DSD comparison to PCM.

[LynnOlson]

The Karna amplifier power supplies are absurdly overdesigned for a nominal 20 to 30 watt amplifier. The input and driver have completely separated B+ supplies from the output section; by completely isolated I mean separate plate transformers and separate damper-diode rectifier bridges. The only thing the two sections share is a power cord. The damper diodes, in additional to having far quieter switching than solid-state rectifiers (including HEXFREDs), can carry peak currents of 1 amp, which isn't bad at 500 volts.

The input section has shunt regulation powered by current sources with a measured isolation of 120 dB (the Gary Pimm cascoded MOSFET current sources). Same for the driver section, which gives very high isolation between sections.

The output tubes can carry momentary peaks of 300 to 400 mA - 300B's can turn on surprisingly hard, and the amplifier slides between Class A1 and Class A2/AB2 with no visible transition around 15~20 watts. The Class A PP driver section can actually drive the grids of the 300B's 30 volts positive (Class A2) with no visible or audible transition, something I would not have thought possible for a DHT like the 300B.

I've measured full-power output at 500 kHz with no visible distortion on the scope, a test that would demolish many solid-state amplifiers. The slew rate on the grids of the 300Bs was some crazy number well in excess of 1000V/uSec. This was a spooky test; I knew all of the tubes were driving loads that were almost purely reactive at that frequency, yet they handled it pretty well. That's the magic of Class A PP; nearly complete immunity to any load, which is not true of Class AB or SET operation.

The after-RMAF visitors are usually shocked by the sound of the Karna amplifier; there's the delicacy and tonal depth of 45's and 300B's combined with the slam-bang dynamics of a Crown Macro Reference. There's none of the usual mush of most vacuum-tube amps; it's insanely fast compared to most amps, including solid-state. If you can imagine Stax headphone transparency with Klipschorn dynamics and 45/300B tone color that about describes it.

What's odd is that recordings, even "bad" recordings, sound great, but boy, it doesn't forgive poor sources at all. Changes to the source are usually audible before I walk back to the sofa - everything sounds different, there are no sound-alike DACs with this amplifier.

What gives me pause is the new speakers will be far more transparent - and dynamic - than the Ariels. The system will gain nearly 10 dB of headroom and loudspeaker distortion IM distortion will drop several-fold. This will almost certainly result in more demands on the source - maybe by then my friend's DAC project will be done.

 

[LynnOlson]

Sorry about the braggy tone of the previous post, but I had to describe what the Karna sounds like. The post-RMAF visitors are usually speechless, and they all described it as "best sound at the RMAF" - which I had to concur.

When I talk about tube DACs, most folks think of a tubey-sounding mush that conceals the gruesome sound of PCM by spreading a layer of syrup over everything. A good example of this would a system with a 12AX7-based phono and linestage and a solid-state power amp - which to me is the worst of all worlds, tube mush and Class AB solid-state grit.

This ain't like that. At all. Once the miserable, low-speed I/V converter is removed, PCM sounds a *lot* different. Really, it does.

One of the kinky tests I tried was comparing the Resonessence Invicta with 64fs DSD, and the Monarchy N24 playing 88.2/24 from Pure Music, with PM converting a 128fs DSD file into 88.2/24 PCM. Same music file, just different DSD source resolutions. You'd expect the DSD -> PCM conversion to sound way worse, wouldn't you? I certainly did.

Well, I was wrong. Both sounded equally good, to my surprise. The Monarchy was more diffuse, but also more spacious (sound filled the room). The Invicta was more focussed, coming mostly from between the speakers, a more "concentrated" sound if you will. This was with symphonic material, by the way, so a more spacious sound was a plus. Tonally, both were equally good - vivid, dynamic, with beautiful tone colors and dynamic shadings. The image distribution was quite different, in a way that's hard to describe.

On my system, PCM and DSD were a draw, even allowing for the losses of the Pure Music conversion process from 128fs DSD to 88.2/24 PCM. Karna thought little of it - she preferred the Monarchy with the more spacious and open sound. Me, I thought it was a draw - the more in-your-face sound of the straight-DSD approach would appeal to a lot of audiophiles.

 

[bbb]

Spot on Lynn. We also build our dac like how we build our amps. Past the digital section, just treat the analog signal like any low level signal. Give it a good tube output transformer coupled stage and very robust choke filtered, tube rectified & regulated power supplies. The downside is usually the dac ends up weighing like most people's power amps and takes a while to get going . We have recently done up a really sweet sounding type 50 DHT pre (much better than type 10 and 300b IOE) and are thinking of using that in place of our usual CCA output stage in the DAC. Any comments/insights on this?

