THD Flexi 50 Head

I've played 40 years and owned a dozen amps. This is what I've been looking for my whole life. The best Marshal tone I've ever wanted with lower lows, higher highs, and a low midrange with mind blowing complexity and harmonic content.

Simply breath taking. Tons of headroom. Id NEVER give this up. THe clean boost is the best I've heard. Really exposes the flaws in my pedals.....Its like a science lab.

Built like a tank. best build Ive ever seen.

The best. I called three times about tube choices and they were totally helpful!

I play, rock.blues, jazz, funk. It does it all. Totally dynamic and responsive to my guitars volume control.

THD Electronics Flexi 50 head. #214, Extremely versatile controls, volume, treble, midrange, bass, bright switch, input hi/lo switch, boost switch with gain and global tone, master volume with bypass switch, cut (presence) control, effects loop, line out with level switch and control knob, two speaker jacks, impeadence switch, external bias check points with adjustment controls, switch input to high with boost switch, footswitch jacks for the master volume and boost circuit, and the designer, Andy Marshall's signature with plexiglas cover right on the back, cool huh? the external bias contrrols alone make this one woth a 10. How much would you save a year on trips to the amp tech, just for new tubes and a bias?

I installed (2) Groove Tubes GTEL34M's for the power section and the pre amp now consists of V1 GT12AX7C, V2 GT12AX7R-2, driver is a GT12AX7R, all new. With the boost engaged this combination delivers a better than authentic JCM800 tone. Turn off the boost and there is that sought after Plexi tone. Putting a 12AT7 in V2 as recommended by the manufacturer yields a chilling early rock tone anyone would fall in love with. Very responsive amp, will make you a cleaner player. No where to hide sloppy chops, this thing is as articulate as any amp out there, note clarity is hands down the finest I have heard. Truly a quiet amp, even at extreme settings, it hums just enough to let you know it is ready to erupt at your command. All of the various controls and switches are dead silent, and very usable. Nothing here you would look at and say "why?".

I have only had the amp for a week now, so I am going to be honest and say no opinion. But I will say it seems to be built to survive. Everything is seems to be of the highest quality, it looks, feels and sounds very solid. I really expect years of trouble free service, how many used amps can you feel that confident about.

Here's one you never heard before. I purchased this amp used from an online auction site(yes, the E word), and thought it was not going to include the manual. I emailed customer support telling them my dilema, and requested a manual. Les than three hours later , I had the file sitting in my in box with friendly reply. Wow, fast you say, huh? Now, this was on SUNDAY afternoon. Customer support, on sunday? It is true, cross my heart! The manual was included with the amp, just to give Music Go Round in Novi thier credit, thier customer support is also top notch. Thanks again guys!

I went through the disappointment of trying to get my sound from large company produced budget tube amps, Crate(bv60h), Peavey(windsor,valveking), Epiphone(socal50h), Marshall(avt50h). The one thing they all share in common, when really pushed to loud volumes the sound just goes to mush. Why make a 50 or 100 watt head that only sounds good a quarter of the way up and then just starts a downward spiral in the muddy mess the louder you go. Then I decided to get the amp I originally wanted but Thought was too much money to spend. Well, I spent triple the new price of a Flexi trying all the others. After playing this amp for a week, I realize how expensive this lesson really was. This amp is by far the most versatile amp on the market.

All this info has been covered elsewhere in these reviews. This amp tries to cover lots of ground, but most of it I consider a waste. For all intents and purposes I consider it a 2 channel amp, but I was happiest when I treated it as a non-master volume single channel amp running on full power. The clean settings give you wonderfully sparkley tones, but I don't care for the overdrive at all. Obviously many of the reviewers like the overdrive, and it's there if you want it. One thing nice about this amp is it's LIGHT. That's important when you get tired of lugging 70 lb. combos around.

