MOD 101 Guitar Amp Kit

File Downloads:
Instructions (997.13 KB)
Schematic (141.28 KB)
Part List Drawings (322.73 KB)
Soldering Tips (33.93 KB)
Sound Sample (3.19 MB)

Click here for a list of frequently asked questions for the Mod 101 Guitar Amp Kit. 60 watt vacuum tube amp kit. The MOD 101 Amp Kit measures 8 1/8" in height, 19" in width (including handles), chassis width is 16", depth is 8". Overall weight of assembled amp kit is 23.7 lbs. Comes with complete instructions for putting together kit as well as detailing 32 circuit variations including: Tone Stack Mod, Input Voltage Divider Mod, Negative Feedback Mod, Bypass Cap Mod & Power Tube Mod.

MOD 101 Guitar Amp Kit Features

  • All Tube Design (solid-state diodes used only for full-wave rectification)
  • 60W output power into 4, 8, 16 and 20 Ω
  • 1 channel with customizable: tone stack, power tubes, negative feedback, input miller capacitance volt divider/LP filter, and preamp cathode bypass cap (all parts included)
  • Vintage channel controls: bass, treble and volume
  • Vintage pilot lamp and screw-on jewel cover for power-on indication
  • DPDT power switch circuit for instant high-voltage drain in power-off
  • Standby Switch
  • Output Impedance Selector Switch: 4, 8, 16 and 20 Ω
  • Tubes included: one 12AX7 (preamp), one 12AT7 (phase inverter), one matched pair of 6L6GCs and one matched pair of EL34s (JJ Electronic brand)
  • Hammond Mfg 374BX world power transformer and 1650P push-pull output transformer
  • Fixed bias class AB power tube operation with bias pot adjustment
  • Point to point hand wiring using terminal strips
  • Carbon film resistors
  • Mallory coupling caps
  • Pre-punched painted steel chassis
  • Assembled Kit Weight: 24 lbs.
  • Assembled Kit Dimensions: 16" Width x 8" Depth x 8 1/8" Height

MOD 101 Instructional Features:

  • Detailed, easy to follow instructions include high resolution computer drawings for parts list and every step of assembly
  • Tips for soldering and wiring
  • On-line technical support

Here is what people are saying about MOD 101 Guitar Amp Kit

"This kit was my first amp build. I had fun and learned a lot while putting it together. Now I have a great time gigging with it!" "This is a nice amp. The kit was fun to build and the instructions were great!" "I've been wanting to learn to to build my own tube amp for a long time but had no idea where to start. The MOD 101 has been my gateway to DIY amp building."

Sound Sample01:23

Frequently Asked Questions:

What tools do I need for the MOD 101 guitar amp kit?

You will need the following tools:

  • Wire Strippers
  • Needle Nose Pliers
  • Cutting Pliers
  • Desoldering Pump
  • Solder (60/40 rosin core)
  • Soldering Station
  • Phillips Head Screwdrivers
  • Slotted tip screwdrivers (3mm tip)
  • Digital Multimeter (DMM)
  • Alligator Clip Test Leads (to fit DMM)
  • Channellock Pliers (or similar type)
  • Miniature Round File (fine cut)
I live in the UK, does the power transformer for the Mod 101 work for 220V, 50Hz?

This amp kit uses a Hammond Manufacturing "300" Series world power transformer. It can be wired for the various voltages used around the world.While the instructions are only written for United States wiring (120V, 60Hz), you may be able to figure out the wiring for your country.

Do you recommend the product called a "yellow jacket" that installs in the tube base, allowing for interchanging of the tubes in the Mod 101?

The Yellow Jackets YJS (normal or triode) model is the correct tube adapter to use with the MOD 101. Using Yellow Jackets in your MOD 101 will allow you to use EL84 power tubes in place of the 6L6GCs or EL34s. They will also reduce the maximum output power from 60 watts to between 18 and 30 watts (YJS normal) and to between 6 and 18 watts (YJS triode).Because Yellow Jackets convert the power stage to Class A auto-bias configuration, you do not need to change the amp\'s bias pot when using the Yellow Jackets.

What is the difference in sound between using 6L6GC or EL34 Power Tubes?

Generally, the EL34s will allow for a little easier breakup than the 6L6GCs and they will have a tighter more straight-forward low and mid body. Of course, each power tube brand and type will bring its own personality to the mix. We highly recommend trying different brands and types of tubes to find your favorite.

Why did you design the Mod 101 amp to be able to get so loud?

The 60 watts of power output can really come in handy when playing in a large impromptu jam session or at a gig with limited PA capabilities. But at low volume or with the use of a power attenuator, the amp will still sound excellent at levels that will not drive your neighbors crazy.

