With record on the platter, tube line stage and tube amps warmed up I set the needle down carefully on the record. No hum but rather distorted sounding. After trying different cartridges it was still distorted and my hopes were somewhat let down.
I pulled out a record I knew was in great shape because it had only been played one time in its life still no joy. I played with the gain switches still no help. I pulled out the input opamp a OPA2134 and replaced it with the only thing I had laying around which was a TL082 and fired it up again and it wasn't distorted but it sounded kind of lifeless. I surely shouldn't be overdriving it with a Pickering XV-15 D1200 cartridge which should output 5mv.
What could I have done wrong? Power supply measured correctly at +15.16 & -15.12 voltage on opamp pins 4 & 8 is correct
Any ideas?
I pulled out a record I knew was in great shape because it had only been played one time in its life still no joy. I played with the gain switches still no help. I pulled out the input opamp a OPA2134 and replaced it with the only thing I had laying around which was a TL082 and fired it up again and it wasn't distorted but it sounded kind of lifeless. I surely shouldn't be overdriving it with a Pickering XV-15 D1200 cartridge which should output 5mv.
What could I have done wrong? Power supply measured correctly at +15.16 & -15.12 voltage on opamp pins 4 & 8 is correct
Any ideas?
You need to separate and isolate the cause. First, feed your amp with a reliable source: a PC, a cell phone, a radio tuner, and be sure the trouble is or not in the power stage.
Check R6, R7, R11, R14 and the setting of the switches on R12 and R13. All them fixes the gain of the stages.
Checked supply voltages as I mentioned. I also checked for proper parts placement on the board. I also checked R6,7,11,14 along with R12 and R13..
Ohmed everything out
Yes , have schematics
Ohmed everything out
Yes , have schematics
Maybe double check the electrolytic caps are installed for correct polarity?
Is this a new build, PP-4?
Is this a new build, PP-4?
There might be one of two causes:
1. Parasitic oscillation. Prevent it by placing a 100 nF ceramic capacitor between pins 4 and 8 directly on the PCB track side below the chip.
2. DC shift. Connect a 100 uF/25 V capacitor in series with R6 and R11/12/13.
1. Parasitic oscillation. Prevent it by placing a 100 nF ceramic capacitor between pins 4 and 8 directly on the PCB track side below the chip.
2. DC shift. Connect a 100 uF/25 V capacitor in series with R6 and R11/12/13.
Photographs of the top/bottom of board? IIRC PP4 let's you set gain, impedance and capacitance. How have set those?
After assembling the version 4 I double checked the resistor values and placement along with capacitor values and correct orientation of the caps. So I have correct resistors and capacitors installed correctly.
I have set the gain at 38 db and I have tried different gain settings. The impedance is set at 47K and I haven't soldered in any capacitors to help match the capacitance of the phono cartridge as I'm not sure what to purchase and solder in the unused pad for this purpose. Capacitance of 0-200p is marked on the board on these 2 pads.
I still have a doubt: the board in question, worked properly some time ago or it is completely new and first use?
Photos please. Well, lit and in focus. We’ll help you figure this out.
Also, do you have another known good cartridge you can try?
Also, do you have another known good cartridge you can try?
I think I found the problem. The turntable an Audio Technica AT-LP120USB has an internal built in phono preamp and a switch to allow either phono level out or line level out. It looks like the cartridge output always feeds the internal preamp and the switch controls the output allowing either the cartridge output or preamp output. It looks like the switch was the problem. It looks like either the abuse I subject it to or the cleaning has cleaned up the output.
The output from the cartridge via the hair like wires is soldered onto a PC board. I think I should purchase a decent set of line level cables and parallel the cable to where it feeds the internal preamp to allow myself an un switched output in which to feed my preamp. I don't want to take the board out because the wife wants me to transfer all the albums to the computer via the USB output that the board has.
The question I have left is there is a surface mount resistor that is soldered across the left and right ground trace. One side of the resistor is attached to the left channel ground and the other side of the resistor is attached to the right channel ground. The value of the resistor is approximately 115 or so ohms. What does this resistor do?
The output from the cartridge via the hair like wires is soldered onto a PC board. I think I should purchase a decent set of line level cables and parallel the cable to where it feeds the internal preamp to allow myself an un switched output in which to feed my preamp. I don't want to take the board out because the wife wants me to transfer all the albums to the computer via the USB output that the board has.
The question I have left is there is a surface mount resistor that is soldered across the left and right ground trace. One side of the resistor is attached to the left channel ground and the other side of the resistor is attached to the right channel ground. The value of the resistor is approximately 115 or so ohms. What does this resistor do?
This was the first use of the board which I recently put together for use with a used ebay turntable I purchased also recently which was used the first time with the phono preamp board. See post above this one.