Hey diyaudio!
So im getting a pair of DT990 250ohm in the mail in a week or so and i want to have a basic amp until i can afford to get something like an o2 amp. My plan is to build a cmoy amp based of the How to Build the CMoy Pocket Amplifier build. Iäm planing on powering it with 18v dc right from the wall because i already have a pair of SE215 i love to use while on the move. Since it will be stationary i see no reason to use batteries. But with this panic planing (have to order parts in 2 days) i'm struggeling to figure out how will the Tangenstsoft version look like i want it. Or is there a newer better version of the cmoy that you can recommend to power my new Beyh cans?
So the first problem is that i do not know what potentiometer i should get,
i'm thinking this will work? am i wrong?
https://goo.gl/rLZXK3
Also im wondering if Parasonic FC capacitators will do the job?
Next problem is with how to wire the power switch. Do i just connect the wires from the dc power plug to + and - on the switch, and then connect the power to the circuit from power switch to the circuit. If not, how do i do it?
Third problem, or well its more of a question. I will need an op-amp and i'm having a hard time deciding what to go with. Right now im thinking the OP275GPZ will be the best way to go, opinions? I do like bass, but i do not want it to be overpowering.
Lastly, How would one make a container for it all. I know its usually contained in a mint box, but since im not going for a protable amp. Do you guys have any recomendations what i can make my self to contain it?
So im getting a pair of DT990 250ohm in the mail in a week or so and i want to have a basic amp until i can afford to get something like an o2 amp. My plan is to build a cmoy amp based of the How to Build the CMoy Pocket Amplifier build. Iäm planing on powering it with 18v dc right from the wall because i already have a pair of SE215 i love to use while on the move. Since it will be stationary i see no reason to use batteries. But with this panic planing (have to order parts in 2 days) i'm struggeling to figure out how will the Tangenstsoft version look like i want it. Or is there a newer better version of the cmoy that you can recommend to power my new Beyh cans?
So the first problem is that i do not know what potentiometer i should get,
i'm thinking this will work? am i wrong?
https://goo.gl/rLZXK3
Also im wondering if Parasonic FC capacitators will do the job?
Next problem is with how to wire the power switch. Do i just connect the wires from the dc power plug to + and - on the switch, and then connect the power to the circuit from power switch to the circuit. If not, how do i do it?
Third problem, or well its more of a question. I will need an op-amp and i'm having a hard time deciding what to go with. Right now im thinking the OP275GPZ will be the best way to go, opinions? I do like bass, but i do not want it to be overpowering.
Lastly, How would one make a container for it all. I know its usually contained in a mint box, but since im not going for a protable amp. Do you guys have any recomendations what i can make my self to contain it?
The volume control in your link takes me to a single gang control. You need a dual gang for stereo which looks like a double version of the one in your picture.
The CMOY appears in different versions with regard to the power supply. If you are building a 'virtual ground' type which uses a single supply (such as a single battery or a single DC mains powered supply) then yes, the switch simply connects in series with the positive lead of the power supply. If it is a true dual supply (split rail generating true minus and positive voltages) then you need a double pole switch to control both positive and negative rails.
The opamp used has no bearing on the amount of bass produced. All opamps have a response down to DC.
The case is up to you
It would be best if you could post the diagrams of what you are building and then we can advise on the power supply better.
The CMOY appears in different versions with regard to the power supply. If you are building a 'virtual ground' type which uses a single supply (such as a single battery or a single DC mains powered supply) then yes, the switch simply connects in series with the positive lead of the power supply. If it is a true dual supply (split rail generating true minus and positive voltages) then you need a double pole switch to control both positive and negative rails.
The opamp used has no bearing on the amount of bass produced. All opamps have a response down to DC.
The case is up to you
It would be best if you could post the diagrams of what you are building and then we can advise on the power supply better.
The volume control in your link takes me to a single gang control. You need a dual gang for stereo which looks like a double version of the one in your picture.
The CMOY appears in different versions with regard to the power supply. If you are building a 'virtual ground' type which uses a single supply (such as a single battery or a single DC mains powered supply) then yes, the switch simply connects in series with the positive lead of the power supply. If it is a true dual supply (split rail generating true minus and positive voltages) then you need a double pole switch to control both positive and negative rails.
The opamp used has no bearing on the amount of bass produced. All opamps have a response down to DC.
The case is up to you
It would be best if you could post the diagrams of what you are building and then we can advise on the power supply better.
This is the schematic; http://tangentsoft.net/audio/cmoy/misc/cmoy-tangent-sch.pdf (it's with batteries instead of wall power)
and here is the parts; Part Lists and Suggestions
Is this still up to date, or do you recommend something els?
Its an up to date circuit.
Do you understand the implications of the power circuit as it is drawn ? This is very important.
If you replace the two 9 volt batteries with a single mains powered 18 volt supply then the circuit will in isolation function correctly. If the mains power supply happens to have the '0' or zero volt wire of its output internally connected to mains ground via a three core mains lead then you have a problem. The problem is that you could create a short circuit if you then used the CMOY with any other mains grounded equipment (CD player etc).
In other words the part marked -9 on the diagram would be connected to mains earth. The CMOY ground for audio is the virtual ground formed by the two 4.7k resistors. Use it with a grounded CD player for example and you have just shorted the point currently marked -9 to the virtual ground via the interconnecting leads.
