[DecentLevi]

Finally got a pair of a 6SN7 predecessor - the Tung Sol 6F8G. They live up to their reputation with a glorious very wide sound stage and beautiful tone:

Powered by 2x5A of Cetron 6336B tubes from an external power supply. Discovered that the secret to good sound from these double 6080 tubes is a 20A voltage regulator connected to an ample 20A power supply (or a 20A 6,3v transformer).
Shown here is the voltage regulator attached to the back of the transformer housing using a patented rubber suspension:

I am using a 4" PC fan to cool the amp and voltage regulator. The huge heat sinks on the voltage regulator don't even get warm to the touch.
Both tubes are made by Tung Sol, but one is relabeled Radiocoin. That tube has no markings except for the 6F8G; the TS tube has a an additional marking 22.
The EIA (Electronics Industry Association) three digit codes came into use in 1946; the Tung Sol code is 322, but I don't think that it is related to the number 22 on the tube.
February 1942?
Somehow these tubes are among the most beautiful looking that I have......

Hi @mordy, any comments on the difference in sound between the 6F8G and 6N7 or VT-96 drivers? And does it make any sense to get a pair of both 6N7 and VT-96, or would you say they basically both sound the same?

I was about to get a pair of the latter but I realised I also need an ECC31 adapter. Are there any recommended state-side adapters available or is it only from Hong Kong? And for those 6F8G tubes, looks like you had to custom fashion an adapter?

RE the 20ah 6.v power supply for the 6x power tube board - I have just a transformer unit, complete with switch and wall socket - a very good unit sold by JazzVinyl from his Elise. Are you saying that this sounds better with a voltage regulator in addition to a transformer??? And why?

Finally I get a feeling we're making this look quite challenging to a novice, so hopefully if @xmr0613 would let us know his sonic preference, then we can point him in the direction of an easier combo. Becauase the Euforia also has fantastic performance without any special adapters / circuits as well... And in case some of our previous terms threw you off in terms of 'sonic preferences', what I mean is to explain the sound you're looking for - example: slow heavy bass, fast heavy bass, liquid/sweet mids, natural mids, soft treble, edgy treble, hard hitting drums / dynamics, large soundstage (virtual reality effect), etc...

 

[mordy]

Hi @mordy, any comments on the difference in sound between the 6F8G and 6N7 or VT-96 drivers? And does it make any sense to get a pair of both 6N7 and VT-96, or would you say they basically both sound the same?

I was about to get a pair of the latter but I realised I also need an ECC31 adapter. Are there any recommended state-side adapters available or is it only from Hong Kong? And for those 6F8G tubes, looks like you had to custom fashion an adapter?

RE the 20ah 6.v power supply for the 6x power tube board - I have just a transformer unit, complete with switch and wall socket - a very good unit sold by JazzVinyl from his Elise. Are you saying that this sounds better with a voltage regulator in addition to a transformer??? And why?

Finally I get a feeling we're making this look quite challenging to a novice, so hopefully if @xmr0613 would let us know his sonic preference, then we can point him in the direction of an easier combo. Becauase the Euforia also has fantastic performance without any special adapters / circuits as well... And in case some of our previous terms threw you off in terms of 'sonic preferences', what I mean is to explain the sound you're looking for - example: slow heavy bass, fast heavy bass, liquid/sweet mids, natural mids, soft treble, edgy treble, hard hitting drums / dynamics, large soundstage (virtual reality effect), etc...

