THD Flexi 50 Head

This is an incredibly versatile amp. You can read the features below ... Plenty of power, depending on the tubes you choose. Paired with the THD cabinet and a power brake, this thing is unbelievable!

I have mine set up as a blues amp...with a little bit of edge. I use my guitar's volume control to push it into distortion. I like the stock tubes ... but swapped the V1 preamp tube for a NOS RCA AT7. Great sound.

Only had it for a short while, but tubes are easy to replace ... looks solid!

Great web site... check below for a great forum...

http://www.univalve.net/forums_new/

By far the best amp I've ever owned or used for that matter.

Single channel
Volume, Treble, Mid, Bass and Presence controls
Switchable Master Volume
Switchable Boost function with gain and tone controls
Bright switch
High / Low input switch
Effect loop
Impedance switch for 2,4 and 4, 8 and16 ohm cabinets
Allows for substitution of virtually any power tube
Easy to adjust power tube bias. Individual bias pots for both power tubes with outputs for a multi-meter.

I have used this amp with: An '89 Strat with stock pickups and a Seymour Duncan ? pounder at the bridge.
A Squire Tele Deluxe loaded with Seymour Duncan JB and Jazz pickups and coil-taps.
An Ibanez S470 with stock pickups
A parker P-38

My musical style is primarily classic rock with occasional, semi-competent safaris into blues and jazz.

I too wanted to love this amp but I think we are still just friends at this point. Here is why:
It all started when I bought a 70-something Traynor YBA-1. It sounds great, I don?t need to use any pedals. But I know the Traynor is going to catch fire any day now so I bought the tank-like THD Flexi in hopes that I could replace my beloved Traynor with a modern and ostensibly more reliable amp.

First off, the Flexi-50 really responds differently with different power tubes so I will treat each individually:

EL34s: Clean, low volume / low boost sounds pretty good. Playing Jazz with a loud drummer is damn near impossible. At high volumes there is very little headroom before serious power amp distortion, nasty compression and clipping take place ? at least for single notes. It did sound REALLY cool playing rhythm in open G on a bunch of Stones tunes. However, on single note runs at high volume / high gain it basically sucks a** (in my humble opinion)

6L6s: At clean or slightly overdriven settings it sounds great -- the amp has a wonderful clean / slightly dirty tone. Think Stevie Ray or maybe Ronnie Earl without reverb. Switch on the neck pickup on a Strat with the boost and volume set at reasonable levels and you should be able to nail a pretty cool blues tone.
It also sounded pretty good at high volume / high gain with the 6L6s but not as good as my Traynor YBA-1.

6V6s: Sounded pretty cool in my bedroom in both clean and high gain modes but there wasn?t enough volume to compete with a spirited drummer. The only time the master volume feature seemed even remotely useful was with the 6V6s loaded

Summary:
* I agree with others that the overdrive can definitely be ?farty? sounding and over-compress. 6L6s seem to help.
* I also agree with others that technique does seem to count for something with this amp.
* The amp has a cool clean tone and good crunch tone for classic rock rhythm guitar. Forget about nu-metal.
* The amp will cut through a loud mix
* The amp seems to sounds cool with an overdrive pedal (I have a Boss SD-1)
* With its boutique price tag, the Flexi-50 should have a much better overdriven lead tone.

I have only owned it for two months. I appears to be very sturdy.

N/A

I have been playing for 30+ years.
I have owned or played several Mesas (no thanks), A silver face twin, a Peavey Classic 30 (great amp) and a vintage Traynor YBA-1 (near nirvana)
I would probably buy something else if this was stolen.

I purchased this amp new in the beginning of 2005. My intention was to find something a little more flexible that my Marshall JCM2000, which I have been playing for the last few years. There was not a dealer in my area at the time, so I bought this over the internet based on the rave reviews this amp has been getting. This is a single channel amplifer, but with quite a bit of control over that one channel: including foot-switchable Master Volume and Boost features, along with the usual EQ controls. This is an all-tube amplifier designed to allow the user to try different combinations of input and power tubes. I was particularly drawn to this amp because of this ability: to try out different tubes in order to fine tune my sound. This amp also has a feature which makes it easy for the user to adjust the bias of the power tubes. As for the single channel feature, the THD website describes using only the guitar volume for "cleaning up," the guitar signal. I did not find that practice to work particularly well for me. In retrospect, the THD statement about the different channels on multi-channel amps sounding "more or less the same" may be a bit self-serving, as THD only makes single channel amps at this time.

