I see. My OPA2134 also has a very low offset, 1.7mv and 1.8mv. Never seen as offset as low as yours, though.
The compensation caps were causing oscillation. It’s why they are marked as optional for stability on the schematic... they need to be used only if needed.
The hum sounding quiet at the potentiometer extremes and the middle point, but louder everywhere else is the tell-tale of oscillation in this circuit.
The hum sounding quiet at the potentiometer extremes and the middle point, but louder everywhere else is the tell-tale of oscillation in this circuit.
@Logic800, putting the inputs on the side is a brilliant idea 
nice super short wire runs from there. Very nice indeed!
Which opamp are you using?
nice super short wire runs from there. Very nice indeed!Which opamp are you using?
Hi. I built this on a custom pcb and though it works, the mosfets barely get warm, and i have a huge power on/off thump.
i am using irf9610/610 pairs and everything else to spec.
also getting .6v drop on the bias resistors.
what are some voltage readings i should do, ect?
i am using irf9610/610 pairs and everything else to spec.
also getting .6v drop on the bias resistors.
what are some voltage readings i should do, ect?
Thanks twitchie. The op amp is the one supplied in the kit, didn't check type, but I have a AD823ANZ to try later.
Power Supply Problem
I just assembled the power supply for the voltage reference version. After I plug it in, only one LED lights. Anyone have any clue where the problem could be?
I just assembled the power supply for the voltage reference version. After I plug it in, only one LED lights. Anyone have any clue where the problem could be?
LED
I checked the LED, doesn't work in any direction. Checked all the solder joints, everything looks fine. Thanks.
I checked the LED, doesn't work in any direction. Checked all the solder joints, everything looks fine. Thanks.
Hello, I am a new member and this is my first post. I have built the Whammy amp and LOVE it! Thank you all for your hard work and support.
I have one question about adding an LED to the front panel as a power indicator. I read in the guide “If you want to use one of these as a light for the front panel you may, but it would be better to attach a different LED and resistor to the V+ and ground output of the raw PSU.” Can anyone help me with this as I don’t totally understand? For instance, can someone identify specific pads I should solder to? I’m sorry I don’t know better.
Ok, I guess I have a second question, lol. Will I be able to check the DC voltage from these two pads? I know I need to add a resistor on the positive leg of the LED and I think I can calculate the value as long as I can properly read the voltage.
Thank you in advance!
I have one question about adding an LED to the front panel as a power indicator. I read in the guide “If you want to use one of these as a light for the front panel you may, but it would be better to attach a different LED and resistor to the V+ and ground output of the raw PSU.” Can anyone help me with this as I don’t totally understand? For instance, can someone identify specific pads I should solder to? I’m sorry I don’t know better.
Ok, I guess I have a second question, lol. Will I be able to check the DC voltage from these two pads? I know I need to add a resistor on the positive leg of the LED and I think I can calculate the value as long as I can properly read the voltage.
Thank you in advance!
@loopyeddie - Welcome!
If you are using this guide -
WHAMMY headphone amplifier - diyAudio Guides
- It looks like you're at Step 8. Read ahead a bit to step 12 - "Testing the PSU". It will show you the pads for measuring V+ and the target value of ~+17V. Loaded, the PSU will put out ~15V per the schematic.
Edited to add the answer to your other question - you can solder your wiring to these pads. The positive pad of C9 may be most easily accessed from the bottom of the board after the cap is installed. You can add a wire to the top or bottom of the GND pad mentioned along with the other wire. There are other options, but since you'll already be familiar with the location of those two, I'd recommend using them.
If you are using this guide -
WHAMMY headphone amplifier - diyAudio Guides
- It looks like you're at Step 8. Read ahead a bit to step 12 - "Testing the PSU". It will show you the pads for measuring V+ and the target value of ~+17V. Loaded, the PSU will put out ~15V per the schematic.
Edited to add the answer to your other question - you can solder your wiring to these pads. The positive pad of C9 may be most easily accessed from the bottom of the board after the cap is installed. You can add a wire to the top or bottom of the GND pad mentioned along with the other wire. There are other options, but since you'll already be familiar with the location of those two, I'd recommend using them.
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Bipolar capacitors C12 / C17 / C22 / C25
Hello all Whammy enthusiasts,
I have now started to build my Whammy.
Can I also use bipolar capacitors with 47uF for C12 / C17 / C22 / C25?
Hello all Whammy enthusiasts,
I have now started to build my Whammy.
Can I also use bipolar capacitors with 47uF for C12 / C17 / C22 / C25?
I am in the process of doing the same thing. If you look at earlier threads from a week or so ago you will see all you need to know. There are options to connect to the unused resitors spaces adjacent to the PSU or alternatively connect direct to the secondary on the transformer which I will do. Any problems let me know. Best wishes
N
N
Sure can they tend to have lower distortion Anyhow. Maybe not the best for bypass but I have done it.
New Build
Hello, I set aside my board with the LED anomaly and decided to start fresh with the other board I have. I was out of LEDs so decided to build the “Resistor reference” version. I did not install caps at C9 or C28–should I have?
When I measure at C9, I get 20 volts, not 17. I also notice AC voltage is at 123, not 120. Are these issues related?
Should I be following the guide and measuring at R13 and R14, even though I have resistors there?
Sorry for the stupid questions, this is all new to me.
Hello, I set aside my board with the LED anomaly and decided to start fresh with the other board I have. I was out of LEDs so decided to build the “Resistor reference” version. I did not install caps at C9 or C28–should I have?
When I measure at C9, I get 20 volts, not 17. I also notice AC voltage is at 123, not 120. Are these issues related?
Should I be following the guide and measuring at R13 and R14, even though I have resistors there?
Sorry for the stupid questions, this is all new to me.
