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HB-1 "Hot Box 1" Guitar

2U Rack Mount Preamp


Model No. HB-1-RM
Series: Rack Mount Chassis Guitar & Bass Preamp    

MSRP: $665.00



HB-1 "Hot Box 1"  Guitar Preamp


Model No. HB-1
Series: Open Chassis Guitar & Bass Preamp 

MSRP: $575.00





The FRENZEL HB-1 "Hot Box 1" dual channel guitar/bass tube preamp is part of our "INSPIRED" line of products and  will give you the classic vintage tones of the Hot Box preamp a lot more.  As with all of our "INSPIRED" line of products, this preamp  is designed to give you  the vintage 50's-60's amps  "TONES YOU KNOW"...but it's far from simply a clone...the HB-1 preamp incorporates features and mods developed over FRENZEL Tube Amps 65 plus years of building and fine tuning it has the upgrade option to add a 1 watt power amp for low volume practice sessions. 

I am sure all  you guitar guys know about the vintage Matchless Hot Box, and what a great tube effects pedal it was, so I won't go into a history of it...but I will tell you a little about the original Hot Box circuitry. The original  Hot Box had two channels...CLEAN and BOOST  that used two 12AX7's. They were wired so that, in the CLEAN mode, you had one stage of gain, with a Gain control and a bright capacitor and some other audio filtering that made the tones  sparkle. You did everything else with your guitar controls. For the BOOST stage you had three stages of gain with circuitry very similar to the vintage Marshall preamps. The BOOST channel had Gain and Master level controls  that drove a cathode follower which fed a two band tone stack. All in all a really ace combination....but  despite it's excellence, it had a few problems and we have endeavored to correct them by listening to  suggestions made by our "rock on" guitar friends.


The first change was to replace the two band tone stack in the BOOST channel with a 3 band type tone stack similar to the one was used on the JTM 45. This stack  allows you to create a much wider range of fantastic overdrive tones. We also changed the CLEAN/BOOST channel switching circuit to use a sealed ultra low noise relay to eliminate switching noises and loud pops. Another problem with the original Hot Box was that they all had a lot of 60 cycle hum. We have corrected this by using DC on the filaments and shielded wire on all the high gain audio circuits. In the CLEAN amp section  we installed a BRIGHT pull switch on the Clean Gain control. This simple change gives you a much larger range of tones. Also, a second pushbutton was added to the footswitch to allow you to completely bypass the Hot Box. This gives the player three options.....BYPASS, CLEAN, and BOOST. Regarding the footswitch, we also added LED's so that you know which mode you are in. This was requested by lots of performing artists.


Additional features include a standard IEC plug-in 3 prong ground power cord and all point-to-point hand-wiring. The controls are Input, Clean Gain with Bright Switch, Boost Gain with Boost Switch, Boost Bass, Boost Mid, Boost Treble, Boost Master, Power LED, and Power On/Off. The rear panel has a 1/4" footswitch jack,  1/4" Output jack, Output Level control, and power line fuse.  The tube line up is 2 -12AX7's.

If you have never played through a Hot Box... you are in for a real treat. If you have, you are still in for a trip, because of the new features that have been added.  It makes any tube amp sound better...and for you guys with solid state amps who are craving that vintage tube sound, you can insert it in front of your solid state amp and get that classic Fender, Marshall, or Vox preamp tube overdrive distortion tones.

The preamp is built on a 10" x 6" x 2" chassis. It is constructed with all new top of the line parts....Neutril jacks, JJ 12AX7's, Micalex tube sockets, polypropylene caps, metal film resistors... etc.  It comes with a two button Marshall style footswitch. 

Standard Features:

  • Input Jacks isolated from chassis to eliminate eddy currents and hum.

  • DC on filaments to eliminate 60 hz hum.

  • Star ground system to eliminate induced current chassis noise.

  • Clean and Boost foot switchable inputs with separate preamps and Gain controls for the unique clean smooth  warm blues tones or the  dynamic boost lead  tones.

  • Classic  VOX  style 3-BAND TONE STACK with mid-scoop for extended flexibility in shaping your tone.

  • Bright Pull-Switch on Gain controls

  • Deep Switch on Bass control.

  • MASTER level control on the Boost channel so you can crank the GAIN up and overdrive the preamp without overdriving the output tube.

  • Dual Button Footswitch Pedal  With LED's- Button 1 select Clean or Boost Channel  - Button 2 select Preamp Active or Bypass Preamp

  • Preamp tubes are JJ 12AX7's known for low noise and linearity. You may also use 12AT7's or 12AU7's for different tones and less preamp overdrive.

  • Classic Knobs and Toggle Power Switch

  • Standard IEC plug-in three prong grounded power cord. 

  • Rock solid point-to-point hand wiring using only the best of parts...low noise tubular polypropylenes caps, metal film resistors, Micalex sockets, Neutrik  jacks...etc.

  • Sweet vintage clean to classic overdrive tones with three different types of  distortion depending on whether you are overdriving the preamp, output... or both! 

