All user reviews for the Thd Flexi 50 Head

All tube 50 watt head.
3 12AX7 pre-amp tubes, 2 EL34 power tubes.
Volume, bass, mid, treble, boost volume, boost tone, master and cut controls.
Switches for input sensitivity, bright, boost on/off, master on/off, 20/50 watt mode, stand-by and power.
On the back you get passive line level effects loop send and return jacks, 2 speaker jacks and the 2/4 ohm-8/16 ohm impedance selector, transformer driven live out with line/instrument level switch and control. As well as the "link input to boost switch" with that you can foot switch the amp so when you turn the boost on the amp uses the high sensitivity input and off it uses low sensitivity.
There are also bias points and controls so you can bias the quickly for your power tubes of choice.

UTILIZATION

As with all THD amps super easy to get a good tone out of. With the same caveat as for the UniValve or BiValve it needs to be dialed with the ear not the eyes.

SOUNDS

That's what I love about this amp. It sounds and feels like an old amp. Without loosing its identity. That in itself is quite the feat. I use it mostly set to a crunch sound so i can use the guitar's volume to clean it up. This is actually one of the few amps where the clean sounds amazing when used like this. And for over the top stuff I hit it with a pedal. Usually something like a Maxon SD9 or a Demeter Fat Boost.

OVERALL OPINION

Great amp in a small package. I really like to use it different than intended. It shipped with 2 12AX7 and a 12AT7 and replacing the AT for another AX type type in the pre-amp it opened up. Then using the bias controls to run the bias at 33 mA instead of the factory setting of 25 mA made crunch chords overall frequencies much more cohesive. Switching to running a EL34 and 6550 together gave me the best of both worlds. The nice midrange :fur" of the 34 with the bottom and "glass" of the 6550.

Originally written by Stephen Sawall from rig-talk.com

The design was all about getting British voiced distortion and a great clean from one amp.

With the switches there are a number of clean voices to choose from.
I like the clean sounds I get with the boost on best.

No matter how distorted you run the amps preamp and or poweramp you can use the volume on the guitar to get a good clean.

I feel a Hot Plate with the amp is very practical because a lot of the sounds from this amps are about the power amp being turned up.

The tone controls are not very interactive and have a large range that works.
Baxandall bass/treble. Very strong mid control.
No presence but the cut is similar but does not add gain.

The clean to clean break up on the amp is amazing.
I am sure the huge dynamic range of the amp helps.
When using a pick or my fingers it responses more to my right hand more than any other amp I have played on.

Headroom is not something that I have had a problem with.

What preamp and poweramp tubes you use gives different colors and headroom.
Setting the bias a little hotter or cooler also changes things.

UTILIZATION

This is a comparison of a Flexi 50 to a JMP
.It would be similar comparing it to a lot of amps.....

You well want a Hot Plate or what you like to use with these amps.
We are talking about power amp distortion here.

The Flexi has more bottom and low midrage if you want, the Marshall's sound kind of thin side by side with the THD.

The mid range on the two are different. Both sound good in a mix/live.
There is way more dynamics and control with your right hand with the Flexi.
The Marshall well be more compressed with a equal range of gain.
The Flexi may be the most dynamic amp made for guitar.

The Flexi has more gain on tap as it does have a boost.
You can get more gain than a single channel 800 with the boost on the Flexi.

You can put a lot of different tubes pre/power in the Flexi.
Without much time spent doing it.



SOUNDS

The clean sound in my ears has a lot more of that old Fender tone, feel.
You can back off the volume on the guitar down to clean and does this with every guitar I have put into it.
With a Marshall if you back off too much it just gets thin and weak.

The tone controls on the Flexi have a huge range and sounds good with a lot of range.
Many voices that all work very well.

There are more voice options with the THD.
Input - Hi/Lo
Bright - on/off
Boost - on/off
50w/20wMaster - on/off
These are all tools I use.

You can get in the ball park of many English tones, even the Vox tones.
I did say ball park. That is with the right pre/power tubes.

The harmonics that come from the Flexi are unreal. I have only heard a few amps that come close.

OVERALL OPINION

The THD is very well built and I run it full blast without thinking twice about it
if I want that tone / gain/ feel.

Good luck finding a Marshall that does not have some bad mod done to it. If you don't know THD stands by there amps.

The problem with the effect loop is the same as all amps that get a lot of the distortion from the power amp. Distortion after the effect does not sound good with a lot of effects.

My father fixed amps on the side when I was a kid (70's,early 80's).I have played thru a lot of the classic amps.
The harmonics, punch, attack envelope, tone range and most of all the way it reacts to my right hand.The dynamics are key to the way I play.
I feel the Flexi is equal or better than anything else I have played on for a lot of things.
THD builds my favorite amps.

The Marshall sounds like a Marshall and I love that sound.But I do not miss the ones I have had that much, even my JMP and Super Lead. The Flexi just does a lot more.

