You wrote that you have used the P3 in MC-setting (high gain). Did you experience the difference in voltage gain?
Did it play a lot louder using this setting (vol pot has to be set very low for normal listening level)?
If not then there is something fundamental wrong with the amp.
Did it play a lot louder using this setting (vol pot has to be set very low for normal listening level)?
If not then there is something fundamental wrong with the amp.
In high gain mode, it indeed gained a lot of volume. It appears to be amplifying okay. That said, it sound like it has an aggressive low pass filter at say 4khz (just a random guess). I tested all the parts before soldering them in, so the problem seems to be something I've done rather than fault components.
Wellerman,
Thanks for the insight on the Ortofon and the suggested settings.
I did the boards in parallel, so it's absolutely possible I made the same error on both. I'll check the resistor values in the RIAA sections and C15 later today.
I really appreciate the guidance.
Thanks for the insight on the Ortofon and the suggested settings.
I did the boards in parallel, so it's absolutely possible I made the same error on both. I'll check the resistor values in the RIAA sections and C15 later today.
I really appreciate the guidance.
In the picture it seems you have DIP 1 activated, which would be 1k with 1nf in series. Not the right load for an mm I think. Switch dip 2 to on for the capacitance (or dip 3, try which sounds best) and leave the rest set to off, so you'll have the default 47k load.
Hello AkimoSD,
Wellerman is right. You have the 47KOhm as R12 at the input to ground in the PEARL3 (nothing to switch)
.
ORTOFON recommends a capacitance of 150 - 300pF (because the ORTOFON 2M Bronze is a MovingMagnet cartridge).
So you should switch in C11 (220 pF) or you could try C10 (100pF) and C11 (220pF) which would add to 320pF (slightly above the recommended value).
The sensitivity of your PEARL3 should be set to 'low'
I would for sure check my part values in the RIAA-section. R13 / C3 / C12 / R28 should also be checked (this is the high frequency
equalization in the RIAA -network).
Only some thoughts
Cheers
Dirk😉
Wellerman is right. You have the 47KOhm as R12 at the input to ground in the PEARL3 (nothing to switch)
.
ORTOFON recommends a capacitance of 150 - 300pF (because the ORTOFON 2M Bronze is a MovingMagnet cartridge).
So you should switch in C11 (220 pF) or you could try C10 (100pF) and C11 (220pF) which would add to 320pF (slightly above the recommended value).
The sensitivity of your PEARL3 should be set to 'low'
I would for sure check my part values in the RIAA-section. R13 / C3 / C12 / R28 should also be checked (this is the high frequency
equalization in the RIAA -network).
Only some thoughts
Cheers
Dirk😉
I use Ortofon 2M Black LVB250. I started with only the 47k resistor. This sounded too bright for my taste.
220 pF made a big difference with an "ear-friendly" sound with still a lot of treble and high "resolution" of details.
220 pF made a big difference with an "ear-friendly" sound with still a lot of treble and high "resolution" of details.
@AkimoSD -- check the orientation of the DIP switches. They appear to be reversed. It's hard to see but worth checking.
First, I can't tell you how much I appreciate all of your help on this.
To get caught up:
- I've confirmed that C15 has appropriate circuit continuity to U1, and no inappropriate continuity between its two pads (i.e. no horrible blob of solder connecting them).
In all tests, I have the low-mode jumper in place. Without it, the distortion is fierce.
- On the idea that I reversed the installation of the DIP switches, I suspect that this is correct, but still gives me puzzling, but different results:
- If I set it for 47k and 220pF, the high frequencies are there, but I also get incredible levels of distortion (possibly overloading the input transistors?). If I remove some of the resistance, the distortion begins lessening, but the high frequencies drop out completely. The capacitance doesn't seem to have any effect. I'm guessing this is due to the resistance issue overwhelming it. I only avoid distortion at very low load levels, and I only get high frequencies at very high load levels. There's nothing close to an overlap.
My next step will be to confirm that I have the right resistors in the right places in the load stack.
Thanks again
To get caught up:
- I've confirmed that C15 has appropriate circuit continuity to U1, and no inappropriate continuity between its two pads (i.e. no horrible blob of solder connecting them).
In all tests, I have the low-mode jumper in place. Without it, the distortion is fierce.