 

[LynnOlson]

If you can conquer the microphonics of the 50, which won't be trivial at the signal levels involved - or maybe you were thinking of using it as the output/line driver stage? Mostly a flavor choice in that location. I'm kind of old-school - I'd think of a plain old 6SN7 as the line-driver.

The really critical interface is between the current output of the converter and the input node of the first analog stage. Low-passing of some kind is necessary, and the actual conversion element must have low distortion from the audio band to the highest frequency of interest, which is 10 MHz or higher.

 

[rbbert]

Sorry to go off-topic for a moment, but what were the other components in the Karna room at RAMF?

 

[MarinJim]

Sorry about the braggy tone of the previous post, but I had to describe what the Karna sounds like. The post-RMAF visitors are usually speechless, and they all described it as "best sound at the RMAF" - which I had to concur.

When I talk about tube DACs, most folks think of a tubey-sounding mush that conceals the gruesome sound of PCM by spreading a layer of syrup over everything. A good example of this would a system with a 12AX7-based phono and linestage and a solid-state power amp - which to me is the worst of all worlds, tube mush and Class AB solid-state grit.

This ain't like that. At all. Once the miserable, low-speed I/V converter is removed, PCM sounds a *lot* different. Really, it does.

One of the kinky tests I tried was comparing the Resonessence Invicta with 64fs DSD, and the Monarchy N24 playing 88.2/24 from Pure Music, with PM converting a 128fs DSD file into 88.2/24 PCM. Same music file, just different DSD source resolutions. You'd expect the DSD -> PCM conversion to sound way worse, wouldn't you? I certainly did.

Well, I was wrong. Both sounded equally good, to my surprise. The Monarchy was more diffuse, but also more spacious (sound filled the room). The Invicta was more focussed, coming mostly from between the speakers, a more "concentrated" sound if you will. This was with symphonic material, by the way, so a more spacious sound was a plus. Tonally, both were equally good - vivid, dynamic, with beautiful tone colors and dynamic shadings. The image distribution was quite different, in a way that's hard to describe.

On my system, PCM and DSD were a draw, even allowing for the losses of the Pure Music conversion process from 128fs DSD to 88.2/24 PCM. Karna thought little of it - she preferred the Monarchy with the more spacious and open sound. Me, I thought it was a draw - the more in-your-face sound of the straight-DSD approach would appeal to a lot of audiophiles.

I am sorry, but I know what I like to listen to (in fact I used to own a pair of Heil AMT-1s), and frankly, I am reading a lot of personal biased BS. Tube amps lack dynamics, speed and transparency. But hey, to each his own. I don't write for a publication because listening is a personal endeavor. What I mean, is here on this forum, we are allowed to express our preferences, but not to disparage other preferences. This comes from a Masataka Tsuda preamp 12AU7 devotee with SS amps.

 

[LL21]

Well, one difference, discussed in more detail in Part Two, between PCM and DSD is a very different ultrasonic spectra. DSD is noiselike (but not quite noise in the analog sense), while PCM is a collection of narrow spectral spikes that are tightly correlated with the audio signal.

The reason I mention this is that PCM seems to greatly suffer in DACs that use opamps or discrete-transistor circuits with high feedback ratios combined with low slew rates. By "low" I mean a slew rate appreciably slower than 1000V/uSec. I've measured comb spectra coming out of a Burr-Brown PCM-63 that was flat to 20 MHz, and finally disappeared in the noise at 50 MHz. To keep up with that kind of rate-of-change requires a slew rate 1000V/uSec, or more.

This is why I favor passive I/V conversion in parallel with a lowpass capacitor. It is nearly impossible to build an analog stage that has low distortion in the 1~20 MHz region; RF circuits avoid this necessity by extensive use of filtering, as in superheterodyne conversion and amplification.

Passive I/V conversion distortion is set by the distortion of the resistor, which if well-chosen, is less than -150 dB over a wide bandwidth extending into the GHz region. A 70 kHz 1st-order lowpass (parallel cap) shunts RF energy away from the following analog section, which still needs to be reasonably fast (5532/5534 and 797 need not apply).

The 6DJ8, although not my favorite audio tube (more 3rd-harmonic than I'd like), has exceptionally good RF performance into the hundred-MHz range (the 6DJ8 was originally designed as a RF preamp tube for color-TV tuners). Although the 2nd and 3rd-harmonic are probably in the 0.1% range for 2V rms out, that can be lowered (if desired) by choke or current-source plate loading. It has plenty of headroom with the plate at 100~120V; the available voltage swing is about 60V.

