REVEIW EQP-KT UPGRADED WITH FULLY TESTED MULLARD MODERN PRODUCTION TUBES

Does swapping tubes really make a difference? 

Is it worth extra $$ to buy fancy tested tubes?

Inside the EQP-KT, click to enlarge

We have an ongoing long term vacuum tube comparison going on in the High on Technology lab and some exciting early results are rolling in. Fully tested, graded and matched sets of 12AX7 and 12AU7 were installed in a pair of EQP-KT equalizers, replacing the stock Chinese “Bugera Selected” tubes (don’t you just love tube marketing). The results were shocking and impressive.

REVIEW: Tubes for Microphones, Preamps and Guitar Amps

12AX7A Super-Star of Guitar Amps

Are you curious about what tubes are, when they were invented, why they sound different and how they work? If the sound coming out of different tubes makes such a BIG difference, how come no music is marketed as “using it” or “game changing”? Let’s unpack the mystery around 9-pin miniature vacuum tubes used in guitar amps, tube-EQ, microphones and mic preamps.

LINE 6 SPIDER V60 REVIEW: Practice Amp Shows Its Age in 2026

It’s been a while since High on Technology reviewed any guitar amps, here’s an interesting addition to our flock of studio guitar amps. The Line 6 Spider V 60 dropped back in late 2016 (officially announced September 27, 2016) as part of the new Spider V modeling amp lineup. It was marketed as an easy-to-use, self-contained combo loaded with 200+ amp, cab, and effect models, plus built-in looper and drum tracks. Does it succeed in the burgeoning 10” or 12” self contained guitar amp category?

REVIEW HEADRUSH “FRFR GO” POWERED SPEAKER: Rechargeable battery too

Headrush is a relatively new player in powered speakers. The acronym FRFR was previously described here on High on Technology, Headrush has borrowed it and put it into the name of today’s review product. The Headrush “FRFR GO” is a small, inexpensive, portable speaker system with an emphasis on musical instrument applications — think guitar modelers, digital drum and synth use, jamming with loops, listening to tunes and so much more. But is it good?

REVIEW VOX AMPLUG3 AC30: Convenient, Inexpensive, but…

I wanted to love this little headphone amp from Vox. The clever, integrated design eliminates the need for a guitar cord, you just plug this little box into your guitar, plug your 1/8” headphone plug into amPlug3, and start jamming, right?

WHAT IS FRFR? Why you need Full Range Flat Response

In the world of audio, FRFR stands for Full Range Flat Response. It refers to audio equipment, typically speakers or monitors, designed to reproduce sound across the entire audible frequency range (roughly 20 Hz to 20 kHz) with a flat frequency response. This means the system doesn't emphasize or attenuate any particular frequency, aiming to deliver sound as accurately and neutrally as possible, without coloration or distortion.

REVIEW JOYO JA-02 II: Rechargeable Guitar Amp Bluetooth Speaker

Those clever designers at Joyo have combined a rechargeable Bluetooth speaker and a guitar amp together in a lightweight plastic amplifier, complete with switchable distortion, external line input, headphone output and USB-C charger hole. But there is one feature that blew my mind and caused me to immediately hit the buy button.

REVIEW MOOER PE100: Tiny Powerful Guitar Processor that easily fits in your shirt pocket

In the world of guitar effects, bigger isn't always better—especially when you're practicing late at night or jamming in a cramped hotel room. Enter the Mooer PE100, a compact desktop multi-effects processor that's designed to pack a full pedalboard's worth of versatility into something that easily fits in your shirt pocket. Released a few years back, this little beauty from Mooer Audio has earned a reputation as an affordable and complete solution for practicing guitarists. It's got an incredible bargain price, but does it deliver? 

A TRIBUTE TO JIM MARSHALL: The Father of the 4x12 Speaker

James Charles Marshall, affectionately known as "The Father of Loud," was more than just the founder of Marshall Amplification—he was a visionary whose innovations shaped the sound of rock 'n' roll and beyond. Born on July 29, 1923, in Acton, West London, into a family of boxers and music hall performers, Jim's early life was marked by adversity. A little-known fact is that he suffered from tubercular bones as a child, spending much of his youth encased in plaster casts and hospitalized, which deprived him of a formal education. Yet, this hardship fueled his resilience; exempt from World War II service, he turned to music, becoming a skilled drummer and singer. He even built his own portable amplification system for his vocals, foreshadowing his future empire.

REVIEW: Jim Marshall’s JCM2000 TSL100: The Misunderstood Masterpiece of Tube Tone

Jim Marshall

When you think of Marshall Amplification, you think of Jim Marshall—the "Father of Loud," whose vision gave us the iconic stacks that defined rock ‘n’ roll. From the JTM45 that powered the British Invasion to the JCM800 that roared through the ‘80s, Jim’s legacy is synonymous with pure, tube-driven tone. In 1997, under his watchful eye, Marshall released the JCM2000 TSL100, a 100-watt, all-tube amplifier that marked a triumphant return to the company’s valve roots. Yet, this amp remains one of the most misunderstood in Marshall’s storied catalog—criticized by some players but cherished by those who uncover its magic. 

REVIEW MXR X100 ROCKMAN REISSUE, IN A GUITAR PEDAL: Does it Rock?

The original Rockman X100 captured the unique guitar tones Tom Scholz brought to the band called Boston. Riding on the wake of popularity caused by the Sony Walkman, the Rockman was a compact, battery powered appliance that could be used with an included set of headphones to provide a wide range of guitar tones. Using a mini TRS splitter cable you could get the headphone sound out of the Rockman and into your recordings, many artists used this technique to record hit tunes that did not sound like Boston, thus making the Rockman a real tool for the masses. Those plucky Dunlop engineers in their MXR lab have now reconstituted the Rockman tone and packed it into a stomp box the same size as an original Phase 90. I’ve had the new one in my hands for a couple of months, how did they do? Is it good?

