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Dark Voice 339 - Page 74

post #1096 of 2376

Hmm...

 

WALL-E, would you like to explain in more details what is added/changed?

 

Kind regards,

V

post #1097 of 2376

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.
 


Edited by WALL-E - 10/8/12 at 4:06pm
post #1098 of 2376

^^^ Bowing and proclaiming: I'm not worthy!

post #1099 of 2376
Ho hum...Another small weekend project biggrin.gif

You put a lot of thought and effort into that mod. Great work!
post #1100 of 2376
wow Wall-E this is some awesome mod you did! Took your time but looks like it was worth it! I wanted to thank for our correspondance without your help i shouldnt have been able to do my YB339 mod (yellow blue mod). that amp is already so good with cheap parts and yes i admit that for me all the work i put in the soldering was all worth it with sonic improvements and the peace of mind it is as solid as possible and good sounding to boot. your mod looks even awesomer with teflon socket and new power cabling and the nice amtrans resistors! You gave me ideas! Bravo well done!
Edited by telecaster - 10/9/12 at 10:09pm
post #1101 of 2376
It looks like you modified the tube socket wiring, could you eleborate a little about that? Also you kept the 6sj7 driver topology, you like those driver hehe it seems!
post #1102 of 2376

Thank you guys for your kind words...and thus follows more news!
It took some effort, especially to put  the big output caps, size of can of coca each, under the cap cover there was no way to use hacksaw and had to remove two large pieces of metal to fit the caps in, using saw blade, 2 hours of cutting, in chassis I had to remove old and put new thread holes to mount the clips for the kendeil caps, the caps are almost twice as bigger as the original but the rest of that was not to bad.
I decided to do not change the driver tube yet is just as it was, I didn't modified the tube socket wiring just ran the wires different way to improve ground conducting. Yes I like the combination with the tung-sol 6sj7gt or rca 5693 as a driver but I will change it later, matched pair of GEC CV1067 and resistors waiting for that in drawer. The sound is heavily altered by the choice of tubes even unmodded lf339 with good sort of tubes will sound very well.
 


Edited by WALL-E - 10/13/12 at 1:35am
post #1103 of 2376

Yes TS 6SJ7GT is a real treat! I keep them just in case. The case for that amp is a really hard steel! I had to make just Three hole underneath to fit spikes and oh boy it was such a hard work for three miserable holes! I feel for you and you case mod, as I have endured some of that bit too.

 

I made some endless thinking about choosing the 4 100uf mkp, and they fit in the cubical cap, but let them show and I thought why not going for the looks.. If I knew I would have chosen maybe 4 150uf mkl caps!
 


Edited by telecaster - 10/10/12 at 3:30pm
post #1104 of 2376

HI all,

 

I may be joining your club.  I'm debating between the 332s and the 339, but really want the 339.  My wallet's telling me to go with the 332, but I have a habit of under buying and then spending more...this time I may just jump to the top of the line.  With DT880s, will the 339 make that much difference over the 332s?

 

And are there any tips for turning it on the first time.  I'm a tube newbe...do I plug it in with the headphones attached for load, or do I let it heat up and then try it with headphones?  Also, should I try a $100 pair first to see that it work before risking the Beyers (not that I expect a problem, just want to be careful)?  

 

One last question.  On the Website, when I select a region, does that price include shipping or will that be extra?

 

(I even have a bare spot on my shelf next to me where my new amp will go).

 

Thanks.


Edited by BackwardPawn - 10/18/12 at 6:31pm
post #1105 of 2376
Quote:
Originally Posted by BackwardPawn View Post

HI all,

 

I may be joining your club.  I'm debating between the 332s and the 339, but really want the 339.  My wallet's telling me to go with the 332, but I have a habit of under buying and then spending more...this time I may just jump to the top of the line.  With DT880s, will the 339 make that much difference over the 332s?

 

And are there any tips for turning it on the first time.  I'm a tube newbe...do I plug it in with the headphones attached for load, or do I let it heat up and then try it with headphones?  Also, should I try a $100 pair first to see that it work before risking the Beyers (not that I expect a problem, just want to be careful)?  

 

One last question.  On the Website, when I select a region, does that price include shipping or will that be extra?

 

(I even have a bare spot on my shelf next to me where my new amp will go).

 

Thanks.

 



When you select the region, shipping is included of course. Don't forget to order the EF80 adapters.

Procedure for OTL amps: Volume to 0 -> turn on amp (always with tubes) -> Wait at least 30 seconds (if the tubes are faulty you will know it) -> plug in phones -> increase volume -> listen -> decrease volume to zero -> unplug headphone -> Power off

 

Are the DT880 600Ohm? I didn't like the 339 with my 600ohm DT990, only with the 5998/5693 tubes, not with the regular one.

post #1106 of 2376

They are 600ohm...I heard the Chinese tubes were bad and figured I'd be upgrading them eventually anyway--it may just have to be sooner rather than later  I actually have access to a box of vintage tubes from my grandfather (its curently with one of my uncle's neighbors), or I can buy new tubes.  You think the the 5998/5693s will work with the DT880s?  Thanks.

 

EDIT:  Where do I get the EF80 adapters?  They aren't on the site--do they come with the tubes?

 

EDIT_2:  EF80 looks like a type of tube...so you're saying I should get the 339, EF80, and the 5998/5693 for the best sound?  Am I off base here?  Also, where do you buy new vacuum tubes?


Edited by BackwardPawn - 10/19/12 at 7:13am
post #1107 of 2376

ef80 are a kind of tube you are right and some of the best kind are listed somewhere in this thread! You should buy  NOS one from a trusted store that accepts return and your best bet is telefunken EF80 or if you have the money the EF800 which are long life ef80.

The 5998 are pricey and you should get it of course! I haven't cause lack of funds and because I have so many other tubes but I will buy a pair one day for sure!

So many tubes are available for this amp, read carefully and choose a pair and be happy with your sound, its the magic of tube!

The 5693 is also your best bet, if you get 5998/5963 combo get it and be done with it, you will be really really happy and save you some hum troubles... The 5998 are hard to find though but a pair of western 6AS7G NOS and 5693 should be almost as good.
 

post #1108 of 2376

I still have four 2399/5998 NOS tubes for sale ;)

Shameless advertising? Damn right!
 

post #1109 of 2376

I'll get the EF80, but the amp is stretching my budget as it is, so I'll look through the thread and find some other tubes until I can afford the more expensive ones.  Is there any chance my vintage tubes will fit?  

 

My grandfather did electronics as a hobby back in the day and there's a large box of unused tubes that my uncle gave to a neighbor when he got the house.  The neighbor said I'm welcome to anything I want as, they're technically mine (or my uncle's) anyway.

post #1110 of 2376

Quick followup on that last question.  Do I need to test new tubes before use, or can I assume they're in working order?  Among the items the neighbor got was a tube tester.  I was just going to order another off Ebay, until I saw they were about $200.  I hate to be an Indian giver (for lack of a better term) since any tubes I take from him I can test on the spot, but if I'll need it on a regular basis, I may just have to take it back.


Edited by BackwardPawn - 10/20/12 at 8:59pm
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