FM-DP1 "Deluxe Plexi 1" Preamp

FM-RDP5A3 "Retro Deluxe Plexi 5A3" Preamp

FM-DP2S "Deluxe Plexi 2" Stereo Preamp

FM-800Z "Rocker 800" Stereo Preamp

HB-1 "Hot Box Preamp"
FM-800Z "Rocker 800" Stereo Preamp





Open Chassis

Retro Mini-Head

2U Rack Mount

 Rocker 800
Stereo Preamp

Model No. FM-800Z 
Series: Preamp

"The Ultimate Stereo Tube Preamp" 

Open Chassis................$395.00  

25% Off Sale Price - $295.00


Retro Cage....................Add $100.00  $75.00
2U Rack Mount.............
Add $195.00  $150.00  



The  FRENZEL FM-800Z  "Rocker 800" dual channel  stereo guitar tube preamp is part of our "INSPIRED" line of products and  will give you the classic vintage tones of our Type F(Fender)  and Type M (Marshall)  tube amps ....and much more. Those of you who follow us on Facebook know that we sell retro conversion and vintage amps with of our Type F and Type M custom vintage tube preamp circuits. A lot of our customers use the Line Out jacks on these amps to drive other amps and they have asked us to build them custom we decided to add stand alone tube preamps to our product line. You can use these preamps to drive your solid state amps to generate the classic 60's vintage tube tones. The FRENZEL FM - 800Z preamp was inspired by the vintage Bassman and JCM800 amps ...but it's far more than a clone....this preamp incorporates features and mods developed over FRENZEL Tube Amps years of building and fine tuning amps! 

The preamp uses  12AX7's to create two separate preamps each with its own Input Jack, Gain control, Tone Stack and Master control, Output jack and Level control. The output driver uses a 12AU7 low impedance cathode follower circuit. The are three output for each channel and a Mono jack that combines the signals of both channels into one output.  Each output jack has a Level control to match the output level of the preamp to the input level requirements of the amp you are using.
The The F section preamp  is voiced like the classic 5F6A Bassman.  The M section  is voiced like the classic JCM800. The three band tone stacks were modeled after the original Fender and Marshall stacks and we added a Master volume after the tone stack.  With the combination of the separate Gain control, tone stack and  Master control you can get just about any sound you ever dreamed of.....including great clean tones of the Bassman...or that fantastic tube preamp overdrive distortion that the Marshall JCM800 amp is famous for.  We also provide options to change the voices of either channel.

The preamp is a point-to-point hand wired pure tube preamp amp that uses only the best of parts...low noise tubular polypropylenes caps, metal film resistors, Neutrik jacks, Micalex long life sockets, etc. The input jacks are isolated from chassis and it uses a star ground system and DC on the filaments for very low noise.

The front panel controls are (Type F) Input 1, (Type M) Input 2, Gain with pull Bright switch, Bass with Deep switch, Middle, Treble, Master, Power  with LED pilot lamp. The  output jacks, level controls,  power fuse and power connector are on the rear panel.
The input  is high impedance. and the output is low impedance. This allows the preamp to work as an effects amp between your guitar and the high impedance input jack of your amp....or in your amp's line level  effects loop. If  you have never played through a tube are in for a real treat. If you have, you are still in for a trip, because of the combination of Type F smooth warm tones and Type M high-mid overdrive tones and other extras that have been added.  It makes just about 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 vintage  custom sound of your own. It works great with guitar, bass and harp. 

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.

Type F (Fender) and Type M (Marshall) inputs with separate preamps and Gain controls for the unique smooth Fender 5F6 warm tones or the Marshall JCM800 great high mid  tones....or you can use an AB-Y switch and create your own distinct tones.

Classic 60's JTM45 - Bassman 5F6 style 3-BAND TONE STACK for extended flexibility in shaping your tone.

Deep Pull-Switch on Bass

Bright Pull-Switch on F and M Gain

Stereo Output Jacks with Stereo/Mono jack that connects jacks together for Mono operation

MASTER level control on Boost channel so you can  overdrive the preamp without overdriving the output tube.

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! 

