New JJ Fat Bottle 6CA7 Review

[talbany]

Amp Tested in 100w Music Man non HRM high plate 220k-150K w/4.7 uf bypass, loaded CTS pots. Preamp tubes NOS Amperex 12AX V1 IEC Mullard 12AX V2 LPS 12AX PI..

Tubes biased 25ma..

Speaker Cab used VVT Oval back 2X12 loaded G12-65's..EV 12L loaded Thiele 806 1X12..

Tube Specs. Matched Quad new Fat Bottle 6CA7's from CE.. Plate current measures 25ma Trans conductance measures 4.8 4.9 respectively

First impressions were very pleasing...With a plate current rating of 25 these tubes hung in strong stout and a nice tight punchy low end even at fairly loud (gig volume settings)..Nice for a D-Style amp IMO.. With the tone controls set straight up and in rock mode there was plenty of low end. More than any old style soft vacuum 6Ca7 I've ever used..
If you’re a fan of output tube distortion at lower volumes perhaps a plate current rating of 18 would be better suited as a matter of reference..

Where the similarities of the 6CA's become apparent to me are in the pronounced mid-range. They served up a nice throat at lower volumes and when pushed developed a nice honk to it especially in OD..FWIW For me this went both ways as I missed the sweeter more Fendery vibe on the clean channel although I really liked the throaty mids when in OD helped with the projection on my gigs.. You can decide!

These also had no lack of balanced high end content.... With the treble set on noon didn't find myself fiddling with the treble control to much as these I thought were pretty close to a 6L in this respect. Although at louder volumes and as the tubes started to break the tone was a bit crunchier (probably due to the larger plate structure) on the top end than the 6L's and noticeably more so than the older 6CA's I've used which became creamier. This to me was not so much a factor since I like to run my output section clean however those that do take notice..

With the fresh set of tubes and a plate current rating of 25 the tone overall was clear articulate with very little compression before breakup and a noticeable lack of wool or fuzziness vs the Sovetek 5881’s previous ,although this might change with age or a lower plate current rating..

Conclusions. Although these reminded me very little of the older soft vacuum 6CA7's they have their place in these amps.IMO.. Stout, tight open, and strident with an extended bandwidth than the usual 6CA7's..The pronounced midrange of these tubes for me are the deciding X factor along with the crunchier type breakup if you run your amps into output distortion. If you have any questions I'll try to answer

I really should post some clips showing the differences and perhaps in the future I will after the holidays..

HAPPY NEW YEARS TO ALL!!
Be Safe and watch the cops tonight..

Tony

[Structo]

Tony, thanks for the in depth review.

I am unfamiliar with this tube.

Is it more or less a beefed up EL34?

I see some data sheets that have both designations on them.

40 watt tube that can take 800v on the plates? Whoo Hoo!

Did you find they sounded best cold or hot biased?

Here is what Bob at Eurotubes has to say about this tube:

The JJ Big Bottle 6CA7 is another welcome addition to the already extensive line offered. It has the harmonic complexity of an EL34 in the upper mids and highs and the round low end of a 6L6 so it's as close to mixing an EL34 with a 6L6 in one bottle as you can get. We just loaded up Marshall DSL50 with a pair of these and and the first word that came to mind was "wooly". The low mids were FAT, and the high end sparkle was outstanding! These are a great "in-between" tube for the Peavey XXX and JSX amps as well as just about any other EL34 type amp such as Marshall, Laney and Mesa to name a few.

[David Root]

Tom, it's an American take on the EL34. Tonally it splits between the EL34 and the 6L6GC.

[jaysg]

My understanding is that the originals were close to a 6550 that met EL-34 specs. I had an HD-130 for a number of years and it wasn't the coolest amp cranked. It wasn't as satisfying as a Marshall and it wasn't quite the Fender/SRV thing either. It probably excelled just at breaking up.

[talbany]

If I had to quantify this tube in a short description I would say it's a pentode version of a Phillips 7581 w/ slightly wider plates and packed in a tighter envelope..Both sport dual halo's..
If your a fan of of the STR 415's/7581 and like mids you would perhaps dig this tube...


Hope this helps!!!

Tony

[PierreL]

Could those tubes be used instead of 6L6s in a Fuchs ODS ?

[tubedogsmith]

How was the pin size on them?

[talbany]

Could those tubes be used instead of 6L6s in a Fuchs ODS ?

Check with Andy

Here is the spec sheet for the JJ's...They put the plate dissapation rating same as the origional 6CA7's (25w) w/8 watt screen dissapation..I would bet my left nut this tube provides 40 watts easy.. I'll pull the scope and get back!!
Tony

How was the pin size on them

Pin size same as any other tube..

[BobW]

Tony, thank you for the JJ datasheet.

FWIW, EH was reluctant to send a datasheet when asked about their 6CA7 parameters when compared to the original Tung Sols and actually got quite pissy about it.

Apparently EH does not actually make those particular tubes, they just relabel them. Looks like I will be buying the JJs.

[talbany]

Tony, thank you for the JJ datasheet. 8)

FWIW, EH was reluctant to send a datasheet when asked about their 6CA7 parameters when compared to the original Tung Sols and actually got quite pissy about it. :roll:

Apparently EH does not actually make those particular tubes, they just relabel them. Looks like I will be buying the JJs.

Bob
Hope you are well and thanks for the low down on the EH's...Very interesting indeed..
I see the EH's have been getting mixed reviews out there and have a feeling the JJ's will as well as they circulate out, especially from those that try to compare these FAT bottles to that of an older style 6CA7 as these are for me very different..
To me the JJ's have always been a blue collar well built tough and rugged tube so I figured in the MM w/700V would be a better more reliable choice..So far they have worked out well..

Good Luck with them..

Tony

[renshen1957]

Tony, thanks for the in depth review.

I am unfamiliar with this tube.

Is it more or less a beefed up EL34?

Hi Structo,

The 6CA7 tube is essentially a North American take on the Mullard EL34, a beam tetrode (similar to a 6L6) with the beam forming plates replacing the suppressor grid (pinned out like an EL34 supressor grid) and a harder vacuum than the EL34.

The original version of the tube was more reliable than an EL34 and being native to North America, cheaper. It tends to sound like other beam tetrode (6L6, 6550, etc)

Traynor used them in his Bass master Amps after switching from 7027As when these became unavailable.

Best Regards,

Steve

[BobW]

I put a set of JJ 6CA7s in my Dynaco Mk III last night and used a #124 clone preamp. Although the removed KT88s are a bit dated, the 6CA7s have much more touch responsiveness and top end clarity. Am very happy with this change.