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Rocker 800Z

Stereo Preamp


Model No. FM-800Z 
Series: Open Chassis Guitar & Bass Preamp   

MSRP: 695.00



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Rocker 800Z Stereo/Mono

2U Rack Mount Preamp


Model No. FM-800Z - RM
Series: Rack Mount  Guitar & Bass Preamp  

MSRP: $795.00



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The  FRENZEL FM-800Z  "Rocker 800" dual channel  stereo guitar tube preamp is part of our "INSPIRED" line of products.   It was inspired by the vintage Bassman 5F6A and JCM800 amps...but it is not a clone....this preamp incorporates features and mods developed over FRENZEL Tube Amps years of building and fine tuning amps.   You can use the "Rocker 800" as a preamp to enhance a tube amp or to drive a solid state amps to generate the classic 50-60's vintage tube tones. It is a perfect companion for the Frenzel SPX-3030 Stereo Power amp or the Frenzel SS-4772 Super Stereo amp.

The preamp uses  12AX7's to create two separate preamps each with its own Input Jack, Gain control, Tone Stack and Master Level control, Output jack. 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.  

Input 1 is the F section of the preamp.  It is voiced like the classic 5F6A Bassman.  Input 2 is the M section.  It  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 Level 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 warm clean tones of the Bassman...or that fantastic high gain rock tube preamp overdrive distortion that the Marshall JCM800 amp is famous for. 

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 and output jacks are isolated from chassis and it uses a star ground system and DC on the filaments for very low signal to noise ratio.

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, power fuse and power connector are on the rear panel.
The input  is high impedance. and the output is + 4 dBu line level. 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, keyboard 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  Plexi - Bassman style 3-BAND TONE STACK with mid-scoop for extended flexibility in shaping your tone.

  • Deep Pull-Switch on Bass

  • Bright Pull-Switch on F and M Gains

  • MASTER level control so you can crank the GAIN's up and overdrive the preamp without overdriving the output tubes.

  • 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.

  • Stereo Output Jacks with Stereo/Mono jack that connects F & M outputs together for Mono operation

  • 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  (12"W x 8"D x 7.5"H) or Open Chassis

Electrical Specifications: 

  • Input Impedance:  1 megohm 

  • Level:  Instrument Level (100 millivolts RMS)

  • Output Impedance:  10K ohm

  • Output Level:  Line Level +4dBu  (1.5 volts RMS) 

Physical Data: 

  •  2U Rack Mount Chassis  -  Overall Dimensions(19"W x 10"D x 3.5"H)  or Open Chassis -  Overall Dimensions(12"W x 8"D x 4.5"H)

  • Chassis - Heavy gauge aluminum with welded corners. 

  • Weight -8 lbs. 

  • 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 - F Input Jack, M Input Jack, F Gain/Bright Pull Switch, M Gain/Bright Pull Switch, Bass/Deep, Middle, Treble, Master Level, Pilot Lamp, On-Off Power Switch

  • Rear Panel Controls -  Power Cord Connector, Fuse,  F Line Out Jack, M Line Out Jack , F & M Mono  Output Jack

Wiring View:  Hand-wired point-to-point for long-life and reliability.

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Upgrade Options:

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

RETRO CAGE COVER  -  Ventilated cage with handle  for open chassis model provides protection for tubes and excellent ventilation. Add $125.00



Review  by Featured Artist & Master Guitar Builder Tom Curneen - (Washington)

 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.

Review  by Featured Artist Gary DiCenso - (Maine)

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)

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Review by Featured Jeff Florence - (California) 

Jim, thank you for this incredible amp! I am primarily a rock bassist and have been searching for that classic Hiwatt sound minus the Hiwatt price tag. You really nailed it! As a devotee of Lemmy I love the Marshall channel as well, but I can't stop playing the Hiwatt channel in my Rocker 800Z. The 1 watt power amp absolutely rips with guitar and I have been thrilled running the preamp into a Class D power amp to rumble my 8x10 bass cab. The build quality and attention to detail is fantastic. I can't recommend the Rocker 800Z enough, especially to bassists looking for a dirty, vintage tone.

Customer Reviews 

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)  

FM-800Z -  Hello, I recent!y bought a used Frenzel Rocker 800Z preamp, with the Fender/Marshall style channels. I use it for bass, and cannot say enough about how good it sounds. I mainly use the Fender channel, and the unit has separate outs, with volume control on each out.I have and have had a lot of different  bass amps through the years, and the sound quality of this is beyond anything I have ever had. It has a massive throbbing  push, when used at volume. And truly a 3d sound. It blows away the Alembic f2b, which is now out of control price wise. Steve Azola - Azola Basses (California)

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)  - 6 year follow up review.  I am a bass player and the proud owner of a FM800z.  I’ve been playing since 1990 and it is one of the best pieces of gear I have.  It must always be there!  I use a Rickenbacker with Ricosound.  The bass pup goes to Channel 1 the 5F6A channel and the bridge goes to Channel 2 the JCM800 channel for some crispyness to taste.  Thank you! Chris G. (Connecticuut)


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-800Z Custom Voiced Rackmount Preamp Review - Hey! The custom rackmount preamp with one channel voiced retro champ blackface & second channel voiced super bassman 100 has been kicking serious tones! Just finished recording the band's next album with it...and it's use with my bass is beyond words. Thanks! Chris C. (Colorado) 


FM800Z-CUSTOM VOICE - "Hello, I bought a used Frenzel preamp and it sounds amazing! Chan1 is a Fender Champ and Chan2 is a Bassman. I've had it for 2 days and I'm in love! Chris B.

For more reviews please check our Customers Reviews page.  

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