john.luckins
pfm Member
Thanks David. I do have a load of large green 18ohm wirewound, about 5W I think so I'll try them first. Later on it'll be interesting to see if regulated DC for the heaters sounds any different!
Great accessible little project. Thanks very much for posting. Maybe it can become the valve alternative to the Pink Fish/Piglets Dad B4?
I fancy a go at this as a first foray into Valve builds as well. Had a good look at the design and mugged up on some valve theory with Morgan Jones's book.
A couple or three newbie questions if I may please?
The ECC88 is a double triode. I've read it can be used in parallel. Are we doing that in this design or is it one half for each channel? There are two valve bases at the top of the BOM, so perhaps we are leaving one half of each ECC88 unused?
I have a 12v transfomer I can use for the heater but will need to drop the voltage to 6.3v. Will a LM317 based circuit be OK for current at 1.5 Amps max?
Can I make the higher wattage resistors up from 0.5W metal film in series or are wirewound better for other reasons?
Thanks for the inspiration.
John
Great accessible little project. Thanks very much for posting. Maybe it can become the valve alternative to the Pink Fish/Piglets Dad B4?
Thanks for the inspiration.
John
That's precisely what I would like to do.
Yes, thank you.
I have a spare one of these, more than up for the task it seems
http://rover.ebay.com/rover/1/711-5...0001&campid=5338728743&icep_item=131848217900
One suggestion- The addition of a 1M ohm resistor from the output terminal to ground would eliminate the build up of any DC offset on the output capacitor and keep a grid leak path from the grid of the triode to ground should the wiper of the volume pot fail open circuit or become noisy.
There is already such a path via the vol control and this is why I didn't fit such a resistor. It's not an oversight.