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Amplifier Discussion / Re: Fried Ampeg SVT-200T
« on: February 08, 2019, 05:27:46 AM »
toast resistors, fried amps, fused relays......Why're geeks always speaking so FuNnY?
In my opinion the problem might be caused by neutral wire breakdown in the club , which could lead to a 380-volt high voltage on mains.
It's tragic but, even switching power supply modules can't handle such a CRAPPY voltage so always use a surge protecting extension cord

Amplifier Discussion / Re: Reverse polarity protection
« on: February 08, 2019, 05:19:18 AM »
Quoting from Youtuber ElectroBoom, you need a FULL BRIDGE RECTIFIER!……no, a single puny diode (1n4007) would be ok.

Amplifier Discussion / Re: parts
« on: November 28, 2018, 09:17:12 AM »
As for signal generator, a cheap MP3 player with several WAV files inside(100hz sine wave, 1khz sine wave, 12000hz sine wave, 10hz to 24000 hz sweep, white noise, pink noise) is a pretty good choice. Smartphones with portable DAW software like Garage Band, Caustic 3 or FL Studio Mobile are much better choices.

Amplifier Discussion / Re: Fender Chorus Distortion Problem
« on: November 28, 2018, 09:03:48 AM »
Hi there!
I'm keen to help you but …… It seems that the information you offer is a little bit limited.
First, you can try using a 3.5mm TS to 6.35mm TS audio cable to feed line-level sine wave into FX return jack. If the sound is distorted, the problem is in the power amplification section.
If it's not distorted, then the power section is OK. Check if the lead channel works as common to probe out whether the problem is only on the clean channel or not.
If the lead channel is also broken, then the problem might be at the input stage(probably the feedback resistors are not well soldered )Otherwise, it is out of my range of ability and I must apologize that I'm unable to help you further.

Amplifier Discussion / Re: OK to run Marshall Lead 12 into 4 ohm load?
« on: November 28, 2018, 08:44:51 AM »
If your amp has 2x8ohm speaker outputs which are paralleled, it will be certainly OK to use 4ohm load. However, it'll be dangerous to use 4 ohm load on amplifiers which have only ONE 8ohm output-The current going thru the transistors will be doubled and they'll overheat and, plausibly, burn themselves down under such a current while using original cooling systems so using larger heat sinks and adding fans might be the first thing essential to be done. Replacing a transformer may help to prevent overloading and burning among the area with mains voltage but NEVER use any transformers with higher output voltages. Use ones with the same voltage and higher output current instead. In addition, don't forget to check the rectifier circuit and the fuse to prevent potential overloading.

The Newcomer's Forum / Re: Bench Setup
« on: October 15, 2018, 09:39:25 AM »
For safety reasons, a hold-down type pedal switch(It activates while you press it down and deactivates as soon as you release it) might be connected in series with the powerboard and then, while you're zapped, you release your feet and then the power goes off and it saves your life. Good gadget.

Preamps and Effects / Re: Nice: op-amp swap on Yamaha FX-500 processor.
« on: October 15, 2018, 09:34:40 AM »
Ha, double-precision NE5532s, great idea. They're usually used in HI-FI audio products and you used it, inside a guitar effects module!

Schematics and Layouts / Re: Fan control, indicating, proportional
« on: October 15, 2018, 09:32:04 AM »
Good idea it might be, but using a transistor which works in linear section to drive a fan is likely to generate lots of heat. As guitar amp geeks, most of us have several Op-Amps and it might be a better idea to build a PWM(pulse width modulation) speed controlling circuit instead of a linear one. As temp probes, LM35 is a great choice for its voltage output exactly mapped to the centigrade temperature. Feeding the signal and another sawtooth or triangle signal - it could be easily generated by using a NE555 timer chip - into the opamp(let it work as a comparator) and use mosfets (try irfz44 or 75nf75) as switching components. Hope it'll work well!

Amplifier Discussion / Re: Thinking about building a SS amp
« on: October 14, 2018, 09:17:57 AM »
You can start with combining a booster(as the input stage), a distortion pedal, a speakersim(Visit for the PCB/schematic) and an amplifier module which is sold on Taobao or Amazon or other Internet shops

I do not know what does the circuitry of CODE amps exactly consist of. However, it's a good idea to try finding a  line-level signal around the amp chip using a VU meter or a pair of computer speakers with probe made of alligator clips, 1/8'' TRS lines and a 3.3uf cap(in order to block out the DC bias which would fry your speakers) . Once you've probed out the signal successfully, you can then find the connection of it to the preamp, cut it, and put the LOOP circuit between the gap. Opamp buffers might be added in order to deal with the impedance problems. Good luck!

Amplifier Discussion / Re: Power on LED.
« on: October 14, 2018, 09:04:53 AM »
Green LEDs, especially extra-bright ones, are no doubt battery eaters. Using a red one with a resistor with higher resistance (Just let the LED glow slightly) will work.

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