Guytron GT100 Head

Dave and others below have covered the circuitry and other features very well and you can download them at the guytron website. All I can say is that this amp has totally consumed me with a desire to play it unlike every amp I have owned in the past 25 years.

I use a Strat, Anderson, Tele, Les paul and an old Jazz box and with each guitar you hear all the subtle nuances that come from each one. I play Hard rock, blues, fusion and some jazz and country. In every style this amp does the job!

It is built extremely well and I have had no troubles as of yet.

Guy has responded to every email and question very quickly.

Played for 25 years. Also have Egnater TOL combo and some other amps. I am thinking of getting another one in case anything ever did happen to it. Compared to ALL other amps I have heard or played, this is by far the best amp made. It will do the best sounds from the best amps ever made and some of them better than the most sought after tone machines on the planet. If you can afford an amp in this range don't even worry about hearing it just order one. You will kick yourself If you pass it up and hear one after you spend your $ on a Soldano,Matchless,Mesa,Rivera,Fender,Bogner or anything else in this kind of price range. The cabinets are equally impressive. email me with any questions you have and I would be happy to share any info I can. If other ratings for amps are a ten this one is ceartainly an eleven!

Let me start off by quoting the Guytron sales brochure:
THE HEAD:
* Exclusive patented design delivers that "on 10" sound at any volume (without external power attenuators), restoring power amp distortion and harmonics missing from conventional master volume technology
* Cascaded power amp design utilizes EL84 and EL34 power tubes operating in Class A and Class AB
* Vintage clean and dirty tones (from crystal clear to hotrodded overdrive)
* Channel Switching (2 footswitchable channels)
* Hand wound, custom-designed, interleaved paper bobbin transformers
* Hand-made in the USA
THE CABINET:
* One 12" Celestian Vintage 30 and one 12" Celestian G12T75 (Greenback tone) in one cabinet to provide balanced clean and dirty tones.
* Angled baffle board
* Custom tuned closed back design
* Lightweight and portable
* Full stack fits in a compact car
* Hand-made in the USA
Let me add the following:
* Low-level (-10 db) and high-level (+3 db) effects loops are accessible from the back panel of the head, allowing simultaneous operation of both pedal and rack-mount effects units. The Effects knob on the front panel controls the wet/dry mix sent to the output power stage.(The manual doesn't explicitly mention this, but the Effects knob can be used to setup the loop for parallel or serial operation. Just turn it completely clockwise and all of the amp's signal is sent to the effects loop - now you have a serial loop!)
* Each channel features Gain, Tone and Level controls. Channel A spans the range from sparkling clean on up (in very fine increments) to a bit more gain than a stock Marshall plexi. Channel B spans the range from warm, round clean tones on up to way more gain than most humans would ever need. The Gain knobs control the degree of saturation. The Tone knob in channel A affects the gain and distortion in the upper registers. The Tone knob in channel B does not affect the distortion characteristics of the channel, but simply controls the amount of high-end bite. The Level knobs do not affect the level of distortion in either channel, but simply control the amplitude of the signal fed into the EL34 power section. Consequently, their purpose is to set the relative volume between channels.
* The signal from both channels is routed to a pair of EL84s running in cathode-biased Class A and then into a transformer and finally into a resistive dummy load. According to Guy Hedrick, this transformer is designed specifically to drive the resistive dummy load, as opposed to most output transformers, which are designed specifically to drive speakers, which are reactive loads. This is where Guy's design is different than anything currently in production. I also believe this is where most of Guy's patent activity is centered. Guy's transformer/dummy load pair DOES NOT attempt to emulate the reactance, or the tone, of a speaker as do many of the inductive attenuators on the market (such as the Marshall Power Brake). Guy has simply matched components according to accepted laws of audio electronics and attempted to preserve signal integrity throughout the signal path (through the use of extremely high quality components, especially the transformers). The coloration of the speaker transform occurs naturally when the signal finally reaches the speaker cabinet. Obvious, yet brilliant! (By the way, the Level controls described above are placed after the dummy load.)
The signal from the Level controls is then routed to the master tone section, which sports Master Volume, Treble, Mid, Bass and Presence controls (as well as an Effects knob, which controls the mix in the parallel effects loops as described above) and then into a quartet of EL34s (100W, Class AB2), a main output transformer and then out to the speakers.
This configuration allows the user to adjust the gain in each channel for the just the right amount of EL84 power amp saturation, the relative volumes between the channels with the Level controls and then the final overall volume and tone with th

