Audio Alchemy PPA-1 Phono stage.
One of the Best Phono Preamp for $$$$ Very musical with dead quiet MC! I'm the original owner. Comes with the original packaging.
Ultra-Quiet, Fully Discrete Phono Stage with No Op Amps
Audio Alchemy's PPA-1 phono preamplifier uses all-analog,
discrete FET gain and EQ stages to transform the microscopic grooves in vinyl
records into stunningly lifelike music. It includes all the features that
serious vinyl enthusiasts demand, such as continuously variable input loading,
MC/MM gain switching and XLR and RCA outputs. It can also be upgraded by adding
the PS-5 power supply, which can simultaneously power the PPA-1 and one other
Audio Alchemy component, such as the DDP-1 digital preamp.
Fully Discrete Circuit With No Op Amps
Any phono preamp has to incorporate the RIAA playback EQ curve
to correctly handle the musical signal from the phono cartridge, and this
basically consists of a bass boost and a treble cut. There are all sorts of
ways to accomplish this, using various types and combinations of active and
"The one that sounds the most musical to me is the
combination of a discrete FET [field-effect transistor] input stage, a passive
treble roll-off filter, and an active EQ circuit for the bass boost," says
Peter Madnick, the founder and chief engineer of Audio Alchemy – and the
cofounder of the original Audio Alchemy back in the late 1980s. "The basic
circuit concept dates back to a phono preamp I designed for Dennesen
Electronics in the 1980s. I’ve used it a few times since then, but the PPA-1 is
the first chance I’ve had to implement it the way I’ve always wanted to: a
fully discrete circuit with no op amps, a very quiet, well-regulated power
supply, and versatile tuning options."
Magical Analog Musicality
As Audio Alchemy sees it, analog signals from vinyl records are
already perfect when they leave the phono cartridge. All they need is to be
handled with the utmost care in their path to the preamp. That's why Audio
Alchemy use all-discrete, ultra-low-noise FET circuits for the PPA-1's RIAA EQ
and gain stages, with no integrated circuits in the signal path.
With a phono preamp, especially running an MC cartridge, the
gain has to be very high – in this case +67 dB – and, of course, the higher the
gain the more you have to be careful about noise. "One of the main things
we did to minimize noise was use multiple FETs in parallel in the input
stage," says Peter. "When you run two transistors in parallel, you
get a theoretical -3 dB reduction in noise. We use eight FETs per channel –
four in parallel for positive, four in parallel for negative. This reduces the
noise to virtually imperceptible levels."
Low Noise Power Supply
After lowering the noise levels in the preamp and EQ circuits,
the power supply becomes key. The PPA-1 is very quiet, even with its stock
power supply, which uses an AC transformer and not just a switching-type power
supply like you usually get with audio products. The incoming AC is rectified,
and then it's run it through a large capacitor bank. Audio Alchemy uses a
circuit called a capacitor multiplier, which increases the effective
capacitance. "Coming out of the capacitor bank we have very smooth DC voltage,
plus those capacitors store electricity and release it when the preamp needs
extra power for highly dynamic musical passages," Peter notes.
The PPA-1 follows the capacitor bank with low-noise DC
regulators, which in turn are followed by RLC [resistor-inductor-capacitor]
filters that trap high-frequency noise.
According to Peter, "We also carefully researched the
internal isolation for the different circuit elements. Everything that might
interfere with something else is isolated from it, and we use star grounding to
make sure all the various circuits have the same ground reference."
Still More Noise Control
After all of this attention to lowering the noise floor, Peter
wanted to make sure that there was nothing inside the chassis that could
produce its own noise. So there’s no display, no microcontroller, no computer
interface, no wireless connection, no digital or RF or computer-based
components of any kind. A nice side benefit of this is that the front panel is
simple: just power, input selection, and mute buttons.
Transformations That Suit Any System
Serious vinyl enthusiasts need more than just the basic options,
so the PPA-1 gives you what they need. Load impedance is independently,
continuously adjustable for both inputs, so optimal performance can be achieved
with any cartridge, and you're not locked into specific settings. Either input
can be set for MC or MM gain, and balanced XLR outputs are provided in addition
to single-ended RCA outputs.
"Of course, you can set the gain for MC or MM cartridges,
and that’s for each input, so you can have two MC, one MC and one MM, or two
MM," says Peter.
"What I’m most proud of is the way we set up the adjustable
cartridge loading. Controls on the back let you select 47 kΩ loading for MM
cartridges (and some people like that for MC, too), or adjustable loading from
1 ohm to 1000 ohms for MC cartridges." This gives the listener lots of
flexibility to either use the cartridge manufacturer’s recommended loading or
experiment to find a loading they like better.
It’s very easy to adjust the loading precisely, because the
PPA-1 includes contact points on the back panel that let you measure the
loading for the left and right inputs of channels 1 and 2. "All you need
is a $10 digital multimeter to measure the load impedance," Peter notes.
"Touch the meter probes to the contact points, and turn the knob on the
back until you have the load setting you want."
Easy Upgrade Path with Optional PS-5 Power Supply
As great as the PPA-1 sounds, it can sound even better! Audio Alchemy
provides an easy upgrade path via the optional PS-5 outboard power supply,
which offers superior filtration, tighter voltage regulation, lower noise and
greater energy storage. Adding the PS-5 makes the PPA-1 more dynamic, too.
"All the AC power is isolated in the PS-5, so the PPA-1
sees nothing but filtered DC," Peter explains. "It also provides a
higher supply voltage: +/-20 volts DC. The stock power supply is 9 volts AC,
which gives you a little more than +/-3 volts DC. The PS-5 also has a much bigger
capacitor reservoir than what’s inside the PPA-1. So with the PS-5, you gain a
lot in terms of dynamic capability."
§ Freq. Response: 10hz-20Khz +/- 0.1db
§ THD distortion: <.005% at 1Khz
§ S/N ratio high gain input shorted:
67db unweighted; 76db A-weighted
§ S/N ration low gain input shorted:
84db unweighted; 90db A-weighted
§ Total Gain high setting: +67db
§ Total Gain low setting: +49db
§ Phono input impedance switchable: 47K
OHM or 1-1K Ohm variable
§ Output impedance: unbalanced 100 OHM;
balanced 100 Ohm per leg
§ Input sensitivity at 1Khz high gain:
450uV input for 1V balanced output
§ Input sensitivity at 1Khz low gain:
3.5mV input for 1V balanced output
§ Crosstalk high gain at 1Khz: >88db
§ Crosstalk low gain at 1Khz: >100db
§ Dimensions: 5.5" wide x
3.5" high x 11.6" deep
§ Weight: 9 lbs.