Tech21 - Character Series.  [schematic]

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Re: Tech21 - Character Series.

Postby JiM » 09 Sep 2011, 19:48

Here is a quick update, for the component values found in Joyo/Harley Benton "True Tone" variations of the Character Series circuit.
Feel free to fill in the blanks ...

Code: Select all
        +------------------------------------------------------+-------------------------------------------+
        |                    T e c h   2 1                     |                  J O Y O                  |
        +---------+---------+------------+-----------+---------+----------+---------+------------+---------+
        | Blonde  | British | California | Liverpool | VTBass  | American | British | California | AC Tone |
--------+---------+---------+------------+-----------+---------+----------+---------+------------+---------+
R4      | *3.3k   |   10k   |            |   3.3k    |  3.3k   |   *10k   |         |            |   10k   |
E1      |  open   |   18n   |            |    22n    |    ?    |   open   |         |            |   22n   |   Input &
Cin     |   22n   |   22n   |            |    22n    |  100n?  |    22n ? |         |            |   22n   |  filtering
C2      |   47n   |   47n   |            |    47n    |  open   |    47n ? |         |            |   47n   |
--------+---------+---------+------------+-----------+---------+----------+---------+------------+---------+
C5      |   22n   |   10n   |            |    22n    |   10n   |    22n   |         |            |   22n   |
C6      |   22n   |   10n   |            |    22n    |   10n   |    15n   |         |            |   22n   |
R6      |    1k   |    1k   |            |     1k    |    1k   |     1k ? |         |            |    1k   |  Character
R7      |  100k   |  100k   |            |   open    |  100k   |   100k   |         |            |  100k   |   pre-EQ
R9      |    1k   |  3.3k   |            |   3.3k    |  3.3k   |   3.3k   |         |            |  3.3k   |
--------+---------+---------+------------+-----------+---------+----------+---------+------------+---------+
R14     |   47k   |   33k   |            |    47k    |   33k   |    33k   |         |            |   33k   |
C14     |  470p   |  470p   |            |   180p    |    ?    |     ?    |         |            |    ?    |  HP sim
C15     |  2.2n   |  2.2n   |            |   2.7n    |    ?    |   2.2n   |         |            |  4.7n ? |
--------+---------+---------+------------+-----------+---------+----------+---------+------------+---------+
C20     |   10n   |   22n   |            |    18n    |    ?    |    15n   |         |            |   18n   |   MID
C21     |   10n   |   22n   |            |    22n    |    ?    |    15n   |         |            |   22n   |    EQ
--------+---------+---------+------------+-----------+---------+----------+---------+------------+---------+
*Not used
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Re: Tech21 - Character Series.

Postby served » 12 Sep 2011, 15:12

Just curious. HB AC Tone is what I have, and when the gain know passes alost max point, it will get really really noisy. Voice knob olso very noisi if I turn it open. What kind of modds could be done there? Some better opamps maybe? What would you suggest. At the moment there are somekind of weird markings on the opamps and I dont really know what they are.
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Re: Tech21 - Character Series.

Postby Mbas974 » 19 Nov 2011, 17:00

Hi, does anyone haveposted the Liverpool schematic ?

...seems I miss it :-(((
can kindly repost

Thank in advance.
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Re: Tech21 - Character Series.

Postby JiM » 19 Nov 2011, 17:41

Mbas974 wrote:Hi, does anyone haveposted the Liverpool schematic ?

It's still linked here : viewtopic.php?f=1&t=6571&start=280#p134003
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Re: Tech21 - Character Series.

Postby Mbas974 » 19 Nov 2011, 20:40

got the pdf file... I think I'll be awake all night !!!

THANKS Jim (and all people work hard for it too !!!)
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Re: Tech21 - Character Series.

Postby Mbas974 » 20 Nov 2011, 16:58

me again...
Got the Liverpool schematic in front of me. Again a great thanks!! :applause:

Beginner question... :slap:
how has to be connected the switching system ? (I see dotten red lines close Q1 Q2 Q3 but wondering where are the connections points exactly).

Thanks
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Re: Tech21 - Character Series.

Postby JiM » 21 Nov 2011, 00:41

Mbas974 wrote:how has to be connected the switching system ? (I see dotten red lines close Q1 Q2 Q3 but wondering where are the connections points exactly).

These dotted red lines are normal wires actually. Q1 is used to short the feedback loop of IC1A, i.e. turn it into a unity gain buffer.
Yep, bypass !

For the rest, just connect the U, V, X, and Y points together.

Before you ask : C30 is 47nF
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Re: Tech21 - Character Series.

Postby Mbas974 » 16 Dec 2011, 23:29

Hi, me again... hardware issue

Looking to the PCB picture I can see the tact switch built on pcb, looking to the pedal I see the gold stomp button, how they coexist ?
Is the gold stomp the "mechanical way" to activate the temporary switch on pcb (if so, where to buy) ?

THANKS
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Re: Tech21 - Character Series.

Postby Maxwell » 05 Jan 2012, 22:44

I'm interested in building one of these but I'd like to understand the circuit a bit more before I jump in...could anyone offer an explanation as to what is happening in the "Drive" or distortion part of the circuit? Those two opamps, the second of which has the diodes in the feedback loop, look really strange!
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Re: Tech21 - Character Series.

Postby Maxwell » 06 Jan 2012, 01:01

To better communicate what I'm talking about, it is this part of the circuit (grabbed from an earlier posted schematic):

liverpool_drive.tiff


I've not seen a circuit like this before.
You do not have the required permissions to view the files attached to this post.
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Re: Tech21 - Character Series.

