Tag Archives: phono preamplifiers

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl

Decaf

The taste of decaf coffee isn’t the same as caffeinated, in the same way that Diet Coke, vegetarian bacon, or high-end MP3 players aren’t the same as what they started out as.

It’s good we call out differences between the original products and their derivatives, but at times it can seem a bit odd. As vegetarians, we enjoy a meat-like substance that resembles strips of bacon, but bacon it is not. Were it actually animal flesh we would not eat it.

The fact it isn’t what it purports to be is the reason we engage with it.

Take for example a product said to have a tube-like sound. We ignore the fact it is 100% solid-state because that description might not connect with our image of good sound any more than a package of Vital Wheat Gluten, Canola Oil, Adzuki Beans, and Buckwheat Groats seems appetizing.

It’s bold indeed to produce products that stand on their own merit and challenge stereotypes: AC regenerators, separate phono preamplifiers, CD transports, vibration control feet, active grounding systems.

I love the taste of a great cup of coffee, caffeine, and all.

Asheville, Walnut Cove, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

Rumble

In the volumes of email I receive I get some great questions. Mark, in San Jose California, was asking why phono preamplifiers no longer offer switchable rumble filters.

I think it’s a great question. I remember years ago when nearly every phono preamplifier had a switchable rumble filter and I also remember hating it. Every time I clicked that filter all the bottom end of the recording seemed to vanish along with the unwanted woofer movement. Those high-pass filters of the day were pretty aggressive.

PS Audio has been building phono preamplifiers since our inception in 1974 and we have never offered a switchable rumble filter. However, every one of those preamplifiers had built-in rumble filters and that, Mark, is the most likely answer to your question.

By building in a fairly aggressive filter we can keep its frequency low enough so as not to negatively affect sound quality. We do this with a multi-pole high pass filter that has the dual role of keeping any small DC issues from occurring and, at the same time, eliminating rumble without impacting bass.

I am going to guess that what’s actually different is not the lack of rumble filters, but the lack of switches to toggle them on or off.

 

Walnut Cove, Asheville, Biltmore Forrest and Western North Carolina’s Audio and Home Theater specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

Separates

Where did the idea of separates come from? Planned or piecemeal?

We started with all in ones: radios with speakers, consoles with turntables, complete systems. And then along came the separates, tearing apart the integrateds.

The first separate I was aware of came from my father’s system. He had a separate tuner, turntable, amplifier and preamplifier. He was the first mix and match person I had met and I remember him telling me the components were cobbled together with the idea of best in each field; it caused me pause then as now. Did these specialist companies, like H.H. Scott, who made separate tuners in the 1950′s, form by master plan to build only tuners and later extend into full lines of products as an afterthought?

My curiosity extends to how separates developed and then morphed into full line offerings. In our own case, PS Audio, we first ventured into making separate phono preamplifiers because we could, there were no alternatives, and we felt we had something of value to offer. What followed those phono preamplifiers evolved from what we knew best. My guess is few companies like ours had sights set on complete systems from the beginning.

Separates that grow into systems came not so much by calculated design, but piecemeal on an evolutionary timetable.

Asheville, North Carolina ‘s Home Theater and Audio specialists present Cane Creek AV and Paul McGowan – PS Audio, Intl.

2400 year advice

Every piece in an amp, preamp, DAC or link in the music reproduction chain matters; even the chassis itself. To believe otherwise ignores Aristotle’s insight the whole is greater than the sum of its parts. For more than 2,400 years we have known that everything matters and the passive bits in our hifi products are no different.

I first learned this lesson designing the original PS Audio phono preamplifier forty one years ago. Our design used a passive RIAA curve consisting of two capacitors and two resistors of exact value; their tolerance should not exceed 0.1%. Precision resistors are easy to find, capacitors are a different story. One of the capacitors was an odd value; 0.0233mF when the standard is 0.022mF. The difference between the two is small but ignoring the 0.0013mF meant a deviation from the RIAA standard we were unwilling to consider. Capacitors can be stacked together to form new values: a 0.022 and a 0.001 might get us close, but the easiest method of finding what we wanted was to hand-measure from selected bins of lower tolerance parts instead.

Every designer has boxes of parts accumulated over years and ours proved a treasure chest for building prototypes during the initial design phase. The problem we kept running into was consistency of sound; even seemingly identical designs sounded different. Building matching pairs of phono preamplifiers was at a standstill until we could figure out what affected differences in sound. Each of the reference designs were identical from the viewpoint of the schematic, differing only in the parts themselves: in one we used polystyrene capacitors for the curve, the other polypropylene and in a third, ceramic; and each had a sound different from the others.

It took a lot head scratching to determine the cause of sound differences between units; each measured identically. But once we settled on a common capacitor type, unit-to-unit differences vanished. This bit of insight proved invaluable as we moved forward with the design process and remains a hallmark for those building with the ear as the best piece of test equipment owned.

It all matters.

Enjoying or working?

Happy December! I was just watching some silly show last night and was reminded the Mayan calendar says the world ends in 21 days. Let’s make the best of what we have left icon smile Enjoying or working? Sorry, I just couldn’t resist.

We’ve been focusing on the art of listening and the subjects seems to have generated some measure of comment. One of the more interesting points made was the challenge of listening as a designer is different than listening as a music lover. Of course you can have both but if you, like me, make your living designing audio products then sometimes we have to “work” when we listen.

I cannot speak for other designers, most of whom are far more gifted than I, but I can relate to you the process I went through to understand the cause and effect of designs and parts. Indeed, when I hear a Hi Fi system displaying certain character traits I can usually tick off the most likely candidates of why I hear what I do. That skill is something learned over many years of trial and error.

The education started many years ago when were were working on the first phono stage the company manufactured. There are two main schools of thought when it comes to designing a phono stage and both concern the way the RIAA curve is implemented: actively or passively (we’re ignoring digital schemes because in the early 1970′s there was no such thing).

The RIAA curve is a serious bit of EQ, spanning a 40dB range. It’s essentially a huge double low pass filter – meaning it rolls off higher frequencies – starting at 20Hz and reduces everything above that. LP’s are mastered with the opposite EQ: exaggerated highs and reduced lows. This EQ is implemented to reduce noise and increase the playing time available and the RIAA curve in a phono preamplifier reverses this so you get a flat frequency response.

Most phono preamplifiers place this EQ curve in the feedback loop of a single amplifier and this is known as active EQ. Another way to handle the EQ is passively: meaning the components used to roll off the highs are not in an active feedback loop but instead, the passive components are placed between two amplifying blocks.

Because we were using an Audio Research tube phono stage as our reference and it used a single stage active RIAA, we did exactly the same thing in our first designs. We made sure we copied the exact values of the EQ network and even made sure the parts themselves were identical to the ones AR used so there would be fewer differences in our solid state design vs. their tube design. We weren’t even close in the way ours sounded next to theirs despite the fact the measured results were nearly identical and – despite the fact that our little solid state design sounded remarkably good as a simple line stage relative to theirs. It was when we tried to implement the RIAA curve that everything fell apart.

Tomorrow we start to relate what we’re hearing to what’s happening.

Paul McGowan – PS Audio, Intl.