The Guytron produces the tones we all love. This is the real McCoy - TRUE power amp saturation at just about any volume you want. This is the tone I used to get as a kid with cranked Plexis and Twins (and more recently with a Power Brake and Tone-Master)...but now I can do it at blues-club volumes and without the loss in tone experienced with power attenuators. The clean tones are also the real deal - sparkling, rich and sweet. No compromises have been made here at all. In my discussions with Guy, he always expressed as much concern over the clean tones as he did over the dirty.
Sure, you can probably get similar overdrive tones by cranking any one of the many fine lower wattage, boutique tube amps currently on the market. BUT, how do you adjust that volume to suit the venue (without resorting to tone-sucking attenuators)? AND, how do you get any kind of clean tone without hauling another (higher powered) amp along with you? AND, how do you get the myriad low and medium gain overdrive tones you need at the volume you need? The answer is the Guytron!
Now, with that said, what are the amp's shortcomings? Well, there really AREN'T any, as long as you're aware of what tubes, pickups and tone settings you're using. When I first received the Guytron, I plugged a Barden-loaded Strat into it and set all the tone controls at 12:00 (as Guy suggested). My FIRST impression was that the amp was too bright. (It sounded phenomenal with humbuckers and Silver Lace Sensors though.) In any case, I was quickly able to adjust the amp for warmer tones with the Bardens by slightly rolling off both Tone controls and the Treble and Presence controls. Another improvement came when, on Guy's advice, I swapped out a very bright and somewhat thin (to my ears) Philips 12AX7 preamp tube for a Chinese 12AX7. Another improvement came by swapping out the Sovtek EL84s for some Tesla EL84s. Finally, complete tonal bliss was acheived by swapping out the Russian and Chinese phase inverters for Yugoslavian EI ECC83s! So, my GT-100 has Chinese 12AX7s everywhere, except for the phase inverters, which are EI ECC83s. Also, the Sovtek EL84s have been swapped out for Teslas. The original E34LS tubes (from Tesla) were left untouched. With these tube changes, ANY guitar/pickup combination sounds absolutely stunning in this amp...almost regardless of the EQ settings. I have tried a Barden-loaded Strat, a Silver Lace Sensor-loaded Strat, a vintage SG, an ES-335 and a Tom Anderson do-it-all Strat and they have ALL sounded amazing!
Let me emphatically state, however, that this amp is not overly picky about tube types. You can get unbelievable tone with any tubes that aren't defective! However, the GT-100 IS a relatively high fidelity amp and, as a result, you WILL be able to clearly hear the differences among various tube types. To my ears, the tube tweaks mentioned above represent prehaps a 3-5% change in tone. These kinds of changes simply reflect differences in personal taste. For example, Guy prefers the Sovtek EL84s for their more aggressive tone when overdriven. Personally, I prefer the Tesla EL84s for their smoother overdrive characteristic. Let your ears and musical style requirements be the judge.
By the way, there is no reverb in the GT-100. But, you won't miss it in the least! Just talk to any of the boutique amp builders and most will tell you that reverb just gets in the way. (Reinhold Bogner told me that he resisted putting reverb in the Shiva for MONTHS until he was "forced" to do so by popular demand. You won't find it in his Ecstacy though. You also won't find it in the GT Soul-O 75 or Dr. Z's wonderful new Route 66 or the Fender Tone-Master, etc, etc.) In any case, if you absolutely had to have reverb in the GT-100, you could always stick a pedal or rack in the effects loop.

In four months of almost daily use, I have had no problems whatsoever. I have taken the amp apart many times and, as an electrical engineer myself, can state with confidence that this amp is built to last. Virtually everything that could be done to build the best tube amp possible with current technology has been done. The ONLY possible exception to this statement MIGHT be the fact that snap-on locking connectors were used to connect the chassis-mounted preamp tube sockets to the main signal board, as opposed to simply soldering the wires to plated-through holes. This was done to enhance serviceability. The locking connectors themselves should never become loosened, but it IS possible for assembly personnel to incorrectly crimp the wires to the sockets which reside inside each connector. However, if that step is performed correctly, then it's just as good as solder and should stay connected forever.
I currently use the GT-100 without a backup, but may purchase something lightweight and relatively cheap (like a Trademark 60, for example) that I can easily throw in the trunk and retrieve should I ever have tube problems that can't be quickly solved on-stage. Other Guytron users have reported heavy usage over periods as long as three years (with original tubes!) without experiencing any downtime.
Therefore, based on the design and construction techniques, the materials used, my personal experience and the longer term experience of others, I can confidently hand out a 10 for this category.

