I just had a random phono preamp thought

mhardy6647

Not sure why I was thinking about phono preamps, but I was.
I was thinking about the proliferation of really, really cheap add-on (MM) phono
preamp/EQ boxes that every retail & catalog electronics supplier carried back in the good ol' days. You know, this kinda thing:


source: http://www.radioshackcatalogs.com/html/1977/hr040.html

So, in 2020 AD, they call these Little Rats and there are clowns hucksters audiophiles who sell upgraded examples (new caps) for, like, two hunnert smackers.

The mind boggles.

So, here's what I was thinkin'. There are lots and lots of really good, cheap transistors nowadays. These gizmos were (are) extremely simple -- although I'll admit, I don't even know if they use active or passive RIAA networks (I assume the latter...?).

I'm just wonderin' if anyone's knocked together a drop-dead simple, discrete SS phono preamp along the lines of the "Little Rat" and its peers -- but using modern transistors and capacitors (and resistors, too...)? Seems like it would be a cheap and fun exercise.
One could run it with batteries, off a wall wart (switchmode or linear), simple linear P/S, not-so-simple linear P/S, or a bench/lab P/S (for those who have such things handy -- they're cheap and plrentiful; a good investment for tinkerers). It might be way easier to make it quiet compared to DIY with vacuum tubes.

I mean, I could google for examples -- but I am really lazy, and it is a holiday, so I thought I'd ask!

Thoughts?

verb

Doc I’m amazed at your random flights of fancy always seem to be destined as a published paper in audiophile circles!

Btw, sorry but I’ve got nothing for ya! Following though!

motorstereo

I remember buying one of those things some 45+ years ago. I had moved up from a ceramic cartridge to a mm and my botl all in one didn't have the proper input for the mm input.
Going from ceramic to mm now that was quite an upgrade at the time for those that never had a ceramic cart that tracks at ounces as opposed to grams.

mhardy6647

... on the other hand, there were (and, I think, still are) some "audiophile" ceramics.

In the old days, there was EV's "MagnaCeramic" line of high, and low, output ceramics, for example -- these were at least as expensive as the better/best MMs and MIs of their day.

Here's one, e.g.,


source: http://www.alliedcatalogs.com/html/1961-200/hr097.html
The price of this EV is the same as a Shure M7D in the same catalog (i.e., at the top end of all phono cartridges in 1961).

Grado once also had a line of ceramics. Old Joe Grado invented and patented a moving coil design, sold MC cartridges early in his career, but quickly abandoned them for ceramics and moving iron (MI, aka "variable reluctance") designs. I've always been amused by that (but then again, I was and still am a Grado fanboy).


source: https://www.lencoheaven.net/forum/index.php?topic=22033.0

A Grado ceramic from the 1960s on a Technics SL-Q2.
DSC_3849 (2) by Mark Hardy, on Flickr
DSC_3850 (2) by Mark Hardy, on Flickr


More recently (it's all relative) there were "solid state" cartridges -- marketing speak for ceramic, aka piezoelectic, cartridges. MicroAcoustics (MA) was pretty successful with their line (which are still held in no mean regard in some circles), and Panasonic's "Strain Gauge" cartridges were/are kind of legendary. These were low output, MM phono-compatible cartridge designs (for better or worse), like the above mentioned EV.

The MA cartridges had onboard networks to reduce their output (I think) and to de-equalize them so that they could be plugged into an MM phono input. I think that the Panasonics had an outboard adaptor box that did the same basic thing.

MA QDC-1e on a Philips 777 tt.
DSC_6962 (2) by Mark Hardy, on Flickr

I've got one MA cartridge (i.e., the one above ) - the midrange is absolutely glorious; everything else is -- OK. In fairness, the condition of the stylus is utterly unknown, and I never set the cartridge up with a lot of care, so it may well be capable of more than I have let it be.