I play in a classic rock band. My primary guitars are a stock Les Paul Standard with "Burst-bucker" pickups, a Strat with Dimarzio "stacked" single-coils, and another Strat with Lace Holy Grail pickups. I would say that the lead guitar sound I shoot for the most runs along the lines of Journy/Boston/Santana/Mana, etc. It is in this capacity for lead guitar sounds that, in my opinion, this amps falls sadly short. I hate to say this. I really WANTED to love this amplifier -- after all, the reviews are great, so the amp must be awesome, right? Right out of the box, plugged into an Avatar Speakers 2X12 with vintage Celestians, this thing sounded horrible. I was trying to get a sweet, over-driven, boutique amp sound, but this amp was not about to give it. The distortion sounded fuzzy and synthetic, like cheap transistors. It seemed to have a lot of buzz to it, like a Marshall with the presence control pegged to maximum. Strangely, the initial pick attack to the strings was very loud and percussive, but the signal seemed to drop off faster than expected, as though a compressor was engaged at the time of sounding the initial note, but then disconnected as the string begins to vibrate. Reducing the "CUT" control helps minimize this, but not enough. I called the folks at THD; they felt that I would have much better performance if I incorporated a Hot Plate into the set-up. One 8-Ohm Hot Plate and $279.00 later, I tried it again, but the amp was not any better. The Hot Plate seemed to increase the hiss. Another phone call to THD, and I was swapping out the EL34s for 6L6's. Actually, this smoothed things out a bit, reducing some of the hiss when the Gain and Input Volume were at 3:00 O'Clock or better, but I still didn't think it sounded very good at all. If fact, my cheap practice amp, a VOX ADT30, sounded much, much better. More phone calls to THD resulted in Ed giving me some recommended control settings over the phone: while I very much appreciated his time, the amp still sounds very strange to my ears: a percussive intitial string signal, lack of sustain, and a tone rife with hiss (or should I say lack of tone?). I have now tried the amp through a different speaker cabinet, but this does nothing to improve the performance. There is now, since the time of my purchase, a THD dealer in my region. This dealer says that "this isn't a high-gain amplifier;" he recommends running the amp clean, and putting a high-quality overdrive pedal on the front end for that "harmonic distortion" lead guitar sound. That would probably work to some extent, but at this much money, I would expect this amp to sound a lot better without any effects. The best sound I have gotten out of it is a fairly clean blues sound (think SRV's clean stuff). By itself, I have not gotten this amp to give me the harmonic-distortion, violin-like sustain that I was hoping for. Maybe I got the lemon. I cannot account for the fabulous reviews this amp gets, unless these folks are just playing clean blues and jazz?

This amp has not broken on me. It appears to be very well made. I would gig with it if I liked the way it sounded.

The customer support, despite my problems with getting this amp to sound decent, has been wonderful. I have spoken directly with Ed and Andy up at THD, and I do very much appreciate their time even if the amp isn't working for me. On my last conversation with THD, however, they were kind of pushing me to try this thing through the THD speaker cabinet, and I have to say that I felt frustrated that the solution to the sound quality problem kept being to buy something else (tubes, Hot Plate, etc.) Still, these folks have been very generous and patient with me over the phone. I can't imagine being able to talk to an engineer over at Marshall, for instance!

