Dark Voice 339 - Page 114

http://www.bottlehead.com/smf/index.php?topic=3453.0 Quite a bit of comparison here too. Hope it's useful.

The RCA 6AS7 is right at the bottom pertaining to the Crack amp. Not sure if the findings are true for the 339 as well :(

BTW, any tube rolling guide for the 6922?

Quote:

Originally Posted by Contrails 

RickEC, I do not mean to boast but I did pay $50 for three of them (tung sol mesh) just last week. I thought it was an absolute steal.

But I did pay twice the price for RCA 6AS7G n Red 5693 thanks to customs.

So you win some and lose some...

I guess it boils down to luck, until some businessman put up ridiculous price for the rest to follow suit. Good for you!

Searched in Ebay, turn up nothing.

I finally made the adapter and the TS 6SJ7GT sing again... They have their qualities of their own! I remember why I like them so much, there is this 3D feel, the midrange has incredible depth, bass is smooth. I like! Though pure triodes like the mullard CV1932 is more transparent across the entire Spectrum and bass is stronger. Each tube has its sound identity.

They have this tendency to cut the sharp edge on the upper register that may be a good or bad thing depending on conditions. Relaxing tube and mesmerizing...

Quote:

Originally Posted by telecaster 

Hey Wall-E!

Thanks so much for the image of you latest DK339 mod!

So it looks like you use twisted wire for the heater supply, I guess it could only be good thing regarding noise interférences. Did you had noise issue cured that way?

 

It's not that clear on the photo, did you solder directly to the battery end? I would have thought them to be rather hard to solder because of the metal mass...

 

You don't happen to have Frequency response ARTA graph of auto or fixed/battery bias comparaison?

 

If you fix cathode bias the 6J5 at 1.82V while the bias runs about 2.2V in auto, I would guess you a running less current on the plate is it right? That way it is safer for the tubes.

 

I wanna try the NiCd 2.4V bias and if it's only 10% more than that auto bias, I'll be happy to run the bias little on the hot side as I like to do in my guitar amp!

 

Anyway thanks again for taking time and upload a picture, you are a gentleman!

 

Best to you!

My pleasure,

There was always slightly hum with volume pot set up on max almost not audible on normal listening level with all my input tubes except EF80 and EF800TFK they humed in my DK339. The source of interference could have been of course, the adapter also large carbon resistors across the tube socket in close proximity (above them) of parallel lying heater wiring and the (most suspicious)  electromagnetic field due to the current flowing in the heater wiring. I rid off the grid leak carbon resistor and put in small film resistor soldered directly to the socket pins and replaced the short thin signal wires coming from volume pot to the grid, for DH Labs BL-Ag shield solid-core silver cables and I moved them away from the filament circuit. To minimise the external electromagnetic field, the heater wire should be tightly twisted what I've done very precisely in my own 339, not leaving any loop area as you see on my previous photo. To my surprise, issue with the hum/noise permanently gone, allows me to fully enjoy the cheap but very beautifully sounding tubes,  RCA6AS7G & EF800TFK.

Is not show on picture I made it (solder) directly to the battery the positive and negative pole are copper, nickel plated, scrape off the top layer and can be soldered or you can buy, solder tab rechargeable batteries much easy to do. Very important: battery need to be isolated from the chassis, can not  touch the metal enclosure I used this: self-adhesive cable-tie bases.

Originally Posted by telecaster:
"If you fix cathode bias the 6J5 at 1.82V while the bias runs about 2.2V in auto, I would guess you a running less current on the plate is it right? That way it is safer for the tubes."

This is a compromise if you want rolling tubes u need to find the right bias for all your tubes.

I didn't see why the FR may depend on the bias method...ooh pardon me, it did only when the cathode resistor is bypassed with too small capacitor acting high pass filtering. I did compare the self biased to the LED bias and the main difference is the higher gain about 3dB ARTA and low noise and THD for LED biased cathode.

short about my modified dk339,
there is couple of things I did or I'll do later to improve the amp even more to bring it to another level.

Quote:

Originally Posted by telecaster 

 

I finally made the adapter and the TS 6SJ7GT sing again... They have their qualities of their own! I remember why I like them so much, there is this 3D feel, the midrange has incredible depth, bass is smooth. I like! Though pure triodes like the mullard CV1932 is more transparent across the entire Spectrum and bass is stronger. Each tube has its sound identity.

They have this tendency to cut the sharp edge on the upper register that may be a good or bad thing depending on conditions. Relaxing tube and mesmerizing...

 

 

 

 

You made it! i'm glad i see you happy!