Like I said, the clean tones are great. Set it for full power, non master volume, and you get glassy, chimey, and harmonically rich tones. Very pretty. Sounds great both with my Strat or my Les Paul. But that's where it ends for me. All the other bells and whistles are just a waste. The over drive (boost)is harsh and not musical at all, in my opinion. Very uninspiring. Use a good pedal if you want gain. The master volume settings were equally unimpressive, since I don't care for the amp's overdrive sounds. I tried all sorts of different tubes and the results were always the same. That's too bad, because I bought this amp hoping I'd be able to achieve nice tube overdrive at a lower volume. The overdrive tones on this amp never sound good. I like the clean tones, but I have to knock it because the overdrive sucks.

I owned this amp for about a year before selling it. It seems to be made very well, and THD has a great rep. I never had a problem, and never had to get it serviced. Never gig without a back up. You may have the best amp in the world, but tubes fail and soldered wires can disconnect and nothing lasts forever.

THD has a great rep, but I never dealt with them.

I've been playing 20 years and have been through all sorts of amps. My current keeper amps are a Fender Vibro King, Whitney MV34, Bassman Reissue, '73 Princeton Reverb, and a Musicman 130-212. I was very disappointed in the Flexi-50, especially after reading all the glowing reviews.

You can find a better description of the features else where
But here are some things you should note:
Tube bias system- use any power tubes you like
Tone controls- more like a 3-band eq, makes it so much easier to dal in a specific sound
Master control-gives you four fot switchable sounds:
1. clean rhythm
2. clean lead
3. rhythm overdrive
4. lead overdrive

Wish it had:
2 independent channels
Reverb
No Cut control

I'm not going to compare this amp to any other amp, because the majority of us, like myself, have never played a vintage marshall, vox, or fender. Those amps are for collectors, not players.
i am using an '81 les Paul studio straight into the amp, and have a 2x12 Avatar cabinet w/ celestion lead 80's.
This has an outrageously clean tone. I prefer the ton controls set to a mid scoop which gives it a bell like, even acoustic qualities. 6L6's and 6V6's have the best clean tones. Use 6L6's if you need more head room.
EL34's and 7581's are better for overdrive.
The boost control is not another channel, its a volume increase.
so if you want a nice crunch tone, you have to peg the boost and switch in the master to control the volume. to get more distortion, all you have to do is turn up the volume and turn down the master. If you have the volume past three, it will start to compress which is distracting when you try to play fast.
Your speaker choice will be crucial to your sound. if plan to focus in on a overdrive setting, you may want a greenback or a V30. The lead 80's are very clean and very articulate, so they match with the flexi because it has the same qualities. My favorite over drive setting w/ the lead 80's is "smooth upper mids" setting in the manual, basically a mid boost.

Built like a tank, weighs a ton
everything is well thoughtout on this amp
becareful of liquids because the chassi is exposed to this due to the holes in the role cage.

Great.
talk like humans to you
respond quickly on emails

Cleans, cleans and more awesome cleans make this amp a winner in my book.
If you want footswitchable distortion, get a Mesa. dont bother with this amp.
If clean is what want, go wih amp, you will not be disappointed.
it really says want it to say when your playing.
Check out Avatar cabs if want a decent cab with nice speakers.
the flexi is a truely awesome and revolutionary amp.

Footswitchable Master volume & Overdrive boost. Bias controls on back mean you never have to buy tubes in matched sets again. Speaking of tubes, put pretty much whatever you want in this sucker! I've tried EL-34, 6L6, and one of each and it sounds great with all of them. Can't wait to try some EL-84's with my new Yellow Jacket converters! 50 watts of sweet, totaly configurable tube power. Half power switch drops it to 20W for even more FLEXIbility. Use a wide selection of cabinets too. I really miss not having reverb, but the other features of this amp almost make up for that.

Marshall Plexi tones to die for. Distortion totally controllable with master vol & boost. Sky's the limit for sounds and tones on this baby...Marshall, Fender, Vox and more are all there with a quick tube swap and re-bias.

A sherman tank should be built this tough!

Ed Genaro and his supports staff are the best I've ever dealt with...barre none! Nead a manual, PDF emailed to me. Problems with some yellow jackets, replaced no questions asked. Questions to be asked...answered promptly. I can honestly find no fault with the customer support...a few other companies should take notes here!

