12BH7A valve. Impressions? Insights?

[pankon]

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
IMG_1888.jpg

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]

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.

[Jimbo]

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]

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]

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?

[pankon]

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]

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.

[pankon]

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).

[eksiil]

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.

[pankon]

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