Hi DL,
I am new to the 6F8G sound so I need more time to crystallize out how they sound. In addition to the pair of Tung Sol tubes I am now trying out a pair of Raytheon/Philco 6F8G.
First impression is that the 6F8G has an expansive, sweet organic sound - something akin to vinyl vs solid state. Great soundstage and detail as well - a winner.
The 6N7/VT-96 is different - more energetic and punchy and not as sweet and majestic but still very enjoyable.
There is no difference between 6N7 and VT-96 - the latter designation is a military one. You do need special adapters that also work for the 6S7G and 6SN7GT and ECC31 tubes - thought you had these already.
The 6F8G tube has an anode cap and needs special adapters. I am not capable of making my own adapters and usually buy from China; however this guy in Poland makes a beautiful 6F8G adapter which was recommended by UT. It took two weeks for it to come - usually it takes longer from China.
You have a much better setup than me for external power; your transformer puts out 6.3V and therefore you do not need a voltage regulator. I use a PC power supply that puts out 12V and that is why I need a voltage regulator to get 6.3V. My previous voltage regulator was rated 15A but that was not enough for my 2x5A=10A current draw. Apparently the tubes spike a current draw on start-up that was too much for this 15A regulator, and a 20A voltage regulator solved that problem and improved the sound a lot.
Regarding giving advice to new members I am not so quick to direct people to do this or that since people have such different tastes and equipment.
I like inexpensive, good sounding tubes and then the trick is to find good synergistic combinations between driver and power tubes. And is something sounds good it will make everything sound good....
An inexpensive top notch driver tube is the 1952-55 ribbed anode Foton 6N8S and you could pair it with the RCA 6080 or RCA 6AS7G for very good results with not much money.
Or you could buy a pair of Tung Sol 6SN7 black round plates and a pair of GEC 6AS7G. This will sound very good, but you could spend over $1200 on this....

 

[Oskari]

ps. It is the VT52...without the hyphen inbetween!...that is the US equivalent of the EL32/CV1052. The VT-52 is another animal entirely, and cannot (unfortunately!) be used in our amps...

It's even worse than that. There are three different VT52s: RAF VT52, GPO VT52, and US VT-52. It is the RAF VT52 that is the EL32/CV1052 equivalent.

 

[DecentLevi]

Hi DL,
I am new to the 6F8G sound so I need more time to crystallize out how they sound. In addition to the pair of Tung Sol tubes I am now trying out a pair of Raytheon/Philco 6F8G.
First impression is that the 6F8G has an expansive, sweet organic sound - something akin to vinyl vs solid state. Great soundstage and detail as well - a winner.
The 6N7/VT-96 is different - more energetic and punchy and not as sweet and majestic but still very enjoyable.
There is no difference between 6N7 and VT-96 - the latter designation is a military one. You do need special adapters that also work for the 6S7G and 6SN7GT and ECC31 tubes - thought you had these already.
The 6F8G tube has an anode cap and needs special adapters. I am not capable of making my own adapters and usually buy from China; however this guy in Poland makes a beautiful 6F8G adapter which was recommended by UT. It took two weeks for it to come - usually it takes longer from China.
You have a much better setup than me for external power; your transformer puts out 6.3V and therefore you do not need a voltage regulator. I use a PC power supply that puts out 12V and that is why I need a voltage regulator to get 6.3V. My previous voltage regulator was rated 15A but that was not enough for my 2x5A=10A current draw. Apparently the tubes spike a current draw on start-up that was too much for this 15A regulator, and a 20A voltage regulator solved that problem and improved the sound a lot.
Regarding giving advice to new members I am not so quick to direct people to do this or that since people have such different tastes and equipment.
I like inexpensive, good sounding tubes and then the trick is to find good synergistic combinations between driver and power tubes. And is something sounds good it will make everything sound good....
An inexpensive top notch driver tube is the 1952-55 ribbed anode Foton 6N8S and you could pair it with the RCA 6080 or RCA 6AS7G for very good results with not much money.
Or you could buy a pair of Tung Sol 6SN7 black round plates and a pair of GEC 6AS7G. This will sound very good, but you could spend over $1200 on this....

Yup, I'm not quick to recommend tubes to new members anymore, that's why I ask for sonic preferences first... Going by what xmr0613 liked and by the overall however, I would say one can't do wrong with the Mullard 6080 + GE 6SN7 GTA - for a good performing budget combo to add some weight to the slightly sweet / bright-leaning tone of the Utopia headphones.

Great, I'll go for the VT-96 instead of 6F8G since I prefer more of a punchy not so sweet sound. I used to have ECC31 adapters but they were externally powered and I let them go.

I've got a Triad external transformer, which is a nice hand-crafted kit complete with on/off switch and power chord and ceramic tile board, thanks to @JazzVinyl that he used to use with the Elise. As you said, with a transformer outputting the correct voltage, you don't need a regulator - though I do use an external fan as recommended.



