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Messages - voltwide

#1
Preamps and Effects / Re: active guitar
February 26, 2016, 08:33:37 AM
Finally the New Chinese Year celebrations are done and my pcbs (20x30mm) arrived today.
Later I will test and put one into my strat.
#2
Amplifier Discussion / Re: KMD GV-60D take-apart problem
February 13, 2016, 02:17:51 PM
There are combos out where you have to remove the front baffle before removing the chassis!
#3
I do it like this. What you see is a part of some small flyback converter I am just working at. Actually it works :)
#4
The main problem with SMD are our degenerating eyes.  Equipped with a pair of high magnifying  spectacles and a 2mm solder tip with my 50 years old weller soldering station I solder prototypes on perfboard  including SMD0805/0603, Mini-Melf and SOT-23. Considering ruggedness against EMI (cell phones!) the smaller dimensions of SMD are superior to THT solutions. And populating a proper layouted SMD-PCB does not take more time than a THT-Version.
just my 0.02€
#5
Preamps and Effects / Re: active guitar
February 03, 2016, 06:09:47 PM
This tone control shows a quite different response compared to the traditional pot - capacitor combination. I choose a linear response  for the TONE but a logarithmic for the VOL.
#6
Preamps and Effects / Re: active guitar
February 03, 2016, 09:40:45 AM
If audio taper means logarithmic response, the answer is no. The spice potentiometer simulates a linear response.
This is the spice symbol I used:
#7
Preamps and Effects / Re: active guitar
February 03, 2016, 05:18:44 AM
Please note that the file extension ."txt" should be removed before loaded into LTSpice
#8
Preamps and Effects / Re: active guitar
February 03, 2016, 05:16:46 AM
LTSpice is the tool I designed this circuit with. For playing around I will add the simulation file
#9
Preamps and Effects / Re: active guitar
February 03, 2016, 05:11:26 AM
Yes, this indicates a test point reserved for the wiring, same sort as input and pos voltage supply.
#10
Preamps and Effects / Re: active guitar
February 03, 2016, 03:17:23 AM
you are right, placing the buffer at the input of your amp is too late. Nonetheless this can improve sound if input impedance of amp is too small - and that is often the case.
I would expect no problems with the increased output of humbuckers - keep in mind that the voltage gain is less than unity. Using a 9V-Battery allows voltage upto 2Vrms (i.e. 6Vpeak-to-peak) without distortion - and that is pretty much.
The most important part for tweaking is the resonant capacitor which sets the frequency range of the tone control. Depending on the pick-up impedance and your personal taste I would expect anything between 1nF and 10nF.
#11
Preamps and Effects / Re: active guitar
February 01, 2016, 07:25:36 PM
In that case the resonant peak can be set between 1,4kHz and 4kHz. The pickup is not the original Fender single coil but some stacked humbucker with 12kOhm DC-resistance.
Adopt this circuit to different pickups by tweaking the resonant capacitor C3 (here 3.3nF).
The JFETs shown are SMD-types provided by ON-semi/Sanyo and can be replaced by 2SK170 or similar.
#12
Preamps and Effects / Re: active guitar
February 01, 2016, 07:16:27 PM
And finally TONE-contral at max position
#13
Preamps and Effects / Re: active guitar
February 01, 2016, 07:14:41 PM
Now somewhere in the middle
#14
Preamps and Effects / Re: active guitar
February 01, 2016, 07:13:43 PM
Measuring The Frequency Range

Using my favourite audio-analyzer program ,,ARTA" and a PC with a sound card (behringer UCA-202) it is quite easy to measure the resonant peak according to the TONE-control setting. Line-Out (right) feeds via a series resistor of 3.3megOhm the pickup. Line-In (left) is connected to the guitar jack.
Starting with the TONE-control in minimum position

#15
Preamps and Effects / Re: active guitar
February 01, 2016, 07:03:35 PM
The TONE pot is 50k linear, the VOL pot 50k log.
C1,C3,C4,C5 are film caps. C2, C6 are ceramic/MLCC.