Vermes
Advanced Member level 4
This is a chassis for a head, designed as a very fast hiGain, which includes 180W supply transformer and 70W speaker transformer. Power supply uses quite large capacitors 200uF and 100uF. Powering voltage in „AB” class is equal 485V. Power tubes are TAD EL34-STR, which are slightly larger than normal EL34 and can last greater load. Inverter of power tubes was made of ECC81, which is better than ECC83 for this purpose.
Preamplifier has 3xECC83 (two of them NOS RTF) in a non typical topology. The first stage consists of two triodes operating in a cascode circuit. The cascode circuit is very dynamic and wideband (cascode circuit significantly eliminates capacities between the tube electrodes). The gain on that stage is controlled by a switch on the panel.
The second and third stage are normal „cutters” that generate the distortion. In anodes and nets circuits, values of the resistors are relatively small. Net 500k instead of classic 1M, causes the tube faster goes out of the clogged state at strong distortions, and anode 100k, even though it reduces the gain, it „hardens” the operation of the entire stage and weakens the higher frequencies.
A patent of Soldano was implemened in the first stage of „cutters”. It consists of dynamic gain of a stage depending on the strength of hitting the strings (it operates like expander, inverse of the compressor). Eventually, this gives a great increase of sound dynamic despite a large gain which flatters the sound. The second stage of „cutters” is a classic with switchable gain.
The fourth stage is the separator, which efficiently powers the tone of sound. Behind the preamplifier, you can find the connectors of effect loop with switchable levels (-4 / +10 dB).
The whole was soldered p-2p. Resistors were metallized. High voltage capacitors are from Marloy and Silver Mica. TAD capacitors were used in the power supply.
Effects which can be reached using this device:
- clean
- crunch
- distortion
- rock
- hi-gain
Schematic of the premplifier and other pictures:
And how it looks in total (head and box) in housing made by a company.
Some samples recorded using SM57 and Cparison Dellinger I.
Link to original thread (useful attachment) - Piec do gitary 60W "Chameleon"
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