I know, but I'm trying to learn as I enjoy the music. I put out my reasoning hoping someone would either concur or explain why it's not as I see it. I'm simply asking questions (OK, I didn't phrase the above as a question...) based on my obviously limited knowledge of how AC works. You see, I was always the kid who asked questions when no one else would - and would always have several kids thank me for asking b/c they were wondering the same thing.
OK, I'll try to stop bugging you all.
OK, I'll try to stop bugging you all.
No no, I'm mostly just kidding you- hence the emoticon. It's a good thing to ask about stuff. Richard is clearly going to have a really solid grasp of this circuit though, so he has presented you with a reasoned suggestion on priorities. I must admit I was a little surprised that his advice seemed to be disregarded though! If you check out his own BoM for the board, you'll see his preferences for the component choices. I've yet to build mine, but a friend of mine uses a Phonoclone in a pretty serious system using one of Richard's kits of parts. It sounds excellent. The trouble with parts substitution questions is that personal preferences and the particular characteristics of your room and system are issues that the designer can't really address. Try out some options by all means, but you will find that the standard parts give very good results. I wouldn't get too snarled up with details. I suggest you build it to whatever budget you decide on and listen to it. My experience- FWIW- is that a single component change in a circuit will rarely affect a transformation unless the part being replaced really sucks. Best of luck, and do report back on any experiments with parts that you do.
I have a PC3 between 6K of turntable and 6K of electronics, and its built to the BoM except the loading caps changed to suite the cart, and the output cap changed to a Clarity Cap. I have not felt any other need to tweak it, and it will stay as is until I can afford the 2K5 phono stage I lust after.
As there is no concrete reason why the resistor construction should influence the sound quality, there can be no concrete directive regarding which resistors to use where.
I have not exhaustively examined the correlations. I only tested this to the extent needed to prove to myself that resistors do appear to slightly influence the sound quality, and get some qualitative feeling for individual characteristics. The BOM recommendations evolved from that, but remain grounded in the concept of "value". If cost is no longer an object, the possibilities for experimentation with boutique parts ("platinum plating" as its sometimes called) are virtually endless - and, I would add, completely at the discrimination of the end user.
I have not exhaustively examined the correlations. I only tested this to the extent needed to prove to myself that resistors do appear to slightly influence the sound quality, and get some qualitative feeling for individual characteristics. The BOM recommendations evolved from that, but remain grounded in the concept of "value". If cost is no longer an object, the possibilities for experimentation with boutique parts ("platinum plating" as its sometimes called) are virtually endless - and, I would add, completely at the discrimination of the end user.
Thanks, Richard. Cost is certainly an object, and that is why I asked about the best bang for the buck in terms of resistors. As I'm generally a skeptic in terms of parts (aside from some capacitors...) I'll just experiment with what I have on hand. I put in some resistor sockets in a few locations where I have a few boutique parts and will report back if I find any magic from them.
Toaster and Mr. Onion, I appreciate your thoughts.
Carlp
Toaster and Mr. Onion, I appreciate your thoughts.
Carlp
Got it up and running. Richard advised 135 and 540 Ohm for R1 and 2.This was not enough gain. So after some fiddling around with the Excell sheet I now have 135 and 1K. Sound is still very harsh but it looks like the soundstage is more 3D than the VSPS300. Will leave it powered up for a couple of days and see what happens...
Greetings!
I have built a VSPS and have been using a 12VDC transformer and 2 FC caps 100uf at each of the +- power pins on an lm4562.
It works very nicely for around 15 or 20 minutes, then it sort of shuts down with a little bit of hum.
This is remedied by unplugging the power to the transformer and immediately plugging back in. Then the 'clock' is reset.
Help a moron out?
Kind Thanks!
paul
I have built a VSPS and have been using a 12VDC transformer and 2 FC caps 100uf at each of the +- power pins on an lm4562.
It works very nicely for around 15 or 20 minutes, then it sort of shuts down with a little bit of hum.
This is remedied by unplugging the power to the transformer and immediately plugging back in. Then the 'clock' is reset.
Help a moron out?
Kind Thanks!
paul
First thing I'd do is replace the op amp with a NE5532, see if that helps.
Second thing, if the problem persists, is check the supply voltages before and after the 20 minute failure. Try and isolate the problem to either the power supply or the phono stage itself.
As wirehead.be points out, the LM4562 probably needs ceramic bypass caps due to the high GBWP.
Second thing, if the problem persists, is check the supply voltages before and after the 20 minute failure. Try and isolate the problem to either the power supply or the phono stage itself.
As wirehead.be points out, the LM4562 probably needs ceramic bypass caps due to the high GBWP.
If only I knew how to model on LTSpice (it's on my list of things to learn though)
In the meantime, I'll rely on other peoples' knowledge and experience
If only I knew how to model on LTSpice (it's on my list of things to learn though)
In the meantime, I'll rely on other peoples' knowledge and experience
So what is the input impedance of your preamp?
Actually, in this application the NE5532 is better than an LM4562 - If you sim the circuit, the noise floor of the NE5532 is at -80dB; while the LM4562 is at -73dB. This is due to the fact that an MM cart is high impedance. The NE5532 behaves better in real life situations than the LM4562 in this case. Better yet, a low noise FET-based input would be even better due to lower voltage noise. (Analog has those, albeit in single versions.)
C=1/(2*PI*f*R)
R is the input impedance, use 22k if you don't know.
f is the bass cut off frequency, use 5 Hz.
C is the value of the coupling capacitor to use.
It works out to 2.2 uF. If your imput inpedance is higher, the capacitance can be smaller, and if it is smaller the capacitance should be larger.
No need to consult LTspice on this.