View Full Version : NOS valves in a Croft preamp. A 'wow' moment!
Well, it is one of those rather rare 'wow' moments, when you do something, a small change, an adjustment, or anything and then out of the blue a major sound upgrade is achieved...
I've had this Croft SuperMicro II, which I purchased during my studies in the UK in 1989. When I purchased it after many auditions of equipment, I had the impression that the SuperMicro blew away all preamps at its price range and also many others costing many times as much. It was so open, transparent and convincing that I became a Croft fan ever since.
I have been listening to the SuperMicro with great pleasure, initially with a set of Musical Fidelity MA50 power amps (SS mono blocks, class A) and for many years afterwards paired with a Croft Series7. Almost one year ago, I had the preamp serviced by Glenn Croft and at the same time Glenn performed some upgrades, also bringing it to R-spec (R=regulated). That was a MAJOR upgrade! The sound became more composed, wider, tighter, with better imaging, deeper and yet more controlled bass. I was impressed (and very pleased, taking into account the cost-effectiveness of the upgrade).
Yesterday, a installed a pair of NOS Tesla E83CC in the phono stage of the SuperMicro. Nothing else. With only a few hours on the Tesla valves, two questions come to my mind:
1) Why had I never thought of this ever before? How can I have been missing this potential of the SuperMicro since 1989?
2) Why doesn't Glenn fit all his gear with high quality NOS valves? I am sure he is facing the hard reality of component cost, but then again there is so much more to be gained. Croft clients should be able to enjoy the full potential of the gear.
For the moment, I am getting much more detail than even before, with more resolution between instruments and voices but in a very relaxed manner. And the pace of the music is better. Yes, it is a cliche, but I am listening to records I've known all my life and I am discovering small things I never knew they existed on the record. The greatest improvement is on the realism of acoustic instruments and vocals. Buena Vista Social Club, Ella Fitzgerald, Neil Young, etc.
I hope my NOS Teslas will further improve, while breaking in. I will report again after 100h+.
In the meantime, the two further upgrades that I am planning for the SuperMicro are the following:
a) have the stock power supply upgraded to an external power supply (Glenn says it will give the sound more body and make it more lifelike. Can it be???)
b) substitute the stock GE 6463 valve of the line stage with an even better one. Any suggestions perhaps?
Phew, I had to get this 'out of my system' and share my upgrade experience. It was indeed one of those rare 'wow' moments. So gratifying...!
Hi Panos,
glad you have found the NOS Tesla ECC83's work well in your Croft preamp. I would use nothing else, they are simply superb especially the Tesla ECC83 32's
I have tried my Croft set up with the KEF LS50 speakers also and find it a great combination.
Now I must try some 7R mono's!
Firebottle
25-07-2016, 06:22
Hi Panos,
Great to hear you have opened up the sound of your Croft.
2) Why doesn't Glenn fit all his gear with high quality NOS valves? I am sure he is facing the hard reality of component cost, but then again there is so much more to be gained.
Yes, it is a cliche, but I am listening to records I've known all my life and I am discovering small things I never knew they existed on the record.
I believe Glenn fits the valves he does due to the uncertainty of supply of NOS valves, apart from the cost as you say.
It is so satisfying to hear more in well know recordings, just more enjoyment :)
:cool:
Hi Panos,
glad you have found the NOS Tesla ECC83's work well in your Croft preamp. I would use nothing else, they are simply superb especially the Tesla ECC83 32's
I have tried my Croft set up with the KEF LS50 speakers also and find it a great combination.
Now I must try some 7R mono's!
Yes, NOS Tesla E83CC sound great in the phono stage of the Croft SuperMicro preamp. Mine should be from the 60's. Now, I have to see whether I should try another NOS valve in the line stage (instead of the GE 6463 that's fitted).
Although I own the KEF LS50, IMHO they are NOT the ideal combination with the Croft amps (and in that system of mine I don't have the SuperMicro, but the Micro25R and a set of Series7R mono blocks). The KEFS are really difficult to drive and require the volume to be turned high, in order to perform better. Changing from the standard Series7 to 7R mono blocks allowed to get a better control on the KEFs, but still the synergy is not ideal, at least not in my ears -)).
Try and get hold of some Spendor SP2's they are simply stunning with the Croft, indeed Glenn used to use them regularly.
With regards to the Micro 25R I would recommend you have the line stage changed to the RS spec which is a 12BH7a valve with non inductive resistors. Takes some time to run in but benefits the whole preamp as the phono stage runs through this.