The most important aspect of the I/V conversion stage is avoidance of RF crossmodulation from ultrasonic components from the converter. It's basically akin to designing a MC preamp that has to operate in close proximity to a flourescent light. The primary requirement is noise resistance. Compared to that, everything else is secondary; it is more important to reduce gross distortion over the working bandwidth of the I/V converter than chase the last decimal point in the audio band.

The second stage, if necessary, can be perfectly conventional, since by then the signal has been effectively lowpassed to the 70 kHz or lower range.

Returning to the original point, ladder/R-2R DACs with correctly designed I/V conversion sound remarkably "analog" and DSD-like. On the other hand, if you simply follow the manufacturer's app-note and use a 797 or 5532 active I/V converter followed by a 797 or 5532 Sallen & Key active lowpass filter, all of the grit-n-grain of PCM returns.

Protip: Any time you hear flattening of the soundstage, or outright grittiness, do a thorough analysis for any possible RFI intrusion into the analog circuits. Solid-state audio-analog circuits, in particular, do not behave well in the RF region, so content above 100 kHz needs to be well-filtered before it touches the first transistor base or FET gate.

The Karna amplifier is very overdesigned from this viewpoint; the input transformer is a 2nd-order lowpass around 50 kHz, the secondary is electrostatically screened to filter RFI, the gryounds of the amplifier are electrically isolated from the DAC (no ground loops are possible), and the input tubes retain their linearity in the MHz region. In addition, there's no output-to-input feedback loop, so RFI picked up by the speaker cables (which are good antennas for AM radio) does not crossmodulate with audio in the input stage.

Thanks for joining Lynn...very much enjoy reading your posts...and in a thread I have already particularly enjoyed.

 

[BudP]

Tube amps lack dynamics, speed and transparency.

True of most any tube amp other than the Karna. Lynn is actually just reporting what you would also hear. The things are startling, in a very good way. No disparagement of SS implied here either, just equivalent but different.

Bud

 

[mep]

I have owned tube amps for many years and never found them to lack dynamics, speed, or transparency. Where I find tube amps lacking is the bottom octave. They simply can't do bass like a great SS amp can.

 

[BudP]

Just means that the OPT's were designed like power transformers, rather than the meta stable nature required of audio outputs. I only know of 5 designers in the world who know how to design audio transformers. Earlier, in the 40's and 50's, there were quite a number, but SS killed the knowledge base. The problem is that the core, which is actually passing power at low frequencies, is hanging at saturation peak until the voltage swing goes opposite in phase. This sounds slow and muddy. There are solutions, Lynn's Karna has one of the solutions in it's audio section. He could have chosen from the offerings of any of the 5 current true professionals and had an amplifier that does not suffer any of the slings and arrows that almost all of the rest suffer from.

I would direct your attention to the Red Rose tube amp models and the AudioPrism models of a few years prior to Red Rose taking them over. These amps do not suffer the typical tube amp problems either.

For the rest, I completely agree with your criticisms, all of them.

Bud

 

[MarinJim]

Just means that the OPT's were designed like power transformers, rather than the meta stable nature required of audio outputs. I only know of 5 designers in the world who know how to design audio transformers. Earlier, in the 40's and 50's, there were quite a number, but SS killed the knowledge base. The problem is that the core, which is actually passing power at low frequencies, is hanging at saturation peak until the voltage swing goes opposite in phase. This sounds slow and muddy. There are solutions, Lynn's Karna has one of the solutions in it's audio section. He could have chosen from the offerings of any of the 5 current true professionals and had an amplifier that does not suffer any of the slings and arrows that almost all of the rest suffer from.

I would direct your attention to the Red Rose tube amp models and the AudioPrism models of a few years prior to Red Rose taking them over. These amps do not suffer the typical tube amp problems either.

For the rest, I completely agree with your criticisms, all of them.

Bud

OK, who in the good "ole USA" wants to buy and report?

 

[BudP]

Well, as of a few minutes ago I would have to add another tube amp to my very short list. Gary Koh loaned me a pair of his personal designs for unobtainium mono blocks, from out of his storied and smokey history.

Incidentally Gary, placing the notch filter after the speaker and placing a Ground Control in between appears to be the answer. For the rest of you, I have been trying to keep a notch filter applied to my EnABL'd Lowther's from absolutely killing all life from those drivers. So, two delights in one evening... no chocolate required either.

