This pedal is a copy of legendary "Deacy" amplifier, that was used extensively by Brian May of Queen in countless number of records. Unlike Vox VBM-1 amplifier that I own as well, it's schematic is absolutely authentic. It utilizes old germanium PNP transistors AC125, AC126 and 2xAC128 and 2 transformers: a driver and an output one. As a big plus it has built-in (bypassable if you'll ever want it) Rangemaster with beautiful Soviet germanium transistor МП39Б. 4-16 Ohm load switch allows you to drive 16 Ohm cabinets, that are quite more common than 4 Ohm ones, original "Deacy" is purposed to be used with. Other convenient features are: On-Off switch, power source connector and, of course, battery powering option (more popular 6LF22 size was chosen. Exactly like an original amp it doesn't have any controls, knob on top is a boost level that works with Rangemaster only. Here are key features:
1. Precise replica of the original "Deacy" original transistors, transformers and circuit.
2. 4 Ohm / 16 Ohm load switch - allows you to use amp with 16 Ohm speakers/cabinets as well as with 4 Ohm ones that original unit was used with.
3. Built in beautiful Rangemaster utilizing germanium PNP transistor.
4. Rangemaster can be truly bypassed.
5. Rangemaster On indicator LED.
6. On-Off switch - to prolong battery life it's easy to switch it off when not needed, rather than unplugging plug from the input socket.
7. Power supply feed option.
8. Battery feed using 6LF22 size 9v battery option.
9. Neutrik sockets, robust metal case, good layout, quality components, very low noise.
Project started because I encountered transistors and transformers here: http://www.ebay.com/usr/elebcz. Though I have Vox VBM-1, that is a model of the original unit using a number of ICs, I was very curious of what the real thing is. Getting parts was fast and smooth, and I breadboarded the unit. Sound was excellent, but the big surprise was that amp just doesn't work with loads more than 4 Ohms. I could throw unit into oscillation on 6 Ohm load, with 16 Ohms load it oscillated instantly. I wanted an option to connect any cabinet to the amp, so I designed a 4/16 Ohm switch. In 4 Ohm position - it's an original "Deacy" without any modifications, in 16 Ohm mode - negative feedback path is slightly changed, that makes unit work with 16 Ohm load like with 4 Ohm one.
Thinking of the enclosure, I decided to put it in a pedal case. It doesn't take much space in my room, already overfull of other amps, it can be put into a guitar case and taken to rehearsal base.. So many benefits. After many hours of laying out a PCB I was very glad that it's possible to have an excellent layout on a very small board.
Next step was etching a breadboard, soldering, lots of mechanical works on enclosure and stuff. I never scrimp on components, decorative elements and other parts, neither I did for this project. I used the best components I could find, neutrik sockets, beautiful aluminum panel and very cool Soviet chicken-head knob.. Sure, unit came off very pretty. Ready-made device:
PCB (I experimented with transistors for Rangemaster, later on I decided to put a germanium one. The one on the photo is a silicon type that was replaced later):
Recording! I Couldn't wait to see amp in action. I had only quick auditions of the breadboard, but with ready-made amp I could enjoy the sound at the top of my bent. Like John Deacon, I used the very first speaker I had:
Willing to hear how timbre of the amp suits all the harmonies as soon as possible, I didn't waste time on experimenting with microphone placements, eqs and other studio techniques, recorded guitars very fast without any editing. I didn't even change a gain of the Rangemaster - it was always full up (that was a big mistake, as I see now, I should have lowered the gain). Guitar that I used: Stratocaster with bridge+middle in series for all voices. Sure, it's not exactly Brian's sound, considering all above, but it's clearly heard that "this is it". It is definitely the "Deacy", and getting that famous sound is not a big problem anymore:
I was very happy. Then, I decided to compare it with Vox VBM-1. I was very surprised that new pedal sounded so much better! First of all it's noise floor: it's so much lower than one of VBM-1. Now I don't have to bother how many guitars I have recorded and how much noise I'll get after that. Then, overall gain is higher, Rangemaster in the pedal has higher gain than one in the Vox. Probably, Vox had to lower the gain to keep noise of IC modeled transformers under a certain threshold. I use real transformers - they have zero noise, and overall circuitry has the same gain as in Brian's "Deacy". Also, what's extremely important to me, when played very accurate, pedal produces sweet and accurate sound, while VBM-1 is very harsh and spiky, sounding like one with improperly etched ground to me. I always used VBM-1 at highest possible gain, and it sounded best this way. With my new pedal I have an option to play the amp, varying it's gain and the way I pick a guitar. Picking a guitar different ways I can get as many different sounds as Brian can. I was never able to do it with VBM-1. It's extremely important for sounds like ones in Good Company, Winter's Tale and Bijou.
Now I have a reason to replace guts of my VBM-1 with original circuit. I will definitely not want to use VBM-1 as is anymore. But amp is so pretty looking that I want to keep it.. But only with completely new circuitry.
I can add that 250mAh 9v accumulator of 6LF22 size easily keeps amp running for more than 2 hours - more than enough for a rehearsal. Batteries last even longer. It makes this amp a good rehearsal device, you have to carry your guitar, this pedal and nothing more, not even a power supply is needed. Rehearsal bases usually have cabinets, 16 Ohm ones at least, that this amp can handle. Again, small enclosure allows transporting it to a rehearsal base in a guitar case.
