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My CNC phono preamp build.

Lavane

Lavane

Lunatic Member
I have the phono preamp and power supply board, and have ordered everything else to build it. I'm putting it in a passive preamp with a source selector in a chassis I bought to match a tube amp I built a few years ago. I've ordered the NE5532 OP amps to start with. I may alao try the LME4970NA/NOPB'S with an adaptor as well.
I was wondering though, has anyone that has built this preamp tried the OPA2134's since they use a Jfet input stage?
Thanks
 

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Lavane said:
I have the phono preamp and power supply board, and have ordered everything else to build it. I'm putting it in a passive preamp with a source selector in a chassis I bought to match a tube amp I built a few years ago. I've ordered the NE5532 OP amps to start with. I may alao try the LME4970NA/NOPB'S with an adaptor as well.
I was wondering though, has anyone that has built this preamp tried the OPA2134's since they use a Jfet input stage?
Thanks
Click to expand...

I have experimented a bit with different op amps, IMO it would be hard to beat the NE5532 in the first stage. I currently have the LM4562 in the second stage, and I don't feel any need to roll op amps again.
 
Lavane said:
I have the phono preamp and power supply board, and have ordered everything else to build it. I'm putting it in a passive preamp with a source selector in a chassis I bought to match a tube amp I built a few years ago. I've ordered the NE5532 OP amps to start with. I may alao try the LME4970NA/NOPB'S with an adaptor as well.
I was wondering though, has anyone that has built this preamp tried the OPA2134's since they use a Jfet input stage?
Thanks
Click to expand...

Ooh! Very nice. Must give test report on the final build!

:thumbsup:
 
Mr Boochie said:
Ooh! Very nice. Must give test report on the final build!

:thumbsup:
Click to expand...
Will do. I have a thread started on it. Originally I was just going to add a volume control and input selector. Then I noticed a cheap Pyle PP-999 on a shelf I used temporarily, so I was going to add it also as a token phono pre. But decided to go with something better that I could build. It's taking longer than I thought. The chassis kit came with a wrong part and I had to wait for it.
https://audiokarma.org/forums/index.php?threads/passive-pre-input-selector-build.1025777/
 
stratokaster said:
I have experimented a bit with different op amps, IMO it would be hard to beat the NE5532 in the first stage. I currently have the LM4562 in the second stage, and I don't feel any need to roll op amps again.
Click to expand...
Thanks for the input. I'll order a LM4562 and give it a try.
 
stratokaster said:
I have experimented a bit with different op amps, IMO it would be hard to beat the NE5532 in the first stage. I currently have the LM4562 in the second stage, and I don't feel any need to roll op amps again.
Click to expand...
What brand LM4562 did you use? I see some Bridgold brand that are 1/3 the price of TI or Burbrown. I've never heard of Bridgold brand before.
 
slofut said:
Build in enough gain for switchable mm/mc? I have a shelter mc with .5mv output, most phono preamps don't have enough gain. Just a thought.
Click to expand...
I haven't really played with MC carts very much at all. This piece of equipment I'm building is for a second system with a TT using a MM cartridge.
If I really like the preamp, I may build another with MC capabilities.
I really wasn't thinking about a phono preamp in the beginning. The tube amp I'm building this for just doesn't need a preamp at all. I like the overall sound of it as is, no need to color it in any way. So all I needed was a volume control and a few source inputs. But like most of my builds and modds, project creep sneeks in. :D
 
Unless my brain had turned off I've been running them since day one. Few years in now. I like the burr brown chips. They've gotten more expensive and there are counterfeit out there, I'd pay extra for legit sources.
 
loudnoises said:
Unless my brain had turned off I've been running them since day one. Few years in now. I like the burr brown chips. They've gotten more expensive and there are counterfeit out there, I'd pay extra for legit sources.
Click to expand...
Ya, you have to be careful with so many counterfeit parts these days.
 
Lavane said:
This will be using a step down transformer in a wall wart. 120v AC-12V AC @ 1.5w. I bought a panel mount jack to plug the thing into.
Click to expand...
Sorry, perhaps I misunderstood. One of the pictures in post #1 shows a box with two valves and a mains transformer on top. I thought the phonostage was going inside that.
 
rothwellaudio said:
Sorry, perhaps I misunderstood. One of the pictures in post #1 shows a box with two valves and a mains transformer on top. I thought the phonostage was going inside that.
Click to expand...
That was a picture of the amplifier this passive pre is being built to match. I thought about putting a toroidal transformer inside with a shield as others have done, but decided to just use the wall wart. This preamp can be powered using a 12v to 24v transformer. Heat sinks need to be used on the regulators for 24v though. I don't see the need for a 24v trany though. Why stress the regulators like that?
 
Lavane said:
That was a picture of the amplifier this passive pre is being built to match. I thought about putting a toroidal transformer inside with a shield as others have done, but decided to just use the wall wart. This preamp can be powered using a 12v to 24v transformer. Heat sinks need to be used on the regulators for 24v though. I don't see the need for a 24v trany though. Why stress the regulators like that?
Click to expand...
Wall warts get a bad press on this site, and from audiophiles in general, but they really aren't the devil's work, as some claim. The big advantage for a phonostage (whether it's a switch mode power supply or a linear power supply) is that the power supply is kept well away from the sensitive bits of the audio circuit.

The problem with "good" power supplies is that they're often built into a nice/fancy box which matches the rest of the gear and that encourages people to place them next to the gear they're powering. They're better off on the floor, behind the rack, well away from everything else (in my opinion).
 
rothwellaudio said:
Wall warts get a bad press on this site, and from audiophiles in general, but they really aren't the devil's work, as some claim. The big advantage for a phonostage (whether it's a switch mode power supply or a linear power supply) is that the power supply is kept well away from the sensitive bits of the audio circuit.

The problem with "good" power supplies is that they're often built into a nice/fancy box which matches the rest of the gear and that encourages people to place them next to the gear they're powering. They're better off on the floor, behind the rack, well away from everything else (in my opinion).
Click to expand...
Well designed switch mode supplies are pretty decent. I have one in an all tube headphone amp thats built more like a flea watt amp with output transformers.
It uses a 90v to 230v switcher in its own shielded box. I have a couple CDi 1000 Crown amps that use a switch mode supply. It really cuts down on the weight.
I have a small hybrid headphone amp/line out preamp that uses a switcher.
I did find replacing the switcher wall wart with the hybrid with one that can supply more current sounds better at higher volumes.
 
The DIY phono stages that I designed specifically featured a switching supply, converting mains to +/-15v DC - essentially just to demonstrate that it was doable in a LOMC case, and indeed it was (and is). Still, many claim that the switching noise is unacceptable and that replacing the SMPS with a linear supply "improves the sound".
The cheap commercial version uses an 14v AC out wall wart which is double regulated to +/-15v, and as far as I can determine there is no benefit, except it's much easier to position the unit and not have the mains AC couple into the cartridge.
The more expensive commercial unit has a separate supply box with an umbilical and it has received a lot of opposition from various potential buyers who want a single box with the mains plugged into it and no SMPS.:confused:
I guess the customer is always right but not always rational.
 
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