UA 175, or how much power can a 12BH7 stand ??
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CJ
Well-known member
Those tubes were used for vertical deflection in TV sets, so they are used to getting worked hard and long.
It looks like Putnam had the option of either adding on another stage like the 670-6V6, or work the tibe above it's ratings and save money/space.
Look at the load it is driving also. You guys are just talking about the dc operation.
It looks like Putnam had the option of either adding on another stage like the 670-6V6, or work the tibe above it's ratings and save money/space.
Look at the load it is driving also. You guys are just talking about the dc operation.
[quote author="cjenrick"]Those tubes were used for vertical deflection in TV sets, so they are used to getting worked hard and long.
It looks like Putnam had the option of either adding on another stage like the 670-6V6, or work the tibe above it's ratings and save money/space.
Look at the load it is driving also. You guys are just talking about the dc operation.[/quote]
I had asumed this was Class A operation - wouldn't the power inside the tube then be at its maximum with no signal?
(Not entirely sure about the transformer coupled case, but ...)
JH.
It looks like Putnam had the option of either adding on another stage like the 670-6V6, or work the tibe above it's ratings and save money/space.
Look at the load it is driving also. You guys are just talking about the dc operation.[/quote]
I had asumed this was Class A operation - wouldn't the power inside the tube then be at its maximum with no signal?
(Not entirely sure about the transformer coupled case, but ...)
JH.
[quote author="sismofyt"]No. Some seem to take more than others, but you can be sure it's going to shorten life. How much? Dunno, I'm only 29 :wink:
12BH7, 12B4A, 5687 and all of the 6J5/6SN7/7193/2C22 family are pretty strong, ime. ECC8X stuff is not and not very good sounding either. That is my highly biased opinion though
The schematic may very well be correct...[/quote]
Speaking of different / good / bad sounding tubes, I was curious and looked at the schematics of the famous Hammond B3 organ. Lots of different types in these.
But I found something I had not been aware of before: The B3 has a simple variable mu VCA, built from a 12AU7, for its percussion function!
Quite simple, no balancing trimmers at all - guess some hefty thumping is ok in _that_ application.
JH.
12BH7, 12B4A, 5687 and all of the 6J5/6SN7/7193/2C22 family are pretty strong, ime. ECC8X stuff is not and not very good sounding either. That is my highly biased opinion though
The schematic may very well be correct...[/quote]
Speaking of different / good / bad sounding tubes, I was curious and looked at the schematics of the famous Hammond B3 organ. Lots of different types in these.
But I found something I had not been aware of before: The B3 has a simple variable mu VCA, built from a 12AU7, for its percussion function!
Quite simple, no balancing trimmers at all - guess some hefty thumping is ok in _that_ application.
JH.
[quote author="soundguy"]Its been a while since I sat at a B3, but I wouldnt be suprised if it used the THUMP to create the persucssion voltage...
dave[/quote]
Well, it's a Gating (VCA operation) of either one of two drawbar signals, with an AD envelope. Fast Attack, two different Decay settings. A 330nF capacitor between the common cathodes of two 12AU7 halves, and the center tab of an interstage transformer that goes to the two grids. This cap is quickly charged thru a triode (forgot the number) that is connected as a diode (grid to plate), and discharged thru either one, or two resistors in parallel, for exponential decay. And there is quite some filtering in the percussion signal path. Thumping will certainly occur, but as a side effect.
JH.
dave[/quote]
Well, it's a Gating (VCA operation) of either one of two drawbar signals, with an AD envelope. Fast Attack, two different Decay settings. A 330nF capacitor between the common cathodes of two 12AU7 halves, and the center tab of an interstage transformer that goes to the two grids. This cap is quickly charged thru a triode (forgot the number) that is connected as a diode (grid to plate), and discharged thru either one, or two resistors in parallel, for exponential decay. And there is quite some filtering in the percussion signal path. Thumping will certainly occur, but as a side effect.
JH.