  • Electrical Specifications: 

  • Input Impedance:  1 megohm

  • Level:  Instrument Level (100 millivolts RMS)

  • Output Impedance:  10K ohm

  • Output Level:  Line Level (1.5 volts RMS) 

Physical Data: 

  • 2U Rack Mount Chassis - Overall Dimensions(19"W x 12"D x 3.5"H)  or Open Chassis - Overall Dimensions(10"W x 6"D x 3.5"H)

  • Weight - 9 lbs. 

  • Chassis - Heavy gauge aluminum with welded corners.

  • Retro Vintage Cage Mini Head Upgrade  - heavy duty lightweight steel mesh cage provides protection and excellent ventilation for tubes. Comes with easy carry Fender style strap handle. Overall Dimensions - 10" Wide x 6" Deep x 7" High

  •  Rock solid point-to-point hand wiring with military style tie-wrapped wiring harnesses for long life and reliability.

  • DC on filaments to eliminate 60 hz hum.

  • Star ground system to eliminate induced current chassis noise.

  • Input and Output Jacks isolated from chassis for low noise, eddy currents, and hum.

  • Classic Vintage Fender Control Knobs

  • Components - Only the highest quality parts are used including heavy duty transformers, low noise tubular polypropylenes capacitors, metal film resistors, Micalex sockets, Neutrik jacks. All parts are rated for commercial high use conditions. Wherever possible we use parts made in the USA.

  • Front Panel Controls - Clean Input Jack, Boost Input Jack, Clean Gain/Bright Pull Switch, Boost Gain/Bright Pull Switch, Bass/Deep Pull Switch, Middle, Treble, Master, Pilot Lamp, On-Off Power Switch

  • Rear Panel Controls -  Power Cord Connector, Fuse,  Output Level, Output Jack, 

Upgrade Options:

These options allow you to  customize your amp to meet your special individual requirements.

RETRO CAGE COVER  -  Ventilated cage cover for open chassis model provides protection for tubes and excellent ventilation. Add $95.00


230-240 VOLT POWER TRANSFORMER - for operation outside the USA where 230-240VAC line voltage is used. Add $75.00


"I will never be able to play without this preamp in my life, its the best thing that had happened to me since I played guitar for the first time, nothing comes close to the quality of what you have built... it sounds like heaven. Nothing else to say." Thank you Jim, you are building a legacy.  Cesar L. (Guatemala)  


Hello Frenzel Team,  I love the Hot Box preamp I just purchased.  You guys are great, and make the best tube gear. Thank you,Will K. (Oregon)

"the unit works beautifully and sounds terrific. I only started playing with the different settings - and then played with it splitting the signal between the Blues Junior amp with the HB1 and the piezo output to a Crate acoustic amp. Amazing to have the warm overtones accompanied by the clean acoustic sounds." Thank you very much! Scott B. (Maryland)

Hello Frenzal, I finally had time to sit down with the HB-1 preamp. I received the preamp back in February 2018. I actually tried it out when I first got it but didn't think it was for me. Man was I wrong. First let me explain my background in music a little bit. I first picked up a guitar at 18 years of age...I'm 44 now and play it every night. About two weeks ago...I connected the HB-1 for one more try. I was blown away. I guess I was impatient the first go around. But I took my time on it this time. I believe, no I know that your HB-1 tube preamp gives my solid state Fender and Orange amps super powers. Thank you every one at Frenzel for such an outstanding preamp. Thanks to y'all I'm sold on tubes and on Frenzel!!!  Ron P. (Virginia) 

Hello Frenzel Team, Having a blast with my Frenzel Champ Super Sportster amp and Hot Box ! preamp. Couldn't be happier with my purchase. You guys are terrific. The value of the amps you sell is second to none. I own a 1953 Tweed Fender Princeton and it just cannot hold a candle to my Super Sportster. Yes, that's right. My modern amp (loaded with NOS tubes), built by you, actually sounds better, has better tone, and is far more versatile, than my vintage amp. That is no exaggeration. It's just fact. With the HB-1 Hot Box patched into the Super Sportster I now have a 4-channel monster amp. Every place I play, every gig I play, I'm always quizzed about my "Little" amps. It's amazing how many guitarists just find it very difficult to believe that I'm playing through an amp they themselves could purchase for $600 to $700, and just over $1K with the preamp. I have so many musicians ask me about my amps that I've had to print up little cards with you email address on them to hand out because otherwise I would be spending way too much time after any gig just writing out the info on where they can get one for themselves. I've stopped taking the bottom off the Super Sportster to prove to my fellow musicians that it is indeed point to point wired. I've even stopped bringing it up. No one believes me. For Blues, Classic Rock, and Country Rock ... Frenzel Amps rule!!!  Will Kenworthy (Oregon)

I love the HB-1 preamp! I use the clean channel as an always-on preamp with my TC Electronics G-system (in the insert loop) and going into a Quilter Power Block head (set to line level input). It adds depth and sparkle and is the foundation of my sound. I use the G-System to switch the HB-1 to overdrive  for leads and a creamy distortion. Great product and superb value!  - Mike F. (California)

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