Batery powered DIY CNC phono stage

[sachu888]

Can we source the following parts locally which sachin had ordered from digikey?

Accessories and OP-AMP:
2 X CT2064-ND / SWITCH SPST GOLD 4 SEC / Input Loading Dip Switch
2 X AD823ANZ-ND / IC OPAMP JFET R-R DUAL LN 8DIP / AD823 Op Amps

Capacitors:
2 X P4518-ND / CAP .027UF 50V STACK METAL FILM / RIAA Capacitor
2 X P4519-ND / CAP .033UF 50V STACK METAL FILM / RIAA Capacitor
2 X P4521-ND / CAP .047UF 50V STACK METAL FILM / RIAA Capacitor
2 X P4675-ND / CAP 1UF 50V STACK METAL FILM / DC Blocking
Resistors:
4 X RNF14FTD3K32CT-ND/ RES MF 1/4W 3.32K OHM 1% AXIAL/ Feedback Resistor
4 X 3.83KXBK-ND / RES 3.83K OHM 1/4W 1% METAL FILM/ RIAA Resistor

Hi,
I just checked, All parts are available with Digikey.You should opt for shop n ship for sipping.Digikey will ship(ground shipping $7) to your SNS US address,SNS will charge only $10 for India+custom duty.It will be cheaper if 3 of you combine your order.

Regards,
Sachin

 

[sachu888]

Op amps are available with RScomponents with free shipping
AD823ANZ Analog Devices | Dual op amp,AD823AN DIP8 | 523-7409 | Welcome to RS Online
You may find some more parts here.
Regards,
Sachin

 

[santhosh]

Update on my CNC Phonostage - my First ever Electronics DIY:

Soldering is almost complete. I have problem with the PCB in that one of the solder pads does not have a hole through the PCB (see pic where one of the resistor does not have a through hole) . As per Sachu888's suggestion offline, I plan to drill a hole using a thin bit. Any other ideas or precautions while doing this?

Next steps are to wire the RCA terminals, battery terminals and an fit into an enclosure.

 

[gopib]

When drilling make sure the bit is sharp. Else you may shave off the copper pad. When the size is small I use a sharp pointed tool ( a divider from a geometry box is ideal). This always worked for me as I can gauge if the copper is getting damaged or not and apply pressure appropriately.

HTH

 

[reubensm]

Gopib has got it spot on. Also with some school-day projects i've drilled PCBs from the copper side downward, this ensured that the copper pad did not peal off. It worked wonderfully well. Please ensure that you use the right drillbit. I have also used a compass from my school geometry box to drill holes in PCBs, however, this is quite a painful and time consuming job but will give you excellent results.

Honestly, would have done this before mounting and soldering the other components. Anyways, a quick fix would be to insulate and solder the component directly to the copper pads (as appropriate). Even some high-end equipment manufacturers use this technique (and also, was very common with 1980s Japanese audio equipment). I would not suggest this as it would 1) look untidy, 2) hamper your PCB mounting, 3) give your problems with issues like cross-talk. However, it will save you from the risks of drilling. I've known some of my friends who ended up with cracked PCBs when attempting this. If you're going to drill, please practice on an old PCB before your first try.

Btw, cool job given its your first DIY. Would like to see the other side of the PCB though, to give you full marks for your soldering job

 

[Hiten]

Santhoshbhai,
If you need it regularly get PCB driller like this.

OR if you are using hand drill. Small dia. drill will not fit in its chuck. Crude method I used was get proper dia. nail. flatten it little at the end. make it little triangle shape. use thick paper to surround the other end, push it in the chuck. tighten it. just like the bottom one in below pic.

OH ! forgot to add. Nice job :thumbsup:

 

[sachu888]

Hi Santhosh,
Compass idea should work well without too much risk,or you can get it done with any local pcb maker.Your soldering looks good,watch out for solder bridges,cracked solder joints, etc.Blue Panasonic caps have +/- polarity,did you check that?(longer lead of cap should be inserted in + sign)everything looks good to me.Be careful while fitting Op amps in the socket,if you reverse them,they will never work.
Edit:Op Amps. The end with the crater and/or cutout must go to the end with the cutout on socket. If you reverse them they won't work again. Touch something grounded before handling them. I gently place one side of the pins in the socket and using a fine blade screwdriver to gently push the pins on the other side in far enough to fit in the socket. Then push gently down on the top of the Op Amp so it fits snuggly in the socket. Don't force them in.


Regards,
Sachin

 

[quad]

If you want, you can solder one end of the resistor in
the provided hole, and other on the top side to the resistor
lead as shown.
Or you can even solder the resistor on the other side (copper side).

These alternatives are a little dirty, but will get the job done.
Ideally, you should get a 0.8mm PCB drill bit
and a PCB hand drill as suggested by Hiten. It is useful if you
plan to do more electronics DIY in future.
If you have a Dremel, you can use that for drilling, provided you
have the proper collet.

Quick-Change Collet Set [2615504485] - $4.70 at eReplacementParts.com

 

[omishra]

@ Santhosh, It looks great. if you could not drill hole then just solder that resistor from below side. No problem with that.
Also those small yellow caps near dip switch and output could be inserted closer the PCB. They are looking taller as length of leads are kept longer. Please make it shorter.

