Modern 6CA7 Follow Up

[sixpakldp]

I'm due for a re-tube in the near future and wanted to see what everyone thinks about what is currently out there.

There was a post about the new JJ 6CA7 and it looks like all the reviews on that tube are glowing. There were a few references that infer that these may possibly be the best option out there for the money for a plexi style amp given that winged c's are overpriced and now possibly out of production.

So what's the scoop, are these the way to go?

Tubes I own (in various states of wear) and know what they sound like:

JJ EL34L's (currently in my amp)
Tung Sol EL34B
Svetlana EL34 (not winged C's)
SED Winged C's
Electro Harmonix EL34

I have the JJ's back in my amp currently because they have the least wear on them and I found that my Tung Sol EL34B's have what I would describe as a grainy texture to them when pushed. They also tend to get flubby on the neck pickup. My other EL 34's all sound smoother, clear and defined.

My current pre's are Tungsol V1, JJECC083 Longplate V2, JJECC083 Longplate V3.

Curious about 6CA7's and have always wanted to try them and it sounds like the JJ's sound better than the EH's and also if they seem better than anything I have tried thus far.

The SED's and the JJ's are probably what I have liked best out of what I have tried. I'm not paying the premium for the SED's as you can almost get NOS at those prices.

[SteadyEddie]

I love my JJ 6CA7s, but some people here say they didn't like them. I guess it's a matter of preference.
I liked the smooth highs, open mids and big bottom end. If your amp is already a bit dark it might smooth it out too much, that's the only thing I can think of with regards to those who didn't like it.

[stef]

EH6CA7 is a real 6CA7 (beam tetrode) JJ's are pentodes.. I've used and abused EH's and my amp and my ears like them very much, haven't tried the JJ's "version"

[cfljames]

I have a set in my 1959HW and they do sound good in a warm full way like a 6L6 because basically they are a 6L6 that biases like a EL34...I spent the $$$.$$ for the Winged =C= SED'S and prefer them over the JJ6CA7'S because they have that snarl and crunch that is so familiar to what a great EL34 does.....Again as far as cost and performance the JJ'S are good but to me I hear a lot of 6L6 in it which is not a bad thing but not 100% what I wanted....
These did tame the harness this amp had in its stock form minus the bright cap being changed to a 100 verses a 4700 ...But now its for the most part 67 SL/SB circuit that oddly enough likes the stock EL34'S and loves the Winged =C=...
Overall this is a good tube that JJ put out finally, I never had longevity with any tube I have used from them in the past but these impress me so far but again in a 6L6 way...

[54strat]

I have posted before about how much I like the JJ 6CA7. I bought a quad when they came out a couple of years ago so I could put a pair in and have another for backup. I am STILL using the first pair...two years this month now! Granted, I don't play every single weekend, and don't play THAT loud...although some would argue about that sometimes. I still think it remarkable that they have not bias drifted one bit, and still have the big, clean, low end that they had when new. It's supposed to be crazy to use power tubes for this long but I am on mission now to see how long they go

[sixpakldp]

So I finally bought some EH 6CA7 tubes. When I went to bias the today I couldn't get the bias on the 500v setting lower than 60 mv. On the 480v setting I can get it down to where I need it. Is this normal when going from el34 to 6CA7? I didn't do the math but I would assume they need to be somewhere between 30 to 40 mv at idle. Do I need to change resistors similar to Kt88's?

[sixpakldp]

Just read somewhere that a 6ca7 dissipates 30 watts of heat versus 25 for an el34. The B+ on my amp is 480v, therefore I should bias at 43 mv if this is true.

However looking at the cut sheet for jj 6ca7 it appears the rate that tube at 25w dissipation, however that tube is a pentode vs the eh being a triode. Anyone know the specs of the. EH 6ca7? Is 30 watts correct?

[sixpakldp]

Just answered my own question found the cut sheet on the EH here http://www.svetlana.com/pdf/electro-harmonix/6ca7eh.pdf" onclick="window.open(this.href);return false;

The EH definitely bias hotter than my el 34. I put the 34 back in the amp to double check the amp and they are way colder. When I put the 6ca7 back in I run out of room on my trim pots. Got them from the tube depot, they have a sticker that says 55 on all of them which is way higher than my tung sol el34 I bought from them which have 31 on them. Sounds like I need to change some resistors possibly. Let me know what I should do here or if these tubes should bias hotter for some reason.

[demonufo]

however that tube is a pentode vs the eh being a triode.

No it isn't. It might be a Beam Tetrode, which is essentially a Pentode anyway, but with beam forming plates.

[stef]

The EH6ca7 should be biased up to 70% MPD, and they behave just like the 6L6 when it comes to biasing.
Yes, you need to change some resistors in the bias circuit in order to get -40DCV

[demonufo]

Often with different EL34's you may have to change a resistor to get the bias within range. It's no big deal.

Also, I disagree with this "bias at 70%" rule. Trust your ears. Obviously don't go above that point, but it certainly isn't a golden recipe for tone. Also remember, when measuring cathode current, there is also screen current combined, so you can allow a little extra.

[sixpakldp]

Thanks. Should I change the resistors like in the kt88 post then?

[sixpakldp]

Got it figured out thanks for the help.

[demonufo]

All you need to do is adjust the resistance values for the bias feed.