Amplitude Audio

Amplitude Audio Guitar and Bass Amplifier Service and Repair

Long time, no post. How's everyone doing? I know I'm terrible at this social media thing. Life has been busy in the shop...
03/16/2026

Long time, no post. How's everyone doing? I know I'm terrible at this social media thing. Life has been busy in the shop and I'm excited that my MaxiMatcher II output tube tester has arrived. New bench gear is always fun.

A small sample of the equipment I've serviced recently. Just want to send out a HUGE thank you to everyone who has kept...
05/02/2025

A small sample of the equipment I've serviced recently. Just want to send out a HUGE thank you to everyone who has kept me busy! I'm grateful that you trust me to get your gear healthy again.

Check out this beauty! This 1975-ish Fender Bronco (VibroChamp) came in requiring a new AC mains cable. When the mains...
02/26/2025

Check out this beauty! This 1975-ish Fender Bronco (VibroChamp) came in requiring a new AC mains cable. When the mains cable present in any amp has the outer plastic insulation split in several places revealing the inner wires, it's time for a new one. The amp was wired with the neutral fused when it arrived, so it was re-wired with the live fused first and both neutral and live are now switched. The mains AC ground was also originally mounted on a transformer mounting bolt - not a safe practice - and is now attached to the chassis at its own dedicated ground point. Because the amp was being used on some road dates, bear-trap retaining clamps were also installed on the power and rectifier tube sockets to ensure reliable tube pin to socket connectivity. Thanks very much !

Happy 2025! Just want to send out a huge thank you to everyone who kept me extremely busy in 2024. I'm very grateful fo...
01/07/2025

Happy 2025! Just want to send out a huge thank you to everyone who kept me extremely busy in 2024. I'm very grateful for your patronage. The last few months of 2024 included a few rebuilds / restorations that always have a hiccup or two and seem to take forever.

One cool project from 2024 was a conversion of an old Traynor YVM-1 Voicemaster to a two channel Marshall / Fender amp. The original amp was an amplifier that would have been used to power a small PA for weddings or live music. Now it's a versatile two channel amp with one channel very similar to the Marshall (SIR #34) amp Slash used on Appetite for Destruction and the other channel identical to the preamp of a Super Reverb. With a PPIMV, this baby can do almost anything at bedroom volume.

Another project that just recently exited the shop was a rebuild of a previously modified mid-60's Traynor YBA-1. Because the amp was modified in the past, there was little incentive to restore it to original specs. Now it's similar to a late 70's Marshall 2204 50w amp with a PPIMV - much more versatile than the original circuit.

Here are a few before and after pictures of some of these projects...

I'm always grateful to have people entrust me to restore their vintage gear like this 1969 Fender Bassman. It's pretty ...
09/17/2024

I'm always grateful to have people entrust me to restore their vintage gear like this 1969 Fender Bassman. It's pretty cool to open the amp up and have it bone stock with nothing changed since it left the factory. The original filter caps and bias board components have been upgraded with new parts but I was apparently too busy working on it to take a photo of the new filter caps.

I've made minor changes to the amp by converting the pre-amp to AB165 specs and the power amp to AA864 specs - making it the Bassman it always wanted to be but never was. A new 3-prong power cable, new tubes, and a handful of new components to replace out-of-spec parts were also installed. The tolex was peeling off in a few places, so it was glued back and given a full deep clean to make it (almost) look like it just came from the factory. It's now healthy again and ready to rattle walls and windows like it did back in 1969.

Had a Guild Starfire IV on the bench to replace the current, if not original(?), pickups. It's like a game of Operation...
09/17/2024

Had a Guild Starfire IV on the bench to replace the current, if not original(?), pickups. It's like a game of Operation to modify the electronics in hollow-body guitars but there are some tricks to make life easier. The new pickups sound great and, with a full setup, the guitar plays amazing.

Guitars! We also do some work on guitars like pickup swaps and set-ups. This Suhr Thornley JM came in to get some new ...
06/20/2024

Guitars! We also do some work on guitars like pickup swaps and set-ups. This Suhr Thornley JM came in to get some new Thornbuckers and a Suhr single coil installed. Sounds amazing.

Check out this gem! An amazingly pristine 1966 (late 1966) Fender Deluxe Reverb came to the shop for an overall amp hea...
06/20/2024

Check out this gem! An amazingly pristine 1966 (late 1966) Fender Deluxe Reverb came to the shop for an overall amp health evaluation and good once over. It contained original(?) or close to original tubes - a Telefunken GZ34 rectifier, Italian-made 6V6s and a variety of Philips, Admiral and Radiotron pre-amp tubes. When was the last time tubes were made in Canada? The amp even has the snowman 8 potentiometer k***s - IYKYN. The filter caps were non-original and a small piece of tape inside the doghouse cover indicated that the amp was re-capped in 1971.

