DID I TYPE THAT? I meant there's no reason to jumper the small film cap I recommend removing.... WTF was I thinking?
The .22uf caps are the input capacitors that I highly recommend replacing with 1.5uf MKP capacitors, or whatever you have that's known to be a good input cap and is 1.5uf+
It is likely that the little orange capacitor used for power bypass, should be replaced with ceramic disc or x7r. Ceramic has greater tolerances for wrong-size bypass usage.
That's because (explanation!) other types of capacitors would have to be closer to the correct size if ringing weren't the desired result. The size of a bypass cap matters, and for this exercise, please assume that 100n is the wrong size. Indeed, if electrolytic decoupling were working, then 100n is too large for bypass, will fight, and ringing is the result. Why that is on almost every schematic is not something I could know. Also, can't guess it either.
Common "placeholder" values do serve a goodly purpose--that indicates a spot where some fine tuning could be useful.
That's because (explanation!) other types of capacitors would have to be closer to the correct size if ringing weren't the desired result. The size of a bypass cap matters, and for this exercise, please assume that 100n is the wrong size. Indeed, if electrolytic decoupling were working, then 100n is too large for bypass, will fight, and ringing is the result. Why that is on almost every schematic is not something I could know. Also, can't guess it either.
Common "placeholder" values do serve a goodly purpose--that indicates a spot where some fine tuning could be useful.
If I understand correctly, installing smaller value capacitor is what's necessary to get rid of the ringing and improve sound quality?
Not trying to contradict your explanation, but some pages back I read somebody installed 1uF which is bigger than stock, with good results. Which is why I put 1uF in my dumb photoshopped board above LOL. Okay noted, remove the small film cap, replace the diode with jumper wire.
Strangely choice is limited for 1.5uF, I can get MKP, MKS Wima, and Nichicon Muse ES BiPolar in 1uF, and the same Muse ES in 2.2uF.
Can I use bipolar cap in this situation? Should I pay attention which leg installed in which hole?
If bipolar cannot be used, I might install 2x1uF in series. Thanks again!
I've removed the small film cap, and replaced the diode with jumper wire. The faint ringing stopped but now there's an audible hiss. I put the small film cap back in, and the hiss is still there. When I touch the pot, there's a hum. Could this be a grounding issue? I use SMPS brick like this:
Small film cap back in place, diode replaced with wire.
Any help would be appreciated.
Small film cap back in place, diode replaced with wire.
Any help would be appreciated.
Note: There is hum when I touch the pot since new, so this is not related to the mod. The amp kinda opens up after I removed the small cap and jumper'd the diode, but there's the hiss.
I have ordered new pots, 20K and 50K, currently installed is 50K. I read the pot resistance should be lower than amp input resistance, the amp's is 25K with 30K typical, so 20K is a good choice? Up until now I've never turned the volume knob above 9 o'clock. This amp is loud for me in my room
I have ordered new pots, 20K and 50K, currently installed is 50K. I read the pot resistance should be lower than amp input resistance, the amp's is 25K with 30K typical, so 20K is a good choice? Up until now I've never turned the volume knob above 9 o'clock. This amp is loud for me in my room
Each pair should be connected internally in the jack, so it shouldn't matter. Do you have a DMM? It's very helpful for both checking for bad/bridged connections and learning how the entire circuit works.
Mine were delivered with badly bent pots, and I replaced them with the same 50k pots. They work pretty well.
Mine were delivered with badly bent pots, and I replaced them with the same 50k pots. They work pretty well.
The hiss you can hear with your ear next to the speaker never goes away as far as I know.
It sounds like you have a ground not connected correctly or an antenna somewhere that should be connected to a ground.
Those pots are pretty shitty, and more than one person has had one that was cracked or damaged.
It sounds like you have a ground not connected correctly or an antenna somewhere that should be connected to a ground.
Those pots are pretty shitty, and more than one person has had one that was cracked or damaged.
Mike, Destroyer (Salis? ��
I can hear the hiss in my listening position, don't have to put my ear next to the speaker. This is louder than the initial ringing. In build guide v.2 you mentioned 'bridge the signal paths you took out' - should I put jumper wire where the small film cap was?
Would having three conductor power cable help in this case? Here we use standard two prong Euro style plug. I'm starting to think this is not grounding issues, as the hiss is louder after the mod and power section hasn't been changed at all.
Thanks for handholding me. Have a pleasant day everyone.
I can hear the hiss in my listening position, don't have to put my ear next to the speaker. This is louder than the initial ringing. In build guide v.2 you mentioned 'bridge the signal paths you took out' - should I put jumper wire where the small film cap was?
Would having three conductor power cable help in this case? Here we use standard two prong Euro style plug. I'm starting to think this is not grounding issues, as the hiss is louder after the mod and power section hasn't been changed at all.
Thanks for handholding me. Have a pleasant day everyone.
