Xotic - BB Preamp  [traced]

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Re: Xotic - BB Preamp

Postby joeboo88 » 07 Nov 2011, 20:08

looks like there is a cut under r22, I built this a while ago and had no problem ( I'm not at home to check). Enlarge the picture to verify.
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Re: Xotic - BB Preamp

Postby andrapgm03 » 11 Dec 2011, 18:10

First of all, I want to know

1) What is the differences between JRC4558 and 4558 D when I place it in my BB preamp board ? I think it will be quite warm than 4558, but I believe there will be a great explanation about it here

2) I used 1N4006 for the diodes, it is good ? I used Glitterrattii from madbeans, with his latest mod http://madbeanpedals.com/projects/Glitt ... rattii.pdf, seems 3.5 don't have any working link so I decide look forward into new one, is it good ? just my question

3) What kind of resistor should I used, 1/2 Watt or 1/4 watt ? sorry for noob question, just to make sure if I have a wrong perception about 1/2 Watt or 1/4 Watt

Thanks all :D :D
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Re: Xotic - BB Preamp

Postby Frabbio » 11 Dec 2011, 19:11

The difference between the opamps is subtle, try to swap some e leave onboard the one you like best.
The diode is ok, and you can use both 1/2 and 1/4 watt resistor in this circuit, i suggest using 1/4 watt because of the smaller dimensions.
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Re: Xotic - BB Preamp

Postby pedalgrinder » 15 Dec 2011, 01:21

has anyone ever wanted to add a mid control to there bb preamp well opportunity knocks here is a cool mid range mod for the bb that doesn't effect the way the original circuit performs. so here it is enjoy!!!!!!! [smilie=bowdown.gif] [smilie=bowdown.gif] [smilie=bowdown.gif] [smilie=bowdown.gif] [smilie=bump.gif] [smilie=cactus_man.gif] [smilie=muffin.gif] [smilie=muffin.gif] [smilie=muffin.gif] [smilie=lol_xtreme.gif] [smilie=lol_xtreme.gif] [smilie=lol_xtreme.gif] [smilie=lol_xtreme.gif] [smilie=lol_xtreme.gif] [smilie=lol_xtreme.gif] [smilie=lol_xtreme.gif] [smilie=banana.gif] [smilie=banana.gif] [smilie=borgsmile.gif] [smilie=borgsmile.gif]


Mid frequency tone control.jpg
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Re: Xotic - BB Preamp

Postby lukatosh » 09 Mar 2012, 20:58

Hello Friends! ... I'm Lucas and I'm writting from Chile!

I've build the bb preamp (glitterati, madbean v3.5)...and iwould like to add more gain to it... how can increase gain in the pedal?

excuse my bad English :/

thanks so much!
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Re: Xotic - BB Preamp

Postby bigorangefan79 » 09 Mar 2012, 21:08

lukatosh wrote:Hello Friends! ... I'm Lucas and I'm writting from Chile!

I've build the bb preamp (glitterati, madbean v3.5)...and iwould like to add more gain to it... how can increase gain in the pedal?

excuse my bad English :/

thanks so much!



An easy way would be to change the clippers to germanium diodes. Or you could always put a boost in front of it, maybe even change the input buffer to jfet boost. Another easy one would be to increase the 10k resistor (r5), that would not allow you to turn the gain down as much. But just put a 100k, 220k, 500k resistor or whatever you want in there and see if you like it.
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Re: Xotic - BB Preamp

Postby lukatosh » 09 Mar 2012, 21:45

Thanks!

i was asking because comparing my pedal with videos on youtube my pedal has less gain.... i've re-checked al component values and everything is ok :/

i've used 2n5088 instead of 2n3904 and a JRC4558 and TL072 for the ICs

What else do you suggest to increase the gain?
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Re: Xotic - BB Preamp

Postby pedalgrinder » 09 Mar 2012, 22:16

he wants more gain as in the distortion the easiest way to change the gain rather than stuffing with the circuit is the the old formula rf/ri so change the 1m gain pot to 2m if you can get your hands on one. Or change the the 4k7 resistor going to vb from that op amp to a 2.2k or even change it to a 5k trimmer so you can adjust your gain to taste then leave it. Op amps circuits are not much different from each other.
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Re: Xotic - BB Preamp

Postby jymaze » 12 Mar 2012, 13:01

If you don't like the gain as it is, just put a bigger value gain pot because changing the opamps and the transistor will not change the gain at all. i have seen things like that said around the forum, that different active components yields different gains: while it is maybe sometimes true for jfet, it makes no sense that swapping an opamp or a bipolar transistor with emitter degeneration makes any difference in gain which are both high gain devices and the real gain is defines by the feedback structure built around them. On the other hand, there may be a subtle change in frequency response that can change the "perceived gain". But once again, the difference in frequency response should be very subtle too when using modern components.
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Re: Xotic - BB Preamp

Postby pedalgrinder » 18 Mar 2012, 13:19

yeah as i said rf/ri yah da yah da yah da increase the 1m pot not rocket science!
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Re: Xotic - BB Preamp

Postby lukatosh » 14 Apr 2012, 19:34

is there a way to get more volume out of the pedal??

