Hello Joachim,
with lots of help from the friendly people of this forum!
I tried the 24v trafos but they failed powering up the regulator,
with 30v toroidals it works well.
Thank you for offering your preregulator schematic, it is (in the end)
easy to build up on a universal striped board, 10x16 cm.
Christoph
with lots of help from the friendly people of this forum!
I tried the 24v trafos but they failed powering up the regulator,
with 30v toroidals it works well.
Thank you for offering your preregulator schematic, it is (in the end)
easy to build up on a universal striped board, 10x16 cm.
Christoph
Joachim, have you seen my post?
My boards are finished, too.
The regulator is working fine, I could trim the input offset to 0mV but I have 2,5 and 2,7V at the external riaa and the output offset is fluctuating around underneath 1V.
I don't know if I should have the courage to connect it to my system
10kohm is quite high, as it will see leakage current variations of the elcaps and the BJTs. Once it is adjusted, try putting 10Ohm across the input as JG suggests, and let us know what the output does. It should be fine, meaning, no more significant voltage fluctuations. In fact, while the elcaps are "forming" (and that can take a couple weeks of constant operation), you may continue to see output voltage fluctuations, and it may pay off to re-adjust the input offset after that time. No need to worry, though.
Some DC across the "Ext RIAA" connector is no problem, it indicates the DC offset of the output buffer that the servo is trying to correct. Ideally, it should be zero. I had -1.5V there, and it still sounded (mighty) fine.....
Some DC across the "Ext RIAA" connector is no problem, it indicates the DC offset of the output buffer that the servo is trying to correct. Ideally, it should be zero. I had -1.5V there, and it still sounded (mighty) fine.....
A 22v traffo nicked from a Yamaha Av amp and a couple of Hackercap boards with Q-speed diodes, 6x Kendeil 63v 6800uf and hand wound coils in a CLCLC.
I have a little wandering on the output voltage but my multimeter does that anyway, so i'll have to wait until I can get my scope back to check it for sure. It does however sound mighty fine even like this and I have virtually no noise from the speakers- I don't even have the tonearm earth wire attached yet...!
Just one question, actually a repeat question. Is this really ok for the cartridge loading- signal and gnd wired into one set of the inputs, and a 3k resistor across signal and gnd on the other side of the center line? Or should the gnd wire be attached to the back of that 3k resistor?
An externally hosted image should be here but it was not working when we last tested it.
It's been a long road...thanks to all who helped out so far.
An externally hosted image should be here but it was not working when we last tested it.
I put a 10Ohm load across the input, the input offset is still fine and stable, no change at the ext. riaa and the output offset is still fluctuating, but at lower voltages.
With 10KOhm dummy it was underneath 1V, now it is underneath 100mV.
But I don't know how much I could trust my DMM at these low voltages.
With 10KOhm dummy it was underneath 1V, now it is underneath 100mV.
But I don't know how much I could trust my DMM at these low voltages.
Well, it isn't a very good DMM, not he cheapest also, but if I measure across the input in the same voltage range on the DMM I get a stable value at the display so I think the measurement are somehow reliable.
Well, meanwhile I installed my old OC9 on my second player and I think I will fire up the paradiese tomorow.
Maybe I need a new cartridge or even some new amps and speakers the day after tomorrow...but hey, no risk - no fun
And in the case this little joke comes true, I guess you guys have some nice projects out there
Well, meanwhile I installed my old OC9 on my second player and I think I will fire up the paradiese tomorow.
Maybe I need a new cartridge or even some new amps and speakers the day after tomorrow...but hey, no risk - no fun
And in the case this little joke comes true, I guess you guys have some nice projects out there