Wednesday, November 26, 2008

Focal/JM Labs: Small or Large?

I've been a big fan of Focal/JM Labs for several years. The beryllium and aluminum/magnesium tweeters have such air, and naturalness about them I just can't avoid being drawn to them. In addition their W material really stands out for their transparency and dynamic range which few other drivers have.

There is one thing I've noticed consistenly about bookshelf focals using their W sthough, and a recent Hi-Fi+ review points out. The bookshelves have a bit of a notch in the upper midrange. I think it's related to the small diameter voice coil, but here's a funny thing: The floorstanding speakers, with similar Mid/Woofers don't have this problem. This notch makes them sound a tiny bit nasaly. Good for low volume listening, but at louder volumes, compared directly with their floorstanding siblings, this problem is more noticable.

So, my quick advice: Focal's make awesome speakers, but before you shell out money for the bookshelves + a subwoofer, listen to the floorstanders. I think that for the same money, and footprint they are just better speakers.

Thursday, November 6, 2008

Dave Wilson Owes Me Money

About a year ago I had promised myself I would never buy another issue of The Absolute Sound again. What got me so bothered was their coverage of the Wilson Duette. You can see the cover on the right. Mind you, I can see a reviewer going head over heels for a speaker or component here and there, but the sheer size of the review, including at least 4 full-color/full-page pinup shots of the Duettes was just ridiculous. Hell they devoted an entire page to a picture of the Duette's external crossover!!!! What an insane amount of free press for Wilson. This isn't reviewing, this is blatant advertising. If TAS is going to devote an entire section to advertising for a speaker brand, they should give the magazine away so at least we readers won't feel completely ripped off. In addition to that, it weakens the magazine's brand. Anyone with any sense (and money doesn't equal sense) is going to see through these "reviews" for blatant advertising, and will have serious quesitons about just how objective the reviews of all the products presented in the magazine. Whether TAS gave Wilson this coverage in exchange for past advertising or they got paid directly, or they were promised future advertising, I don't know, but no reasonable person would look at that coverage and conclude there wasn't serious collusion to sell Wilson speaekers in these two issues.

So, I should have learned my lesson, but honestly, lately I've been bored by the reviews at Stereophile, so I decided to stop by the news rack in Harvard square, and pick up TAS and hi-fi+ just to shake things up. I should have seen the Wilson Alexandria Series 2 on the cover, but I was so desperate that I didn't think about it and bought the magazine without opening it first. Damnit! Yet again, an endless set of pages of reviews, gloating, and interviews with Dave Wilson himself. Dave, if you are reading this, you owe me the price of two magazines. TAS, I promise never to buy your magazine again. This time it's for real.

Thursday, October 30, 2008

In Memory of the Snell A series

Today I found a person on Audiogon selling his Snell A2's near me for only $500. I hope he doesn't mind if I steal his picture, if I help him sell these wonderful loudspeakers. I really really wish I could buy them but I have absolutely no place in my house to put them (and my gf tells me she'd kill me).

At $500 with new woofers these speakers are a total steal, even if for only one reason. What the Snell A series speakers have done better than ANY speaker I've ever listened to is that their bass response sounds equally amazing no matter the room you put them in. This particular ability, to perform equally well in a small room or large I've just never heard replicated.

The Snell A's had bass that was awesome, limitless, and not fussy. Any room you put them in, the bass was just, breathtaking. I don't mean that they were scary, or goosebump raising, which they could be, but instead what I mean is that listening to them you felt as if the room, the speakers, the air in your lungs were all somehow coupled together and that the Snells could suck the air right out of your lungs if they tried. And in addition to all that, they felt utterly and completely balanced and real without ever feeling heavy, or offensive, as many large speakers can sound. You can get more bass from something like the large Wilsons, and several of the current super-subsoofers out there today but you can't put most of them into an average sized living room without sounding bad.

If you imagine the best midrange from an electrostatic you ever heard, and then put that quality into a bass driver, these speakers had it, only with ten times the dynamic range. The one negative thing is they were VERY sensitive to amps. Forget driving the bass with tubes or pathetic zero feedback amps. I mean it. You'll need an amp with a high damping factor with at least some local feedback but when you do, wow.

