Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: John on August 23, 2011, 09:23:06 pm

Title: More headroom
Post by: John on August 23, 2011, 09:23:06 pm

Hi fellas, there are just a few songs we play where I'd like it to be as clean as possible while still putting out the volume. So my question is, could I implement a switch to bypass the first tube, the 5879? Or, would the Gain2 pot shown on Geezers original do the same thing, what with the added resistor before the grid on V2?

We had a backyard wedding we played at this past weekend, and I got nice compliments on the sound and chuckles at my woodworking.  :laugh:

Title: Re: More headroom
Post by: tubenit on August 24, 2011, 05:13:49 am

The first one you drew will not work because you need to ground the grid of the unused tube.  And you'd have a huge difference in volume between those two.

The second one where Geezer is using dual volume and master volume pots is what I personally would use. My impression (from Geezer's comments and sound bits) is that he likes to have a cleaner tone accessible. Since he is pleased with the amp, I am thinking he probably has achieved the clean/OD tone switching using this method.

Hopefully Geezer will chime in.  He is in Virginia where the earthquake hit.

With respect, Tubenit

Title: Re: More headroom
Post by: John on August 24, 2011, 05:50:15 am

Tubenit, thanks for the answer. That will give me the kick in the pants I need to actually finish it off with the relays.

Yes, hopefully Geezer's fine down there. In Westminster MD yesterday it rattled things, and that's a good 75 miles or so away from the epicenter.

Title: Re: More headroom
Post by: Geezer on August 24, 2011, 06:41:52 am

I'm ~~50mi from the epicenter, but we didn't get much "effect", just some slight shaking for 15-20 seconds. I am to the west, and the vector seemed to be strongest north/south of the epicenter. Plus, I'm surrounded by mountains, so I think they absorbed much of the shock(?).

As for the headroom thing, the "fake" channel switch is the way to go (2nd posted schem, as Tubenit suggested). I use it all the time, as it allows me to preset the volume & gain for differing amounts of headroom.

G

Title: Re: More headroom
Post by: John on August 24, 2011, 08:38:58 am

Thank you both! And glad to see you didn't have any damage.

Title: Re: More headroom
Post by: HotBluePlates on August 24, 2011, 09:20:52 pm

And I'm about halfway between Baltimore and DC, and only noted a little damage to a couple buildings in Baltimore.