- On the idea that I reversed the installation of the DIP switches, I suspect that this is correct, but still gives me puzzling, but different results:
- If I set it for 47k and 220pF, the high frequencies are there, but I also get incredible levels of distortion (possibly overloading the input transistors?). If I remove some of the resistance, the distortion begins lessening, but the high frequencies drop out completely. The capacitance doesn't seem to have any effect. I'm guessing this is due to the resistance issue overwhelming it. I only avoid distortion at very low load levels, and I only get high frequencies at very high load levels. There's nothing close to an overlap.
My next step will be to confirm that I have the right resistors in the right places in the load stack.
Thanks again
If the switches are reversed, you'd have to switch "off" nr 2 (or 3 whichever gives you 220 pF) and switch "on" the rest.
I would turn off all switches. Had similar issues with a friends P3. Problem was that cable capacitance was so high he needed not any additional.
With Bias I didnt talk about RIAA components.
With Bias I didnt talk about RIAA components.
@AkimoSD
Please verify and set all dip switches to OFF. (away from the numbers)
This will work regardless of package orientation.
Please verify and set all dip switches to OFF. (away from the numbers)
This will work regardless of package orientation.
6l6 is right, I was overthinking this a little. On=on and off=off regardless of the orientation. Hopefully this works when you try it monday.
@AkimoSD: 6L6 and Wellerman are, of course, correct -- for troubleshooting purpose all of the DIP switches should be disabled. Once you correct any issues and return to fine-tune your cartridge, however, you should remember to reverse their order -- the progression of 1-8 in Randy's table will actually read 8-1 in your build.
I got a chance to do a drop more work this morning with confidence in the following:
- Q9 is biased to .44 volts (with R27 at 680R)
- There continues to be no combination of load settings that approaches usability:
Distortion goes away at 250R or lower
Upper and upper-mid frequencies become usable at 47K (even at 8.2k, they are muffled to the point of the amp being unusable)
There is nothing even close to an overlap range in which both criteria are usable.
I, therefore, suspect that there is an error somewhere else in my build.
P.S. Thanks to Wellerman etal for the guidance on the flipped dip switches. I've taken that into account with the info above.
P.P.S. All the input JFET's show good continuity, but I had trouble soldering them. Would I be getting results like this if I had overheated one or more during the build? I wore an ESD strap when handling them, but took a LONG time while soldering them, exposing them to more heat than usual.
- Q9 is biased to .44 volts (with R27 at 680R)
- There continues to be no combination of load settings that approaches usability:
Distortion goes away at 250R or lower
Upper and upper-mid frequencies become usable at 47K (even at 8.2k, they are muffled to the point of the amp being unusable)
There is nothing even close to an overlap range in which both criteria are usable.
I, therefore, suspect that there is an error somewhere else in my build.
P.S. Thanks to Wellerman etal for the guidance on the flipped dip switches. I've taken that into account with the info above.
P.P.S. All the input JFET's show good continuity, but I had trouble soldering them. Would I be getting results like this if I had overheated one or more during the build? I wore an ESD strap when handling them, but took a LONG time while soldering them, exposing them to more heat than usual.
Hello AkimoSD,
you shouldn:t switch any resistor-load in. Only switch the 220pF -cap to 'on'. All others 'off'.
You can check the continuity of your soldering by measuring from the JFet - legs to the next part on the pcb (check schematic).
Should be very low resistance (Ohm).
Greets
Dirk
you shouldn:t switch any resistor-load in. Only switch the 220pF -cap to 'on'. All others 'off'.
You can check the continuity of your soldering by measuring from the JFet - legs to the next part on the pcb (check schematic).
Should be very low resistance (Ohm).
Greets
Dirk
Dirk,
Thanks for the suggestions. I have tried the setting you specify. With that setting, the high frequencies are present, but the distortion is incredible. It sounds like an amp thrown into massive overload.
Regarding the JFETS, I have continuity, but am wondering if I may have fried the junctions by overheating during soldering.
Thanks for the suggestions. I have tried the setting you specify. With that setting, the high frequencies are present, but the distortion is incredible. It sounds like an amp thrown into massive overload.
Regarding the JFETS, I have continuity, but am wondering if I may have fried the junctions by overheating during soldering.