Hi James,
as a matter of fact, my Micro25R does have the line stage with the 12BH7A valve (a Synlavia one). It produces more realistic ('grown up' -)) sound than a ECC82. I will just need to replace the JJ ECC83S valves of the phono stage with a pair of NOS Tesla E83CC, like the ones I installed in my SuperMicro.
With respect to the speakers, I am thinking of changing the LS50 with a pair of Harbeth, probably the SHL5Plus. I wish I could go up to the M40.2, but I am afraid that the cost may be too high in comparison to what the SHL5Plus offers.
Try and get hold of some Spendor SP2's they are simply stunning with the Croft, indeed Glenn used to use them regularly.
With regards to the Micro 25R I would recommend you have the line stage changed to the RS spec which is a 12BH7a valve with non inductive resistors. Takes some time to run in but benefits the whole preamp as the phono stage runs through this.
I did not realise you had the 12BH7a line stage, good move in my opinion.
As the Harbeth SHl5 plus is a bit expensive I would consider the early SHL5, I recon they have better cones and are more musical than the radial material they build the new SHL5 from. Just my opinion but I heard an early ShL5 recently and it sounded very nice indeed.
Gents,
I would like to try some Tesla ECC83 32's in my Croft 25R, put have been put off so far due to not wanting to buy "fakes".
Could you please advise where you purchased yours from, or any good sources in the UK (not EBay) ?
I currently use new issue Genelex Gold Lions in the phono stage, Yellow print Sylvania 12BH7A in the linestage & Nos Mullards in the
power supply.
Thanks in advance
Oliver
Gents,
I would like to try some Tesla ECC83 32's in my Croft 25R, put have been put off so far due to not wanting to buy "fakes".
Could you please advise where you purchased yours from, or any good sources in the UK (not EBay) ?
I currently use new issue Genelex Gold Lions in the phono stage, Yellow print Sylvania 12BH7A in the linestage & Nos Mullards in the
power supply.
Thanks in advance
Oliver
Oliver, there is a chap called Mullardman who sells NOS Tesla ECC83,s on ebay. He is very reliable and good person to deal with. I have bought from him.
Hi Oliver,
I have purchased my NOS Tesla E83CC from Jac van de Walle in Germany. His website is http://www.jacmusic.com. It was a pleasure to do business with him, as he is a very knowledgeable guy.
Cheers,
Panos
Gents,
I would like to try some Tesla ECC83 32's in my Croft 25R, put have been put off so far due to not wanting to buy "fakes".
Could you please advise where you purchased yours from, or any good sources in the UK (not EBay) ?
I currently use new issue Genelex Gold Lions in the phono stage, Yellow print Sylvania 12BH7A in the linestage & Nos Mullards in the
power supply.
Thanks in advance
Oliver
Yep,
he is also a very reliable supplier of NOS valves and quite an authority on genuine vs fake valves.
Thanks Guys,
I have ordered a matched pair from Mullardman, will update (if ok with you Pankon ?) in this thread once received.
I think I will have to resist looking in on Aos for at least 3 months, it is hitting my pocket HARD :):D
At least my ears are enjoying the journey ;)
Now where did I hide my screwdriver to open the Croft ?
Oliver
Oliver,
please feel free to update this thread with your opinion about the valves you will install in your Croft preamp. Which valves will you be replacing? Standard JJ ECC83S?
Cheers,
Panos
Thanks Guys,
I have ordered a matched pair from Mullardman, will update (if ok with you Pankon ?) in this thread once received.
I think I will have to resist looking in on Aos for at least 3 months, it is hitting my pocket HARD :):D
At least my ears are enjoying the journey ;)
Now where did I hide my screwdriver to open the Croft ?
Oliver
The cream of the crop of the Teslas have cross sword markings.
TBH the yellow print ECC803S 32 is as good as the Telefunken ECC803S. I know as I owned both. The Teles cost a fortune, but I made money on them. They are no better IMHO, they sound almost exactly the same. Extremely close.
I have a quad of cross sword yellow print E88CC 32s and they are fantastic. Paid around £120 for them but they are getting scarce, so I'd expect more for those now.
The cream of the crop of the Teslas have cross sword markings.
TBH the yellow print ECC803S 32 is as good as the Telefunken ECC803S. I know as I owned both. The Teles cost a fortune, but I made money on them. They are no better IMHO, they sound almost exactly the same. Extremely close.
