Equalization, amplification and location. That’s a phono preamp in a nutshell. But “the devil’s in the details,” as the saying goes. And then there’s the grounding minutia…
Last summer, in the introduction to my confession of having recently tumbled down the vinyl rabbit hole, I shared a photo of Schiit’s second-generation Mani, a phono preamplifier.
Ever since then, I’ve been tempted to take one apart to see what’s inside. That said, they’re not cheap; the Mani 2, for example, costs $149 (black) or $159 (silver) brand new, with the larger Skoll model going for more than twice that amount: $399-$479, depending on color and optional features. Other companies’ audiophile-targeted products’ prices are even more stratospheric.
So, when I subsequently came across a Pyle PP444 phono preamp promo-priced on Amazon’s Resale (formerly Warehouse) sub-site for only $10.46, I redirected my curiosity to it instead.
It’s certainly more elementary, with gain compatibility for only moving magnet (MM) cartridges, not also including innately quieter moving coil (MC) and other cartridge types, not to mention a diversity of cartridge impedance loading options. The settings for all of these (plus selectable low frequency filtering to reduce “rumble”) are showcased in this Mani 2 underside stock shot.
But hey, the PP444 offers at least one upgrade over its Schiit competitor…both dual RCA and ¼” tip-ring-side (TRS) output options!
Ahem. And did I mention it cost only 10 bucks and change?
Fundamentals
Let’s cover RIAA equalization first. Here’s a requote from the initial entry of a two-part early-2012 Design Idea series that I conveniently came across as I was preparing to begin writing.
The hi-fi phono preamp should have an accurate RIAA equalization, which is a technical standard of frequency response used on vinyl records during the playback and manufacturing. Once vinyl masters are cut, below-1 KHz frequencies are attenuated to prevent the stylus from crossing over into the groove. Higher frequencies are amplified in order to prevent noise from the disc surface. The RIAA equalization of phono preamps increases the lows and attenuates the highs so the original analog signal can be recreated.
Next, following in the order listed in the subhead, what about amplification? The end goal is to output a dual channel (assuming a stereo turntable) line level signal ranging from approximately 0.3 to 1.2 V. Using a moving magnet cartridge as the source, the resultant signal to be amplified is ~3 to 6 mV, translating to ~40 dB of gain necessary in the phono preamp stage. Moving coil cartridge outputs are even quieter, in the range of ~0.1 to 0.5 mV, necessitating ~60-70 dB gain.
And location? Although my Audio-Technica AT-LP60XBT is an entry-level turntable, its flexibility neatly allows for exemplification of all three common phono preamp location options.
The AT-LP60XBT offers a built-in phono preamp which the user can selectively enable to directly drive, quoting from my earlier coverage, a “conventional audio preamplifier, integrated audio amplifier or even more integrated audio receiver” via respective RCA sets. The turntable’s integrated phono preamp stage presumably also finds use ahead of its A/D converter, leveraged for its Bluetooth and USB digital output options. Switch off the integrated phono preamp, on the other hand, and the AT-LP60XBT reverts to sending innate moving magnet cartridge signals over those same RCA connectors.
One alterative phono preamp location is within the aforementioned “conventional audio preamplifier, integrated audio amplifier or even more integrated audio receiver,” which subsequently connect to the turntable via a dedicated “phono” or equivalent input set. Such setups were historically common, although less so as vinyl faded from popularity (at least temporarily!) in favor of CDs and other optical disc formats, not to mention digital downloads and streams.
And, of course, the third location is as a discrete device in-between the turntable and the audio preamplifier, integrated amplifier or receiver, such as with today’s showcase Pyle PP4.
Peering inside
Speaking of which, here’s our patient, as usual accompanied by a 0.75″ (19.1 mm) diameter U.S. penny for size comparison purposes and beginning with admittedly bland outer package shots.
Top.
Front.
Left side.
Back.
Right side, showcasing the Amazon Resale sticker commonly seen in such dissections.
And bottom.
Enough of the brown cardboard monotony; let’s get inside.
Various paperwork bits (PDF).
And now for the good stuff.
A “wall wart” power supply, of course.
And, last but not least, the star of the show. Same photo perspective sequence as before.
Top.
Front.
Left side (See those screws? Hold that thought).
Back.
Right side (ditto re the side screws).
And bottom.
Grousing about ground
Remember those two screws on each of the two sides? Buh-bye.
Speaking of screws, let’s next look at this one in the back corner, intended for the ground connection between the phono preamp and the turntable.
My suspicion is that it’s the single biggest reason why phono preamps end up getting returned for refund (like the one I ended up buying via Amazon Resale). Why? Take my Audio-Technica AT-LP60XBT turntable, for example. It doesn’t have a ground connection.
Instead, the negative shield of one or both RCA cables between it and the phono preamp does double-duty as the ground tether. But if you don’t realize this, all you see is a ground connector sitting there unpopulated and seemingly doing nothing at the phono preamp end of the cable span, figure your turntable is therefore incompatible with the phono preamp, and return the latter.
Or, conversely, what if your turntable does also have a ground connection? In this case, you might be more familiar with other audio peripherals, such as a streaming receiver or tape deck, which don’t have ground connections. And you might also be in a hurry to listen to your turntable, so you don’t bother reading the instructions, instead connecting only the RCA cable pair (and overlooking the both-ends ground wire in the process). And you then end up with nothing but an annoying hum, which once again compels you to return the phono preamp.
Sigh.
Onward. Four more screws to go, two on the back panel and two more keeping the PCB connected to the bottom panel (which is also connected to the back panel, but I digress).
And detachment (or, if you prefer, nirvana) is achieved.
My, what thick traces you have!
The dominant (and only, actually; everything else is seemingly done discretely) IC on this side of the PCB is Unisonic Technologies’ UTC4580 (PDF), also commonly referred to as the MC4580, a dual bipolar operational amplifier with audio tone control capabilities, the latter presumably tasked with RIAA equalization duties. Next to it, in the lower left corner, is the power LED.
Now for the PCB backside.
Not much of note here, unless you’re into solder points. That said, look at the resistor silhouettes between many of them. Now go back to the PCB frontside, and you’ll see hints of component-info outlines underneath and to the sides of the passives and other components. Manual assembly assistance, I ‘spect. Nifty!
I’ll close with four consecutive (in clockwise order) side views, starting with the front.
And with that, I’ll wrap it up and turn over the keyboard to you for your thoughts in the comments!
—Brian Dipert is the associate editor, as well as a contributing editor, at EDN.
Related Content
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- RIAA Standard Hi-Fi Phono Preamplifier
- Preamplifier Input From Moving Coil Head
- Peeking inside a moving magnet phono cartridge and stylii
- Assessing vinyl’s resurrection: Differentiation, optimization, and demand maximization
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