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Maybe not the best place to ask, but -- I had a random (simple) DIY phono preamp thought/question

mhardy6647

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#1
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:

1586868735133.png

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. :eek:

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 plentiful; a good investment for tinkerers). It might be way easier to make it quiet compared to DIY with vacuum tubes. I am a big fan of vacuum tubes for hifi (sorry!) -- but not as much for high-gain applications, due to noise and hum issues. Indeed, I do use a soiled-state umm, I mean solid state phono preamp myself! :rolleyes:

I mean, I could google for examples -- but I am really lazy, so I thought I'd ask! :)

Thoughts?

PS Actually I did google around a little bit -- but everything that started simple in DIY threads seemed to get ever more complex as folks tinkered.
I am poised to pull out the very old GE transistor manual(s) I have downstairs and see what sort of circuit(s) might be therein.
 

solderdude

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#2
Most likely there is something like this in it (active RIAA)

RIAA.png


using low noise resistors might lower the noise just slightly.
Maybe, just maybe changing the high resistance values for metalfilm might just slightly reduce the S/N ratio.

Don't expect miracles. Maybe when using low tolerance caps/resistors in the feedback path the RIAA correction might be a little more accurate.
 

Ivanovich

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#3
Searching AMZ I see that Pyle makes one for $13 and Behringer’s is $26. I would be curious about performance but not sure it’s all that critical given the medium’s other shortcomings.
 
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mhardy6647

mhardy6647

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Thread Starter #4
Searching AMZ I see that Pyle makes one for $13 and Behringer’s is $26. I would be curious about performance but not sure it’s all that critical given the medium’s other shortcomings.
The Pyle is a pile by all accounts I've seen.
The Behringer, I dunno.

Not lookin' for critical -- lookin' for fun. I've got the itch to build something different. Transistors, for me, are different. :)

PS This is old, but not entirely obsolete. Best comparative assessment of cheap phono preamps I've (ever) seen.
https://web.archive.org/web/20061112180327/https://audioxpress.com/reviews/media/403hansen2090.pdf

PPS Derp. I guess this is what got me to thinkin' about this in the first place. :oops:
https://www.audiosciencereview.com/forum/index.php?threads/reviewing-an-old-realistic-42-2109.11836/
 

JeffS7444

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#5
If I were to build a cheap non-DSP/PC phono preamp, I might just copy the circuit built into my Audio Technica 120USB turntable: Texas Instruments DRV602 or 603 (I forget) audio-specific opamps, low overall parts count, only single-rail 5V power supply needed and it plays nice, with no "pop" when powered up. I traced out the circuit at one point but forgot where I put my notes.

But why not spend a bit more money and make something that will provide more than a brief bit of amusement? For example, Douglas Self's "Devinyliser" brings something new to the table by cancelling out of phase low frequencies.
 
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mhardy6647

mhardy6647

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Thread Starter #6
... because I have a good phono preamp -- I just feel like playing. :)
 

sergeauckland

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#7
Searching AMZ I see that Pyle makes one for $13 and Behringer’s is $26. I would be curious about performance but not sure it’s all that critical given the medium’s other shortcomings.
Don't know the Pyle, but the Behringer is OK. Fixed gain and fixed loading, which means that it won't suit every MM cartridge, as they are very susceptible to loading, but apart from that, OK. Low enough noise, accurate enough RIAA equalisation and decent enough overload capability. I bought one a few years ago at a show as somebody was selling a new unused one for £10 for charity. Gave it to a friend, and I don't have a record of the measurements I took, but there was nothing there that surprised me. Hardly SOTA but Good Enough.

You can build a perfectly decent RIAA stage using a 5532 IC which will perform much better than the two transistor stage above.

S.
 

SIY

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#8
... because I have a good phono preamp -- I just feel like playing. :)
Go balanced. You can do it with a few opamps. with an RIAA network sandwiched in there. Cheap and effective. You'll never go back.
 

LTig

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#9
You can build a perfectly decent RIAA stage using a 5532 IC which will perform much better than the two transistor stage above.
This! And you need fewer passive components. I once build such a preamp for a good friend and mounted it inside of his Rotel integrated amp which had no phono input. Worked like a charm.
 

SIY

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#10
This! And you need fewer passive components. I once build such a preamp for a good friend and mounted it inside of his Rotel integrated amp which had no phono input. Worked like a charm.
Speaking of which, @mhardy6647 do you have Douglas Self's book on phono stages?
 

Ivanovich

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#12
Don't know the Pyle, but the Behringer is OK. Fixed gain and fixed loading, which means that it won't suit every MM cartridge, as they are very susceptible to loading, but apart from that, OK. Low enough noise, accurate enough RIAA equalisation and decent enough overload capability. I bought one a few years ago at a show as somebody was selling a new unused one for £10 for charity. Gave it to a friend, and I don't have a record of the measurements I took, but there was nothing there that surprised me. Hardly SOTA but Good Enough.

You can build a perfectly decent RIAA stage using a 5532 IC which will perform much better than the two transistor stage above.

S.
Interesting, thanks!

I bought the PP400 to have a stand-alone Phono Pre-amp to replace the UF-220 I had used to digitize a couple of vinyl albums some years back before I committed to streaming.

When it tried it using my old Empire TT I inherited from my Dad, it had a lot of hum and the right channel had all hum and no signal. I’m not sure a loading issue would cause that but I haven’t had time to troubleshoot further. I started thinking it’s a grounding issue somewhere and didn’t get passed continuity and anti-continuity test of the original cable, with new RCA jacks, which showed no issues.
 

TimW

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#14
For example, Douglas Self's "Devinyliser" brings something new to the table by cancelling out of phase low frequencies.
Thanks for mentioning this, I had never heard of it and find it interesting. Can't seem to find much info on it other than what Douglas Self has said himself. Would this circuit need to be used in conjunction with a typical high-pass filter? I'm considering buying the kit if it's still available.
 

JeffS7444

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#15
Thanks for mentioning this, I had never heard of it and find it interesting. Can't seem to find much info on it other than what Douglas Self has said himself. Would this circuit need to be used in conjunction with a typical high-pass filter? I'm considering buying the kit if it's still available.
No, so far as I can see, you just need a power supply to go with Devinyliser, while the other phono preamps (including the one incorporated into the Precision Preamplifier) already incorporate a high-pass filter. Getting ahold of Gareth Connor aka Signal Transfer Company may require some persistence, but quality of his product is good. Particularly for those products which incorporate 2SB737, 2SA970, 2SC2240 small signal transistors, small PC mounted heatsinks or headphone jacks, do buy a full kit if possible.
 
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#16
If you use an op-amp instead of transistors you can use a really simple circuit and the equalisation is suprisingly accurate. There are plenty of schematics about for these pre-amps, there is a John Lindsey Hood one for example. I think you would get better rejection of power supply noise using an op amp too. There are some cheap kits on ebay you could use as a starting place.
 
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#20
Yes I agree the NE5532 is excellent, people are put off it because it cheap but thats only because they mass produce it. You do need to use a bit of gain with it though, I seem to remember it can't be used at unity gain, but thats no problem in a phono pre-amp as it has a good bit of gain.
 
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