At least I can show you about the simplistic Riaa. It depends a lot on the build for harmonic noise, two box is better, on the gnd execution also. This is a typical measurement I get from the MC 56dB version. The particular chart is from a build with a V1 feeding it from very near, common to both channels with resistive Vref. The TX and rectification, main cap filter, are in another box. 0.02% THD at 0.5mV nominal input. 0dB=1VRMS. Ignore the 16kHz line, its an artifact that I get some times from my card and software.
Attachments
Fun you shall have, sir.
Regarding your noise issue, the simplistic RIAA on its associated regulator proves me besides being highly musical- good favors on classical music. The dark-as-night background can be explained for the best part by the quality of regulator and for a small part by the measures I took filtering common mode noise and using soft recovery diodes. The schematic is in this thread.
Regarding your noise issue, the simplistic RIAA on its associated regulator proves me besides being highly musical- good favors on classical music. The dark-as-night background can be explained for the best part by the quality of regulator and for a small part by the measures I took filtering common mode noise and using soft recovery diodes. The schematic is in this thread.
I guess you will find it adequate in your system, after paying the required attention to grounding and isolation from power transformer's hum field etc. That chart is about the highest gain version, i.e. at its most noise.
What kind of cartridge will you be using, so to choose the correct phono gain version? You will need a 0.3-0.5V input sensitive for nominal power output amp so to have all your volume if with a unity gain buffer as control unit. That leads to a tube amp choice most easily and it matches well for tone.
What kind of cartridge will you be using, so to choose the correct phono gain version? You will need a 0.3-0.5V input sensitive for nominal power output amp so to have all your volume if with a unity gain buffer as control unit. That leads to a tube amp choice most easily and it matches well for tone.
Adequate?
You folks have put in long hard work. I am going to use your creations as a reference to compare my efforts to. I hope to come close with vacuum tubes. Tubes sound nice but their noise floor seems to be higher.
The current cartridge is a Moving Magnet that will take the lowest gain version of your Riaa amp. The line stage is a home cooked grounded cathode 9AU7 with a gain some where near 12. The power amp is not the norm. The power amplifier is a pair of triode wired 837 RCA JAN transmitter tubes. They have a really cool blue glow about them. The output transformers are custom, 5000 ohm to 300 ohm. The headphones are Sennheiser 600D’s. To help with noise the transformers, (power and separate filament) rectifiers and first stage capacitors are boxed away from the amplifiers. The B+ and heaters all are regulated and installed at the amplifiers. The stepped attenuators do not through away too much signal. The line stage and power amplifier are very quite to my ears. The tube Riaa has room to improve. The PC, soundcard and software test system you use looks interesting.
I am looking foreword to building your Salas Simplistic Riaa and DISCO your implementation of the power supply.
DT
All just for fun!
You folks have put in long hard work. I am going to use your creations as a reference to compare my efforts to. I hope to come close with vacuum tubes. Tubes sound nice but their noise floor seems to be higher.
The current cartridge is a Moving Magnet that will take the lowest gain version of your Riaa amp. The line stage is a home cooked grounded cathode 9AU7 with a gain some where near 12. The power amp is not the norm. The power amplifier is a pair of triode wired 837 RCA JAN transmitter tubes. They have a really cool blue glow about them. The output transformers are custom, 5000 ohm to 300 ohm. The headphones are Sennheiser 600D’s. To help with noise the transformers, (power and separate filament) rectifiers and first stage capacitors are boxed away from the amplifiers. The B+ and heaters all are regulated and installed at the amplifiers. The stepped attenuators do not through away too much signal. The line stage and power amplifier are very quite to my ears. The tube Riaa has room to improve. The PC, soundcard and software test system you use looks interesting.
I am looking foreword to building your Salas Simplistic Riaa and DISCO your implementation of the power supply.
DT
All just for fun!
Hi Salas
Replaced the leds in the CCS of the working shunt by higher vdrop ones and I am now reading 200mV on R1 (10r).
The measurements are made with the shunts connected to the riaa. (Is this a real measurement of the idling output current ? ... should I expect a higher current if the shunt is not loaded ?)
I notice a soundstage depth increase with more "air" between the instruments.
As for Q7 mod, I still have oscilation ...
Ricardo
Replaced the leds in the CCS of the working shunt by higher vdrop ones and I am now reading 200mV on R1 (10r).
The measurements are made with the shunts connected to the riaa. (Is this a real measurement of the idling output current ? ... should I expect a higher current if the shunt is not loaded ?)
I notice a soundstage depth increase with more "air" between the instruments.
As for Q7 mod, I still have oscilation ...
Ricardo
I would expect you read 2V across a 10R R1 for 200mA CCS, not 200mV. Check again. Because of having a CCS in the shunts we avoid changing the demand dynamically on the regulation and ground lines imprint. Its a major benefit in my view, and you should see no difference across R1 either with or without load on the shunt's output. I have wrote before that at about 200mA the output impedance goes lower and the Mosfets gm works better, so you aren't hearing ghosts. The Q7 has been working for me and HiFiNutNut as for now, but I consider it a beta option since it can lead to layout trouble or interactions in some builds because it opens the bandwidth a lot. Now you see why I was reluctant for too many additions in a real diy friendly priority effort like this one in older posts. Anyway if it works it is more robust, resolute and smooth in my system, NutNut liked it too in his super duper big scale OB speakers active crossover.
I would like to be able to test the shunt before connecting it to the riaa.
Without Q7 it is now set to output 28v. (When I installed Q7 it could not produce more than 24v even with the trimmer set to full... is it normal ?)
What I want to know is if it should procuce 28v with the same trimmer setting as without Q7. If so it will be easy to detect oscilation before installation... ( I really do not like to hear the whystle ... it also takes a lot of work to install and I do not like this trial and error method using the perfectly working riaa as a measuring tool)
Without Q7 it is now set to output 28v. (When I installed Q7 it could not produce more than 24v even with the trimmer set to full... is it normal ?)
What I want to know is if it should procuce 28v with the same trimmer setting as without Q7. If so it will be easy to detect oscilation before installation... ( I really do not like to hear the whystle ... it also takes a lot of work to install and I do not like this trial and error method using the perfectly working riaa as a measuring tool)
In the bench it is producing 28,1v from regulated (317 337) 31.2v.
I can adjust the voltage with the trimmer but it is not the same setting as before the Q7 mod... should it be ok ?
I am sorry for the transcendental questions but I do not have a scope (I learned how to use those in the university but I never owned one).
I can adjust the voltage with the trimmer but it is not the same setting as before the Q7 mod... should it be ok ?
I am sorry for the transcendental questions but I do not have a scope (I learned how to use those in the university but I never owned one).