Guy Hedrick is extremely supportive! He has given me all kinds of great tips and advice, from optimum mike placement to interesting tube substitution options to advice regarding tube bias. He also faxed me a block diagram of tube function and location, not to mention spending WAY too much time on the phone with me. Can't get any better than that! Let me also state that Mike Glazier from Main Street Music was extremely helpful and honest in providing information and support throughout the purchasing phase. (He also threw in a free guitar strap, which I actually needed at the time!) His seven day, no-questions-asked return policy gave me enough time to thoroughly evaluate the amp and make the right decision! In my case, this was crucial because I was comparing the GT-100 to another very fine amp that I owned at the time - the Bogner Shiva.

Overall, this amp is everything a discerning guitar player could ever want. There are DIFFERENT tones out there, but are aren't any BETTER ones. I compared the GT-100 extensively to my Bogner Shiva 1x12 6L6 combo. I had several people take "blind" listening tests in addition to just tweaking for endless hours on my own. Except when playing at EXTREMELY low volumes, the GT-100 consistently edged out the Shiva. Surprisingly, at extremely low volumes, FAR below practice volumes, the Shiva distortion was smoother. But, at anything other than whisper quiet volumes, the GT-100 was more complex and dimensional in both clean and distorted settings (even when using the Shiva with reverb and the GT-100 with none).
The GT-100 also allowed much finer control over the distortion levels and distortion characteristics than did the Shiva. Even with the boost off, the Shiva just could not be adjusted for those elusive "in-between" distortion sounds. The GT-100 gets them all, both vintage and modern. As a testament to the Shiva though, I have to admit that its distortion characteristic was just as smooth as the GT-100's, but once again, not as complex and dimensional. The Shiva also seemed to have this VERY slight, but pervasive, midrange honk that couldn't be dialed out. I never really noticed this before until I got it right next to the GT-100. An A/B box is an amazing tool...
Before the Shiva, I owned a Fender Tone-Master. For my tastes, the Tone-Master distortion tone didn't come close to the Shiva's or GT-100's, unless I cranked it up through a Marshall Power Brake. I saw Billy Gibbons play one live on VH1 and it was THE BEST tone I've ever heard him get! Just amazing. So, in the right hands and in the right application and at the right volume, the Tone-Master can sound absolutely great too. (By the way, the Tone-Master does have an absolutely beautiful warm, round clean tone.)
The other guitarist in our band currently plays a Groove Tubes Soul-O 75 head and 2x12 cab, but used to play a vintage Black-Face Twin cranked through a Power Brake and a Mesa Trem-O-Verb. In extensive listening comparisons, the Soul-O 75 easily edged out the Twin and T-Verb! In fact, I have to admit to liking the Soul-O 75 as much as the GT-100! They're different animals to be sure, but just about equal in most categories as far as sheer quality and complexity of tone is concerned.
As for the other amps I've played and compared, please refer to my Shiva review in this same forum.
About the only thing I would add to the GT-100 is a duplicate of each channel (or at least the A channel) and the ability to footswitch between them. That way, you could have "presets" for clean rhythm, crunch rhythm, light overdrive lead and heavy overdrive lead. I get all those tones now, but I need to tweak knobs between tunes and insert a Boss LS-2 (used as an active guitar volume control) in my signal path to do it. Of course, the trade-off is cost and complexity. At about $2500 for a head and 2x12 cab (which is definitely a fair price, considering the workmanship and materials), I think the price point would probably become unnecessarily inflated with those extra channels.
The other "wish" might be for a 6V6/6L6 version of the GT-100! I have always seemed to like 6V6s better than EL84s and 6L6s better than EL34s. For example, the Mesa Blue Angel 6V6 setting always seemed to be a touch "better" to my ears than the EL84 setting. The Shiva 6L6 version seemed to be a touch "better" to my ears than the EL34 version. Of course, there's a much better world supply of EL84s than 6V6s...at least at this point in time! But, maybe we'll see something like that from Guy in the future...that is, if he can ever dig himself out from massive response he's getting to the CURRENT version!

