Mark Kelly said:
I remember proposing this a couple of years ago (never got around to it). I did do some experiments with MP3's to see if they hold frequency resolution and was surprised that even at 96K I could see perfect reproduction of 60Hz plus or minus one cycle in a minute. OTOH if you make a perfect sine wave in Audition FFT it and MP3 it and FFT it again there is a lot of (not so) random noise in the signal. It might be worth an A/B test with a clean oscillator, but my feeling is is does not matter much.
Scott
I have actually performed the appropriate tests, having spent a great deal of time and energy constructing power oscillators capable of noise and distortion better than -90dB.
It's hard to summarise my results briefly, as there are many influences on the performance of different motors and I am still accumulating data.
I think phase angle and phase balance are more important than noise and distortion for any reasonable level of noise and distortion. Once phase angle and phase balance are addressed, lower noise is always better, similarly lower even harmonic distortion is always better.
Odd harmonics are another case entirely. For each motor I have investigated there is an optimal level of third harmonic distortion which is related to the cogging torque produced by the motor. The effect requires everything else to be dialed in before it becomes apparent but it's definitely there. I'm currently working on how to optimise this.
The Ipod drive idea is meant as a "bang for your buck" DIY exercise. It isn't the last word in motor drive technology but it can be a significant step up from any single phase drive whether direct from mains or by regeneration.
I have actually performed the appropriate tests, having spent a great deal of time and energy constructing power oscillators capable of noise and distortion better than -90dB.
It's hard to summarise my results briefly, as there are many influences on the performance of different motors and I am still accumulating data.
I think phase angle and phase balance are more important than noise and distortion for any reasonable level of noise and distortion. Once phase angle and phase balance are addressed, lower noise is always better, similarly lower even harmonic distortion is always better.
Odd harmonics are another case entirely. For each motor I have investigated there is an optimal level of third harmonic distortion which is related to the cogging torque produced by the motor. The effect requires everything else to be dialed in before it becomes apparent but it's definitely there. I'm currently working on how to optimise this.
The Ipod drive idea is meant as a "bang for your buck" DIY exercise. It isn't the last word in motor drive technology but it can be a significant step up from any single phase drive whether direct from mains or by regeneration.
Re: methinks you have ...
It's a 15v with a passive delay network. Pro-ject abandoned these in favor of the 16v motors when they upgraded the xpression line of turntables from II, which is what I have, to III. My guess is that now they are single phase motors which is why you can use them with a speed control (mine, of course, you can't use with a speed control unless you cut out the delay network). I'm just going to bypass the delay network and use the offset phase approach suggested here. I found that Audacity generates sine waves that are easily exported as .wav or mp3's in any duration and frequency you choose. It's free for both mac and PC.
Another question. I have a dual primary/ dual secondary trafo. Can I use this to output both channels with an offset phase angle do I need to use two separate trafo's for this purpose. My gut says two, but my heart wants one.
Nanook said:
It's a 15v with a passive delay network. Pro-ject abandoned these in favor of the 16v motors when they upgraded the xpression line of turntables from II, which is what I have, to III. My guess is that now they are single phase motors which is why you can use them with a speed control (mine, of course, you can't use with a speed control unless you cut out the delay network). I'm just going to bypass the delay network and use the offset phase approach suggested here. I found that Audacity generates sine waves that are easily exported as .wav or mp3's in any duration and frequency you choose. It's free for both mac and PC.
Another question. I have a dual primary/ dual secondary trafo. Can I use this to output both channels with an offset phase angle do I need to use two separate trafo's for this purpose. My gut says two, but my heart wants one.
You guys seem confused about the identity of these motors. There is basically no such thing as a single phase synchronous motor, what manufacturers who make single phase powered TTs do is use a two phase synch motor (such as the Hurst motor in VPIs) and fake the second phase with a capacitor.
I haven't inspected a Project but as far as I know they do the same thing with a 16V version. This idea will work with that type of motor but you you need either an output amp capable of swiinging 16V AC or a 1:2 step-up transformer.
One way of faking the latter is to use a standard twin secondary toroidal (such as the one shown in the phot at the top), cutting the primary leads off and tying the two secondaries in series. Power one secondary and take the output across both secondaries.
WARNING: This might give some problems with BTL amps like the T-amps, I haven't tried it.
I haven't inspected a Project but as far as I know they do the same thing with a 16V version. This idea will work with that type of motor but you you need either an output amp capable of swiinging 16V AC or a 1:2 step-up transformer.
One way of faking the latter is to use a standard twin secondary toroidal (such as the one shown in the phot at the top), cutting the primary leads off and tying the two secondaries in series. Power one secondary and take the output across both secondaries.
WARNING: This might give some problems with BTL amps like the T-amps, I haven't tried it.
Mark Kelly said:
Is there any advantage over just making a clean mains? Popular Electronics circa 1969 had a DIY clock drive for telescopes (for precise tracking adjustment) that did that very crudely with a Radio Shack 12.6V backwards and a car battery.
Is there a way to measure these effects loaded without having the belt or bearing contribute?