My overall rating for this amp is very low because, fundamentally, I never got really good guitar sounds out of it. The name and description of this amp implied something much more versatile than it actually was, at least withn respect to the one I bought. I would like to close this review with some advice to others that may be thinking about buying one of these: First: buy it from somewhere that you can return it (Musiciansfriend, etc.). That way, if it really doesn't work for you, you can return it. Second: really assess your performance styles and determine if a single-channel amp is going to work for you. I think that a lot of rock music is far better suited to a channel switching amp. Third: forget the hype. Forget the reviews. Forget what I write here, and forget what the other guys wrote. Plug in your guitar find your sounds and play it. Close your eyes and listen, really listen. If it really works for you, then great! If not, then return it, and don't worry about being judged as a lesser player if you can't convince yourself to feel the same way as previous reviewers may have. After all, art is subjective. As for myself, I have found a much better solution with a Mesa Lonestar, but that will be a different review......

Visually the amp looks terrific -- watch those valves glow --E34's on this come as standard. It is pricey but offers a tonal pallete that sounds good to my ears. I was wary about gigging with this though as only a plastic cover is offered -- I'm sure some manufacturer will have a flightcase for it. I opted to buy the THD speaker enclosure as it's about the best reference monitor I've heard (I tried it with other heads). All the controls work well together but do take time to find that sweet spot. I like the idea of a single channel -- I've always found that most amp manufacturers compromise somewhere on their multi-channels -- either the clean or the dirty suffers. The ease to change valves makes this a good choice for the recording guitarist -- go brit or yank armed only with a multimeter. The provision of 20w or 50w is good too as this is seriously loud. It'd be nice to have a footswitich to bring in pedals in the loop -- too much footstomping for me.

The sound. First try in the shop, I sounded really messy. This amp takes no prisoners when it comes to sloppy technique. I immediately slowed down and tried to interact with it. This amp really does raise the bar --although I have found it needs an overdrive/distortion pedal to take it into this millenium's style of heavy tones. That's not a criticism -- it's just that it's hard to go from crystal clean to crunch to squeal. This amp does it all -- but it does require careful setting up and thinking ahead. I've found a Boss DS1 works well and a hotcake. This needs to be heard in a band environment because that's where it really cuts through like no other amp I've had. However, if you play sloppy -- this will exaggerate those errors. It might just help your technique!
I use a Fender Strat with duckbuckers and a JB along with a custom built guitar made many years ago by Ian Watt. For the first time I can really distinguish between the pickups.

Tubes look easy to replace and so far it's not broken down on me. I always take along a Boss GT6 I can plug into a PA if it fails -- doesn't supply the sound of the Flexi -- but it's a safe back up.

Before I bought this I harrangued the customer support people about availability of parts and servicing and they were very helpful.
I really must say they've responded each time to any queries -- no matter how stupid sounding.

I'd buy another if this was nicked (stolen) I love it's apparent simplicity -- it's about the guitar and how it interacts with the amp. For example my guitar sounded poor plugged into a Peavey Joe Satriani model -- but the Ibanez Satriani guitar sounded very good.
With the THD all the guitars sounded good. I tried Mesa Boogies -- Peaveys -- Marshalls and settled for this.

Taking into consideration that it is a single channel amp, it does have a good amount of features, but some of the features aren't really as useable as it first seems. For example, the footswitchable boost looks good on paper, but in reality, the volume difference is to great to be of any use. I would have liked to see the ability to switch only the input gain switch via foot (now, you can only switch it and the boost simultaniously). The amount of gain that the input gain switch adds is just the right ammount for lead boost.

This can be an incredible sounding amp, or nails on a black board, depending on the player and playing style. For those used to modeling amps, or all in one FX boxes, this amp may not suit your needs. It can sound immensly better than the modelers, but it takes more work to play (as with any real tube amp). Where on a modeler, you can pretty much hit the strings any way you want and still get the same sound, with the Flexi, dynamics play such a big part of it's tone that you actually have to play your instrument.

This is the third THD I've owned, and I've never had a problem with any of them.

I've heard great things about their support, but I haven't seen it first hand. I've tried e-mailing, and never got a response. I see that they are now selling to Musicians Friend. Perhaps the company is getting a little big for their employee base?

If you use real tube amps, and are looking for a single channel amp that sounds like what you think the best hot rodded plexi SHOULD sound like (but never does), then you'll be happy.

