Is there a good quality small magnetic cartridge phono preamp board that can run on up to 12Vdc?
The B+ to the 45 player is +12Vdc as I needed to replace the stock motor with a DC brushless motor due to it inducing hum in the cartridge. I can use a LM-317 to derive any voltage under +12Vdc.
I've got an RCA 45 player I converted to a stereo magnetic cartridge and wanted a built in preamp so that I can plug it into any line level input.
The board needs to be relatively small as there's only a small place for it to fit.
Pictured is where the board has to go and also a previous attempt from a few years ago that didn't work so good. The existing board is 3" X 2 1/4", but there's enough space to where it can be 3" X 2 1/2".
The B+ to the 45 player is +12Vdc as I needed to replace the stock motor with a DC brushless motor due to it inducing hum in the cartridge. I can use a LM-317 to derive any voltage under +12Vdc.
I've got an RCA 45 player I converted to a stereo magnetic cartridge and wanted a built in preamp so that I can plug it into any line level input.
The board needs to be relatively small as there's only a small place for it to fit.
Pictured is where the board has to go and also a previous attempt from a few years ago that didn't work so good. The existing board is 3" X 2 1/4", but there's enough space to where it can be 3" X 2 1/2".
I've made good use of this kit after upgrading the TL072: https://www.tme.com/us/en-us/details/vel-k2573/assembly-kits/velleman/k2573/
EDIT: It came up as withdrawn after I clicked on "similar products"!
For other interested parties, it's available as the Whadda WSAH2573 here in the UK: https://quasarelectronics.co.uk/Item/velleman-k2573-stereo-pre-amplifier-md-pick-ups-kit
EDIT: It came up as withdrawn after I clicked on "similar products"!
For other interested parties, it's available as the Whadda WSAH2573 here in the UK: https://quasarelectronics.co.uk/Item/velleman-k2573-stereo-pre-amplifier-md-pick-ups-kit
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How good does that kit sound given it only uses a single OP-AMP?
Also the input impedance of the Schiit Saga S preamp is 10k. Will the kit work well into that impedance?
What OP-AMP did you use as an upgrade?
Also the input impedance of the Schiit Saga S preamp is 10k. Will the kit work well into that impedance?
What OP-AMP did you use as an upgrade?
I used it in a vintage set-up and I couldn't fault its performance in that application.
Obviously, the pre-amp makes no pretense of being the ultimate in hi-fi quality given its low price.
I used it into a line (AUX) input. These are typically 10 kΩ or more.
I can't remember my chip upgrade offhand, but the Burr Brown OPA2134 is recommended.
Obviously, the pre-amp makes no pretense of being the ultimate in hi-fi quality given its low price.
I used it into a line (AUX) input. These are typically 10 kΩ or more.
I can't remember my chip upgrade offhand, but the Burr Brown OPA2134 is recommended.
I can't guarantee the Velleman kit will provide the "warm musical sound" that's down to the 12AX7A tube in the output stage of the Bellari! 😀
Mine came with a 12AU7.
I'm not concerned about the warm sound.
I just want it to be reasonably accurate.
I'm not concerned about the warm sound.
I just want it to be reasonably accurate.
The board I have came from this preamp
https://www.phonopreamps.com/tc450pp.html
If it's similar to the one posted here I might be able to use it.
Is there any schematic for that one?
It uses the JRC 4558DD OP-AMP
https://www.rcscomponents.kiev.ua/datasheets/jrc45584i743ncft874nfdt34ufguygf43.pdf
Now if that is not a good OP-AMP, but the rest of the circuit seems solid, I can remove the chip and install a socket so that I can use any OP-AMP with the standard pinout.
https://www.phonopreamps.com/tc450pp.html
If it's similar to the one posted here I might be able to use it.
Is there any schematic for that one?