The Flexi 50 is a handbuilt tube amp made in Seattle, Washington by a mad scientist by the name of Andy Marshall.
The power output is switchable between 50w and 20w. Unlike many other amps that have this feature, this variation in output power is achieved by changing the HT supply voltage to the tubes rather than a pentode/triode switch. This keeps the tone and response of the pentode operation at a lower volume.
There is a switch on the back to select between 2/4 Ohm and 4/8/16 Ohm output impedances. Very useful for those who have oddball 2 Ohm cabs.
There's a switchable boost function with level and tone controls. It can be fairly transparent or cut/boost high end for different tones. Very useful for live situations as it can be controlled by a footswitch in addition to the front panel switch.
To keep things simple, there's only one input but there's a switch to change between high and low gain signal paths. It's not switchable via the footswitch unless you configure it to switch in/out with the boost.
The master volume is switchable by either a front panel switch or footswitch. Great for a lead boost if you're already running it fairly high.
The rest of the controls are volume (gain), treble, middle, bass and a cut knob. The tone stack is of the Baxandall type and as such allows for great flexibility and precision. I'm not sure where in the circuit the cut knob is but it acts much like a standard presence control.
There's also a line level series FX loop that works great for rack FX and a transformer isolated line out with a level control that is awesome for those who run dry/wet stereo rigs.
There are also external bias test points that make biasing a simple 30 second operation, a god send due to the ability to switch out power tubes as you wish.
The O'Netics transformers are also shielded for low noise.

UTILIZATION

Dialing in a good sound is extremely simple. Some sample settings are included in the manual for those who would like a good place to start.
The manual is great and explains limitations and valid tube substitutions. It also explains how to bias the amp with precision and consistency. If you ever lose it, a copy can be found on the THD website very easily and the tube substitutions are listed on the chassis.

SOUNDS

I use either a '56 RI Strat with Lollar Blackface pups or a Standard Strat with a BareKnuckle VHII in the bridge. Both sound killer.
I find that the mid knob likes to be run fairly high, ie past 2 o clock, the bass knob likes to be kept low when using distortion and higher when using cleans. The treble knob is similar, as is the cut knob. The boost tone can be set pretty much anywhere and sound great, it just depends on what you want out of the boost.
The touch sensitivity is outstanding. With the gain all the way up in high gain mode with the boost on, you can clean it up completely just by using your volume knob and the tone doesn't thin out or muddy up like many amps. The boost function does seem to add a bit of compression, though it's nothing too much.
With 6L6 or 6V6 power tubes, I can get a nice Blackface Fender type tone with some scooped mids and higher bass/treble/presence. They're not exact, particularly due to the Black Back speakers I use but they're close enough for live use and could be dialed in further for studio use.
With EL34 power tubes, classic Marshall and hot rodded Marshall tones come very easily. Mids turned up, bass set with moderation and treble/cut set to whatever I'm feeling that day, classic Led Zeppelin and AC/DC through Van Halen and Ratt tones come very easily. All with fantastic clean up ability.
Clarity and note separation are killer. Complex chords can be played with moderate gain settings if you've got articulate pickups.

OVERALL OPINION

The thing I like most about it is the build quality. The THD stuff is built by FAA certified assemblers and it shows. The very first day I had it, I managed to drop it down a flight of stairs. Other than a few minor scratches and a slightly bent corner of the steel shell, it worked flawlessly afterwards. The steel corner was very easy to bend back into place and looks just like new now.
The thing I like least about it is that the variety of tones are a bit difficult to access live. Switchable channels would be great.
The value for a studio musician is killer. This could easily replace 2 or 3 amps that the muso would no longer have to cart around, saving set up time. For those with no experience in that area, time is very valuable in a studio.
A gigging musician may not like the lack of on the fly versatility but to be honest, it doesn't make near as much difference in that situation. You could easily do a gig with varying cleans and heavy tones throughout with the Flexi, it just won't be your ideal clean or dirty tone.
The amp sounds consistently great and I wouldn't worry at all about it all of a sudden sounding bad right before an important gig.
I didn't really try any similar amps before this as I wasn't looking for this type of amp when I bought it. I do have experience with many similar amps though and I can say the Flexi easily hangs with the best of them.
After owning the Flexi for a few months, I'd easily buy it again at the price I got it at and probably even the new price, though I don't really buy music gear new. It's honestly the only single channel, vintage style amp a guy could ever need.

This is a tube amp made by THD. This company has not been very good at getting their name out there, which is a shame because they make some really cool products that are really ahead of the curve. This is a tube amp head that can switch between 20 and 50 watts with the touch of a button. It has controls for volume (gain), three band EQ, a master volume and a boost (which can both be bypassed via a footswitch), as well as a "cut" knob which works like a presence knob but is sort of different in a way that I can't really describe. It's different in that it doesn't really affect your other EQ settings as much, which is pretty mind-blowing to me.

UTILIZATION

This amp is really one of the more versatile amps out there, and this is mainly because it allows you to change the fundamental way it operates. This can be as easy as bypassing the master volume or boost, or even switching the wattage from 50 to 20. However, the real treat is the ability to switch virtually any kind of tube into the amp, as it has a detailed manual that will give you precise instructions. Considering the variety of different tubes that one can buy, this is really an unprecedented feature.

SOUNDS

I love the sound that I got out of this amp. I haven't had time to really change the tubes out, so I don't know how different tubes work in it, but the stock tubes were more than adequate. This sort of reminds me of an older Marshall tone, nothing too modern and boring. It has a great way of reminding me of great classic sounds like Cream and Hendrix. Increasing the wattage can really add a whole new level of impact. The boost channel gives you more of an in-your-face sound, and can be EQ'd perfectly for solos and leads. This is just an all around great tube amp from the get-go, and can only be improved by tinkering around with it more.

OVERALL OPINION

This is a ridiculously expensive amp, which makes me wonder whether or not it's worth it. I would say that it is simply because there is so much variety. If you want it to work more like a Twin, you can put in the 6l6 tubes or if you want Marshall tones, EL34. This isn't possible with many (if any) other amps. Basically you're paying for the wiring to be done for you while you customize the amp, and also a ton of other killer features. Highly recommended.