Ceramics do offer some intrinsic advantages -- they have a constant-amplitude response characteristic (as opposed to the constant-velocity response of an MM, MI, or MC cartridge), so they're self-equalizing. That's why the MA cartridges mentioned above have on-board 'electronics' that make their output look like that of an MM or MI cartridge!


source: https://www.vinylengine.com/ve_downloads/index.php?micro-acoustics/micro_acoustics_phono_cartridges_catalog_1977.pdf

Here's an article that looks like a good one-stop shop on this topic I haven't read it carefully, so I cannot guarantee its accuracy -- but it's a start if anyone's interested

http://www.enjoythemusic.com/cartridgehistory.htm

PS I may not have characterized the 'strain gauge' carts terribly accurately; I am going from memory I am on a short leash this AM (got some stuffs to do anon) so I will update later as and if necessary. I know youse guyses love this kind of stuff!

afterburnt

https://youtu.be/KKy9IPN31gs

My random thoughts

jdjohn

@mhardy6647 You probably mean a kit of some sort, but there are several cheap Chinese pre-made options on eBay. Seller 'doukmall' has several, of which most are the tube variety, but here are some internal pics of a few SS options.

They say this one is 'inspired by Shure', but no mention of how.


Little Bear is a popular minimal, normally tube, but here is a SS:


This one is based a Nait 2 phonostage from the '80s:


Nobsound:


Douk:

mhardy6647

I don't mean a kit I mean a schematic.
I have an urge to tinker.
None of those pesky lethal voltages that plague the vacuum tube stuff that I usually tinker with, either. Run the dang thing offa batteries!

I have been fiddlin' on and off, with a dysfunctional old(er) Samsung flat-panel TV (long, long story). I figured 99.9% most likely that the problem was (were) one or more bad P/S electrolytics -- but, noooooooooo...





Interacting with the outside world via Zoom has given me (yes me) an urge to come up with something a little bit bigger than the laptop displays we've got around here. I've solved the audio problem but the video is a higher bar. But I digress...


(Easter Sunday service... via Zoom! )

At any rate, fiddling with soiled state stuff has some advantages, and I thought it would be fun to recreate some simple passive RIAA ss design with gooder, moderner components either point to point or on a perfboard.

That's all -- nothin' profound.

I actually have the genesis of a pretty high end DIY phono preamp in the form of PC boards, tubes, and a power transformer. I actually just need to source the passives for it and devise some sort of enclosure... but that's a bigger project than I am up for right this second.


Oh, man, I sound even more ADD than I believe actually I am today!

[Deleted User]

You might want to consider building the Realistic 42-2101, you can find the owner's manual which has the schematic drawing at HiFiEngine's website.
Another choice very popular with the folks in Japan is to do a search for the Toshiba TA7122AP a three transistor preamp mini-module that can be configured into a fine sounding phono preamplifier with just a few external components. There are usually a few available on eBay for a fairly modest sum.
If you need parts, let me know, or inverse RIAA testing with THD and IM distortion measurements.

tonyp063

Mark,
I've not made it yet, but the schematic in this intrigues me .

https://www.ti.com/lit/ds/symlink/lme49720.pdf

FTGV

tonyp063 wrote: »

Mark,
I've not made it yet, but the schematic in this intrigues me .

https://www.ti.com/lit/ds/symlink/lme49720.pdf

I built one based on this data sheet and using that op-amp. The passive parts were scaled to slightIy different values. The polystyrene and polypropylene caps and metal film resistors were tested and matched to better than 1%. I'm very pleased with the results in my modest vinyl set up. Simple , quiet and clean sounding little circuit.

mhardy6647

Thank you, gentlemen, and I appreciate the leads, but I am tryin' to avoid them little squashed bug op amps in this Gedankenexperiment. Tryin' to think like Nelson Pass, you know? I might have to take a few big ol' hits of ozone to pull that off, though, of course.
(oh, and become a master circuit designer with a phalanx of credentials...)

hmmm... did he do a discrete DIY phonostage design? Guess that's worth a look.

Guy on ASR popped up with this interesting page, BTW (and FWIW):
http://www.douglas-self.com/ampins/discrete/2Q-RIAA/2Q-RIAA.htm

FTGV

Yes, I realize you didn't want to use any of those wretched 8 pin devices. I was just giving Tony some feedback on the schematic he posted.

voltz

I like the way you think Doc!!

I been so in love with my Vincent phono amp with separate power supply...so can you and this to your design? hint...hint...

https://www.audioadvisor.com/prodinfo.asp?number=VIPHO701

p.s. I had a Graham Slee phono a Canadian brother here bought and love d so much he upgrade to a higher model of it..I only sold it because it was so light weight.. the heavier cables pulled it off my Rack then I got the Vincent and found Vinyl heaven for now!