Choice of Cabinets: 2U Rack Mount (19"W x 12"D x 3.5"H)   Retro Mini-Head  (10"W x 6"D x 7.5"H) or Open Chassis




        POWER CORD



- Input Impedance:  1 megohm
- Input Level:  Instrument Level (100 millivolts RMS)
- Output Impedance:  10K ohm
- Output Level:  Line Level (1.5 volts RMS) 

Upgrade Options

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

1. 100 - 240 VOLT  POWER TRANSFORMER - for operation outside the USA. Please specify line voltage. Add $40.00 
2. ONE WATT POWER AMP - Add a power amp using a 12AT7 as a Class A output stage which will deliver F and M crystal clear cleans or great overdrive tones at 1 watt of power into an 8 ohm speaker. This allows you to use the FM-800Z as a low power practice amp as well as a preamp. Monaural Option: Both channels are Y'ed into one power amp.  With this option one speaker jack is added to the rear panel. Add $90.00  Stereo Option: Each channel is fed into a separate power amp.  With this option two speaker jacks are added to the rear panel. Add $180.00.

3.  CUSTOM PREAMP VOICES - We can provide custom preamp voices for each input including the Fender Tweed and Blackface models, Marshall Plexi, VOX, Hot Box, and Hiwatt. Specify the voices you want on the Order Form in the Upgrades section. There is no extra charge for this upgrade. 

4. DUAL PLEXI - JCM800 PREAMP - Extra gain stage added with pull-switch on M Gain control to select between Plexi  low gain or JCM800 high gain.  Add $60.00


From the fabulous custom guitar maker Tom Curneen..."Jim, Your stereo preamp FM800z, combined with the SPX-3030 power stereo amp, coming out of vintage Altec Lansing 12’s is so Sweet!!! Your amps have an aural shimmer. The soundfield is wonderful thanks to your build quality and character of sound. Thank you for building affordable classics. My stairway to heaven, you are." Tom Curneen - Use this link to listen to Tom's amazing guitars.

Dear Jim, A miracle has come to pass - it arrived safely two days ago! I had very little time so far, but my initial impression is - awesome! It was really worth it. Both channels sound great. The bright switch and bass enhancement make it even more versatile. My setup is your preamp into a 35 watts tube poweramp from a local builder into either one or two 12'' cabs. I have a ABY switch on my pedalboard and connect it with four cables so that I have time based and Modulation effects between preamp and master. There are two boosters on the board - a midboost for solo tones and a fat boost for heavy rhythm. Works beautifully! The crunch channel on the amp sounds so fat and full, way better than any pedal i ever had. It also cleans up really nicely with the guitar volume. The clean is awesome too. Quite jazzy on 'normal' and sparkly on bright. It strikes me how quiet the preamp is. Very little noise. Well done! I am looking forward to spend much more time with it. You are a real gentlemen! All the best, Frank N. (Germany)  

Dear Friends at Frenzel...Thank you for this wonderful little FRENZEL FM-800Z amp / preamp. I am fully utilizing its capabilities as both amp and preamp and also combining the F and M channels to get a really nice tone. I lean a little heavier on the M channel. This amp seems to get better with time , warmer and richer.  The power amp section sounds great and gets actually pretty loud. The tone controls are very nice in that you can get an excellEnt variety of tones with them. The Rocker 800Z sounds so good with rich harmonics and overtones that a person can learn to play better and get those great tones. The level of build and sound quality would be very challenging and extremely expensive to beat. I want to thank all people at Frenzel that were involved in building this great little amp / preamp for doing such an excellant job. In the future I will probably order the 5E3-SD with a few upgrades. A local craftsman built the cabinet with solid teakwood. Sincerely, Donald K Bazille (Thailand)

FM-800Z - Mr. Frenzel & Sons & Co., - Got the FM-800Z   We've had it at our space for a few days.  I can't say how happy I am.  It sounds so great!  Everything about it is great.  It saturates so beautifully.  I had emailed you about my sides "collapsing" with all my effects (often in parallel) hitting the pre's I'd tried.  The 800z deals with it beautifully.  I hear compression now as opposed to distortion.  I can hit it hard with a delay and get it pumping but the reverb sliding through underneath sounds unscathed.   It's so rich sounding.  It really is exactly what I was looking for! Doug M. & Steve S. (Kansas)  

Just wanted to say thanks for a excellent amp! I ordered this with the 1 watt amp option not expecting much from it but expecting everything from the preamp. I've owned quite a few low wattage amps have have never really liked any of them. The Frenzel's little amp option blew me away, absolutely haunting tone with all the controls set at 5 and the master cranked with the guitar's volume rolled down a bit. That was something I wasn't expecting! Ran the preamp through the loop input of a 6L6 based head that I've always thought sounded lifeless and it's like being a kid in a candy store, can't find a bad tone if I tried. Thanks again! Mark S. (Florida)

