Need to listen/capture from vinyl? Are you questioning the quality of that dusty 1970’s phono receiver you found in the basement?
If you’re a musician, it’s likely you have a highend Pre/Audio interface at your disposal. With minimal cost & effort you can use the Hi-Z instrument gain stage as a pristine Phono preamp (with specs/results that the HIFI world have wet dreams about) . You not only gain the added benefits of a quality gain stage, most turntable outputs are also balanced by nature. A simple conversion cable is all that is needed.
Most phono cartridges are spec’d to work with a load around 47k/250pf. With that in mind you need to recreate that scenario when you plug your turntable into your preamp. A simple resistor will give you the 47k impedance & the cable length alone should cover your capacitance. If you know your cartridge is wanting to see a higher capacitance, then you’re an audio geek. Adding a CAP to the chain will have you covered.
All you have left to deal with is the RIAA curve once you get the signal into your DAW. Vacuumsound has created a great VST/AU plugin RIAA – phono equalization that will accurately give you the RIAA curve needed. I have compared the curve/phase response against the analog counter part & the plugin is tits on. I’ve supplied a schematic & build pictures below. (FYI for those wondering why my cable is using 2 resistors? I’m using a 50k load with my deck)
BOM
- 2x 1/4 TRS
- 2x RCA Phono
- 1x 47k resistor
- Single pair shielded cable (11ohm digital audio cable is best)
- Ground lug
riaa_vst_win_v1.1 riaa_au_ub_v1.0.1 riaa_vst_osx_v1.0 riaa_vst_x64_v1.1
I smell some vinyl programs for Nebula being made… It would be great if You could capture actual vinyl through needle sound.. not only turntable circuit.. (I think AlexB Vinyliser is only the ciruit but I`m not sure..)
Wasn’t aware of that, I’m not planning on creating any vinyl nebula programs at the moment. I agree getting a vinyl cut with the sweep tone would be the way to go. The physics of the stylus/tonearm is most of the color.
Hi Eric, I’m on my way for doing this very nice adapter. I wonder what hapens if I do it with an xlr adapter so I can use a mic input on a desk, would I have to change the value of the 47K resistor? And would you know what to do if my turntable (an old Thorens) has no separate ground connector? Would I need to find a way to get the ground from somwhere inside the turntable’s rather simple electrical guts, or should I leave the signal floating or maye add a transformer? Thanks for answering, best regards!
Mitch
XLR’s are fine, but microphone input impedance is to low. It should really be connected to a line input. As far as grounding goes just leave it floating. If you have any ground hum issues then you can try attaching the ground to the negative ring of the cable, or finding a ground elsewhere on the turntable.
Hi! thank you for the reply and for your cool internet site!!
A question regarding ground: “try attaching the ground to the negative ring of the cable”,
do you mean the “-” phase of the symetrical instrument input which happens to be also the ground of the cinch on the turntable side?
Regarding impedance, maybe I will try to find a transformer to match the impedance between the turntable output (with 47K adapter) and the mic preamp input, I would really like to to try some preamps to see how the sound changes!
A transformer would also help in case the +48v is switched on accidentaly!
regards,
Mitch
“do you mean the â-â phase of the symetrical instrument input which happens to be also the ground of the cinch on the turntable side?”
Yes, exactly.
A transformer could do the job. Would have to think about that a bit to figure out a good ratio. An email to Jensen or a few over at GroupDIY would know better then I. Will be a transformer+shunt+zobel.