|About the Kits||Rebuild Examples||Assembly Manuals||FAQS||Stereo 120 Repair Information|
|Power Supply Update Kit||Dynamite Capacitor Configurations||Blue Light Kit||PAT-4 Pages||PAT-5 Pages|
|Submit a Question||Testimonials||updatemydynaco store||Speaker Refurbishing||Bridging Mode|
|Akitika GT-101||Akitika store||Clean Connectors||updatemydynaco store||Stereo 400|
The Dynaco Stereo 120 Power Amp was revolutionary when it came out in the mid 1960's. It had some problems, though, mostly related to under-biasing of the output stage. The result was the cross-over distortion that came to be the unpleasant hallmark of "transistor" sound. Forty years of progress later, we can do a lot better. With our kit, you recycle and reuse the highest quality, timeless parts of the Stereo 120, and replace the parts, e.g. the amplifier and power supply regulator modules, where technology has made the most improvements.
It's actually true! The updated amplifier modules have been improved. We've included some (but not all) of the improvements of the GT-101 amplifier modules into the TCK modules. The improved version is called Rev B.
Pick just the parts you need at the Updatemydynaco Store to bring your Dynaco Stereo 120 Power Amplifier back to life, to improve it a bit, or to take it about as far as you can go.
Our two kits for the PAT-4 are incredible values. The DRD-4 kit reduces the distortion of the high level stage by a factor of 10! Our TCS kit lets you swap out the almost never-used HI FILTER switch for a switchable tone control disable. Check them both out in our store. Just looking for good information? Check out the PAT-4 Pages.
Our latest kit produces rock steady, extremely low noise power supply voltages for the PAT-4 Preamp. We think you'll love the way your PAT-4 sounds when you install this new power supply. Here's the PAT-4 Power Supply ordering information and Assembly Manual
Let's say you don't have a Stereo 120 to update, but you still want to build a power amplifier kit...One that puts out more than 50 Watts per channel into 8 Ohms, and nearly twice that into 4 Ohms. It sounds great, and uses top-notch components. Visit Akitika's website and look at the GT-101 stereo power amplifier kit.
Does your 40+ year old Stereo 120 still have working amplifier modules? Do you want to keep the original modules while still improving your sound? You might want to try:
We've got the stuff that lets you make your Dynaco Stereo 120 Power Amp and PAT-4 Preamp better than new. It's right here in the store. Amplifier modules, super heatsinks, replacement capacitors, power supply replacements, beautiful blue lights and even new feet! It's all here.
The website has grown so much, it's easy to miss something that you're looking for. Use this search box to find what you need.
The original UpdateMyDynaco kit recycled the original Dynaco heatsinks. Those heatsinks were perfectly adequate for music listening, but a bit marginal for heavy duty use. That's why we've introduced the Super Heatsink Option. The Super Heatsinks are direct replacements for the originals, but are 3 times as thick, at 3/8" versus the original's 1/8" thickness. The result allows the LM3886 to deliver significant 4 Ohm power, more than 100 Watts!
Ordering the Super Heatsink Option has added benefits:
Order the Super Heatsink Option from the UpdateMyDynaco store.
the original black heat sink (on the left) is only 1/3 as thick as the super heat sink (on the right)
update kit with the super heat sink option
Lots of people used to build electronic kits. Heathkit, Eico, and Dynaco let anyone assemble great stuff and save a lot of money. On top of that, building the kits was relaxing, educational, and rewarding. Weíre here to say that the good times are back! UpdateMyDynaco has designed a high performance amplifier replacement module kit that lets you make your Stereo 120 better than new.
The Dynaco Stereo 120 was the first powerful (60 Watts/Channel) transistorized stereo power amplifier in wide production. My uncle had the Stereo 120, PAT-4 Preamp, FM-3 tuner, and A-25 Loudspeakers. In 1968, that was the good life! I always liked the look of the amp, its size and its shape. The neon-illuminated crystal clear rocker switch promised power with its orange glow in a darkened room. As I studied engineering and analog design, Iíd marvel at all the function the Dynaco guys crammed into those few transistors.
Forty years of technological progress allows us to bring you lower distortion and greater efficiency, along with protection circuits that make your amp nearly bullet-proof. Our Update Kit for the Dynaco Stereo 120 lets you rescue your Dynaco from demise in the dumpster and make it better than new! Many old Stereo 120ís have dead or dying amplifier modules. The update kit consists of new amplifier modules that you build. You recycle the power supply and chassis, and replace the old amplifier modules with the new. In a few short hours youíre ready to listen to tunes on equipment built by you!
You can buy the modules in kit form, or assembled. Youíll need an old Dynaco Stereo 120, as you will re-use its chassis, power transformer, and power supply. Our detailed construction manual guides you step-by-step through the process. Itís easier than a jig-saw puzzle, and a lot more fun.
