Since I designed the Folcrom and I'm selling it, I don't expect anybody
to take my word for it that it's a good idea. The people who have been
buying it seem to think it's a good idea, as we've gotten a
surprisingly strong and positive response so far. I'll comment on some
of the commentary below.
Paul Stamler wrote:
Electronically it makes sense, with one exception, which I'll get to in a
moment. But unless they're using very high-quality switches for 20 years of
reliability, it's way the hell overpriced. A prosumer version of this could
go for perhaps $250, a higher-quality one (again, that mostly means better
switches) for $450-500.
I've had to defend the price of the Folcrom on several occasions when
DIY types suggest it's nothing more than a box of resistors and that it
should cost some ridiculously paltry amount. I could have thrown in
three dollars' worth of op-amps and a wall wart and it wouldn't be
passive, and nobody would complain about the price. The fact is that
the bulk of the parts cost lies in the chassis, the switches, and the
circuitboards. The difference between a passive circuit and an active
one does not amount to a meaningful percentage of the selling price.
The parts cost only accounts for about a quarter of the selling price,
which is typical for any gear you buy. Aside from parts cost, there's
also dealer mark-up, distribution costs, assembly labor, and facility
overhead to account for the majority of the cost. I'm not quite
getting rich off this thing. The dealers I'm working with and my
partners seem to think the price is a bit too low, and in fact I think
it's right about where it should be. In truth a person who's handy
with a soldering iron and friendly with a metal shop could build one
for about $300 if they soldered everything point-to-point, but that
would take a hell of a long time. The circuitboard design would be a
hurdle for most DIY folks, which makes the selling price of my box seem
pretty reasonable. Is it worth 30 hours of your time to save $400?
The Folcrom is sturdy and well-built, it looks good, and comes with a
warranty.
Like I said, electronically it makes sense; the gain staging should work
okay. If the nominal output level is -35dBu, and the nominal output
impedance is 150 ohms, that'll work just fine with a typical microphone
preamp. If the latter has an input equivalent noise level of -127dBu, then
you'll get a signal-to-noise ratio of 92dB, relative to nominal level, and
however much headroom your converters allow.
Exactly. Many folks don't immediately realize that any normal, active
mixer has a make-up gain amplifier built into it. The noise
performance of the Folcrom coupled with a good low-noise preamp is no
worse than a good quiet mixer with built-in makeup gain. In fact it is
even quieter because we left out all kinds of circuitry that's needed
in a traditional mixer but unnecessary in a DAW-summing application.
The fly in the ointment is the crosstalk spec and the switching. They say
it's -90 dB, but they don't say how that number's derived. My guess is that
it's the figure for how much leaks into the left channel when you're driving
the right channel, or vice versa. All very well and good, if that's all
that's punched in.
But they also give you the facility to swtich an input to both channels at
once, and that will degrade the separation some. I calculate that pushing in
one pair of buttons to switch that channel to the center makes the
separation more like -76 dB, and pushing in more pairs degrades it further.
Maybe the distinction's academic, but it should be noted.
It's actually very difficult to pin down an accurate, meaningful
specification for either crosstalk or noise. The measurements will
always depend on what's feeding the Folcrom and what the Folcrom is
feeding. The crosstalk specification we give (-90dB) is sort of a
best-case scenario for the real world. Paul's right that assigning
numerous channels to mono (both left and right output) will degrade the
crosstalk performance somewhat, but that degradation will be very
slight when the Folcrom is fed by a high quality source. In this
context I'm defining "high quality" as a very low-impedance source. A
theoretically ideal source, having zero impedance, would not degrade
the crosstalk whatsoever. Any high quality DAC ought to have a source
impedance of under 100 ohms, which will have a negligible impact on the
crosstalk even if several channels are bussed mono. I would put the
worst-case scenario, barring any unusually high-impedance sources, at
about -70dB.
Let's also remember that this is a mixer we're talking about. Its
output is a stereo mix that you're going to listen to on a pair of
speakers. Crosstalk between the left and right channels is about the
most unimportant specification I can think of. What's the separation
of an LP being played by a good cartridge through a pair of speakers
placed 10 feet apart? In reality, the potential "degradation" of the
crosstalk Paul describes will be absolutely undetectable to even the
most critical listener.
You could build a switchbox like this yourself, and if you remember to only
switch inputs to left or right, not both, getting center stuff by panning,
you could get very nice results, and use up a wad of solder. Of course, then
your results will depend on the quality of your D/A converters.
You absolutely could build a box like this yourself for less than half
of what you can buy mine for. But it'll be a lot of work. And if you
leave out the switches so that you can't assign an input to more than
one channel, nor mute an unused channel, then you'll shave the cost of
the actual mixer substantially. But then you'll need twice as many DAC
channels to feed your mono signals, and you'll have to build dummy
plugs to short any input that's not in use. Those items will cost
substantially more than the price difference between a stripped-down
DIY version and the store-bought version.
In summary, the Folcrom is actually a pretty good idea. We spent a
long time developing and refining the design, and in practice the
device works very well. Users have been thrilled with the ability to
change the sound of their mix buss by switching make-up gain
amplifiers. Its price reflects its production costs and is on the low
side of industry norms.
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