Damn we miss you Peter.

Tuesday, October 14, 2008

The Best PC DAC/Preamp, it's not a Benchmark

There are have been a lot of new companies and names in the audio business over the last 10 years but none of those has succeeded in crossing over from the professional market to the high-end audio market better than Benchmark Media, makers of the much talked about Benchmark DAC and Benchmark DAC1 Pre.

All you have to do is count the number of reviews in consumer mags over the past year and notice how many reviewed products come from professional sound companies. Besides the Grace Designs m902 Headphone Amplifier I can't think of a single other example.

Honestly, I haven't heard either of these products, but I have to explain that based on features alone, neither of these works as well for me as the E-MU 1616m. The reason is simple, I need to multi-task my audio. In other words, I need to mix it, not just listen to 1 thing at a time. I know the high-end is all about listening to 1 thing at a time, but honestly, most people today listen to music from their computer, or while sitting at their computer. When we do, we need to hear multiple things at once. We need the alerts and digital audio from the PC, but we may want to hear an external CD player, or FM radio, and the PC sounds. In other words, we need to be able to listen to multiple things, and if we have taste and can afford it, we want it all to be high quality.

Let me explain further. In my home office, which also happens to be my bedroom, I have my AKG 240 headphones, and a pair of Monitor Audio S6 desktop speakers. The speakers face the bed for watching online movies, or DVD's, but I spend most of my time in here at my desk, with the headphones on listening to a class. Sometimes I want the classical music from the radio on the speakers, and the online class and any computer beeps all coming through the headphones, all at the same time, but not always.

The E-MU 1616m with it's multiple analog and digital inputs, as well as multiple digital and analog outputs does this all for me. It also happens to have multiple very good DACs and a headphone amplifier. There's also interesting features which I have no use for, such as two microphone preamps, with phantom power. If you don't know what that is, then you don't do much live recording. :)

The fact is this is an overkill product for me. If you have a small club, or a large house with multiple zones, this product can work as a very capable multi-zone preamp, letting you set up multiple sources, multiple destinations, and run it all from one place with very high quality, low noise, low distortion results.

Lastly, if I really really wanted to, I could use the 1616m as a very high quality, low jitter PC to S/pdif converter, for about the same price as the USB option on the Benchmark DAC, then run it to any DAC in the world. Plus, with it's digital processing features, I can do serious EQ in the pure digital domain. Also, because the E-MU 1616m uses a proprietary interface, a lot of the ground loop and interface problems inherent in the USB interface just disappear.

There is one downside. The learning curve for the mixer software is steep if you've never used a mixer or digital production software before. There are more buttons, bells and whistles involved. Fortunately once you know how to use the Solo and Mute buttons, as well as the Output assignments, the rest is all gravy.

So, my advice if you are willing to step up to using professional grade tools, and you need the flexibility that I do you simply MUST listen to the E-MU 1616m.

Saturday, March 22, 2008

The Most Common Myths About Home Theater

This post is for the average movie enthusiast who wants a high quality home theater experience, whether he's renting an apartment, or just starting out with home theater, but who isn't sure where to put his money. Those of you who already set aside 1,200 square feet of your home for a separate room with theater seats, an industrial popcorn maker, and automated curtains in a tacky bordello red, as recommended by your installer, who by the way integrated your remote with your garage door opener, can stop reading right now. This is not the post for you.

You've heard about books like "The Secrets of Home Theater". Tells you everything you need to buy and how to hook it up. This article is what NOT to buy, and what you should do instead. This article is also about making spectacular movie experiences accessible to those of passionate, but modest means.

When Dolby Surround first came to the home, decoding VHS HI-FI movies into the front and rear channels, only 3 channels of speakers were used, or sold. Left, Right, and two surround speakers with the same signal. Sometimes with a subwoofer, sometimes not depending on the equipment.

Today we see receivers and equipment regularly having 7.1 channel outputs, and sometimes boasting up to 9.1 or 9.2 channel outputs. While equipment makers try to sell the well heeled the more is better solution, they keep leaving most true enthusiasts to sigh, and say "I can't afford Home Theater" and settling for using the Left and Right channels out of the DVD players, and hooking them up to their stereo, or even their TV speakers thinking to themselves that they will never be able to get "really good" home theater sound.

