Power transformers

[savvy]

Hi,I am building an amplifier based on the SE-5a Ampmaker and have a PT running 255v as against the schem which calls for 190-0-190v.I am assured this is ok and have a modified schem and rectifier circuit with 4 diodes to suit the PT.My question is what difference will this make?more headroom,more power? The 2
valves I am using are an ECC82/12AU7 (2 stages) and then into an EL34 power stage. all heater voltages etc are as schematic.Thanks

[laird]

The SE-5a is based on an EL84 power tube, which would run fine from 255v rectified from a 190-0-190 PT. 255v would be a very low voltage for running an EL34 - they're usually run around 400-450v.

Could you link the schematic are you working from?

-Laird

[tele_wah_fuzz]

Higher voltage = tighter low end and slightly more headroom and clarity. Lower voltage = more sag and overdrive.

Eddie Van Halen used to variac his Marshalls to drop the B+ voltage to get that "brown sound"

[savvy]

I don't know if this will work but this is the modified schem or at least the jpeg of it.I havn't tried this before.The original schem is on ampmaker.com site as SE-5a british sound.I have the OT and am using an old Ibanez chassis.Cheers

[laird]

Yeah, that's an EL84 in the schematic. What gives it away is the connection to pin 9... EL34's only have 8 pins. Your 255v B+ should be just fine, though I expect you'll find the 12AU7 won't drive hard enough.

-Laird

[savvy]

Yes Laird my dropped bo--ock,I typed it wrongI have 2 ecc82/12au7's here so I thought I would try those first,if they don't work then I will sub an ecc83/12ax7I am doing it on a shoestring and so far it has cost £50.00 and all I need now is a 4pin input socket,power on sp switch(I have the power switch) and 5 pots, so maybe another £5.00 (gbp) oh and build a pine head cab to match my speaker cab,so all in all about 86 USD.
Thanks for your input,all the bits should be here tomorrow