View Full Version : 12BH7A valve. Impressions? Insights?
I came across the 12BH7A valve for the first time, when I recently received my upgraded Croft Micro25R preamp (used in the line stage) and my Croft Series7R monoblocks.
Unfortunately the Sylvania 12BH7A (green lettering) of my preamp had a serious deficiency in the treble (roll-off), that led me to believe that it must have obviously been a faulty one. Currently I am using a Philips 12AU7 instead, which is quite good, but does not have such a full body in comparison to the 12BH7A. So I am looking for a substitute 12BH7A NOS valve to do justice to my Croft preamp.
Anyone with experience with 12BH7A valves? Which models are worth going for? Where could I find a good source for such valves? Is there perhaps a compatible substitute for 12BH7A valves, that is also worth considering?
Thanks in advance for any information.
Cheers,
Panos
Hi Panos,
I currently use a NOS Sylvania 12BH7A (yellow writing) in my 25, no problems with reduced treble, and prefer it to NOS Mullard, new issue Genalex ECC82, and supplied Sylvania 5814WA. I would say that the differences between these valves were not "night & day" but I felt that the 12BH7A gave a tad more depth, and a slightly more robust (firmer in the bass) sound.
When I asked my Croft dealer if the 12BH7A would be ok in my non regulated 25, & about the general sound of the different brands, his answer was "Tungsol warmest, GE brightest and Sylvania in middle", so I went for the Sylvania.
Having said this, I could happily live with any of the above valves, as none of them made the pre sound bad :)
Good luck tube rolling :)
Oliver
Hi Oliver,
thanks for your input. You said your pre is a Micro25, not a Micro25R. In its previous guise (before the upgrade), my Micro25 used to have an ECC82 valve for the line stage, not a 12BH7A.
In any case, my limited impression with the Sylvania 12BH7A is that it definitely has a 'bigger' sound, perhaps even sweeter than an ECC82 (or 12AU7).
Glenn Croft said that Tung Sol and RCA 12BH7A are good.
I have found a rather inexpensive version (obviously not NOS), which is https://www.tubesandmore.com/products/T-12BH7A-TAD. I may perhaps give it a try...
I have a NOS Tung-sol 12BH7a on the way for my 25R+ line stage which will replace the RCA valve I have in there at the moment.
Will be interesting to hear the difference!:)
I have a NOS Tung-sol 12BH7a on the way for my 25R+ line stage which will replace the RCA valve I have in there at the moment.
Will be interesting to hear the difference!:)
James, I would definitely be interested in hearing your impression. Have you tried any other 12BH7A apart from the NOS RCA? Is there a particular reason you would like to change to Tung-Sol?
James, I would definitely be interested in hearing your impression. Have you tried any other 12BH7A apart from the NOS RCA? Is there a particular reason you would like to change to Tung-Sol?
I have tried a number of 12BH7A valves including my current NOS RCA which has been the best. I have a NOS GE which was a bit lightweight and airy. I has a modern JJ 12BH7a equivalent which was terrible. The RCA has good detail, soundstage and weight. I would very much recommend one of these in the line stage of the 25R but not in the input stage of the Series 7 power amp. It does not perform well there at all!
I am trying a NOS Tung -Sol in the line stage as I have it on good authority that this will give even more weight and dynamics to the sound but I will let you know as nothing has impressed me more than the NOS RCA.
One thing to remember with valve rolling is that the particular character a certain make of valve has is rather general but the period when that valve was manufactured is probably more important. Notice I only refer to NOS valves. The older you can get the better especially if you can get one from the 1950's or early 60's.
I have done a lot of tube rolling with ECC83's and the best have always been the earlier ones. Search hard and you pay more but if you can find a reputable seller the rewards with these earlier valves is definitely worth paying for.
I have tried a number of 12BH7A valves including my current NOS RCA which has been the best. I have a NOS GE which was a bit lightweight and airy. I has a modern JJ 12BH7a equivalent which was terrible. The RCA has good detail, soundstage and weight. I would very much recommend one of these in the line stage of the 25R but not in the input stage of the Series 7 power amp. It does not perform well there at all!