I'm going to show you how you can invest in "old school" equipment, and get something fantastically better than "really good" that will make you stop envying the pimped out theater rooms, and start enjoying yourself.

The Myth of the Center Channel
The first myth is that you need a center channel. You don't need it. It may not even do anything useful for you. "What, huh? But but but...."

Look, in movie theaters, Dolby Surround (pro-logic to you consumers) was designed so that no matter where you were sitting, looking at a 50' (that's fifty FEET, not inches) screen, your ears would hear the sound coming from the right location. In fact, Dolby Surround was tuned for effects in very large rooms. It was designed to go snap, crackle, pop, across the screen. It does do that, but the only reason for a center channel was the screens were soooo wide, and people often sat on the sides of the theater, that the only way to ensure dialogue stayed localized, and that the recording engineers could transmit the correct effect was with three channels behind the screen (sometimes 5 in mag 70mm) . Unless you have a screen that big, or are sitting too close, having 3 speakers is ridiculous.

Fortunately, most processors, and receivers let you set the center channel to "phantom" mode, redirecting it to the left and right speakers. So, save your money, skip the center channel. You'll need it elsewhere.

The Myth of the Subwoofer

The myth is that your theater will sound better with some oversized subwoofer than without it. Total myth, for most people. Look, here is what usually happens. You live in some apartment, or even a house, with a listening room 12' x 20' and you go looking for a subwoofer.

You go to the store, and they put a glass of water down next to you, then they demonstrate some ultra powerful 3,500 watt, Class A rated sub in a perfectly tuned room which does a Jurassic Park on the water glass next to you. Your hooked. You don't even pay attention to the sound of dialogue, or that every time an actor closes a door in the DVD it sounds like a T-Rex is eating your car, or that Meg Ryan's breath sounds like Darth Vader. The vibes got you. Maybe you can't afford this one for $12,000 with it's delta-sigma amplifier, built in equalizer, and ability to hack into the Death Star like R2D2, but there's it's smaller brother which has a few scuff marks and the dealer can just let it go for a dollar under $2,500.

You get hit home, but because you use your room for things like, I don't know, working, eating, playing Wii and entertaining, there's only one place to put it. And, it's probably the worst sounding place in the room. You turn it on, you find out that it is spectacularly loud for movies, but it colors everything and you can't stand it with music playing. Your girlfriend can't understand the words (like you were ever listening to them) and Conan O'Brien sounds much more Republican now than he used to. Truth is, chances are you bought a sub that's too big for your room, and you aren't going to be able to place it well, and even if you do, it's going to be very hard to integrate it with your speakers. It's like buying a Hummer to do 90 MPH in the narrow streets of Rome. Nice idea, but just not happening. The kid on his scooter will get through with less hassle and look like less of a dork.

So, my advice after living with an M&K sub for over 15 years, and doing all sorts of things to try to get it to get it to work not only with it's own satellites and in several living rooms, dump it. Instead, get some full range front speakers. Nice floor standers that will go no lower than 40 Hz and play loudly without distorting. Another point, is floor standing speakers are usually designed to sound good where people tend to put them, a few inches from the rear wall, and out from the sides. Having a 40 Hz cutoff is really the ideal response for the average TV watcher's living room.

The Myth of the Dipole Surrounds
If you've gone shopping for surround speakers lately you've probably encountered "dipole" surrounds. Surrounds which fire in different directions with different polarity. Basically the idea (was it some geek at THX who thought of this?) was to use tricks of speaker design to make up for you only having 2 rear speakers. What a terrible idea this was, if ever there was one. I've never heard a pair that sounded anywhere near as good as a theater. The reason is that even a small theater would often have 4 surround speakers, which would wrap around you, enveloping you in the rain, the firefight, or even the deep ocean through the oh so thin walls of a wounded submarine.

