Sunday, December 12, 2010

Birth of an Amplifier

Here's a short description of the construction of an Elliott Studio Arts 66-100 power amplifier. This is a basic model, unbalanced and without a triode/UL switch (which switches the output stage between modes). The first step in construction is to assemble the chassis and related components. Shown below is the top panel to which the circuit board is installed after it is seperatly constructed, as well as the power and output transformers. A horizontal brace can be seen, situated below the heavy transformers to provide additional strength, and a lightweight vibration damping material is applied to damp rining. The tubes, bias pots and switch protrude through the holes and the bias meter occupies the rectangluar opening in the center.

Next you can see the bottom of the chassis with the seperate front and rear sub-panels installed. Seperate sub panels facilitate changing the configuration without having to re tool the entire enclosure. In example, the rear sub panel for the balanced version of the amplifier is different but is the only part that needs to be changed. This makes the product flexible and economical to build in small quantaties. Also seen is the cooling fan, input and output jacks, power inlet / filter and fuses. Up front you see the main filter caps, smoothing choke and power switch. In the center is the terminal block where all the power wiring will land when the top panel and circuit board are installed.

The next picture shows the circuit board with the tube sockets, terminal strips, bias meter & pots, and ground wiring installed. This "circuit board" is actually 16ga. steel which provides a rigid backbone for the circuit to live and an active ground-plane with good RFI rejection. All the components are riveted directly to the circuit board and will not vibrate loose over time. All the wiring is point to point just like the old days. This method of wiring is time and labor intensive but is more robust, superior for the high-heat and high-voltage environment of tube amplifiers, and sounds better. I have repaired some contemporary tube amps that use printed circuit boards and have seen catstophic failure of the board itself where the heat of a power resistor actually burns a hole through it. No way to fix that without replacing the entire board! Printed circuit boards also exhibit small amounts of capacitance between traces and the board material itself is not a very good dielectric, which can smear the sound to a degree. That said, we do use printed circuit boards in non-critical areas, like power supplies and logic circuits.

Here things are beginning to come together. This is part of the on-board power supply bypassing for the output stage. Also seen in the background is the filament supply circuit with damping resistors and +50V injection to cap off hum and prevent too high a voltage differential between cathode and filament at the input stage phase splitter. Heat resistant ceramic tube sockets are employed for long life and no arcing. All signal path junctions are soldered with silver content solder and care is taken at every step to ensure solid connections and future serviceability.

The next picture shows the input stage under construction. Each half of the input tube (12au7a) is bypassed to prevent power supply interaction between stages. The first stage is a simple voltage amplifer with feedback from the output transformer injected at the cathode, which is bypassed with high-quality solid polymer electrolytic caps. These have outstanding low impedance and ESR properties and live well in high-heat environments. This stage is direct coupled to a spit-load phase splitter which has a build-out resistor in the cathode leg to match output impedances of both halves for better high-frequency linearity.

In this picture the input stage / phase splitter and driver stage are completed. In a novel implementation of local feedback and bootstrapping this little stage delivers the needed voltage swing to drive the output stage to full power at low distortion. One wouldn't normally consider the 12au7a to have the balls to do this! High-quality polypropelyne coupling and bypass capacitors are used throughout. All wiring is high-tempature and rated for applied voltage.

Here's the completed circuit board installed to the top panel with transformers mounted and wired into the power supply circuitry, which can be seen along the bottom. On the left is the main B+ supply, on the right is the bias supply and filament damping circuit. Off to the side can be seen a small printed circuit board which houses the 60 second B+ delay, which allows the filaments to heat up fully and applies the bias voltage before the high-voltage hits the tubes. The output stage employs an LR network to equalize the small inductance differences between windings in the output transformers. This also improves high-frequency linearity.

Speaking of transformers, all transformers used in Elliott Studio Arts products are custom wound to our own specifications by a well respected company based in New Mexico, Edcor Electronics. The excellent sound quality and bass control of these amps can in large part be credited to these transformers. The power supply transformer is massive with ample power regulation; in conjunction with the big computer grade caps and choke provide huge power reserves which greatly increase dynamic impact and slam. The power supply is very clean and well protected with fuses and inrush current limiters, which can be seen below mounted to the terminal strip in the bottom chassis.

