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

[D-500 Flogger]

I think we’re all foolish to not embrace a balanced line from the table to the phono preamp. Take advantage of the noise rejection of a balanced line! It just makes sense! It’s lower than a microphone output, and those are balanced.

J!m, while scouring the net earlier for any potential references to vinyl devos hot-rodding their RS 42-2111 phono preamps I happened across this extended troubleshooting session trying to suss exactly where RF interference was entering into the sound system...but only when listening to records.

It's an interesting read, with a nice plot twist. And it also reminds me of when I used to teach Avionics troubleshooting to The Next Generation airmen. Q: Is the thing that you are troubleshooting the perpetrator or the victim? And I would make them explain why they thought this. It was a useful method, because it would force them to look at the troubleshooting scenario from more than just 1 perspective...

 

[D-500 Flogger]

Interesting info there, funny how this thread appeared today. George (Pennysdad) recommended an $18 phono preamp which runs off a 9 volt battery (Thank you George!) I purchased one which arrived a couple of days ago. I didnt think it would be any good, but after hooking it up, wow, for $18 this thing sounds fine. Clean and balanced. Really exceeded my expectations. My usual phono pre is a $500 Project Tubebox DS which Performs very well. Big difference in price there. But for now, I am enjoying the battery powered one, its always good to try new things and they are handy to have as a spare.
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Derek92994,

We have a match -- here are the 2 I have to work with:



Your comments as to their sound quality are very similar to what I've read around the internet. Sometimes minimalism really pays sonic dividends!

 

[D-500 Flogger]

At long last, after scaling the phono preamp Everest, it's time to get back down to the base camp, and complete the circle.

In terms of sheer bang for the buck, quite possibly the all-time winner for a battery-powered turntable-based music system would be the following:

 

[D-500 Flogger]

Here's an actual Kenner Close 'n Play TV commercial from 1967. NOTE: We're in some rarefied air here, for only 839 true aficionados have watched this ad to date.

And for your viewing pleasure, here's a nice inside shot showing how the 'speaker' is driven directly off of the needle/tonearm:



(Edit: The batteries are installed under the purple cover towards the back of the cheerful plastic plinth.)

 

[D-500 Flogger]

At first I couldn't find anything representative in all of eBay...but once I did an advanced search for completed/sold listings this popped up.

The best part? Under 'Seller Notes':

"This is not a good record player, and that is exactly what makes it great. Sound is tinny & uneven..."



Then again, I think that the seller is being somewhat overly cautious with setting expectations -- check it out, right there on the box it says that this has "Beautiful Tone":



NOTE: The earliest reference I could find to the Kenner Close 'n Play in this forum was 17-Apr-2016.

Like they say, You gotta remember your roots!

3D

 

[J!m]

This is Perry’s reference player. (WOPL sniffer)

What more need be said?

With two phono preamps you can run true balanced- one for each channel!

Do you have a balanced in on your preamp? You may have just solved every problem- even those not yet identified by science!

 

[J!m]

One exercise I’d like to see, is to take the original board layout (schematic) and simulate it in SPICE. And then, see what optimization can be done in SPICE and then finally, rebuild it with what the simulation indicates as “the best” regarding noise, slew and accuracy of RIAA (which I don’t know if SPICE does because I don’t have it or use it).

It’s obviously a good design but may benefit from 40+ years of technology advancement to get the last 0.28% improvement.

Resistors of 0.1% tolerance and 1% film caps are not difficult or expensive now. You can build very close to simulation. Places like oshpark make nice boards for little money.

 

[derek92994]

Might get a couple more of these battery powered phono pres, then I can switch between the 3 turntables using a switch box at line level. I have to manually connect them to the Tubebox DS which is a little inconvenient at times. Also that will give me an option to run the 4th turntable from a battery pre. Will keep the Thorens 160 Super on the Tubebox and run the others on separate pres.

 

[derek92994]

I'm almost tempted to pull the cheap battery phono pre apart to see if any upgrades can be done, but that would require desoldering of the rca jacks and switch etc, not simple to just pull the board out so will leave as is. If anyone pulls one apart, please post a pic so we can see what components are on there.

 

[J!m]

Just build a 1u box with several of these optimized boards inside. Set loading and gain specific for each cartridge (how Wyn prefers to do it) and add a selector (maybe remote operated relays) and go!

Power with a Milwaukee drill battery…

 

[J!m]

I wouldn’t hesitate to take one apart.

Solder sucker will pull enough off to get the jacks out with minimal damage.

You want to make new boards anyway!

 

[derek92994]

I wouldn’t hesitate to take one apart.

Solder sucker will pull enough off to get the jacks out with minimal damage.

You want to make new boards anyway!

Will sacrifice one as a guinea pig once I have multiple units

 

[Gepetto]

Interesting info there, funny how this thread appeared today. George (Pennysdad) recommended an $18 phono preamp which runs off a 9 volt battery (Thank you George!) I purchased one which arrived a couple of days ago. I didnt think it would be any good, but after hooking it up, wow, for $18 this thing sounds fine. Clean and balanced. Really exceeded my expectations. My usual phono pre is a $500 Project Tubebox DS which Performs very well. Big difference in price there. But for now, I am enjoying the battery powered one, its always good to try new things and they are handy to have as a spare.
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That is the Rat Shack one Darcy. I am sure the same unit was marketed by many companies.

 

[derek92994]

That is the Rat Shack one Darcy. I am sure the same unit was marketed by many companies.

Do You know of any possible upgrades to the units?

 

[Gepetto]

Do You know of any possible upgrades to the units?

I really haven't studied it much Darcy...

 

[derek92994]

I really haven't studied it much Darcy...

I have ordered some more, when they arrive will disassemble and have a look.

 

[mr_rye89]

Bump for interest!

J!m's thread about the Wyn Palmer phono preamp:

https://forums.phxaudiotape.com/thr...mance-low-buck-phono-preamp-diy-project.9891/

 

[derek92994]

Found a schematic for the Rat Shack Pre

 

[J!m]

Who can put that into SPICE and refine it?

Build two and you can run balanced.

 

[D-500 Flogger]

I'm almost tempted to pull the cheap battery phono pre apart to see if any upgrades can be done, but that would require desoldering of the rca jacks and switch etc, not simple to just pull the board out so will leave as is. If anyone pulls one apart, please post a pic so we can see what components are on there.

I looked everywhere for a good photo of the component side, but all I found was poorly lit, shadowy, no depth of field, or just plain blurry...

So in the interest of science I took one for the team, and this evening I disassembled my newly acquired NOS unit. What you see is exactly what was shipped from the factory, w/no added value by yours truly:


(Nikon D7000, 35mm ED prime, f/22, ISO 100, 1/60 sec, dbm)

This photo plus the schematics should make it pretty easy to figure out what parts you would like to selectively upgrade...

NOTE: The 4 transistors in this circuit (Q1 / Q2 / Q3 / Q4) are visible here, but in person are downright diminutive. Depending upon the size of the screen you are using, this is a macro photo. To get a better feel for the real-world dimensions, the actual distance between the centerlines of the + & -9V battery connections is 1/2". (Or 12.7mm for those that were raised to think metric.)



The bottom line is that this is looking to be an ideal low-risk/non SMD/small scale project where someone new to the hobby can practice their modding/electronic hot-rodding chops. (!)

Cheers --

3D