It's hard to imagine the hiss is related to the small cap you removed given the fact that you have hiss when you put one back in. You really don't want to put a wire in place of the cap. That would be a dead short in the circuit. BTW no one else has reported a loud hiss, so let's look for problems, not consider parts that cause ringing.
Can you provide a picture of the bottom side? Does anything change if you wiggle the pot? How much hiss was there to begin with? Your SMPS does look like it accepts safety ground, but I'd hope that wouldn't affect it. Have you used this SMPS with other projects and not had problems?
Did you place it near anything? The heatsink can pickup a lot of noise. You can isolate the chip from it pretty easily with a TO-220 washer and TO-3 insulator.
Can you provide a picture of the bottom side? Does anything change if you wiggle the pot? How much hiss was there to begin with? Your SMPS does look like it accepts safety ground, but I'd hope that wouldn't affect it. Have you used this SMPS with other projects and not had problems?
Did you place it near anything? The heatsink can pickup a lot of noise. You can isolate the chip from it pretty easily with a TO-220 washer and TO-3 insulator.
I agree, the small cap on or off doesn't change the hiss.
Picture of the bottom side I can provide later when I get home.
The pot is not moving in relation to the board, it is soldered well on all six legs. But when I touch the body or the shaft, there's a hum. When I turn the volume up with no music playing, the hum gets louder with 12 o' clock being the loudest then fades as I turn it up further.
The hiss on the stock board was faint, I had to put my ear close to the speaker to hear it. And it was a higher frequency than what I have now.
I bought this SMPS new for this project.
I place it on a low desk, a mess of cables (RCA, stereo mini, etc) and two speakers on each ends. I can find these:
Mica insulator
Came complete with bushing
Thanks again.
Picture of the bottom side I can provide later when I get home.
The pot is not moving in relation to the board, it is soldered well on all six legs. But when I touch the body or the shaft, there's a hum. When I turn the volume up with no music playing, the hum gets louder with 12 o' clock being the loudest then fades as I turn it up further.
The hiss on the stock board was faint, I had to put my ear close to the speaker to hear it. And it was a higher frequency than what I have now.
I bought this SMPS new for this project.
I place it on a low desk, a mess of cables (RCA, stereo mini, etc) and two speakers on each ends. I can find these:
Mica insulator
Came complete with bushing
Thanks again.
This is the stock board as I'm sure everyone is familiar with:
Took an insulator and bushing from old PCB
After putting the insulator, the hiss is now half as loud, and it's now back to the high pitch ring. Not sure what's happening here. I'll try to replace the pot when it arrives. I'm starting to think that the wires carrying the DC voltage is too small. Or not.
If anyone have any suggestion where to look, please let me know. Thanks~
Took an insulator and bushing from old PCB
After putting the insulator, the hiss is now half as loud, and it's now back to the high pitch ring. Not sure what's happening here. I'll try to replace the pot when it arrives. I'm starting to think that the wires carrying the DC voltage is too small. Or not.
If anyone have any suggestion where to look, please let me know. Thanks~
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Destroyer OS.,
Moved the bridge to the bottom, and while removing the LED I noticed it was installed backwards. Tried installing it the right way, but that didn't change the noise, so I left it off.
I tried to peek from the vent holes in the PSU and can only see one 47uF 400V.
I am planning to make a dedicated cap board like you explained on audiocircle, but currently don't have one. Speaking of which, how many 1500uF caps would you recommend for this amp, and what is the value of the resistor for RF noise reduction?
Here's the bottom pic
Thanks so much.
Moved the bridge to the bottom, and while removing the LED I noticed it was installed backwards. Tried installing it the right way, but that didn't change the noise, so I left it off.
I tried to peek from the vent holes in the PSU and can only see one 47uF 400V.
I am planning to make a dedicated cap board like you explained on audiocircle, but currently don't have one. Speaking of which, how many 1500uF caps would you recommend for this amp, and what is the value of the resistor for RF noise reduction?
Here's the bottom pic
Thanks so much.
Might I suggest you order a stock board and start to enjoy some music. I've had one for 3 years, it never gets turned off and there is no hiss.
Perhaps the hiss you are hearing is all part of the perceived sonic advantage of modding, making the little amp more tubelike or vinylesque?
Your solder holes where you removed stuff looks awfully dirty and could have some micro bridges to the nearby ground plane. Go over those holes with a clean hot iron tip to clean them up. The scrub with a brush and some alcohol to remove the cruddy flux and lead residue. See if that helps. You may have a bad part somewhere. Given that putting an insulator on the heatsink reduced the hiss I think the problem is a small short or a cold solder joint somewhere. Go over all joints and liquify the solder to remove the possibility of cold solder joints. Use a DMM to check resistance between ground and parts that should not be grounded. It's a defect somewhere because these amps are quiet. I have 8 of them and none have had hiss.
Sounds like a good idea, I can't see any obvious problems. His board doesn't even have the grounding path problem.
For off board caps I've come to prefer Nichicon KG over any configuration of smaller capacitors. 6000uf should be good, going over that won't hurt.