Hi everyone !
I’ve bought a pair of boards to build a dual mono phono stage based on the "Le Pacific" circuit. Here’s a link to the ebay ad :
PCB for RIAA JFET Phono Preamplifier Dual Mono - Two Boards only | eBay
The seller is from the toronto area and does it’s own designs, so it’s no chinese unknown circuit. (It looks a lot like the boozhound lab phono stage though...)
While i’m waiting for the boards to arrive, i’m starting to plan the power supply. I asked the seller for some recomendations regarding the power supply. Here’s his answer :
"Hi Gabriel,
General rule is: stay away from any 3pin regulators as LM78XX LM317, LM350 and so on, cause these are noisy.
Better results you will have with old, good uA723 / LM723, plus passing transistor.
By the way, my variant of the phono preamp has modified power section to improve filtering ripples and some noises from power supply.
I have a plans to design quiet power supply dedicated to phono preamp, unfortunately, right now I'm very busy with my day job.
Thanks and happy DIY-ing."
Btw, the boards need 18V to 24V.
Does anybody have experience with the LM723 regulator ? I looked at the specs and it’s clearly less noisy than a LM317, but a lot more complicated to me. I would like to know if it’s worth the trouble. My first idea was to use an external power supply in the style of a laptop charger, but couldn’t find one rated below 100mA, wich is the max current according to the seller. Could this kind of power supply be adequate considering the added filtration on the boards ? Could it be more appropriate to just use a 24V wall wart, and filter/regulate the supply inside the chassis on a third board ? I really want to stay away from batteries for this project.
Thanks in advance for your answers and your time !
I’ve bought a pair of boards to build a dual mono phono stage based on the "Le Pacific" circuit. Here’s a link to the ebay ad :
PCB for RIAA JFET Phono Preamplifier Dual Mono - Two Boards only | eBay
The seller is from the toronto area and does it’s own designs, so it’s no chinese unknown circuit. (It looks a lot like the boozhound lab phono stage though...)
While i’m waiting for the boards to arrive, i’m starting to plan the power supply. I asked the seller for some recomendations regarding the power supply. Here’s his answer :
"Hi Gabriel,
General rule is: stay away from any 3pin regulators as LM78XX LM317, LM350 and so on, cause these are noisy.
Better results you will have with old, good uA723 / LM723, plus passing transistor.
By the way, my variant of the phono preamp has modified power section to improve filtering ripples and some noises from power supply.
I have a plans to design quiet power supply dedicated to phono preamp, unfortunately, right now I'm very busy with my day job.
Thanks and happy DIY-ing."
Btw, the boards need 18V to 24V.
Does anybody have experience with the LM723 regulator ? I looked at the specs and it’s clearly less noisy than a LM317, but a lot more complicated to me. I would like to know if it’s worth the trouble. My first idea was to use an external power supply in the style of a laptop charger, but couldn’t find one rated below 100mA, wich is the max current according to the seller. Could this kind of power supply be adequate considering the added filtration on the boards ? Could it be more appropriate to just use a 24V wall wart, and filter/regulate the supply inside the chassis on a third board ? I really want to stay away from batteries for this project.
Thanks in advance for your answers and your time !
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Phono is tricky because of the noise performance required. The rules of thumb for genuinely quiet is 1) transformer not in the same chassis, and 2) add a lot of filter caps. 🙂
A good implementation of a 317 with a wart can be very quiet. Same with a 7824, though those usually need more capacatiance for similar noise.
A 723 circuit can be found as shown here - (Although I would add a lot of filtering before and after the regulator to this particular implementation.)
Regulator Power Supply AC-DC 0-50V 3A Assembled Kit 2SC5200 LM723 [FA816] | eBay
A good implementation of a 317 with a wart can be very quiet. Same with a 7824, though those usually need more capacatiance for similar noise.
A 723 circuit can be found as shown here - (Although I would add a lot of filtering before and after the regulator to this particular implementation.)
Regulator Power Supply AC-DC 0-50V 3A Assembled Kit 2SC5200 LM723 [FA816] | eBay
I would use a standard 78 series, noise is not an issue as the recommended 10u capacitor filters it out.
Why spend your money or something that is in the end no better than the 78/79 series after the filtering.
Why spend your money or something that is in the end no better than the 78/79 series after the filtering.
The seller is right, you'll ruin the sound of this good preamplifier with standard IC regulator.
I would use voltage regulator from schematics of Kenwood KA 3020 amplifier, just positive side of regulator, adjusted to around 20 to 24V output.
I would use voltage regulator from schematics of Kenwood KA 3020 amplifier, just positive side of regulator, adjusted to around 20 to 24V output.
