xtc 20th

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Im trying to figure out whats different in the 20th preamp as compared to the 101b if anyone has any gut shots of the 20th i would appreciate it.
 
Basically the 20th has less compression and is tighter with more high mids (bite). That being said, if you want a smoother or looser, more vintage tone there's the vintage/modern switch, old style mode, excursion switches, etc. I can get pretty close to the 101b sound if I make changes like those. Here's a guy who showcases the channels pretty well I think:

 
do you know if there's any benefit to changing the preamp voltage. say raising it up to 400 ?
 
pedal builder":33krkaru said:
do you know if there's any benefit to changing the preamp voltage. say raising it up to 400 ?
Click to expand...


preamp voltage? I know reinhold chose to bias the 6l6 tubes colder to get them to sound closer el34's in the 20th.
 
se7en":2viiwfqt said:
pedal builder":2viiwfqt said:
do you know if there's any benefit to changing the preamp voltage. say raising it up to 400 ?
Click to expand...


preamp voltage? I know reinhold chose to bias the 6l6 tubes colder to get them to sound closer el34's in the 20th.
Click to expand...
I opted for the EL34 version.

2 birds.
 
is there any info around on how the filtering is done ? and is there any difference in the excursion circuit
 
Any idea how to get one of those "uber" modded 101b's mentioned in the threads Setneck posted?
 
started trying some of those changes listed in the second link, so far not sounding right unless i'm reading it wrong. so somebody correct me if this is wrong.
R112 change to 1M in series with 2nf and the 330k voltage divider goes from R112 to ground ?
second cathode R11 4.75 to 2.7
3rd stage cathode R12 10 to 2.7
3rd stage bypass c11
4th cathode R19 bypass w/1u
plexi mode is R101/C55
 
For the record, I'd never f*ck with my 20thA-EL34 XTC.

Ever.
 
well if i had a 20th i probably wouldn't either. i'm trying to get mt 101b to sound closer to a 20th
 
pedal builder":88w98b7y said:
do you know if there's any benefit to changing the preamp voltage. say raising it up to 400 ?
Click to expand...
In general, higher voltages = cleaner and brighter; lower voltages = browner, more distorted
Higher plate voltage gives a cleaner and more punchy sound with tighter lows, not as middy and compressed. In general, lower voltages are darker, warmer, browner with more mid emphasis and earlier onset of overdrive. Higher voltages are cleaner, stiffer with more robust bass and treble and extended headroom.

There are certain applications by design where you would consider using either exclusively. In a clean bright preamp like a Fender Twin you would probably want to use higher voltages, because it will give cleaner sound with more headroom. In a crunchy preamp like a 2203/1959 (so a family the XTC belongs to) you may want lower voltages to achieve a warmer, more distorted texture.

I was advised to raise a preamp voltage when I was modding my amp, but it didn't do it. That would mean lower overall gain, which wasn't a goal for me.

If You want to mess with preamp voltage supply here's the pic of the black 15K resistor under the board, which controls it. It is placed directly under the main filter caps. You may try to lower its value to 10k or 4.7k. I was advised to try one of those.




Best regards, Andy :)
 

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Jer":3f1c8bc1 said:
Any idea how to get one of those "uber" modded 101b's mentioned in the threads Setneck posted?
Click to expand...
Well, "Uber Mod" is actually a conventional name for a tweak, which is a variation of R12 Cameron Mod, where instead of 1uF cap .68uF is used. It doesn't make XTC sounding "Uber" though, so the name is a bit confusing, sorry about that :).

You put it on R12 the same way as Post2004 Factory Mod. I have it on switch, as Factory Mod gives too much gain. See here for more details: viewtopic.php?f=59&t=116020#p1619844

Best regards, Andy :)
 
Setneck":3k52aaak said:
pedal builder":3k52aaak said:
do you know if there's any benefit to changing the preamp voltage. say raising it up to 400 ?
Click to expand...
In general, higher voltages = cleaner and brighter; lower voltages = browner, more distorted
Higher plate voltage gives a cleaner and more punchy sound with tighter lows, not as middy and compressed. In general, lower voltages are darker, warmer, browner with more mid emphasis and earlier onset of overdrive. Higher voltages are cleaner, stiffer with more robust bass and treble and extended headroom.

There are certain applications by design where you would consider using either exclusively. In a clean bright preamp like a Fender Twin you would probably want to use higher voltages, because it will give cleaner sound with more headroom. In a crunchy preamp like a 2203/1959 (so a family the XTC belongs to) you may want lower voltages to achieve a warmer, more distorted texture.

I was advised to raise a preamp voltage when I was modding my amp, but it didn't do it. That would mean lower overall gain, which wasn't a goal for me.

If You want to mess with preamp voltage supply here's the pic of the black 15K resistor under the board, which controls it. It is placed directly under the main filter caps. You may try to lower its value to 10k or 4.7k. I was advised to try one of those.




Best regards, Andy :)
Click to expand...

Thanks Andy

do you happen to know about the filtering for the 20th/classic.
so far the only difference i can see is the four big electrolytic's were dropped from 270uf to 50+50uf dual section
 
pedal builder":3v1qe2gi said:
do you happen to know about the filtering for the 20th/classic.
so far the only difference i can see is the four big electrolytic's were dropped from 270uf to 220uf
Click to expand...
No, unfortunately I have no info about that. And I am very interested in it as well. Maybe someone who owns 20thAnn or Classic might open the amp and drop us a piece of info :).

Regards, Andy :)
 
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