I recently built a 5e3 ... The amp sounds great, but I noticed that it stays pretty clean and doesn't seem to break up as quickly as other 5e3s that I see videos for. ... my voltages ... are slightly higher ... Could the higher headroom I'm getting be attributed to the higher voltages?
The voltages I have are:
B+1 387
B+2 345
B+3 270
V1 12AX7A
#1 147
#3 1.47
#6 174
#8 1.4
V2 12AX7A
#1 184
#3 1.39
#6 219
#7 15.5
#8 50
V3 & V4 6V6GT
#3 379
#4 343
#8 21
My opinion is that your amp is fine, and that you might be mislead comparing amp-in-room to unknown-conditions-in-video.
I see this a lot on forums, where players are fooled by the relative-loudness of talking & distorted-amp being similar in the video. However, that's often merely the video editor normalizing volumes so that the viewer doesn't need to make major volume changes between sections when watching the playback.
A tweed Deluxe is plenty-loud when it distorts, which by design is when pushing the power tubes beyond making all the clean output power they can (15 watts?). At that point, typical lower-sensitivity Jensen-style alnico speakers would be making ≤106dB, which is quite loud. So if you think "my amp has a lot of headroom" based on relative loudness of "talking" to "Amp-dirt" then your amp is probably normal.
Maybe you're making the judgment based on the setting of your amp's Volume control compared to some setting shown in a video. Esquirefreak was right to say if your amp uses audio-taper pots and the video-amp uses linear-taper, that could account for the difference of settings. And there's no telling how your guitar's pickup-output compares to the video-guitar, etc.
Based on
Robinette's diagram of typical 5E3 voltages (and what I've seen over time), I don't think your slightly-higher voltages would cause a significant headroom increase. That said, original 1950s Deluxe amps had voltages & output tube bias-voltage creep up over time, possibly to raise output power slightly. Your amp's 21v across the cathode resistor is very close to Robinette's 20v, though both are well above the
18v shown on Fender's 5C3 Deluxe layout.
So what? The 5C3 Deluxe would distort when receiving an 18v peak signal, but your amp will need a 21v peak signal to distort. That could be part of the "headroom" you're experiencing. Except we can't just reduce the cathode voltage, because tube plate current would go up, and your bias probe already indicates 364v x 0.040A = 14.56 watts (hot, but fine/typical for a tweed Deluxe). And FWIW, I also have some Eurotubes bias probes, and can confidently report they measure plate currently
only (not cathode current) and plate-to-cathode voltage. Therefore, they give you the exact information you would prefer when performing multiple manual steps (it's also why you report "40mA" but your cathode voltage would seem to imply "42mA" per tube).
What to do? You could simply make the 4.7kΩ resistor between B+1 and B+2 a larger value. The 5C3 Deluxe used a 10kΩ resistor here, but your amp has higher voltage at B+1 (345v) than the 5C3 Deluxe did (308v). You might choose to get a few 5w resistors in 10kΩ, 15kΩ, etc. Then you could try them out & see which brings down the 6V6 dissipation and increases the power-section sensitivity in the way you prefer.
Never built one of these, so disclaimer up front, but isn't V1 meant to be a 12AY7?
This is true. Though the 12AX7 would be higher-gain, and we might expect folks to interpret this as "less headroom."
Also, Fender always used the same parts-values for their preamp circuit whether there was a 12AX7 or a 12AY7 in the socket. So while folks may be right to point out these types should probably have different parts-values to "optimize" their use, that's not what we see done in historical amps.
Topic: Optimized 5e3 voltage questions (Read 7382 times)