Bud

 

[LynnOlson]

I can only report my own subjective impressions, along with the measurements I've made along the way. I certainly don't expect most audiophiles to agree with me, since my tastes are quite different from Stereophile, Absolute Sound, Six Moons, Computer Audiophile, and most other reviewers. I also think - and I expect most folks will disagree with me here - that most commercially available high-end equipment has numerous design flaws and outright errors, some of which affect reliability. I make plenty of mistakes too ... but so does every high-end designer I've met. Sadly, there are no Einsteins among us, or even Edisons, much less a Major Armstrong, H.F. Olson, A.D. Blumlein, or D.E.L. Shorter. Audio has gone a long way downhill since those days.

Much of what I do is a kind of archeology, rescuing interesting ideas before they are forgotten. I collaborate with folks like Gary Pimm, Matt Kamna, Bud Purvine, John Atwood, Bjorn Kolbrek, and Martin Seddon because I couldn't possible work at the edge of audio otherwise.

I used to listen to solid-state until about 1992, when I got pulled into the orbit of the Oregon Triode Society, which led to designing the Ariel, etc. etc. I would be the first to agree that most Class AB PP-pentode-with-feedback amps are pretty dull-sounding, which I why I don't think the "Golden Age" amps from the Fifties are all that great. And the modern high-end remakes are worse, not better, adding a nasty layer of grain and listening fatigue to a mushy-sounding architecture. Adding solid-state regulation to a 1950's amplifier does NOT fix what's wrong with the circuit.

The SET revival in the early Nineties went off the rails by solely focussing on the least-good aspect of direct-heated-triodes ... single-ended operation. The dull, clouded sound of PP tube amplifiers is not the sound of PP itself, but poor phase splitting architecture, with the split-load inverter being the worst (but also the most common, unfortunately). There are better inverters out there, with the Mullard a significant step upward, and the much-maligned paraphase inverter a real surprise. But the highest quality is with interstage transformers, which are passive devices and have the charm of greatly improved current drive into the somewhat nonlinear and reactive grids of the power tubes. Both solid-state and vacuum-tube amplifiers are critically sensitive to the current-drive linearity of the driver stage; this innocent-looking stage actually dominates the sound not just of the amplifier, but the entire hifi system.

There are critical nodes in every hifi system: in a phonograph-based system, the weak points are tip-mass resonances in the phono cartridge, which can interact with the first stage of the phone preamp. The high Q of the tip-mass resonance can nudge the first stage into slewing, and a long recovery time from slew events. The first stage has a very difficult job because it has three conflicting requirements: (1) low noise (2) freedom from overload, slewing, and fast settling when these events occur (3) ability to drive the highly reactive RIAA network that loads the first stage. Most designers focus only on noise while ignoring (2) and (3), which has a very obvious effect on the sound of LP replay.

Power amps almost always have marginal driver stages, with not enough current to linearly drive the substantial capacitances of the power devices. Class AB operation makes this quite a bit worse, with charge-storage effects happening when one transistor needs to be turned on again. Unfortunately, despite claims from solid-state vendors, the transition from Class A to Class AB happens around 1 watt, not a great location.

The critical node with DACs is the interface between the converter and the first analog stage. Unfortunately, very few audio designers have access to a instrument-grade 100 MHz RF spectrum analyzer, so they can't see all the amazing things coming out of the converter - and no, a scope is NOT the right tool for investigating and removing RFI.

Case in point: the analog stage of the much-ballyhooed Sony SACD-1, the flagship one-box SACD player of the late Nineties. I'm not 100% sure, but I've heard from several sources the architecture was as follows:

Dual converters with balanced outputs -> two 5534 opamp-based I/V converters -> 100uF electrolytic coupling caps -> 5532 balanced-to-single-ended converter -> 100uF electrolytic cap -> 5532 active lowpass filter -> 100uF electrolytic cap -> 5532 single-ended-to-balanced converter -> XLR output.

For those not up to speed on opamps, the 5532 dates back to 1979, and was the first (I'm not joking) opamp designed for audio (previous opamps like the 741 and 301 were far too slow and have too much HF distortion). It was pretty good for 1979, but in 1995? Come on.

Slew rate is 13V/uSec, many orders of magnitude too slow for raw digital outputs. The 5532/5534 also has quite a lot of input bias current, which leads to DC offsets. The stupid way to remove the DC offset is with a low-fi electrolytic, the smarter way is to balance the DC source impedance of the inverting and non-inverting inputs, and if you're really tricky, a separate DC servo circuit. But a failure in the DC servo can destroy a direct-coupled transistor power amplifier, so be careful.