The top cover and circuit is now wired to the bottom chassis, the input connections have been wired and the output transformer secondaries are hooked to the speaker jacks.

The next step is to install tubes, connect meters to monitor B+, bias and filament voltages and an O'scope and dummy loads to the output. Now fire her up!

After everything checks out, the bias is increased until the proper current reading is applied to each tube, voltages are checked again. Once everything stabilizes it's time to throw some sine waves at it and check for oscillation, frequency response and max power output. Then a complete battery of computer generated tests including frequency sweeps, distortion and square wave response is done and documented for record keeping.

The face plates are installed after all the testing is complete. The amp is then installed in my reference system for a week to burn it in and listen for any anomalies. It is then packaged up and shipped to the customer for many years of happy listening!

Thursday, October 21, 2010

Tube Stomp Box

Tube Stomp Box for digital recording

A good friend of mine is an accomplished guitarist who has a recording setup for his band. Part of his rig is an amp simulator plug-in that he uses with digital input (AD converter) to simulate the tone of an amplifier. Recently he asked if a tube guitar pedal would add that tube 'roundness' to enhance the sound of his recordings. This sparked an idea..

I figured that any stomp box has to be small and portable, powered via wall-wart and have a bypass switch. Having lots of tube stuff and parts around I scrapped a prototype together on the bench. In the photos above and below you can see the first attempt at the circuit. To fit the requirement of wall-wart power meant that a high-voltage B+ supply had to be derived from a low voltage source. I settled on a 24VAC @ 1 amp supply sourced from Triad, which when run into a voltage quadrupler yields 160VDC at about 200 ma. The filament supply would have to come from the 24VAC, padded down with series resistance to get 12VAC. OK, so with the PSU figured out it was on to the tube gain stage.

My first attempt was to use the venerable 12AX7, which as you will see proved problematic. I used both halves of the tube to make two identical stages with a gain of about 35dB each. I put a volume control between stages figuring that the guitar volume control could be used a a gain and the stomp box control could be used for drive so you could get some overdrive. The gain of the whole circuit was way too high to input into a guitar amp (or amp simulator) so the plan was to knock it down with an output transformer.

Alright, so far so good.. looked clean on a scope, got plenty of gain and overload margin was acceptable. Then I put it in a box and hooked it to an amplifier- BUZZ! HUUUMM! Oscillation! Microphonics! High frequency rollof! I was surprised, everything looked fine before putting it in the box. Too much gain coupled with wiring capacitance and high impedance created all sorts of problems. I worked on adding more filtration to the power supply, DC filaments and shielded cable to no avail (high-gain, high impedance tubes such as the 12AX7 have issues like this).
I had to look for another solution.

Well, of course! Change the tube to a 12AU7, get rid of all that gain and all the associated problems go away too. And as fate would have it, the plate and cathode resistor values worked out perfectly for the given voltages so the 12AU7 could just drop right in. Less gain equals lower miller capacitance, meaning flatter frequency response and less sensitivity to induced hum, microphonics and oscillation. This tube also has lower output impedance making it easier to drive long(ish) unbalanced interconnects which are likely to be use with this device. So with less gain and lower output impedance the output transformer could be eliminated too.

So, done for now. I will ship this out to him to see what he thinks, probably end up making some changes according to his feedback and then who knows? Maybe another Elliott Studio Arts product?? We'll see..

 Nope! This project was a failure... My friend could not get rid of the buzz. Probably due to sharing the same supply for the filaments and the B+. He still has it so I have no way to experiment and figure it out~ Oh well, next time I'll do an isolated DC supply on the filaments..

Saturday, October 2, 2010

This really makes a difference....

I am amazed at what I'm (not) hearing!
Have you ever noticed how your system sounds great on some days and kind of grainy and harsh on others? Usually sounding more sweet late at night? Dirty power - that's what I say! During the day when usage is high in your area microwaves, electric motors, ubiquitous switching supplies, fluorescent CFL bulbs, etc. generate tons of spurious RF and harmonic noise that gets into your sound system and robs it of clarity and silence, adding grit and grain and listener fatigue.
I discovered the Surgex power conditioner ( years ago when their product rep visited our office for the dog and pony show, and since then always wanted one. I have recommended them to clients (see my previous post: "Power Conditioners and Hype") and have heard how they cut down on the noise in various sound and video systems, not to mention the superior surge protection they afford. So I finally broke down and made the purchase, opting for the more industrial looking (and cheaper) pro A/V unit rather then the home model.

