Another Super High End Phono Stage! No expense spared...

Count me in, too!

If you're going through with the group buy, please include me. Just PM me with details, and I'll send the cash. I'll follow with rapt fascination your experiments, and once you've worked out what works best, I'll populate my board accordingly. (Love this place, too! :D) I have visions of being REALLY extravagant with it, and actually mounting it (gasp!) inside of a nice little BOX --if that doesn't destroy the whole spirit of the thing! :D

Whoahhh there, don't go over the top, these things are not used to boxes.:D

Next you will be telling us you are going to use all new parts and not stuff salvaged from old VCR's.
 
Not really. We need to crack it open so we can roll op-amps. At the moment it has a pair of LM4562's and the one time we compared to the Bugle, it was a bit harsh. The op-amps were put in during a troubleshooting session and I meant to change back before the first listening test.

LM4562's are bright especially when two are used together, you will be surprised how much sweeter and smoother the AD823's sound.
 
Down for TWO too, if there'll be an MC spinoff of this I want that too.
:yes:

I think you need to order more than ten PCB's. ;)
 
Down for TWO too, if there'll be an MC spinoff of this I want that too.
:yes:

I think you need to order more than ten PCB's. ;)

The good news is they get cheaper the more you order.:yes:

I am still experimenting with some different value components, I won't be ordering until I am satisfied that we have the best combination.

As for the MC part, I have a nice circuit I have built but still waiting on Comet Supply to send my LOMC cart.:no:
 
I'd be interested as well even tho' my MM listening has gone fallow for other interests at the moment.
 
Please put me on your subscriber list for 1 PCB for the mm version and a BOM.

I’ve been planning to upgrade my phono preamp and build in additional gain in the left channel to account for the channel imbalance in my PL-570/Shure V15 III. I’d like to have about 50 dB of gain to provide dynamic range for the sound card in my PC when digitizing LPs, then reduce it to about 40dB when playing thru my receiver. Sounds to me that I could build your preamp with a 5K pot replacing the 3320 ohm resistor, plus determining the value of a small resistor in the right channel to account for the imbalance in the TT. I can also calculate a new value for the 150 ohm resistor to boost the gain to ~ 50 dB.

The GW stores around have a surplus of used VCRs, so I’d better get a few before the stampede starts.

Like Arkay says, I think that it really deserves a nice box with a LED or 2.

The listening trials that you and fasterdamnit have reported on are making my mouth water, and we are all anxiously waiting for reports using other op amps. All done & said, it sounds like an excellent design & implementation, and an ideal solution for my problems.

Perhaps fasterdamnit, Big Bill, and you can come up with a fancy moniker for this device. One that will stick and is easy to remember. Something like the CNC preamp (Charlotte, NC), CINC (Charlotte In NC), or something with AK in it. I’m sure that many of the other thread readers could suggest some real winners.

THANKS for pulling all this together! ! ! I’m really looking forward to the next installment.

.
 
Whoahhh there, don't go over the top, these things are not used to boxes.:D

Next you will be telling us you are going to use all new parts and not stuff salvaged from old VCR's.

Oh, don't worry... while their numbers are dwindling in favor of DVD players (which people are replacing with blu-ray players), I still see hundreds of VCRs in the used-gear market here. No shortage of them to salvage old parts from. Heck, I could even become a supplier of really grungy old parts for other AKers to use! :D


...
Like Arkay says, I think that it really deserves a nice box with a LED or 2.
...

LEDs? Do we really need to go that far? I just said a box, not LEDs! I'm not sure if those old VCRs even HAVE LEDs in them, to salvage! :sigh:...
:D


Seriously, this seems like one of the more exciting new threads to appear since, um, perhaps the Econowave. More promising than even the Sonic T-amp, which was relatively lacking in the DIY opportunities! Hopefully it will gain a catchy name, too, and take on a life of its own.


:scratch2:..Depending on price, and how good y'all say these actually sound, I might want as many as two boards each for MM and MC... definitely at least one of each, if you make an MC board as well as an MM board.
 
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The good news is they get cheaper the more you order.:yes:

I am still experimenting with some different value components, I won't be ordering until I am satisfied that we have the best combination.

As for the MC part, I have a nice circuit I have built but still waiting on Comet Supply to send my LOMC cart.:no:

If you do go the MC route, I'd be down for one of those (in addition to the previously mentioned MM). I'm also waiting for Comet Supply.:tears:
 
Mine will get the full treatment, just like the Bugle:

Bugle%20001%20%281024x768%29.jpg
 
Please put me on your subscriber list for 1 PCB for the mm version and a BOM.

I’ve been planning to upgrade my phono preamp and build in additional gain in the left channel to account for the channel imbalance in my PL-570/Shure V15 III. I’d like to have about 50 dB of gain to provide dynamic range for the sound card in my PC when digitizing LPs, then reduce it to about 40dB when playing thru my receiver. Sounds to me that I could build your preamp with a 5K pot replacing the 3320 ohm resistor, plus determining the value of a small resistor in the right channel to account for the imbalance in the TT. I can also calculate a new value for the 150 ohm resistor to boost the gain to ~ 50 dB.