The kit costs $89. That gets you two 60 Watt Amplifier module kits, and for a limited time, free shipping in the USA. A pair of assembled and tested circuit boards costs $139. The assembled and tested version is currently built to order, so you'll have to wait a little bit to get one. You can buy all the variations here. Either form still leaves a lot of fun for you ripping out the old stuff and putting in the new.
|TCK||Two single channel amplifier update kits||$89.00|
|TCA||Two Assembled and Tested single channel|
amplifier update kits
|SHS||Two Super Heat Sinks||$20.00|
|FFT||Set of four vinyl feet. The original ones |
tend to disintegrate after 40 years.
|PSRC||Power Supply Replacement Capacitors, |
for use with the Updatemydynaco kits
|PSUG||Power Supply Upgrade for Regulator, |
for use with either original Dynaco or Updatemydynaco kits
|BLUE||Blue Light Kit, |
for Stereo 120, PAT-4, Stereo 80, or SCA-80 Power Switches
|DRD4||Distortion Reduction Kit for PAT-4, an unbelievably economical |
way to reduce distortion by 10X
|TCS||Tone Control Switch for PAT-4, replaces the HI FILTER that |
no one ever uses with a tone control defeat switch
|C12XX||Take C12 from stock 3300 uF to 20,400 uF for better Bass||$21.00|
|PAT4PWR||Improve the sound of your PAT-4 Preamp with an electronically Regulated Power Supply||$39.00|
|C7X2||Better bass for original Dynaco amplifier modules.||$25.00|
The amplifier modules are built on high quality 2-layer FR-4 PC Boards. Critical signal path capacitors have high linearity NPO or poly-film dielectrics. The output capacitor stays very linear owing to the constant bias voltage. The resistors are metal film, mostly 1% tolerance.
Kit construction has three steps:
The kit uses all through-hole components. The circuit board has been specially designed with generous spacing between all the soldered points, making assembly easy.Check out our YouTube video, where we summarize the assembly process.
To keep the assembly process simple, we've written manuals tailored to each kit. Click on the links to download the described item.
If you're having trouble viewing the manuals in Firefox, the following tip may be helpful. Go to Tools=>Options, pick the "Applications" tab. Scroll down and look in the left ("Content Type") column until you see any entries that include the words "Adobe Acrobat". In the adjoining space in the right ("Action") column, select "Use Adobe Reader (default)".
Q. How long does it take to assemble?
A. Probably less than 5 hours of work. Disassembly takes about 1 hour. Building the new amplifier boards takes about 90 minutes each. Reassembly takes another 90 minutes.
Q. How much of the old Stereo 120 has to work?
A. Just the power supply.
Q. What tools do I need?
A. At the minimum, youíll need:
Itís also handy, but not necessary, to have:
Q. I haven't soldered for a while. Is there somewhere I can get a refresher?
A. This youtube video reviews soldering technique.
Q. Do I have to be an electronics genius to build it?
A. Not at all. If you can stay calm and follow directions, you shouldnít have any trouble.
Q. Do I need any supplies that arenít in the kit?
A. Just isopropyl alcohol and some paper towels for clean-up. Just be careful about paper towels and isopropyl alcohol...they are a flammable combination. We supply solder and all the hardware youíll need. Youíll recover the wire and screws youíll need from the old Stereo 120. We recycle a number of the bits into the updated design. We even supply the thermal compound you need.
Q. Can I see schematics of the updated amplifier module?
A. Click here for a schematic of the amplifier module.
Q. What are the shipping options?
A. All shipments are by USPS Priority mail. This makes it easy for us, and gives you free shipping. The only exception is if the value of your order is less than $89.00, we charge $5.00 shipping.
Q. How is the new design different or better than the original design?
A. There are a number of ways. Here's a short list:
Q. What IC is the design based on?
A. The design is based on National Semiconductor's LM3886.
Q. I don't see the answer to my question here. What can I do?
A. Submit a Technical Question
The following plot compares 1 kHz THD+N versus output power for the old (original) and new (UpdateMyDynaco) designs. Note that the old design distortion increases a bit at first, indicating crossover distortion. The new design's distortion and noise is about 1/10 as much, and decreases smoothly as the level increases. This indicates a relative absence of crossover distortion. (Note...the absolute power numbers may be off by a few percent) The overall decrease in THD+Noise for both amps with increasing power just reflects that noise is a smaller part of the output as the input level increases.
The original Stereo 120 had significant crossover distortion, visible as extended numbers of high harmonics at small output signal levels, like half a Watt. That crossover distortion was one of the most recognizable shortcomings of early transistor amps. The figure below shows the dB relative amplitude of the harmonics in the original Stereo 120:
Notice that the second harmonic is down about 60 dB, with 20 harmonics visible, indicative of classic crossover distortion.
The UpdateMyDynaco Stereo 120 has almost no distortion at a half Watt of output:
The second harmonic is down 92 dB, while the few other harmonics are more than 110 dB below the fundamental!
At 6.25 mW of output power, the differences are even larger. The original Stereo 120 crossover distortion harmonics are down 60-70 dB:
The UpdateMyDynaco Stereo 120 has harmonics in the noise floor, more than 100 dB below the signal.
Here are some scans of historic documents about the Stereo 120
The updatemydynaco assembly manuals typically have all the information you need to make your Stereo 120 better than new. Still, some people like to keep their Stereo 120 original. Hereís a set of pdf files with high resolution scans of an original Stereo 120 assembly manual, plus a sheet with revisions.
Weíve written a few documents, in case you want to repair your old Stereo 120, or just learn more about power amplifier design.
The Classic link for lots of Dynaco stuff is here:
Tubes 4 hifi specializes in tubes and tube based mods for Dynaco equipment, but they
keep a great page with all the Dynaco Solid State Schematics
If you're visiting this web site, you probably enjoy Audio DIY as a hobby. Here are some links you may find interesting:
The Stereo 120 wasn't the only history making amplifier, here are a few others:
These tube amps were designed by Hafler and Keroes before there was a Dynaco:
An older Audio Research and Mcintosh Design:
I found some lovely old brochures in my files...a short (4 page) brochure, and a long (16 page) brochure. The scans are in color, and the 16 page brochure has 5 pdf files of about 6 Mbps each.
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