I have a quad of cross sword yellow print E88CC 32s and they are fantastic. Paid around £120 for them but they are getting scarce, so I'd expect more for those now.
Is that £120 for 4 or each valve? I may be interested in buying a pair off you.
By the way, Justin, are they NOS or used (simply Old Stock)?
Is that £120 for 4 or each valve? I may be interested in buying a pair off you.
No I am using them - none for sale! They were £120 for 4 and totally NOS.
Bear in mind they are E88CC cross sword, not E83CC.
You can find some cross swords on ebay - now.
When I said I'd expect more for them - I actually meant I'd expect them to cost more from someone commercial seller, if that was the misunderstanding.
http://www.ebay.co.uk/itm/2x-TESLA-E83CC-GOLD-12AX7-ECC803S-NEW-YELLOW-LABEL-SWORDS-MATCHED-from-70-s-/301925305656?hash=item464c268d38:g:mdIAAOSwsN9XCtJ W
My NOS Tesla were actually manufactured in August 1982, according to their marking on the glass (IH). Although not of the oldest Teslas, however the sound is magnificent. Perhaps it has to do with their frame grid construction, which -in the view of several experts- make a big difference.
In any case, they were a big improvement over my stock ECC83 valves (HRS and Ei).
Oliver,
please feel free to update this thread with your opinion about the valves you will install in your Croft preamp. Which valves will you be replacing? Standard JJ ECC83S?
Cheers,
Panos
I will be replacing new issue Genelex Gold Lion ECC83's.
In my system the JJ's seem to have higher gain (phono stage only) than all the valves I have swapped in (Mullard / TJ Full Music / & Genelex), could this be due to Glenn using these valves to voice the pre ?
Oliver,
IMHO, higher gain does not necessarily mean quality. Croft gear usually have quite high gain, so that even when you use valves with lower gain than the stock ones, you still end up with quite sufficient gain.
Based on my experience, there is quite a lot of potential in Croft amps that remains hidden because of the use of new issue valves instead of NOS. If you can find good NOS (say Tesla E83CC or other, depending on the type), it will be money well spent; every penny of it.
Cheers,
P.
I will be replacing new issue Genelex Gold Lion ECC83's.
In my system the JJ's seem to have higher gain (phono stage only) than all the valves I have swapped in (Mullard / TJ Full Music / & Genelex), could this be due to Glenn using these valves to voice the pre ?
Hi Pankon,
What i meant to say was "the JJ's sound more dynamic / punchy than the other valves", did you find that vs the Tesla's ?
Oliver,
As a matter of fact, the NOS Tesla E83CC are much clearer, detailed and composed than the JJ's. The dynamic / punchy sound that you mentioned may be due to less clarity perhaps?
Hi Pankon,
What i meant to say was "the JJ's sound more dynamic / punchy than the other valves", did you find that vs the Tesla's ?
I agree with you on this Panos the NOS Tesla valves are cleaner and clearer and more detailed than JJ,s by far, in fact they are one of the cleanest see through valves I have ever heard. They are so transparent with a clarity that reveals so much in the recording without much sonic imprint themselves.
I know valves all have their own characteristics, warm, detailed or rich but the Tesla's are probably the least valve like if you know what I mean. There is certainly no etched shrill top end to them as has been suggested of some ECC83 valves. In my system they give a big dynamic sound and really allow my speakers to sing.
I fully agree with you, James. Things are as you describe them. I think that instead of considering a rather costly upgrade to a new preamp (Croft or other), the most sensible and cost-effective approach is to replace the valves in the Croft pre with some NOS. In hi-fi terms they are much, much better that the JJ's that Glenn uses.
By the way, there is one thing to note: Tesla E83CC are frame grid type, whereas Tesla ECC803S are not, exactly the opposite from Telefunken. So, if one would like to go for the top-end Teslas, the E83CC are the ones to look for.
I agree with you on this Panos the NOS Tesla valves are cleaner and clearer and more detailed than JJ,s by far, in fact they are one of the cleanest see through valves I have ever heard. They are so transparent with a clarity that reveals so much in the recording without much sonic imprint themselves.
I know valves all have their own characteristics, warm, detailed or rich but the Tesla's are probably the least valve like if you know what I mean. There is certainly no etched shrill top end to them as has been suggested of some ECC83 valves. In my system they give a big dynamic sound and really allow my speakers to sing.
There are three valves in my croft integrated...
Would it be worth just swapping the one that is not the phono stage?
