HAPPY NEW YEAR
Greetings in the new year. I thought I'd reflect back a bit on quality radio in this area from a quarter century ago. While archiving my open reel tape collection, I ran across some programs that I recorded off an exceptional FM station that existed then. The station was WRVH and they lived at 105.5 on the FM dial.
From about 1982-1986, this station provided an enjoyable listening experience for me. During the week, it featured a beautiful music format, but on Sunday evenings from 7:30-8:00pm, it featured a program by audiophiles, for audiophiles. They played direct-to-disc and master tape recordings of classical, Broadway and other music, with the common theme that they were the "cream of the crop" in terms of technical excellence.
The station's owner, Ed Valentine of Wappingers Falls, NY, was a co-owner of the station and one of its founders. He was also a bright engineer who redesigned the audio circuits of the main console mixing board, to improve the audio characteristics. Indeed, WRVH's audio stood out from the other stations in that the top end sounded sweeter, and they didn't process the audio as much as other stations. Processing was practically non-existent, except for peak limiting, on that Sunday evening show, Adventures in Sound, hosted by Anthony Fast and Chip Enright.
WRVH today is but a fond memory, whose license and facilities were bought out by various conglomerate radio entities over the years. The call letters now belong to an FM somewhere in Pennsylvania. But alas, I have some audio clips of the original WRVH for your enjoyment!
Here is the introduction to Adventures in Sound, with Anthony Fast as the host:
Here's the end of a show, with Anthony's closing comments:
I have more recordings from this radio station and as I get to archiving them, their bits and bytes will pass this way. Anyone else who lived in the Hudson Valley at the beginning of the 1980s may remember this station fondly.
I met Ed Valentine shortly after reading an article in the local paper about the launch of WRVH. At the time, I was working on the final stages of a prototype state-of-the-art stereo generator and was making the rounds to all the FM stations in New England, gathering support for my designs. Somewhere along the way, I ended up doing some field concert recording with Ed Valentine and found those excursions to be exhilarating experiences. It was a chance to go to a classical concert free of charge, and it was fun to be working with the radio station, doing something related to my passion. I sure miss those days!
MORE RADIO HISTORY
As promised, here is some more "air check" recordings from WRVH.
You can hear the remarkable acoustics of the specially-built studio, when Anthony's guests, Chip Enright and Bob Biscaborne, speak, further from the microphone. They are discussing the 1959 RCA recording of Camille Saint-saŽns' Organ Symphony, recorded at Symphony Hall, Boston.
Here is Anthony Fast and Chip Enright, discussing some Christmas music recordings, almost exactly 25 years ago to this day:
SPAM, PILLS & "PUMP 'N DUMP"
It's somewhat amusing, just how desperate and industrious these spammers today are. Someone apparently found my e-mail address and as of last week, I started getting about 1-2 spam e-mails a day, where I had received none for the entire year 2006.
As a measure to thwart the spambot harvesters, I have encrypted the e-mail address on this website. In order to find out what it actually is, one has to click on it and bring up a mail reader as if sending me an e-mail and only then is the real address visible.
Well, apparently there are either very advanced spambots this year, or spammers are desperate enough to manually click on links to dig through and find e-mail addresses.
There is just one problem: I have never had an interest in Viagra, stock scams, or 'low interest mortgages'. You see, I work in the financial services industry and I don't need to hire a middleman to buy my stocks or write a loan. And I have a policy: if someone needs to push their crap into my mailbox, or use pop-ups or other annoying means of getting their junk in front of my eyes, I will avoid buying it on principle, even if, say, a spammer was trying to sell me woofers or discounts on electricity. I have always been dumbfounded by the tenacity of spammers, who think that someone is going to respond favorably to their rude and intrusive advertising methods.
As such, if the problem continues, I may route the address through another ISP that has an effective spam filter (too effective sometimes). It's just one of those pet peeves.
