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For 6AS7G tube rollers here ..... - Page 39

post #571 of 1446

Loose glass isn't a problem.

 

Other pollutants might cause a leakage if lodged between electrodes.

If that happens a good shake usually helps. 

 

Best test them before you put them in your amp.

post #572 of 1446

In the 6AS7G family, it is quite common.

 

Quote:
Originally Posted by kramer5150 View Post

Is it common for these tubes to have glass fragments and dust inside?  I have seen that mentioned on the NOS www retailers.  If the tube tests and performs as it should are small bits of dust and glass inside OK?

post #573 of 1446

2399 group buy complete. Thanks everyone!
 

post #574 of 1446
Wow, I've got my bias set at 70mA now and it's like I just got a new amp....extraordinary. smily_headphones1.gif
Quote:
Originally Posted by Xcalibur255 View Post


We only went up 20mA.  That way if the switch was accidentally left in that position with a 6AS7G in the socket disaster would not ensue.  I did not do the work, I only wish I had that kind of talent.  2359glenn is the person who made the modification and is also the builder of the amp.  If I recall the numbers right the amp is setup for 100mA bias for a 6AS7 and the 5998 biases at 60mA in the same circuit, so the values just moved to 120mA and 80mA respectively with the cathode switch.  I'm not certain if 80mA was the ideal bias for the tube based on the curves or if Glenn decided it was best to maintain safety for the reasons stated above, but that 20mA makes a substantial and immediately noticeable improvement in the sound of the tube.  It actually makes the tube sound less harsh and edgy despite being run harder, it just takes on a truthful quality like all great sounding triodes seem to do when they are running well.
post #575 of 1446

Did you make any other changes apart from setting the bias to 70mA?

post #576 of 1446
When I first got the amp, I added a Wima MKP10 .1uf as a bypass to the last filter cap in the power supply. That is the only other change to the amp.
Just to clarify, 70 is the bias for both plates combined (keeping apples to apples across amplifier designs from previous posts). Each triode is individually biased at 35mA.
The PS bypass sits right on the 6AS7 tube socket between pins 5 and 8. One side of the heater (pin 8) is grounded and plate pins 2 and 5 are jumpered on the socket to B+ in the stock WA3.
Other than the bypass cap, the only other change is adding a CCS to each cathode in place of the 1.5K cathode bias resistor. To make the mod as simple as possible (and easily reversible) I just clipped the grounds off the cathode resistors and left them hanging in the circuit. The CCS board then has three easy connections to the amp: B+ (right off the tube socket), ground from a nearby existing post, and a wire to the circuit side of the abandoned cathode resistor.
Quote:
Originally Posted by rosgr63 View Post

Did you make any other changes apart from setting the bias to 70mA?

Edited by GrindingThud - 3/1/13 at 11:17am
post #577 of 1446

Thanks for the valuable and excellent info.

post #578 of 1446
Hi was wondering, are CEA JAN Bendix 6080WB w graphite plate the same as Tung Sol 6080WB w graphite plate?
post #579 of 1446

To my knowledge the Tung Sol 6080WB with graphite plate are Bendix.

post #580 of 1446
Have not read any mention of the Thomson CSF 6080WA in this thread... Anyone have an opinion on that tube?
post #581 of 1446
Bought these cuties the other day. Look similar to the one Golden Monkey posted about earlier in the thread. Canadian GE 6AS7G with copper fins:

Edited by GrindingThud - 3/6/13 at 2:50pm
post #582 of 1446

Sweet looking tubes.  How do they sound?

post #583 of 1446
They are still in transit and I've not had a chance to listen to them yet. frown.gif
I'll post an update when they show up. smily_headphones1.gif
Quote:
Originally Posted by hodgjy View Post

Sweet looking tubes.  How do they sound?
post #584 of 1446
Tubes are in! Aesthetically, they are absolutely beautiful. Clear top, rectangle getter, copper fins....Mmmmm tasty! Rather than write a half page of tube drivel ranting about their warm rendition of an expansive soundstage, and giving me the sensation that I'm sitting amidst animals on the verge of extinction on the Serengeti Plain, I'm going to just say they sound like a quiet 6080. I prefer it to RCA 6080 and winged 6H13C, but not above TS5998 or JAN Sylvania 5998A. I have one JAN Sylvania 5998A I'm in love with and it's my favorite in the WA3 so far. I did just snag a pair of 7802.....with a transconductance of 20K, I have high hopes.
Ray Charles 'give me fever' sounds outstanding....definitely a non fatiguing tube.

Quote:
Originally Posted by hodgjy View Post

Sweet looking tubes.  How do they sound?

Edited by GrindingThud - 3/13/13 at 6:22pm
post #585 of 1446

I have also recently discovered the Sylvania 5998A in my WA3.  It's basically a Sylvania 7236 in a different bottle and without the computer rating.  But, it sounds slightly different to my ears.  I like it.

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