The Dipole speakers, then Bipolar and related ideas like tripolar speakers (this may be an MK Sound trademark) just were never anything but "odd" sounding. What's worse is that these speakers often cost 2x the cost of their front channel brethren. Instead of buying gadgety surround speakers which are nothing like what is used in motion picture studios or theaters, buy 2 pairs of "normal" (i.e. monopole) speakers for your surrounds. Buy two pairs even if they don't match your fronts or each other. Believe me, the experience with the extra pair of surrounds is so much better, you won't care if they match or not. Don't deny yourself this sheer pleasure. Really. Audio Advisor often has small closeout speakers which are ideal for under $60 a pair.

The Myth of the 7.1 Processor / Amplifier
I remember spending a lot of time reading posts from disgruntled Theta Casanova owners that they wouldn't be able to upgrade their processors from 5.1 to 7.1, and that Theta was not really going to provide an upgrade path for this great little processor. My goodness was there a lot of vitriol in Theta's direction for this decision. A year later Theta was sold to ATI (the amplifier company, not the video card company). I chuckled the entire time, and as soon as they were widely available for under $1,200 I bought one at Audiogon.

For those who are new, the extra 2.0 channels were two discrete (as in separate) rear surround channels. They were first introduced in movie theaters with Dolby Digital EX and DTS ES.
I've gone to theater's and listened to the extra two surround channels. What a load of huey. It's not that they aren't used, it's that engineers, and effects people are still not really sure about how to treat surround speakers. Are they for immersion, effects, or should they provide pinpoint sound location?

Honestly, in almost all movies engineers use the rear speakers for immersion, and then they realise at some point in the movie "oh, right, the producers insisted that I do something special with the surround tracks, I know, let me add wall to wall farts across the back wall....." Sorry, I just can't justify spending extra money, and electricity on having 4 discrete surround channels when I know this is not how the majority of movies are recorded or treated today.

So, if you've been paying attention, you've noticed the math doesn't add up. I've just told you to buy 2 front speakers, and 4 surround speakers, but only 5.1 capable processors/receivers/amplifiers. Huh? Shouldn't that be a 6.1, or 7.1?

Wire the speakers in parallel if your amp is kick-ass. Wire them in series if it has big warning labels like "This amplifier will explode like an al-quaeda dirty bomb if you hook up speakers less than 8 Ohms" By the way, this is how the pro's do it. If you aren't sure, ask for guidance.

The Bottom Line
The bottom line is the ideal starter set up is a 6.0 channel system. With the following equipment:

  • 1 pair of floor standing speakers for L and R
  • No center channel speaker
  • 2 pairs of direct radiating speakers for the two surround channels (4 surround speakers total)
  • 5.1 channel processor or preamp that can redirect the subwoofer output to the L and R as well as handle surrounds which are "small" and fronts that are "large"
  • No subwoofer unless you absolutely can't have large front speakers.
  • If you are buying separate electronics, buy a pair of stereo amplifiers, with the front amp bigger than the rears. This is critical because the front L&R speakers are serving up the acoustic power needed by their normal signals plus the Center, Low Frequency Effects (the discrete 0.1 channel), and the bass for all the surrounds. This also lets you get really nice amplifier for the fronts, especially important if your an audiophile and love good music. In my HT I use 300 Watts for the front, 75 for the rears. The surround amp is a professional grade Yamaha amp with clipping indicators and it's NEVER come near clipping.
  • Consider powered professional/studio speakers for the surrounds. They can be high quality but relatively cheap by comparison, and eliminate the need for yet another amplifier in the rack. In fact if you really want to be iconoclastic, do professional powered speakers all the way around. You'll do it for about 1/8 of what your local high-end dealer would have charged you for the 6 channel amplifier plus speakers. Alternatively, they are making some great powered wireless speakers, this let's you place your surrounds without stringing wires under carpet, in the basement, or through the attic.
  • Timbrally matching the surrounds to your fronts is not nearly as important as sales people claim it is. You really are better off having the 4 surrounds, than having 2 which match your fronts. This timbral matching never existed in theaters, and is a complete fabrication of speaker makers who want you to buy 6 of their top of the line speakers all at once.
Write to me, let me know how this advice has helped you. If you really do love movies, and not counting speakers, I hope this advice has given you a good way to get to movie heaven, while still affording that vacation to Kilimanjaro you were planning.