Features: A footswitchable 2 channel, 100 watt all tube amp with a radical new design where 2 EL-84's (and a transformer) are fed by the preamp section prior to hitting the quartet of EL-34's in the power amp stage. 2 simultaneous effects loops (high and low level) with effects blend control. Each channel has separate Gain, Tone and Output controls and the master section has Bass, Treble, Midrange, Presence, Master Volume and the Effects Blend. I am also using 2 Guytron 2x12 cabinets. Each cab is loaded with 1 Celestion GT12-75 and one Celestion Vintage 30.
I play mostly Pop(Hendrix, Burning Water, Seal, Eric Johnson, etc) and this amp has all of the features that I need. I have seen some people complain about the lack of reverb, but it doesn't bother me. The thing kicks ass right out of the box!!

Plain and simple. Its the BOMB!!!! It sounds better than just about any amp that I have ever owned. If anyone wants the balls sound do the this; run your amp through a dry cabinet and then run a line out to a stereo rack so that you have a wet and dry signal. I do this with a Bradshaw switching system, my GT100 and a TopHat King Royale and I have to say that this combination rules. It costs a hell of alot of money, but it rules. I play a Tyler classic strat and a Studio Elite through it and the single coils sing like nothing that have ever heard. Eat your heart Eric Johnson!

Never had a problem!! Don't expect to either. If I do, I'll let you know.

Haven't had to call yet!

I've been playing for about 15 years and I love this amp. Like I said above, I have a TopHat King Royale that I use with this rig and it rules to. Maybe I should review it as well? I've owned Matchless, Soldano, Marshall, VHT and Rivera amps. While these are all great amps, the GT100 is just more pleasing to me. Go buy one!! NOW!!!!!!!!!!!

Features: A footswitchable 2 channel, 100 watt all tube amp with a radical new design where 2 EL-84's (and a transformer) are fed by the preamp section prior to hitting the quartet of EL-34's in the power amp stage. 2 simultaneous effects loops (high and low level) with effects blend control. Each channel has separate Gain, Tone and Output controls and the master section has Bass, Treble, Midrange, Presence, Master Volume and the Effects Blend. I am also using 2 Guytron 2x12 cabinets. Each cab is loaded with 1 Celestion GT12-75 and one Celestion Vintage 30.
I have been using the GT-100 setup for about 4 or 5 months for live performances, rehearsals and practice at home - pretty much everything! The versatility of this amp is unrivaled. I play rock, blues, country, alternative and the occassional Van Halen tune and I have no trouble finding what I need in this amp. The design of the amplifier allows the EL-84's to saturate at a low wattage and provide tube saturation at low volumes so you don't have to crank this amp into oblivion to get a great sound. The harmoinic content of any note when using the higher gain settings is nothing short of incredible.

I am currently using an Ernie Ball / Music Man Axis Sport loaded with a DiMarzio Steve Morse in the Bridge, a DiMarzio Virtual Vintage Blues in the middle and a DiMarzio Pro Track (tapped with a push/pull tone pot) in the neck. Also use a Strat with a similiar pickup configuration.
I typically run the amp with all of the knobs in the master EQ section all pointing to 12:00 although I occassionally need to roll the low end off to about 10:00 in live situations. I control the overall tone by tweaking the dedicated Tone control for each channel. The voicing of this amp is amazing at these settings but the tone controls don't offer extreme swings in control. What they do offer is the ability to fine tune a great tone to the player's individual taste or guitar. The channel dependant Tone controls are fairly broad in the "Q" sort of like the tone control on your guitar - they cover a lot of ground. I have tried to find some really ugly sounds by dialing up some extreme tone settings and while the tones I found at these extreme settings were not always "musical", I wouldn't call them totally unusable either! This amp does an incredible job with any style at any volume and the compression characteristics make this amp feel really organic. Clean, mild overdrive, texas blues, crunch or high gain, it's in there. I don't want to slag any other manufacturers, but I haven't plugged into anything (bar none) that has topped the tone and responsiveness of this amp.

As far as reliability, I would have to say that this is untested yet since I have only had the rig for about 5 months. I have exchanged e-mails with Guy Hedrick on several occassions and he has been very responsive. We have a small (but growing!) Guytron user's group in my area and there is a loose, informal communication between many of us. The oldest amp I am aware of in this group has been going strong for nearly 2 years without a single problem (on the original tubes, no less). I get to hear that amp regularly since it belongs to the other guitar player in my band and I can tell you first hand that it still sounds amazing. As it stands right now, I have no reason to think that reliability is going to be an issue.