Yes, soundstage and weight are definitely qualities that I also recognized with the Sylvania 12BH7A of my Micro25R. No great detail though, probably due to the treble roll-off that I had detected. The 12BH7A sounds more 'grown-up', authoritative and confident than a 12AU7 (ECC82).
I am trying a NOS Tung -Sol in the line stage as I have it on good authority that this will give even more weight and dynamics to the sound but I will let you know as nothing has impressed me more than the NOS RCA.
One thing to remember with valve rolling is that the particular character a certain make of valve has is rather general but the period when that valve was manufactured is probably more important. Notice I only refer to NOS valves. The older you can get the better especially if you can get one from the 1950's or early 60's.
I have done a lot of tube rolling with ECC83's and the best have always been the earlier ones. Search hard and you pay more but if you can find a reputable seller the rewards with these earlier valves is definitely worth paying for.
Any indications about the cost of the RCA and Tung-Sol NOS 12BH7A?
Yes, soundstage and weight are definitely qualities that I also recognized with the Sylvania 12BH7A of my Micro25R. No great detail though, probably due to the treble roll-off that I had detected. The 12BH7A sounds more 'grown-up', authoritative and confident than a 12AU7
Any indications about the cost of the RCA and Tung-Sol NOS 12BH7A?
Expect to pay anything between $50-$100 for a good NOS 12BH7a. The American tube sellers have the best price and choices on these tubes. I would not buy from eBay!
[QUOTE=pankon;735919]Hi Oliver,
thanks for your input. You said your pre is a Micro25, not a Micro25R. In its previous guise (before the upgrade), my Micro25 used to have an ECC82 valve for the line stage, not a 12BH7A.
Yes, my pre is not the 25R, but was told that the extra current requirements of the 12BH7A would not be a problem in my pre.
I intend getting mine upgraded to "R" status later this year, & I will ask Glenn to configure the linestage for a 12BH7A (as suggested by Jimbo in a previous thread).
http://i1101.photobucket.com/albums/g436/User_211/tubes_zpsm0hxqnsx.jpg
Above are some valves I sold with my Air Tight ATM2. So I did a few as you can see.
I reckon the best were the RCA long black plates from 1966 right next to the white boxes on the right.
Top left mid-70s Mexican RCA are good but not as good.
The black plates really are close to black with a kind of glossy sheen to them.
The Zaerix branded ones where also pretty damned OK I see to remember.
Actually I may have some 12BH7A somewhere if anyone is interested give me a shout but it'll just be at market rates.
Arkless Electronics
02-03-2016, 01:35
ECC82 does have a bad reputation sound quality wise.... no matter what make ;)
Funnily enough I've not found NOS to be unequivocally better in small signal valves. More that particular circuits seem to sound better with certain valves, whether NOS or modern Russian.
http://i1101.photobucket.com/albums/g436/User_211/tubes_zpsm0hxqnsx.jpg
Above are some valves I sold with my Air Tight ATM2. So I did a few as you can see.
...
That's a pretty interesting collection of valves. :)
http://i1101.photobucket.com/albums/g436/User_211/tubes_zpsm0hxqnsx.jpg
Above are some valves I sold with my Air Tight ATM2. So I did a few as you can see.
I reckon the best were the RCA long black plates from 1966 right next to the white boxes on the right.
Top left mid-70s Mexican RCA are good but not as good.
The black plates really are close to black with a kind of glossy sheen to them.
The Zaerix branded ones where also pretty damned OK I see to remember.
You wouldn't happen to have any RCA 12BH7a valves you want to sell Justin?
That's a pretty interesting collection of valves. :)
The RCA clear tops looked cool but sonically they were a disaster in said amp. But yeah, I went a bit 12BH7A crazy...:D It was an xxpensive amp - need to get the best out of it.
Expensive though they are it got systematically trashed by the Austria Analogue 211 based monos I got aftwerwards.
You wouldn't happen to have any RCA 12BH7a valves you want to sell Justin?
