Hello Forum,
Last year I built a modulus-86 from Neurochrome. It was a great project and @tomchr was very helpful, enabling a person like me without a lot of electronics knowledge to build a working amp.
I didn't have a proper preamp to run the mod-86 with, only a cheap mini bluetooth input selector and volume control. None of my other amps have outputs for an external power amp. Problem: it doesn't get very loud. But I guess I can change this by allowing more gain either via the resistors on the modulus boards or with a universal buffer. First imression was still good, it sounded more precise than before with an old NAD 3020e. The big disappointment came when I compared it with a 1992 Creek 4040s3. The modulus with the chinese preamp sounded -surprise- awful in comparison. I expected it to be worse than the Creek but it was no match at all. The creek is to this day the best amp I ever owned, the "size of the room", the location of the instruments and the warmth of the sound are just fantastic.
So of course the next step would be a diy preamp, preferrably from Tom. I ordered the input selector and the preamp psu to start with and want to add one of his universal buffers to provide a balanced connection to the power amp. Got the parts from mouser and assembled the input selector, switch and volume control.
So I started planning an enclosure and realised that the psu, volume control, input selector and buffer fit into a really small box. Now I wonder if it would make sense to build one enclosure for both, preamp and modulus. The advantage would be that I have to buy fewer connectors if I can wire it internally instead. I could also add an arduino for the remote contol, stepper motors for volume, a hifiberry dac and a display in the same box.
A few questions about the wiring:
What kind of cable would be best to connect the RCA sockets to the input selector? The RCA sockets to solder straight onto the boards are all totally unshielded. I assume I want to keep the wires as short as possible?
Is the length of the ribbon cable for the volume control a problem? If it is a problem I'll get the volume pot near the input selector and connect it with a long rod to the volume knob. Otherwise the volume knob goes into the front, I guess that would make the assembly easier.
Although I've seen quite a few now, please share pictures of your (Neurochrome) preamp designs, just to get more ideas.
Thanks for your time
Stefan
Last year I built a modulus-86 from Neurochrome. It was a great project and @tomchr was very helpful, enabling a person like me without a lot of electronics knowledge to build a working amp.
I didn't have a proper preamp to run the mod-86 with, only a cheap mini bluetooth input selector and volume control. None of my other amps have outputs for an external power amp. Problem: it doesn't get very loud. But I guess I can change this by allowing more gain either via the resistors on the modulus boards or with a universal buffer. First imression was still good, it sounded more precise than before with an old NAD 3020e. The big disappointment came when I compared it with a 1992 Creek 4040s3. The modulus with the chinese preamp sounded -surprise- awful in comparison. I expected it to be worse than the Creek but it was no match at all. The creek is to this day the best amp I ever owned, the "size of the room", the location of the instruments and the warmth of the sound are just fantastic.
So of course the next step would be a diy preamp, preferrably from Tom. I ordered the input selector and the preamp psu to start with and want to add one of his universal buffers to provide a balanced connection to the power amp. Got the parts from mouser and assembled the input selector, switch and volume control.
So I started planning an enclosure and realised that the psu, volume control, input selector and buffer fit into a really small box. Now I wonder if it would make sense to build one enclosure for both, preamp and modulus. The advantage would be that I have to buy fewer connectors if I can wire it internally instead. I could also add an arduino for the remote contol, stepper motors for volume, a hifiberry dac and a display in the same box.
A few questions about the wiring:
What kind of cable would be best to connect the RCA sockets to the input selector? The RCA sockets to solder straight onto the boards are all totally unshielded. I assume I want to keep the wires as short as possible?
Is the length of the ribbon cable for the volume control a problem? If it is a problem I'll get the volume pot near the input selector and connect it with a long rod to the volume knob. Otherwise the volume knob goes into the front, I guess that would make the assembly easier.
Although I've seen quite a few now, please share pictures of your (Neurochrome) preamp designs, just to get more ideas.
Thanks for your time
Stefan
My thoughts on preamps are available here: https://neurochrome.com/pages/the-ultimate-guide-to-preamp-design
Keep mains wiring and signal wiring as far apart as your chassis allows. So push the power supply off to one side and the input selector and volume control off to the other side (and towards the rear of the chassis). If you're using a motorized pot, it's often advantageous to place it by the input selector and run a shaft extension to the front panel.
I recommend using the ALPS RK271-series ("Blue Velvet") pot. If that doesn't suit your fancy, the Khozmo attenuators are excellent. There are other solutions as well. Until I offer a different solution (which I am considering) I'll point to those options.
Tom
Keep mains wiring and signal wiring as far apart as your chassis allows. So push the power supply off to one side and the input selector and volume control off to the other side (and towards the rear of the chassis). If you're using a motorized pot, it's often advantageous to place it by the input selector and run a shaft extension to the front panel.
I recommend using the ALPS RK271-series ("Blue Velvet") pot. If that doesn't suit your fancy, the Khozmo attenuators are excellent. There are other solutions as well. Until I offer a different solution (which I am considering) I'll point to those options.
Tom
Using the ALPS pot as per the BOM. I thought I'll try 2 individual pots to get a balance control but I decided to go with the normal Volume control with one stereo pot. On low volume this would always be fiddly. Looking forward to see what you're working on!
I'm really considering to build one enclosure for preamp and mod-86, I think I can keep the mains wiring away from the signal wiring. Are standard coax cables like from an rca cable OK to connect the RCA sockets to the input selector?
I'm really considering to build one enclosure for preamp and mod-86, I think I can keep the mains wiring away from the signal wiring. Are standard coax cables like from an rca cable OK to connect the RCA sockets to the input selector?