Tech21 - Character Series.  [schematic]

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Re: Tech21 - Character Series.

Postby Mbas974 » 30 Apr 2013, 09:47

I've noticed that the EQ section use different caps from type to type. ( C23 to C28 )

Why these are not mapped into the comparison matrix some posts above :hmmm:
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Re: Tech21 - Character Series.

Postby Mbas974 » 30 Apr 2013, 20:31

Question.... (stupid I think....)

R100, R103, R104 labeled NOT USED.... means that the Op-Amp are buffer or have the feedback loop has to be leaved open ?
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Re: Tech21 - Character Series.

Postby JiM » 01 May 2013, 16:22

Mbas974 wrote:I've noticed that the EQ section use different caps from type to type. ( C23 to C28 )
Why these are not mapped into the comparison matrix some posts above :hmmm:

That's because the first models to be traced (Blonde, British, Liverpool) do indeed have the same values there.
Feel free to expand the table.

Mbas974 wrote:R100, R103, R104 labeled NOT USED.... means that the Op-Amp are buffer or have the feedback loop has to be leaved open ?

Those resistors are open-circuit inside the gooped module. The feedback loops are not open though, look closer at the schematic. :wink:
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TLC2262 & clipping

Postby x-tn » 01 May 2013, 19:15

bajaman wrote:...
Anyway - back to the CH34-4 module :wink:
This module uses the LINCMos TLC2262 dual op amp - internally entirely constructed with mosfets - it gain swing the signal full rail before it clips and Tech 21 have used this same device in all of their pedals from the original Sans Amp onward. It has a very soft clipping characteristic and can sound a bit "mushy' in the bass region in my opinion. However it's implementation in the character series pedal is a little different :wink: With reference to the schematics earlier in this thread you may notice two back to back 3.3v silicon zener diodes in the feedback loop of the second stage of the CH34-4 module.
It is THESE zener diodes that clip FIRST in this module according to my simulations NOT the op amp as in the original Sans Amp pedals. These zeners also roll off the high frequency response of this stage - the signal is -3dB down at 5khz and drops to over -22db at 100khz. Without the zeners, the response is flat to 100khz and beyond :shock:
I must emphasize that the signal is attenuated at high frequencies by these zeners EVEN when the signal is NOT being clipped by them :!:
The TLC2262 NEVER has the chance to influence the clipping behaviour in these pedals - all the clipping and high frequency rolloff is performed by the two back to back zener diodes - food for thought :secret:
Cheers
bajaman


bajaman wrote:I just bought a JOYO California sound pedal
...
I changed the dual op amp (TL062) - put a TLC2262 in it's place - i left the other two quad op amps (TL064).
...
bajaman


If "The TLC2262 NEVER has the chance to influence the clipping behaviour in these pedals" what would be the reason to change the TL062 with a TLC2262?
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Re: Tech21 - Character Series.

Postby bajaman » 02 May 2013, 01:22

good point :wink:
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Re: Tech21 - Character Series.

Postby engineelite » 26 May 2013, 21:54

How close are you guys to getting this finalized? I'm really anxious to build a tech21 blonde clone :mrgreen:
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Re: Tech21 - Character Series.

Postby Nocentelli » 26 Mar 2014, 19:14

Hi all.

My bro-in-law has given me his Blonde to try and repair the intermittent footswitch. I knew it would be electronic switching from the schem, but I'm struggling to get it a part to check the actual board-mounted switch.

Do I actually have to de-solder the in and out jacks to get access to the board?
mmolteratx wrote:absolutely zero commercial use allowed. If I find anyone selling these, I'll fly to your house and kick you in the nads. And you may or may not find yourself in trouble.
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Re: Tech21 - Character Series.

Postby jaylj14 » 06 Apr 2014, 14:33

What is the Q100(SOT-23) in the schematic?
Are they two 3.3V Zener?
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Re: Tech21 - Character Series.

Postby theV » 06 Apr 2014, 16:04

Nocentelli wrote:Do I actually have to de-solder the in and out jacks to get access to the board?


No,
at least in my revision of VT Bass. Just unscrew the screws and all the nuts, and it comes apart.

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Re: Tech21 - Character Series.

