You may have seen my other thread about my modified Baldwin tube amp. It's an old mono electronic organ amp that was converted over to stereo operation by a gentleman named Will Vincent. He sells many modded Baldwin amps as well as modded Dynaco ST-70 amps.
At any rate, this amp uses two 5U4GB rectifier tubes. I assume it was designed this way to provide ample current and output on demand without "sagging" when full organ was required. It proves to be a very solid design as this amp effortlessly powers my inefficient NHT 2.9's (86dB @ 1w/1m) with ease. Bass attack is extremely tight and punchy. Even my old Technics SU-8099 amp with its 115w per channel didn't provide this kind of controlled bass.
Anyway, I've been doing some brief reading around the forum about the 5U4 tubes and rumor has it they heat up very quick and throw B+ to the output tubes way before they are heated up properly to receive that voltage. Apparently that can cause damage to the output tubes and I'm sure the driver tubes as well.
I also read that the 5U4's are known for sparking or "spark out" as TubeLab calls it. What's curious about his statement ( http://www.diyaudio.com/forums/tubelab/129396-rectifier-tube-5ar4-vs-5u4gb.html ) in this link is that these 5U4's did this with 47uF caps which is what I'm using in my amp, FOUR of them in fact, all rated at 450v. That really concerns me!
Now I haven't noticed any sparking of any kind when I power up this amp and maybe it doesn't because there's twice as much draw being there's two 5U4's there. However I do notice that the filaments in the 6L6's are glowing within a second or two of flipping the switch.
Should I possibly be looking at replacing these 5U4's with other tubes such as 5AR4's or 5V4G or something like that if this amp allows it?
Should I consider installing a CL150 thermistor?
This amp no longer sees any kind of high demands like it did as an organ amp, but I still require it to provide the strong, tight and punchy deep bass that it has now. I just want it to be as safe as possible and be gentler on all the tubes. And unfortunately, I do not know what the different voltages are in this amp. I guess I'd have to speak with my father and see where I need to probe with my old table top HP DMM to take measurements.
Any info will be greatly appreciated!
At any rate, this amp uses two 5U4GB rectifier tubes. I assume it was designed this way to provide ample current and output on demand without "sagging" when full organ was required. It proves to be a very solid design as this amp effortlessly powers my inefficient NHT 2.9's (86dB @ 1w/1m) with ease. Bass attack is extremely tight and punchy. Even my old Technics SU-8099 amp with its 115w per channel didn't provide this kind of controlled bass.
Anyway, I've been doing some brief reading around the forum about the 5U4 tubes and rumor has it they heat up very quick and throw B+ to the output tubes way before they are heated up properly to receive that voltage. Apparently that can cause damage to the output tubes and I'm sure the driver tubes as well.
I also read that the 5U4's are known for sparking or "spark out" as TubeLab calls it. What's curious about his statement ( http://www.diyaudio.com/forums/tubelab/129396-rectifier-tube-5ar4-vs-5u4gb.html ) in this link is that these 5U4's did this with 47uF caps which is what I'm using in my amp, FOUR of them in fact, all rated at 450v. That really concerns me!
Now I haven't noticed any sparking of any kind when I power up this amp and maybe it doesn't because there's twice as much draw being there's two 5U4's there. However I do notice that the filaments in the 6L6's are glowing within a second or two of flipping the switch.
Should I possibly be looking at replacing these 5U4's with other tubes such as 5AR4's or 5V4G or something like that if this amp allows it?
Should I consider installing a CL150 thermistor?
This amp no longer sees any kind of high demands like it did as an organ amp, but I still require it to provide the strong, tight and punchy deep bass that it has now. I just want it to be as safe as possible and be gentler on all the tubes. And unfortunately, I do not know what the different voltages are in this amp. I guess I'd have to speak with my father and see where I need to probe with my old table top HP DMM to take measurements.
Any info will be greatly appreciated!