[YzaKun]

Thank you for your advices. 
StalkerAssassin: I own a pair of 6AS7G too and they're great, indeed. But I like my Sylvania 7236 even more. Maybe I should try to find some other driver tubes for them.
WALL-E: Very revealing info, thanks! As I'm still new on head-fi; did you publish your measurements somewhere or is there any thread/ webpage with a table and general overview? Thanks!

 

[WALL-E]

Quote:

WALL-E: Very revealing info, thanks! As I'm still new on head-fi; did you publish your measurements somewhere or is there any thread/ webpage with a table and general overview? Thanks!

 
I believe I did some on this thread, the measurements were taken by ARTA software using a computer! external loopback (line-out - line in).
Most digital scopes is useless for audio analysis because they are only  8 bits, to measure the THD, THD+N or IMD, you can not see anything that's going on below-50 dB for example a cassette tape noise is 60 dB and you can hear it without any effort so,  there is one exceptions at reasonable price PicoScope power full tool for audio, I add this scope to my wishlist for Christmas.

The professional equipment (audio analyzers) to measure the harmonic distortion like (Ap) Audio Precision costs fortune BTW the magazines like Sterophile, Hi-fi news and many more use them to test the audio equipment.
Being an amateur hobbyist I cannot afford such an expensive stuff.
Nowadays computer audio is coming on strong and computers can be used as a audio tool with software like ARTA or RMAA if properly calibrated will be very useful. BTW the la figaro boss used similar program RMAA to measure his reference 339 and you can find his graphs in this thread too.
But arta has one advantage over rmaa, it is real time analyzer and you can see what is going on at real time.
below few graphs, not yet modified 339 with set of 6N13PJ and 6*4 and set of 7236/5693, alternately 33 and 300 ohm of the dummy load resistor, with volume setup bit louder then my normal listening level.
 
 

 
6N13PJ/ 6*4 dummy load 33 Ohm

6N13PJ/6*4 dummy load 300 Ohm
 

7236/5693 dummy load 33 Ohm
 
 
 

DK339 5998/5693 50 Ohm                   DK339 7236/5693  50 Ohm
 
as you see dominate even-order harmonics with the 2nd highest, which are perceived by our brain as a pleasant so even set stock tubes with total THD over 1.6% with the low impedance cans will still sound pleasure to our ears.
the two bottom graphs show clearly better performance of TS 5998 with the low impedance cans.

 

[hifimanrookie]

RCA 6AS7G. And TFK ef80 for he 500

Does the ef80 fit directly to my 337?

 

[Ultrainferno]

Quote:

Does the ef80 fit directly to my 337?

 
It doesn't fit the 339 directly. I don't know what input tube types the 337 can take. Don't forget this is the 339 thread, maybe you should check out the 337 tube rolling thread

 

[hifimanrookie]

I bought this amp with a view to tweak it later, the idea to mod this amp was born in my head before I bought it. I began from LF332c in which i did simply mod consisting in an exchange of output coupling caps, what was like day & night, the sound improved dramatically but for lack of space to do something more serious I sold it and bought LF339.


In preparing to this mod I had to think long-term, to do this once and good.

So replaced the caps in a filter CRCRC (power supply) for a Low ESR(equivalent series resistance), in a  power supply it is important to have a low ESR because the capacitor is rapidly charged and discharged to maintain the output voltage and current flow, so current with resistance will creates a voltage drop. It is not only about the voltage drop but also ESR caps have few time longer life than general purpose caps. The other part of that rule is to increase the capacitance about 20% now is about 3000uf and the max working voltage rating from 200V which was wery close to the max pick!  increased to the 400V/105 Celsius.

Also replaced the bridge rectifier for a ultra fast HEXFRED(low forward voltage drop and low noise switching) to provided clear DC voltage.

The output coupling caps increased from 130 to 265uf (Mundorf MKP film capacitors) will allow extended bass response into low impedance headphones, bypassed with small oil Film Caps will improve the highs. All resistor used to this mod was 1% precision Non-Inductive and Non-Inductive Wirewound Resistors in power supply and for cathode output, for a driver section Japanese-made beauties Amtrans "premium" carbon film resistors. Using precision resistor will  help to match the section of amp. Rewiring this amp I tried to not mess too much and keep the symmetrical layout as soon as it is possible.
NEOTECH - Solid Core Copper, Teflon Jacket (UP-OCC Mono-Crystal design) for filament (16 awg) and for a power supply (18 awg), all connection between tubes in&out with the use of Amtrans Gold Plated Solid Core OFC.  All hook up wire have teflon Insulation so they are heat resistant and not gonna melt.

