HELP! I final got round to finishing my Phonoclone last week. Everything was working great but today I took it apart to try some new coupling caps. When I put it back together I accidentality mixed the V++ and V-- power wires the wrong way round. It was still on the bench with the lid off when I powered it on, within a few seconds I noticed smoke and immediately pulled the plug.
I wired it up correctly and tested the positive and negative voltage rails according to the build notes and they're still good to within 10mV of each other.
However I then noticed R11 on both boards look burnt and possibly R12. I used my multimeter to test them. R11 are down to just over 20ohm. R12 are still measuring 22.1ohm. I've still got a coupe of 22.1ohm resistors left over so I can replace the R11...
Visually, nothing else looks damaged but I'm wary about hooking it up to my system just in case blow-up my cartridge! I've no idea how to / if I can test the op-amps and transistors. Is there anything I should test (or replace) before plugging it all back in?
I wired it up correctly and tested the positive and negative voltage rails according to the build notes and they're still good to within 10mV of each other.
However I then noticed R11 on both boards look burnt and possibly R12. I used my multimeter to test them. R11 are down to just over 20ohm. R12 are still measuring 22.1ohm. I've still got a coupe of 22.1ohm resistors left over so I can replace the R11...
Visually, nothing else looks damaged but I'm wary about hooking it up to my system just in case blow-up my cartridge! I've no idea how to / if I can test the op-amps and transistors. Is there anything I should test (or replace) before plugging it all back in?
I remember some people posting in this thread a couple of years back with some crazy Vreg mods, discrete boards that were plug-in replacements for the LM7x12s.
The possibilities are open, but at some point the fundamental limit is the stereo design of the VSPS with the dual op amp sharing the same power rails. Dual mono aka the Emerald the "out".
The possibilities are open, but at some point the fundamental limit is the stereo design of the VSPS with the dual op amp sharing the same power rails. Dual mono aka the Emerald the "out".
Hi captain pugwash,
One thing not often considered when "improving" a design are things like limitations of the source. Something that comes to mind would be stereo separation.
The most important aspect of a regulator would be isolation of mains borne noise, the second would be minimal noise from that regulator itself. There are practical limitations for performance of things like regulators where beyond those points, further improvement doesn't bring any benefits to the table.
Some regulators are better than others. But from what I have seen, discrete regulators in the footprint of the industry standard ones do not perform as well. They are typically sold on the idea that they "sound better". That should be a sign that you should check the actual performance data more carefully. If those specifications are not given in a standard, clear format, I would avoid the part without further investigation.
When planning improvements, look at the system as a whole.
-Chris
One thing not often considered when "improving" a design are things like limitations of the source. Something that comes to mind would be stereo separation.
The most important aspect of a regulator would be isolation of mains borne noise, the second would be minimal noise from that regulator itself. There are practical limitations for performance of things like regulators where beyond those points, further improvement doesn't bring any benefits to the table.
Some regulators are better than others. But from what I have seen, discrete regulators in the footprint of the industry standard ones do not perform as well. They are typically sold on the idea that they "sound better". That should be a sign that you should check the actual performance data more carefully. If those specifications are not given in a standard, clear format, I would avoid the part without further investigation.
When planning improvements, look at the system as a whole.
-Chris
Remember that the op amp is designed to neutralize noise on its power rails (how much being defined by the PSRR), but it also produces its own self-noise on the output.
The regulators "job" is to reduce the power rail noise below the point where the op amp self noise begins to dominate the output.
Since the PSRR of most op amps is so huge, this is not such a difficult task.
Thus choosing a regulator because it advertises to remove lots of noise is misguided. (for an op amp circuit at any rate)
A better metric is how much noise the regulator self-generates, especially at high frequencies which the op amp has more trouble neutralizing. At heart, a regulator circuit is just a reference voltage source connected to an amplifier. Finally, you have to consider the dynamic performance of the amplifier built into the regulator .. its recovery after transients, overall stability, speed, etc.
The regulators "job" is to reduce the power rail noise below the point where the op amp self noise begins to dominate the output.
Since the PSRR of most op amps is so huge, this is not such a difficult task.
Thus choosing a regulator because it advertises to remove lots of noise is misguided. (for an op amp circuit at any rate)
A better metric is how much noise the regulator self-generates, especially at high frequencies which the op amp has more trouble neutralizing. At heart, a regulator circuit is just a reference voltage source connected to an amplifier. Finally, you have to consider the dynamic performance of the amplifier built into the regulator .. its recovery after transients, overall stability, speed, etc.
Hi all! To this day still enjoying my stereo VSPS, buffered with Richard's bboards!
I'm posting this because I was messing around with some spare opamps i have laying around, and thought I give the LME49720 a try in the VSPS. Guess what.... I all of a sudden had made a VSFMRR, a Very Simple FM Radio Receiver. I could faintly but very clearly hear a local station on 94.4Mhz, with the volume on my amp all the way up, it was almost enjoyable!
Needless to say, the JRC MUSES 8820 I have been using all these years is back in business!
I'm posting this because I was messing around with some spare opamps i have laying around, and thought I give the LME49720 a try in the VSPS. Guess what.... I all of a sudden had made a VSFMRR, a Very Simple FM Radio Receiver. I could faintly but very clearly hear a local station on 94.4Mhz, with the volume on my amp all the way up, it was almost enjoyable!
Needless to say, the JRC MUSES 8820 I have been using all these years is back in business!
Indeed, and if we believe that the LME49720 is in fact the same as the LM4562 (specs are identical, according to the internet!), Doug Self does write:
"The LM4562 represents a real advance on the 5532. It is, however, still a good deal more expensive and is not perfect –it appears to be more easily damaged by excess common-mode voltages, and there is some evidence it is more susceptible to RF demodulation."
@rjm : sorry if this has been discussed earlier in the thread, but what are the practical differences/consequences between BJT and JFET input types in an application like the VSPS? Which kind would you recommend (if that's even possible)?
Noise. JFET vs BJT is a consideration of high voltage noise and low current noise vs. high current noise and low voltage noise. The higher the input impedance, the more JFETs are favored. MC carts have very low impedance so BJT is a clear choice, for MM it's a bit of a half/half scenario, both are okay though on paper BJT usually have an edge.
Even if it worked fine, i would still keep that Muses 8820.
It is a very pleasant sounding opamp.
To my ears, it is better than LME49720 for the VSPS.
More 'analogue' sounding.
hello Richard,
Currently, I am using the DL103 with the Emerald, and thinking to change the cartridge to "recommended loading: >100ohm, 20ohm MC transformer.
Internal impedance, DC resistance: 20 Ohm. Output voltage : 0.35mV".
Do I need to change the values of R1 and R2? if yes what are the values?
Currently, I am using the DL103 with the Emerald, and thinking to change the cartridge to "recommended loading: >100ohm, 20ohm MC transformer.
Internal impedance, DC resistance: 20 Ohm. Output voltage : 0.35mV".
Do I need to change the values of R1 and R2? if yes what are the values?
I like the VSPS really good so far. My Technics 1210 MkII with an Ortofon DJ Scratch needle is attached to it. The problem is, that the output of the VSPS is comparably quite. It is not very quite but still quiter than my other audio sources. Is it possible to adjust the output gain somehow?