In the meantime, it was 64ļF outdoors today and it felt like a day in early April. I took my daughter for bike ride, towing her little buggy all around the neighborhood. Many people were out and about, walking their dogs, some kids riding their bikes and so on. It felt somewhat surreal to be biking in January, when we normally have a deep freeze and a couple of feet of snow on the ground. If this is global warming, then bring it on! I have yet to turn on the big red switch to our oil burner this season. Passive solar has been enough to keep the house warm and comfy. Down here in the studio, I have the windows wide open, otherwise the heat is stifling.
PROGRAMMING THE KURZWEIL SYNTHESIZERI finally got the bug to learn how to use Setups and Zones on the K2600RS. I wanted to split my keyboard into two distinct zones, so I could play a manual part and a pedal part simultaneously. I wanted a Zwel registration and a Bourdon pedal registration both at the same time. I had gotten the bug to play some Christmas selections earlier this afternoon while the wife was out shopping for books at Borders. Seeing as I could make a little noise for a couple of hours without getting hit on the head by a wife who doesn't in the least appreciate my seismic activities, I chose to engorge my appetite on some organ music, using the Post Organ Toolkit samples of the great Bavo Organ and some other organs in Italy and the Netherlands.
I discovered that I could quite intuitively figure out how to setup "setups" --those special quick access buttons that reconfigure the Kurz into a particular configuration for live performance by talented musical performers adept at playing 3-4 instruments at a time and dazzling the audience. It was a matter of choosing a default setup and then changing the sound program to the one I wanted for the right hand, duplicating the zone and then changing the sound program number to the sound I wanted for the pedal (left hand). It was easy and it worked as expected, the first time. I even was able to program some sliders as volume controls for each sound, so I could balance the levels between the melody and the bass. Cool stuff!
UNDERSTANDING THE INNER WORKINGS OF THE ADC SS-525X
For quite a few years, the most limiting component in my sound system has been the ADC SS-525X. It has a very small dynamic range. But I love this unit's selection of frequency bands in the bass range, and the ease of operation. It's the most convenient EQ I've ever used.
A few weeks ago, I was on the quest for better squarewave response from the external processor loop chain. Part of this quest was to maximize dynamic range.of these components. As most of the modules operated from +/-12 VDC rails, this was not an issue. But the ADC is a different animal entirely.
With a digital control and memory storage system (pretty advanced for 1982), the SS-525X can store up to four EQ curves in battery backed memory. This technology was implemented through C2MOS devices that actually pass audio. The Toshiba TC9170AP is employed as a 13-step electronic volume control, both in the individual EQ bands, as well as the master volume control.
Now this is all well and dandy, except for one thing: the maximum supply voltage of VSS to VDD is just 13 volts--that is 6.5 volts per rail! Making matters worse, is that the peak to peak diode clip limiting ahead of these chips is set at 6 volts peak to peak. That's a little over 2 V RMS. That's 12dB less dynamic range than typical op amp systems running on +/- 12V rails, which provide more than 8 V RMS.
Realizing this, I have to concede that there is little I can do to easily improve this component through modifications of a minor nature. So I am contemplating the replacement of it with a Behringer DEQ2496, which would probably sound a heck of a lot better anyway.
HEARING THE TINY NUANCES IN RECORDINGS
As an orchestral recording engineer, I have been doing a lot of critical listening to recordings made by various engineers, with various microphones, preamps and signal chains in the recordings.
This evening, I was listening to a choral performance and noticed some things that were rather glaringly obvious to me. It sounded like inner groove distortion in the right channel only, but it was rather subtle (so subtle that the recording engineer didn't notice it) and it was a kind of crackly, edgy harmonic distortion in the vocals during the louder passages.
This made me very curious, so I listened to the PCM audio file on various DACs, using my MotU 896, and my Turtle Beach Santa Cruz sound cards to compare the sound and ferret out any possible problem with one of the DACs. The problem was audible on the Turtle Beach, though with not as much clarity as the MotU revealed. Then I tried playing just the left channel and then the right, alone. The crackling was clearly in the right channel of the recording. Although, the cymbal rolls had a harsh, gritty sound in both channels, to my ear. Compared to my reference recording, made with my own mics and the MotU 896, it sounded rather harsh and gritty, while my recording sounded like just the orchestra playing, not like a recording at all.