Postby Stephanovitch » 15 Apr 2014, 06:16

I have mesured value of the California Joyo:
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(R4) |   10k (R4) |   10k   |
E1      |  open   |   18n   |            |    22n    |  10nF   |   open   | 18n(C3) |  open (C3) |   22n   |   Input &
Cin     |   22n   |   22n   |            |    22n    |  22n    |    22n ? | 22n(C1) |   22n (C1) |   22n   |  filtering
C2      |   47n   |   47n   |            |    47n    |  open   |    47n ? | 47n(C2) |   47n (C2) |   47n   |
--------+---------+---------+------------+-----------+---------+----------+---------+------------+---------+
C5      |   22n   |   10n   |            |    22n    |   10n   |    22n   | 3n (C8) |   10n (C8) |   22n   |
C6      |   22n   |   10n   |            |    22n    |   10n   |    15n   | 82p(C7) |  open (C7) |   22n   |
R6      |    1k   |    1k   |            |     1k    |    1k   |     1k ? | 1k (R6) |    1k (R6) |    1k   |  Character
R7      |  100k   |  100k   |            |   open    |  100k   |   100k   | 100k(R7)|  100k (R7) |  100k   |   pre-EQ
R9      |    1k   |  3.3k   |            |   3.3k    |  3.3k   |   3.3k   |3.3k(R10)|  3.3k(R10) |  3.3k   |
--------+---------+---------+------------+-----------+---------+----------+---------+------------+---------+
R14     |   47k   |   33k   |            |    47k    |   33k   |    33k   | 33k(R24)|  33k (R24) |   33k   |
C14     |  470p   |  470p   |            |   180p    |   470p  |     ?    |470p(C17)| 560p (C17) |    ?    |  HP sim
C15     |  2.2n   |  2.2n   |            |   2.7n    |   2.2n  |   2.2n   |2.2n(C18)| 2.8n (C18) |  4.7n ? |
--------+---------+---------+------------+-----------+---------+----------+---------+------------+---------+
C20     |   10n   |   22n   |            |    18n    |   10n   |    15n   |15n(C25) |  22n (C25) |   18n   |   MID
C21     |   10n   |   22n   |            |    22n    |   10n   |    15n   |22n(C24) |  22n (C24) |   22n   |    EQ
--------+---------+---------+------------+-----------+---------+----------+---------+------------+---------+
*Not used


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Desdog (06 Apr 2015, 21:50), eastermaster (19 May 2014, 12:47), JiM (17 Apr 2014, 10:43), MACopeland90 (01 Apr 2016, 02:38), x-tn (16 Apr 2014, 01:42)
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Re: Tech21 - Character Series.

Postby moralo75 » 09 Aug 2014, 15:34

Good afternoon, I am interested in buying an American or California Joyo to become VTBass ... you think that you may easily ??? Which would be better to buy ???
Thanks and sorry for my english ...
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Re: Tech21 - Character Series.

Postby rocket512 » 18 Aug 2014, 23:50

Are there any values available for the Leeds ( Hiwatt)?

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Re: Tech21 - Character Series.

Postby artaommahe » 19 Aug 2014, 17:57

About speakersim on-off switch.

It's strange to have 22k-10n chain after high pass filter C11-R13, because we have bass drop on speaker-sim off. It's important for VT Bass variation. So i think low pass filter 22k-10n can be moved before C11-R13 without any issues.
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Re: Tech21 - Character Series.

Postby artaommahe » 19 Aug 2014, 18:38

I was wrong, the problem is in C13-R16 filter, that reduce bass response as bajaman noted above. But the solution is the same - move HP filter before C11-R13 ;)
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Re: Tech21 - Character Series.

Postby CloneME » 24 Oct 2014, 17:48

Has anyone successfully modded one of these for less noise with the drive up?
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Re: Tech21 - Character Series.

Postby artaommahe » 31 Oct 2014, 16:58

CloneME, it's opamp noise, so use them with low noise value(e.x.e TLC2272)
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Re: Tech21 - Character Series.

