DIY 15/30W Amplifier

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#2
Attached to which point on which switch? To which ground? Unclear whether you are talking about doing something dangerous with the mains, or merely wasting power by using a big 'bleeder'. Why not tell us what you want to achieve? Maybe we can suggest a safe/sensible way to do it. If this is a guitar amp then you are in the wrong forum area.
 
#4
blackwhaleamp said:
You are right, I was reading more on the internet and I will go for a Pentode / Triode Half Power Switch. I just want a switch to change the amp from 15W to 30W.
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When I started experimenting with 'power reduction', I was surprised that there wasn't much difference in sound level unless I dropped the power a lot.

Although a triode/pentode switch will make a difference to the sound quality, there won't be a very big change in volume level, I think. Even 15W is LOUD!
But there is no harm in experimenting; that's the best way to find out.

VVR-type circuits are interesting and fun as they can change the overdrive characteristics as well as the volume, depending on whether the voltage reduction is on the preamp, power amp or both. More internet reading!
 
#5
VictoriaGuy said:
When I started experimenting with 'power reduction', I was surprised that there wasn't much difference in sound level unless I dropped the power a lot.
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I had the same experience as VictoriaGuy. Some years ago I grabbed a few power resistors and put together a 6 dB speaker-level attenuator, to cut the power from my Super Champ XD guitar amp from roughly 15 watts to roughly 4 watts.

This is a hybrid amp, and it sounds cold and solid-state until the power section (tubes) is getting pushed fairly hard. With the attenuator in place, the amp was still way too loud to use at home, and even too loud to use at the weekly living-room jams I used to attend at the time. In fact, at 4 watts, it seemed almost as obnoxiously loud as it had been at 15 watts. Six decibels of attenuation is not very much, to the ear!

I built a second attenuator to stack with the first one, to cut the power down another factor of four, this time to 1 watt nominal output. Still too loud for the home, but about right for those weekly jams (where I would be playing along with a mix of other instruments, including several acoustic guitars, and the odd mandolin, fiddle, uke, or keyboard).

At about that time I discovered the L-pad - an adjustable speaker attenuator. Using one of my 6 dB home-brewed attenuators followed by an L-pad, I finally got what I was looking for. I could turn down the power to milliwatts (which was about right for home use), or up to a couple of watts (for louder jams).

I shouldn't really have been surprised, since I know how decibels work. But there you have it, I had to cut the power by a factor of ten to really notice a substantial volume reduction!

-Gnobuddy
 
#6
Gnobuddy said:
I had the same experience as VictoriaGuy. Some years ago I grabbed a few power resistors and put together a 6 dB speaker-level attenuator, to cut the power from my Super Champ XD guitar amp from roughly 15 watts to roughly 4 watts. This is a hybrid amp, and it sounds cold and solid-state until the power section (tubes) is getting pushed fairly hard. With the attenuator in place, the amp was still way too loud to use at home, and even too loud to use at the weekly living-room jams I used to attend at the time. In fact, at 4 watts, it seemed almost as obnoxiously loud as it had been at 15 watts. Six decibels of attenuation is not very much, to the ear!
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Firstly, check your math---the difference between 4 watts and 15 watts is 4 db not 6 db.
This guy has a pretty good handle on regulating power:
Power Scaling Kits
 
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