I was able to pinpoint the distortions in the sound file through a careful process of listening and then punching the "M" key to lay down a marker at the precise moment when I heard the distortion. Then I zoomed all the way in on the editor and saw some weird waveforms on the right channel portion of the recording that looked like clipped waves, but with ringing in several places a few milliseconds apart, only in the right channel's waveform. It was subtle, but definitely different from the left channel. And I heard it, while listening on the main speakers.
Such things as this both reaffirm my listening skills as a musician and recording engineer, but they also confirm that the detail and sonic clarity of the sound system on a whole is very excellent. I can hear things on these speakers that it would otherwise require a very good set of headphones to spot, as many speakers just blur the information passing through them far too much. The fact that one recording sounds gritty and harsh and another sounds silky smooth and lifelike, really strikes me sometimes, as it did when comparing two raw PCM sound recordings from two different engineers, all using state-of-the-art sound recording equipment. Every detail, no matter how subtle, is revealed on this system. It's not just a Pig, but a very discriminating Pig.
QSC POWERLIGHT POWER SUPPLY FAILURE AND REPAIR
Quite unexpected, but something I was, frankly concerned might one day happen, one of the power supplies in the upper QSC PL6.0 experienced a chopper MOSFET failure. Mode of failure was short between drain and source terminals. This happened last Saturday night, while the amp was idle. It just tripped the rack breaker without warning. When I powered it back on, I was greeted with a loud BZZZZT! sound and smoke pouring out of the amp, which caused me to instantly switch it off again before extensive damage could occur.
In a system this complex, things are bound to happen, and this is a case where high spike voltages on the primary of a large ferrite transformer can exceed the 500V rating of the IXFN55N50 MOSFETs used to chop the ac power 180,000 times a second to drive the ferrite transformer and rectifiers.
I wasted no time in pulling the amp, bringing it to my shop and disassembling it to locate the problem. Opening Pandora's Box would be an appropriate description. Taking apart this amplifier involved a prodigious number of different kinds of screws, which had to be kept in order so i could figure out where they all go later on, and two floors of electronics inside.
The problem was in the power supply chopper, a shorted MOSFET, which had released a lot of black smoke. First, it was necessary to remove both power amp channel modules, then a partition dividing upper and lower chassis. That revealed two power supply modules. (Each channel has it's own dedicated power supply.)
The supply on the right had sustained the damage. Getting to it meant removing the module, and then removing the heatsink that supported the high speed rectifiers and the MOSFET switchers. And here is what was underneath:
Quite a mess. But I managed to clean it up with multiple acetone and denatured alcohol washes.
I was able to buy a power supply restoration kit from QSC, which contained the most likely to fail components, and it arrived yesterday. I wasted no time setting to work installing the replacement parts. I decided to simply replace everything as provided in the kit, to avoid risking another failure because some related component was overstressed by the shorted MOSFET.
The reassembled module appears here:
This angle shows the diodes that rectify the incoming AC power, making it ready for the chopper to switch it into high frequency RF to drive the transformer.
The solder side, after I installed the replacement components. I washed it several times to get rid of any traces of flux. The voltages here can get very high!
Here is a view from the opposite side, with the heat sink in place.
Finally, I was able to start reassembling the amp.
The power supplies already in, the partition installed, and left amplifier module in place. QSC used 8AWG wire for all the power and speaker leads. Quality throughout.
And... ready to power up!
The experience alleviated my worst concern: that I might be unable to get parts and maintain these amplifiers. I've been maintaining the Haflers and the Phase-Linear for nearly 30 years. This nefangled switching technology looked intimidating. However, the components used are generic enough to be available on the market. QSC also will sell the components. This experience has revealed that I can troubleshoot and repair even such a complicated amplifier and get it running again. And it runs like new once again.
|RETURN TO THE BASS PIG'S LAIR|