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12BH7 preamplifier

arts said:
Apologies for the misinformation. I absolutely remember some similar looking audio gear being manufactured in BC around the1980's, and I thought this was one of them.
Oops :(
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Any help is appreciated! Lee’s Electronics in Vancouver offered project kits in the 80s-90s. I had no idea there was a Korean Lee’s Labs that produced tube gear. Learn something new everyday ☺️
 
fxer1982 said:
you replyed with the location, title and the web site name...... web site...... ALIEXPRESS WiKi 12au7 VS 12BH7:a practical comparison for Audiophiles and DIY Enthusisasts.
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@fxer1982, I have not replied with anything - just quoted what you wrote.

Has anyone been able to decipher this? What is the link?
 
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Here is Google’s view on 12AU7 and 12BH7

“The 12AU7 and 12BH7 are both dual-triode vacuum tubes with the same medium amplification factor (μ = 20), meaning they have similar gain on paper, but they differ significantly in physical size, power handling, and electrical requirements.

Key Electrical & Physical Differences
    • Gain / Amplification Factor (μ): Both share an amplification factor of ~20, though the 12BH7 can yield slightly higher actual gain in certain anode resistor circuits due to lower plate resistance. [1, 2]
    • Heater Power & Current Draw:
      • 12AU7: Draws less heater current (around 2W heater power).
      • 12BH7: A physically larger, beefier tube that draws significantly more heater and high-tension (plate) current (around 4W heater power—roughly double the current). [1, 2]
    • Plate Dissipation:
      • 12AU7: Rated at 2.7W max plate dissipation per section (max plate voltage ~300V, max current ~20mA).
      • 12BH7: Rated at 3.5W (or higher) per section, designed to handle more muscle and act as a driver tube or small power output tube. [1]
    • Plate Resistance:
      • 12AU7: ~7,700 ohms
      • 12BH7: ~5,300 ohms (lower plate resistance)”
 
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You know... I have heard units with 12BH7 in the gain stage and others with 12AU7, though not in the same amp.

The typical (read: Sylvania, in my case) 12BH7 has a different tone. It has a very nice, deep bass. Good headroom. Very good dynamics.

The typical 12AU7 sounds tilted toward the high end and kind of weak in the low end. It’s just not an exciting tube to listen to.

If I were to build a DIY and had to choose between the two, I’d prolly go with the 12BH7. The only issue is the tube’s availability. I have not heard the EH 12BH7.

One good thing. I have had good luck with NOS Sylvanias and their long life. :idea:
 
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spantou01 said:
That is a nice summery of the basics; basics that are well known. I thought @fxer1982 had something interesting to offer, an article that I have not seen.
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i added a link and i tried it. took me right to the articular so just a minute ago i did a link again, no nothing WTH. its done by a builder of high end pre amps and what he found in his changes of going to the 12bh7 vs 12 au7. what the hell it was a great write up with pertinent info for DIY or High end builders. i tried it today didnt work did a link again it worked then i come back and the link wont work. WPMO sorry guys and gails.
 
knotscott said:
My VTA/Dyna 70s use 12BH7a as a driver tube in place of a 12AU7, and definitely prefer the 12BH7a....especially the NOS Tung Sols I put in a few weeks ago. Never saw one in a preamp before.
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I believe Ludwell wrote that the 12BH7 was originally designed for vertical-sweep amplifier circuits in TVs. That’s probably why they weren’t initially used in audio circuits. Certainly not in the 1950s — except for McIntosh. :)

BTW.... the 12BH7A is a nice variant. Slow heater warm-up. :thumbsup:
 
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right from the Tung Sol datasheet

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vertical sweep in a TV is not very different from an audio amp so the tubes end up being perfectly usable for both. Its basicaly a single ended amp that can run up to a couple watts of output, depending on the size of the CRT.
 
indeed. The "cow bile machine" transformers I bought for my AMP-197 are surprisingly not bad, though I still have no idea what cow bile has to do with anything.

I'm also not necessarily completely allergic to cheap import stuff, I just don't put much stock in what the ad copy has to say.
 
gadget73 said:
indeed. The "cow bile machine" transformers I bought for my AMP-197 are surprisingly not bad, though I still have no idea what cow bile has to do with anything.

I'm also not necessarily completely allergic to cheap import stuff, I just don't put much stock in what the ad copy has to say.
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I was about to order a couple 5K/8 ohm 10w "cow bile machines" until I saw the shipping charge.
 
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