DIY Cheap upgrade for a cheap phono stage

I will confess now that my gear at home is ultra sub-par bargain basement stuff; but I try to do the best that I can with it. 

After working at a dealer myself that sold VPI and Rega tables, Conrad-Johnson, etc – I wanted an at least mildly respectable turntable.

So, a few years back I picked up a B-stock Pro-Ject table and fit it with a pretty nice GRADO MM cartridge; and left it at that.

My garbage A/V reciever doesn’t have a phono stage; so I picked up the ultimate of all ultimate pile of crap phono stages.

The MCM Electronics 40-630 Piece Of Crap phono stage:


widely available on eBay for anywhere around $10-$20; you get exactly what you pay for.

Although I do not own the appropriate gear to measure it and tell you; I can say that the RIAA EQ curve is VASTLY off base; the sound stage is ultra flat and narrow. Everything is very brittle sounding and it sounds almost like your records have been placed under running water while using this phono stage.

But the most noticeable flaw with this phono stage is the INSANE 60hz hum. This unit is A/C powered and has the transformer inside of its chassis.

The hum is so bad that the reciever has to be turned up quite loud to get over it; and in many cases the hum just drowns out any recorded sound on the record.

So; time to rip it apart.

After unfolding two tabs; the bottom plate can be slid right off


Just look at that quality!!!! And the “Fully isolated” transformer is a piece of state-of-the-art wonderment!

We are going to solve the hum problem by replacing the transformer with a DC Battery power supply.

After checking it out with my multimeter I determined that the transformer was putting out a somewhat fluctuating voltage range of 15.5VDC-17VDC.

Awesome; the solution is easily within reach at this point.

Proceed to remove the transformer – it is mounted to a plate that is held to the chassis with two screws.


There is the offending pile of crap:


Make sure that it goes DIRECTLY into the trash


All in all; still a pretty low quality piece – but lots of room


(with the “isolation plate” back in place)


And; the ultimate solution to the problem:


I had this stuff on hand; but if you wanted to purchase it – here is what I used:

-(2x) “Heavy Duty” 9V Battery Snap Connector Radio Shack Part Number 270-324 (pkg. of 5)
-(1x) SPST Mini Toggle Switch – Radio Shack Part Number 275-634
-(2x) 9V Alkaline Enercell Batteries – Radio Shack Part Number 23-463 (pkg of 2 batteries)

…Actually; if you haven’t got this stuff on hand – it may not be worth purchasing – since the parts wouldprobably cost you about $15 – and for a grand total of $35 you could probably find a better phono stage than this MCM Electronics piece. 

The rest is fairly self explanatory; I’ll let the pics talk…

Test fit:


Cut the pigtails to the appropriate length:


Mr. Dremel:


Test fit switch (and cover hole for A/C cable with electrical tape):


Solder and shrink wrap the battery connectors:


Add a Positive lead to go from the phono stage to the battery power switch:


Connect battery pigtail negative lead to phono stage:


Solder switch in place:


Cover the switch and bottoms of the batteries with tape to protect against shorting; then put it all into the chassis:


Put the bottom cover back on it and make appropriate labeling for the new switch:


I also marked the date of when I installed the current set of batteries on the side of the chassis.



And the results…

Was it worth it? ABSOLUTELY!!

The hum is GONE the phono stage is 100% silent!!

Additionally; the soundstage is wider and not quite as flat; the phono stage is now also a great deal warmer; instruments no longer sound like they are buried – and the EQ curve sounds like it is a WHOLE lot closer to where it should be.

Swapping out the transformer for batteries isnt going to make this shining turd sound like a $50000 phono stage; but it WILL make it sound kind of like a $50.00 phono stage.

I am almost positive that replacing the crappy components with some quality components will make a MASSIVE difference – but I don’t see myself actually investing any money into this thing.

Given my average listening habits and the current draw of the transistors I would estimate proposed battery life somewhere around 1YR. But – I think that I am going to be buying a new phono stage tomorrow anyway; so I don’t think it matters.

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