This is what I was trying to get at with my question, does this inverting make it worthless to substitute another op amp on the input side? The difference between the OPA27 and LME is subtle enough to be my imagination.
DIY High or Low Ouput Moving Coil Phono Stage
- Thread starter HypnoToad
- Start date
This is what I was trying to get at with my question, does this inverting make it worthless to substitute another op amp on the input side? The difference between the OPA27 and LME is subtle enough to be my imagination.
Probably Jim, it definitely works fine with the OPA27 in the first stage, something that surprised me, so maybe it's limited to a few within the parameters of the design, and specs don't mean much.
The second stage is pretty regular so it would make sense all the usual op amps would work there.
But whatever it's doing it's doing well.
That's correct.
In the first stage, the resistance of the cart sets the gain, the lower the resistance the higher the gain, it's a trans impedance stage.
You can read all about it here:
http://phonoclone.com/diy-pho4.html
Each manufacturer of Op-Amps decides on which parameters to optimize or maximize. Therefore each Op-Amp sounds a little different. It is not as great a difference you might hear in swapping tubes but since we all listen for different things we can swap Op-Amps till we find the sound we like best.
Edit: It seems that only a few Op-Amps work in the input stage. So you need to find those that work within this thread.
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Grainger the AD797 won't work in the first stage, it produces no gain, others on the DiyAudio site have tried it as well.
Richard Murdey stated he originally chose it for the phonoclone but could not get it to work in the input stage.
Well, I've drunk the cool-aid and contacted Richard.
Hypno-you'll recall my post about the med output Benz disturbing my synergy while sounding too good to let go of it
http://www.audiokarma.org/forums/showthread.php?p=4963277#post4963277
Then this is: THE ANSWER!
I am quite excited to do this build and dedicate it to my med output Benz. I am awaiting clarification from Richard about hi output MC, of which I have 3.
For those not following on DIY, elow is his recent DIY Audio post regarding med and hi output MCs and this pre:
"Finally, a note about high output MC cartridges: They might be OK, they might not. It's a bit of a toss up without knowing the coil inductance. The problem occurs if the inductive contribution to the total impedance becomes significant compared to the resistive component over the audio spectrum. Loss of high frequency intensity can result.
Your Benz is probably OK, I suspect. If you can find the coil inductance data from the instructions or someplace, I can tell you for sure one way or the other."
OMG! This will leave me with a 3rd readily available/conveniently switched phono input. That's a problem, isn't it?
Hypno-you'll recall my post about the med output Benz disturbing my synergy while sounding too good to let go of it
http://www.audiokarma.org/forums/showthread.php?p=4963277#post4963277
Then this is: THE ANSWER!
I am quite excited to do this build and dedicate it to my med output Benz. I am awaiting clarification from Richard about hi output MC, of which I have 3.
For those not following on DIY, elow is his recent DIY Audio post regarding med and hi output MCs and this pre:
"Finally, a note about high output MC cartridges: They might be OK, they might not. It's a bit of a toss up without knowing the coil inductance. The problem occurs if the inductive contribution to the total impedance becomes significant compared to the resistive component over the audio spectrum. Loss of high frequency intensity can result.
Your Benz is probably OK, I suspect. If you can find the coil inductance data from the instructions or someplace, I can tell you for sure one way or the other."
OMG! This will leave me with a 3rd readily available/conveniently switched phono input. That's a problem, isn't it?
Once you hear this thing you won't listen to anything else.:yes:
Fasterdamnit
Super Member
Now there is some truth for you! Mine is still sitting in a Vifa tweeter box I used to haul it on a plane to Grainger's. Why? Because I am listening to it! Can't stop to put it in an enclosure, the Music beckons!
If I build another one, I could swap back and forth on the downstairs system between the AT20SLa/CNC and my idle, NOS, Ortofon MC10. Yeaaaahhhhhhhh... :guitar:
So are you saying that only specific Op-Amps work in the first stage?
I guess the obvious next question would be which ones will work?
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The OPA27 of course, NC Jim tried the OPA134 and Jim Reeves tried the LME49710 they all worked.
Some have tried the OPA627/637 and didn't like it in the first stage so maybe the OPA27 is as good as any.
grundigger
Well-Known Member
I agree. I notice that a lot of people modifying DACs go for exotic components in their search for that elusive "analog" sound. We don't need to.
I'm thinking about buying a Denon 301 MkII or a, gulp, DL-S1. The gain of my current MC stage is only 52 dB. It's a DB Systems DB-8HG, which I like a lot. While it's fine for my current '103, I think I might have to build one of these for the 0.18 mV output MC's. I'm guessing that 65 dB of gain ought to be fine?
I agree. I notice that a lot of people modifying DACs go for exotic components in their search for that elusive "analog" sound. We don't need to.
I'm thinking about buying a Denon 301 MkII or a, gulp, DL-S1. The gain of my current MC stage is only 52 dB. It's a DB Systems DB-8HG, which I like a lot. While it's fine for my current '103, I think I might have to build one of these for the 0.18 mV output MC's. I'm guessing that 65 dB of gain ought to be fine?
It's actually the internal resistance of the cart that sets the gain, and others have used it on the DL-103's with great success.
I believe I ordered some OPA134s for this circuit yesterday. Also a hand full of AD823s for the CNC at the same time. It was a local supplier so I don't have the old email confirmation at hand.
Thanks for the help. It does make me feel better.
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I installed a pair of AD711's into the input stage today and they work just fine. AD's on both ends gives very nice punchy bass.
Too soon to tell if they're preferred to the OPA's on the input end yet.
Also installed my LiPo's in place of the 9v batts today, works great! We'll see how the charge holds up. I don't think I got more than 20 hours out of the 9v alkalines, but I was using AD797's in the output stage most of that time. Could the op amps be drawing that much more current? I'll have to take another look at the specs.
Where do you guys get the nice aluminum boxes to mount the PCB in? I don't have a Fry's here and I didn't see these in the online Fry's catalog.
I installed a pair of AD711's into the input stage today and they work just fine. AD's on both ends gives very nice punchy bass.
Too soon to tell if they're preferred to the OPA's on the input end yet.
Also installed my LiPo's in place of the 9v batts today, works great! We'll see how the charge holds up. I don't think I got more than 20 hours out of the 9v alkalines, but I was using AD797's in the output stage most of that time. Could the op amps be drawing that much more current? I'll have to take another look at the specs.
1 x OPA27GP = 3.3ma
1 x AD797 = 8.2ma
So yeah they do draw a lot more current.
What voltage are the LiPo's? Looks like a neat setup.
I have the AD797's but so far been too busy and too lazy to try them out, mine sounds so good now it's hard to imagine it getting any better. But you always come up with something Jim, so will probably try them tomorrow.
I got mine at Fry's they are Context Engineering, Model 4006.
http://www.frys.com/product/2090829
Thanks, every search I made wouldn't come up with this kind of enclosure.