| Electronics > Beginners |
| Op amp based preamp supply. Charge pump, single vs symmetrical & ripple |
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| dazz:
--- Quote from: spec on November 27, 2018, 03:44:41 am ---Could you please confirm that you will be using a 9V PP3 battery to power this pedal? --- End quote --- That's up to the user/builder of the pedal. I personally never use batteries, I have a cheap 9V PS that I slapped a linear regulator in front. I don't require much current at all for the few pedals I use. --- Quote from: spec on November 27, 2018, 03:44:41 am --- In any case, the approach that seems to be the most economical and lowest risk is to use a 9V to +-15V power supply module. I havn't done a good search but something like this is what I have in mind: https://www.aliexpress.com/item/8W-2-5-15V-to-15V-Dual-Output-power-supply-DC-DC-Step-up-Converter-module/32789671683.html --- End quote --- I ordered a couple of those just two days ago, hehe. In principle for testing purposes, I'd prefer to integrate the converter in the board if I can find a reasonable solution, but using one of those is certainly a possibility. --- Quote from: spec on November 27, 2018, 03:44:41 am ---just out of interest, what guitars do you have? --- End quote --- Just a 90's Fender Mustang MIJ and a cheap chinese strat copy. I'm not a great guitar player at all and I only play at home these days, don't really need more than that. --- Quote from: spec on November 27, 2018, 03:44:41 am ---PS: if you run the opamps from +-9V, as you suggested, the sound would change, not due to the headroom or noise considerations but because the opamp itself is operating from lower rails. This effect is not so marked in newer opamps, but more so with the older opamps. --- End quote --- Damn, I see. Thanks for letting me know, that seals the deal for anything but a full +/-15V solution then |
| spec:
I mentioned about capacitors affecting the sound. Just in case, the CDE 715 and 716p orange drop polypropylene capacitors are very much favored in the guitar amp world (without going crazy on price). Data sheet attached. At the other end of the spectrum ceramic capacitors give a gritty sound which some players like. y5U dialectic in small leaded or surface mount versions have the greatest effect. |
| dazz:
Damn it, look at this in the product description of those boards in aliexpress: 1 Due to the diode partial pressure, the voltage of -Vo is lower than +Vo 2 In order to obtain a more stable voltage, it is recommended that the output is greater than 15MA I guess I could add a diode in series with +V to make it more symmetric, and a resistors in parallel with the preamp to increase load and go above 15mA? --- Quote from: spec on November 27, 2018, 04:14:11 am ---I mentioned about capacitors affecting the sound. Just in case, the CDE 715 and 716p orange drop polypropylene capacitors are very much favored in the guitar amp word (without going crazy on price). Data sheet attached. At the other end of the spectrum ceramic capacitors give a gritty sound which some players like. y5U dialectic in small leaded or surface mount versions have the greatest effect. --- End quote --- Thanks, I will include that info in the build instructions :-+ |
| spec:
--- Quote from: dazz on November 27, 2018, 04:10:49 am ---I ordered a couple of those [9V to +-15V modules] just two days ago, hehe. In principle for testing purposes, I'd prefer to integrate the converter in the board if I can find a reasonable solution, but using one of those is certainly a possibility. --- End quote --- You can mount the PSU modules on the board, just like a component, or am I missing something? --- Quote from: dazz on November 27, 2018, 04:10:49 am ---Just a 90's Fender Mustang MIJ and a cheap chinese strat copy. I'm not a great guitar player at all and I only play at home these days, don't really need more than that. --- End quote --- Yamaha FG350W (1981), Washburn WLD20S, and Crafter ST120 strat copy- can't play any of em :palm: Just sniped a Fender Deluxe 112+ combo for a song on ebay. The voice coil connecting wire has pulled of the cone and snapped under the dust cover- must get around to fixing it. :) |
| spec:
--- Quote from: dazz on November 27, 2018, 04:23:38 am ---Damn it, look at this in the product description of those boards in aliexpress: 1 Due to the diode partial pressure, the voltage of -Vo is lower than +Vo 2 In order to obtain a more stable voltage, it is recommended that the output is greater than 15MA I guess I could add a diode in series with +V to make it more symmetric, and a resistors in parallel with the preamp to increase load and go above 15mA? --- End quote --- That module is just the first one in Google. It is just an example. But all the same, the minimum current draw is no big deal and is a requirement for many PSUs. (even the LM317, LM337 three-terminal regulators). Minor differences in the PSU rail voltage should make little difference- you will see more variation in sound between different samples of the opamps, especially different ages and suppliers. |
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