Going Wirelessly Wired - Home Networking

I'm an odd fellow. I'm odd because I want convenient things like wireless home networking, but I want performance, reliability and simplicity at the same time, and I'm willing to experiment to find the right way to go about it. In other words throw money at it.

So, here is the set up. I rent the top half of an home. The DSL modem, router, and everything else is in the opposite part of the house to where my home office is. Long history behind that, but it was the only way I could keep my significant other from flipping out over reliability issues otherwise. She gets a wired connection to the router, I suffer through with the wireless one. Now, to make a long story very short, I was having serious Internet reliability issues. Web sites could not be found, my DSL connection was going down at least hourly, etc. When you just use the network to surf and do e-mail that's no bid deal, but when your working from home via a VPN connection, and using some fat-bootie e-mail/contact manager tool like Lotus notes, getting bumped off regularly is a big problem. So I put myself and my home network through the grueling ordeal of upgrading.

First, my Netgear router, which yes, was heavily modified by me with the addition of heatsinks and fans, was replaced by a new DLink Wireless N (802.11n) router. No difference in DSL behavior. Contacted Covad who wanted to charge me $100 for a new DSL modem. Apparently they don't understand, for $50 I could have switched to Cable TV's broadband. Finally, after getting them to test the phone line, I did some experimenting and found the problem was that the phone cored was wrapped around too many power cords. Once I straightened up the phone cord, our reliability all miraculously improved.

Next problem was the wireless connection. My PC sits about 45 feet from the wireless router. However, that's 3 open doorways in between. With the first router I had such problems getting a good signal in this room that I used a Linksys G/USB 2.0 adapter that was taped to the back of a bookcase next to the door. That gave me pretty good signal quality, all I needed was 12' of USB cable in between. The new Dlink Wireless-N router worked fine with that adapter, but I was trying to be cool, and bought a new N adapter for the PC, one that would sit inside the case, eliminating the need for the USB cable, and hey, with the 2 antennas, and using Wireless-N I was sure I would get a great signal. Sadly, no. I had exactly the same problems in this location using N as I did with G and B adapters in the past. So, back to the G adapter tied to the bookcase.

No matter what they say about range, or how wireless N should be better, once I introduced the same obstacles into the mix, it all went downhill the same way. I could have bought a N type USB adapter, but I have serious questions about how easily they overheat. In the past I had bought another Netgear product which overheated, a Wireless-G USB adapter. So, I wasn't keen on another one. Which makes the next part of this posting odd.

My end solution was to buy a pair of Netgear WNHDE111 access points/bridges (also available as a 2 unit kit, the WNHDEB111) . What's odd about this is that after having 2 pieces of Netgear products overheating due to cheap ass design I would buy another one. Believe it or not, what convinced me was the case design. It looked like they paid a lot more thought into cooling these units, and that the industrial designers were a completely different group than the one's that designed the original router and USB adapter. As an aside, I think the same people designed the Hauppauge! WinTV-PVR box I use which had the same basic case design and the same overheating issues. I have NO proof of this, just my guess, but if you look at how the cooling can barely make it through the same basic case design, and how they laid out the inputs, outputs, power and main CPU, you'll understand why I would think so.

So, now a little background. Netgear and Dlink are both selling what we can loosely term "media bridges". They are designed to wirelessly enable devices which otherwise may not have a wireless connection, and even if they do have it, provide even better speed than they would have otherwise. Examples of this include devices like Apple TV, SonyPlaystation, and any of the various wired and wireless media players currently out there. These media bridges work to fool your equipment into thinking that it's hooked up to your network via the Ethernet plug out the back. Once hooked up, they are pretty much transparent to the devices. Since the connection to your important devices (PC, XBox, etc.) work on well established networking protocols, Ethernet and TCP/IP, they should work for any Ethernet enabled device you can buy. Basically anything you can hook up via Ethernet, you can now convert to a wireless connection. Their marketing spiel is of course that they are designed to let you stream High Definition (HD) audio and video over your wireless network, which is true but what they do is create a second, high speed wireless network which now runs in parallel to your original one. What they don't tell you is, they really don't care what you hook up to it so long as it talks TCP/IP over ethernet, and what device now doesn't?

