I agree.
what would be an acceptably low value for the R43 resistors?
the measurings were taken when the Input was shortened with 10ohm. Will retry with 10k
Thanks Hesener, I've had enough practice at this little project of yours, Joachim's and FDW's.
If your going to build something it's worth while doing it right.
https://live.staticflickr.com/7848/33434148568_3fe86dcd5b_k.jpg
If your going to build something it's worth while doing it right.
https://live.staticflickr.com/7848/33434148568_3fe86dcd5b_k.jpg
Stick a10k across input and ground them adjust the central trimpot until you measure 0.0mv across the input. Then measure the rest of it.
I have a known good, separate, shunt reg pcb that I wire up for all my builds so I can check the riaa section. It means I can rule out any faults in the shunt.
I also put the last transistor on each side of the input stage on header pins, then you can swap them easily to adjust the offset before soldering them in.
I have a known good, separate, shunt reg pcb that I wire up for all my builds so I can check the riaa section. It means I can rule out any faults in the shunt.
I also put the last transistor on each side of the input stage on header pins, then you can swap them easily to adjust the offset before soldering them in.
Ok, reduced the R43s to some k below 100k, bridged the input with 10k and ajusted to close than 0V on the output.
Check!
Now connected both boards with 300R cross the input to the MC and measured output voltages just to play safe before connecting to the Amp.
16V - what??
Check!
Now connected both boards with 300R cross the input to the MC and measured output voltages just to play safe before connecting to the Amp.
16V - what??
Seems to be a grounding problem when the boards are fitted into the enclosure as board is ok w/o enclosure.
Will further check tomorrow.
Will further check tomorrow.
Wrong direction, guys!
It was an issue with the RCA connectors 🙄.
So if all is fine tonite, I'll have a first listening session.
Cheers
Stephan
It was an issue with the RCA connectors 🙄.
So if all is fine tonite, I'll have a first listening session.
Cheers
Stephan
Next issue - I hate this project 🤬
when I connect the cart and the power amp, boards are running wild.
Voltage on the outputs directly hits 14V and - 10V.
do I have an issue with grounding?
what has to be connected to central GND:
Cheers
Stephan
when I connect the cart and the power amp, boards are running wild.
Voltage on the outputs directly hits 14V and - 10V.
do I have an issue with grounding?
what has to be connected to central GND:
- GND from both inputs
- resistors from the impedance selectors
- GND from both outputs
Cheers
Stephan
Ah, I always float my sockets so the outer isn't in electrical contact with the chassis. Only mix signal gnd and psu 0v where I want. Which is normally in the psu.
I use a 4 core cable between psu and paradise boxes. +/-/0v and 4th wire for chassis gnd on paradise back to psu 0v star via a DDRC. Tonearm earth goes into isolated socket via 3 position switch, with floating, signal gnd or psu/chassis gnd as the 3 switch positions. That accommodates all possible deck/ tonearm wiring earth setups. Signal gnd is usually the quietest, but I've built patadises where it wasn't due to tonearm wiring.
I use a 4 core cable between psu and paradise boxes. +/-/0v and 4th wire for chassis gnd on paradise back to psu 0v star via a DDRC. Tonearm earth goes into isolated socket via 3 position switch, with floating, signal gnd or psu/chassis gnd as the 3 switch positions. That accommodates all possible deck/ tonearm wiring earth setups. Signal gnd is usually the quietest, but I've built patadises where it wasn't due to tonearm wiring.
I usually don't form a common bond between input and output socket signal gnd either. It's only a small loop, but it's a loop.
The loading resistor can be soldered to the spare set of input holes on the pcb, or wired onto an extra rca socket and soldered into an rca plug. Check you have no continuity between rca gnd and chassis on all sockets.
The loading resistor can be soldered to the spare set of input holes on the pcb, or wired onto an extra rca socket and soldered into an rca plug. Check you have no continuity between rca gnd and chassis on all sockets.
Changed all ins and outs to floating GND but still having problems when everything is connected.
But: when I disconnect the inputs all is fine. As soon as I connect the input channels the output voltage is running wild.
OK. Disconnected the inputs - all fine again.
Now: pulling the SME connector on the tonearm and connecting the inputs again. Everything still fine.
So what have we learned?
So there‘s a problem with the cartridge tonearm cables that causes issues with the Paradise but not with the resident preamp.
Ideas welcome, I‘ll call it a day now and will continue tomorrow.
Cheers
Stephan
But: when I disconnect the inputs all is fine. As soon as I connect the input channels the output voltage is running wild.
OK. Disconnected the inputs - all fine again.
Now: pulling the SME connector on the tonearm and connecting the inputs again. Everything still fine.
So what have we learned?
- Paradise Amp is ok now
- cable tonearm to Paradise is also fine.
So there‘s a problem with the cartridge tonearm cables that causes issues with the Paradise but not with the resident preamp.
Ideas welcome, I‘ll call it a day now and will continue tomorrow.
Cheers
Stephan
Try the same with resistive plugs (resistor in RCA plug mimicking the mc cart) on input.
Your conclusions above however are not valid.
Your conclusions above however are not valid.
If everything is good with only a resistor shorting the input it implies the boards are OK, but only with no input signal present.
That said I've never had a unit that measured in the sub mV on the outputs with input shorted that didn't work.
I'd be looking to try another cart and or arm before considering anything else. Actually I'd liquid flux the underside of the boards and reflow every joint. Then try the arm.
I've seen a few built by other people that were hard up against the rail where one of the smt caps on the underside were bridged with solder or had failed short, this puts rail voltage straight into one side of the input stage. Even had one in for inspection where you could cause this by slightly flexing the board.
That said I've never had a unit that measured in the sub mV on the outputs with input shorted that didn't work.
I'd be looking to try another cart and or arm before considering anything else. Actually I'd liquid flux the underside of the boards and reflow every joint. Then try the arm.
I've seen a few built by other people that were hard up against the rail where one of the smt caps on the underside were bridged with solder or had failed short, this puts rail voltage straight into one side of the input stage. Even had one in for inspection where you could cause this by slightly flexing the board.
So I’ve rechecked all rca connectors and tested each board independently.
Both of them work fine and play.
I’ve also checked left and right channel of the cartridge with each board. Also fine.
if I now connect both boards to the cartridge, output voltage runs wild. Which board I connect first and which one second does not matter.
To rule out the cartridge I’ve used a 4Ohm resistor that I’ve plugged into the SME on tonearm side with both left and right rcas connected to the boards. In this case one resistor is enough to cause trouble.
4Ohm is close to the 5ohm of my Koetsu.
I don’t get it.
Edit: might cable length be an issue? The cable is 2m long.
Both of them work fine and play.
I’ve also checked left and right channel of the cartridge with each board. Also fine.
if I now connect both boards to the cartridge, output voltage runs wild. Which board I connect first and which one second does not matter.
To rule out the cartridge I’ve used a 4Ohm resistor that I’ve plugged into the SME on tonearm side with both left and right rcas connected to the boards. In this case one resistor is enough to cause trouble.
4Ohm is close to the 5ohm of my Koetsu.
I don’t get it.
Edit: might cable length be an issue? The cable is 2m long.
Last edited:
I‘m done with this project - at least for the moment.
From my personal perspective this is the worst project ever - and the only electronics project I was unable to finish.
some takeaways for my personal list
From my personal perspective this is the worst project ever - and the only electronics project I was unable to finish.
some takeaways for my personal list
- never buy unfinished projects that have been lying around for a decade or more
- don’t mess with beta versions