Since all my equipment was plugged into a power strip it was a simple install: Plug in the Surgex and plug the power strip into it. I let it cook for a day before I had the opportunity to really evaluate my system with this new change. My first impression was immediate- I put on my vinyl copy of Alan Parsons Project 'Pyramid'; it sounded as it does late at night when the backgrounds are blacker, the highs are more shimmery and pure and the sound is generally more liquid and transparent. But even more so than what I'm accustomed to hearing in those (rare) late night sessions: blacker silence, more transparent, more vivid, more liquid. No fatigue, zero, nada, nyet. The bass tightened up, cymbals sounded more real and brassy, voices more pure. I heard vocal tracks way back in the mix I hadn't heard before. Even the hum in my already quiet phono stage w/ no signal was less.

The improvement to CD's was more profound, making them sound more analog and pure, removing that last bit of elusive to describe 'digititus', especially in the high frequencies; again, cymbals sounded more like cymbals. Everything was more liquid, more transparent, more like music from top to bottom. More detail but without the fatigue. I could go on but I'm starting to sound like one of those audiophile magazine reviewers (which I read all the time!)

The bottom line is if you've invested substantial time and resources into your system you owe yourself the protection that these units afford. The cost of the Surgex isn't cheap but not much compared the the price of replacing all your gear, some of which may not be replaceable. But with the improvement to the sound, having the best surge protection technology in the world is just the icing on the cake! You cannot buy these units retail at the Best Buy, you'll have to go to the website and find out who your local rep is and order one from them, but it is mandatory!

Happy Listening!

Monday, May 10, 2010

The making of a preamp

Building the 66-001p Vacuum Tube Reference Preamp
(an overview)

Well, it's been a while since I've posted here. I've been working on a preamp that is bound for review. The picture above is the regulator section for the outboard PSU, which in this case is configured for 120VAC / 60Hz. The regulator board is the only circuit board used in the entire product. Circuit boards are convenient but can color the sound as they are a giant capacitor with not so good dielectric. All of my products use point to point wiring as seen in this photo of the RIAA section under construction.

The circuit resides on an aluminum sub-chassis that is isolated from the main casework via 8 nitrile rubber bushings. The entire sub-chassis is the ground plane, and there is copper buss wire connecting all grounded points in the circuit. This provides a low-impedance ground path and helps to shield against noise. The RIAA preamp uses a fet/triode cascode for the input stage for high gain and low capacitance.

All the wiring is high-temp Teflon insulated solid conductor for signal and stranded for power. Silver solder is used throughout along with close tolerance metal film and wire-wound power resistors, polypropylene capacitors, (hand matched polypropylene and polystyrene caps used in the RIAA filter), and high-quality electrolytic and polyester caps for power supply bypassing. Solid polymer electrolytics are used for the cathode bypass capacitors; these have very low ESR and a long life span. You can see them in the picture above zip-tied to the yellow poly bypass caps. Below shows each tube section has 110uF of bypass capacitance. High quality ceramic tube sockets are used for longevity.

Below you can see things starting to come together. Those are the output transformers, used here for gain reduction and impedance matching. These transformers have an output impedance of 8 ohms! They drive headphones with authority and since the output impedance is so low you can run very long interconnects without high frequency roll off. The signal cable you see is high-speed digital coax used for HDTV and VGA applications. It has very low capacitance and uses foamed Teflon for the dielectric, has a silver plated solid copper center conductor and dual shield (foil and braid).

