- Can I get a new Fryette name plate?
- When replacing tubes do you recommend any particular brand?
- What's the difference between tube and solid state rectifiers?
- What's the difference between Class A and Class A/B operation, and how does it affect the sound?
- What's the difference between Series and Parallel effects processing?
- What is Gain Stacking?
- What are the advantages of printed circuit technology over point to point wiring?
- What is slaving?
- When should I have my amp biased?
- How can I bias the amp myself?
- Why don’t FRYETTE amplifiers provide external bias points?
- Is it OK to install 6L6 power tubes in my amplifier?
- What's the difference between KT88, 6550, EL34, 6L6, EL84 tube types?
- What does VHT stand for?
Fryette name plates are available for owners who wish to replace the VHT name plate on their original Pre-January 1, 2009 VHT amplifiers or speaker cabinets. Name plates are available for all models displayed on this web site. To acquire Fryette name plates please select the "Nameplate Replacement" radio button on the support page and select the package you wish to purchase. Back to top
For optimum performance it's always best to replace tubes with the original factory supplied types. There are many reputable suppliers of quality tubes however. Please refer to your owner’s manual for details. If in doubt and you would like advice or technical assistance, always feel free to contact us directly. Back to top
The rectifier circuit in an amplifier converts the Alternating Current (AC) from the wall outlet to Direct Current (DC) required for operating the various circuits inside the amp. Originally, this conversion or "rectification" was accomplished using a vacuum tube rectifier, also known as a dual diode. Later with the advent of solid state technology, the rectification process was accomplished much more efficiently and less costly with silicon diodes. Besides the cost, one of the primary advantages of the silicon diode is its low voltage drop. Because of this characteristic, the solid state rectifier supply responds much more quickly to the increased current demand created when the amplifier is driven to full output. This gives the amplifier a tight, crisp and dynamic response. The tube rectifier exhibits a much higher internal voltage drop, which in turn causes the power supply voltage to sag when the amplifier is driven hard. We experience this sag as a natural sounding compression, which seems to give the amp a breathing, bouncy quality. In addition the tone will appear to sound softer or more rounded with increased sustain. Today we find that both the tube and solid state rectifiers have a valid application in helping to enhance the personality of a given amplifier design. Back to top
Generally speaking, the power tubes in a Class A amplifier operate at pretty close to full power whether or not a signal is being amplified. As long as the tubes are being operated at reasonable voltage and bias range we're OK. The beauty of this type of operation is that there is no significant difference between the tubes’ work interval and its rest interval. The distortion products created by this method of operation are very musical sounding and the overall tone has a pure quality.
When combined with the right output transformer, the harmonic blend created by the tube distortion characteristic and transformer saturation (that is to say, just past the point of maximum linear operation), is rich, full and fat sounding. It sounds pretty much like an amp turned up loud even when it isn't because it's operating nearly full out in a sense.
In class A/B operation the tubes are getting a big break. How much of a break is determined by the bias idle current setting. When no signal is present the tube is essentially at rest. When you begin to play, there occurs a transition from "off" state to "on" state between the push-pull pairs of tubes. This transition, known as the crossover region, produces a noticeably different type of behavior typically referred to as crossover distortion. Crossover distortion contributes harshness to the sound which can give the amp an aggressive personality. This can be interpreted as a good thing depending on what you are trying to accomplish musically. How the tubes are biased determines not only the tubes idle current, but also whether a greater or lesser amount of crossover distortion occurs. A high bias current will minimize crossover distortion, however, if set too high the tubes will overheat and could fail prematurely. Too low and increased crossover distortion will cause the amp to sound fizzy and lifeless.
The real up side of Class A/B operation is its inherent efficiency. The simple fact that each tube has a rest interval in its duty cycle allows the tube to operate at higher output during its work interval or "on" state. Thus, a power amp operating in Class A/B will typically produce about 30% more power than a comparable Class A amp. Since the typical output transformer in a Class A/B amp will not be required to operate at high continuous current, it will spend less time in saturation mode. This contributes to the clarity and detail of the power amp sound.
An additional advantage of Class A/B is that because they tend to run cooler, tube life can be extended somewhat. For strictly comparative purposes however, the essence of the debate is sound quality. We are attracted to the Class A sound because of its warmth, sonic complexity and rich harmonic content. The Class A/B sound is more articulate, dynamic and gives us the sensation of immediacy. Back to top
The effects loop design in all current Fryette Heads and Combos, allow either Series or Parallel operation. In the Series mode 100% of the signal from the preamp section of the amp is routed through the send jack to be modified through the effects device. The modified signal is then returned to the effects return jack and sent to the power amp section for final amplification. Effects such as equalizers, compressors and multi-effects processors with fixed or programmable mix controls are typically operated in Series mode. Effects processors that can handle higher than typical guitar level signals are usually recommended in this application.