It uses the JRC 4558DD OP-AMP
https://www.rcscomponents.kiev.ua/datasheets/jrc45584i743ncft874nfdt34ufguygf43.pdf
Now if that is not a good OP-AMP, but the rest of the circuit seems solid, I can remove the chip and install a socket so that I can use any OP-AMP with the standard pinout.
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Installing an IC socket in your existing pre-amp would certainly be convenient if you wish to compare different types of dual op-amps.
The Velleman is fitted with a socket and, having checked, I now know that I replaced the TL072 with an NE5532.
https://components101.com/ics/ne5532-dual-low-noise-op-amp#:~:text=NE5532 Dual Op-Amp IC features and specifications 1,Available packages: TO-99, CDIP, DSBGA, SOIC, PDIP, DSBGA
P.S. It may be of general interest to share that 'Velleman for Makers' has been transformed to 'Whadda' who have upgraded many Velleman projects:
See the range here: https://quasarelectronics.co.uk/Category/velleman-kits-modules-uk-official-distributor-stockist
The Velleman is fitted with a socket and, having checked, I now know that I replaced the TL072 with an NE5532.
https://components101.com/ics/ne5532-dual-low-noise-op-amp#:~:text=NE5532 Dual Op-Amp IC features and specifications 1,Available packages: TO-99, CDIP, DSBGA, SOIC, PDIP, DSBGA
P.S. It may be of general interest to share that 'Velleman for Makers' has been transformed to 'Whadda' who have upgraded many Velleman projects:
See the range here: https://quasarelectronics.co.uk/Category/velleman-kits-modules-uk-official-distributor-stockist
I think that I either stopped using the circuit because it only has one OP-AMP or maybe it was because the Shure SC-35C cartridge sounded dull and I thought it was the preamp when it was actually the stock .7mil stylus tip versus the JICO stylus I have installed with the .6 mil tip.
For the TC450 circuit, it had 10uF output coupling caps which would induce some phase shift starting at 50Hz. I needed 33uF caps to get the phase shift to zero at 20Hz, but all I had was 100uF caps so I used those.
For the TC450 circuit, it had 10uF output coupling caps which would induce some phase shift starting at 50Hz. I needed 33uF caps to get the phase shift to zero at 20Hz, but all I had was 100uF caps so I used those.
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A single ended power supply (+12V) operating one dual op-amp will certainly be bettered by a double ended power supply (+/-12V) operating two dual op-amps. An example of the latter is described in this link: https://sound-au.com/project06.htm
I temporarily mounted the preamp and tried it.
Seems to sound decent enough.
Will need to properly mount it with double sided tape and connect it properly then do an extended listening session.
I need to look up the cartridge so I can see the recommended loading capacitance to be sure the board has the right value of cap on the input. Maybe that's one reason the preamp didn't sound good initially several years ago.
Seems to sound decent enough.
Will need to properly mount it with double sided tape and connect it properly then do an extended listening session.
I need to look up the cartridge so I can see the recommended loading capacitance to be sure the board has the right value of cap on the input. Maybe that's one reason the preamp didn't sound good initially several years ago.
The schematics of the Velleman circuit are in the manual https://quasarelectronics.co.uk/manuals/velleman/usermanual_k2573.pdf
The ceramic capacitors in the RIAA correction of the Velleman circuit look like single-layer class 2 capacitors to me. I would definitely replace them with either class 1 ceramic capacitors (NP0, C0G) or film or foil capacitors. In general, the filter components of the TC450 look better than those of the Velleman kit.
The ceramic capacitors in the RIAA correction of the Velleman circuit look like single-layer class 2 capacitors to me. I would definitely replace them with either class 1 ceramic capacitors (NP0, C0G) or film or foil capacitors. In general, the filter components of the TC450 look better than those of the Velleman kit.
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The tc450 indeed uses film caps.
Will need to look at the board to see if it has loading caps on the input.
Will need to look at the board to see if it has loading caps on the input.
