THD Flexi 50

stephen sawall

stephen sawall

Well-known member
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.

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.

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.

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.
 
Necro but I want to know if you still feel the same way about the amp after all this time and if anyone here has any feedback?

Btw are there any mods that people know of worth mentioning?
 
I just saw this today.

I still use the amp all the time.
Personally I feel the Bivalve gets closer to the Marshall thing.

I have four THD amps. Each one has its own sound. The thing about THD amps is the amount of harmonics.

Flexi 50 - Does English crunch and Fender Tweed stuff. Class AB.

Bivalve 30 - probably the most gain. Not high gain. But can get very aggressive. Class A. Has all the odd and even harmonics.

Series One Plexi - a 1969 JMP clone, 50 watt small box. Voiced with Dave Friedman amp that Dave uses to voice everything. Personally it is the best sounding Marshall type amp I have heard. Lots of glass and really nice attack.

Deco 36 - 4 x EL84, 2 x 12AX7. Cathode bias (self bias). Class A or AB depending on settings. Doesn't sound like any other EL84 amp.
There was two prototypes built about 15 years ago. Andy Marshall recently built me a one off. This amp will go into production. He has parts to build a few hand wired right now.
 
stephen sawall said:
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.

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.

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.

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.
Click to expand...
Hi!
I am considering getting one of these. Would you mind answering a couple of questions?

- Could you get a “quasi two-channel” setup going with slightly crunchy unboosted and then full on drive with the boost and the link high/low input switch?
- If you stick a volume pedal or tuner in the loop, does it silence the amp completely, even with the boost activated? (My current amp bleeds a little bit of signal that gets really loud through a PA).
- What’s your issue with the loop? Just an issue with power amp/post fx distortion?

Thanks!
 
Torbiz said:
Hi!
I am considering getting one of these. Would you mind answering a couple of questions?

- Could you get a “quasi two-channel” setup going with slightly crunchy unboosted and then full on drive with the boost and the link high/low input switch?
- If you stick a volume pedal or tuner in the loop, does it silence the amp completely, even with the boost activated? (My current amp bleeds a little bit of signal that gets really loud through a PA).
- What’s your issue with the loop? Just an issue with power amp/post fx distortion?

Thanks!
Click to expand...
THD amps are not about preamp distortion. They are about poweramp overdrive. Most of the distortion comes from the poweramp. Most effects people put in the loop of a amp do not sound good with distortion after them. I don't consider it a problem really. I have a Fryette PS-100. I could use it's loop if needed.

quasi two-channel .... Yes you could do that. But it behaves more like a vintage amp than a modern Master Volume amp.

Personally the way I usually use the amp is like a single channel and get different sounds by using the guitar controls or boost / overdrive pedals.

If the effects loop bleeds I am not sure. I haven't used the effects loop in about 20 years and the amp is still packed from my last move.
 
Univalve is pretty different voice from the Flexi.
All the THD amps are about poweramp overdrive more than preamp distortion.
 
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I used to work for Andy, about 2001. He was a good friend to me then. I had moved back from San Diego and he hooked me up with a job. Even let me stay with him for a short while on a rather small houseboat..lol. Had never used a compost toilet before..😉.
I would do the final QC and shipping of Univalves and do local runs to places contracted to do powder coating and transformers etc. While I was there I was writing the serial numbers by hand with a Sharpie, my penmanship was pretty good I thought..lol. As luck would have it, when I was ready to get a Univalve for myself it was getting close to a certain serial number and I asked if it was OK if I gave that number to the one I was going to get and Andy said yes.
So I broke out the red sharpie and wrote me a rather splendid 666 in the same style as in the Omen. Unfortunately I didn’t work there for long as Andy overestimated how much he could afford to have me on, so after a slow summer it was goodbye and many thanks from me for getting me going on my return to Seattle. I had to sell the amp along with most of my gear to keep afloat being unemployed for a minute (bummer, but that’s life). So if anyone comes across serial 666 and wonders what is up with that, there it is. I really hope nobody covered it up from being superstitious or religious.
 
Last edited:
I currently own a THD...
Series One Plexi 50
Univalve 15
BiValve 30
Flexi 50
Deco 36

Each has it's own sound. But what they have in common is very touch sensitive and ton of harmonics in phase.
Easy my favorite amps. I don't have a favorite among them. Each does it's own thing.

These are not high gain amps. Maybe a little more than a JCM 800. If you want more just use pedals.
 
stephen sawall said:
I currently own a THD...
Series One Plexi 50
Univalve 15
BiValve 30
Flexi 50
Deco 36

Each has it's own sound. But what they have in common is very touch sensitive and ton of harmonics in phase.
Easy my favorite amps. I don't have a favorite among them. Each does it's own thing.

These are not high gain amps. Maybe a little more than a JCM 800. If you want more just use pedals.
Click to expand...
Even though I’m usually an EL34 guy I liked the Univalve best with a 6V6 and sometimes an EL84/yellowjacket. I couldn’t get enough top end rawness out of Bivalve and the Flexi but it’s been so long since I tried them and I’m into different stuff now, so hopefully will get a chance to try one again. I’m trying to remember if you had to use the low Voltage selection for a 6V6 and EL84 on the Univalve?
 
skoora said:
Even though I’m usually an EL34 guy I liked the Univalve best with a 6V6 and sometimes an EL84/yellowjacket. I couldn’t get enough top end rawness out of Bivalve and the Flexi but it’s been so long since I tried them and I’m into different stuff now, so hopefully will get a chance to try one again. I’m trying to remember if you had to use the low Voltage selection for a 6V6 and EL84 on the Univalve?
Click to expand...
Yes low on both of those tubes.
Currently EL34 in the Univalve, Plexi and Flexi. KT88 in the Bivalve. The Deco 36 is EL84 only. It is self biasing. But doesn't switch tubes like the other amps.

Andy mentioned he really likes a 6V6 in the Univalve. KT66 in the Bivalve and Flexi.

I occasionally switch out a bunch of tubes and land someplace else.
 
Stephen, you and I have talked in the past and you've been a wealth of knowledge especially regarding THD amps. I had a Flexi, sold it. Bought another. And sold it. Every time I think I know what I like something else shows up. Now I'm thinking about buying yet another Flexi. What the?
To have an amp that you can constantly tube roll finally seems like a therapy dog for someone suffering from chronic GAS. I was convinced that KT88 tubes were IT! But then I acquired a Redplate Magica 100, EL34 power tubes and forgot about anything KT88. Not really but definitely became my number one. Now I've been looking for an amp for smaller gigs and one of my knocks on the Flexi was that it seemed like a somewhat low 50 watts, depending on tubes of course. I think you agreed with that assessment. Reality steps in and that power level is perfect for certain gigs that I want to take. Wine bar and such. I don't really have a question but I just wanted to share my experience with the Flexi 50. My small bit of wisdom, and I will need to make that purchase to really clearly describe this hack sort of, but I was using a single switch pedal to simultaneously turn on the master and the boost? Something like that. Damn. Can't remember exactly but it made all the difference in my usage. If anyone wants to know I might be able to figure it out.
 
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