Anyway, I purchased one of the Netgear bridges, thinking "Hey, it's a Wireless N device, it should work with my D-Link N router. Well, no such luck. They use the same N protocol but a completely different frequency, 2.7 GHz and 5 GHz. So, in order to make this work, had to have two. Purchased a second one, upgraded the firmware, set up the security configuration on each manually. Powered it all up. And, as if by magic, I have Ethernet-like speeds coming out at both ends. Sweet!

The benefit in my home office is, I can stick one in my bookshelf, in the room's sweet spot, then run 1 Ethernet cable to my desk, where I have an inexpensive DLink 5 port Gigabit switch, and then I can hook up my laptop, my desktop, even an Internet cam. Whatever devices I want to hook up I can, without buying additional wireless adapters. Another major benefit to this all in my mind is not having to install new devices. Half of all the wireless problems I have had have stemmed from getting the drivers installed correctly. Now, my PC and laptop think they are hooked up via the Ethernet cable, and my network's performance has been great ever since.

What's next? Next I'll probably purchase some sort of High-Def media player for the living room and hook it up the same way. I'm waiting for the Netflix/LG settop device to come out, but I'm also thinking about getting a Sony Playstation 3. Even if I never play another game, I think it's the only Blu-Ray player on the market I won't have to upgrade to keep current. Sony has invested a lot of money on the PS3 platform, and it's consistently been the first Blu-Ray player to meet each new specification.

Also, another aside, I think that if this keeps up the other Blu-Ray licensees will figure out they've been had. Sony doesn't want to license Blu-Ray, they want to dominate it. Their continuous evolution of the Blu-Ray player standard will mean that only PS3 owners will be able to keep their players more than a few months before they are obsolete.

Thursday, March 20, 2008

Resmed S8 Version 2

After trying out my original filter mods I found myself working harder to breathe than I did before. Under load, the filter media surface area was just too small to avoid straining the motor, and my lungs. So, I did what any other hacker would do. I multiplied the surface area by 8, and tried again. Problem solved, but, instead of a square patch, I ended up with this 6" white felt tube sticking out of the corner, and the whole thing looks rather obscene. Fortunately I'm now putting the S8 in my night stand, with plenty of ventilation, and you can't see it. What would mom think?

Monday, February 25, 2008

Modding the Resmed S8 CPAP Machine

Finally, after several overnight studies in two different sleep labs, my doctors have prescribed me a C-PAP machine. Basically, it's a bed snorkel. The mask provides pressurized air to your airways while you sleep, reducing the number of times your airways collapse and try to choke you. Now, if you just died in the middle of the night, this wouldn't be so bad. I mean, it's just death, but what actually happens is that your brain, for some odd reason, realizes you are choking, and wakes you up, so you semi-consciously start breathing again. If this happens frequently enough, instead of dying peacefully in your sleep, you wake up feeling like sleeping is very hard work. In other words, barely rested.

So, enter the CPAP machine. Keep your airways full of air, and you don't wake up before choking to death. In fact, you don't choke much at all. No dying, no waking. Just nice even sleep.

The one major problem I see with almost all CPAP machines being sold today, and the Resmed in particular, is that they really are not designed to be all that quiet, but more importantly for allergy sufferers, the filtration really stinks. They fit this tiny bit of polyester fluff in at the entrance of the machine, which basically won't filter out anything but big tufts of cat hair. Everything else in your room, you will breathe, at high pressure. Not a great way to spend the night. They do make in-line filters, but these have a chance of tricking the pressure meters into thinkign your air pressure is higher than it is. It really would have been oh so very easy for Resmed to put in a HEPA filter on the inake.

I should have taken a picture of the intake before I cleaned it for you to see. It was really dirty. Also, instead of providing you with a place to put an intake filter, or at least a place to attach one to, Remsed instead has an opening that makes it almost impossible to attach anything useful to the intake, like for instance, a muffler, or a HEPA filter. Very frustrating. And on top of everything else, my MD prescribed this particular model. Mind you, it works very well, and I understand it's very reliable, and small and portable and the integrated humidifier is pretty sweet, but they are like morticians. They really don't want you shopping around for the best casket, they want you to buy the one they tell you to buy.