The preamp does sound good, however the treble is slightly rolled off which I believe is due to the 220pF load capacitors that are on the preamp.
I saw mention where the load capacitance is around 135pF.
I may try and remove the caps and see if there's an improvement.
EDIT:
Indeed there's an improvement.
May not install any caps at all as it sounds good enough.
I ran two pieces of regular cartridge wire inside the shield from a piece of shielded cable so I'm sure that's adding some capacitance.
Will listen to it tonight on my main system to verify it's good.
The preamp originally had a 9.1 volt zener which somehow shorted and I simply removed it and it runs on 12Vdc . I did notice that I can hear a slight noise in the audio as the motor first spins up, but the voltage for the preamp is taken from the 12 volt regulator I used for the motor, so I might use a separate regulator for the preamp voltage. Probably will use one of these regulators https://www.amazon.com/Onyehn-Adjus...r/dp/B07G59J3TL/ref=sr_1_8?crid=3BB8UZOLI8A2J
Will give me 9 more to use for other projects.
I saw mention where the load capacitance is around 135pF.
I may try and remove the caps and see if there's an improvement.
EDIT:
Indeed there's an improvement.
May not install any caps at all as it sounds good enough.
I ran two pieces of regular cartridge wire inside the shield from a piece of shielded cable so I'm sure that's adding some capacitance.
Will listen to it tonight on my main system to verify it's good.
The preamp originally had a 9.1 volt zener which somehow shorted and I simply removed it and it runs on 12Vdc . I did notice that I can hear a slight noise in the audio as the motor first spins up, but the voltage for the preamp is taken from the 12 volt regulator I used for the motor, so I might use a separate regulator for the preamp voltage. Probably will use one of these regulators https://www.amazon.com/Onyehn-Adjus...r/dp/B07G59J3TL/ref=sr_1_8?crid=3BB8UZOLI8A2J
Will give me 9 more to use for other projects.
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Been using the changer for a bit and am satisfied with it.
I know the preamp isn't the best though.
There any good shielded tonearm wire around that isn't super expensive?
I know the preamp isn't the best though.
There any good shielded tonearm wire around that isn't super expensive?
1 op amp can do an excellent job. Many op amps have 0.01% thd in RIAA configuration.
2 op amps allows easier EQ settings.
2 op amps allows easier EQ settings.
Are there any single OP-AMP dual supply RIAA preamps that can operate on +/-12Vdc and be as small as the existing preamp board?
I'd prefer pre-built unless there's a kit with a PC board.
However with pre-built I don't want to spend a lot as I'm just going to remove the board from the case anyways.
Would two OP-AMPs allow for a more accurate EQ?
I wonder if the Rolls Belari VP-129 preamp uses just one OP-AMP for the RIAA and the other OP-AMPs are only for providing gain for the line out and headphone out.
I'd prefer pre-built unless there's a kit with a PC board.
However with pre-built I don't want to spend a lot as I'm just going to remove the board from the case anyways.
Would two OP-AMPs allow for a more accurate EQ?
I wonder if the Rolls Belari VP-129 preamp uses just one OP-AMP for the RIAA and the other OP-AMPs are only for providing gain for the line out and headphone out.
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Thanks for that. Will order one when I get paid again on Thursday.
I'll have to get a Traco +/- power supply module though as that's the easiest way to generate +/- 12Vdc provided there's room on the speed control PC board for the small module to fit.
Just emailed them about if it is possible to alter the input capacitance to suit the cartridge I am using.
If so I may see if I can find a socket that a cap can plug into unless it's better to solder the cap to the board.
I'll have to get a Traco +/- power supply module though as that's the easiest way to generate +/- 12Vdc provided there's room on the speed control PC board for the small module to fit.
Just emailed them about if it is possible to alter the input capacitance to suit the cartridge I am using.
If so I may see if I can find a socket that a cap can plug into unless it's better to solder the cap to the board.
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