Recording - April 2017 - 62

Avedis Audio Electronics E27 500

Adam Taborowski, Avedis Kifedjian, and Mateusz Wozniak

Tell me about the 1122 op amp. Since it was made to work
in older API gear, is it similar to the API 2520 op amp?

The 2520 API op amp goes back to the late '60s and had
evolved by the mid to late '70s with the Melville and Huntington variations, which are the ones that I studied and measured.
It's similar in that it's still a discrete hand-built op amp, but I used
different components inside to improve stability, noise performance,
and just to make it more reliable-especially since when an opamp fails you can't fix it.
It's like if somebody gave you the recipe for making chocolate chip
cookies. First you make it exactly like that recipe and you learn about
it... but once you have learned it, you make little adjustments, right?
Brown sugar for white sugar, or whatever. There was certainly some
small room for improvement-for example, ceramic caps with a 20%
tolerance were horrible for audio. Modern quality ceramic caps have
a 2% to 5% tolerance, and can withstand a higher temperature. So
why would you not use that?

So how did Avedis Audio Electronics come about?

When I made the 312A for Brent, he actually put my first
name on there with a Trademark symbol...

So basically Brent kind of launched the company for you!

Yeah, he put me in a position where I had to trademark my first name
[laughs]. Avedis is an old Armenian name, but he said, "It'll make a
good company name; people don't know what it means." The symbol
for the company is a 1960s schematic symbol for an op amp. So that's
how it all got started; the first product that I made on my own, using my
own symbol and name, was the E15.

Which was the precursor to the E27. Can you tell me
about the evolution of the two?

Brent asked me to design an API-style EQ like a vintage 550A.
While I put the buttons and knobs in the same place as 550-style
EQ, the insides are really different. The calculations, the topology, the
way that I used the amplifiers and the filter design, make it unique.

And the E15 was an Avedis product, not BAE?

Yes, and interestingly when the E15 came out in 2003,
basically Brent Averill and API were some of the only companies
making anything for the 500 Series. There was no other company
actively making anything for the 500 Series at that point.
My E15 was the first 500 Series EQ to come out that was
all discrete and with a balanced transformer input. All of the
API EQs in the 1970s and 1980s were either unbalanced, like
the 550A or 553, or they were electronically balanced, such
as the 554 and the 560s that used electronically balanced (IC
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RECORDING April 2017

chip) inputs. Nowadays, how many companies are making 500
Series modules?

I have lost track!

It's so many, which is good, but when I made the E15, I put it out
in Brent's shop for people to look at, and back then nobody really
cared about 500 Series. Nobody wanted to commit to that format.
What helped out was, Warren G [the rapper] came in to buy some
preamps, and he looked at the E15 EQs, and he said "How much
are these?" I said "These are $750." That's how much they were at
that time. He said, "What? These little things are $750 each?" And
I say, "Yeah, you know, it's high quality parts... expensive transformers, switches and caps and all that, custom-made knobs, reliability,
high headroom, low noise, all this stuff comes at a cost, you can't
make it cheap." So he bought a pair and then after that, all these
other guys heard them in his studio and ended up buying some. My
first customers were all from the LA Gangsta Rap scene.

How did the E27 come about?

It was probably 2005, simply because I found some switches that
had more positions and I added more frequencies. That became
the E27, and I abandoned the E15. E just stands for Equalizer
and 15 means 15 frequencies total: five per band, and there are
three bands. E27 is nine frequencies per band over three bands.

I know they visually look similar, are they the same inside?

Yes, it's the same Jensen transformers, the capacitors are German-made Wima or Japanese-made Panasonic, which I can't
get any more, so I have to find them from old stock warehouses
and buy as many as I possibly can.
I use Grayhill switches; they actually cost a little more money,
but the Grayhill switch is PC mount, which makes for more reliable manufacturing. It's a dual stacked circuit board design with
the frequency filters on a daughterboard, and the amplifiers and
transformers on the motherboard.

That's a lot jammed inside a 500 Series module.

Yes, but should it ever need servicing, it's easy to do and you can
get to any component inside. One advantage to through-hole vs.
surface-mount components is that many years from now you can
still easily service through-hole gear.

What kind of EQ is the E15 and E27?

Unlike the original API 550A, which is a twin-T topology, this
is an inductor simulator, which is actually what it does. I like
the sound of well-made inductors. so I use a Class-A amplifier
and I put the capacitors around it that make it act as if it's got

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