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

It's a bit embarrassing considering the rest of projects on this page but I've just finished my first CNC. Well, I've got it working! The enclosure and connections are a work in progress. Loving the sound already.

A picture tells a thousand words, so I'll try and post one.

No real problems with the build process thanks to the excellent clear labelling, in fact many thanks to Sachin for such a great board. I did however solder the dip switches upside down!

One query, when selecting input loading I'm getting little or no difference from the 62/47/33 positions but the 18k reduces volume by about 20db. Technics 1210 & Stanton 500 cart, so nothing exotic, but I'm not sure if this is normal, it's the same behaviour on both channels so I guess it might be.

The 47k resistors were a bit of a mistake in the ordering process, not sure if I'm going to need to remedy that. Still got the PS to build and then 1 more of CNC and PS so plenty more to do.
 

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Your shielded wire on the input side looks like there is a few strands of the ground wire loose and close to the white wire. But congratulations, they do sound amazing.
 
Yes, midnight soldering! I had a few attempts with different co-ax but didn't have the sockets for the enclosure so some of my early joints broke because the wire is free floating. Typical of my style that I couldn't wait to hear it so had to cannibalise some leads etc. At my age I should have got over doing that.

I plan to fit it into a plastic enclosure with the OPS and power it from a 12v ac wall wart, I'm concerned about the wall wart being noisy, i.e. making noise as opposed to electrically noisy, as some of my other ac/ac ones are, will see when it arrives.

I'm in awe of the properly finished versions that get posted here, mine is likely to be a bit ragged by comparison.
 
Welcome to AK, and the pleasant sounds of the CNC. For now, just let your ears do the "looking".

If you use RCA cables and connectors to your eventual chassis you can run twisted pairs of insulated solid wire from the case to the PCB. That should minimize any problems with whiskers, and be more pleasing to the eye. Another thing that might help is to use terminal blocks on the PCB so that wires can be inserted and held in place with a set screw. You can see some examples in photots posted by Babblefish and Skrodahl on page 125, posts 2482 and 2491. This also makes it much easier to remove the board if you want to work on it.

Enjoy - - -
 
Hi,, thanks for the welcome. I ordered the terminal blocks last night but didn't have them in my first order as I couldn't find the pitch (which I think is 5mm from my measurements). I tried twisted insulated (stranded not solid) first time round and it seemed to be very effective as an aerial. I'll try it once I have the terminal blocks and rcd plugs and can play around with it. Thanks for the heads up though.
 
I'm using a wall wart to power the power supply and 3' long twisted pairs for an umbilical. Quiet as a graveyard. Airhead, I also have an impatient streak in me. I used these for days jury rigged.
 
Going to one of answer my own questions now. I've been a bit upside down on the input loading so the problem I've been having is with the 62K resistor. Found out why the volume drops off when it's engaged, I've fitted a 61.9Ohm resistor which I ordered as an extra in case I wanted extra gain for my AT cart. So basic user error, no surprise that no one spotted it in the photos but I'm sure it will stand out now to anyone who knows their colour codes. :)
 
mkane said:
I'm using a wall wart to power the power supply and 3' long twisted pairs for an umbilical. Quiet as a graveyard. Airhead, I also have an impatient streak in me. I used these for days jury rigged.
Click to expand...

My wall warts are supposed to arrive tomorrow, I should take it easy now I've got the CNC working (try and do a proper job!). Your avatar caught my eye, wild guess at some sort of yamaha 2 stroke, possibly 350 pre ypvs? I've got a basket case TZR250 taking up yard space which I'll probably never part with even though I'm about 10 kilos too heavy for it now. I go by Airhead because of my R80/7, which is still factory unlike most these days.
 
Easy to lose 1/2 of that. I went from a garage full to just one. It's my track bike. 2 stroke airhead

 
I've thought of this several times but not posted.

Contrary to the title of the thread, there have been some builds that look very high end. Beautiful work guys!
 
Got the CNC and OPS finished and working last night (late!). Properly wired to RCA connectors and all in a case. 12v AC wall wart no problems at all, as MKane said, quiet as a graveyard. I did seem to get a little more high range (pops and clicks came back a bit) changing to the OPS. I had felt there was a slight reduction in top end with the batteries but put it down to having been working with some noisy machinery all day. Now it sounds well balanced. It has improved playback on older albums (20+ years) which could seem bright and harsh. St. Peppers for example used to be unpleasant, on the other hand a few new albums have so little top end (i.e. Burial - Untrue) you wonder if they are even listening to the vinyl once it's pressed.

Thanks for all the advice, especially from Sachin who was great at answering emailed questions. Really great service all round. Anyone wondering whether they should take the plunge with his boards, I would recommend it without hesitation.
 
Hello everybody,

I am a newcomer.
I'm trying to build preamp from datasheet LME49860. One guy reccomend me the other values for RIAA network. I have used this calculator http://www.mh-audio.nl/calculateRIAA.asp

R1=5K1. So we have R2=750 (741.5767), C1=330nf+100nf=430nf (428.81nf), C2=150nf (147.06nf)

Any comments?
Thank you
 
Welcome to AK!

Sounds like you are on the right track. You've obviously done some research, and are knowledgeable about the subject. One great feature of the CNC is that the design allows you to swap and compare different opamps so you can experiment and find a combo(s) that appeals to your listening pleasure.

Enjoy - - -
 
vlads55 said:
Hello everybody,

I am a newcomer.
I'm trying to build preamp from datasheet LME49860. One guy reccomend me the other values for RIAA network. I have used this calculator http://www.mh-audio.nl/calculateRIAA.asp

R1=5K1. So we have R2=750 (741.5767), C1=330nf+100nf=430nf (428.81nf), C2=150nf (147.06nf)

Any comments?
Thank you
Click to expand...
I altered the datasheet RIAA values to suit the measured values of capacitors and resistors I had available in order to tighten up the tolerances and improve the matching for one version of this preamp I built. It turned out to be the one I think sounds the best.
 
vlads55 said:
So we have..., C1=330nf+100nf=430nf (428.81nf), C2=150nf (147.06nf)

Any comments?
Click to expand...
That's three (>1%) capacitors per channel (and too far from the ideal RIAA curve).

1% tolerance capacitors are expensive!
1% (or better) resistors are inexpensive!

Review AN-1651 by Joe Curcio (I'm a NATIONAList) for a better resistor/capacitor combination.
With R1=22k, you retain the capacitor count at three (R2=3k2, C1=100n, C2=33n+1n) and get closer to the RIAA curve.
R1=11k is also a good choice (R2=1k6, C1=100n+100n, C2=68n)!
You can cross-check the results here.

68n,1% Polypropylene
100n,1% Polypropylene
etc...

Good Luck!

EDIT:Correction... (I can't count) :oops: :oops:
 
Last edited:
Hello everybody,
Many thanks for the advices.
Special thanks to Hamish119
I will check the links. And will try to order from Farnell. Hope they will ship to Bulgaria.
At the moment I have three types of opamp - NE5532, OPA2134 and LME49860. Will try all.
Thank you
 
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