Basic impressions of this above addition to the Euforia are as follows:
- Single (compatible) powers sound better directly in the Euforia
- Multiple pairs of tubes sound better with this. EG, 4-6 tubes always sound better than any singe pair of tubes
- This 6x adapter board can enable better overall sound than any combination of tubes directly in the amp, with two caveats: performance with this is highly dependent on synergy amoung chosen tubes, and it can take days or even weeks to try all possible combinations you may have. Also of course for certain recordings you may still find yourself going back to a "one tube per socket" setup on occasion.
- Combos that are NOT compatible or otherwise exhibit distortion/hum with this board are multiple pairs of EL11 /12, and 6BL7 + 6SN7. Literally hundreds of other combinations are possible.
- 6336 tubes: for me, these have a similar performance to the Tung-Sol 5998 in which the bass definition suffers in speed and is somewhat rolled off, dynamics lacking 'snap' and and are a bit closer to the 'sweet' tone than I'd like. This is with NOS mint contidion Cetron 6336 tubes after many trials over weeks, though this may theoretically change with burn-in. also I've noticed that 6336 tubes always perform better when paired with other powers, especially 6BL7 and GEC 6080; more full-bodied, punchy and resolving, vs. a somewhat lacking sound when solo.
- This externally heated power set seems to somehow prefer drivers that are extra dynamic and punchy; 9-pin octals such such as 6N23P, 6FQ7 or RCA 12AV7, also Telefunken EL12 or EL12 Spez.

This mod shown is also heavy, seeming a good 5/8th's of the total weight of the Euforia, but for me it's a great upgrade to the amp!

Disclaimer:
The above are all my personal opinions and are subject to change, and this configuration is not officially sanctified by Feliks Audio.

Hey anybody else notice what looks like a cute little bear hugging my tree out back?


LOL I guess crazy tube rolling (in_addition_to) a hectic schedule can take one off one's rocker. Not to mention crazier combos I've withheld from here. But my system is singing splendid nevertheless!

 

[Scutey]

Finally got a pair of a 6SN7 predecessor - the Tung Sol 6F8G. They live up to their reputation with a glorious very wide sound stage and beautiful tone:

mordy,

If you like the 6F8G "sound" then you may well like the Ken Rad 6F8G, I don't have the TS to compare but the KR has a very nice sound, transparent, very good detail, expansive sound too, good detailed high extension, warm relaxed mids and deep warm bass, for me, a real winner.

 

[mordy]

mordy,

If you like the 6F8G "sound" then you may well like the Ken Rad 6F8G, I don't have the TS to compare but the KR has a very nice sound, transparent, very good detail, expansive sound too, good detailed high extension, warm relaxed mids and deep warm bass, for me, a real winner.

Hi Scutey,
Thanks for the recommendation- you describe the 6F8G sound very well; I would only add the word “creamy” to the description lol.
Will be looking for more, but the price has to be right- seems these tubes sell on their looks alone with commensurate prices....

 

[Scutey]

Hi Scutey,
Thanks for the recommendation- you describe the 6F8G sound very well; I would only add the word “creamy” to the description lol.
Will be looking for more, but the price has to be right- seems these tubes sell on their looks alone with commensurate prices....

Hi mordy,
I agree, "creamy" really sums up the KR in just one word!, you're also right about the 6F8G, although they are lookers, perhaps the George Clooney of tubes? lol, having said all that still love the "ugly" Foton Ribber Anode!

 

[mordy]

Yup, I'm not quick to recommend tubes to new members anymore, that's why I ask for sonic preferences first... Going by what xmr0613 liked and by the overall however, I would say one can't do wrong with the Mullard 6080 + GE 6SN7 GTA - for a good performing budget combo to add some weight to the slightly sweet / bright-leaning tone of the Utopia headphones.

Great, I'll go for the VT-96 instead of 6F8G since I prefer more of a punchy not so sweet sound. I used to have ECC31 adapters but they were externally powered and I let them go.