Effects such as reverbs, delays, and pitch shifting devices which can be set for 100% "wet" output can be operated in Parallel mode if desired. In Parallel mode only a portion of the preamp signal is routed to the effects send jack for processing. In this case the original signal path inside the amp is protected from the sometimes undesirable side effects of external devices such as signal loss, impedance mis-matching, coloration of the sound and distortion. The processed signal is returned to the amp to be blended with the internal dry signal and then sent to the power amp section for final amplification.
Although it is possible to use pedals in the loop, it is generally not advised as the higher signal level in the loop can overload the pedals instrument input. Although this will not damage anything, it could result in undesirable distortion and loss of dynamics. Back to top
Gain Stacking is a feature found on many of our high gain preamp channels that allows you to pre-select the number of gain stages utilized in a selected channel to achieve the desired amount and type of gain you are looking for.
Depending on the model of amplifier, you may set up a crunch sound with 3 stages of gain and a solo sound with 4 stages, or vice versa. Or you may want 2 high gain lead sounds or 2 medium gain rhythm modes with slightly different tonal balance or volume. This can all be accomplished easily and quickly with Gain Stacking. The Gain Stacking circuit utilizes a "flying" 4th stage that can be assigned wherever it is needed without the waste of un-used or over-compensated tube stages in the preamp section of the amp. This is one of the reasons why our high gain channels produce as much or more gain than other designs with a lot less noise, hum and microphonics.
On PITTBULL series amplifiers this feature is activated by the HI GAIN switch on the front panel. On the DELIVERANCE and SIG:X amplifiers, this feature is activated by the MORE/LESS switch. Back to top
For the record, all FRYETTE amplifiers are primarily hand built PCB assemblies. All components such as resistors, capacitors, pots, switches, tube sockets (that's right…Tube Sockets…Pre and Power) and various other items are reliably and confidently PCB mounted. Do not confuse “PCB Mounted” with “Poorly PCB Mounted”. There is a world of difference. We use top quality double-sided glass epoxy boards with heavy copper plating and plated through holes for maximum reliability and signal integrity. PC boards are mounted on heavy-duty tubular aluminum supports attached to the chassis with machine screws. Small tube sockets have large diameter solder pads. Large tube sockets are attached to the board with heavy tubular aluminum supports and chassis mounted with machine screws to form a solid and bulletproof board to chassis assembly.
There are a lot of misconceptions and misinformation about printed circuit board construction versus point to point assembly. The problem we see is that many times a failure of a PCB amp is often caused by the circuit design itself, not the board design. We will discuss the issues as they relate specifically to the manufacture of our products.
Since there is plenty of information out there about the origin of point to point wiring and PCB's, we'll skip the history lesson and get right to the pros and cons.
Contrary to what you may have heard, great tone is not the exclusive domain of point to point wired amps. Even the use of top quality components and meticulous assembly methods do not guarantee good tone. There are plenty of examples of great and lousy sounding products in both point to point and PCB categories. There are well built, mediocre sounding amps and sloppily thrown together, great sounding amps. In fact, undesirable sonic characteristics frequently attributed to circuit boards are much more likely to occur in point to point wired amps. Stray capacitance, phase cancellation, signal degradation, and crosstalk between stages are common problems in point to point designs. Most of these conditions are easily minimized or eliminated in a well executed PCB design.
One interesting and often overlooked side benefit of PCB design is the ability to precisely control the way the board will "sound" by experimenting with placement of sensitive components. We frequently use this technique of "tuning the board" to tweak various parameters of a circuit which might normally be accomplished with the relatively "brute force" use of added capacitance or tone robbing bundled wire harnesses.
One of the most attractive benefits of PCB construction is their inherent consistency. Once the design is complete, it can be easily reproduced with a very high degree of accuracy. In our particular case, the object is to produce an amplifier that meets a set of pre-defined sonic and functional criteria. These criteria are built into the board design and are not subject to the wide variations in tolerances normally found in the point to point assembly process.
