Vintage Amp Repair

Introducing...
The Open-Design Guitar Amplifer
Change your amp's design and components with only a screwdriver!

The Open-Design Amp is made to be changed!

The whole amp, from preamp to output section, is built on the top of an old-fashioned "breadboard." This board has the whole amp on it, including the gain and tone controls, the phase inverter and output sections, and they can all be changed to the values you want to try.
The amp comes completely built, and has drawings with it that detail the construction to the point that you can rebuild the amp back into its original configuration.

Configured as a classic generic 15 Watt push-pull guitar amp, this design can be changed to values that represent other famous and classic amp designs. The included drawings name the function of each component, so you can easily change the "slope resistor," for instance, without struggling to find it.
The amp is provided in a push-pull "fixed-bias" configuration that can be easily changed to self-biased (also known as cathode bias) mode. It can also be made single-ended.
The target price for the Open-Design Amp is about $475.

It comes in a nice wood box that lifts up for changes, which also disables the high voltage. When closed, it looks like a custom guitar amp, and the amp is ready for operation. Volume and tone controls are in the front.

Caution! This design, while having safeguards to prevent shock, can still be dangerous.
There is almost 500 Volts on the power supply, and that is enough to kill you!

The Hush Puppy Tube Module

Now available as a Kit!

Quiets your amp – what a treat!

The Hush Puppy Tube Module is a replacement for the output tubes of your guitar amplifier to quiet it down. It is a drop-in replacement for most common output tubes.
According to folklore, a “hush puppy” was a tidbit given to dogs during cookouts after the hunt to quiet them down.

The normal 50 watts of power furnished by a pair of 6L6's is way too much for studio or small-room use. It is also hard to mic an amp when it is at full volume!

Without any changes to your amp, these modules reduce the power down to about 3 watts, and they sound good... perhaps better than your favorite 6L6, EL34, or 6V6.
Sound Samples:
(Note - I noticed the MP3 conversion resulted in a distortion-like fuzz that was not there in the original recording.)
Adam Burchfield On Guitar - short boogie with Hush Puppy
Adam Burchfield short rhythm with Hush Puppy
On these samples, which were done on a Fender Blues DeVille, I progressively increased the input volume until I hit the max. You can hear how it goes from clean to quite dirty and compressed.
Tommy Luna playing bass riffs with Hush Puppy, also done with increasing volume until max. It really changes the sound as you push it.
Musicians courtesy of Rockin' Robin Guitars in Houston, Texas.

There is no need to use a volume reducer your amp. Most of those add their own coloration to the sound anyway.

The Hush Puppy uses a smaller tube than your original tube. It is also self-biased, and does not require resetting the bias in your amp. It creates its own environment independent of the normal output circuit. This creates the potential for great sound.

Most tube amps start sounding good only above 7 or so. That is normally where that unique tube compression and distortion happens. Your amp sounds so good at those levels only because the tubes are near their limit of current capacity. Too long like that, and your whole amp (and your hearing) could suffer.

The tubes in the Hush Puppy Module are working just as hard in proportion as the larger tubes, and they sound like it. But they are only drawing a few milliamps, one tenth or so of what two 6L6's would draw.

The Hush Puppy module currently comes in two forms: Model 2, which is switchable; and Model 1, which the same as the middle setting of Model 2 but is not switchable.
The Model 2 settings are called "quiet pup," "nice dog," and "bad dog."
"Bad dog" is purposely distorted by raising the current draw. It is similar to the practice of biasing an output tube "hot."

They are compatible with all varieties of:
5881, 6550, 6K6, 6L6, 6V6, KT66, KT77, KT88, STR387, STR415, EL34, 6CA7, CV1741.
(with varieties being 6L6, -G, -GA, -GB, -GC, -GT, -WGA, -WXT+, etc.)

The Hush Puppy is supplied with the proper tube. It can use a 12AT7, 12AX7, 12AU7. It is truly a simple installation.

Buy them online! Click below to order one or more Hush Puppy Modules.
More info? Email me with the subject: Hush Puppy, at

The Hush Puppy Module is now available in KIT form. It isn't really hard to assemble, but it takes a while. Included are the directions with diagrams, a small circuit board, all the components, sockets, plugs, wire, and the housing.
Not included is the 5-minute epoxy to secure the unit together and fine wire cutters. These can be obtained at almost any craft store, hardware or department store.
There is detailed soldering, wire stripping and wire cutting. This is not a project for beginners, as if it is not built according to instructions, it will probably not fit in the housing!

Pricing and Purchasing: (Prices are for a single unit)
Model 1 Kit $25.00
Model 1 assembled $40.00
Model 2.1 Kit $32.00
Model 2.1 assembled $65.00

Choose your product

Hush Puppy Modules

I repair vintage and classic tube amps in Houston, Texas.

I am centrally located in the Museum District, Southwest of Downtown.
We have a waiting list, but it is to your advantage. Rather than having your amp sitting in the shop while we get around to repairing it, we ask that you put your name on our list. When your name comes up on the list, we will contact you, and you can bring your amp in to the shop. Then we will only have it a few days, instead of weeks or months.
Same-day repair is available if needed and if possible. Priority is given to working musicians or others with a need to get their amp back in a hurry.
I have a good parts-supply chain if I need to order something, but I have many parts in stock already.
My prices are low compared to many long-lead-time shops:
Thorough Examination with Accurate Estimate: $65
Minor Repair: $85 (fuses, adjustments, cleaning, simple component replacement), parts extra.
Most often: $115 (multiple component replacements + cleaning + adjustment + functional test), parts extra.
I can rebuild, re-cap, and restore your amp into whatever shape you want it to be.
I NEVER put in parts that you don't need, unless it is part of the diagnostic process.
Mods: If you don't like the way your amp sounds, we can discuss what mods would help it.

"Amp Repair Guy."

I am now creating custom amps.
These are amps that I have done:

The R.R. Special Guitar Amplifier
- This amp is an all-tube, one-input design, with two internal channels. The Normal channel is used all the time and can be run clean or dirty, depending on your settings. The Overdrive channel is mixed with the Normal channel via the Mix control, into the Master Volume control.
- This amplifier design uses dual outputs: standard 6L6's or the Hush Puppy outputs, so that the output power is selectable as either 45 Watts or 4 Watts. It can be switched on the fly, during play in fact.
- The Effects Loop Output is buffered and the level is adjustable. The Effects Loop Input goes right to the Master Volume Control input.
- The power supply is selectable for either a solid state diode or a tube rectifier. The Diode give more power, but the Tube gives more personality, and the amp responds more to your playing.
- There is a Feedback control that controls linearity. Completely off, and the amp can get real dirty. Turn it up, and errors (distortion) in the output are corrected, and the amp becomes more linear.
- The Ultralinear switch cuts in the Ultralinear windings on the output transformer, creating even more linearity.
- Bias for the 6L6's is switchable to self-bias (Class A-like), or adjustable bias. Bias is adjustable from the front panel, and is limited to extremes of Cold and Hot. The Hot setting would break up sooner.
- The Harmonic switch purposely unbalances the Phase Inverter to create even harmonics safely.

The Mr. J. Guitar Amplifier
The goal with this design was a Hendrix-like sound with plenty of gain and overdrive distortion. Power is from two 6V6's, with switchable Hush Puppies to reduce power. A reverb adds a nice dimension, and effects-box loop makes it expandable.
The owner will pick it up soon.
More shots: Those are Gold Plated jacks...

Contact me with your requirements and ideas, and I'll work up a quote.

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