The front panel is where you see the functional interfaces; volume control (Alps Blue), balance, mute and mono, input selector (silver contact) and headphone jack. The balance control works in shunt mode and is out of the direct signal path. Moreover, it's action is limited to about 10dB of variation. The balance, mono, volume and mute controls can be seen in this picture.
The casework is steel with a nice satin texture paint job which hides fingerprints and other maladies well. The steel does a good job blocking RF interference.
Below is the nearly completed preamp awaiting the top and bottom covers and faceplate. These units take about 24 hours of labor to put together as every component has to be placed, every wire cut to size and dressed, components have to be measured and matched. Then multiple tests and measurements are done and finally a listening evaluation. This is not to mention the amount of engineering, prototyping, testing, measuring, listening, re-evaluating and modifications that went into the design. But a labor of love, to be sure!
So, I'm not going to give away all my secrets~ But I can assure you that this preamp performs very well in the measurement world and even better in the listening room! For full specifications and performance data please visit my website:

Thursday, March 25, 2010

Resurrecting the McIntosh MC-30

The Mighty McIntosh

My boss Jack has had a pair of old dusty and slightly pitted MC-30's laying in his office for several years. The story was that they belonged to his father who purchase them new sometime in the golden age of Hi-Fi, and they had been languishing at the home of one of his other sons for years. Jack came across them and rescued the pair thinking that someday he would put them to use driving a pair of Renkus-Heinz commercial 16ohm speakers we've had in our warehouse, also collecting dust. Well, he finally asked me if I could do something with them.. duh!

I got them home (heavy buggers!) and got one up on the bench, opened it up and found that some repairman from the distant past had done some meatball surgery that had to be corrected. One of the amps power supply section was really messed up by someone - the rectifier feeds a 30uf cap first, then a 150 ohm power resistor to an 80uf section forming a CRC filter. But what I found was actually a 10K power resistor feeding the second stage filter (which is B+ for the output stage). I don't see how this could have even worked! Plus, there was a 12au7 instead of a 12ax7 in the driver cathode follower stage. Also, the power cord had long since disintegrated and there were some burnt wires (why did they use 22 gauge wires from the rectifier to the filter cap??), but overall things looked pretty good.

First things first, get rid of all the 45 year old electrolytics! Except for the main filter caps, which measured good with the cap meter (all 3 sections), there were dried up bias supply caps and input stage cathode bypasses that had to go. Also, the paper/wax coupling caps were suspect; I've heard that they tend to get leaky- though some audiophiles like the way they sound. I don't. I like detailed music reproduction, thank you. These caps would be good for a guitar amp where you're going for a colored sound, not Hi-Fi (now days there are very expensive 'boutique' paper in oil capacitors available, I'm not talking about these). Most of the other coupling caps are some sort of plastic encapsulated film, not sure about them. I left them in for now.

Since Jack is not an audiophile I didn't use any exotic parts; rather than an 'upgrade' this project is more of a resurrection. I used what I had on hand. I replaced the caps listed above with standard modern electrolytics, replaced the output stage coupling caps with poly film (.47uf @ 630V) and installed grounded power cords (I cut the IEC ends off of some stock power cords that come with AV equipment). I also put in some 330uf @ 450V Panasonic snap-in caps that I've had laying around since the '80's (these were in the first iteration of the ESA 66-100 which have long since been scrapped for parts). These I paralleled with the 80uf main B+ caps, and bypassed them with some .1uf 450V poly's.

I do see alot of room for improvement, though. Like replace all the old coupling caps with decent film caps like Solen or better, do more power supply bypassing for the input and inverter stages and get rid of all the unnecessary input wiring and hardware. The input RCA's could use an upgrade, and a heavier barrier strip so you can connect some 'real' speaker cables would be nice.

The design of the amp is interesting. There's the obvious 'Unity Coupled' output transformers which have a cathode winding from one tube in phase with the plate winding of the other tube. There is the 'bootstrapping' of the driver; the B+ for the driver load resistor is derived from the plate winding of the same phase tube giving a positive feedback to the driver tube while delivering negative feedback to the output tube. And there's the 12ax7 cathode follower between the driver and output stages, direct coupled to the input grids and therefore having the -45V bias voltage on their cathodes. This tube is also bootstrapped; the positive feedback is necessary to derive the very high AC drive voltage required for the output stage (remember the cathodes are in the transformer winding causing negative feedback, lowering the overall gain of the stage). The input stage is pretty standard and uses 1/2 of a 12ax7 direct coupled to a 12au7 configured as a cathode coupled phase inverter. The McIntosh design was way ahead of its time and the performance is reported to be excellent. All in all, alot of circuitry for 30 watts!

