Comparing battery-powered phono pre-amps, from RS ($$) to ASR ($$$$) ... and beyond!

You were mentioning external power supply where only DC enters the main box?

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Got that.

It enters in the corner of the main box. The connection and filter board are within a faraday cage:
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Then to the power switch- I decouple +, - and ground, as well as the feed for the LED all at once.

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That litz braided line makes its way to the MM and then MC boards.

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Lots more tidying to do but I deliberately have the MC board as far as possible from the incoming power. All the switching mombo-jumbo happens after signal is brought up to line level. Input wires are as short as possible. All signal wire is solid copper, tin plated. (Power is stranded, tin plated)

If I make this a product, as I hope to do, there will be one board with one power entry point and all switches mounted direct to the board. It’ll still be cramped around the op amps because you want those caps as close as possible. Otherwise I’m going to spread it out.

MAYBE some easier loading options. Possibly stealing the 47k idea of jumpers to set loading (and gain in the case of the 47k). The board designer is quite busy but he did get me files for the elliptical filter. That’s a much easier project. Besides the filter, it will also have switchable 10dB gain.
 
There is some great info there, very interesting read (yes my dinner went cold), really appreciate the contributions too!
Still waiting for the other 3 battery pre's to show up, great idea about using 2 in stock form. What will be more interesting is applying the mods and listening. 3D you are going into a lot of detail here, good stuff.
 
The Powerful Difference said:
When I was young I would make mistakes, get mad about it, not realizing how much more you learn when this happens.
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When the WOPL was having issues, there were some moments where I got 'angry', but certainly not silly angry like when I was young. I realize this happened for a reason, to make me learn. Lee and Joe spent hours guiding me through the troubleshooting, and I am glad I took the time to nut it out with their guidance, learnt a bunch at the same time. I think as we age it gets easier to keep our cool and let things go, always come back and have another go. In the case of the WOPL, I just kept putting her back on the bench, chipped away at it. It can't always be fixed in one day. Patience is important and a part of being a mature adult.
 
Metal film resistors are a given. As you point out, in a new build, the price difference to stuff an average board is less than a cup of coffee.

Metallized film capacitors- if you want exotic, I think the Mundiorf in the red wrapper are the nicest. That says, I rarely spend that extra money because the difference is so small.

But, another advantage is how tightly tolerances these things get. A 1%tolerance film cap is not that exotic. Channel balance gets easier. Behavior much more predictable.

When I couldn’t get specific parts for my phono preamp, I went tighter on tolerance and/or up in voltage or amperage. Price difference from a 2% metal film resistor to a 1% is less than a dime. And I have a few that are 0.1% tolerance…
 
The Powerful Difference said:
...And that's all I've got for this battery phono preamp project -- for awhile anyway.

The good news is that a ton of gear has arrived for the lab, so I am going to refocus on physically assembling / repairing / proving the repeatability of this lab for the next while.
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Then the 3 amps, the preamp, the speakers...and then once *all* that is back online, then I'll get to come back & turn all this phono preamp theory into reality for myself -- for listening to Aja on vinyl will literally be the cherry on top of this huge project. (At least the TT is ready & waiting. :0)


Meanwhile, if Derek92994 & others want to take this project & run with it in the interim, I will be all eyes & ears.

Best of luck, mate! :0)

Cheers --
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You know if learning had been this much fun when I was in school, I might have stuck with it and got a degree.
I did get my RNE (red neck engineering) degree but that came from the school of hard knocks.
3D your effort and enthusiasm is appreciated, I understand a little more now than I did before, thanks.
 
3D, that is excellent, my cigarette went out multiple times during reading :evil4:. Your contribution is much appreciated. I am working 12 hour shifts, so not much time to do anything. On a positive note the other 3 phono pres arrived. The best I can do for now with the 30 minutes I have before bed, is hook two of them up and dedicate each to one channel. I have also purchased some fresh duracell ultra 9 volt batteries which are supposed to be a step up from the standard copper top.
More when I get some time to play with these. Cheers from Australia Mate!
 
Hooked up the two pres, both loaded with a duracell ultra battery. Two audio grade 32k resistor plugs on unused inputs (its all I had handy). Earth wire running from Turntable then another wire to share the earth to the 2nd pre. Put some Dire Straits on, Japanese pressing, not bad. Its going to get better too with upgrades!
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I went back to running the tubebox ds off the standard switch mode psu due to space constraints, it still sings nicely and sounds more full than the rat shack battery pres. That being said, considering what the battery pres are, they do very well, but of course this will improve with mods.

Currently running sovtek 12ax7 lps valves, they are close to the genalex gold lion valves, which have a certain edge to them. Cant really describe what the difference is, both sets of tubes sound good. There is also the stock electro harmonix valves which came with a kit line level preamp that I built, have not run those much as I almost immediately upgraded to the sovtek/genalex valves.

She has some dust build up from non use but who knows, there could even be upgrades to this in the future.
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Not sure about today, but Sovtek and Electro-Harmonix were the exact same tube (made by Sovtek). Sovtek also marketed the re-issue EM stomp boxes because they owned the IP.

I was a dealer back when we had the guitar shop and we sold a LOT of sovetek tubes. Trey from Phish got tubes from us. He would use a set of four for two shows and then change them… we had a huge hoard of low hour matches quads that my partner got, since he actually played guitar.
 
I was just wondering the advantage of using silver-mica over metallized film...

Let's (not) get some Russian paper in oil caps!
 
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