The GW stores around have a surplus of used VCRs, so I’d better get a few before the stampede starts.

Like Arkay says, I think that it really deserves a nice box with a LED or 2.

The listening trials that you and fasterdamnit have reported on are making my mouth water, and we are all anxiously waiting for reports using other op amps. All done & said, it sounds like an excellent design & implementation, and an ideal solution for my problems.

Perhaps fasterdamnit, Big Bill, and you can come up with a fancy moniker for this device. One that will stick and is easy to remember. Something like the CNC preamp (Charlotte, NC), CINC (Charlotte In NC), or something with AK in it. I’m sure that many of the other thread readers could suggest some real winners.

THANKS for pulling all this together! ! ! I’m really looking forward to the next installment.

.


I think you nailed it and Bill agrees! :thmbsp:
CNC Phono Pre-Amp

I think it will be close to a Bugle with the right op-amps. The toad is on the right track...

MrToadLogo.jpg
 
The Box

I don't want just any old box, I want a BOXX! A spiffy little box with some of MAXZ28's rosewood veneer. And some LEDs. Gotta have at least one small one to indicate that the batteries are pumping those electrons.

I have an LED VU meter that is handy for telling me when I am pushing things too hard. Might be better to keep it as a separate item running off its wall wart. Don't want to compromise the esthetics of the CNC Phono Pre-Amp.

.
 
G'day all, I've been following this thread with interest and I applaud the initiative shown, but I must add that phono preamp design is exacting, especially the design of the RIAA equalisation network.

It is more difficult than one might think. I certainly do not have sufficient design expertise to do this, and this is precisely why I rate the ESP P06 so highly simply because all the hard work of the design has been already done by Rod Elliott.

This simple circuit is excellent as a means of checking the accuracy of the RIAA equalisation. http://sound.westhost.com/project80.htm Regards, Felix aka catman.
 
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G'day all, I've been following this thread with interest and I applaud the initiative shown, but I must add that phono preamp design is exacting, especially the design of the RIAA equalisation network.

It is more difficult than one might think. I certainly do not have sufficient design expertise to do this, and this is precisely why I rate the ESP P06 so highly simply because all the hard work of the design has been already done by Rod Elliott.

This simple circuit is excellent as a means of checking the accuracy of the RIAA equalisation. http://sound.westhost.com/project80.htm Regards, Felix aka catman.

The actual RIAA equalization network is unchanged and designed by National Semiconductor so it should be very very accurate. The only changes that have been made are in the gain and loading with some DC blocking and radio interference added, so it should all be kosher. The values I have kept to around 1% to maintain accuracy.

It's a passive filter between the gain stages and not in the feedback loop as shelley_d pointed out.
 
Here's my latest listening results on the CNC.

I compared it directly to my battery powered P06, using it as a yard stick.

It was very good but I noticed it did not have the gain of the P06 and also some uncomfortable graininess in the middle to upper regions, which was only noticeable in direct comparison. But as my wife says now that I noticed it, it has to go.

I tried a few different values for the gain resistors from 75ohms upwards and found 100 ohms a perfect match in the first gain stage. It has the gain now of the P06, which has given it a bit more beef.

On to the graininess, working on the assumption that it's probably something simple as the design is sound, I started experimenting.

I found the input resistors made no difference so they were left as is, I then tried the output caps and it was better with them in and this value seems ideal. So I then removed the output loading resistors with the idea of swapping values. I tried listening without them in first and viola sweet sweet sound, no graininess at all now.

I then did another comparison between the "CNC" and the P06 expecting them to be nearly identical.

I was wrong it is the P06 that is now slightly on the grainy side compared with the "CNC". The sound stage is extremely wide and 3d with as much detail as I have heard mixed with a ever so slightly mellow sound that is very pleasing to the ear. Exactly what the AD823's should ultimately sound like or even what the venerable OPA627/637's are described as.:banana:

Who's the idiot that put those loading resistors in the first place? :D It seems they don't agree with the output of the op amps.

Back for more listening. The sad thing is I am going out of town tomorrow until next Wednesday/Thursday so I won't be able to do any more testing until then.

Oh and I tried a LED connected across the batteries with a 8.2k resistor and it works fine, not sure how much juice it takes so I will have to measure it with my amp meter, it should be very low, but like others have said it's pretty necessary.
 
I was wrong it is the P06 that is now slightly on the grainy side compared with the "CNC". The sound stage is extremely wide and 3d with as much detail as I have heard mixed with a ever so slightly mellow sound that is very pleasing to the ear. Exactly what the AD823's should ultimately sound like or even what the venerable OPA627/637's are described as.:banana:

Who's the idiot that put those loading resistors in the first place? :D It seems they don't agree with the output of the op amps.

Ooohhh, it starts 'sounding' more and more interesting from here.
:tresbon:
 
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