There are three valves in my croft integrated...
Would it be worth just swapping the one that is not the phono stage?
Phono stage valves make the biggest difference.
Yes, indeed! If you listen to records, of course -))
Phono stage valves make the biggest difference.
I have three NOS Tesla E83CC in the phono stage of my CJ ET3, and they are very good indeed. I think we need to introduce a little perspective - these valves will perform very well but we are talking about a reasonably subtle improvement if you comparing NOS to NOS (or new-new). We usually think they are very much better compared new to old, tired valves plus a big slice of expectation bias. Nice dimensionalality, and clean, neutral tone, with good detail are characteristics, but I have some Ei 12AX7 which are almost as good sounding and long lived too (if they survive initial burn-in/early life failure!)
Arkless Electronics
26-07-2016, 17:07
I have three NOS Tesla E83CC in the phono stage of my CJ ET3, and they are very good indeed. I think we need to introduce a little perspective - these valves will perform very well but we are talking about a reasonably subtle improvement if you comparing NOS to NOS (or new-new). We usually think they are very much better compared new to old, tired valves plus a big slice of expectation bias. Nice dimensionalality, and clean, neutral tone, with good detail are characteristics, but I have some Ei 12AX7 which are almost as good sounding and long lived too (if they survive initial burn-in/early life failure!)
Indeed Alex and a good point about the ageing aspect.
To add a little technical meat to the bones of this thread... much is likely to depend on the exact use to which a valve is put, its biasing, and also power supply voltages. Hence a valve which gives great subjective results in one amp may be not so good in another make or a different position. As far as gain goes well the gain of a triode (mu) is one aspect that is fairly well controlled in manufacture and for a ECC83 should be 100. Actual gain depends much on surrounding circuitry and mu is the maximum theoretically achievable from the valve itself. In the case of pre amps using negative feedback (the majority) the overall gain will be set by the feedback and only slightly effected by the choice of valve... there are some variants with a bit more than standard gain, usually intended for guitar amps in order to give more distortion/overdrive.
Hi Alex,
my Croft SuperMicroII (R-spec) had the initial stock valves since 1989 and until a few days ago, when I replaced the two phono ECC83 valves (NOS HRS and Ei) with NOS Tesla E83CC. Right from the start, the improvement was undeniable. And I hope it is going to become even bigger, as the Tesla valves break in.
I have three NOS Tesla E83CC in the phono stage of my CJ ET3, and they are very good indeed. I think we need to introduce a little perspective - these valves will perform very well but we are talking about a reasonably subtle improvement if you comparing NOS to NOS (or new-new). We usually think they are very much better compared new to old, tired valves plus a big slice of expectation bias. Nice dimensionalality, and clean, neutral tone, with good detail are characteristics, but I have some Ei 12AX7 which are almost as good sounding and long lived too (if they survive initial burn-in/early life failure!)
And because a picture is a thousand words, I am publishing a photo of my SuperMicro internals...
17605
Oliver,
out of curiosity, the NOS Teslas you have ordered are ECC83 or E83CC?
Thanks
P.
Thanks Guys,
I have ordered a matched pair from Mullardman, will update (if ok with you Pankon ?) in this thread once received.
I think I will have to resist looking in on Aos for at least 3 months, it is hitting my pocket HARD :):D
At least my ears are enjoying the journey ;)
Now where did I hide my screwdriver to open the Croft ?
Oliver
Oliver,
out of curiosity, the NOS Teslas you have ordered are ECC83 or E83CC?
Thanks
P.
Pankon,
They are E83CC, arrived yesterday evening :)
I will put them in later today (after I do my chores !!!!)
Oliver, I am sure you are going to enjoy your Tesla valves! They made a real difference in my preamp.
And if you find some time, it would be great to post one or two photos of your new valves.
Pankon,
They are E83CC, arrived yesterday evening :)
I will put them in later today (after I do my chores !!!!)
I bought my Tesla E83CC from Peter at Edicron, who was great to deal with and prices were quite reasonable. '33' factory code I believe too, which are the ones to have. They may still have some stock
Sent from my Nexus 7 using Tapatalk
So, any impressions, Oliver?
Any photos perhaps?
Enjoy!
Pankon,
They are E83CC, arrived yesterday evening :)
I will put them in later today (after I do my chores !!!!)
Oliver, I am sure you are going to enjoy your Tesla valves! They made a real difference in my preamp.
