Recently I have built a 5f2a inspired amplifier which has reminded me how much I love the sound of low wattage single ended amps! Many have pondered how to get a higher powered version of that tonal bliss and have come up with parallel single ended designs as well as using larger transformers/power tubes to simply build a bigger single ended amp. Lately I have been interested in some of the old integrated high-fi tube amps that use two Output transformers which made me wonder: Could someone build 2 champ circuits in one combo amp chassis/ cabinet fed by the same input, with seperate vol and tone controls, separate OTs and a speaker for each channel?
I started sketching out a schematic drawing on some of the forum threads where people have built similar stereo guitar amps and then while reading Jack Darr's book, I found that he has a schematic for a circuit that uses a phase splitter after a tremolo oscillator and inserts the out of phase signals to the grids of two separate preamp channels to create true stereo tremolo! In the end I got down a rough draft without any component values.
My list of concerns for actualizing this thing:
1. The power supply. I figured if I used a simple preamp circuit with modest current demands that maybe I can use a simple, single-rectifier power rail design as opposed to a separate power supply for each circuit like on some stereo amp designs?
2. Transformer specs. would a normal PT and single ended OTs work?
3. Input signal strength. I know using a passive AB boxes cut you signal (in half?) when you use two amps at the same time.. Im guessing it would be the same if the input signal was separated to two different input stages.
Would it be as simple as adjusting the input impedance by increasing grid leak values on input stage?
4. tremolo function/ insertion. In Jack Darrs book he inserts the tremolo into the grids of two separate preamp channels using a phase splitter. On a typical vibrochamp the insertion point is the cathode of the second stage.. I have read that a cathode follower is used as a buffer to provide a low impedance signal which matches the cathode of the tube being inserted into.. I imagine the higher impedance plate signal from the splitter could cause problems and perhaps there are other problems I am probably not aware of.
I was thinking of maybe building it in a deluxe reverb sized cabinet or something similar with a 10" and 8" speaker.. It seems to have almost exactly the right number of holes for tone controls and the size seems about right to fit the speakers.
Anyone point me to schematics of people building something similar?
Topic: Stereo Vibro Champ concept (Read 2953 times)