12AX7 equivalents

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Tone Deaf

12AX7 equivalents
« on: 5 Nov 2003, 03:30 pm »
I've just read that ECC88/6DJ8 is an equivalent for (and less noisy than) 12AX7/ECC83, and so ideal for use in phono stages.  So far I can't find anything on the net to confirm.  
Are any more experienced old sages able to enlighten me please?

EDS_

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12AX7 equivalents
« Reply #1 on: 5 Nov 2003, 04:31 pm »
I hope this does not make things worse.....

I use Telefunken ECC-83, ECC-88 and Telefunken (Dynaco Labeled) smooth plate (12AX7) pretty often. These all work like magic in phono-stages.
The ECC-83 and ECC-88 don't offer the same stats or sound the same (They do sound similar but IMO the '88 offers slightly better bass and a tad less lush sound).
I will grant that the ECC-88 is quieter.

ECC-83
FV-6.3-12V
FC-300-150mA
PV-330V max.
PC-6mA max.
plate dissipation-1.1W max.

ECC-88
FV-6.3V
FC-365mA
PV-130V max.
PC- 25mA max.
plate Dissipation-1.8W max.

(I have this info. typed on a sheet--likely from Kevin Deal at Upscale Audio but I'm not sure of the source)------

IMO-either tube will work well in a phono-stage. If forced to pick-------I'd try the ECC-88 first---they are quieter.

Good luck.

randytsuch

12AX7 equivalents
« Reply #2 on: 6 Nov 2003, 05:38 am »
You might check out this page.
http://www.audioasylum.com/scripts/d.pl?audio/faq/joes-tubes.html

called joe's tube lore, it has a lot of info on 12ax7's.

In it, you will find you can use the 5751 tubes as a replacement for 12ax7's, and they are usually cheaper.  You only get about 70% of the gain with the 5751's, but I never had a problem with that.

Randy

hagtech

12AX7 equivalents
« Reply #3 on: 6 Nov 2003, 06:43 am »
The 6DJ8 is not very similar to a 12AX7 IMHO.  Way different specs, different pinout.  Both designed for different purposes.

That said, I agree, they both make excellent tubes for phono stages.  But you need different circuits to take advantage of their individual characteristics.  The 6DJ8 operates at much lower voltages and higher currents.  Less mu (voltage gain), but way more gm (transconductance gain).  It is a higher frequency tube designed to operate in cascode stages.

Really, both will give great results if used properly.  They are not, however, interchangeable.

jh :)

Tone Deaf

12AX7 equivalents
« Reply #4 on: 6 Nov 2003, 07:57 pm »
Thanks for the replies.  I think I'll stay away from ECC88's then.

I'm trying some NOS GE 5751's in my Cornet at the moment.  They seem quite a lot brighter so far, good with dark sludgy sounding records, but I'm favouring the 12AX7 for most things. (Remember tone controls, weren't they handy???)  Perhaps they'll settle in a bit as they get older

Question is, what to try next.  Look for some less bright 5751's or NOS 12AX7?

Wayne1

12AX7 equivalents
« Reply #5 on: 6 Nov 2003, 08:46 pm »
The Sovtech 12AX7LPS long plate spiral tubes are very nice sounding for a new tube. They can be found at a reasonable prices at various places.

Here is a link to one place: http://www.thetubestore.com/sovtek12ax7lps.html

The Tungrams NOS 12AX7 sounded wonderful in Marbles Cornet at VSAC. They do run about $35.00 each if and when you can find them.

The late 50's Mullard longplates are quite a catch getting upwards of $175.00 for a pair.

The early 60's Telefunken smoothplates are also in demand at over $70.00 a tube

You can have lots of fun looking over the listings of 12AX7 tubes here:
http://www.audiotubes.com/12ax7.htm#12ax7%20list

I have found the 12AU7 to be the most important tube in the Cornet for sound. I am now using a GE JG-5814 from the 50's that Larry Welch lent me. It is Fantastic!!

Using that tube with the Sovtek LPS and a CBS JAN CHY 5Y3WGTA really makes a nice combo with the tweaked Cornet.

tianguis

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Tube Rolling the Cornet
« Reply #6 on: 7 Nov 2003, 03:07 am »
Wayne:
      So, you still like that (not!) dusty ole tube? Me too. It's still the one I'm using.  I agree about the Tungsrams, also. Got in some from the Netherlands. Great dynamics and extension. The JAN CHY 5Y3WGTA is a great rectifier, but I've found a better one (I'm not gonna tell). And, yes, I've used all the Mullards.
     Since VSAC, playing with room EQ with the Behringer, (repositioning speakers, too) I'm able to hear far more into the details and nuances and make better-informed judgements about tubes.
      For "Tone Deaf",  there are many, many flavors of GE 5751's. Black plates, gray plates, double micas, triple micas, getter shapes. Their sonic sig differs from etched to detailed. Even among different years of identical construction, there are noticeable differences. I guess that's what makes this sport so enjoyable.

Regards,
Larry Welsh

Marbles

12AX7 equivalents
« Reply #7 on: 7 Nov 2003, 03:23 am »
I have Tungsrams as the 12AX7's
I have a GE as a rectifier (5Y3)

I ordered (tonight) a JAN GE 5814 for the 12AU7 I hope it works out well.

I will let you know.

This is who I ordered from

http://cgi.audiogon.com/cgi-bin/cl.pl?accstube&1072927110

Tone Deaf

12AX7 equivalents
« Reply #8 on: 11 Nov 2003, 12:35 pm »
Thanks for all the tips.  I changed 12AU7 first, as I had quite a few on hand for my line pre.   Each one I tried made a marked change, & I had settled on an old Mazda ECC82.

Changing from 12AX7 to 5751 also made an equally profound change to presentation.  Now after 30-40 hours' use they've broken in (either that or I've broken in to them!) and sound great, IMO a big improvement over the 12AX7's.  I've now changed the ECC82 for a mullard cv4003 box-anode thing, which has always given me problems in the past (microphonics & rolled-off highs when hot) in the Cornet & line stage.  With the 5751's in front of it, works perfectly.

One problem - there is a slight hum with the 5751's.  Not audible in use, but with vol turned up, there it is, begging to be worried about!  If I touch the 5751 glass, hum gets louder.  Touch both at the same time it gets really loud!  Touch glass of V1 with finger while thumb is on ground, hum completely disappears.  I'm wondering if the valves are faulty, or if my grounding is shoddy.  Any ideas?

Finally, I picked up a NOS rectifier tube for pennies at the local ham radio fest at the weekend, a mullard AZ31 from 1950's.  Checked it's spec on the net when I got it home, & it's a lighter duty device than the 5Y3, but still a direct heated FW tube & ok for power demands of the Cornet, so I thought I'd give it a try.  Works fine, & guess what?  It sounds different!!

hagtech

12AX7 equivalents
« Reply #9 on: 12 Nov 2003, 04:25 am »
Tone Deaf,

Nothing wrong with your tubes.  In fact, all front-end tubes will do that.  Just plain high impedance, high gain circuits with very small signal levels.  Can't help but pick up any stray electric field info.  That's why many phono stages (especially vintage) use the metal shield cans.  It's a very good thing to do for this circuit.

But hey, we like to see the tubes, too.  This is the one compromise I made for aesthetics.  Sonically, a properly implemented shield would be preferable.

So I did my best with layout and balance and proximity to minimize any stray hum pickup.  Distance is our friend.  The Trumpet fares even better because of the differential circuitry.

jh :)