Allen Amplification Chihuahua Amplifier Review



Here's some pictures, sound files and comments on my new Allen Chihuahua tube amp kit. I ordered it with the 10" Eminence Copperhead Speaker. I built this as a kit and I'll leave out a lot of comments and details that apply and are quite well covered in my Allen Encore Amp review:

My Allen Encore Amp Review

This will primarily be a home practice amp and I ordered it as a class A single 6V6 6 watt RMS amp in the same finish as my Encore. It has all tube spring reverb and preamp stages but uses a full wave filtered power supply instead of a tube rectifier. I decided to record three full tunes with this amp as well as samples with pedal steel, archtop jazz guitar, electric mandolin, telecaster, nylon string guitar and fiddle all of which are linked to below.

Some useful links:




Two full song recordings with real bass, rhythm guitar, EZKeys piano, EZDrummer drums. All pedal steel, mandolin, rhythm and lead and guitar parts are played through the Allen Chihuahua amp.
Click here to listen to Class A Dawg
Click here to listen to I Won't Mention It Again


Review Summary

Like the Encore this amp is dead quiet with almost undetectable hiss or white noise. Also like the Encore, it's a cinch to dial in any desired level of cleanness or distortion by cranking back on the Master Volume control, increasing the Raw control and adjusting the input Volume control. It has a bit less gain than the Encore but plenty of gain to achieve great dynamics. With a typical guitar pickup you can easily drive the amp to full power with no additional preamps or active electronics. See the picture below under bench testing that shows the ability to achieve really cool distortion at only 1/8 watt of output power!

In keeping with the vintage tube sound I used my Goodrich pot pedal and no stomp boxes on all the recordings. The amp's reverb is a lot like the classic Fender tube reverbs when they sounded good years ago but with maybe a hint more of a hall reverb sound to it. Not at all tinny or metallic sounding. This amp's reverb equals and even improves the reverb of the best vintage Princeton's I've owned. All of the recordings on this page use the amp reverb. The amp at about 4.2 watts RMS output is still LOUD in a small room or practice venue. It does have a TON of gain which makes volume pedal dynamics and expressions easy.

Obviously the sounds presented here don't show the effects of the speaker after break in. As well, the amp placement, speaker, cords, efffects, guitar and many other things will have a huge effect on the tone of the amp. In fact I placed the amp on the floor and the bass response went through the roof. This is truly a turbo-charged Champ style amp and great for recording, practice or miked on a gig. Pair it with a big 12" or 15" speaker and you can get a wall of sound if desired.

The speaker weighs 4.5 pounds, the chassis weighs 8.1 pounds and the cabinet with reverb tank weighs 11.2 pounds. For comparison here are the relative weights of some popular amps:

Fender 68 Custom Deluxe Reverb 40.2 pounds
Fender Steel King with casters 64.4 pounds
Peavey Nashville 400 57.0 pounds
Allen Encore 43.7 pounds
Allen Chihuahua 23.8 pounds





Sound Samples



Here's some sound samples. All pedal steel samples use the Goodrich volume pedal with a Dunlop Hotpotz, 12' of George L's cable between the amp and volume pedal to roll the highs off a bit, Allen Chihuahua amp with a Shure SM-57 mic, onto a Zoom R24 recorder then ported to Reaper to convert them to mp3 files at 320 kbps. Guitar samples omit the Goodrich foot volume. No reverb or EQ is added by Reaper. The samples are very raw and close to what I hear sitting next to the amp. My initial amp settings (subject to change):
  • Volume = 5.0 (varies a bit)
  • Treble = 4.0 (lower for steel, higher for tele)
  • Bass = 1.0
  • Raw = 1.5 (except for distortion sounds)
  • Reverb = 6.5
  • Master = 10.0 (except for distortion sounds)


Selection
Recording Method
 		Comments
Shure SM57
 Pedal Steel - E9th - Sample 1
Shure SM57
 Pedal Steel - E9th - Sample 2
Shure SM57
 Pedal Steel - E9th - Sample 3
Shure SM57
 Electic Mandolin Sample 1 (4 string with low C)
Shure SM57
 Electic Mandolin Sample 2 (4 string with low C)
Shure SM57
 Epiphone Joe Pass Archtop Electric Sample 1
Shure SM57
 Epiphone Joe Pass Archtop Electric Sample 2
Shure SM57
 Fender Nashville Tele Sample 1
Shure SM57
 Fender Nashville Tele Sample 2
Shure SM57
 Godin Nylon Electric Sample 1
Shure SM57
 Godin Nylon Electric Sample 2
Shure SM57
 NS Electric Fiddle
Shure SM57
 Pedal Steel Distortion (Raw and Volume controls cranked, Master set low)
Shure SM57
 Tele Distortion (Raw and Volume controls cranked, Master set low)



Bench Testing and Accessories

A 20 amp variac was used to adjust the input voltage to 120 VAC just for uniformity and because my house line voltage can run pretty low. The 20 amp variac is overkill but it's built more ruggedly than the lower amperage rated units. For a dummy load I used the Weber TRU-LOAD DUMMY LOAD with a mod to switch out the unit's internal speaker motor allowing for a more resistive load. This keeps the load voltage and current in phase eliminating power factor considerations which simplifies power calculations.

  • Weber TRU-LOAD DUMMY LOAD

    Here's a schematic I traced out showing the added switch (click on picture for full size pdf file):

    For bench testing I used an audio signal generator, 200 MHZ digital scope, variac set at 120 VAC with the amp impedance switch set at 8 ohms and the dummy load set at 8 ohms. A tube amp will deliver maximum power to it's load when the load matches the amp's internal impedance. A lower or higher load will result in a lower power output to the load but can result in useful damping transient and tone changes in actual use. Note that a 3 db increase in audio level only yields a slight increase in audible volume but requires twice the power! Similarly a 6 db increase requires 4 times the power and a 10 db increase requires 10 times the power but will sound twice as loud. Nevertheless, amps are heavily marketed based on wattage and it's hard to convince buyers that whether an amp is 6 watts or even 10 watts really doesn't much matter in terms of sound levels. For my setup I used a sub $100 audio generator and it's pretty amazing. You can see the waveform purity immediately below and pictures of the setup far below. The scope has a somewhat useful FFT (Fast Fourier Transform) function that shows a decent frequency domain representation of the signal. What is REALLY cool about the scope is that it calculates the RMS value of the waveform allowing for accurate output power calculations of various waveforms. A square wave will have a lot higher power output than a sine wave at the same frequency. Thus, as the amp starts to get pushed out of it's linear region , you can get more than 4 watts of RMS power out of it.

    Input signal:

    The first picture below shows the amp delivering a fairly clean 4.36 watts with a 306 mV peak to peak input signal at 1 khz. The 6V6 plate voltage is at 373 volts, screen grid 282 volts, cathose at 17.57, plate current is xxx ma and the tube is dissipating about 12 watts.. Most passive pickups that I've seen put out between 90 and 400 mV. The picture just below it is the same sort of setup with the FFT and output signal on a split screen.

    Here's the amp delivering 3.14 watts into a 16 ohm load.

    The next picture shows the amp delivering 1/8 watt with the RAW control cranked up a bit (overloading the input stages).

    The next picture shows the amp delivering 6.59 watts while producing a distorted signal by overloading the output stage.

    Note that the amp is capable of producing two different sources and sounds of distortion. You can overdrive the output section or you can overdrive the preamp section depending on how you set the master Volume and Volume/Raw controls.




    There are quite a few pictures below. Click on them to see them full size or at least sized to a browser window. Click on the picture again if needed to zoom in even more!







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