I'll have a look this weekend James. Got a big bag of allsorts I looked at a few months ago and I am sure there is something 12BH7A in there - maybe not RCA though. I'll PM you with what I find.
ECC82's not much sonic cop? Not sure I can agree with that one, but my own first Croft came with beefed up CV mil spec versions so I stuck to those with the current one. Aren't the gains slightly different too - ECC82's and 12BH7's? Since the preamps have slightly too high output for their power amps (volume controls squashed to the first third of their rotation from minimum for a loud playback volume), I'd have considered a lower gain line-stage valve a blessing, so you could use far more of the volume control without being deafened with it set less way than half way up.
I thought the 12BH7 had more demanding characteristics and wasn't entirely suitable for some preamps with simpler power supplies set up for the ECC82. Oh to really know what I'm on about here and a shame Glenn won't waste his time chatting on audio forums...
To gauge why he uses the valves he does in a particular design. I think you only need to email him and you'll get a polite and considered reply in return. He knows his designs backwards and will give chapter and verse if necessary I reckon :)
anthonyTD
02-03-2016, 11:50
Hi All,
I have a small stock of original, boxed [orange and black] Brimar, Black plate 12BH7's.
A...
Arkless Electronics
02-03-2016, 19:28
ECC82's not much sonic cop? Not sure I can agree with that one, but my own first Croft came with beefed up CV mil spec versions so I stuck to those with the current one. Aren't the gains slightly different too - ECC82's and 12BH7's? Since the preamps have slightly too high output for their power amps (volume controls squashed to the first third of their rotation from minimum for a loud playback volume), I'd have considered a lower gain line-stage valve a blessing, so you could use far more of the volume control without being deafened with it set less way than half way up.
I thought the 12BH7 had more demanding characteristics and wasn't entirely suitable for some preamps with simpler power supplies set up for the ECC82. Oh to really know what I'm on about here and a shame Glenn won't waste his time chatting on audio forums...
To gauge why he uses the valves he does in a particular design. I think you only need to email him and you'll get a polite and considered reply in return. He knows his designs backwards and will give chapter and verse if necessary I reckon :)
That's what the general consensus is but it will probably vary with use.... and all too often things are "the general consensus" on fora without there being even a jot of truth to it! ;)
That's what the general consensus is but it will probably vary with use.... and all too often things are "the general consensus" on fora without there being even a jot of truth to it! ;)
My personal, short experience with a 12BH7A (Sylvania with green lettering) is that is sounds fuller and more refined than the 12AU7 (or ECC82). I cannot compare detail reproduction, as my 12BH7A was seriously hampered by treble roll-off, so any deduction may not be reliable.
Starting from the Sylvania 12BH7A with the green lettering, I tried a few other 12BH7A alternatives (see enclosed photo) in my Micro25R, driving two Series7R monoblocks.
Top row (left to right): Tung-Sol short black plate, Tung-Sol short black plate, Tung-Sol short black plate, Sylvania long short gray plate
Bottom row (left to right): Raytheon short gray plate, Raytheon short gray plate, RCA long gray plate, Westinghouse short gray plate
18079
Sonically, I detected similarities in relation to the length of the plate, i.e. the long plates sounded similar with each other, and so did the short plates (which I preferred).
Overall, I personally preferred the Westinghouse, which presented very good imaging, clear instrument separation, full body and deep, well-controlled bass.
Second (slightly behind) was the Raytheon, which was similar to the Westinghouse, with perhaps slightly more fluidity and slightly less body.
Any opinions from fellow forum members?
Sondekker
21-09-2016, 17:21
Those findings are rather interesting.
I too have a 25R modified by Glenn to use a 12BH7 in the line stage which has been up for sale here and elsewhere for around 3 months without success. Glenn originally fitted an unbranded 12BH7 and when I decided I'd like to try a different version I picked up that Glenn rather liked Westinghouse versions.
I bought a pair of NOS 1958 black plate D getter valves and fitted one in the 25R. The results were very positive in comparison with the unbranded version it replaced, however, I have never tried any other versions of the 12BH7 and so my own experiences are rather limited.