If you're playing a Pod or digital stomp box, move on. You won't like the amp, because it sounds and feels like a real life tube amp.

the features are fine.... did'nt want a modeling amp tried them all.... the master vol. on /off, boost/gain,bright,
hi/low all are real usable

the amp sounded great at home...but on stage WONDERFULL.....It cut throughthe mix with some of the best tones' I've played in 40 years...... (oops I dated myself) Im using a marshall 2061xc w/ 2-12 celestion gh speakers...Thanks ED, for the advice (it's Greg from Flag)I play rock n blues it's great for my styles

My amp had a faulty bridge rectifier crct...THD took care of it pronto....so I did'nt miss a gig....and this was during the NAMM
show week prep...Thanks again ED

Customer Support is fantastic readusual last remark

I've been Playing for 40 years... I own 1774x LE Marshall 18 watter
Custom shop LP,Custom shop 336 Gibsons , a Don Grosh Strat, and a Vox tonelab SE for effecs. Tryed most everthing over the years.... Davoody too..Frank Gambale was my instuctor (LAMA 96')...If it was ripped off I would get another...This AMP ROCKS

Nice. It is basically a one channel amp with two different footswitchable flavours but I regard this as a two channel amp for easier reference. There are two gain structures that can also have two different volume levels. You can either have a clean sound and a dirty rhythm then switch to a pedal for solos. Or you can have two rhythm sounds + use a pedal for solos. Or you can dial one channel for rhythm and the boost channel for solos... And it works. You can dial in a darker solo tone or a brighter one... Go and see the description on the THD website.
The best feature after the sound quality is the bias possibility. I can use various tubes, even if not matched and bias the amp all by myself and I am no technician. Would never dare doing so on other amps. Then you can also disengage the master volume circuit and have a non-master volume amp ! Having enjoyed several non-master volume amps in the past this was a very important factor for me. For now I use the Master Volume as it is a very well executed design that doesn't take away from the good sound of this amp. Switch the Master Volume out of the circuit and the amp shines. You can also use the footswitchable master volume as a volume boost for solos.

Awesome. Use it mainly with Strats (single coils and HB in the bridge). Works wonderfully in a band context. You are never too loud and always cut through. Has the right frequencies tuned in. Great for classic Rock, Blues or Blues-Rock. Even for Hardrock. For Nu-metal, I would use it as a good foundation and add some pedals in front. You can use it with various cabs and speakers as I did with good results. Don't judge this amp solely by playing it in a store or at home. Take it on a gig and you will be surprised as to how well it responds to your playing dynamics and the sound of the other instruments in a band context. You have to turn it up to get best results.

Built like a tank. FAA approved technology it seems! Not point to point, but a very thick PCB well supported and well built with thick copper traces. Tube sockets and pots are chassis-mounted. I don't expect any probs in the near future. Should last a lifetime. I bought the amp only 2 months ago, but used it on a few gigs with no problems.
I had many Marshalls new and old break down on me. Never use without backup though. You never know. There are tubes inside. But you can easily change them and rebias and off you go.

They seem very nice and responsive. I emailed them a few times directly with questions and got quick answers that were to the point.

Tens everywhere ? Well for me it is the best amp I ever had. Because I have many variables to take into account: sound, built quality, size, bias, tubes etc. The Flexi with a 1x12 cab, a Strat or a Paul, plus my collection of pedals is the ticket to go. Sounds huge and cuts through. 3D tone and dynamics. What else do I need ?
I have had the following amps and always had a complaint: Budda Superdrive combo (best sound but bulky and not flexible enough), Soldano Caswell (great sound but not my cup of tea), various Marshalls (classics but not reliable enough and needed the 4x12 to sound right), various rack gear, combos and heads... I feel like I will not look any further for amps. I can concentrate on my playing and maybe add some pedals to get different flavours now that I have the right foundation.

