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Bigbottle MM/MC Hybrid Valve Phonostage PCB

Good evening all.
Nearly finished with assembly, waiting for few more components.
Oliver, could you please confirm:
Position of LED, square pad is Anode?
Voltage supply to PCB 9,5 - 0 - 9,5 to LV and 0 - 165 to outside pins of HV?
MM or MC - switch position open or closed?
Best regards.
Sasha.
 
Square pad = Cathode.

Pardon the many files. But I enjoy doing this. It teaches me to remember. I hate always having to google it...when I'm soldering. One day....
 

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Last edited:
Good evening all.

Nearly finished with assembly, waiting for few more components.

Oliver, could you please confirm:

Position of LED, square pad is Anode? - see diagram above.

Voltage supply to PCB 9,5 - 0 - 9,5 to LV and 0 - 165 to outside pins of HV? - Yes

MM or MC - switch position open or closed? MC - Open. Leds light up in MM

Best regards.

Sasha.
 
Why not ECC88 so the sake of simplicity? I know it is not as cheap as PCC88 ..
I've seen price mentioned. But you could still use ECC88 by hacking the board. I haven't seen a schematic yet. I suppose a little IC is used to supply the 7volts...you could omit that, cut the traces and wire the socket directly to your 6.3V supply. Or perhaps even without cutting traces...
 
Just wanted to ask why use tubes that have different heater voltage? PCC88 is 7-7.6V (better to power them via 300mA CCS) and ECC83 are 6.3/12.6V?



Why not ECC88 so the sake of simplicity? I know it is not as cheap as PCC88 ...
The reason was gain and Millar Capacitance.

This valve combination gives the right amount of gain for what we wanted.

The combo also gave lower Millar Capicatnce than you would get from a phonostage with 3x ECC83

At the time, PCC88'S were plentiful and far cheaper than 83's too.

There were 3 very good reasons
 
I have connected the L/V side of things and my unloaded heater voltages across pins 4 and 5 are 6.49v. With the valves in place the heaters glow and the voltage drops below 6.3 volts. Using 6DJ8's with Craigs suggested mod.

With the H/V connected I have the following readings all measured to ground :- V1 pin 1 135.2V pin 2/3/7/8 0V pin 6 135.2V

V2 :- pin 1 149.9v pins 2/3/7/8 0v pin 6 150.2v

V3:- pin 1 236.3v pin 2 17.25v pin 3 16.69v pin 6 236.3v pin 7 17.17v pin 8 16.67v. I forgot to say the led's do not light up.

TIA

Nobody? Seems my confidence has deserted at the final hurdle😕