Going to audition the 339 and 339 Ref later ;)

Quote:

Originally Posted by WALL-E 

 

My pleasure,

There was always slightly hum with volume pot set up on max almost not audible on normal listening level with all my input tubes except EF80 and EF800TFK they humed in my DK339. The source of interference could have been of course, the adapter also large carbon resistors across the tube socket in close proximity (above them) of parallel lying heater wiring and the (most suspicious)  electromagnetic field due to the current flowing in the heater wiring. I rid off the grid leak carbon resistor and put in small film resistor soldered directly to the socket pins and replaced the short thin signal wires coming from volume pot to the grid, for DH Labs BL-Ag shield solid-core silver cables and I moved them away from the filament circuit. To minimise the external electromagnetic field, the heater wire should be tightly twisted what I've done very precisely in my own 339, not leaving any loop area as you see on my previous photo. To my surprise, issue with the hum/noise permanently gone, allows me to fully enjoy the cheap but very beautifully sounding tubes,  RCA6AS7G & EF800TFK.

 

Is not show on picture I made it (solder) directly to the battery the positive and negative pole are copper, nickel plated, scrape off the top layer and can be soldered or you can buy, solder tab rechargeable batteries much easy to do. Very important: battery need to be isolated from the chassis, can not  touch the metal enclosure I used this: self-adhesive cable-tie bases.

 

 

Originally Posted by telecaster:
"If you fix cathode bias the 6J5 at 1.82V while the bias runs about 2.2V in auto, I would guess you a running less current on the plate is it right? That way it is safer for the tubes."

This is a compromise if you want rolling tubes u need to find the right bias for all your tubes.

 

I didn't see why the FR may depend on the bias method...ooh pardon me, it did only when the cathode resistor is bypassed with too small capacitor acting high pass filtering. I did compare the self biased to the LED bias and the main difference is the higher gain about 3dB ARTA and low noise and THD for LED biased cathode.

 

short about my modified dk339,
there is couple of things I did or I'll do later to improve the amp even more to bring it to another level.

It is great news that twisting heater wiring improve hum with EF800, that's the only reason why I didn't like the EF80/EF800, because they sound absolutely fabulous in the amp!

I tested my EF80 mullard and TFK EF800 and they DO sound good! Such bass that is thunderous and dynamic, with neverending highs. I only dislike the hum I get and maybe after prolonged time of listenning a small degree of listenning fatigue due to the dynamic nature of the sound presentation.

I will replace the heater wire ^^

Wall-E, you're the man!

About the bias voltage, it seems you are running the bias on the hot side. As it applied to the cathode, if I understand correctly, it is then a negative votage.

The more the tension is near zero, the hotter the bias is, and the more current is going to the plates. If you're bias point was -2.18V, and you are running at -1.85V, you run the tubes with a hot bias, and you should have very dynamic sound, improved gain and lowered distorsion, but it "could" (that I don't know) lessen the ltubes life and be fatiguing on the transformaters.

As it is if you didn't experience ill effect, or didn't saw the tube plate going red, then your bias is not that hot.

EDIT :While the soldering gun was at reach, I rewired the EF80 adapter so I can use my EF800 directly with my modded 6J5 driver 339...

I rewired internally the heater wire as to eliminate any loop space, and I'm glad to say that I don't have any interference with my EF80 anymore! Happy happy!

I now must replace the signal wire so to arrive at a perfect ground noise.

Quote:

Originally Posted by snip3r77 

Going to audition the 339 and 339 Ref later ;)

And it's now back at home powering my HE-500 via ODAC.

Quote:

Originally Posted by Ultrainferno 

Which one?

The 339 bro...The Ref 339 is like 4x the price.

Since I'm using the HE-500, which drivers should I get for the 5998?

I understand that you suggested the RCA 6AS7 Black & Telefunken EF80. Any tube retailers that can supply all of these?

I don't know your local dealers. There are a lot of these tubes on ebay though. Go for the TFK EF80 if you have an adapter, those are cheapest. then the RCA RED (no adapter) then the 6SJ7(w)GT by Tung Sol with mesh plates

Quote:

Originally Posted by snip3r77 

The 339 bro...The Ref 339 is like 4x the price.

 

Since I'm using the HE-500, which drivers should I get for the 5998?

 

I understand that you suggested the RCA 6AS7 Black & Telefunken EF80. Any tube retailers that can supply all of these?

Best drivers to go with the 5998 are the rca 5693 reds or the ts sj7gt mesh plates..imho ofcourse

Quote:

Originally Posted by hifimanrookie 

Best drivers to go with the 5998 are the rca 5693 reds or the ts sj7gt mesh plates..imho ofcourse

Pissed off with my ODAC.

Lugged the 339 to my Hifi system and do abit of re-cabling to my 339.

Now is running

Macbook => Calyx DAC ( powered by Kingrex PSU ) => Cyrus Pre-Amp ==> 339

I think I'm pretty much satisfied with the sound for now :)