Why are there no internal effects or channel switching features in the Mod 101?

The amp was designed to be basic and classic allowing for warm clean tone at low volume and transitioning gradually into rich power tube overdrive distortion at higher volume, while encouraging the builder to experiment with basic circuit variations to find their preferred tone. Many amp builders and guitar players have found that the quality of tone is degraded more and more with the addition of internal effects and channel switching. (Also, more effects and more tubes make the amp more of a workout to carry around.)

What kind of chassis comes with the Mod 101?

The kit comes with a black powder coated steel chassis which is pre-punched. Because the steel is punched before being coated, you will need to file away the coating around the holes to allow for conductivity between connections made to chassis ground. (This is a step included in the instructions).

What brand of transformers does the Mod 101 use?

The kit comes with Hammond Transformers 374BX and 1650P.

Is there an FX loop in the Mod 101?

There is no FX loop, but the amp sounds great with effects pedals.

What is the output impedance of the Mod 101?

The kit comes with a rotary impedance switch allowing you to change the output impedance to 4, 8, 16, or 20 ohms. This gives you the flexibility to use different speaker configurations and not waste output power or damage the amp.

How is the Mod 101 biased?

The power amp is fixed biased for Class AB operation with an adjustable bias pot. (The instructions will guide you through setting the bias for both 6L6GC and EL34 power tubes).

Are all the parts provided for the 32 different circuit variations in the Mod 101?

Yes, all the parts are included for the different circuit variations.

Does the Mod 101 have a tube or solid-state rectifier circuit?

The Mod 101 has a solid-state rectifier.

Is there an explanation somewhere detailing the 32 circuit variations of the Mod 101and what they do?

Yes, the last section of the instructions gives details on the modifications which can be implemented by using the included extra components. The following is a list of the modifications:

  • Tone Stack Mod
  • Input Voltage Divider Mod
  • Negative Feedback Mod
  • Bypass Cap Mod
  • Power Tube Mod
In the Mod 101, is it possible to change between the matched pairs of EL34 and 6L6GC power tubes without having to de-solder or change out any other components?

Yes, if you follow the EL34 set up initially, then you can switch to 6L6GC tubes without changing any other components. It\'s always a good idea to check the bias when changing power tubes. (The bias can be checked and adjusted with just the steel cage removed and using a volt meter - the instructions will explain this process.)

Can the Mod 101 be modified for cathode biasing instead of fixed?

No, the instructions do not explain a modification for changing the power tubes from fixed bias to cathode bias.

Can other preamp tubes be used in the Mod 101?

Yes, other preamp tubes may be used in place of the 12AX7 in position V1. (For example: ECC803, 12AT7 and 12AU7).

Can the Mod 101 be built with a tube rectifier? If so do you provide instructions?

No, the instructions do not explain a modification for changing from full wave solid state rectification to tube rectification. (Although, the Hammond 374BX power transformer does come with an extra secondary winding not used in the kit).

Can the Mod 101 use other power tubes other than 6L6GCs and EL34s?

Yes, you can use the following power tubes which are substitutes for 6L6GCs and EL34s

  • 6L6GC substitutions: 5881 and KT66
  • EL34/6CA7 substitutions: KT88 and KT77
My pilot light does not turn on, what could be causing this?

Check the fuse. It has probably blown do to excessive current draw. A blown fuse measures as an open circuit from end to end and usually happens when something else in the circuit is wrong. The fuse is a protective device, so if your fuse has blown, check your work to see what may have gone wrong.

What does it mean if I'm hearing a very loud low frequency hum when I turn my Mod 101 on?

A low 60 Hz hum can be the result of:

1)The power transformer\'s filament winding center tap (TR1 green/yellow wire) has come loose.
-Check to make sure this wire is connected properly and not just hanging on by a cold solder joint.

2)You may have a faulty tube in V1. Sometimes a bad preamp tube will amplify the filament's AC frequency.
-Remove the tube in V1 (ECC83) to see if the hum goes away.

Is it possible to add a master volume control to the MOD 101?

Yes. The parts are not included with the kit, but we have provided a schematic and layout drawing for how to add a "post phase-inverter master volume" (PPIMV) control in the MOD 101 "File Downloads" section. Mod 101 PPI-Master Volume Mod Instructions

My MOD 101 still has some sound with volume at "0" and with all controls at "10" it's motor-boating. Is there a fix for this?

Yes. This is most likely due to the shared cathode of the V1 preamp tube. The parts are not included with the kit, but you can easily split up the cathodes by using the instructions provided in the MOD 101 "File Downloads" section. Mod 101 Shared Cathode Split Mod


A Demonstration of Amp and Effects kits from MOD Kits