I have also been advertising the other unused Westinghouse valve here (also without success) if anyone wants to try one.
Those findings are rather interesting.
I too have a 25R modified by Glenn to use a 12BH7 in the line stage which has been up for sale here and elsewhere for around 3 months without success. Glenn originally fitted an unbranded 12BH7 and when I decided I'd like to try a different version I picked up that Glenn rather liked Westinghouse versions.
I bought a pair of NOS 1958 black plate D getter valves and fitted one in the 25R. The results were very positive in comparison with the unbranded version it replaced, however, I have never tried any other versions of the 12BH7 and so my own experiences are rather limited.
I have also been advertising the other unused Westinghouse valve here (also without success) if anyone wants to try one.
Hi John, I will have it. Sent you a PM.:)
Arkless Electronics
21-09-2016, 18:18
Bear in mind folks that when "tube rolling" all is not as it may seem.... Whilst there are undoubtedly differences in the sound of valves of the same type but different make etc, much will also be due to the way that a specific sample reacts to the circuitry around it! A given stage of an amplifier may exhibit lets say 0.05% distortion with one sample of valve but a different sample may result in 0.5% distortion and the distortion may be of a different blend of odd and even harmonics to the first one. Hence sound will be different.
Although mainly irrelevant to most users, changing say the cathode resistor value to suit a particular sample of valve may totally change the measured performance and sound of the stage;)
CornishPasty
29-09-2016, 20:40
I built a phono stage based on the 834P but with Thorsten's mods which includes using an ECC82 for the output buffer stage instead of the usual ECC83. After reading through this thread I'm wondering if a 12BH7 would offer any improvement over the ECC82?
Ralph,
I have no knowledge on circuit design. However, from experience, what I can say is that the 12BH7A is cleaner, more robust (with more body) and smoother sounding valve than the ECC82. And it seems that there is a general consensus in favor of the 12BH7A.
You just have to take note that from what I've read the 12BH7A draws twice as much current that the ECC82, so that should be probably taken into account if you are considering a swap.
I built a phono stage based on the 834P but with Thorsten's mods which includes using an ECC82 for the output buffer stage instead of the usual ECC83. After reading through this thread I'm wondering if a 12BH7 would offer any improvement over the ECC82?
CornishPasty
30-09-2016, 16:37
Thanks Panos. The transformer in my phono stage has a 4 amp heater winding so will be fine. If I have a 12BH7 in my valve collection I'll give it a go.
Thanks Panos. The transformer in my phono stage has a 4 amp heater winding so will be fine. If I have a 12BH7 in my valve collection I'll give it a go.
Ralph, it will be interesting to hear about your findings, once you've tried a 12BH7A (or more).
I'm very happy with NOS (1950s I think) black plate Tung-Sols in my overhauled (2015) Mega Micro II & similar age Sylvanias in the 7R monos. I was told by Glenn Croft to go for US 12bh7a-s.
I'm very happy with NOS (1950s I think) black plate Tung-Sols in my overhauled (2015) Mega Micro II & similar age Sylvanias in the 7R monos. I was told by Glenn Croft to go for US 12bh7a-s.
Hi ahto,
thanks for your input. Would it be too much to ask for a few photos of the valves you have installed, if that's not too difficult? What's the color of the Sylvania marking?
I'll PM you yo ask something else as well.
Thanks
Panos
The Westinghouse 12BH7a is very very good and has given a touch more weight to the sound. It is however only equal to my long plate grey RCA 12BH7a which has been a long term favourite. The Westinghouse is definitely one I will keep in my armoury and indeed it will be staying in the 25R+ for some time yet.
If I were to ultimately replace the RCA long plate I would buy an older version -this valve has it all!
On another matter I am currently using a GE 5751 in the input stage of the Series 7 power amp but have considered again an older version of this tube as the current JAN version is probably not the best?
