Hello!
I'm looking to build a modular 2-channel DJ mixer. By modular I mean that, if I understand concept of audio-electronics, every module(pre-amp, EQ isolators etc.) will go on a separate PCB Stripboard because every module has an input and an output and every output is connected to the next input and so on.
So, I'm looking for some help in finding all the schematics I need and of course help with everything else on this project.
So, first to tell, everything is going to be inside a wooden box with which is
350L/450H/150D(mm) the wood is 10mm thick.
I need help with finding/creating the following schematics so any help would be appreciated, I will be using EaglePCB for creating the schematics:
- RIAA phono pre-amp schematics
- EQ isolators schematics with low-pass to be <300Hz, mid from 300-4000Hz and hi-pass to be 4000Hz and upwards
Thanks in advance and I'm looking forward to finishing this project and posting all the pictures and sound tests! Cheers!
I'm looking to build a modular 2-channel DJ mixer. By modular I mean that, if I understand concept of audio-electronics, every module(pre-amp, EQ isolators etc.) will go on a separate PCB Stripboard because every module has an input and an output and every output is connected to the next input and so on.
So, I'm looking for some help in finding all the schematics I need and of course help with everything else on this project.
So, first to tell, everything is going to be inside a wooden box with which is
350L/450H/150D(mm) the wood is 10mm thick.
I need help with finding/creating the following schematics so any help would be appreciated, I will be using EaglePCB for creating the schematics:
- RIAA phono pre-amp schematics
- EQ isolators schematics with low-pass to be <300Hz, mid from 300-4000Hz and hi-pass to be 4000Hz and upwards
Thanks in advance and I'm looking forward to finishing this project and posting all the pictures and sound tests! Cheers!
Nearly half the threads on this board require either 2sk170 or lateral fets also available only with a ticket to Japan. Try to buy some! And the parts count is rediculous in this day.
Furthermore your wooden box is only going to keep out the radio inteference if you live in Nova Zembla. For a MM cartridge you need 50x gain. If you're using ceramic cartridge with .5 v out you're destroying the very records you're playing with the 5 g weight. My Mother's ceramic cartridge wonder player certainly did.
I have a "legendary" dynaco PAS2 vacuum tube preamp, and my op amp disco mixer sounds just as good IMHO with $.38 parts and 1/20th the electricity. It took a lot of fiddling to get the hiss & hum out of the RA-88a, but less than $20 in parts.
Good slide pots are nearly $10 apiece, so starting with a failed kit like above which I purchased for $15 is a great start. The steel box and 6 pots were great, the circuit wasn't too bad but the packaging guy was an idiot. I've seen them on E-bay for $30.
Isolating the case ground from the analog input ground was a great start to reducing hum. Moving the hummy power transformer out of the box and getting the 120 vac power switch out too were key to eliminaing hum. And changing the op amps from hissy 4558 to 33078 eliminated the hiss. See the gory details, as well as the compact RIAA stage on this thread: Improving a "Disco mixer" to mid-fi performance - diyAudio
The 8 part mag phono circuit is so compact, you might be able to cram it in a commercial non-RIAA mixer like a Peavey PV8 or similar. the 4558's are fine at gain 1 to 10, but for the RIAA circuit a quieter op amp is required. Besides 33078 another quiet amp you might be able to get is NJR2068.
If you want to bare board build and a drawing easier to read, the RIAA circuit on the LM4562 datasheet from TI may be your ticket. Records only have 55 db signal/noise so you don't need ultra parts to get the noise level below that. Op amps are perfectly capable, and so compact! Use a socket so you can try different ones. Don't forget the PS bypass ceramics close by the op amp, also the 22 pf around the feedback resistor to reduce the tendency to oscillate. Use COG ceramic for the RIAA cap.
For more simple ciruits out of parts you can buy, see this thread: WANTED: schematic for a 9 V-DC operating RIAA/pre-amp In stead of 2 9 v batteries you can use a 16 v wall transformer, 2 zeners, two resistors, two capacitors as I used in my RA-88a detailed above.
Have fun.
Furthermore your wooden box is only going to keep out the radio inteference if you live in Nova Zembla. For a MM cartridge you need 50x gain. If you're using ceramic cartridge with .5 v out you're destroying the very records you're playing with the 5 g weight. My Mother's ceramic cartridge wonder player certainly did.
I have a "legendary" dynaco PAS2 vacuum tube preamp, and my op amp disco mixer sounds just as good IMHO with $.38 parts and 1/20th the electricity. It took a lot of fiddling to get the hiss & hum out of the RA-88a, but less than $20 in parts.
Good slide pots are nearly $10 apiece, so starting with a failed kit like above which I purchased for $15 is a great start. The steel box and 6 pots were great, the circuit wasn't too bad but the packaging guy was an idiot. I've seen them on E-bay for $30.
Isolating the case ground from the analog input ground was a great start to reducing hum. Moving the hummy power transformer out of the box and getting the 120 vac power switch out too were key to eliminaing hum. And changing the op amps from hissy 4558 to 33078 eliminated the hiss. See the gory details, as well as the compact RIAA stage on this thread: Improving a "Disco mixer" to mid-fi performance - diyAudio
The 8 part mag phono circuit is so compact, you might be able to cram it in a commercial non-RIAA mixer like a Peavey PV8 or similar. the 4558's are fine at gain 1 to 10, but for the RIAA circuit a quieter op amp is required. Besides 33078 another quiet amp you might be able to get is NJR2068.
If you want to bare board build and a drawing easier to read, the RIAA circuit on the LM4562 datasheet from TI may be your ticket. Records only have 55 db signal/noise so you don't need ultra parts to get the noise level below that. Op amps are perfectly capable, and so compact! Use a socket so you can try different ones. Don't forget the PS bypass ceramics close by the op amp, also the 22 pf around the feedback resistor to reduce the tendency to oscillate. Use COG ceramic for the RIAA cap.
For more simple ciruits out of parts you can buy, see this thread: WANTED: schematic for a 9 V-DC operating RIAA/pre-amp In stead of 2 9 v batteries you can use a 16 v wall transformer, 2 zeners, two resistors, two capacitors as I used in my RA-88a detailed above.
Have fun.
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For a DJ project of today, I wouldn't dream of using anything but opamps in all stages except the PA. Modern opamps are fully capable of meeting all but the crasiest asylum specs. Ease of design and component count will outperform anything, and particularly if you build on strip boards. A google search should bring you several designs, including most of the "normal" gadgets one might think of including....
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