I'm normally fairly critical, so hats off to these guys for making the best amp I could find at a really fair price (not cheap, but very fair).

All knobs and switches offer considerable tone and dB shaping. LOVE the individual bias feature. The only change I'd make would be to make the input gain footswitchable.

This amp has a unique voice, which is probably more reminiscent of Marshall in it's hey-day, but more refined. I've owned Marshalls from the '60s, '70s and '80s, as well as a handful of Fenders, a couple of Boogies, a rack rig with an ADA MP-1, and a few "boutiques." Currently, I have 7 amps, including a handwired Marshall, Vox, Fargen, Fender, etc., and I have to say that the Flexi is the one I grab for EVERY gig, week after week, regardless of whether it's to play classic rock, funk, blues, or jazz.

I have a Les Paul Standard, a Strat, a Tele, and a couple of other guitars and use a mix of Duncans, Texas Specials, and Fralin pickups. I'm a bit of a pedal nerd with a decent collection of overdrives, treble boosters, and distortions built by Keeley, Fulltone, and other "boutique" brands. I also have used a wide variety of tubes in this amp, both new and NOS. The point to all of this, is that despite the subtle variations created by all of these things, this amp always sounds great. Does that mean that it will, or that it should, be perfect for everyone? Of course not, however, if you understand it's niche and then spend some time with it, you'll be rewarded. It took me a while to understand the preamp design, the unconventional controls, and so forth, but once I did it went from a nice sounding amp to "the sound in my head."

To me, these are the tricks to this amp:
1. It sounds best with the "boost" section on all the time, and thus I don't use the footswitch. I'd imagine that gain freaks peg the boost control, but I find that it works best if you back off of it just a bit.
2. You have to use the volume control above 12:00...I prefer it at 3:00-ish. Above that you may find it to break up and compress sort of like a fuzz tone, so again, pegging this control doesn't work for me. This amp is very much about smacking the output, so cranking the volume (within it's "sweet spot") is crucial...thus it's best to use an attenuator for reducing volume (except where 20 watt mode and subtle reduction of master, boost, and cut controls can sound great to reduce volume by, say about 4dB).
3. Keep the bass control down.
4. Most room eq-ing is done with the cut control.
5. The master thins it out too much for me...a hotplate is better (however subtle master settings are nice to add some bite).
6. This amp is capable of a fair amount of high end...thus I don't like it as much with Celestion 75s or V30s...better with H30s and Classic Lead 80s.
7. Like any amp, this front end likes some pedals more than others. Likewise, it may require different settings on pedals and guitars. It is highly sensitive, thus very dynamic, but it will also reveal some things you probably didn't hear with other amps.

Excellent! Really heavy duty. No problems.

Superb...really nice and helpful people. In addition, the users forum

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

has been very helpful in tweaking it to taste.

I've been playing about 30 years, and for the last two, this has been just about the only amp I've used. The Flexi-50 is appropriately named...I play a wide variety of gigs and venues, from weddings to outdoor festivals, and have never had a problem dialing it in. Simply an excellent value.

My Flexi is an 05. I play a number of styles, from heavy space-rock to jazz, to blues on occasion, to straight up STP style rock. This thing covers them all. The ability to use any kind of power tubes with this thing is incredible. It's amazing how the character of this amp changes with tubes. I use this head in small to medium size clubs, and I've used it on an outdoor gig once. It handles every situation just fine. I have to say that I always use my tone for every type of style I play. My pick attack, my guitar, and other factors in the way I play change according to the needs of the moment. This amp doesn't have a ton of knobs, channels, or options on its own (unless you count being able to use any type of power tube or preamp tube and completely change the character of the amp), but it is the perfect amp to use as a starting point to add your stompboxes and other accoutrements.

The ability to rebias in a matter of minutes yourself will save you a TON of money, and make your tubes last much longer.