Hi Jim,  Your Frenzel FM-800Z "Rocker 800" preamp is incredible with my Peavey Classic Series 50/50 and vintage Altec Lansing ceramic 12’s. By the way, your preamp is making my handmade guitars sound better than ever. Thank you for your excellent customer service, prompt updates, and incredible build quality! Sincerely, Tom Curneen (Washington)

Hi everyone at Frenzel Tube Amps, I just received the FM 800Z preamp.  I have been blown away by its incredible sound.I am using it with a Rickenbacker 4003 with the Ricosound.  The neck pickup goes to the fender channel and the bridge goes to the Marshall.  I put more bass on the fender channel and more treble on the marshall channel and it sounds amazing.  When you dig in it starts to growl and get a little more top end sizzle. The two channels are perfect compliments to each other.  The fender very fat and warm.  The marshall more bite in the top end. You get way more of an overdrive sound than I expected as well.  That's if you want it.  I will be using this for recording and most likely live after I build a nice case for it. Thank you so much for such a beautiful well thought out amp. Your newest fan,  Chris G. (New York)

FM-800Z - Dear Sir\Madam,  I received the FM-800Z Preamp. Thank you very very much. Very happy to make a business with Frenzel. Best regards, Mr. Ng Chin Fung (Hong Kong)

FM-800Z - I have one of these. I run it through my Mesa Mark V 25 and it sounds fantastic. It bridges the gap between the channel 1 crunch mode and the channel 2 MkIIc+ perfectly - William B. (Texas)

FM-880Z/2U  - When my FM-800Z2U got delivered it was enclosed in two boxes, one inside the other. The outer box had two florescent green “fragile electronic equipment” stickers on it for added safety.  I was impressed when I discovered the rack chassis was made of aluminum as I don't like rust. Some people say aluminum breaks down also, I say check out my aluminum boat, it looks new after years of use and a couple of trips each year to the cost in salt water. If it were made of steel it would be a a pile of dust right now. If you live in the southern states the humidity would take out a steel chassis after a few years unless you had a dehumidifier running all the time, then it would take a little longer. I took off the bottom panel of my preamp to find that the circuit board and related electronics are mounted on the top inside panel of the preamp, how thoughtful as what little dust makes in through the cooling holes will land on the bottom inside panel where it won't affect the electronics and can be removed in one swipe of a cloth. The eyelet board is almost one quarter of an inch thick, it will never bend, stress or crack unless you are trying to purposefully destroy it. All the components are mounted point to point. The board is there to stabilize and logically arrange the components. In traditional point to point type construction the components are soldered together with no added supported, other than another component, if there were ever a need for a component to be removed the heat of the soldering process could stress the other attached components, Frenzel has removed the danger by incorporating this type of eyelet board. All the markings on the components are readily visible as there are no components mounted underneath the board where you can't see them. The ceramic tube sockets are mounted on a separate aluminum bracket which is very sturdy and will undoubtedly stand the test of time. All the components are of top notch quality and the construction is suburb. Another refreshing quality of this exceptional preamp is the simplicity of its design, there is no extra unneeded circuitry for channel switching as one only needs to use an a,b or a,b,y channel switch for full control of the FM-800Z2U's channels. When designers add circuity for internal channel switching in their preamps they always use shared components which adversely effects the quality of the sound of the preamp, they add transformer taps to run the low voltage needed for op amps as well as other solid state components which are sometimes used for channel switching or low grade effects loops (non tube type), no so in Frenzel's case, the channels are discrete meaning no shared tube stages and no shared resistors or caps, another mark of ultra high quality. It is more expensive for Frenzel to design and build using discrete techniques I don't know how they do it for the prices they charge for their products. There is exceptional care and pride oozing from every aspect of their products. I am a designer and builder of my own personal tube equipment, if I had the time to build my own tube preamp with no compromises in cost or quality I doubt it would be as exceptional, functional or attractive as my FM-800Z2U. Frenzel has made well thought out rugged products that can stand generations of being moved around and used, in my opinion their equipment will only go up in value. Speaking of functional every time I plug in to my FM-800Z2U I love it more and more. The controls are endless in sweet spots, you find more each time you experiment. The FM-800Z2U is the most “amp sounding” of any tube guitar preamp I have ever heard and I have owned them all!  The old adage “If you want it done right do it your self” does not fly in this instance as you can not do it better than Frenzel and definitely not with less cost! Thanks ever so much Frenzel! I intend to be purchasing more of your quality equipment, I would rather be playing than building. Best Regards! Gary DiCenso (Maine)

For more reviews please check our Customers Reviews page.