2204 Marshall Build Half Power Switch

[Ed_Chambley]

I have a single input copy of a Fargen ole 800 which is just a souped up 2204.  It is a 50 watter running EL34's with plates at 470.  It is LOUD and already has a master volume.  Anyone ever installed a half power switch in a 2204.  Does it really make any difference in SPL?  I have searched for a schematic for this to no avail.  If anyone has any info I would really appreciate it.

[navdave]

Even if you wire in a pentode triode switch if wont help ur volume much
a 25 watt amp is still loud. Search VVR in this forum that may help.
Or invest in a powerbrake instead of hacking into your boutique amplifier.
Even a 5 watt amp thru a good 4x12 cab will scream 

[Ed_Chambley]

Even if you wire in a pentode triode switch if wont help ur volume much
a 25 watt amp is still loud. Search VVR in this forum that may help.
Or invest in a powerbrake instead of hacking into your boutique amplifier.
Even a 5 watt amp thru a good 4x12 cab will scream 

Thanks for the reply.  VVR in and VVR out.  I have installed a VVR in 5 different amps and have removed them all.  Tried them with just power tubes and scaling the whole amp.  I don't know why I don't like them as they seem so popular.  I think they are best in cathode bias and the only amp I have that is cathode bias is a Egnater Tweaker.  These are really cool amps with the proper tubes.  I didn't think the half power would do much, but Ben Fargen sure is very keen on them.

I didn't even think of a power brake, thanks for the suggestion as this is probably the best thing for this amp.

[Colas LeGrippa]

why don't you use half the winding of the PT secondary to get half the power ? with a switch you can toggle between full power or half of it.

Colas

[navdave]

Can you elaborate a little? Like a switch to go from full wave to half wave rectifier?

why don't you use half the winding of the PT secondary to get half the power ? with a switch you can toggle between full power or half of it.

Colas

[Ed_Chambley]

why don't you use half the winding of the PT secondary to get half the power ? with a switch you can toggle between full power or half of it.

Colas

Yes, how would you do this?

[Colas LeGrippa]

I'll post a schems when I find it. Basically you lift the power transformer high voltage secondary center tap from ground. Suppose your PT is 310-0-310. Intsall a one unit bridge rectifier  ( or 4 X 1n4007 ) with the minus to the chassis. One side of the ac high voltage secondary ( in this example, 310V ac ) is soldered to one of the AC input of the bridge rectifier. The other side of the HV is soldered to one side of a SPDT , the other side of the switch receiving the 0V ( center tap ) . The center of the switch is sent to the other side of the rectifier ac input so that you can toggle between the center tap, 0V and the other tap ( 310V ). In so doing, you get exactly half the power of the DC output of the bridge rectifier. You have previously removed the heater CT and hung it securely somewhere on a terminal post, eg. ,  installed gnd references to the two 3.15V of the heaters to gnd with two 100 OHM resistors . ASAT !

Colas

[alerich]

I have a Splawn Quick Rod (which is quite similar to a hot rodded Marshall 2203) that has a half power switch. The volume difference is not significant - almost negligible. I tend to prefer it at full power. I have a tough time expressing that sensation in quantitative terms but I seem to like the response of the power amp better at full power. Yes, it is loud either way. I usually run my amp through a THD Hot Plate attenuator at either the -4db or -8db setting. Just taking a little off the top doesn't make the tone suffer too much, in my opinion. Especially when you start with an amp that has tons of tone to spare like the Splawn.

I have installed the Dana Hall VVR in a Marshall Studio 15 (2 6V6) clone I built and while I do like it I still prefer to use the Hot Plate.