I use a PRS Custom 22, a Hamer USA Studio Goldtop, and a USA Hamer Artist. I also occasionally use a Japanese strat and tele. It handles all guitars equally well. You know how they say that tone is in the fingers? Well, I believe that's true, but I think your equipment can either let your tone come through, or squash it and hinder your creativity. This amp is one of those that lets your tone come through. It's incredibly sensitive to the subtleties and nuances of your pick attack, your touch, and the type of pickups you have. In addition to all that, it sounds like freakin' BUTTER. Rich, complex, and a depth that I've not heard in an amp at this price.

It has plenty of clean headroom, though you can change that with a set of power tubes and a different driver tube. I've been able to get very convincing Fender tones, Marshall tones, Vox, Tweed Fender, and a bunch of others just through changing the tubes and resetting some of the switches. If you want to hear the difference between a NOS tube and a current one, this amp will REALLY let you hear the difference. Here's the thing- this amp, in and of itself, doesn't do the channel switching, clean to blistering distortion at the touch of a switch thing. It is more geared toward those who like to turn an amp up all the way and use the guitar volume knob, or those who like to run the amp clean and add pedals. I am one of the latter.

The tone controls are unique in that adjusting one doesn't affect the others. They are incredibly responsive, and you can get a wide variety of tones with a bit of twiddling. The one downside is that the amp is very, very bright. So much so that I actually run it with the treble nearly off. It doesn't matter, I still get the tone I need from it.

The amp is incredibly quiet. Even in my house, where I don't have a single grounded outlet, it remains quiet.

I would gig without a backup with no hesitation. Nice to see a well constructed circuit board amp. The chassis is incredibly tough, and it's obvious that a lot of love and care was put into the construction of this amp. I have never had a problem with it, it has never so much as crackled. Considering the quality, I expect that it won't require service anytime soon. I got to meet the designer of the amp, and he told me that he hopes this amp is the amp that people consider a classic 25 years from now. He hopes it'll be the workhorse that people continue to gig with for years. You know, it says something when other amp companies have postings on their website touting the quality of THD amps.

Every email I've sent has been met with extreme courtesy, and quick response. Ed DeGenaro even called me at home to discuss a concern that I had, which turned out to be nothing. This is a company I'm happy to support. It's good to know that they not only appreciate your business, but work to make some of the best amps money can buy.

I've been playing for 17 years. I researched buying my final amp for 2 years. I've owned Carvin, Mesa Boogie, and Ampeg, among others, I tried some other great amps- Bogner, Rivera, Carr, Victoria, Soldano, Bad Cat, Orange, and others. I was seriously impressed with all of the above, and it was a tough decision, but I'm happy with the one I've made. I got this because of its simplicity combined with its versatility and just all around great tone. The one thing I wish it had was an option for reverb, but I don't miss it enough to let it bother me.

If it were stolen, I'd definitely buy another one. I couldn't be happier with a purchase. I hate to give such a glowing review, but I seriously have nothing negative to say about the amp.

You can read about the features in the manual. I play in a classic rock band that gigs every week. This is a basic two (channel switching amp) with an effects loop, which i dont need or use, a direct out jack for going straight into the snake or board, again i prefer a microphone so i dont really need this.(i have gotten great results with a Blue Ball Mic. it seems to sound better that my sm57) It has an interesting tone stack that makes use of a tone control in addition to the regular treb, mid, lows, and presence controlls, also a hi or low input gain switch, and a treble or normal boost switch, giving a variety of options in setting up your sound. It comes with a heavily constructed footswitch to activate the gain and master on/off setting. This amp sounds great in the master volume mode, using the master volume tone stack to shape differing gain structure but to my ears it excells in the normal position with the master volume off. Thats where you can really hear the character of this amp. But it so hard to decide, both modes sound so good and on any given day i may choose either option (depending on the size of the room). The flexi has a 20 watt and a 50 watt option, where the 50 watt setting applies more current to the circuit whereby the tone is altered to a stronger, slightly louder, less compressed sound. I tend to not use boost pedals or overdrives,for the most part and use my volume controll to alter volume. Unles you are using a super clean amp with loads of headroom boost pedals seem to saturate the tone too much for my liking and actually cause it to lose projection. Many times on many amps i have set up a overdrive to sound really great only to find that when PLAYING WITH THE BAND the sound and projection of it sucks. My ideal of an overdrive is to work on the POWER section NOT the preamp section. After i set up my rythem tone and i need a boost for a lead part I WANT THE SAME SOUND.....ONLY LOUDER. A pedal cannot deliver this, so i must make the trade off and just use my volume knob to project solo's . (back in the day i used 2 amps, but i choose not to do this anymore) Every now and then i may use a chorus and in some songs a wah, but thats it. I find it more pleasing to concentrate on the focus of playing and the sound of the guitar rather than an effect. I bought this amp because i heard a player using 1 in his band. He was really stoked about the amp and was very helpfull allowing me to come to their practice to try it out. This amp needs to be tried out at practice with the rest of the band playing. That way you can get an idea of how its going to sound live, rather than sitting in a small room at the music store. Shoot, you can get anything to sound good at a low volume with tons of saturated gain. Its when you're paired up with a pumped up drummer and a angry rythem guitar player and a string poppin bassmaniac, and you really have to open it up is where you can hear the projection and tone and presence of this amp.

