SM450 Help
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Category: Other Chat
Forum Name: Golden oldies
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URL: https://forum.speakerplans.com/forum_posts.asp?TID=61803
Printed Date: 26 March 2026 at 10:56pm
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Topic: SM450 Help
Posted By: radiouser
Subject: SM450 Help
Date Posted: 15 January 2012 at 3:10pm
Hi All,
I wonder if anyone can help me out with the above mixer.I have had it from new and was only used a couple of times and then put away and forgotten.Recently i got it out again and decided to put it back in service but alas i could find the PSU.Does anyone know the correct voltage and current needed for the mixer +/- 15v springs to mind but not 100% on that.I also want to convert the turntable inputs to line level so if anyone has a circuit diagram or details on how to do it i would be very grateful.I would imagine that there are far better op amps out there now which could be used so if anyone has tuned-up one of these please let me know.
Many thanks all.
Derek.
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Replies:
Posted By: Mhamplification
Date Posted: 15 January 2012 at 8:34pm
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The power supply is + - 15 volts you need about 300ma to power the SM450 but if you are building a psu i would make one about an amp either side so it runs cooler The Citronic ones in the plastic cases do get quite warm I have tried different ways to reduce the cart input to line level and found the best is a 220ohm resistor from the input to ground on each channel |
Posted By: radiouser
Date Posted: 15 January 2012 at 8:55pm
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Hi,
Many thanks for the info,i had an idea it was +/- 15 most op's tend to use that figure.I have some 7815/7915 series 1.5A regs which i will make up into a supply,i already have a suitable transformer
and rec so ill order up some caps from rapid tonight.Thanks for the info on the cart input,ill try that and see what it sounds like.
Yes i had a proper PSU for it but i must have dumped it and i cant find it anywhere,mind you its been stored in the wardrobe for about 18years!! but i do remember it did get very warm. hi hi
Thanks again,
Derek.
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Posted By: bobcat
Date Posted: 18 January 2012 at 9:43pm
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if your'e thinking about using the magnetic cart inputs on line level, you will need a reverse ria filter a circuit is available and its easy to build, as for the psu use an 15 0 15 tx and after rectifier & smoothing this will give you around 21.5 v per rail, and a pair of lm317/377 regs adjusted to 15 v + - wil give you a good stable supply with good noise rejection. B.t.w the v regs will need a heatsink Tim ------------- Cheers And Thanks For comin! |
Posted By: radiouser
Date Posted: 18 January 2012 at 10:33pm
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Thanks for the info Tim,I have made up a supply but i used 7815/7915 fixed voltage regs and it seems to work ok,but i do have a cicuit for the 317/377 adj regs and it will probably give lower
ripple as well.The trannie i used is 18 0 18 which i had to hand and although a bit high i just put a larger heatsink on the two regs.I will get a 15 0 15 doughtnut trannie and built another PSU using the 317/377 regs.
On the disc input i did try initially a inverse RIAA but it tended to sound very different from the other line level inputs and lacked bass,that is why i asked for a circuit so i could compare the line and disc input amps.
I like the sound of the mixer but might try to upgrade the op amps if i can find a suitable eqiv.
Many thanks again for the info.
Derek.
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Posted By: radiouser
Date Posted: 02 March 2012 at 4:00pm
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Hi Thanks for the comments on the PSU for SM450,i have now got it going ok and have replaced the opamps with some OPA2134's which sound great.I have left the NE5532 IC24 in place for the mic circuit.I have also converted the PU inputs to line only and if anyone needs the info for doing this i have the circuit diagrams for the 450,if anyone wants them i will pm a msg to them and append the circuits.Or if there is a place on the forum for circuits etc,i will post them there for all. Many thanks all.
Derek. |
Posted By: Mhamplification
Date Posted: 02 March 2012 at 5:11pm
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Hi Derek Pleased you got the 450 going I would like a copy of the circuit daigram if possible I will send a message with my email address on it Were the op amps direct replacements for the 553`s ? thanks Martin |
Posted By: mostyn
Date Posted: 25 March 2012 at 9:59am
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if it helps i've got copies of the circuit diagrams for the sm440 and sm450 kindly sent to me from the melksham days
mozza
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Posted By: radiouser
Date Posted: 27 March 2012 at 5:02pm
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mostyn wrote:Posted By: AGUS R
Date Posted: 03 April 2018 at 9:30pm
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Hi all, Could you mail me the schematic diagram for the mixer Citronic SM 450... I have problem this mixer, VU level LED one chanel is off. Many thanks all Agus R |
Posted By: Ripcurler
Date Posted: 18 February 2019 at 9:06pm
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Can anyone help me with a schematic for my pristine Citronic SM-440. I put this back into regular service after cleaning the faders and replacing the trimmers. It sounded excellent but there was a bit of underlying noise that bugged me after a wwhile. Chasing this through I pulled the ztx108 transistors that sit in the cue select and other places replaced them with bc549 but now the cue select doesn't work. The LEDs light but the logic is stuck on the main output. A schematic would help me enormously. Thanks Ripcurler
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Posted By: djeddie
Date Posted: 18 February 2019 at 9:49pm
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Here's the 440 schematic http://s000.tinyupload.com/index.php?file_id=03932914361950975593" rel="nofollow - LINK HERE ------------- Chas n Dave : it's like Drum and Bass but with beards. E=mc² ±3dB |
Posted By: Ripcurler
Date Posted: 18 February 2019 at 10:42pm
| Perfect + Thank you |