What they said

Using mostly strat type guitars.This am is very touch sensitive (maybe too much for some judging by some reviews)and dynamic .It has the best cleans of any amp I have ever owned,and also the sweetest and fattest lead tone!!This is a very good amp for old school (do it all with the volume knob)kinda guys perfect for blues,classic rock ,country and jazz(when not to much head room is needed)
The huge lead tone is great for the shreader solo kinda thing,But

This amp will not do Nu metal,or would not be first choice for old metal.
I give this amp a 11,and if I could I would give it a 37 to make up for all the guys who couldnt handel it.

Built like a tank

The best

I have had alot of amps including 5 Fenders,6 Boogies and 11 Marshalls and the FLEXI has a feel and touch that seperates it from all other amps in the price range.
Not for beginners or Nu metal.

I won't go through the trouble explaining all the features, but there are lots of 'em. I bought it brand new mid 2004 and still have it but will try to sell it after the christmas season when people have money.

I really don't understand all the great ratings this amp has gotten here and on other forums. The flexi is absolutely horrible. When driven hard at gig levels, the distortion is harsh. The boost then compresses the hell out of the amp and squishes the notes too much. The master volume is also not very good. by the way, I'm not the only one with this opinion-the others who have played this amp feel the same about the amp. The amp excells at mid gain levels, but other than that it sounds like *hit.

looks dependable.

never talked with them. One of the employees is on the forums all the time and I suspect that's why people aren't cutting this amp too pieces the way it should.

I've been playing for over 25 years and play in 2 cover bands (classic rock and contemporary pop) here in California. I have many guitars but usually play my prs mccarty and custom22 at gigs. I have 3 old Marshall heads, a VHT CLX (great amp!!), and a rack set up which I normally use for gigging. After I got the thd, I tried using it at rehearsals for my classic rock band along with a avatar 2x12 and I hated it. I should have tried this amp out before buying it as this amp is not very good. I gave up with it and put the amp in my closet. It's harsh and just doesn't sound very good. It sounds nothing like a Marshall (I have a 72 and 74 superlead, and a 78 100 watt masterlead to compare to the thd). I have also played a Univalve and Bivalve-both amps are way better than the Flexi. I just can't recommend this amp.

My amp has not arrived yet, it is on order but I have had a number of these cross my bench and have spent many hours with them.

Most if the features have been mentioned here in other reviews. I will take a moment to approach things from a bit of a different angle.

The late 1980s saw some great amp builders come on the scene. Matchless, Dr. Z and THD were a few of them.

THD came to my attention though a friend, Aspen Pittman, founder of Groove Tubes. Now you may love or hate GT but the point here is that Aspen has one of the most extensive amp collections around and he does have a great ear. When THD came out with their tweed bassman reproduction Aspen commented that is was perhaps the best sounding and playing tweed bassman he had ever heard.

Years later I saw an amp called a Univalve. I am involved with tubes in my line of work and this amp seemed to be just the thing to actually compare tubes easily. Too often we rely on tests, traces and specs where these things differ more in the actual tone aspects of the tube. I bought a Univalve from The Amp Shop in So. Cal.

My UV was one of the earliest. I met with Andy Marshall from THD to perform a change to make the amp more reliable. The amp had been 100% reliable for months and this change was something that would fix something "that could happen" but rarely did. It never happened to me. In the process of making the change an etch had to be cut. This opened my eyes quite a bit. You cannot tell all that easily the thickness of etches visually. Once you try to cut one of these THD traces and realize you need a power grinder you realize how thick the etches and substrate are. The construction of these amps is about as perfect as it gets. THD uses proper technology to it's best advantage where it is best applied. Chassis mount sockets with flying hand wired leads to the board. Modern resistors rather than carbon comps which are not as stable and are more noisy.

The Univalve became a primary studio tool. One feature overlooked by far too many folks was the great transformer isolated line out. I use the UV as a preamp quite often. Get the gain and tone from the UV and take it's line out to a Fender Twin Reverb and you can have a pretty amazing rig.

The Flexi 50 - No surprises here. I first saw and heard this amp at the 2003 NAMM. I was very impressed. I told the THD folks I wanted to get on the list for one. They were not going to be shipping for a while as the tone stack was not finalized. Andy and Ed at THD don't let things out until they are completely satistied with the end result.