And if you find some time, it would be great to post one or two photos of your new valves.
Hi Pankon,
Before I put the Teslas in, I visually checked them vs the stock JJ's. The flasher is darker & the tops are flatter, which according to the Jac Music website denotes a proper Tesla valve. Mine shows "32" under the E83CC code, which tallies with James' description of his. I have only had a brief listen at low volume, but will check them out on Sunday.
I did have a listen for tube noise with the pre turned up to max & all good.
Oliver
Super! We will be waiting for your impressions.
P.
Hi Pankon,
...
I did have a listen for tube noise with the pre turned up to max & all good.
Oliver
Apart from the two ECC83 for the phono stage (which have now been occupied by the NOS Tesla E83CC), there are also three other valves, which according to Glenn also affect the phono stage. Namely they are:
1x GE 6463 83-22 33173
1x Sovtek 7025/12AX7WA 0810
1x English electric valve 7709 CV4048 KB/QG
I wonder whether anyone thinks I could upgrade any of the above-mentioned valves with NOS ones, which can make a difference. Any suggestions?
Cheers
Yes, beyond the 'techie' questions, comments and discussions, I have to say that when listening to Van Morrison's Caravan (from the 'In Concert' 1973 record) makes me rock my head, tap my feet, and sing along. Isn't that all what hi-fi is all about? Enjoying the music as if you were there...!
And yes, the NOS Tesla E83CC did play their part in plunging deeper into the music!
(Oops, Caravan just ended. Let's spin it once more -))
I had a brief 2 hr listen to the Teslas yesterday, and the diffs I could hear vs my 50+ hour Genalex tubes were subtle, mainly in the midrange. Having said that, I usually take a while to notice diffs when I make changes, (with the exception of Speakers) so will report back in the next few weeks.
My main concern when comparing kit is I am unsure if I am listening correctly, and what I should be focusing on (currently I listen for extra detail, or little subtle sounds not heard previously):scratch:
For Example I think the stock JJ's in my Croft sound good enough that I would have been happy to leave them in situ if I could not change them.
Maybe my listening levels are too low (peaking roughly 89db @ 2.5metres), or my speakers need rearranging ?
Hi Oliver,
thanks for the feedback. I guess you will need to give your NOS Teslas a few hours to break in and settle. Perhaps this may also allow you to appreciate any differences in the sound (good and bad ones).
For me, the differences of my NOS Tesla E83CC from the previous stock valves (NOS HRS and Ei ECC83) were immediate and quite positive. More clarity, detail, separation, fluidity, extension, but most importantly more realism. This is especially noticeable in vocals, which make you think that you have the artist in front of you.
Now, to ('reasonable') people who are not into hi-fi and its nuances, the differences I mentioned above may be barely noticeable, if at all. But the differences are indeed there, and it's not my imagination or wishful thinking -)).
I had a brief 2 hr listen to the Teslas yesterday, and the diffs I could hear vs my 50+ hour Genalex tubes were subtle, mainly in the midrange. Having said that, I usually take a while to notice diffs when I make changes, (with the exception of Speakers) so will report back in the next few weeks.
My main concern when comparing kit is I am unsure if I am listening correctly, and what I should be focusing on (currently I listen for extra detail, or little subtle sounds not heard previously):scratch:
For Example I think the stock JJ's in my Croft sound good enough that I would have been happy to leave them in situ if I could not change them.
Maybe my listening levels are too low (peaking roughly 89db @ 2.5metres), or my speakers need rearranging ?
The NOS Tesla E833CC in the phono stage of my Croft SuperMicroII-R have been a revelation for me. Now the question is what make of ECC83 to use in the regulation stage. Brimar? Tesla? Philips? Mullard?
Open to suggestions... -))
Thanks in advance!
My Tesla's now have 30+ hours use, they are indeed pretty special in my Croft. The main differences (vs my Genelex reissues) I have noticed are as follows:
Images appear more solid & in focus, (i.e Marvin Gaye was dead centre of my speakers when I played "Lets Get It On" and more "in the room" than before, in fact I could close my eyes & almost convince myself that he WAS in my room ) :)
Cymbals have more shimmer / decay, and I could hear subtle sounds deeper in the mix. In fact, I swear I thought I heard the studio door shutting during "Freddy Freeloader" from Kind Of Blue :eek:
The above differences were subtle, but has added to my musical enjoyment, which is the point of tube rolling in my book :D
I'm off know to see (hear) if Sade can tell me "your love is king" in my room :lolsign:
The NOS Tesla E833CC in the phono stage of my Croft SuperMicroII-R have been a revelation for me. Now the question is what make of ECC83 to use in the regulation stage. Brimar? Tesla? Philips? Mullard?