I've got a Triad external transformer, which is a nice hand-crafted kit complete with on/off switch and power chord and ceramic tile board, thanks to @JazzVinyl that he used to use with the Elise. As you said, with a transformer outputting the correct voltage, you don't need a regulator - though I do use an external fan as recommended.



Basic impressions of this above addition to the Euforia are as follows:
- Single (compatible) powers sound better directly in the Euforia
- Multiple pairs of tubes sound better with this. EG, 4-6 tubes always sound better than any singe pair of tubes
- This 6x adapter board can enable better overall sound than any combination of tubes directly in the amp, with two caveats: performance with this is highly dependent on synergy amoung chosen tubes, and it can take days or even weeks to try all possible combinations you may have. Also of course for certain recordings you may still find yourself going back to a "one tube per socket" setup on occasion.
- Combos that are NOT compatible or otherwise exhibit distortion/hum with this board are multiple pairs of EL11 /12, and 6BL7 + 6SN7. Literally hundreds of other combinations are possible.
- 6336 tubes: for me, these have a similar performance to the Tung-Sol 5998 in which the bass definition suffers in speed and is somewhat rolled off, dynamics lacking 'snap' and and are a bit closer to the 'sweet' tone than I'd like. This is with NOS mint contidion Cetron 6336 tubes after many trials over weeks, though this may theoretically change with burn-in. also I've noticed that 6336 tubes always perform better when paired with other powers, especially 6BL7 and GEC 6080; more full-bodied, punchy and resolving, vs. a somewhat lacking sound when solo.
- This externally heated power set seems to somehow prefer drivers that are extra dynamic and punchy; 9-pin octals such such as 6N23P, 6FQ7 or RCA 12AV7, also Telefunken EL12 or EL12 Spez.

This mod shown is also heavy, seeming a good 5/8th's of the total weight of the Euforia, but for me it's a great upgrade to the amp!

Disclaimer:
The above are all my personal opinions and are subject to change, and this configuration is not officially sanctified by Feliks Audio.

Hey anybody else notice what looks like a cute little bear hugging my tree out back?


LOL I guess crazy tube rolling (in_addition_to) a hectic schedule can take one off one's rocker. Not to mention crazier combos I've withheld from here. But my system is singing splendid nevertheless!

Hi DL,
Tried your recipe with an extra pair of power tubes in addition to the Cetrons - the 6BL7. Unfortunately this did not work for me; the sound became bloated with muddy bass.
Just the Cetrons and certain driver tubes like the VT-96, 6N23P or 6F8G works very well, and I don't perceive any of the negatives you mention above -YMMV....
Also, running the GEC 6080 with the Cetrons amounts to 15A which may be the maximum your transformer can handle.
Maybe you bought the Mullard 6080 when the price was low, but a quick check now shows the price for a pair to be around $110 and up - not sure if this qualifies as a budget tube.
Whereas you could get a pair of RCA 6080 for $15 or less if you shop carefully. Similar prices for a pair of RCA 6AS7G....

 

[Wreckgar7]

Hi guys, been running EL6 tube for a while, really like them. Was wondering if the EL5 tube would be possible to use also?

 

[mordy]

Hi guys, been running EL6 tube for a while, really like them. Was wondering if the EL5 tube would be possible to use also?

Hi W7,
I have used the EL6 which is similar to the EL12 with a different base. Seems the EL5 has the same pinout (be sure to double check) and this is the little I could find out:

"EL6: 18 W power output pentode with almost twice the sensitivity as the EL5, intended for applications designed for normal output pentodes as the EL3, but where twice the output power is desired."
https://www.radiomuseum.org/tubes/tube_el5.html

 

[hypnos1]

It's even worse than that. There are three different VT52s: RAF VT52, GPO VT52, and US VT-52. It is the RAF VT52 that is the EL32/CV1052 equivalent.

Thanks O...the four-pin VT-52 is indeed the only US-made tube here, and VERY expensive...and cannot be used in our amps.

Any eight-pin octal-based VT52/EL32/CV1052 tube should do the job...the ST type being much more expensive (and presumably better, therefore?!) than the very cheap straight-sided version. But @connieflyer will be able to confirm whether this is indeed the case when I can eventually get the parts needed for adapters lol!

