I built Jan Lodstrom's reMUS phono-line preamp from a Sound Practices article at an old and it just won't work. I get no sound out of it! 
I have checked all the components and connections and everything is kosher and the valves are all either new or NOS tested by the retailer. I have attached the schematic and components list to this message.
I decided to try and figure out what stage of the pre-amp is problematic. I have established that the line stage is not working. (I have not checked phono yet so not sure, but let's fix this for the time being and worry about the rest later.) I did this by running my ipod straight into the point that I have labelled "Input" on the schematic.
Could anyone please suggest where I could start looking for problems? My understanding of electronics is limited and this project and the research around it in part serves the purpose of learning so that I make more ambitious things in the future, so please bear with my ignorance.
Some facts that may or may not be significant:
1. Instead of the suggested B+ supply, I am using an RCRCRC filter after bridge. I am getting ~270-280 V DC out of it.
2. My power transformer is a bit too powerful for my purposes, so I had to kill a lot of voltage with the filter. To get to he 270-280V there was a fair deal of trial and error with different resistance values. This meant that I had to run the pre-amp at voltages up to 370 V a few times, all of which for less than one minute. Is there any way I could have damaged anything by doing this?
3. Initially, I had forgotten the C11 capacitor and ran this a few times without it. Again, could I have damaged anything as a result of this?
4. Instead of the suggested 6V supply for the heaters I am using a regulated supply designed by Wavebourne. I am getting 12.85 V DC out of that. (I have of course wired the heaters accordingly.)
5. Although the schematic calls for 3 ECC83s and two ECC82s, I have used (in a V1-V5 order) two ECC83s followed by one ECC81 before the volume pot, followed by an ECC82 at the first stage of the line and an ECC81 at the end. I did this following the suggestions in the article accompanying the schematic, which read:
"The preamp uses five tubes, each of which handles both channels. Two 12AX7s provide the phono amplifications with RIAA equalisation. A 12AT7 is used for an isolation stage and driver for the volume control and tape output. The line stage uses a 12AU7 as a voltage amplifier direct coupled to a 12AT7 cathode follower to provide a solid low impedance output"
6. I have been feeding this into the "CD input" of a solid state amp to test.
Many thanks,
Nikos
I have checked all the components and connections and everything is kosher and the valves are all either new or NOS tested by the retailer. I have attached the schematic and components list to this message.
I decided to try and figure out what stage of the pre-amp is problematic. I have established that the line stage is not working. (I have not checked phono yet so not sure, but let's fix this for the time being and worry about the rest later.) I did this by running my ipod straight into the point that I have labelled "Input" on the schematic.
Could anyone please suggest where I could start looking for problems? My understanding of electronics is limited and this project and the research around it in part serves the purpose of learning so that I make more ambitious things in the future, so please bear with my ignorance.
Some facts that may or may not be significant:
1. Instead of the suggested B+ supply, I am using an RCRCRC filter after bridge. I am getting ~270-280 V DC out of it.
2. My power transformer is a bit too powerful for my purposes, so I had to kill a lot of voltage with the filter. To get to he 270-280V there was a fair deal of trial and error with different resistance values. This meant that I had to run the pre-amp at voltages up to 370 V a few times, all of which for less than one minute. Is there any way I could have damaged anything by doing this?
3. Initially, I had forgotten the C11 capacitor and ran this a few times without it. Again, could I have damaged anything as a result of this?
4. Instead of the suggested 6V supply for the heaters I am using a regulated supply designed by Wavebourne. I am getting 12.85 V DC out of that. (I have of course wired the heaters accordingly.)
5. Although the schematic calls for 3 ECC83s and two ECC82s, I have used (in a V1-V5 order) two ECC83s followed by one ECC81 before the volume pot, followed by an ECC82 at the first stage of the line and an ECC81 at the end. I did this following the suggestions in the article accompanying the schematic, which read:
"The preamp uses five tubes, each of which handles both channels. Two 12AX7s provide the phono amplifications with RIAA equalisation. A 12AT7 is used for an isolation stage and driver for the volume control and tape output. The line stage uses a 12AU7 as a voltage amplifier direct coupled to a 12AT7 cathode follower to provide a solid low impedance output"
6. I have been feeding this into the "CD input" of a solid state amp to test.
Many thanks,
Nikos
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