In the late fifties, state of the art point to point construction ( i.e. military and recording/broadcast electronics) incorporated "turret boards" that supported most of the small components on Nickel/Silver plated posts staked into thick Fiber or Glass/Epoxy strips. The bulky components (pots, jacks, switches, filter caps, meters and transformers) were chassis mounted and meticulously hand wired to these boards. Some of today’s more popular (and more expensive) point to point amps utilize low cost phenolic "terminal strips" with thin Tin plated lugs instead of the much more rugged turret boards. This is a far cry from the venerable point to point designs of the past. The terminal strip method is not particularly rugged or easily serviceable, usually requires much more extensive use of wire, solder and wiring harnesses, and often results in a circuit layout that is subject to wide variations in circuit behavior. Two identical amplifiers built this way are very likely to - and often do - sound completely different!
Reliability and Serviceability
Needless to say, there is a right way and a wrong way to do everything. One might be a little bit more generous and say that there are an infinite number of interpretations of the term "cost effective". Indeed! There are of course legitimate reasons for peoples seemingly genetic aversion to printed circuit boards and all one has to do it gaze into the guts of a PCB amp that falls into the "cheaper to replace than repair" category to see why this is so. It’s a fact however, that circuit boards dominate the electronics industry. Therefore it is important to remember that the Internet connection you are using to access this web page is bouncing off of a satellite orbiting our fair planet that will probably operate flawlessly far into the next century…utilizing printed circuit boards.
How then do we account for this large reliability gap? Simply stated, printed circuit boards pretty much do exactly what the designer intended for them to do. Nothing more, nothing less. If top notch performance and long term reliability are the design objectives, then the end product will perform and last provided that it is correctly engineered. In this context then, it is logical to conclude that a well designed, high quality PCB based amplifier is more than likely to perform as well or better and last easily as long as or longer than a point to point wired amp.
All things considered, we feel that the point to point method of amplifier construction is unnecessarily time consuming and excessively costly. When you pay a premium price for a quality point to point amplifier, it is pretty much understood and taken for granted that you’re not necessarily paying for performance and flexibility. A well designed and executed PCB based amplifier sacrifices nothing to sound quality, construction quality or long term reliability and value merely as an automatic consequence of the use of printed circuit boards. The labor saving aspect of PCB amplifier construction makes it possible to offer a wide variety of features and functions which translate to a higher "Bang for the Buck" ratio. Back to top
Slaving is a method for using amp heads or combos as a signal source in rack systems or multiple amplifier switching systems. The term simply refers to the practice of using one amp (typically a head or combo) as the "Master" amp or primary tone source, and another (typically a power amp) as the "Slave" amp which does the work of driving the speakers. Slaving allows you to generate just the right blend of preamp and power amp distortion in your Master amp. The resulting output is then attenuated down to a practical signal or line level which can then be routed to a switching system, mixer, effects processor, stereo power amp, recording console or any combination of the above.
Slaving is especially useful in live situations where it is desirable to reproduce a variety of different amplifier and distortion characteristics that may have been originally produced in a studio environment with multiple amps and speakers. It usually involves running the Master amplifier "full out" into an enclosed speaker or "Dummy Load" such as a high power resistor or power attenuator. A low level signal is then taken from the Master amp output using the "line output", an external signal attenuator (pad), or some type of speaker emulation device, which is then sent to an effects system, power amp and then to a pair of speaker cabinets.
This is not generally considered to be the most practical of systems, but when done right, it's pretty hard to beat. Anyway, who cares about practical when your main objective is ultimate sonic satisfaction? Back to top
Generally we recommend having the amp biased whenever the power tubes are being replaced. Even if you stay with a particular brand or type, the transconductance of the tube – often incorrectly referred to as “gain” or “distortion rating” - varies even within similarly matched sets. Biasing at replacement time is the best insurance for consistency and reliability. Back to top
Biasing is only one part of a complete test and evaluation procedure, requiring an oscilloscope, a dummy load, a mulitmeter, a signal generator, an adjustable power supply and some method for calculating power output and distortion - not to mention, a clean, safe, organized workspace. Understanding what you are doing and why is of paramount importance.