 

[hypnos1]

Hi @mordy ...the 6F8G is certainly a well-regarded tube...especially the Tung Sol round plate!

And although I applaud your use, and findings re. the 6336 tube, I must once again advise users of F-A's amps NOT to try this powerful tube. Even though its heater is powered by an external source and a fan is used, it appears this tube can place an enormous strain on the cathode resistors, which Feliks Audio have not configured for.

This is not IMHO at all good for the longevity of our amps, and cannot be recommended. Please, folks, take this as a friendly warning...CJ

 

[connieflyer]

Thanks O...the four-pin VT-52 is indeed the only US-made tube here, and VERY expensive...and cannot be used in our amps.

Any eight-pin octal-based VT52/EL32/CV1052 tube should do the job...the ST type being much more expensive (and presumably better, therefore?!) than the very cheap straight-sided version. But @connieflyer will be able to confirm whether this is indeed the case when I can eventually get the parts needed for adapters lol!

funny you should mention this h, just got all four tubes this afternoon. All 4tubes look to be in very good condition ,original boxes for the straight-sided tubes and replacement boxes for the shoulder style tubes. I was surprised that the got here as quickly as they did. Tubes came from two different sellers so that was interesting. I had a laugh yesterday when the three KR VT 96 tubes came in the date was March of 1944 it was three months before I was born! And I must say they look to be in a lot better condition than I do!

 

[DecentLevi]

Hi DL,
Tried your recipe with an extra pair of power tubes in addition to the Cetrons - the 6BL7. Unfortunately this did not work for me; the sound became bloated with muddy bass.
Just the Cetrons and certain driver tubes like the VT-96, 6N23P or 6F8G works very well, and I don't perceive any of the negatives you mention above -YMMV....
Also, running the GEC 6080 with the Cetrons amounts to 15A which may be the maximum your transformer can handle.
Maybe you bought the Mullard 6080 when the price was low, but a quick check now shows the price for a pair to be around $110 and up - not sure if this qualifies as a budget tube.
Whereas you could get a pair of RCA 6080 for $15 or less if you shop carefully. Similar prices for a pair of RCA 6AS7G....

Peculiar indeed - looks like we are largely getting opposite results with our (externally powered) 6336 tube setup on the Euforia. Considering the great difference between our external power setup (20A voltage regulator + 20A power supply, vs. single Triad a 20A 6,3v transformer; both customized), it's no wonder we're hearing different results. I noticed first hand with my unit how the power source can alter the sound, being that I was actually getting quite a bass anemic / thin sound during the first 8+ hours of external transformer burn-in. I would venture to say that my preferred tube combo would sound good to you on my exact system, as well as yours on your system, both not visa-versa. It's just that our external power is affecting the sound quite differently on each other's systems. The 'take home' on this is that what may sound good on one externally powered tube setup may not sound good on another, so I will be even more cautious on any 'blanket recommendations' for tube combos with this externally powered 6x. setup.

But we do both agree on general driver tube pairings.

Good point, the RCA 6080 is very close to the performance of Mullard 6080 at a fraction of the cost, and though I don't prefer these 'solo', to me has some super outstanding fluke-synergy with other tubes on the 6x powered strip.

Actually I haven't even been using the 6336 recently, save for better synergy on this 6x board (and 1-tube-per-socket) with other combos.

 

[mordy]

Hi @mordy ...the 6F8G is certainly a well-regarded tube...especially the Tung Sol round plate!

And although I applaud your use, and findings re. the 6336 tube, I must once again advise users of F-A's amps NOT to try this powerful tube. Even though its heater is powered by an external source and a fan is used, it appears this tube can place an enormous strain on the cathode resistors, which Feliks Audio have not configured for.

This is not IMHO at all good for the longevity of our amps, and cannot be recommended. Please, folks, take this as a friendly warning...CJ

Hi h1,
You scared me so I disconnected my Frankenstein contraption and switched back to approved power tubes, in this case the GEC 6080. Sounds good with the 6F8G but I miss the 6336B....
Hopefully I will get an amp in the near future that can handle such a load......