I use this amp with les paul customs, standards, and a few different strats a 71 and a newer swampcaster. I play in a classic rock band that plays every week. My current main guitar is a stock 1979 lp custom (custom shop gold top). I have been playing over 35 years, my dad was a recorded opera singer and played 6 different instruments. Sooo..i have been around music and musicians a lot. If you enjoy the tone of the masters (page, beck,clapton,kossoff, etc.), you will enjoy this amp. There are a variety of tones possible with this amp as i will get to later. The whole trick of this amp (and finding your own voice) as a guitar player involves the total sum of the parts ( guitar, strings, pickups,cord, amp, tubes, speakers) This amp does not seem to be noisy and has a variety of fenderish clean to modded marshall tones, but with a lot more bandwith in all areas. I wouldnt classify this amp as a high gain amp, but...with the preamp buried is can get really fat and greasy...ala Leslie West. At 50 watts(w el34's or 6550's) this amp can get louder tha a 50 watt JMP. (my other guitarist uses 1). Or using the 20 watt setting it can replicate marshall high gain tones at a respectable volume. As i grow older i find that false security of having the gain knob buried has left and i find myself seeking tone and sustain rather than gain. This is a great amp for blues, or classic rock IMHO.

This amp seems to be built like a tank. I quit hauling my 50 watt smallbox around as a backup amp. I just take a couple of extra tubes.

Customer support is great. I bought the amp at Indoor Storm used, as a trade in (a young player took it home for a few months, and didnt like it). And i was pleased to find out that Ed said we can start your warranty the day i called, obviously THD is not worrying about this amp breaking down. I have had a few conversations with Ed Degenaro about different aspects of this amp, and was always treated kindly and courteously...and...promptly. One time i e-mailed a question to THD and i didnt even have time to sign off the computer before they replied....Now thats the kind of service i like. BTW the folks at indoor storm are absolutely great to deal with also. KUDOS....

I waited months before submitting a review on this amp. I wanted to test it in live playing situations. So many times i have tried an amp out in the store only to take it on a gig and be disappointed. Now a couple basic things..POWER TUBES.. NOS Mullards(not the re-issues) NOS Siemens, NOS Tesla's, NOS 6550's GE or Tung Sol. Dont even mess with the others you are wasting your time and money. Just get the real shit. Pre amp tubes... I like mullards, telefunkin, amperex, Brimar's, GE's, NOS phillips, tungstrams. I saw 1 telefunkin 12ax7 on this tube dealers site for $425.00...Crazy world we live in..... Q: why do you think they want so much $$$ for these old tubes?????...ANS: because they ROCK. and tube dealers know that some tone fanatic is going to shell out the cash to get that sound. Let me add that the ElectroHarmonix 12ax7 isnt a bad tube, or are the jj ecc803's..nor are the new GT 12ax7 Mullard clone. But each tube has its strong and weak points depending on what you like. But across the board the mullard and telefunkin, and amperex seem to sound the best to me. Now we move on to speakers. The safest speaker to start out with are the V30's i guess. Depending on your tastes there can be many different choices. I have tried G75M's, greenbacks (which dont sound anything like original greenbacks), Weber thames (a nice chime speaker)JBL greybacks (nice clean sound, but dont try and clip them blaaaach)and V 30's. Of all the V 30's sound the best (to me). All mentioned in a 4X12 metal handle old (with J.Marshall's signiture in it ) Marshall cab @16 ohm. Get a good instrument cord. You playin a 2k guitar in a 2k amp and using a $6.95 cord. haaaa... Well that about all i have to offer......good luck....and God Bless.....

