Thanks Richard,
I made a mistake in my first e-mail. The OpAmps in my bin are actually single OnSemi SE5534. From the datasheet these draw 4mA (typ) to 6.5mA (max).
If I understand correctly, that should give me no heat worries at 110C/W with 470R for R1, which gives V_opamps of 18V for 15VAC.
Learning as I go here, and every time I think I've grasped one aspect, something comes along to disabuse me of that notion!
Duncan
I made a mistake in my first e-mail. The OpAmps in my bin are actually single OnSemi SE5534. From the datasheet these draw 4mA (typ) to 6.5mA (max).
If I understand correctly, that should give me no heat worries at 110C/W with 470R for R1, which gives V_opamps of 18V for 15VAC.
Learning as I go here, and every time I think I've grasped one aspect, something comes along to disabuse me of that notion!
Duncan
Hi everyone. An FYI:
I've designed a new phono stage. Discrete this time around, two stage jfet with passive eq.
I would expect a very different experience compared to the VSPS circuits.
I've designed a new phono stage. Discrete this time around, two stage jfet with passive eq.
I would expect a very different experience compared to the VSPS circuits.
If my VSPS had one area that could be improved on it would be in the portrayal of front to back sound stage depth. I can not fault it on anything else and it betters may more expensive products (not DIY). In retrospect in my system it has a very BIG sound and plenty of drive. Richard how would you describe the difference?
It's gonna be sloppier. Probably more fun.
I mean, I haven't built it yet but I can tell a certain amount just from the distortion behavior, and remembering how my 6DJ8 stage sounded like. Op amp phono stages are in comparison more businesslike, where you concentrate on getting as much info off the groove as possible. A passive FET stage like this is more about enjoying the voicing of the preamp in and of itself. You either find that appealing or you don't.
I mean, I haven't built it yet but I can tell a certain amount just from the distortion behavior, and remembering how my 6DJ8 stage sounded like. Op amp phono stages are in comparison more businesslike, where you concentrate on getting as much info off the groove as possible. A passive FET stage like this is more about enjoying the voicing of the preamp in and of itself. You either find that appealing or you don't.
I'm always surprised how many people manage to make this mistake. How do you not manage to connect the bridge rectifier "+" to to V++? Did you not use color-code wires, or was it the XLR pin numbers that threw you off? You there is any doubt you can always check by measuring the power supply cable before it is connected to the boards.
Anyhow, a blown fuse meant a lot of current got dumped somewhere.
The usual suspects are the 1000 uF filter capacitors (overheat, burst) or the regulator transistors (zapped). The damage doesn't usually get further than that, and if your fuse was quick-acting you might be completely ok. No smoke or swollen caps? Then a 50/50 chance of survival.
I would connect it again with a new fuse and power it up. If it passes the smoke test check the voltages and if they are OK then you are probably good to go, but keep in mind the filter caps may still have been damaged and now have higher than normal leakage current.
Anyhow, a blown fuse meant a lot of current got dumped somewhere.
The usual suspects are the 1000 uF filter capacitors (overheat, burst) or the regulator transistors (zapped). The damage doesn't usually get further than that, and if your fuse was quick-acting you might be completely ok. No smoke or swollen caps? Then a 50/50 chance of survival.
I would connect it again with a new fuse and power it up. If it passes the smoke test check the voltages and if they are OK then you are probably good to go, but keep in mind the filter caps may still have been damaged and now have higher than normal leakage current.
Two issues caused this - (1) the board markings are covered by the connector, but more so, (2) I was anxious after testing the raw supply (everything was OK there) to hook things up and the two phono boards are facing in opposite directions, but I wired them the same (+ on right, - on left). Totally my screwup!
Thanks for your thoughts. I'll report back on the situation.
Thanks for your thoughts. I'll report back on the situation.
mis wiring of PSU to circuit
I use a diodes (1n4004) across the circuit PCB local decoupling of my power amplifiers.
When the diode/s pass due to inadvertant reverse current flow, the bulb of the Mains Bulb Tester turns on and protects the circuit.
I have rarely done this with pre-amps, but the diode protection does work for PSU screw ups.
The reverse voltage is limited to <1Vdc and no damage!
I use a diodes (1n4004) across the circuit PCB local decoupling of my power amplifiers.
When the diode/s pass due to inadvertant reverse current flow, the bulb of the Mains Bulb Tester turns on and protects the circuit.
I have rarely done this with pre-amps, but the diode protection does work for PSU screw ups.
The reverse voltage is limited to <1Vdc and no damage!
I haven't come across this terminology before. Is that a UK thing, some sort of circuit breaker?
type Mains Bulb Tester into the Forum's "search" function.
A few refer to it as a dim bulb tester.
It was used way back in the 1930's and maybe earlier.
I discovered it here when trying to find a safe method of wiring up dual primary mains transformers when one is not sure of the winding phase for 240Vac operation.