Help With a New Project

[ncusack]

Ok so here are the key details. I have a Hammond 1750E and a 272DX I want to use. Some forum trolling led me to the California Dreamer Amp in the archives over at ax84. Im looking to build the lite version without reverb but was wondering if any of you trainwreck guys could suggest some modifications to the circuit that might give it some more tonal variance other than blackface cleans.

The schematic is attached. Im not sure about the choke in the power section though.

Let me know any ideas or suggestions you guys might have

[selloutrr]

What are you trying to achive?

adding a Post Phase Inverter Master Volume would give you nice drive - It makes the blackface bassman/bandmaster into a nice late 70's /early 80's AC/DC tone. Almost Marshall JMPish

If i'm reading it correctly you have an unused half on both preamp tubes. You could get creatative and cascade.

build the reverb into the circuit and instead of hooking up the tank add a 1K potentiometer across it so you can dial in a foot switchable overdrive.
you would have Send - (Gain amount) - Return knobs. label them something clever.

[ncusack]

The post PI master sounds like it would add more range to things and that schematic is only a 2 tube pre section 1 12ax7 then the 12at7 for the PI so no spare stages there.

[Super_Reverb]

A couple of ideas that I have tried and a some pondered:
i) Add a switch - maybe a pull switch on an existing pot position to float the tonestack - a poor man's boost

ii) many designs use a pot for the PI input resistor on (-) input with a cap from wiper to ground. - your 47 Ohm. Parts express has a 100 Ohm pot, so you could use a 1500-1800 Ohm feedback resistor from spkr out with a 100 OHm pot and you'd maintain a similar loop gain in the PI/out stage. This will give you voltage gain in PI/Out stages which increases with frequency - bypass cap progressively shorts out input resistor with increasing freq. Use f=1/(2*3.1416*R*C) as a starting point, e,g., with pot all the way up (R=100) and a 2.2uF, corner frequency would be about 700 Hz.

iii) How about wiring one 9-pin socket next to each of your 8-pin power tube sockets with EL84 plate pin connected to 6V6 plate pin, screen grid to screen grid, etc. This would give you an output tube option - a pair of 6V6s or EL84s with a bias adjustment via your handy bias voltage pot.




cheers,

rob

[selloutrr]

here are some thoughts.

tube cascading is out but if you are building from scratch you could add whatever you wanted Just to be different you could use a 6K11 tube (3sides of a 12ax7) like found in the ampeg V4 reverb sections.

[selloutrr]

I like the idea of adding the EL84 sockets how about taking it one step farther and adding a blending between the el84 and the octal power tubes.

It would be pretty trick to add a selector for a 100w - 50w - governor (variable selector so you can cut the wattage down to a couple watts like found in the sundown amps)

You could always run the amp with a variac at ~90VoltAC and get some very nice sag and brown sound.

[ncusack]

Those are all interesting ideas but im trying to keep things matched with the Iron I have and that 1750E is only a 15W output transformer typically used in a tweed deluxe. I was thinking I could go 6V6 rocket with this iron and that would mean a third preamp tube in the mix. Im not one for a lot of bells and whistles but I would like to achieve some tonal variations other than just the cleans. The Master volume idea sounds like it would be a decent modification here.

[selloutrr]

just stick a pedal in front of it and be done.

[selloutrr]