So, what is a hacker like me to do? Well, it turns out that in the woodworking and industrial worlds they make these huge dust collection/air cleaning systems. Often a professional mill work or woodworking shop, and sometimes advanced hobbyists, will have large dust collectors with 4-6" ducts running around their shop, sucking up all the wood chips and keeping the shop clean and the air breathable as the craftspeople work. The air gets expelled in a variety of ways, including through these long polyester felt tubes, at the bottom of which is usually a trash bin of some sort. Anyway, the point is, the polyester felt used in these bags normally filters materials down to 1 micron, and after getting nice and packed with wood dust, they get even better, filtering down to 0.3 microns, or about. Not quite HEPA standards (0.3 microns all the time) but MUCH better than what Resmed provides.

So, my solution? Purchase a bag from Oneida Air , cut out just enough filter media to cover the intake, duct tape it in place, and voila, suddenly I can breathe easier at night. :) I've tried it at least one night, and it worked fine, with no apparent change in performance of the CPAP machine. If I was really clever, what I would do is measure the amperage while it runs to see if there's a difference in strain on the air pump with and without the felt, bur right now, my work and school are taking up too much of my time. If I had more time I would have created a felt "pocket" so that I could increase the surface area of the filter. In the next incarnation this is probably what I will do, though honestly it's hard to tell it needs it.

Tuesday, February 5, 2008

The Things We Do for Love

When you are looking at a mid-80s piece of gear the first thing you have to look at are the power supply filter caps, like the one's I pulled out of the Yammie yesterday.

They are in pretty good shape, and will probably last a while longer, but let's face it, these caps are 20 years old. They aren't fresh anymore, and if they go, you risk loosing everything else in the component. As it turns out, the Yamaha, Sumo Polaris and other amplifiers from this era shared the same filter caps.

Today, unfortunately, these caps are extremely difficult to come by. What makes them so special is the 80V rating. You can buy 15,000uF 100V caps right off the shelf, without any problem however they tend to be 120mm long. About 30 mm longer than the originals. The only manufacturer I could find that still makes them is Nippon Chemi-Con, so as a result of this it looks like I'm going to be forced to purchase a small lot of them, and then try to resell any I don't use. Not exactly how I planned on making extra cash this year.

However, if you find yourself in the same boat as I am, and need these caps, send me a yell, I'll be happy to sell you what I don't use. :)

Saturday, February 2, 2008

The Yamaha P2100 Amplifier

The P2100 was introduced in 1977, about 10 years before the P2075, and it's interesting to look at the differences that there are in the circuits of these two amplifiers.

The 2075 is about a 50 W/Channel stereo amplifier. It includes fully balanced inputs thanks to a pair of JRC op-amps, as well as monolithic chip driver and amplifier stages. While you may sniff at the chip amp design, they did a lot of things better in the 2075 than in the 2100. The inputs are truly balanced, many of the audio signal resistors are metal film, copious amounts of bypass capacitors are used throughout the design, and the output stage is heavily protected. Also, the 2075 relies on a lot of ceramic capacitors used as bypass caps.

On the other hand the P2100, while it has a completely discrete audio path, has a single ended input, and almost no bypass capacitors to speak of. The power supply rails go through three different boards with no local capacitor storage at all. While the resistors are mostly cheap carbon composite the capacitors are all polystyrene or tantalum. There's also almost no output protection to speak of. A couple of thermal cut off switches attached to the heat sinks are all you get.

Both amps use several cemented resistors especially near the output stages.

So, the question is what to do, what to do. First, the 15,000uF/86V screw terminal storage caps in the power supply are completely unavailable today. I'm going to have to find suitable substitutes. This probably means designing a new power supply board. If I'm going to do that, I might as well throw in some discrete, zero-recovery diodes, and large value bypass caps.

Next, the cement and carbon comp. resistors will have to go. So will every single electrolytic in the unit.

Last, if I get really ambitious, I'll design a new input driver board to turn the input into a truly balanced design. I'll probably use the design from the 2075 to stay true to the Yamaha spirit.

More when I start ordering parts. :)