Ok, so after all the circuit work, I cleaned up the chassis and tubes, plugged them into AC, and checked out the voltages. One amp measured spot-on, the other had some funkyness in the output stage. One output tube was in cutoff and it's bias voltage measured -220v! Some visual inspection revealed that I had inadvertently cut a 220K cathode resistor for one of the followers, which supplies bias voltage to the grid of the 6L6. Repairing this error fixed it right up!

Alright! I'm too impatient to put these things on the scope and do the requisite battery of tests, I just want to plug them in and play some tunes! They sound pretty fine, I must say. They're a little dark and the bass is not as tight as I'm used to (the 66-100's are highly resolving and have excellent, tight bass). But overall, they have that tube magic. I bet new output tubes and performing the rest of the upgrades as listed above would bring them into better focus, but my boss just wants them to work and I think that they'll do just fine with the high-sensitivity horn loaded Renkus-Heinz speakers he's going to drive for his office system.

I promise I'll get these things hooked up to the scope and see what the power, frequency response and square wave look like, but for now I'll just enjoy them before I have to give them back!

UPDATE: 3/28/10

Just put these babys on the test bench. Amplifiers terminated into 8 ohm resistive dummy loads.

Square wave response is good for 1Khz, 10Khz is a bit rounded off on the leading edges, suggesting a bit of high-freq. rolloff.

Freq. Response is flat from about 30hz out to about 15Khz, and there's a bit of droop on either extreme, as viewed on an o-scope.

Power is 45 watts before visible clipping on the amp with the better output tubes. The one w/ the weaker set puts out about 25 watts before clip. Think I'll recommend new tubes to Jack.

No distortion measurements made at this time.

I had fun restoring these amplifiers. They are very well made, well laid out and easy to work on. I'm sure Jack will enjoy listening to them as much as I have!

Tuesday, March 23, 2010

Home-brew high end speaker cables

Becoming interested in a few DIY projects seen online I decided to make my own speaker cables to replace some home-made jobbies that I'd been using for about 10 years..

Since I work in the commercial A/V field I have collected a ton of surpluse cable and wire over the years. Having an abundance of CAT5E cable on hand it was a cinch to choose one of the projects that feature use of that sort of cable. The final design of the cable is a distillation of several articles that covered the making of your own speaker cable.

Needing approximatley 15' runs I played out eight 18' strands of CAT5E cable. I then made four twisted pairs out of the 8 strands, twisting counter-clockwise. I then took two twisted pairs and combined them, twisting in clockwise direction. This made two rather thick braids of CAT5E about 16' long, of which I secured the ends with electrical tape.

Next I cut 4 6" long pieces of heavy 1" heat shrink and slid them down the cable ends. Then stripped back about 6" of each of the four strands at each end. Next I un-twisted every pair, sorted them out (stripes and solids) and combined all the solids together and the stripes together. I then twisted each bundle and wrapped with teflon plumbers tape. Next I pushed 3" of red heat-shrink down the "solids" bundle and 3" of black heat-shrink down the "stripes" bundle. Next, shrink the black and red wraps on the bundle ends, pull the 1" x 6" heavy shrink up the cable to cover the transition point where the bundles are seperated out of their CAT5 strands and shrink. I then put some hot glue into this cover between the bundles, heated and pinched together with big needle nose pliers to clamp the shrink together and make "pants" over the transition point and the bundles.

Next I stripped each individual strand of the wire bundles for pos. and neg., trimmed to length and crimped on heavy fork connectors, then soldered with silver content solder. Heat shrink was applied over the connectors for a finished look.

Upon first listen they sounded terrible. But after about 1/2 hour of listening they started to break-in and sound better. Now with about 6 hours on them they sound wonderful! Tighter bass, more texture and detail in the lower registers, better integration of the whole sonic picture and a more even presentation of the frequency range. More detail is heard, more low-level stuff like reverb tails, backing vocals I'd never noticed before, etc.

Since CAT5E cable is rated for 350Mhz it should work fine as an audio cable. Even better is that the positive and negative conductors are all seperated and twisted together in individual pairs, and each individual CAT5 strand is twisted with another, and so on. This results in very low inductance (but rather high capacitance, though that doesn't matter as much as inductance for speaker cable) and low resistance. Also this design eliminated the smearing of signal and skin-effect losses associated with multi-stranded cable because each strand is individually insulated, much like Litz wire.

