Tech21 - Character Series.  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
Giaime
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Post by Giaime »

CloneME wrote:Has anyone successfully modded one of these for less noise with the drive up?
Hi, I just modded mine with TL974 opamps, even lower noise than TLC2272 and they sound just as good as the originals 8)

ericlaw02
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Post by ericlaw02 »

Hi there, I successfully modified my Joyo British into a VT Bass, thanks to this thread!

For anyone else who wants to attempt the same mod, I have uploaded my own pictorial reference for the part substitutions between the British/VT Bass (based on the tables from this thread). The SMD capacitors/resistors to be replaced are all 0603 (1608 metric) sized.

It sounds pretty much identical with same settings when comparing to VT Bass reviews on YouTube.

I also attempted the speaker sim bypass mod as per https://www.freestompboxes.org/viewtopic.ph ... 5&start=20, but the treble gain is a bit too much even when plugging into the effects return. I think I might attempt the additional 22k-?nf 6db lowpass filter (like the VT Bass V2) with an on-on-on switch later.

I also thought of adding an XLR out by nicking the BDDI's balanced out circuit, but that would mean sacrificing the ample space for the 9V battery. (also I would have to make an layout myself, because there doesn't seem to be a small enough layout that just has that part, which means more work)
Attachments
vtbass.jpg

medvege
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Post by medvege »

Sorry for the old thread
Recently I got Bass Fly Rig, which i almost loved.
However, I play in metal band and personally like open highs.
Speaker sim in this unit is nice, but cuts all the highs above ~4kHz.
Turning higs up actually adds clank, but nothing in the air
I don't want to make speaker sim defeat, moving low pass freq will be better
I found two ways in this thread

1) bajaman's advice will be reducing R14:
R14 is reduced from 47k to 33k in the British - Only a slight difference in the high frequency rollof characteristic ( British = 4.8khz, and Blonde = 4.2khz) I guess this is the difference with the Celestion speaker response model in the British compared to the Jensen speaker response model in the Blonde 
2) Darkglass advising increasing R18:
For getting the same funcioality as the new Character pedals, I would increase the value of R18. In the Liverpool is 33k, I would try anything from 47k to 100k.
Which way do you think will be better, or may be another one? Thank you!

*guessing Bass fly rig will be another story...

medvege
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Post by medvege »

Anyone?

thehallofshields
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Post by thehallofshields »

Looking at the schematics posted, I noticed that R5 is not consistent between models.
This is part of the buffer stage and forms an R-C network with C2.

Also is anyone knows what R5 is on the Joyo pedals, please share.

thehallofshields
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Post by thehallofshields »

thehallofshields wrote:Looking at the schematics posted, I noticed that R5 is not consistent between models.
This is part of the buffer stage and forms an R-C network with C2.

Also is anyone knows what R5 is on the Joyo pedals, please share.
R5 is likely R5 on the Joyo, but I'm not sure about the Tech21 v2. If anyone has this info, please share!

karaman
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Post by karaman »

R5 in the SansAmps is R2 in the Joyo pedals. It is 22k in both my American and AC Tone.

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n4m3less
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Post by n4m3less »

bajaman wrote:I would suggest trying a value of 1n (possibly more) for the capacitor marked with a ?
This sets the high frequency rolloff when the speaker simulator cabsim switch is disengaged.
For the suggested value the high frequency response will be approximately -3db down at 8KHz.
Double the value (2n2) and the response will be -3db at 4Khz.
cheers
bajaman
Stupid question:
I have a VT bass v2 and if I would remove 6dB per octave high roll off filter when a sim Cab is disengaged just remove this cap marked with "?" ?
But this problem can also be bypassed by putting an equalizer pedal and boosting of 6db the 4.5khz?
Thanks

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AuditoryDriving
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Post by AuditoryDriving »

Too bad no one seems to have the values for the Leeds and California pedals, it would be very interesting and educational.

i ll never get tired of saying those pedals are brilliant ( i have the blonde and the liverpool)!

kcstratslinger
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Post by kcstratslinger »

Hey medvege. Did you ever find an answer or make an attempt at the R14/R18 mod? I have a Blonde that seems too dark. I would like the highs to be more extended but can't find any info anywhere.

jhergonz
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Post by jhergonz »

Done reading this whole thread, and this is awesome! thanks to all of you guys for the information you shared! this is very educational. :applause: :applause: :applause:

rrr969
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Post by rrr969 »

Ammoon "American sound" inside on the photos. They said that it is the same as joyo by the sound and the looks outside, here is the proof of the same circuit by the same factory.
Attachments
IMG_0264 - Copy.JPG
IMG_0263 - Copy.JPG

tommymariot
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Post by tommymariot »

can anyone tell me if there are differences between the various character modules?
I opened my hot rod plexi and found that it is very similar to the character series. the character module is ch33-10. Does the number represent the revision or is it a model identifier?

Antigua
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Post by Antigua »

I made bode plots of the voice control operation of the the four Joto "sound" models. It appears that the Actone, American and British models are all very similar, the main difference mostly being the particular band stop frequency in the middle.

The California Sound's voice knob has a wildly different function from the other three, more like a very broad high pass attenuation.

The way they all roll off below 100Hz and above 4kHz must be the combination speaker + microphone dynamic, because the speakers themselves typically respond past 5kHz.

All of the other knobs are set to 12. The input voltage was 50mV.

Image

Image

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Image

daeg
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Post by daeg »

Anyone have any idea why Tech21 discontinued these? They were pretty popular.

tommymariotti
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Post by tommymariotti »

Dear all, I'm interested to the Tech21 British Schematics but I can't find the thread.
Somebody can uplad it again or send me a PM with the latest scematics?

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