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Flextone 3 - How To Get A Much More Tubeamp-a-like Sound

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Hi there,
are you tired about discussing different speakermodels for the Flextone III amps ?

So let me tell you how to get a much more brillant and crisp sound from your Flextone3 in three easy steps without a speaker change.

After unplugging the mains cord and disconnecting the speaker cables remove the Amp Chassis with the 4 large screws on top and the 4 small screws for the handle.

1) For those who won´t solder on  SMD devices but are aware of tubeamp modifications :


Solder 2 pcs  of  4,7nF film cap across the In- and the Output pins ( bottomview right and middle) on both of the stacked stereo Mastervolume Pot (B 10k) ,  like the "bypass" caps for higher frequencies on Volume Pots in guitars or in valve amps.

Seen from above on the back :   these are the right and the middle pins of the double pot !


So you will have much more over all brillance and treble also at lower power settings without changing the speaker. 

Check first with a Clean amp modell like the DOUBLE VERB with its  2x12 emulation.

If you ever have tried such an analog beast you will find it now -with the same attitude - here in the Flextone3.

And all at neutral 12 o´clock  settings on the EQ pots.   After that try chrunch and High Gain emulations. 



2)  For those who will try additional mods :

Remove the very very small capacitor signed as "C4" from the board with a small solder pen !

If you are not aware in soldering on SMD devices please take care and better take the board to the next electronic technician or to a radio shop with educated personell. Its all at your own risc !!!

These small capacitor( 47pf ) works together with the L1 ( SMD inductance) as a trap for high frequency EMC trouble. Under normal circumstances you will not need it.

And - unfortunatly - the 47pf cuts all the highest frequencies from your guitar signal like a bad guitar cable !
by the way....you´ll never see such a capacitor e.g. in a high class tube guitar amps in the first stage.
So, if there are no high frequencies from the strings .......the amplifier cannot amplify such details.
And the sound will not be so bright, not so clear or crisp .....or what ever words you will use.

But, if you like an  open Tubeamp sound remove the C4 and you will be very happy with the improved sound.
These mods should also work in HD147 ´s , because they use the same technology inside as the Flextone III.

A few words to the Line6 developers :
I know the reasons well for building in the C4/L1 into the amps. Its because the CE and US trade specifications !
But for a musician it sounds much better without these absorption circuits. ;-) Thanks for this great Amp !!!!!!

Peter from Germany  

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  • 1 month later...

I took Peter's advice on removing the C4 Capacitor and I was happy with the results. I couldn't find any more information on this mod beyond Peters post, so I just went for it. 

If you have a good understanding of Safe work practices when dealing with electronics and some time to watch a youtube video on soldering, you can handle this mod. 


Most importantly,

-Unplug any and all power sources

-Dont let the Soldering Iron come into contact with any other components or Overheat the area surrounding C4

(He was right when he said   "very very small capacitor" its smaller than a flea. So, be careful with the Iron.)


I'll increase C5 and let you know how it turns out. I've got to go pick up the Film Capacitor so it may be a lil while.  


Thanks for your insight Peter, 



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  • 3 weeks later...

After reading this thread I also removed C4. Quite an improvement! Thanks Peter!

At this point I have no need to try the other mods of C5/L1. For me it's just fine like this.


I do agree with both Peter and Hans. Without any knowledge or the right soldering tools it's a bit tricky.


Use a small solder tip, a small bellow to suck up the tin, and a magnifying glass.

Despite having all this and working carefully I almost screwed it up when some soldering tin shorted with the other components.

Luckily I could remove that quickly.

It was a great relief to hear that the amp still worked and sounds much better than before!

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  • 2 weeks later...

Hans, Mark,
thanks for your comments and additional suggestions.


Pls have a look to my first writing !

I did add another  very effective mod within the upper discription to get a much more clear and biting over all sound

from lower to higher volume levels without kidding with the terrible SMD´s .


For further discussions or questions pls try to contact me via my homepage  toneshop.de


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  • 1 month later...

Guys, I remove the C4 and come a delay to the sound, same like auto swell or something...I put it back and everything is fine...I remove the C4 that is at the left side of the amp, is that it? I really want this mod to work...

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We do not talk about capacitors on the main board !!!!


We talk about the C4 which is located on the small board with the the 6,3mm Input jack on !  It is the guitar preamp.

This board is screwed into the front panel and linked with a 5 pin connector to the main board and you can easy remove it to solder on.


- Peter

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  • 1 year later...
  • 4 months later...

Hey, I am reading your post and about to do it, however, I have a question

"Solder 2 pcs  of  4,7nF film cap across the In- and the Output pins ( bottomview right and middle) on both of the stacked stereo Mastervolume Pot (B 10k)"

A)Do you mean I need to caps? Solder one to the bottom pot and the other to the top pot? The stereo pot inside legs are very difficult to solder to?

B) Do you mean solder 1 cap across in/out on the pot that is easy to solder to?
The outside legs?

C) Do you mean solder 1 cap to both inside legs and outside legs.

Any help you can give... please.

email genmce(at)yahoo

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  • 5 years later...

I know this is a very old thread, but, I haven't had my Flextone III for very long and have been reading about it like crazy. I did the #2 mod on my amp a little while after I got it and liked the difference it made. Just today I was able to find the time to do the #1 mod. I've known about the bright cap mod people use on some Marshall and Fender amps for a while, but never applied it to a guitar amp. But, with this amp, I felt it needed something, as I feel it's a bit muddy with the Master Volume at 12 o'clock when I use it at home. I had (4) 2.2nF film capacitors and ended up running two of them parallel for 4.4nF per stereo side of the Master Volume pot. Wow, what a difference. The change was dramatic. It gives the sound so much more air. Now, I am wondering if 4.4nF is too much however. I may experiment more. Maybe try 2.2nF per side? But, I'm going to have to change many of my tones now because the amp sounds so much different. Thanks for the original post Flexpeter. Has anyone else tried different values for the capacitors on the Master Volume pot on this amp? I'd love to hear about if you have.

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