RickP
Established 1960, Still Not Dead
A significant testing delay occurred when my daughter gave birth to grandchild #11... a healthy baby girl named Rosalie. Some interruptions you just don't mind.
Ok, ear plugs in place, test 1 was conducted. I unhooked the Ox Box and all its paraphernalia from the loop. 50 watt HXDA, straight to 2x12 cabinet, dB meter approximately one meter from front of cab. Master dimed. HXDA Gain about noon, Bass Gain about 9 o'clock, DA/HX/DA on switches, 594 Soapy as tester. The first tests I had the meter on C Weighting, which I don't pretend to understand, though I know A Weighting is supposed to be tilted towards the human hearing spectrum. I tried both and, although the actual numbers differed, the difference caused by the voltage drop to 90 VAC was the same... 6 dB. I used the opening lick from "Adam's Apple" by Aerosmith as it has a combination of single notes and chords and ends in a sustaining open G that is one of the best Marshall karang chords in existence.
C Weighted (I think this is normal dB), 117 VAC
120 dB on the sustained G
Same settings, regulated to 90 VAC
114 dB on the sustained G
A Weighting showed the same range, but the top was 113-114 dB
So, that gives good evidence that the Variac cuts volume significantly* when VAC is lowered about 25%. I did not attempt any re-biasing, the only thing changed was the voltage.
* "Significantly" will still make you deaf or get you fired in my neck of the woods. Definitely quieter, tone still great. But still loud. Real loud. But if you aren't diming the master and just need to shave some off the dB level, you'd be there.
Impression #1, Ed was right, and it does work. It would probably be even more effective on a 100 watt amp. It still sounds great, but I wasn't removing my ear plugs to get an accurate bare eardrums comparison. I like hearing. I will need to set up a recording to compare. Ear-plugged and all, it sounded great both ways, and was concussively punchy untethered. It is absolutely clear why people like to play this way.
Is it better than an Ox Box? No, no contest there. But at about 18% the price of entry, it might be a good option! I will do some more "turned down" tests and see what's what there.
Ok, ear plugs in place, test 1 was conducted. I unhooked the Ox Box and all its paraphernalia from the loop. 50 watt HXDA, straight to 2x12 cabinet, dB meter approximately one meter from front of cab. Master dimed. HXDA Gain about noon, Bass Gain about 9 o'clock, DA/HX/DA on switches, 594 Soapy as tester. The first tests I had the meter on C Weighting, which I don't pretend to understand, though I know A Weighting is supposed to be tilted towards the human hearing spectrum. I tried both and, although the actual numbers differed, the difference caused by the voltage drop to 90 VAC was the same... 6 dB. I used the opening lick from "Adam's Apple" by Aerosmith as it has a combination of single notes and chords and ends in a sustaining open G that is one of the best Marshall karang chords in existence.
C Weighted (I think this is normal dB), 117 VAC
120 dB on the sustained G
Same settings, regulated to 90 VAC
114 dB on the sustained G
A Weighting showed the same range, but the top was 113-114 dB
So, that gives good evidence that the Variac cuts volume significantly* when VAC is lowered about 25%. I did not attempt any re-biasing, the only thing changed was the voltage.
* "Significantly" will still make you deaf or get you fired in my neck of the woods. Definitely quieter, tone still great. But still loud. Real loud. But if you aren't diming the master and just need to shave some off the dB level, you'd be there.
Impression #1, Ed was right, and it does work. It would probably be even more effective on a 100 watt amp. It still sounds great, but I wasn't removing my ear plugs to get an accurate bare eardrums comparison. I like hearing. I will need to set up a recording to compare. Ear-plugged and all, it sounded great both ways, and was concussively punchy untethered. It is absolutely clear why people like to play this way.
Is it better than an Ox Box? No, no contest there. But at about 18% the price of entry, it might be a good option! I will do some more "turned down" tests and see what's what there.