Postby Maxwell » 06 Jan 2012, 01:03

I meant to add...it looks like the diodes in the feedback loop must perform some kind of clipping function after the first opamp add gain to the signal (I guess)?
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Re: Tech21 - Character Series.

Postby Maxwell » 06 Jan 2012, 19:43

Found most of the answer on page 4, thanks... it seems mostly some weird drawing styles were adding to my confusion as well. This is a very educational thread!
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Re: Tech21 - Character Series.

Postby OrionManMatt » 30 Apr 2012, 17:46

I've tried searching through this topic to see if it had been addressed but I couldn't find anything. I like the way the pedals sound on their own, however whenever I use pedals into them that are boosted it seems like it clips in an undesirable way. Any insight into why that might be?
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Re: Tech21 - Character Series.

Postby mister707 » 02 May 2012, 02:02

Hi guys, I'm Angel Baca of Peru, I was following this topic from the start, thanks to the diagrams published so kindly made ​​this layout, using therefore Circuit Maker 2000, it is not as elaborate as those published by you but it's my first attempt for this forum.
I hope your opinions, I have yet to complete it, greetings to all and see.
P.D. translated with google translate

Image

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bajaman (02 May 2012, 22:02), gaby0076 (20 Sep 2012, 13:22)
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Re: Tech21 - Character Series.

Postby 12Bass » 23 May 2012, 12:30

Just curious if anyone has taken a look at any of the newer Character pedals which have the speaker simulation defeat switch.

I've modded my VT Bass with a switch to bypass the sim circuitry, but am fairly sure that Tech 21's solution is different, as simply bypassing the sim section leads to a huge increase in volume and treble, whereas the change on a real pedal is much more subtle. A lot of people report that the new VT Bass sounds better too... seems to lack the original's upper midrange/lower treble emphasis.
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Re: Tech21 - Character Series.

Postby x-tn » 24 May 2012, 23:23

There is some interesting info about the new version (w/speaker sim switch) in another forum:
http://www.talkbass.com/forum/f36/vt-ba ... ndex2.html

Tech21 guy says that there is HF roll off in the new versions when you switch off the speaker sim:
"The original and updated pedals sound the same with the speaker sim activated.
...completely bypassing the speaker sim would make the pedal even brighter which is why we added the HF roll off."

So, It's not a simple switch removing speaker sim portion from the circuit.
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Re: Tech21 - Character Series.

Postby 12Bass » 25 May 2012, 00:59

x-tn wrote:There is some interesting info about the new version (w/speaker sim switch) in another forum:
http://www.talkbass.com/forum/f36/vt-ba ... ndex2.html

Tech21 guy says that there is HF roll off in the new versions when you switch off the speaker sim:
"The original and updated pedals sound the same with the speaker sim activated.
...completely bypassing the speaker sim would make the pedal even brighter which is why we added the HF roll off."

So, It's not a simple switch removing speaker sim portion from the circuit.

Yep... simply bypassing the sim circuit (as per this thread) adds a lot of treble and increases the volume. The effect of the Tech 21 v2 speaker simulation switch is more subtle. The volume doesn't change much either.

Yesterday I tried out the British pedal and found that the EQ seemed relatively flat with the sim disengaged (up), and brighter in the upper midrange/lower treble with the sim engaged (down). The high treble is still somewhat rolled-off with the sim disengaged. Not sure how much the speaker sim sounds like a real speaker though... as the sound is a bit brash for my taste, not smooth like a good-sounding speaker cabinet.
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Re: Tech21 - Character Series.

Postby theV » 06 Jul 2012, 21:54

Hi to all,
I hope it's ok to bump this thread for a reply maybe a little late...

I modded my (old version) VT Bass for speaker sim bypass thanks to the GREAT instructions provided by OldogNewTrick and the ones who posted the schematics and gut shots :D

I kinda circumvented the (huge) volume increase in the following way.

I used a DPDT switch.
One pole is used for the actual speaker sim bypass operation.
The other one connects (when the speaker sim is bypassed) a newly installed 3.3 Kohm resistor in parallel with the volume pot, thereby reducing the overall output.
(right now I can't remember exactly because it was a bit ago, but I think it is connected between the wiper lug and the "fullscale" lug).

You get the best results around midway of the volume knob excursion, with almost no difference - as desired - in apparent loudness with both the speaker sim engaged or bypassed.
Approaching the extremes it doesn't perform very well: towards maximum volume it gets again too loud and towards minimum, too silent; but I don't care, I'm more than satisfied right now.

Btw, I have a dark sounding enclosure so I like the increase in the upper frequency response, but I'm quite sure that if you add a further, small cap of appropriate value in parallel with the mentioned extra resistor, you could achieve the gentle roll off of the latest pedal versions.

:wink:
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Re: Tech21 - Character Series.

Postby theV » 07 Jul 2012, 19:43

theV wrote:thanks to the GREAT instructions provided by OldogNewTrick and the ones who posted the schematics and gut shots :D


I meant 12Bass user... together with the other ones who contributed, of course!
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Re: Tech21 - Character Series.

Postby drbob1 » 08 Jul 2012, 16:18

I found a British cheap and tried it out vs my original "Sansamp". Gotta say that they cover a lot of the same ground in the "Normal" mode on the Sansamp pedal. I guess I'll just continue to refine my tuning technique for the original, it's gotta have most of the sounds you can get from the Character series in there somewhere...
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