The Westinghouse 12BH7a is very very good and has given a touch more weight to the sound. It is however only equal to my long plate grey RCA 12BH7a which has been a long term favourite. The Westinghouse is definitely one I will keep in my armoury and indeed it will be staying in the 25R+ for some time yet.
If it were to ultimately replace the RCA long plate I would buy an older version -this valve has it all!
On another matter I am currently using a GE 5751 in the input stage of the Series 7 power amp but have considered again an older version of this tube as the current JAN version is probably not the best?
James,
yes, I was also very pleasantly surprised by the Westinghouse 12BH7A. If I understand correctly, it is quite likely to have been manufactured by GE.
With respect to the input stage of the Series7, I am using a Mullard CV492 (military spec ECC83). I was very impressed by the CV492. It's much tighter, cleaner, with more body and better imaging than the stock JJ ECC83. If you can, you should try one (it's not a very easy find).
Cheers,
Panos
no worries, I'll see what I can do either tonight or tomorrow.
James,
yes, I was also very pleasantly surprised by the Westinghouse 12BH7A. If I understand correctly, it is quite likely to have been manufactured by GE.
With respect to the input stage of the Series7, I am using a Mullard CV492 (military spec ECC83). I was very impressed by the CV492. It's much tighter, cleaner, with more body and better imaging than the stock JJ ECC83. If you can, you should try one (it's not a very easy find).
Cheers,
Panos
Thanks for the recommendation Panos I will look out for one.
OK, here's an attempt at posting a pic of the Mega Micro business end innards, featuring the Tung-Sol 12BH7As
https://www.dropbox.com/s/53vcf76ze0fkn71/WP_20160412_14_41_01_Pro.jpg?dl=0
OK, here's an attempt at posting a pic of the Mega Micro business end innards, featuring the Tung-Sol 12BH7As
https://www.dropbox.com/s/53vcf76ze0fkn71/WP_20160412_14_41_01_Pro.jpg?dl=0
Great! Thanks for the photo, Ahto. Classical Croft design. Below you can find a photo of my SuperMicroII. You will notice the similarity... However, my SuperMicroII does not use 12BH7A, but a 6463 (from GE) instead. You will also notice the two Tesla E83CC at the far left. You can also see the small PCB, which was added when Glenn brought the preamp in R-spec (regulation).
The 12BH7A is used in the line stage of my Micro25R, which is a more modern (recent) design.
https://www.dropbox.com/s/qqcjxqkkumswwvt/SuperMicroII_NOS_TeslaE83CC.jpg?dl=0
The Westinghouse 12BH7a is very very good and has given a touch more weight to the sound. It is however only equal to my long plate grey RCA 12BH7a which has been a long term favourite. The Westinghouse is definitely one I will keep in my armoury and indeed it will be staying in the 25R+ for some time yet.
If I were to ultimately replace the RCA long plate I would buy an older version -this valve has it all!
On another matter I am currently using a GE 5751 in the input stage of the Series 7 power amp but have considered again an older version of this tube as the current JAN version is probably not the best?
James, can I please ask you where you purchased your RCA 12BH7A long grey plate from? And if you remember the cost...?
I do not know why, but from the various 12BH7A I've tried, I tend to prefer the ones with short plates. Coincidence? Maybe or maybe not...(?)
Cheers,
P.
James, can I please ask you where you purchased your RCA 12BH7A long grey plate from? And if you remember the cost...?
I do not know why, but from the various 12BH7A I've tried, I tend to pretend the ones with short plates. Coincidence? Maybe or maybe not...(?)
Cheers,
P.
Hi Panos, sorry I did not buy the RCA valve, it was given to me. I would consider the late 50's or 60's long plate versions if you can find a seller on the net. The best ones are in America. Massive choice there.
Hi Panos, sorry I did not buy the RCA valve, it was given to me. I would consider the late 50's or 60's long plate versions if you can find a seller on the net. The best ones are in America. Massive choice there.
