Hey All -
Yesterday I assembled a cmoy amp using a schematic from the tangentsoft tutorial page (
http://tangentsoft.net/audio/cmoy-tutorial/.)
I can hear the music through it, but it sounds very tinny. I can't turn it up very far before the treble hurts my ears and the bass is barely there. Can anyone help me diagnose the problem?
I'm testing with a pair of Sennheiser HD-212's, which have very BOOMY bass, so it isn't the headphones...
Thanks and have a great weekend!
Sal
Yesterday I assembled a cmoy amp using a schematic from the tangentsoft tutorial page (
http://tangentsoft.net/audio/cmoy-tutorial/.)
I can hear the music through it, but it sounds very tinny. I can't turn it up very far before the treble hurts my ears and the bass is barely there. Can anyone help me diagnose the problem?
I'm testing with a pair of Sennheiser HD-212's, which have very BOOMY bass, so it isn't the headphones...
Thanks and have a great weekend!
Sal
Amp Values
I didn't stray from the schematic and parts recommendations on the tutorial website.
- Schematic - http://tangentsoft.net/audio/cmoy-tutorial/misc/cmoy-tangent-sch.pdf
- My resistors are gold-banded (10%?) and the op-amp is a
Burr Brown OPA2132PA.
- And yes, I cleaned the flux off.
I didn't stray from the schematic and parts recommendations on the tutorial website.
- Schematic - http://tangentsoft.net/audio/cmoy-tutorial/misc/cmoy-tangent-sch.pdf
- My resistors are gold-banded (10%?) and the op-amp is a
Burr Brown OPA2132PA.
- And yes, I cleaned the flux off.
Re: Re: Amp Values
Actually, I believe it sets the high-pass to 15.9hz:
http://tangentsoft.net/audio/input-cap.html
Not sure where you got 46.8hz from. I checked this against other RC filter calculators and it is correct from what I understand.
Tangent even states that the 0.1uF cap is a little on the low side, and he recommends 0.22uF to 0.47uF.
I guess I'll start with the easy questions until a picture is posted:
1) Did you use a 0.1uF cap or something lower in value?
2) Have you double-checked the values for all of your resistors
3) Have you double-checked that you laid everything out correctly? You can still get sound even if you don't wire things up correctly since it will pass through the feedback resistors to the output.
A picture is really optimal so we can see what's going on, though.
carlosfm said:
0.1uF input cap + 100k resistor to ground forms a high-pass filter at... 46.8Hz.
Nice schematic.
Change that cap for 1uF.
Actually, I believe it sets the high-pass to 15.9hz:
http://tangentsoft.net/audio/input-cap.html
Not sure where you got 46.8hz from. I checked this against other RC filter calculators and it is correct from what I understand.
Tangent even states that the 0.1uF cap is a little on the low side, and he recommends 0.22uF to 0.47uF.
I guess I'll start with the easy questions until a picture is posted:
1) Did you use a 0.1uF cap or something lower in value?
2) Have you double-checked the values for all of your resistors
3) Have you double-checked that you laid everything out correctly? You can still get sound even if you don't wire things up correctly since it will pass through the feedback resistors to the output.
A picture is really optimal so we can see what's going on, though.
Most common mistake on Cmoy is not connecting the various grounds: input jack, output jack, and rail-splitter center-point must all be connected together.
If you don't, the gain "should go to zero", but stray capacitive leakage in the tightly-built amp will spew treble.
For more Cmoy mistake-sharing, his forum is a good place. Someone there may recognize the problem from the symptoms.
If you don't, the gain "should go to zero", but stray capacitive leakage in the tightly-built amp will spew treble.
For more Cmoy mistake-sharing, his forum is a good place. Someone there may recognize the problem from the symptoms.
Update
First of all, I have some advice for those who may be considering building their 1st Cmoy. DON'T USE RADIOSHACK PROTOBOARD!!!
I decided to get nice components and scrimp on the board, and I've ended up having to buy and try another TWO boards because the three couldn't withstand the heat of tinning once and soldering once. The first board worked till I tried to resolder the faulty ground connections. In some areas of the board the copper just falls off from the temporary heat.
Needless to say this made some connections bad, so after transferring my setup twice and all that heat and stress on the parts, the dual power supply has uneven output. I think the caps in the power supply are burnt, everything else seems functional, but my multimeter doesn't have the capability to test the caps.
Two options now:
1. I can get better protoboard and replace the caps, and risk transferring the components AGAIN -
2. Or I can use the protoboard design, etching materials, and micro-components at my school. and find some way to adapt a full size OPA2132PA to a board with micro-components.
I don't really have any questions, but if any of you have advice I'll gladly take it.
First of all, I have some advice for those who may be considering building their 1st Cmoy. DON'T USE RADIOSHACK PROTOBOARD!!!
I decided to get nice components and scrimp on the board, and I've ended up having to buy and try another TWO boards because the three couldn't withstand the heat of tinning once and soldering once. The first board worked till I tried to resolder the faulty ground connections. In some areas of the board the copper just falls off from the temporary heat.
Needless to say this made some connections bad, so after transferring my setup twice and all that heat and stress on the parts, the dual power supply has uneven output. I think the caps in the power supply are burnt, everything else seems functional, but my multimeter doesn't have the capability to test the caps.
Two options now:
1. I can get better protoboard and replace the caps, and risk transferring the components AGAIN -
2. Or I can use the protoboard design, etching materials, and micro-components at my school. and find some way to adapt a full size OPA2132PA to a board with micro-components.
I don't really have any questions, but if any of you have advice I'll gladly take it.
I've built probably 30+ projects on the protoboards from ratshack and never had a problem. Are you overheating the copper traces? The only time I seem to lift traces is when my iron is cranked up on high.
What type of soldering iron are you using? If you're going to be building more stuff, I highly recommend getting even a basic regulated temperature iron.
To remove the caps and try again, radioshack has a handy $11 desoldering iron that works pretty well. Just another handy tool to have in your kit, especially if you decide to mod gear or rework projects.
Sometimes if you're building something for the first time around, use generic parts. That way you get a feel for the project and can use the "good" stuff later on. It's also a good way to tell how much a given circuit benefits from boutique parts. I also always buy a few spares of every part when I start a project in case I toast a few during the building process.
What type of soldering iron are you using? If you're going to be building more stuff, I highly recommend getting even a basic regulated temperature iron.
To remove the caps and try again, radioshack has a handy $11 desoldering iron that works pretty well. Just another handy tool to have in your kit, especially if you decide to mod gear or rework projects.
Sometimes if you're building something for the first time around, use generic parts. That way you get a feel for the project and can use the "good" stuff later on. It's also a good way to tell how much a given circuit benefits from boutique parts. I also always buy a few spares of every part when I start a project in case I toast a few during the building process.
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