That all about this mod.

 

Quick question...u think a 337 would benefit from same mods? I know its a darkvoice but in basic its same amp right? Only the 339 is a. Improved version? And wow..u did a wonderfull job..one of a kind..and not a hefty price tag also!

By the way..is there a difference between rca 5693 reds and general electric 5693 reds? I can get a pair of the latter for a good price and the seller says that all 5693 reds are made by rca no matter the branding on the glass..is that correct?

 

[Ultrainferno]

Quote:

 I can get a pair of the latter for a good price and the seller says that all 5693 reds are made by rca no matter the branding on the glass..is that correct?

 
Also made by GE, Sylvania, Tung-Sol, Westinghouse but they should all be "RCA" tubes. But it's not glass

 

[Ultrainferno]

5693 = 6SJ7 (USA) =  6J8P (Chinese).
I hope your 337 works with these input tubes

 

[hifimanrookie]

​

Are you sure your amp can take these? (I don't think so)

Yep it can.. Two independent tube sellers confirmed me..as long it has same specs or something as the tung sol 6sj7 gt i now use..a pair of tung sol 5998 nos and a pair of bendix 6080wb with graphite blocks are on their way to try instead of my svetlana powertubes..

 

[hifimanrookie]

​

5693 = 6SJ7 (USA) =  6J8P (Chinese)

have an advice for better tubes thn my already good tung sol driver tubes i own?

 

[hifimanrookie]

Also made by GE, Sylvania, Tung-Sol, Westinghouse but they should all be "RCA" tubes. But it's not glass

Ok..my fault..name is branded on bottoms..

 

[Ultrainferno]

As you use TS 6SJ7GT you can use 6J8P and 5693. They gave you the correct info.
No offence Hifimanrookie, but it looks like you should really read up on "Tubes" in general. Start here: http://www.head-fi.org/t/336151/proposed-darkvoice-337-dedicated-tube-rolling-thread
Also a lot of tube selling sites have a lot of good info on tubes and equivalents. In my opinion everyone who owns a tube amp should at least know what he's doing

 

[hifimanrookie]

As you use TS 6SJ7GT you can use 6JP8P and 5693. they gave you the correct info

Thanks how do they scale against the tungsols i have?

 

[hifimanrookie]

As you use TS 6SJ7GT you can use 6J8P and 5693. They gave you the correct info.
No offence Hifimanrookie, but it looks like you should really read up on "Tubes" in general. Start here: http://www.head-fi.org/t/336151/proposed-darkvoice-337-dedicated-tube-rolling-thread
Also a lot of tube selling sites have a lot of good info on tubes and equivalents. In my opinion everyone who owns a tube amp should at least know what he's doing

No offence taken..i will read myself up on tubes..thanks..i am only into tubes since a month or so..thanks for the link!

 

[WALL-E]

Quote:

Quick question...u think a 337 would benefit from same mods? I know its a darkvoice but in basic its same amp right? Only the 339 is a. Improved version? And wow..u did a wonderfull job..one of a kind..and not a hefty price tag also!
 

 
I think it would, maybe not same mods but similar. It hard to say looking only from picture of internal layout circuit, as I see the power output of the Darkvoice 337 is a cathode follower configuration with two triodes in parallel, same voltages but double current and more output power, same as LF339, the difference could be in input wiring both can use pentodes like 6sj7 but the LF339 have it connected as a triode, to make it more interesting it used very rare configuration with grounded - plate BTW... I have never seen such connection pentodes in any known to me pre-amps I think it is a way to run it at lower current than normal and might give lower noise. Generally triode connection is desirable for a pre-amplifiers because triodes are inherently less noisy than pentodes self.
If you can draw a schematic and do some measurement voltages and currents it would be very helpful?

 

[Ultrainferno]

I decided to stop using the 5998 in my 339. I didn't recognize the amp anymore I fell in love with.
Switched back to some good old 6AS7G Chatham tubes and my precious is back...warm, smooth, bass...oh baby I've missed you.
The 2399/5998 I would only suggest if you need the extra power for the LCD2, if not my suggestion is to stick with the warmer sounding tubes.
Perfection? It's darn close!