Thanks!
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Re: Xotic - BB Preamp

Postby pedalgrinder » 16 Apr 2012, 07:53

i believe if you increase the value of r16 based on madbeans layout the 47k i would use a pot as a variable resistor to adjust it to what level you want. so you could use a 100k linear pot start at half way until you get the desired increased output volume you want. Not sure how much head room would be left but iam sure theres a bit to play with. once desired output is achieved read value of put out of circuit and replace with same or as close value of resistor. From what i can see that increases the gain of the second op amp and should give you the desired more output. or hotter signal whatever you want to call it. Have fun
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Re: Xotic - BB Preamp

Postby kacper.nawrocki » 17 May 2012, 13:46

What is the difference between standard bb and mb?

Pictures of BB preamp MB are here
http://www.dirtbox.net/features/reviews-archive/xotic-effects-bb-preamp-mb-mid-boost/

I have a BB AT, pcbs are very similar
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Re: Xotic - BB Preamp

Postby Frabbio » 22 May 2012, 11:09

Hi, here is my version of the pedal, with mid control added using the schematic provided by pedalgrinder.
Pots are Pcb mounted, dimensions are 87x59 mm.
This version includes the stereo gain pot and the Schottcky diode in series with the 9 volt supply, if you don't want to use it put a jumper instead.
On the layout image the yellow lines are jumpers.
Suggested choice for the quad-opamp (tone control) is a TL074.
Good DIY
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Re: Xotic - BB Preamp

Postby fretzburner » 06 Jul 2012, 01:54

Hello,as i checked the schematics for this circuit there's only two feedback diodes but on the actual unit seems four diodes.Just can't see it clearly because of goop but really looks like 4 identical shape and size.I'm confused with this diode thing.
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Re: Xotic - BB Preamp

Postby diafebus » 10 Jul 2012, 14:17

Hey guys!
In http://www.madbeanpedals.com/ they had a pedal called, Glitterrattii that is a clone of the BB preamp… I compared my build next to an original BB preamp and it sounded almost exactly the same, with the same background noise and same kind of distortion and bass and treble response, maybe, my clone had a little boost on hi-mid freq. but nothing extremly different.
I can post the project pdf here. I don't know why they removed it from their webpage...

https://dl.dropbox.com/u/1416648/DIY/pd ... i_ver4.pdf

I hope you enjoy it! :D
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Re: Xotic - BB Preamp

Postby Dave37LP » 03 Jan 2014, 04:19

sinner wrote:
phibes wrote:Paco, what does the PCB screw to in the case? I never looked into the Xotic stuff too much.



Timothy, It holds the second PCB with pots and one resistor attached to it



Hi all friends, Hi Sinner, what resistor of the Kusi's schematic (seems it's the most exact schem of the real BB, including the Led switching) that you mention to Timothy, is located at the second PCB with pots. Another question is about the real value and type of the Volume pot, in that schematic indicates a dual gang pot, one part acts like a filter and the other one acts like a normal level control. Why, if that could be the real schem, is this structure supressed in the all around internet schematics of the BB, it has no audible difference? Sorry for my bad English, hope it be understandable. Thanks in advance,

Greetings (and Happy New year 2014!!)

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Re: Xotic - BB Preamp

Postby Frabbio » 06 Jan 2014, 12:21

Kusi's schematic is the most accurate schematic you can find, the only difference with the real bb preamp is that the diodes are four, not two. And there is a big difference between the dual volume control and the single volume control.
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Re: Xotic - BB Preamp

Postby Dave37LP » 22 Jan 2014, 02:00

Frabbio thank you very much, I have analyzed all available photos of the layout of the BB Preamp on the internet and they all fit in the schematic of Kusi, the question I have now is about the correct connection of the second part of the volume pot (the filter part), in the schematic I don't notice what is the correct orientation of the potentiometer. I've Included an image with A or B options. Is that filter cutting lows while increasing the volume or vice versa? Again, very much thanks for your kindly reply.

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Re: Xotic - BB Preamp

Postby Frabbio » 25 Jan 2014, 17:01

Hi, B is the correct way to wire that pot.

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