Yes, James, I will definitely have a look across the Atlantic. They seem to have many 12BH7As over there. It's a pity we cannot try before buying. It's an expensive game to try to find the right one(s) and put the rest aside.
the Mega Micro's line stage was updated (among other things) in 2015. I don't actually know what was in there before, I had the seller ship it straight to Glenn Croft. I suspect the 12BH7As came with the overhaul (I sank £500 into it). He says it is now better than a 25R -- some of which presumably has to do with the 12 valves in the power supply unit & the four-way HT regulation... . though given the different topologies etc any comparisons with later models evoke apples & oranges.
the Mega Micro's line stage was updated (among other things) in 2015. I don't actually know what was in there before, I had the seller ship it straight to Glenn Croft. I suspect the 12BH7As came with the overhaul (I sank £500 into it). He says it is now better than a 25R -- some of which presumably has to do with the 12 valves in the power supply unit & the four-way HT regulation... . though given the different topologies etc any comparisons with later models evoke apples & oranges.
Can you kindly post some pics of the mega micro internals?
having just got the hang of Photobucket I might as well replace this post with proper pics of the insides of the two Mega Micro II boxes.
the preamp:
http://i1243.photobucket.com/albums/gg560/eksiil/WP_20160412_14_41_01_Pro.jpg (http://s1243.photobucket.com/user/eksiil/media/WP_20160412_14_41_01_Pro.jpg.html)
the PSU:
http://i1243.photobucket.com/albums/gg560/eksiil/IMG_0124.jpg (http://s1243.photobucket.com/user/eksiil/media/IMG_0124.jpg.html)
some of the PSU valves slantwise:
http://i1243.photobucket.com/albums/gg560/eksiil/IMG_0125.jpg (http://s1243.photobucket.com/user/eksiil/media/IMG_0125.jpg.html)
having just got the hang of Photobucket I might as well replace this post with proper pics of the insides of the two Mega Micro II boxes.
the preamp:
http://i1243.photobucket.com/albums/gg560/eksiil/WP_20160412_14_41_01_Pro.jpg (http://s1243.photobucket.com/user/eksiil/media/WP_20160412_14_41_01_Pro.jpg.html)
the PSU:
http://i1243.photobucket.com/albums/gg560/eksiil/IMG_0124.jpg (http://s1243.photobucket.com/user/eksiil/media/IMG_0124.jpg.html)
some of the PSU valves slantwise:
http://i1243.photobucket.com/albums/gg560/eksiil/IMG_0125.jpg (http://s1243.photobucket.com/user/eksiil/media/IMG_0125.jpg.html)
Wow, so many valves in the PSU box!
I wonder whether you've ever considered asking Glenn to move the transformers to a separate box, like he does with the Micro25RS... I do not know whether that would yield a worthwhile improvement, at least one that would justify the cost.
Wow, so many valves in the PSU box!
I wonder whether you've ever considered asking Glenn to move the transformers to a separate box, like he does with the Micro25RS... I do not know whether that would yield a worthwhile improvement, at least one that would justify the cost.
the transformers are in a separate box. box no. 1 contains the 5 preamp valves. box no. 2 has the 12 regulator valves in the PSU. or do you mean a 3rd box?
the transformers are in a separate box. box no. 1 contains the 5 preamp valves. box no. 2 has the 12 regulator valves in the PSU. or do you mean a 3rd box?
Yes, Ahto, as a matter of fact, I was referring to a third box, which would completely isolate the transformers. It seems that you're not far from a no-compromise solution, so I am suggesting of some (theoretical?) further improvements, irrespective of cost. And perhaps you could also consider changing the Trigon ECC83 with something better (again theoretically...).
Just my two pence -)
I don't think Croft has ever gone as far as three boxes. would it make practical sense? I must profess utter cluelessness here. it's an interesting thought though, thanks.
the Trigons remain as much an affectation (Indian Mullards, after all) as an imposition till I can justify the cost of something better.
Yes, Ahto, as a matter of fact, I was referring to a third box, which would completely isolate the transformers. It seems that you're not far from a no-compromise solution, so I am suggesting of some (theoretical?) further improvements, irrespective of cost. And perhaps you could also consider changing the Trigon ECC83 with something better (again theoretically...).
Just my two pence -)
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