Im pretty sure im gonna end up with scratches trying that..
He is a good cat but hes really likes to chew up my silicone test leads and probe cables, more than once i have used oscilloscpe getting some crazy readings, spending hours fault finding, well probe cable was chewed through..🙀
He is a good cat but hes really likes to chew up my silicone test leads and probe cables, more than once i have used oscilloscpe getting some crazy readings, spending hours fault finding, well probe cable was chewed through..🙀
This is an interesting project and many thanks to member Wayne for making this happen! I am not into Vinyl and only barely scratched the surface during younger days before CDs took over but looks like quite a lot of resurgence lately. Someone in another thread tried to hook a phono output to a WIMM (DSP) but sounded awful. So I was thinking the internal phono stage and ADC are not good enough - better to use a highly quality external one. So to understand how to digitise properly to full scale level, what is the expected output from this phono preamp? There is some mention here of overload levels to consider. When will such conditions occur? I see commercial ones like around 200mV typically so what would overload levels look like? Appreciate any ideas or insights from experts🙂
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Output_Level = Input_Level * Gain
Gain is constant, and its value is written on the Pearl 3 schematic. Input_Level varies from cartridge to cartridge and from one recording to another.
Gain is constant, and its value is written on the Pearl 3 schematic. Input_Level varies from cartridge to cartridge and from one recording to another.
Which WiiM, exactly? What I'm seeing at the WiiM website is that the WiiM Pro, for example, uses a TI Burr-Brown Audio PCM1861 ADC. The catch here is that the specs for that chip shows ADC Sample Rate (fS) = 8 kHz to 192 kHz. The WiiM site reads, "Utilizing the TI Burr-Brown Audio PCM1861 ADC, the WiiM Pro Plus achieves a remarkable up to 192kHz/32-bit digital output." Nice switcheroo there. Utilizing this for our input, we can give you up to that output. Sneaky!
I'd like to think that they would set the sample rate at the full 192kHz, but if customers are getting sound that is not so great, the sample rate is likely set lower since it's not specified.
I'd like to think that they would set the sample rate at the full 192kHz, but if customers are getting sound that is not so great, the sample rate is likely set lower since it's not specified.
This makes a lot of sense. You'll have to spend some time playing back and recording loud records (or use a signal generator and a 'scope) to find the best level.
Not quite
This is the schematic, from post 1... the gain is confusing.
70db gain with 2.2 Kohms,
49db gain with 220 ohms
or
46 db with 2.2 Kohms.
Which is it?
And how about if you need a gain in between, say for a 1 mV Grado cartridge?
If my gain calculations are correct,
5 mV = ~52 db
1 mv = ~66 db
0.5 mv = ~72 db
0.3 mv = ~76 db
So, what is the correct resistance value for a 66 db gain? Is the gain equation ( in terms of resistance ) linear? -in which case I can figure it easily.
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Hello, I hooked up the umbilical cord and everything lights up nicely. I measure 2,32vdc across the 220r resistors. I have two questions before I proceed with a listening test: is it normal that all RCA connections ellicit a beep in continuity mode on the voltmeter? And should the jumpers be in or out for stink normal gain? Thank you
...I,m running into another question, as I am not sure what to do. I measure 2,3v across the 220R resistors (nr 27). i have the U1 that comes with the kit. Do I understand correctly that I need to replace the resistor with a 500-600R one and make sure I measure btw 0.44V and 1.1v?
I only have 750R resistors on hand. That should give me about 3mA for the U1, which is well in spec btw 2mA and 5mA. is there any downside to having less than more current?
I only have 750R resistors on hand. That should give me about 3mA for the U1, which is well in spec btw 2mA and 5mA. is there any downside to having less than more current?
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@tonyEE Yes, the gain equation is linear.
@raduschka RCA continuity depends on exactly how you are measuring, and continuity mode sometimes has an extra functionality on top of it, so the answer is, “it depends”. But I wouldn’t worry much at the moment.
What is stink gain? (Yes, I know it’s a typo 🙂 ) but do you want MM or MC? The silkscreen note printed right on the board says “jumper for low gain” One position is “jumper” (or closed) the other position is “open”, in reference to the pins. You can figure it out.
You don't need to adjust the resistors if you don't want to. If you have 750R to use, yes, do. If that gives you 3mA, fantastic, you are in the range, job done, congratulations!
@raduschka RCA continuity depends on exactly how you are measuring, and continuity mode sometimes has an extra functionality on top of it, so the answer is, “it depends”. But I wouldn’t worry much at the moment.
What is stink gain? (Yes, I know it’s a typo 🙂 ) but do you want MM or MC? The silkscreen note printed right on the board says “jumper for low gain” One position is “jumper” (or closed) the other position is “open”, in reference to the pins. You can figure it out.
You don't need to adjust the resistors if you don't want to. If you have 750R to use, yes, do. If that gives you 3mA, fantastic, you are in the range, job done, congratulations!
Pearl 3 gain formula as provided by Wayne is in the build guide in post #1.
I have a scope and ordered a quasimodo v4 board and parts for it. For now I have the snubber cap across the secondaries in place, but that is all. I soldered it in before i realised I needed to calculate the resistance. Actually both snubber caps are in place on each rail). Can I ignore them and use the pearl 3 with them in for now?
Have a resistor anywhere around 47-82 ohms? Use it and be happy. If not, you can still use it with just the caps soldered in the board with no ill effect.
I actually do, I bought a number of values btw 20r and 400R, just in case. i really want to do the quasimodo thing now, just for the sake of it, but glad to know it's not as precise as I am 🙂 I am sure I will get back here for help once I get the jig up and running. thank you
...also I have a turntable with no separate ground wire, so it is grounded through the RCAs presumably. I wired the ground lug in the preamp just the same, as mentioned in the pdf., in touch with the case and running two wires from it to the PCBs. I am wondering now if I should have adapted the grounding scheme to my situation.
Regarding power supply for pearl3 what do you think about my approach.
The external psu consists of dual toroids, dual regulators sigma22 regulators, theese feed through umbilical cable to phono,
Phono has two per side common mode ckokes and decoupling, this then feeds four 10000uf capacitors, they are bypassed with film type caps, this again feeds the pearl board regulators.
I chose a chain of filtering, and choose large capacitors for low impedance.
This is done by heart , im no engineer, the sigma22 regulators seem happy about the large capacitors, no oscillation, total dc resistance from reg board to pearl board is 7 ohm, mostly the chokes.
I have tried measuring af noise, but levels are to low for my gear. Could be rf and other stuff
The external psu consists of dual toroids, dual regulators sigma22 regulators, theese feed through umbilical cable to phono,
Phono has two per side common mode ckokes and decoupling, this then feeds four 10000uf capacitors, they are bypassed with film type caps, this again feeds the pearl board regulators.
I chose a chain of filtering, and choose large capacitors for low impedance.
This is done by heart , im no engineer, the sigma22 regulators seem happy about the large capacitors, no oscillation, total dc resistance from reg board to pearl board is 7 ohm, mostly the chokes.
I have tried measuring af noise, but levels are to low for my gear. Could be rf and other stuff