And this is a $5000 player, no discounts, folks. I wouldn't use an analog stage like that in a car stereo, much less a flagship product aimed at audiophiles. The total cost of the analog stage, considering the low, low price of 5532/5534's (which is a dirt-cheap "jellybean" part today) and generic Japanese electrolytic caps, is probably $5 to $10, tops. The case, though, was a work of art, and probably cost more than $200. Priorities, you know.

What's really hilarious is most of the "modders" left the circuit alone, and just swapped the generic electrolytics for Black Gates, and charged prices upwards of a $1000 for the mods.

 

[MarinJim]

I love what Modwright has done to my Oppo 105. And adding some PSVANE and Mullard tubes is just icing on the cake. It is all about preferences, folks.

 

[manisandher]

Case in point: the analog stage of the much-ballyhooed Sony SACD-1, the flagship one-box SACD player of the late Nineties... What's really hilarious is most of the "modders" left the circuit alone, and just swapped the generic electrolytics for Black Gates, and charged prices upwards of a $1000 for the mods.

Haha, I bought an SCD-1 pretty much as soon as it was released... and was totally underwhelmed by its performance both from CDs and SACDs. So much so that I sent it to be modded. The mods cost around $2500 and made, well, very little difference to the sound. It was still trounced by my Rotel RHCD-10 CD player in terms of musical involvement and enjoyment.

And like you, I stopped buying from the 'big boys' a while ago. All of my components are made by individuals with a total passion for what they do. Bert Doppenberg for the speakers, Peter Stordiau for the software player & DAC and Gerd Sauermann for the amps. As well as getting a better sound using these guys, it's a total pleasure doing 'business' with them. Their integrity and passion for what they do is so refreshing in this day and age.

Mani.

 

[MarinJim]

Haha, I bought an SCD-1 pretty much as soon as it was released... and was totally underwhelmed by its performance both from CDs and SACDs. So much so that I sent it to be modded. The mods cost around $2500 and made, well, very little difference to the sound. It was still trounced by my Rotel RHCD-10 CD player in terms of musical involvement and enjoyment.

And like you, I stopped buying from the 'big boys' a while ago. All of my components are made by individuals with a total passion for what they do. Bert Doppenberg for the speakers, Peter Stordiau for the software player & DAC and Gerd Sauermann for the amps. As well as getting a better sound using these guys, it's a total pleasure doing 'business' with them. Their integrity and passion for what they do is so refreshing in this day and age.

Mani.

Do you still have your Weiss?

 

[rbbert]

I can only report my own subjective impressions, along with the measurements I've made along the way. I certainly don't expect most audiophiles to agree with me, since my tastes are quite different from Stereophile, Absolute Sound, Six Moons, Computer Audiophile, and most other reviewers....

I don't have the electronics training or expertise to contribute to the present direction of this topic, but I had to chime in here

Bob (Northstar) undoubtedly frequents more audio sites and magazines than I do, but even I have noticed that there is no such thing as "most other reviewers". Even those 4 review sites you mention (not including the multitude of others easily available) present a dizzying array of audio tastes, preferences, opinions, etc. I doubt that anything close to a majority of reviewers (perhaps excluding Computer Audiophile, I've rarely viewed that site) prefer the SS A/B amps and low-efficiency speakers you say they do; I even doubt most "audiophiles" do.

 

[LynnOlson]

Well, I can only speak of the reviewers I've met personally; very hard to tell what a reviewer's system sounds like unless you visit their home. That applies to all of my subjective comments, too. Maybe the solid-state guys have been a bad influence; once I switched to triodes in the early Nineties, I didn't look back.

I've gotten a request from the mods to say whether I'm in the industry or not. Well, in terms of income or having products for sale, I'm not in the industry at present. I'm retired, and live off retirement income and various investments. On the other hand, if I ever find an appropriate business partner with manufacturing experience, I'd really like to get back into it and manufacture the new loudspeaker and commercial version of the Karna amplifier.

