KT66 versus KT88? I've been unable to find this specification in any of the related tube data sheets. Thank you, good sir.

 

[hypnos1]

Hi @hypnos1. Glad you're enjoying the KT88 quad incrementally more than other tube combinations. Can you elaborate on the difference in gain (amplification factor) between the GL KT66 versus KT88? I've been unable to find this specification in any of the related tube data sheets. Thank you, good sir.

Hi LW.

Yo, this quartet of GL KT88s is proving to be the crowning glory of years of messing around with countless different tubes that my poor old amps have had to endure lol!! And amazingly, they still work flawlessly lol! As with @connieflyer , my current setup is performing so well that I have no desire whatsoever to even look at other amps any more! And besides, who else makes a headphone amp - or any other for that matter - that uses the KT88 as drivers to the same as powers? I personally wouldn't now even consider trying any other driver for the 88 powers...they meld together far better than I ever thought/hoped for.

As for the 66 vs 88 gain issue, I actually only came across this in one of the myriad posts I've scoured from users in other (power) amps. And then I realised this would account for the much lower hum thru my HD650s when substituting a 66 driver with an 88, and complete absence with 2x 88 drivers (replicating the experience I had with my mesh plate EL11s compared to the standard tubes - higher gain obviously via the mesh plates!). Plus, the need for slightly higher volume knob setting also confirms this.

 

[LoryWiv]

Hi LW.

Yo, this quartet of GL KT88s is proving to be the crowning glory of years of messing around with countless different tubes that my poor old amps have had to endure lol!! And amazingly, they still work flawlessly lol! As with @connieflyer , my current setup is performing so well that I have no desire whatsoever to even look at other amps any more! And besides, who else makes a headphone amp - or any other for that matter - that uses the KT88 as drivers to the same as powers? I personally wouldn't now even consider trying any other driver for the 88 powers...they meld together far better than I ever thought/hoped for.

As for the 66 vs 88 gain issue, I actually only came across this in one of the myriad posts I've scoured from users in other (power) amps. And then I realized this would account for the much lower hum thru my HD650s when substituting a 66 driver with an 88, and complete absence with 2x 88 drivers (replicating the experience I had with my mesh plate EL11s compared to the standard tubes - higher gain obviously via the mesh plates!). Plus, the need for slightly higher volume knob setting also confirms this.

Understood, thank you @hypnos1. I should receive a pair each of GL KT66 and KT88 in the next several days. I have adapters by Deyan ready to go, and look forward to listening. I enjoyed the TS 7581A's, am currently running NOS TS 7236 powers w/new production TS 6SN7GTB drivers which is quite pleasing as well. Seems there are an abundance of riches / good choices with our amps. I may eventually try a quad of KT88's as well but trying not to rush the journey nor break the bank!

 

[hypnos1]

Understood, thank you @hypnos1. I should receive a pair each of GL KT66 and KT88 in the next several days, have adapters by Deyan, and look forward to listening. I enjoyed the TS 7581A's, am currently running NOS TS 7236 w/new production TS 6SN7 which is quite pleasing as well. Seems there are an abundance of riches / good choices with our amps. I may eventually try a quad of KT88's as well but trying not to rush the journey nor break the bank!

Yes indeed LW...so many good combos for our amps. It's a pity however that we discovered the superiority of quad KT88s a bit late in the day...but this journey of discovery is one that can be very educational on the way to finding just what suits us all best lol! And as usual, different combos may prefer different setups...so, good luck with your own particular quest ....(wallet permitting! )...CJ

 

[mordy]

Hi LW.

Yo, this quartet of GL KT88s is proving to be the crowning glory of years of messing around with countless different tubes that my poor old amps have had to endure lol!! And amazingly, they still work flawlessly lol! As with @connieflyer , my current setup is performing so well that I have no desire whatsoever to even look at other amps any more! And besides, who else makes a headphone amp - or any other for that matter - that uses the KT88 as drivers to the same as powers? I personally wouldn't now even consider trying any other driver for the 88 powers...they meld together far better than I ever thought/hoped for.

As for the 66 vs 88 gain issue, I actually only came across this in one of the myriad posts I've scoured from users in other (power) amps. And then I realised this would account for the much lower hum thru my HD650s when substituting a 66 driver with an 88, and complete absence with 2x 88 drivers (replicating the experience I had with my mesh plate EL11s compared to the standard tubes - higher gain obviously via the mesh plates!). Plus, the need for slightly higher volume knob setting also confirms this.

Hi h1,
Did you come across an actual number for the amplification factor of the KT88 and KT66?

 

[hypnos1]

Hi h1,
Did you come across an actual number for the amplification factor of the KT88 and KT66?

Hi mordy.

Sorry, but no I'm afraid...just a comment on the KT88 being lower than the 66. And you know me - my rather foolhardy/unorthodox approach to tube experimentation has never gone into checking specs beyond the obvious ones to try and avoid drastic incompatibility/disaster lol! ...and for which I'm eternally grateful for having survived such folly!! (or, rather, my amps...not to mention headphones! ).

Anyway folks, while on this subject of gain, I'm happy to report that after the absence of hum now from both KT88s as drivers and powers thru headphones, I'm now checking performance via pre-amp out to my Vincent SS amp and Tannoy XT6f speakers. And not only is there still no hint of hum whatsoever, but the bass coming from Raymond Daveluy's Bach and Widor Toccatas in 192kHz/24bit is not only going even deeper than before (which was already superb with the KT66s), but is rumbling through my whole body in a way that defies words...so I'll just say...I can't believe it...(plus, I'm waiting for the neighbour to knock on the wall lol! ).

Going back to the Empyreans and with more hours on my last 88, yesterday I wanted to see how these KT88s deal with older recordings, and I was surprised at how good they made them sound...(was expecting a case of 'no mercy given!!'). And not simply good, but even better... just as with more recent well engineered material. So far, fairy dust has been sprinkled on Peter Paul and Mary's 'Ten Years Together' (I love especially their 'Early Mornin' Rain'), and Chris de Burgh's 'Spanish Train and other Stories'...I never realised that such old albums were so well recorded/engineered. These KT88s are once again digging out material in the recordings never heard before.

And so to sum up, these GL KT88s have transformed my own Euforia amp/setup into an almost unrecognisable one...and one that is streets ahead of anything I've heard from this amp until now (trying as I am not to over-exaggerate my statements lol! ). And this with two tubes not yet given the final conversion 'treatment' ...CHEERS!...CJ