Mark Kelly said:
My thought is that the 16v Pro-ject TT's must do away with the cap because they are compatible with the speed controls and my 15v version is not. I don't know too much about electricity, but it seems like a speed control system wouldn't work with a passive delay in the way. That is why I make the assumption that the new motors, for whatever reason do not use a passive delay.
Anyway, I cut my delay out, recorded a stereo sine wave, delayed the left channel 90 degrees, played it through a T-amp into the secondaries of two trafo's and ran the motor from the primaries. It works. The only problem I have now, and I can't figure out why this is happening, is that the rotation of the motor at power up is random. Sometimes it will start clockwise (desirable) and sometimes it will start counterclockwise. Any ideas why?
phonoclone 16a completed (finally)
I'm slightly embarrassed to have taken so long but I just finished and tested a phonoclone version 16a (i.e. I bypassed the on board LM79XX/LM78XX and used separate LM317/LM337 power supply boards). What took me time was deciding on this modification (vs getting newer boards), as well as deciding exactly how to implement Richard's suggestion of "using shunts" in order to be able to change R2 to be able to have the preamp work for different cartridges.
Anyway, I am very pleased with the results with an AT-F3II cartridge. Previously I was using a head am feeding a NAD 7220PE phono section. The improvement is astonishing. I am very grateful to you Richard for all your efforts. You have made available working plans for a wonderful mc phono preamp, have regularly ordered boards for people (like me) without the knowledge to do it themselves and have answered lots of questions.
For those who are curious here are some of the parts I used:
AVEL 160VA transformer (it seemed a bargain at US$36)
Panasonic ECQ-PZ series 50V 1% polypropylene caps for RIAA
Vishay/Dale 0.5W 1% metal film resistors for RIAA
Yageo 0.5W 5% carbon film resistors non-RIAA
Analog devices OP27GPZ (I made the lower gain version).
You don't need to spend a lot on parts for this project. I bought duplicates (at most 10) to match left and right and to get the RIAA values as close as possible to Richard's recommendations. It was still very inexpensive.
Anyway, I want to express again my deepest thanks to Richard.
kn
I'm slightly embarrassed to have taken so long but I just finished and tested a phonoclone version 16a (i.e. I bypassed the on board LM79XX/LM78XX and used separate LM317/LM337 power supply boards). What took me time was deciding on this modification (vs getting newer boards), as well as deciding exactly how to implement Richard's suggestion of "using shunts" in order to be able to change R2 to be able to have the preamp work for different cartridges.
Anyway, I am very pleased with the results with an AT-F3II cartridge. Previously I was using a head am feeding a NAD 7220PE phono section. The improvement is astonishing. I am very grateful to you Richard for all your efforts. You have made available working plans for a wonderful mc phono preamp, have regularly ordered boards for people (like me) without the knowledge to do it themselves and have answered lots of questions.
For those who are curious here are some of the parts I used:
AVEL 160VA transformer (it seemed a bargain at US$36)
Panasonic ECQ-PZ series 50V 1% polypropylene caps for RIAA
Vishay/Dale 0.5W 1% metal film resistors for RIAA
Yageo 0.5W 5% carbon film resistors non-RIAA
Analog devices OP27GPZ (I made the lower gain version).
You don't need to spend a lot on parts for this project. I bought duplicates (at most 10) to match left and right and to get the RIAA values as close as possible to Richard's recommendations. It was still very inexpensive.
Anyway, I want to express again my deepest thanks to Richard.
kn
a 300b...60 hz never sounded sooooo good
Found a 25 watter on ebay for a reasonable price. I will drive it at or above 15v. Hopefully this will enable me to get the tranny's out of the system (so I can use them for something else). So, in the end, I had to pay about $30 so far for this project. It never ends.
Found a 25 watter on ebay for a reasonable price. I will drive it at or above 15v. Hopefully this will enable me to get the tranny's out of the system (so I can use them for something else). So, in the end, I had to pay about $30 so far for this project. It never ends.
Mark, keeping the thread "alive"
Mark,
I have decided to give this a go using a class AB amp as a voltage amplifier. I can use an AC synchronous (Hurst 3001-001 or Airpax/Premotec) or an induction motor. I do kind of like the idea of an induction motor. What are your thoughts and/or experiences?
The same could be done as per Altmann and use DC stepper motors of a suitable voltage, using essentially the same scheme.
any comments are appreciated.
Mark,
I have decided to give this a go using a class AB amp as a voltage amplifier. I can use an AC synchronous (Hurst 3001-001 or Airpax/Premotec) or an induction motor. I do kind of like the idea of an induction motor. What are your thoughts and/or experiences?
The same could be done as per Altmann and use DC stepper motors of a suitable voltage, using essentially the same scheme.
any comments are appreciated.
Sorry to dig this up.
I have experimented with this using a stepper motor and t-amp, much like the altmann setup.
Im interested in being able to use a higher quality motor like the hurst, but when you say you need to be carefull on transformer selection can you possibly suggest one? or what to actually look for when buying one.
Thanks,
edd
I have experimented with this using a stepper motor and t-amp, much like the altmann setup.
Im interested in being able to use a higher quality motor like the hurst, but when you say you need to be carefull on transformer selection can you possibly suggest one? or what to actually look for when buying one.
Thanks,
edd
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.