The first order of business was to replace the two-prong power cable with a 3-prong power cable, remove the "death" cap, and re-wire the PT primary eliminating the polarity switch. New F&T filter capacitors and 3-Watt Vishay resistors replaced the old components in the doghouse. All the original, cardboard-housed cathode bypass caps were replaced with high-quality Vishay electrolytic caps. The power tube screen-grid resistors were pretty baked so new 3-watt Vishay resistors were installed and mounted off the side of the tube socket to prevent further heat damage. All the components on the bias board were replaced with new components and I also removed the 6.3 v heater center tap and replaced it with heater balance resistors.

The final step was giving the amp a good cleaning, inside and out. I removed the brass grounding plate and cleaned it and the interior of the chassis to ensure a good ground connection. The other grounds in the amp were similarly cleaned. I was concerned that some or all of the original tubes might have been past their best before date but I was wrong. ALL the original tubes worked great and the noise floor on the amp is extremely low. This amp sounds AMAZING!

Part 2 of 2: AFTERFollowing the chassis gutting, the amp was rebuilt using as many original components as possible. The...
06/20/2024

Part 2 of 2: AFTER

Following the chassis gutting, the amp was rebuilt using as many original components as possible. The point-to-point wiring has been replaced by turret boards for ease of component replacement in the future. The power supply follows that of the original ESR amp using high-quality F&T and Nichicon capacitors. As mentioned in the previous post, the amp contains two distinct channels that mix before the phase inverter. One channel is a Fender-type flavour with a tone stack bypass switch that turns the polite clean tones into Big Sugar-esque sludgy grind. The second channel is a Marshall-type offering. With only two triodes (1 - 12ax7 tube), getting into Marshall grind territory would have been difficult without employing a MOSFET cathode follower. The two triodes can do the heavy lifting in terms of distorting the signal and the transistor can lower the impedance prior to the tone stack.

I've kept the reverb and tremolo in the amp and they are only present in the Fendery channel. Because the output section of the amp is the same as a Fender Twin, a LARMAR post-phase inverter master volume was included to get overdriven sounds that won't cause the police to knock on your door.

Part 1 of 2: BEFOREIn the world of guitar amplifiers, most people would likely be familiar with brands such as Fender, M...
04/26/2024

Part 1 of 2: BEFORE

In the world of guitar amplifiers, most people would likely be familiar with brands such as Fender, Marshall, Vox. Earth Sound Research - likely not, nor was I until this beauty showed up to the shop. Earth Sound Research was a company from New York that built amps for a few years in the 1970's. The ESR Super Guitar G-2000 was one of their offerings and was basically a clone of a Fender Twin Reverb housed in a Kustom-esque tuck-and-roll vinyl clad exterior that would have looked similar to car seats of the same period.

The amp came in with crackly front panel controls, no reverb or tremolo, an original two-prong AC cable that needed replacing and a good cleaning. After taking a look inside it was clear that this amp hadn't been opened up since the day it left the manufacturer - original tubes (I'm pretty sure), capacitors with a 1973 date code and a hand-written date of December 15, 1973 that was probably added by whomever wired/inspected it prior to it leaving the factory.

Many of the electrolytic caps were bulging and all needed replacing, the screen resistors had split in half, almost all of the original components' values had drifted way beyond their spec, and the grounding throughout the amp would have created a noisy mess. After chatting with the owner of the amp, we decided to give this gem a new lease on life and completely rebuild it. Although some people liken point-to-point wiring to unicorns and rainbows, in this case, maintaining this wiring scheme in a rebuild with some circuit modifications and a better grounding scheme wouldn't have worked. The owner wanted one channel to keep the classic Fender tone and one channel to have some Marshall kerrang. As a result, the decision was made to gut the amp down to the studs and build it back up with tone, serviceability and reliability in mind. Stay tuned for part 2.

Mesa Monday - The Mesa Dual Rectifier Road King. Probably the most unnecessarily complicated amp I've ever come across....
04/23/2024

Mesa Monday - The Mesa Dual Rectifier Road King. Probably the most unnecessarily complicated amp I've ever come across. I've seen vehicle user's manuals with fewer pages than the one for this amp.
It came in with two of four channels not making any sound thanks to a few transistors that were shot.

This VVT Earthquake Overdrive came in with one burned screen grid resistor and the ceramic part both power tube sockets ...
04/20/2024

This VVT Earthquake Overdrive came in with one burned screen grid resistor and the ceramic part both power tube sockets heavily fractured - they've clearly experienced just a bit of overheating. Both tube sockets and screen resistors have been replaced, and new power tubes installed and biased. The V1 pre-amp tube was also about to give up the ghost, so that was replaced as well.

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