Anyway, DIY is awesome, and cheap!

Friday, March 5, 2010

Power Conditioners and hype..

In my day job I am a service technician for a medium sized regional A/V contractor. Most of my work involves troubleshooting audio systems and optimizing performance. I have the opportunity to work with some very nice equipment in beautiful environments, like some of the local church sanctuaries around Seattle. One such system involves a church that is used as a venue for performing and recording sacred music, especially involving period correct interpretations of the music score with appropriate instrumentation. The acoustics of this church are perfect for the exquisite pipe organ and musicians; not so much for the spoken word (the two are often mutually exclusive and our job is to try to integrate sound reinforcement into these challenging acoustic environments).

Last year we erected a 25' scaffold in order to install 4 hanging mics from the very tip of the ceiling- high-quality Neumann condensers, two at about center stage and two out in front of the stage and about 12' off the floor. The cabling was run to a mixing console in the rear of the sanctuary and then fed to an Alesis Masterlink hard-disk recorder. The sound captured with this set-up is incredible, but the mics are so sensitive that they can pick up a whispered conversation at the back row!

The music director and the recordist / board operator had been reporting an intermittent noise coming through on the recordings. Intermittent problems are difficult to troubleshoot and the first time out I couldn't re-produce the problem. The second time out I was able to hear the noise through the monitoring headphones. It was a nasty intermittent buzz that varied in intensity and character. We swapped in another console and the noise went away, so I determined that it must be something in the consoles PSU and sent it away for service.

They actually did find something wrong- the phantom power supply was bad and they replaced some components. But after installing the repaired console back into the system the buzz was still there. ??!! Then I noticed when we moved the power cables around behind the desk the intensity of the buzz would vary, and this led us down the path of changing out extension cords and eliminating some cheap plastic power strips. Also, uncoiling the power cables and laying them flat under the desk took care of some more of the noise, but it was still there to a degree which was clearly audible on the recordings.

I then recommended another option that I thought would work since it seemed due to dirty power. That was installing a high-quality series mode power conditioner in the system. The Surgex SA-82 fit the bill and was ordered. These units are expensive but they really do the best job of surge suppression, and unlike MOV based surge protectors they last forever and don't dump dangerous and noisy voltage to ground. The side benefit is that because they use a large series choke to do the surge suppression they filter out way more noise and nasties on the power line than do the tiny little RFI filters found in most professional surge suppressors.

Well, it worked like a champ. All of the noise, buzz, hum and grit was gone, and the sound has taken on a more relaxed and open quality. They really do work. Check out their website for more information on how they work:

The power grid is getting noisier all the time; everything has a switch-mode power supply these days, and those CFL light bulbs they're pushing on us throw out noise too. Plus the utilities can at times send big voltage spikes into your house when working on the lines, it's happened to me! Cheap insurance to protect your stuff.

So, the hype is that these units do an excellent job at protecting your equipment at the same time cleaning up your power from noise, and are much less expensive than some of the crazy audiophile type power conditioners out there.
I think I'll get one for myself!

Monday, February 22, 2010

Turntable Tinkering!

I love vinyl, but was always looking for ways to improve the sound. I built a dynamic noise canceller circuit, installed equalizers, dynamic range expanders and all manner of processing to try and improve the sound of some recordings. When CD players first arrived on the scene I was in High School, and a couple of guys from our local community college came by our electronics class and told us about "perfect sound forever". I was skeptical but intrigued. It took a few years before I could afford to buy one (an ADC I believe) and a CD to go with it (Paul Simon's greatest hits). I was blown away by the lack of noise and distortion that plagued my records. But after time I got bored and kept buying vinyl... that is until about 1990 when you couldn't really buy new releases on vinyl anymore.

About 1995 my boss gave me his old Thorens TD125 mk1, in a box, in pieces. I had to glue the plinth back together, re-build and install the Rabco SL8-E tonearm and do all the necessary lube and adjustments. This is an adjustable spring suspended table. I have been using this table for the last 15 years and have done several modifications to improve the performance that I will list below.