The amps has the features most people would want and that most folks would find useful. I am a big fan of the THD line outs. They are one of the few folks that seem to know how to do this in a way where it works for the applications I need. I have used the UV in very large live environments. Mic the cab and run to one channel and take the line out to a second channel and you can cover a lot of arena area.

The dual voltage is a great feature for 6V6 use.

The amplifier is fully featured yet not messy or complex.

I have used the Flexi 50 amps in a number of environments - live work, studio work, etc.

This amps is not trying to replicate a specific amp. I guess when folks hear Flexi they think Plexi. This is sort of a yes and no. This amp covers the tones and bases of the early era Marshall amps really nicely. BUT >>>> it can also cover bases other than just the "Marshall" tones. With a 12AY7 in V1 and a nice set of 6L6 output tubes and a 4x10 cab you can hear tweed bassman tones and character. With a 12AX7 in V1 and V2 and 12AT7 in V3 with those same 6L6 tubes and an open back 2x12 you can cover Fender tones pretty darn nicely.

This amp does not "copy" other amps. It is a very versitile amp that lets you move to the character of other amp types due to it's design and architecture, tube change ability, etc.

On cabinets by the way, I have used these amps with 1x12, 2x12, 2x10, 4x10, ported, open backed and closed back cabs. Some of you know the other amps and cabs I have and most of those cabs have been used. I have strong personal preferences, and I think Ed at THD has made comments that I am more a "Fender guy" than a high gain guy. Yup, I grew up on Fender, Marshall, Vox in the 60s and have sort of stayed that way but I work with a lot of folks that are quite "over the top" when it comes to gain or walls of cabs. These days the walls of cabinets are going away due to the "Nashville backline" where control and tone are important in live performances. Now one needs a great cab that may be out of sight. I want to just take a second here to say that my two favorite cabinets in the universe are the Dr. Z Z-Best and THD 2x12 cabs.

This amp is very versitle in the "sound" area and covers more bases due to it's tube swappage ability than most any other amp. Many folks think that you can switch 6L6 to EL34 in other amps with a rebias. Well, sort of yes and no. Technically yes, but the amp's output transformer was generally optimized for a specific tube and these two tubes are different. So how can this be done by THD? They have their own design transformers and these are quite different than convention iron. When you move a convention speaker tap from the 4-8-16 ohm positions, you are using a smaller portion of the transformer and the winding setup is not the same. THD transformers use the full core at any setting. Perhaps this should be mentioned as a "feature" but it does affect the sound.

THD also makes transformers that you can buy for your non THD amp. They also make something called the reactive rectifier which is a very cool piece of gear that many folks do not know about. Their Hot Plate and Yellow Jackets are already well known.

If you do want over the top metal sounds just grab an Extreme III pedal and have at it. The amp is very pedal friendly.

I expect this amp to give the same reliability as my Univalve. My UV goes to many gigs, concerts, and studio sessions. The UV has been used from day one many times per week, has been flown over most of this planet, used as a stand alone amp and as a preamp. It has injested more "suspect" tubes as a test device without propblems. It has never had a single problem - EVER.

If there are folks thinking that only a PTP amp can be reliable think about a Navy F-18 pilot crashing onto a carrier flight deck every day. These pilots are surrounded with PCBs that are lighter surface mount technology with micro etch work. Basically, a well built amp is a well built amp and a badly executed PTP amp or PCB amp is going to be a nightmare.

THD support is legendary. Ed at THD is also a killer player and is more than happy to offer his advice on just about anything even if it is not a THD product. Ed is also pretty terrific on recording techniques and live rigs. Andy Marshall is a super fellow too and seems to surround himself with great folks from the receptionist outward in their staff.

I have been playing since I was eight. I am now 55. On my other gear it is basically Fender, Marshall, GT, THD, Victoria, Mesa, Dr. Z, and more. A lot of this is on my business website at Guitar Amplifier Blueprinting. When I am not at GAB I am at GT (Groove Tubes) where I run the SAG (special applications group). I see a lot of amps cross my path, maybe a bit more than the average fellow out there.