Ohm Settings

[blueswaite]

I am trying to think back to along time ago. My Blue Voodoo for practice is alittle loud at the lowest I can get the volume with out losing a good sound.
The cab is 16 ohms. the head is set to 16 ohms. I though you could set the ohms on the head at 8 and have a 16 ohm cab and basically loose volume. It will not be as loud but is it safe to run it this way. Seems way back in the days we use to do this.
Thanks

[sumgai]

bw,

You can do it, but you may not notice much difference in overall level. Where you will likely hear a difference is in the tonality. Going into a higher ohm'ed speaker cabinet, the sound tends to get "darker" - it loses some of the sparkle.

The general rule-of-thumb is that you can go half or double the rated output ohms, but the higher the volume level, the harder you abuse the amp (tubes, transformer, power supply, you get the drift.....). Keeping the volume low is not likely to enter 'abuse territory', but you never know - there are lots of factors and "gotcha's" lurking in the woodwork. It's a rule-of-thumb, not a physical law of the universe, you understand. Engineers would say that you risk everything from catching herpes to blowing the Hubble telescope out of the sky, but real-life experience says it ain't quite that bad.

HTH


sumgai

[blueswaite]

I ran it for about 30 minutes at 8 ohms with the 16 ohm cab and it seemed alright. The one thing I did like was it tamed some of the brittleness on the high end.
I have to see where I read it but I think someone said on a Blue Voodoo change preamp tube V4 to a 12A7T I think it was and it tames the high end.
Over all I am pretty happy with it. Probably should get the 60 watt though. It would be more controlable for volume
Thanks

[sumgai]

bw,

V4 is the phase-splitter and driver for the power tubes. Lowering that tube's gain factor a bit (stepping down from a 12AX7) is usually a good idea, if one isn't into death metal and such. BTW, that would be a 12AT7, not a 12A7T. I'll assume your fingers just got ahead of the game for a moment there.

If using the 16Ω cab with the 8Ω output setting sounds good, then you can probably do this safely for a long time, providing you don't try to make the neighbor's ears bleed!

Now you know why lower-output tube amps are always in demand. There's a valid reason why, year after year, the Fender Deluxe Reverb outsells all other amplifiers combined, if you take the Fender Twin Reverb out of that equation.

HTH



sumgai

[blueswaite]

Thanks
I'll have to see if I can get the info on which preamp tube is witch. I think I a pretty sure though.
Looking from the front thru the grill you can see the 4 power tubes behind the preamp tubes. Left to right I will call them 1, 2, 3, 4
Row in front of them is the preamp tubes. to the left of the power tubes is a lone preamp tube than between tube 3 and 4 is the first of the other 3 preamp tubesand the continue to the right side. The 3rd preamp tube is about 4 inches past power tube 4. I think the lone one is the V4 then the one between power tube 3 and 4 is V1 than V2 than V3
my understanding the closest one to the power tubes is V1.

[sumgai]

bw,

I seem to recall that we've gone through this before, so before I get off on the wrong track, remind me... which model of Blue Vooodoo do you have? And did we already find a schematic for this thing, or only one that was close?



sumgai