[Liu Junyuan]

  To change the sound/sonic coloration, you only need to change the driver tube. The driver is the center tube in front of the amplifier.
 

 
The driver tube uses a 6SL7 tube. There are several versions of this tube, just to name a few.
 
6SL7 GT is the standard version
5691 is the industrial/premium version made by RCA
6SU7GTY/6188 is the premium version made by Tung Sol
ECC35 is the European version of 6SL7
Sophia Electric Premium 6SL7 Grade A is a current production by Sophia Electric.
 
I'm content with either 5691 or 6SU7GTY/6188 for my HD650. Got my tubes from Ebay. The price ranges from $28-$48 each. I got the tubes about 2 months ago.
 
5691

 
6SU7GTY/6188

 
 
 
 

 

Excellent post!

 

[menieres]

 
Excellent post!

 
Thank you.

 

[Dababy]

I just received a RCA 5691 and found it to be a good improvement over the sovtek 6sl7gt that came with the ZD for the HD800. However, I found that I preferred the sovtek tube with the HD650. It seemed to have better treble extension. I am looking at the possibility of getting a 6su7gty or a Sophia electric 6sl7 for the hd650 pairing. Any ideas on what would work best?

 

[Liu Junyuan]

The RCA 5691 is an excellent tube, but is too dark for the stock HD650, as you've discovered.

 

[SilverEars]

Glad there's a dedicated thread so I don't derail the ZDS thread with tube talk.

I bought mine 2nd hand and came with JJ Electr tube. Is that a decent tube? I like the sound overall, so it doesn't seem to be bad, but perhaps get better?

I'm looking for a RCA 5691, but the tube store sells it for whopping $130! There are some on Ebay going for $60 buck or so. Is $60 the going price? Any advice on purchasing on Ebay? Counterfeits, what to look out for etc..?

 

[SilverEars]

5691 red base is perfect for HD800S. It's just a damn good tube in general. I'm floored by it's performance. I've been trying out various 6SL7 varieties and none can really compare to 5691. The improvement this tube brings is signficant. There is no treble peaks, mids are fuller and lush, bass is super tight, and the sound is still fast. It's interesting because the mids are full and the overall response is tight. This tube enhances the imaging significantly. Imaging is so much better. Too bad it's pricey. Based on what I've been reading, the tube is strong and lasts much longer than the other tubes.

The most helpful difference I find is the mids that it enhances, resulting in more even response with better mids definition. Tight and better bass quantity helps significantly as well. It gives it the most perfect timbre. Decay timing is just great!

I've tried various solid-state amps, but this amp does to HD800S none of them can. Make it sound engaging and technical at the same time.