Allynmey wrote:Finally got to finish my Liverpool...
Allyn,
I find a resistor between the wiper of the volume pot and the grid of the second 1/2 12 AX7 on Mark Abbott's L'pool preamp schematic. He labels it Rgs. On your pics I see a blue wire from the volume pot wiper to pin 2 on V1. Did you put a resistor perhaps under the board?
For the coupling cap and grid leak resistor between V1 and V2 (C8 and R7 on Mark's schem), What values did you use? The best I can tell from your pics, the resistor is 150K (?brown, green, yellow), and (crane my neck the best I can) I can't see the value on the cap
Tim the 820 Ohm resistor your talking about isn't used on every 'wreck. Ken probably used it to calm an oscillation. I've seen about 5-6 'wrecks close up and only 2 had one. I used a 150K resistor on the Grid load like the Express. I like it! You can go as low as 68K on the Liverpool if you need to calm it down but, I saw two liverpools that used 150K's so I use them. The Grid load doesn't use a cap but, there is a .002 cap feeding the GL resistor.
Allynmey wrote:I've seen about 5-6 'wrecks close up...
Allyn, it appears to me that you designed your PS board based on the Ginger design rather than the later more Express-like board. There seems to be a dual cathode bias: a resistor (130R)/cap (220µF) for each pair of EL84's instead of one for all 4. Am I correct? Is that one of those "You can do it either way" circuit equivalents or is the dual supply better? Maybe it's like the 80µF cap and the 18k2 resistor, schem'd one way, implemented another
Thanks
Allynmey wrote:I've seen about 5-6 'wrecks close up...
Allyn, it appears to me that you designed your PS board based on the Ginger design rather than the later more Express-like board. There seems to be a dual cathode bias: a resistor (130R)/cap (220µF) for each pair of EL84's instead of one for all 4. Am I correct? Is that one of those "You can do it either way" circuit equivalents or is the dual supply better? Maybe it's like the 80µF cap and the 18k2 resistor, schem'd one way, implemented another
Thanks
Not to speak for Allyn but he built that Liverpool before the new pics came out and the Ginger PS was the only one we had pics of at the time. Using 2 cathode caps and resistors (one for each pair gives you the option to put in a 1/2 power switch and use smaller wattage resistors (10w). The resistors should be 120 - 125 ohms.
Dana and Allyn, thanks I'm trying to draw up a layout for the Express to go with my schematic with some labelling for less experienced builders. A dual cathode bias was my interpretation and seems to be present on the 86 L'pool pic, as well. Thanks for the confirmation