Adjusting the bias based only on idle current reading is ballpark at best - fine for a rush job if you know what you're doing, but easy to get wrong. Most end users are not qualified to perform even this basic procedure and the likelihood of doing damage or getting injured is prohibitively high. Back to top
Experience has shown that expediency, rather than care is the biggest motivation for providing external bias points. Being that very few are really qualified to perform this procedure properly, we feel that manufacturers who offer external test points are well intentioned, but do not adequately evaluate the risks. Manufacturers like FRYETTE and many others who do not offer this feature, but who are much more realistic about the possible consequences, are simply being more responsible in our opinion. Back to top
Fryette output transformers are designed specifically for the tube type selected for use in each design. In fact most if not all amplifiers are optimized for the primary tube type originally installed from the factory. In our former bias switch equipped models, and in any other amplifier so equipped, the original factory supplied type will always perform better and more efficiently than any other tube that the bias switch may allow. This is because the transformer is in fact primarily an impedance matching device between the tube and speaker impedance. Changing tube types therefore alters the circuit impedance which results in an impedance mismatch. As a result, installing 6L6s in an EL34 optimized design, or vice-versa will result in a decrease in headroom and output power and could cause other less than ideal distortion artifacts such as grainy distortion sound, fizziness or lackluster dynamics.
The change in sound you experience when changing tube types is often incorrectly associated with the tube type itself, when what you are really hearing is the behavior of the tube in a less than ideal operating environment.
In short, the tube switching feature is a nice idea on paper and does appeal to the end user as a useful feature. Manufacturers realize this and are usually happy to let the customer believe in the “versatility” myth this has created.
This is not a criticism of 6L6 tubes or 6L6 based amplifier designs in general. It is simply a fact of amplifier design. Although it is possible to design an output transformer that will operate at the average impedance of two or even 3 different tube types, to do so would naturally guarantee that no tube would represent the optimum selection, which is of course why nobody does it.
In Fryette amplifiers, the power amplifier section is designed for optimum dynamic response and harmonic balance. This is an important attribute which is largely responsible for the unmistakable sonic signature of our amplifiers. Shortly after first offering a bias switch for several models, we began to realize that this represented a compromise in our designs and product quality. As a result, the EL34/6L6 and KT88/6L6 switch functions were discontinued in all Steven Fryette Design amplifier models as of January 2004, and we no longer support this switch function in older models so equipped. Back to top
In order to keep the subject matter concise and relevant to FRYETTE amplifier designs, we'll break these tube types down into 3 basic categories: High Power Output, Medium Power Output and Low Power Output.
High Power Output: KT88, KT90, 6550
Although not widely used in the guitar amp industry, we find these to be ideally suited to players who want power punch and articulation. We use KT88s in a variety of configurations, mostly in pairs and quartets and in some cases, sextets. The KT88 is unique in that it behaves a little like a cross between a 6L6 and an EL34 with smooth silky upper harmonics and good bottom end clarity. They are capable of delivering 100 watts per pair and this is the typical application in which they are applied in the TWO/NINETY/TWO and TWENTY ONE FIFTY power amps and SIG:X head. They can also be operated more conservatively as is done on the PITTBULL ULTRA-LEAD and DELIVERANCE ONE TWENTY and in the DELIVERANCE SIXTY where they typically deliver about 60 watts per pair. Because of the high output capability and efficiency of these tubes, amplifiers that use them exhibit a wide dynamic range, lots of low end power, crisp attack and miles of headroom.
Medium Power Output: EL34, 6L6
These are the standard bearers of the majority of the tube guitar amp industry for the last 40 years or so. Typical output for a pair is 50 watts. We use EL34’s in the TWENTY ONE HUNDRED power amp, TWO/FIFTY/TWO power amp, HUNDRED/CLX head, HUNDRED/CL head, FIFTY/CL head and others.EL34’s are harmonically rich sounding tubes with a strong upper midrange which complements guitar voicing very nicely. When driven hard they exhibit a smooth transition into distortion while maintaining clarity and good tone quality. The venerable 6L6 power tube has found its way into FRYETTE amplifiers from time to time. They generally sound a little cleaner than EL34’s and tend to have a bit more beef in the low end as well as more bite on the top. Some players prefer the extra clarity and punch of these tubes. Others just like them because they are used to the 6L6 sound. However, we prefer the sound of EL34’s in our amps and these are what the above models are shipped with as standard equipment.