 

[Hiten]

If you want, you can solder one end of the resistor in
the provided hole, and other on the top side to the resistor
lead as shown.
Or you can even solder the resistor on the other side (copper side).

Clever thinking quad.

 

[omishra]

Clever thinking quad.

+1. I came across this thinking while designing of LDR volume control PCB. Really nice suggestion. Just keep ground lead longer and resistor closer to OP AMP.

 

[reubensm]

I have a German hi-quality FRIWO powersupply unit which has a single polarity configuration. Does anyone have experience is converting a single polarity powersupply into a dual polarity powersupply with a circuit similar to this? Could this work with the CNC phonopreamp?

 

[sachu888]

I have a German hi-quality FRIWO powersupply unit which has a single polarity configuration. Does anyone have experience is converting a single polarity powersupply into a dual polarity powersupply with a circuit similar to this? Could this work with the CNC phonopreamp?

Cnc can be powered from min 3V to 18V max.

Regards,
Sachin

 

[santhosh]

You guys rocks!! Thanks for all your suggestions and encouragement. I really enjoyed soldering this PCB. Lots of learning too. Hopefully will get a chance to test it this weekend.

@Quad: Loved your suggestion. Thanks for the diagram too.

Will check out the tools on S.P Road tomorrow. If not, will do as per Quad's suggestion.

@omishra: Yup, I realised those yellow capacitors were soldered too tall after I soldered them.

@sachu888: I have to confess that I had a few solder bridges. I fixed the ones that should not be shorted (ensured with continuity tester) and the left the rest as they were already connected through the PCB.

 

[reubensm]

Cnc can be powered from min 3V to 18V max.

Regards,
Sachin

yes, but do you think the single rail to dual rail conversion aspect would work?

 

[omishra]

I have a German hi-quality FRIWO powersupply unit which has a single polarity configuration. Does anyone have experience is converting a single polarity powersupply into a dual polarity powersupply with a circuit similar to this? Could this work with the CNC phonopreamp?

Yes! I designed something similar, PCB for this and some basic schematic too. This is called artificial ground which is kept at 1/2 of supply Voltage. Long time back I have done it for my car preamp. I used TL072 OPAMP. Look here for details.
total supplied current was limited to 50mA Max. In fact I paralleled two OPAMPs for more current. Over that output voltages drops.

For CNC it can be used but while connecting output you need to take wrt -ve (which is actual GND) and o/p, not V-GND (which is at Vcc/2).

 

[reubensm]

for those who are interested, here's where I got the dual rail power supply circuit idea from:

Phono Preamplifier Scrapbook

This would be of great help to CNC users who can opt to use a single battery or step-down power source.

It will be interesting to compare the performance of the single battery power source vs the dual battery power source.

 

[reubensm]

Yes! I designed something similar, PCB for this and some basic schematic too. This is called artificial ground which is kept at 1/2 of supply Voltage. Long time back I have done it for my car preamp. I used TL072 OPAMP. Look here for details.
total supplied current was limited to 50mA Max. In fact I paralleled two OPAMPs for more current. Over that output voltages drops.

For CNC it can be used but while connecting output you need to take wrt -ve (which is actual GND) and o/p, not V-GND (which is at Vcc/2).

that line amp you built for your SX4 is pretty cool. congrats on that build. i'd probably have to do something like that for my esteem. its currently running on its OEM Kenwood cassette player which came with the car, new in 2003

 

[quad]

The BUF634 circuit is a straight out of the datasheet.

Here's a nice writeup on virtual ground drivers -

Virtual Ground Circuits

For CNC it can be used but while connecting output you need to take wrt -ve (which is actual GND) and o/p, not V-GND (which is at Vcc/2).

Om, I think this is not correct.
Hypnotoad drew the CNC schematic in in a slightly confusing, non-conventional way, with the
ground drawn around the circuit.
This shows one channel of the CNC (few of component values changed in the group buy/Hypnotoad's version).

CNC PCB -

 

[omishra]

Om, I think this is not correct.

CNC PCB -

Here no question in CNC where '+'ve => +V, G=> 0V or GND, '-'ve => -V. 'G' is real ground as it is referred in dual PS. and Input and outputs are referred wrt that GND only.

What I was talking was in a situation where '+'ve => Vcc, G=> Vcc/2, '-'ve => 0V or GND. In single PS, our OPAMP is using Dual PS wrt artificial ground. But for remaining part in circuit that GND at OP AMP is Vcc/2 and can not be shorted to there own GND (0V of single PS, which is -ve for OPAMP).

If this Virtual Ground is only referenced everywhere in all circuits powered with same PS then using of virtual ground as GND hold true. But in above situation same single PS at one part and derived virtual GND for another part can not be intermixed. Virtual Ground is Vcc/2 for all other guys using same PS. Only OP AMP is fooled with that.
e.g. We have PS with +18V, 0V and I create artificial ground for CNC (+ve => +18V, G=> +9V and -ve => 0V). Now CNC is happy with 9V above its ground and -9V (9V below its ground). It is referred with raised ground at 9V.
Here my Pass B1 comes with PS requirement +18V, 0V within same box and connected to same PS as of CNC before artificial ground.
How to connect output of above CNC phono to input of this PASS B1 Buffer? Because artificial ground of OPAMP (raised at 9V) will be shorted to 0V ground of PASS B1 buffer.