This is the original schematic. The circuit of the board i’ve bought is supposed to have some added filter to it. But i’m really not sure it’s enough to simply plug a laptop style power supply directly into the boards.
From what I understand of your comments, I should go for the less noisy options. Is there any other way to build a silent power supply without using ICs ? I’ve seen some examples on ebay using only discrete components, but this is above my actual understanding of the subject.
Absolutely will need more filtering than a laptop brick.
Don't be afraid of 78xx/79xx, they are great tools.
Note this - the regulators on the heatsinks are 7824/7924. This is the PSU of the Pass Labs XP-25.
Don't be afraid of 78xx/79xx, they are great tools.
Note this - the regulators on the heatsinks are 7824/7924. This is the PSU of the Pass Labs XP-25.
An externally hosted image should be here but it was not working when we last tested it.
I misunderstand you, point is to make this preamplifier to work, and it will sure work with 78xx.
Good idea is to put heavy gold RCA connectors to this preamp.
Good idea is to put heavy gold RCA connectors to this preamp.
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It’s kinda this, but on the other hand, building a phono stage that is not better than what I already have makes no sense to me. I just didn’t know that phono power supply were that tricky to build lol
I understand you, me too took years to learn this 🙂
If you check schematics of commercial amplifiers, you will see that no one use 78xx regulators for phono preamps.
There must be a reason why.
Check here, member dreamth knows things:
ultra low noise regulators
If you check schematics of commercial amplifiers, you will see that no one use 78xx regulators for phono preamps.
There must be a reason why.
Check here, member dreamth knows things:
ultra low noise regulators
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Very interesting!
I totally agree that batteries would be the cleanest supply I could get, but to me it feels a bit like cheating. I think it’s possible to get a power supply with an acceptable level of noise, but I realize that i’m far from having the skills to design one without investing a huge amount of time and effort learning and doing errors. Batteries are simple enough though.
The studer 900 psu is very interesting. I think I will got that way. It costs less than the boozhounds power supply, wich is built around a simple ld1085. At 0.003% of the output, there should be 0.054V of noise at the output of the LD1085 for 18v. 0.072 for 24v output. The studer seems to provide much better filtration and regulation.
Do you think it would be worth the investment to buy 2 one channel boards with one transformer for each board ? This would make for a 100% dual mono phono stage !
I totally agree that batteries would be the cleanest supply I could get, but to me it feels a bit like cheating. I think it’s possible to get a power supply with an acceptable level of noise, but I realize that i’m far from having the skills to design one without investing a huge amount of time and effort learning and doing errors. Batteries are simple enough though.
The studer 900 psu is very interesting. I think I will got that way. It costs less than the boozhounds power supply, wich is built around a simple ld1085. At 0.003% of the output, there should be 0.054V of noise at the output of the LD1085 for 18v. 0.072 for 24v output. The studer seems to provide much better filtration and regulation.
Do you think it would be worth the investment to buy 2 one channel boards with one transformer for each board ? This would make for a 100% dual mono phono stage !
I designed a Moving Coil preamplifeir a few years back and I used a very quiet power supply as was presented by the famous Walt Jung.
If you are interested you can find all the details here:
The MC100 - A High-Quality Moving Coil RIAA Preamplifier | audioXpress
If you are interested you can find all the details here:
The MC100 - A High-Quality Moving Coil RIAA Preamplifier | audioXpress
Hi,
I'd suggest you take a look at the psu Ralp Stens uses for his x ono clone. works fine. I use an adapted version of that. I'm quite sure it would be good enough. And yes it uses simple 317/337 regs in the final stage.
regards
Joris
edit: link Pass XOno Clone – RStAudio.de
I'd suggest you take a look at the psu Ralp Stens uses for his x ono clone. works fine. I use an adapted version of that. I'm quite sure it would be good enough. And yes it uses simple 317/337 regs in the final stage.
regards
Joris
edit: link Pass XOno Clone – RStAudio.de
Thanks to you guys for all the informations. I decided to go with gigigirl’s proposition, wich is the studer 900 board. I can’t build a regulated power supply as good as this for the same price. The parts for the boozhoundlabs LD1085 power supply, without the board, cost more than the complete studer kit. Shenzen is hard to beat when it comes to electronics hehe !
I just have to decide on the model i’ll chose : one dual output board or two single output boards. I’m not shure if going for two separate boards would provide any advantages over the dual output board. They seem to be exactly the same, but I couldn’t confirm that.
I just have to decide on the model i’ll chose : one dual output board or two single output boards. I’m not shure if going for two separate boards would provide any advantages over the dual output board. They seem to be exactly the same, but I couldn’t confirm that.
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