MARSHALL AMPS CLASSIC BRITISH AMPLIFIER COMPANY HAS BEEN SOLD

Details are slim at this point but Marshall Amplification, the company started by Jim Marshall in the early 1960's has been sold to a Swedish company. Marshall family heirs will hold significant stock.

This sale disturbs me at my core. If Jim Marshall were alive I don't think this would have ever happened. 

I hope this actually turns out to be a good thing but I'm doubtful based on my 63 years of experience with guitar and the music business at large. I suspect that social conditions in the UK are making it ever more difficult to run a profitable company based there. In addition, the family heirs are tired of fighting and running the company. 

WHAT IS THE BEST LESLIE FOR GUITAR?

The original Leslie rotating speaker system was packaged in a number of ways. If you're a guitar player who writes and records, and are curious about adding the rotating magic to your tone, this information is for you.

Rear of Leslie 147 system with covers removed for clarity

REVIEW MARSHALL MG15R GUITAR AMPLIFIER

CLICK TO ENLARGE

I’ve been using the Marshall MG15R amplifier for a little over a year. It has continued to climb upwards in price since I bought mine new for $129. I refer to this as my kitchen amplifier because that is where it usually resides, right next to me under the kitchen window. I never thought I’d say a little solid state amp made in Viet Nam was one of my favorite amplifiers but it is. Lets see why.

REVIEW UNIVERSAL AUDIO UA OX AMP TOP BOX IMPULSE RESPONSE REACTIVE LOAD BOX

 UNIVERSAL AUDIO OX AMP TOP BOX     $1299 street price

Universal Audio is a popular brand of DAW technology so when they came out with the OX I wondered what it was like. The OX is physically one of the largest impulse response technology devices reviewed here. It is also one of the most technically sophisticated with the most included integrated options for shaping your sound.

MARSHALL 1-WATT AMPLIFIER REVIEW, WHAT IS THE DSL1 MARSHALL?

 LOOKING AT THE MARSHALL DSL 1-WATT TUBE AMP

HEAD AND COMBO

by Mark King

NEW! CLICK ON LINK BELOW TO LISTEN TO MARK KING READ THIS REVIEW TO YOU

Mark King · DSL1 read by Mark King

Marshall DSL1 Head and Combo Amplifiers 

Marshall has been producing their DSL (Dual Super Lead) amplifiers for a number of years. The DSL designation refers to there being two preamp channels, one which is basically clean and one which offers extreme high gain.

REVVING UP THE LESLIE 147 WITH COMBO PREAMP AND NEW TUBES

KEEPING THE LESLIE 147 ALIVE AND WELL

AFTER 47 YEARS

by Mark King

I bought my Leslie 147 used about a year ago (here's a link to that story). Since that time I've had fun trying lots of different things with it. It did not come with a combo preamp like I've normally used on 145 and 147 models, instead it came with a Dr Fishsticks interface to control the speed.

Leslie 145/147 Combo Preamp

Preowned 40+ year-old Leslie combo preamps have been trending upwards in price because they're becoming more scarce and there are no new ones. I avoided buying one up until recently because they've been up around $500 on ebay. By chance I spotted one for $299 with a Buy-It-Now option, free shipping and guaranteed to be working or full refund. The seller had good feedback so I went for it to simplify and streamline my organ connections. 

REVIEW KEMPER PROFILING AMPLIFIER RACK

IS THE KEMPER PROFILING AMPLIFIER WORTH IT?

PRELUDE

Getting ready for the real tube vs digital smackdown

The Kemper Profiling Amplifier is a digital guitar amplifier. It has an input gain control, digital effects processing, speaker cabinet simulation and a standard complement of bass, mid, treble and presence tone controls. It is available in an oversize lunch box package or a rack mount unit, either configuration can be optionally configured with a 600 watt internal power amplifier. All that is the standard stuff. What really sets this thing apart is the somewhat bizarre, and totally unique way it can sound like any amplifier through a process called "profiling". Will Kemper destroy the tube amplifier industry by cloning the sound of all the best pieces into digital profiles?

LESLIE 147, THE MAGIC ROTATING SPEAKER SYSTEM

LESLIE 147 TUBE POWERED ROTATING SPEAKER SYSTEM

by Mark King for proworkshop.com

THE REAR OF STOCK LESLIE 147, UPPER AND LOWER COVERS REMOVED

PRELUDE

I bought a Leslie 145 brand new in 1972 (identical to 147 except a shorter wood-cabinet). It contained the 40 watt tube amp, came with the weird thick brown cable which is 30-feet long (the only choice). It also came with a good looking chrome preamp box, the whole thing was around $650; that was a lot of money for me. More than my car! But it had an amazing sound and I carried that thing around to many band jobs over the next 25 years. One bitterly cold winter night it almost killed me when I slipped on some ice while unloading the beast after a band job. I retired it from live performance use after that gig, it was just too big and heavy to haul around.

PULLING TUBES AND HOT RODDING BUGERA INFINIUM 1960 GUITAR AMP

HOT ROD THE BUGERA 1960

INFINIUM GUITAR AMPLFIER

by Mark King for Proworkshop.com

BUGERA 1960 INFINIUM GUITAR AMPLIFIER

I got my Bugera 1960 guitar head about a year ago from Sweetwater. I really like this amplifier a lot, it has amazing tone which is a lot like the Marshall Super Lead heads I had in the 70's and 80's. There is just one problem with the stock head, it's too LOUD!