In terms of experience, let's see ... 1972~75, invention, patenting, and prototype of Shadow Vector Quadraphonic Decoder with Audionics of Oregon. Worked on the assembly line building PZ-3 amplifiers to pay the bills while the SV was developed. In 1975, went on a trip to England to meet the BBC Research Lab and Laurie Fincham at KEF, while pitching the SV system to EMI Labs. After returning, the SV project was shut down, and was re-assigned to loudspeaker development after the previous designer high-tailed it out of town with no forwarding address. The 2-hour conversation with Laurie came in handy for the next several years, and resulted in the TLM-200, M32, TL50, T52, and other loudspeakers. Sold a minor invention to Wesley Ruggles which indirectly ended up as a portion of Dolby Surround cinema decoders.

Left in 1979 for greener pastures at Tektronix as a tech writer, and worked in the Spectrum Analyzer business group from 1980 to 1985. Invented and patented a 3-dimensional inertial mouse and scope/spectrum analyzer digital display with variable persistence (electronic phosphor). Took care of interfacing the writer groups with the DEC/Unix mainsframes and was using the Arpanet to communicate with my sister in Berkeley in 1985. Laid off in the 2nd big wave of Tek layoffs in 1988 and went to work at The Computer Store (actual name) in Portland, Oregon as a system engineer, architecting network systems for school districts and PDX businesses. Enjoyed my stay there - the most fun job I'd had to date - and met up with the Oregon Triode Society folks after being out of audio for ten years. (I needed a long vacation after the experience at Audionics, and made a resolution to never work for anyone else in audio ever again. Collaboration, yes, but never as a direct report.)

Started writing for Positive Feedback magazine in 1992 or so, with a long article about building the Ariel loudspeaker. That eventually became one of the early Web pages back in 1995, which is why the Nutshell site looks so old-fashioned. It's hand-coded and dates from the dawn of the Web. Wrote the first American review of the Ongaku amplifier in 1993 for PF magazine, along with the first review of the Reichert Silver 300B. That got me started in amplifier design, something pretty new for me. That was at the height of the SET tidal wave, and all of the East Coast Triode Mafia thought I was nuts for designing a PP, all-transformer-coupled amplifier. Harvey Rosenberg, thank goodness, encourage me, along with the Direct Heating folks in Japan. I was quite surprised the social director lived in the old village where I grew up, Shukugawa, between Osaka and Kobe.

Wrote several articles for for Ed Dell, briefly edited one of Ed's trade magazine, and was recruited by John Atwood, co-founder of Vacuum Tube Valley to replace him as Tech Editor for VTV. Lots of fun working for Charlie Kittleson, editor of VTV, but Ed, David Robinson, and Joe Roberts (Sound Practices) are lots of fun and a hoot to work with. I really miss Harvey and Charlie ... they gave the industry a lot of sparkle and entertainment. Harvey's ridiculous clown persona ... which was on full freak-flag display at the Las Vegas CES ... hid a very serious philosophical approach to the art of audio design. He also had damn good taste, as well a being a terrific and very funny writer ... something almost impossible in audio writing. I consider him on of my mentors, along with the much-missed Bob Sickler.

My sweetie, Karna, worked for the US Army Corps of Engineers as a mainframe programmer, and taught herself Web programming back in the Netscape 1.0 days. She taught me HTML, and I converted all of Ariel project into that format, thus, the first parts of what became Aloha Audio, then Nutshell High Fidelity. I thought I was saving time not having to answer requests from people all over the world to mail them copies of the Ariel project ... well, HTML has a way of not saving time after all, but it was fun being part of the early Web.

Aloha Audio (in collaboration with the late Hiroshi Ito) was the North American distributor for DACT volume controls for a couple of years, but that dissolved after Aloha Audio was wound up. During this time, Per Lundahl approached me about being the North American distributor for Lundahl Transformers, but I was enjoying my new retirement too much to take him up on it. I pointed him to Kevin Carter, formerly of VAC, as a good alternative, and the rest is history. Kevin's a good guy and I'm glad his business is doing well.

So to answer the moderators, I've been in and out of audio since 1972, but don't have anything for sale these days. I pay for the upkeep of the Nutshell High Fidelity website, but it doesn't actually bring in any money. Maybe I should follow my own advice and put in a tip jar.

P.S. First big snow day here in Colorado. Already spent an hour using the snow-thrower on the driveway and sidewalks, but it's still coming down at a good clip. Another session in the afternoon at this rate.

 

[steve williams]

Hi Lynn and thanks for the info. Again, a big welcome

 

[microstrip]

Lynn,

Great to read you at WBF. About fifteen years ago I helped a dutch friend staying in Portugal building a pair of Ariel speakers. It was lot of fun (and many beers...). Besides I always love to read someone who quotes Ralph Morrison's "Grounding and Shielding Techniques in Instrumentation" when writing about audio!