Low Power Output: EL84
This great sounding and economical tube, has had quite resurgence in popularity in recent years due to its increased availability. Typically used in quartets and run in Class A mode, they are good for about 30 watts or 40 to 45 watts in Class A/B. They basically sound like a small screaming EL34 with a rich fat midrange voice and great distortion tone. We have used this tube in the PITTBULL FORTY-FIVE series heads and combos and the PITTBULL SUPER THIRTY. Back to top
VHT founder Steven Fryette moved to Los Angeles from Seattle in 1976. After a few years playing guitar in Southern California cover bands he began focusing on original material and needed a day job to pay the bills. With an innate ability to tinker and coax broken things back to useful life, Steve eventually landed a job doing amplifier repairs and modifications at Valley Arts Guitars, then the epicenter of groundbreaking custom guitar and amp activity in LA. While at Valley Arts, Steve honed his skills doing repairs, modifications and custom work for the likes of Eddie Van Halen, Steve Lukather, Larry Carlton, Tommy Tedesco, Ry Cooder, Buzzy Fieten, Carlos Rios, Duane Eddy, and many other legendary players. Pretty soon his experience in finding innovative solutions for guitarists led him to try out some of his own ideas in guitar amplification.
After several years of building experimental prototypes, Steve decided to go live. Thus began the search for a suitable company name.
“Outside of my circle of friends and clients, I wondered how much sense it made to put my name on the front of an amplifier. Something about that struck me as arrogant or presumptuous, as in “who’s this guy?” I decided to try a pseudonym first. If I failed to come up with something suitable, I’d go with my family name.
I worked on it for weeks…reading, researching; drawing…it reminded me of my days sitting in the back of the class in grade school drawing pictures of drums and guitars. It was also just like trying to name a band – everything I could come up with seemed to have been taken and everyone I discussed it with offered the usual predictably useless suggestions.”
Steve worked tirelessly on this project while developing the prototype 2150 power amp and preparing for the first production run. Time for coming up with a brand name was running out.
“One day a factory rep from TC Electronics visited Valley Arts to demonstrate a new TC product. I was intrigued with the product, but much more interested in the name. I asked the rep what TC stood for. In his thick Danish accent he replied “It stahnds for nussing rilly. It just feelz goot to say in ze mouse.” That was a watershed moment for me. I went back home and began putting letters together that I thought sounded good. It was just as frustrating an effort as what I had been doing already, but I had a renewed enthusiasm for it.
I read where David Byrne of Talking Heads had cut words out of magazines and scrambled them to create song lyrics. I tried that with letters and made a chart of combinations that “felt good to say in the mouth”. Eventually I settled on VHT.”
With the help of some friends in the graphics business, Steve tried various logo ideas. Nothing clicked. He realized there were too many cooks advising him on what a professional logo should look like and went off on his own, eventually settling on a homemade font style using raised letters with a shadow supposedly representing light coming from a sharp angle. It was a very complex logo design.
“It only looked right at a certain height to width ratio. If you messed with that ratio even a little bit, it looked awful.”
His graphics buddies commented that the “light” was all wrong. Steve didn’t care. Once he got the ratio right, he liked the way it looked and besides, time had run out.
“Once I had the logo I soon realized I was going to find myself in the same spot as the TC rep. What does it stand for? I didn’t like that TC “stood for nothing” It must stand for something. I started trying to attach meaning to the letters – an endeavor even more frustrating than coming up with the letters in the first place. Vintage High Tech, Valve Harmonics Technology, Very Heavy Tone. They all sounded stupid and contrived and I realized that this was because it was contrived – so obviously after the fact.”
Larry Latham, a fellow employee at Valley Arts jokingly suggested Valley Heroin Transport
“It was brilliant. I knew it wouldn’t fly in the long run, but it was a signpost – a way forward. I could make a joke of it. I have a terribly sarcastic streak and the idea of making fun of myself was appealing. I went back to the task of finding the right keyword and eventually it came: Voluptuous. It jumped right out at me. I then remembered my fondness for 60s underground comics- Zap Comics in particular - and a gruesomely funny motorcycle gang; the Hog Riding Fools created by the great S. Clay Wilson. One of the characters was a mammoth biker mama riding on the back of a chopped Harley. She had a black scar on the inside of her thigh where she got burned by hot motor oil. “Burnt the livin’ piss outa me and I didn’t even blink” she grinned. In the next frame appeared a crosseyed top heavy biker chick. She was perfect; a Voluptuous Hog Tramp. My work was done.”
Although funny at first, ultimately the inside joke proved obtuse and difficult for the public to swallow. Steve was constantly put upon to reveal the “true” meaning of VHT.
“After many years the whole charade just wore thin and I earnestly wished in retrospect that I had just gone ahead and proudly flew my family name.”
Not surprisingly then, once the opportunity to rectify that situation presented itself, Steve jumped on it.
“I feel like a huge weight has lifted off my shoulders. Now the truth is revealed and all is as it should have been from the beginning.” Back to top