1st- Completely disassemble and install self-adhesive thick sticky tar-like sheeting I picked up from a jobsite (it is used on the outside of new construction commercial buildings as a heavy vapor barrier) to the under-side of the platter and aluminium top plate in an attempt to damp vibrations. This made a subtle improvement in clarity and lowered the noise floor.

2nd- Finally sell of the old Rabco and install a pivoted arm. I picked up a used arm from a Music Hall MMF 5 and built a new arm-board out of plywood. This made a huge improvement and cleaned up much of the distortion on the inner-grooves that had always driven me nutso.

3rd- Install a vintage Audio Technica AT14sa cartridge with a stylus from an AT13ea. This was a top of the line cartridge back in the day (late 70's) but I didn't like the shibata stylus and opted for the elliptical from the AT13ea. I'd put this combo up against many modern high-priced cartridges. It blew away my Grado and works very well in the 9" MMF arm.

4th- FINALLY get an accurate alignment protractor! I had been using a dB systems protractor for years and have always been annoyed by the tracking distortion towards the inner grooves of my albums. I thought that was my fate until the recent article in Stereophile by Keith Howard on the subject (March 2010 issue). He states in the article that most alignment protractors are based on math that is an approximation. He offers on his website ( a simple program that will generate an alignment protractor that you can print out. You just enter your arms effective length and the inner and outer groove diameters you wish to use (explained in his article). SO, after printing it out and re-aligning my cartridge (I love the AT cartridges for their square sides and front - makes alignment easy) with a magnifying glass and much patience I was ready for the test drive. WOW! What a difference it made! I had no idea that tracking distortion could muddy up the sound so much. Everything is much more clear and natural sounding now, more relaxed and more detailed and liquid and (insert overused audiophile term here). No, really, it was that good.

5th- On the advice from several sources on the inter-web ;-) I removed the springs from the TD125 to make it a solid, non-suspended table. Since I've used them under components as feet to good effect I replaced the springs with cork bottle stoppers. (Ask me if you're confused and want more detail). This also made a major improvement in resolution and soundstaging, tightened up the bass and made the speed more stable.

So, after 15 years with this turntable and 30 years playing records, I've finally put to rest the tracking distortion that had been a bane to my existence. My turntable now sounds incredible, probably couldn't buy as good of performance for under $2500 bucks now. Of course the Elliott Studio Arts 66-001p preamp and 66-100 power amp have much to do with the wonderful sound...

Modifying the Rega Apollo CD Player

Recently I decided I needed a better CD player to use as a reference (I do have an audio manufacturing company after all- and the best I can currently afford is the Rega Apollo. My old AMC CD8b gave up the ghost a while ago, and since I mostly play vinyl didn't really care much.
Well, after getting the unit home (I bought it used from a local retailer in Seattle, Hawthorne Stereo - thanks Matthew) I just HAD to open it up and see..

Damn nice! High-end epoxy circuit board, nice components, etc. Not much for power supply bypassing around the discreet transistor output stage, though. And alot of 'lytic coupling caps, too. Also, the PSU for the audio stage doesn't have active regulation, just a simple shunt zener "regulator". But it sounded so much better than what I was used to that I let it be... for a while. I can never just leave it be.

So the first mod that I wanted to try was to increase the PSU bypassing on the output stage and install polypropylene bypasses around the output coupling capacitors. I had some 1uf Electrocube poly's for this, and ordered my favorite low-voltage electrolytic bypass caps from Mouser. These are solid organic polymer electrolytic that have very, very low ESR and will never 'dry out'. I use them for cathode bypass in my tube products.. they work great and sound great.

Carefully, I removed the 4 polyester .1uf bypasses, installed the 100uf 16V (Vishay 94sa107x0016epb) organic polymer caps, then re-installed the 4 polyester caps to the underside of the circuit board, along with the 1uf Electrocube output coupling caps in parallel with the stock electrolytics. Now I put it all back together and didn't have any leftover screws! Yay!!

The caps needed to break-in so I let it play in repeat for a day or so, and then listened to my favorite evaluation disc, YES Talk (1993- killer dynamic range and lots of recorded detail). There was an improvement in dynamic slam and a sweetening of the high-frequency details. The bass is tighter and more textured and at the same time goes a bit deeper. Overall an improvement... maybe I'll leave it alone for a while. We'll see...