20-50 watts, effects loop, boost, self biasing for different tubes. I can't think of more you would need in an amp like this. Very single channel old-school, but extremely versatile.

I should start out by saying I have never felt strongly enough about any product to submit a review like this. I have been in the market for a low wattage tube combo to use at home. I was recently lucky enough to test drive one of these at a Guitar Center with a Les Paul through a Marshall 4x12 cab. I am not crazy into effects, but I do like a little reverb or delay to fatten up my sound normally. I typically walk away unimpressed by most dry amps without some reverb at least. All I can say about this amp is I have never played an amp that actually made me smile while playing it. I am talking about a smile that wouldn't go away for several hours after the experience. I even woke up in the middle of the night a few times thinking about the amp. I won't say it was perfect, but, it came closer to the tone i've heard in my head all these years than anything else i've tried. With the 20 watt switch it was easy to get a cranked Marshall vibe at low volume. The only flaw i could find was it was a little more muddy for rhythym than I would like. I feel confident with a little more time with the amp, it could be dialed out to near perfection. It wasn't the combo i was looking for, but I still can't stop thinking about it.

Seemed very well built. Very heavy for it's size.

I have been searching for the tone in this amp for the past 17 years i've been playing. I didn't buy it because it wasn't a combo, and was a little more money than I wanted to spend. It could very well be the perfect amp tonally for my needs. I just purchased a slightly used Soldano Astroverb 1x12 combo off of ebay based on my experience with this amp and the reviews from this site. If it delivers what reviews claim it could be my last amp purchase. If not I may have to start saving for a Flexi 50.

2005 Flexi-50, very versitile, single channel, boost and master, series effect loop. It has enough power and a very complimentary set of features. I have used this amp gigging, and in my home studio, I am highly satisfied with the features.

This is one of the best sounding amps I have ever heard or owned. You really have to understand how various guitars, pick ups, and tubes work together to get fantastic sounds. I have tried it with the stock EL-34s it came with (excellent), GT-KT66-HPs, and Yellow Jackets with Tesla EL-84s. I have used it with an Anderson Drop Top Classic, Stratocaster Deluxe, Les Paul Standard, PRS Custom-24 and Ibanez RG-520QS with DiMarzio Tone Zone in the Bridge. You can come very close to the Bluesbreaker (KT66 with Les Paul or PRS), Marshall JMP (EL34 with any) Vox AC-30 (EL84 with Anderson or Strat). Certain things don't work as well (Anderson or Strat with KT-66) in my opinion. Also, very nice Fenderish cleans. The amp really shines when played loud with output distortion and no master. Boost for leads is very effective when used in this way, I don't experience the compression others have noted. Really superb harmonics, highly noticable tube characteristics. Again, you must understand how the various factors work together but truly unbelievable sounds when you plan and tweak it. Not for super high gain modern rock as others have noted. Outstanding, phenomenal sounds and gives you the opportunity to learn about tube characteristics.

Build like a tank, small problem with bias diode out of the shop, fixed me up immediately.

Very good. Spoke to Andy Marshall about a small diode problem, dealt with immediately.

Playing for 30 years, definately replace if lost of stole, really unique amp. Many excellent amps out there but the Flexi-50 does perform as advertised once you understand the factors related the the sound coming out of the amp. Could use a true parallel tube driven effects loop but not a real issue.