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The motivation is to try and deal with HD noise for vintage MPX decoders such as in my Scott 112B, and hiss in Reel to Reel tape decks.
The board will run on 10 to 24v, so two 9v in series should be fine. I just need to eventually find a power switch to fit the existing cutout in the metal case and I should be good.
Not too sure about any possible grounding issues though. First I will float everything but I don't know how that will work for input and output devices.
If I need to ground optionally I can add. After testing, I will use hot glue and/or epoxy to mount board and battery jacks.
It should work, these chips were used by some fairly hi-end devices in the not too distant past and the TI specs look fine. We'll see.
Any advice, comments, or snide remarks?
Follow Ups:
Do you have the schematic? After looking at the data sheet for the LM1894 it makes me wonder why use 2 of the IC's. The app note shows one of the IC's being capable of processing a a stereo pair. Getting rid of one of them, cutting the load in half would go a long way toward keeping two series 9V's happy longer. I don't know if that is a LDO in the lower left but I might even be tempted to try running it straight off the batteries too. It has decent power supply rejection.
I guess you must be cascading as shown. It seems like it would be cool if you had the option to choose single or dual stage operation while you are listening.
Testing has shown that two 9v batteries in series do not provide adequate current.
So I powered with my HP bench supply that puts out 300ma and it sounded fine. When pots at minimum I can detect little to no effect on the sound and gradually rotating pots provides a subtle but increasingly noticeable effect.
I will finalize the mounting of the board in the chassis and then test with the hissy Scott 112B, but I am hopeful for $20 this might be a good solution. With adequate power supply the effect was subtle and not objectionable at all until more than 1/2 way to max on the pots.
Hell maybe I can buy some additional cases and make a living selling DNR units! (but not taking orders yet please)
A dbx 296 will do a superb job getting rid of the hiss, and its HF detail can dial the sparkle back in. Sadly, the internal power supply is a P.O.S. and I recommend modding it.
My 2nd choice is a dbx snr-1 dynamic filter. Works great on hiss. Good power supply.
Tom
Dark energy? Ridiculous!
We live in an electric universe.
Are the DBX devices playback only, or do you need to record with them and playback same?
The filtering I need is for tuner source...
They are single ended, meant for playback only. The 296 uses an 18 VAC wall wart, and the rest of the power supply is inside the box.
Best regards,
Tom
Dark energy? Ridiculous!
We live in an electric universe.
I just happened to come across the schematic for a dbx 296, and the power supply looks fine with two 3-pin regulators. Maybe they made a revision along the line or I could be losing my mind ;-)
Dark energy? Ridiculous!
We live in an electric universe.
I don't know if it's OK to post this here, but I have a Burwen Reaserch DNF 1201A I'd be willing to let go cheap. It doesn't sound as good (sometimes you can tell that the signal is being processed) as the dbx units but it gets the job done. I haven't used it in years, so I'd have to check it out and make sure everything works.
Regards,
Tom
Dark energy? Ridiculous!
We live in an electric universe.
How about a schematic..?
Plus I have another problem.
I need to find a line level source for input testing and an amp and speakers - or maybe headphone amp and phones - for output testing where I don't care if I blow them up, in case the board has any problems or I miswired.
Lost it :(
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