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Hi:I am a DIY beginner, though I have an EE background. I have looked at a couple of the battery powered Phono stages out there like Thorsten Loesch's Analog Addict stage and Klaus Boening's Dr. Groove II stage. Both look like they can be done by beginners and have good results. If anyone has built these, I would love to correspond.
Anyway, here are some questions:
1. For the Analog Addict 'El Cheapo' phono stage, where does one find a 10H 30ohm DCR inductor? If I could source this, I think I would start with this one first.
2. Which battery chargers are people using - I found a source for Yuasa NP 2-12 batteries, but would like reqs on chargers for parallel charging.
3. What's the difference between the OPA637AP and OPA637BP? I looked at the TI/BB site and there is little mentioned. Are these different grades of the same chip?
4. For the Dr. Groove, what 9V batteries/charger do people recommend?
5. What are the maximum MM input voltages for clipping? My Goldring 1042 is rated for a high 6.5mv. The El Cheapo was tested with this, but I am not sure about the Dr. Groove (looks like I could always lower the gain to make it work).
Thanks a ton. Reading the archives has made me eager to start a DIY project.
-MA
Follow Ups:
Hi Michael,the first cascoded stage of the Dr. Groove II starts clipping at 100mV at the input. So there will be no problems with an MM cartrige.
Regarding your Goldring cartrige the gain of the OP amps of the second stage should be set to 30 to 50, depending in the sensitivity of your line or power amp.
Greetings
Klaus
Hi,> 1. For the Analog Addict 'El Cheapo' phono stage, where does one
> find a 10H 30ohm DCR inductor?www.steinmusic.de - that is where I get mine from. BTW, if you don't need the MC Stepup stage you don't need the inductor.
> 2. Which battery chargers are people using
If you do a search, I discussed my own take on that a while back, these chargers have a minimum sonic impact if charging when playing, most chargers do offer that.
> I found a source for Yuasa NP 2-12 batteries, but would like reqs
> on chargers for parallel charging.I (obviously) used one charger circuit per battery, nothing parallel.
> 3. What's the difference between the OPA637AP and OPA637BP?
Non that I'd consider very relevant.
> I looked at the TI/BB site and there is little mentioned. Are
> these different grades of the same chip?Yes.
> 5. What are the maximum MM input voltages for clipping?
Depends upon a lot of factors. The "El Cheapo" has a gain of around 120 @ 1KHz and will clip when fed from 12V batteries at around 6V RMS. Thus up to 50mV RMS can be applied. The active RIAA does not waste any headroom like all passive EQ designs do, thus high gain for level parity with CD and excellent overload behaviour can be BOTH achieved.
Ciao T
Heres one I am currently building. From Glass Audio.
http://digilander.iol.it/paeng/a_pspiced_low.htm
http://www.aaroncake.net/circuits/charger1.htm
Have a look at www.dact.com for phono stages, stepped attenuators and line stage. The phono section and line stage can be run from batteries. I have a passive pre amp, just using the selector switch and stepped attenuator. I am fiddling with the line stage.
Hello!I am currently building the El Cheapo phono
preamp, although I am using a normal, but very
good, AC based supply. I am also using only the
MM part of the circuit for my Shure V15 cartridge.
I think that this design could work quite well
with the OP637 op-amp, and will respond to E-mails
about my project version.Dan
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