The amp comes with a one year warranty and as I mantioned above, I have had a few e-mail communications with Guy Hedrick and he has been very responsive to my questions and provided me with the information I needed. I have not yet had to have the amp repaired or serviced in any way as of this writing.

I have been playing for about 30 years and own several other amps by "big name" manufacturers. The GT-100 eclipses tham all. If this amp were stolen or damaged beyond repair, I would not hesitate to replace it. I haven't used anything else since purchasing it and really don't like the sound I get out of most everything else I own at this point. My biggest problem would be trying to find something else to plug into that I could live with while waiting for the replacement!
As far as limitations, I have heard one or two people voice some displeasure with the fact that the amp does not have a built in reverb. This does not present a problem for me as I have a dislike for the "springy" nature of spring reverb tanks (even the best of them) and I choose to use digital reverb units such as the Lexicon MPX-100, the Boss RV-3 or the Alesis NanoVerb instead. I don't use any other effects. I do use the send on the High level effects loop to get a signal to a Korg DTR-2 tuner but I do not return the signal to the amp.
When I was shopping new amps, I auditioned all the usual suspects. While many of them did a really good job at getting certain tones, none of them could match the versatility of the GT-100, in my estimation. For years I had wondered why no one had been able to make an amp that could do great clean AND great overdrive/distortion in the same unit. I was tired of having to either suffer with deficient tone or drag at least 2 amps to every gig. Thanks to Guytron, I don't have that problem anymore.

All tube 100 watt amp with two channels and two stage power amp section. The output section features a pair of EL84's first, and then a quartet of EL34's for master output sections. A design witch is completely unique to this amp! Effects loop with a level control. Each channel have more than enough gain, anywhere from spanky clean to out of control. I play out live 15 to 20 days a month and it plenty loud for the rooms I play. It even sound good at low volumes, but as with all tube amps it sound better loud !

I use Les Pual classic premium with duncan 59's, and it suits my hard edged rock with blues overtones quite well. When I tried the amp out first I used a Tele and Reverend Strat style and the amp sounded awsome with single coil pick ups as well. The amp delivers a wide pallet of tones from black faced sounds to all the valco, and english amps with Plexi authority. The high gain sounds are very smooth, which makes the modded marshall sound hard to aproximate, but the high gain sounds are much smoother which I prefer. This amp is so versitile it is a shame I only get to use 2 sounds live. I can't wait to record with it!

I can't say for sure, but I saw the amp at the shop it was built at, and the construction looks unbelievable. This amp is completely over built. I have owned it for 6 months and have had no problems>

I met Guy Hedrick when I purchased the amp. I spent a long time with him playing and talking about the amp. He is totaly into this amp and I would say he is behind his design 100%. I am ebarassed to say I don't know how long the warrant is, but I don't think that will be a problem. Guy Hedrick is a geniuos.

I have been playing for 19 years and this is by far the most impressive amp I have Ever owned. I just purchased a JCM800 2203, witch I love for that signature Marshall sound, but the GT100 can almost duplicate it an reasonable volumes. This only the second high end amp I have ever owned, but I got rid of a Marshall 6100 to get this, and have tried everything(Matchless, Naylor, Bogner, Riverra, Boogie, Fender custom shop amps ect) and it is by far the coolest amp I have played. If you want a well made amp that will get you Vox, Fender, Marshall, Valco, Ampeg, ect. this is the amp for you.

this amp does everything-extremely well! i play all styles of electric guitar, and this is the first amp i have EVER played in 34 years that has this capacity ! 2 channels-with master tone control for each channel. parallel effects loop -100 watt-head only- perfectly matched cabinet (2x12) - sounds magnificient w/ 2 cabs-able to achieve any tone at any volume (high,or low )-built like a tank- all tube. this amp is the amp of my dreams.the tones are truly magnificient.

i use this amp with a steve morse music man/ernie ball guitar ,as it's the only guitar i have found with the veritility and tones i want. i work with all styles of electric guitar. the amp is very quiet- even with super high gains clean sounds vary from a slightly compressed twin to ac30 to fat tweed to fat crunchy marshall the hot channel pretty much picks up where the low gain channel leaves off- slight crunch-to thick marshall to fat soldono.

i have been using this amp regularly now for 16 months .... it has not skipped a beat.

i talked to the builder (guy hendrick ) about checking the bias after 6 months. he was very responsive, and helpful. the amp has a one year warranty.

i have ordered another guytron in case anything happens to this one ! this amp out performs any other amp i have ever tried- at any price .