Postby azrael » 11 Nov 2014, 18:01

Stephanovitch wrote:I have mesured value of the California Joyo:
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(R4) |   10k (R4) |   10k   |
E1      |  open   |   18n   |            |    22n    |  10nF   |   open   | 18n(C3) |  open (C3) |   22n   |   Input &
Cin     |   22n   |   22n   |            |    22n    |  22n    |    22n ? | 22n(C1) |   22n (C1) |   22n   |  filtering
C2      |   47n   |   47n   |            |    47n    |  open   |    47n ? | 47n(C2) |   47n (C2) |   47n   |
--------+---------+---------+------------+-----------+---------+----------+---------+------------+---------+
C5      |   22n   |   10n   |            |    22n    |   10n   |    22n   | 3n (C8) |   10n (C8) |   22n   |
C6      |   22n   |   10n   |            |    22n    |   10n   |    15n   | 82p(C7) |  open (C7) |   22n   |
R6      |    1k   |    1k   |            |     1k    |    1k   |     1k ? | 1k (R6) |    1k (R6) |    1k   |  Character
R7      |  100k   |  100k   |            |   open    |  100k   |   100k   | 100k(R7)|  100k (R7) |  100k   |   pre-EQ
R9      |    1k   |  3.3k   |            |   3.3k    |  3.3k   |   3.3k   |3.3k(R10)|  3.3k(R10) |  3.3k   |
--------+---------+---------+------------+-----------+---------+----------+---------+------------+---------+
R14     |   47k   |   33k   |            |    47k    |   33k   |    33k   | 33k(R24)|  33k (R24) |   33k   |
C14     |  470p   |  470p   |            |   180p    |   470p  |     ?    |470p(C17)| 560p (C17) |    ?    |  HP sim
C15     |  2.2n   |  2.2n   |            |   2.7n    |   2.2n  |   2.2n   |2.2n(C18)| 2.8n (C18) |  4.7n ? |
--------+---------+---------+------------+-----------+---------+----------+---------+------------+---------+
C20     |   10n   |   22n   |            |    18n    |   10n   |    15n   |15n(C25) |  22n (C25) |   18n   |   MID
C21     |   10n   |   22n   |            |    22n    |   10n   |    15n   |22n(C24) |  22n (C24) |   22n   |    EQ
--------+---------+---------+------------+-----------+---------+----------+---------+------------+---------+
*Not used


Which universal schematic does this refer to? Some of the links in the thread are to incomplete or dead images.
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Re: Tech21 Character Series: anybody cracked one open yet?

Postby av500 » 29 Jan 2015, 22:08

mxrmxr wrote:
BTW, just got hold of a Sansamp PSA-1 rack preamp. Maybe that can be the next project after this one :wink:


Hi, don't know if you saw, I just posted PSA-1 traces and schematics: viewtopic.php?f=7&t=25708
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Re: Tech21 - Character Series.

Postby gregchill » 14 Nov 2015, 12:45

Has anyone got a schematic for the british

Cheers
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Re: Tech21 Character Series: anybody cracked one open yet?

Postby JFace » 04 Jan 2016, 00:08

mxrmxr wrote:o.k here's the resistor values for the 'Goop Hybrid Module'.

This little baby still had a few surprises left.

R104 measured open circuit. My initial reaction was 'shit I've damaged it during the de-goop'. But no, closer inspection with a magnifying glass revealed that the laser trimming has cut completely through and across the resistive element, making it an open circuit. Phew, I can breath again. So, this resistor is not used.

R102 measured 218K laser trimmed. You can clearly see a couple of short laser cuts in the resistive element with a magnifying glass. So, this resistor will be 220K.

R106 measured 218K laser trimmed. You can clearly see a couple of short laser cuts in the resistive element with a magnifying glass. So, this resistor will be 220K.

R101 Measured 221K laser trimmed. You can clearly see a couple of short laser cuts in the resistive element with a magnifying glass. So, this resistor will be 220K.

R103 measured open circuit. Again, closer inspection with a magnifying glass revealed that the laser trimming has cut completely through and across the resistive element, making it an open circuit. So, this resistor is not used.

R105 measured 100K laser trimmed. You can clearly see a couple of short laser cuts in the resistive element with a magnifying glass. So, this resistor will be 100K.

R100 measured open circuit. Again, closer inspection with a magnifying glass revealed that the laser trimming has cut completely through and across the resistive element, making it an open circuit. So, this resistor is not used.


Ok, I realize this is an old post, but after breadboarding this schematic and hearing other's DIY build recordings, I have to ask, are we certain that the open circuit resistors are indeed resistors? With the amount of noise generated at the gain stage, and the obvious lack of capacitors compared to other tech 21 circuits, this leads me to believe these are in fact capacitors. Does anyone still happen to have this deconstructed and able to check the capacitance of: R100, R103, and R104?
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