Sovtek Mig50 Preamp Heater Mod for 12AX7 tubes

DSC_0029DSC_0060DSC_0059DSC_0057DSC_0058DSC_0056DSC_0055DSC_0054Tubes out and testedTubes out and testedWiring a bit "freeform"Wiring a bit “freeform”Little radia caps 250V used in the power supply.. HT is only 395V so two 250V caps in series is fineLittle radia caps 250V used in the power supply.. HT is only 395V so two 250V caps in series is fineDSC_0035Heater circuit wired up for the Russian 6n2p the customer wanted it rewired for 12AX7 and provided 3 rather nice old Mullard tubesHeater circuit wired up for the Russian 6n2p the customer wanted it rewired for 12AX7 and provided 3 rather nice old Mullard tubesDSC_0037After rewiring...After rewiring…12AX7 Tubes in all a glowing...12AX7 Tubes in all a glowing…Love this power transformer... so military looking. 2 different heater output one for preamp one for power amp.. about 400V HT when rectfiedLove this power transformer… so military looking. 2 different heater output one for preamp one for power amp.. about 400V HT when rectfiedDSC_0045DSC_0032DSC_0051Output transformer is a fair size with tones of bottom end!Output transformer is a fair size with tones of bottom end!DSC_0046DSC_0031DSC_0047Checking bias... matching not great between tubes with 20mA on one and 30mA on the other.. a little cold too but the customer liked the sound he was getting so I left them set like that.. no harm in itChecking bias… matching not great between tubes with 20mA on one and 30mA on the other.. a little cold too but the customer liked the sound he was getting so I left them set like that.. no harm in itDSC_0049All tested and sounding really good!All tested and sounding really good!Back together and ready for the customer!Back together and ready for the customer! Lovely Sovtek MIG50 in to have it’s preamp modified for 12AX7 valves (currently using Russian 6n2p which have different heater pin out to the 12AX7 tubes. Nicely made amp with unusual transformers. Sounded fantastic on the bench when finished. The wiring could be neater though but no issues in functionality.

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