Open to suggestions... -))
Thanks in advance!
Pankon,
I use Nos Mullard ECC83's in my Croft pre, but have not listened to alternatives yet !
Oliver,
I fully confirm your comments. The Teslas offer more clarity and more detail, but in an organic manner, not because they are artificially boosting treble. They make records sound so more convincing. Impossible to go back to other, lesser valves in the phono stage...
My Tesla's now have 30+ hours use, they are indeed pretty special in my Croft. The main differences (vs my Genelex reissues) I have noticed are as follows:
Images appear more solid & in focus, (i.e Marvin Gaye was dead centre of my speakers when I played "Lets Get It On" and more "in the room" than before, in fact I could close my eyes & almost convince myself that he WAS in my room ) :)
Cymbals have more shimmer / decay, and I could hear subtle sounds deeper in the mix. In fact, I swear I thought I heard the studio door shutting during "Freddy Freeloader" from Kind Of Blue :eek:
The above differences were subtle, but has added to my musical enjoyment, which is the point of tube rolling in my book :D
I'm off know to see (hear) if Sade can tell me "your love is king" in my room :lolsign:
Well, the Tesla E83CC seem to be unbeatable in the phono stage of the Croft preamp. They are in their own league.
With respect to the ECC83 valve for the regulation, I've tried quite a several NOS alternatives, such as Philips JAN ECG, Brimar ECC83, Mullard ECC83, Mullard CV492. I think that the CV492 performed better than the rest, providing sufficient detail, but with fluidity and naturalness.
At the same time, I changed the stock JJECC83S of my Series7 amp with a Mullard CV492 and that made also significant overall improvement, providing more body and dynamics, as well as a bigger and more detailed soundstage.
I think I am getting there with my valve-rolling. I am quite happy with the result.
It is quite rewarding to be able to improve the sound of the existing amps just by changing one or more valves.
Hello pankon,
Which version of the E83CC you have on your preamp?
The frame grid version (code 37) or the NON frame grid one (code 32) ?
Has anybody tried the frame grid one ?
Hello pankon,
Which version of the E83CC you have on your preamp?
The frame grid version (code 37) or the NON frame grid one (code 32) ?
Has anybody tried the frame grid one ?
Hello pankon,
Which version of the E83CC you have on your preamp?
The frame grid version (code 37) or the NON frame grid one (code 32) ?
Has anybody tried the frame grid one ?
Hi Aris,
as far as I know, all Tesla E83CC are frame-grid type, irrespective to whether their code is 32 or 37. So, they should all be very, very good ones.
Cheers,
Panos
Hello pankon,
Which version of the E83CC you have on your preamp?
The frame grid version (code 37) or the NON frame grid one (code 32) ?
Has anybody tried the frame grid one ?
I have tried both and prefer the frame grid (37) version. The non frame grid are ok but not quite as good.
I have tried both and prefer the frame grid (37) version. The non frame grid are ok but not quite as good.
If I am not mistaken, the non-frame-grid Teslas are called ECC83 (in contrast to the frame-grid, which are called E83CC).
Thank you very much.
Not all the the E83CC are frame grid....as far as I know only the code 37 are frame grid...the code 32 (marked in yellow) are non frame grid...
Check at www.jacmusic.com under TUBES -> NOS TUBES-> TRIODES->ECC83 page
If I am not mistaken, the non-frame-grid Teslas are called ECC83 (in contrast to the frame-grid, which are called E83CC).
You're right pankon...Tesla E83CC code 32 and 37 are frame grid....my bad..
Its so confusing !!
This is E83CC code 32 framed grid : http://www.jacmusic.com/nos/images/ECC83/E83CC-TESLA-BOXES3.jpg
This is E83CC code 37 framed grid : http://www.jacmusic.com/nos/ECC83-part-numbering1.html Check the picture with the 8 tubes at about the middel of the page...its the third from left (tube nr.3)
Then there is this one too....E83CC code 32 yellow marked : http://vintageamps.com/plexiboard/viewtopic.php?f=13&t=51565 check post nr. 9, second picture...
Mr. de Walle of Jacmusic has on stock the 32 version with Crossed Sword and no gold pin...he say that they were bought by the military services. (the first link above).
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