The CMOY is what it is... a basic text book implementation of an opamp that has gained cult status. That said, it is easy to build and to get to work.
The dual gang pot you show is correct.
Do you understand the implications of the power circuit as it is drawn ? This is very important.
If you replace the two 9 volt batteries with a single mains powered 18 volt supply then the circuit will in isolation function correctly. If the mains power supply happens to have the '0' or zero volt wire of its output internally connected to mains ground via a three core mains lead then you have a problem. The problem is that you could create a short circuit if you then used the CMOY with any other mains grounded equipment (CD player etc).
In other words the part marked -9 on the diagram would be connected to mains earth. The CMOY ground for audio is the virtual ground formed by the two 4.7k resistors. Use it with a grounded CD player for example and you have just shorted the point currently marked -9 to the virtual ground via the interconnecting leads.
The CMOY is what it is... a basic text book implementation of an opamp that has gained cult status. That said, it is easy to build and to get to work.
The dual gang pot you show is correct.
You're welcome
(if you are not sure on anything then just ask)
Hello again!
So i'm planing to use a 3,5mm as input and a 6.35mm as output. But i'm not sure what kind of jacks to get? a 2 or 3 pool one?
6.35mm is a standard full sized headphone socket like this,
REAN - NYS216 - Phone Audio Connector, Socket, 6.35 mm, 3, Chassis Mount, Plastic Body, Tin Plated Contacts | CPC UK
3.5mm as input would be something like this,
PRO SIGNAL - PSG08282 - Phone Audio Connector, Socket, 3.5 mm, 3, Chassis Mount, Plastic Body | CPC UK
(Three pin types are stereo, two pin are mono)
REAN - NYS216 - Phone Audio Connector, Socket, 6.35 mm, 3, Chassis Mount, Plastic Body, Tin Plated Contacts | CPC UK
3.5mm as input would be something like this,
PRO SIGNAL - PSG08282 - Phone Audio Connector, Socket, 3.5 mm, 3, Chassis Mount, Plastic Body | CPC UK
(Three pin types are stereo, two pin are mono)
Thanks! Everything is ordered and i start the build next thursday!
Just a quick question, Will i have to add a headsink the the IC since i will be using 2 9v's to power it? Also for how long can i power the amp with 2 9v?
Its not normal practice to heatsink small 8 pin opamps. How long on two 9 volt batteries... hmmm lets see...
A 9v alkaline battery has a capacity of around 550mAh and so if you use an opamp drawing 1ma quiescent then it would run for 550 hours (that's with no audio). I would bet you would be over 100 hours with sensitive headphones. The resistors of the virtual ground (were they both 4.7k ?) add to the current draw. In fact they draw almost 2 milliamps... careful choice of an opamp could see you reduce that 1000 fold as you could use much higher values.
If you use two batteries then you can make a true split -/+ 9 volt supply and so do away with the virtual ground. You would need a double pole switch though, to break both supplies.
A 9v alkaline battery has a capacity of around 550mAh and so if you use an opamp drawing 1ma quiescent then it would run for 550 hours (that's with no audio). I would bet you would be over 100 hours with sensitive headphones. The resistors of the virtual ground (were they both 4.7k ?) add to the current draw. In fact they draw almost 2 milliamps... careful choice of an opamp could see you reduce that 1000 fold as you could use much higher values.
If you use two batteries then you can make a true split -/+ 9 volt supply and so do away with the virtual ground. You would need a double pole switch though, to break both supplies.
Well, so i'm back to wall power because now im building 3 cmoy amps (1 with 1 9v, mine with either 2 9v or dc power and one with dc only)
So im wondering if im looking for something special in the powersupply part? or will this Ställbar nätadapter 9-24 V (DC) 24 W > Ställbar utspänning | Kjell.com will work fine? Also i'm assuming any kind of dc jack will work, as long as + and - is wired correctly(and has the right connector)?
Well, just now i got the parts needed for the builds (finaly 3 weeks wait), but the company i ordered from messed up a bit and got me 10k resistors instead of 1k. As i understand this will get me a gain of 2 instead of 11. Will this be a problem since i have 250ohm headphones? or am i good to go and start building now?
I'm just having to look back... a zillion posts have been and gone since this OK, so you mean you are using a 1k in place of R4 which is shown as 10k. If so then yes, you have a voltage gain of 2. You will only know by trying I'm afraid as to whether it will give enough gain. If you have a lot of 1ks then you could use two in series to make 2k (so that's a start) and also parallel R3 with another 1k so making 500 ohms).
That gets you halfway there. Try it and see how it works out first. And its only a minutes job to swap a resistor out to the correct one anyway at a later date.
OK, so you mean you are using a 1k in place of R4 which is shown as 10k. If so then yes, you have a voltage gain of 2. You will only know by trying I'm afraid as to whether it will give enough gain. If you have a lot of 1ks then you could use two in series to make 2k (so that's a start) and also parallel R3 with another 1k so making 500 ohms).
That gets you halfway there. Try it and see how it works out first. And its only a minutes job to swap a resistor out to the correct one anyway at a later date.
Ill be sure to try that. But while i was looking around for what gain to use last night. I found a review from NwAwGuy about some cmoy amp he tested, but there was a part that made me kinda scared to use my amp :/
- Headphones could be damaged if one battery becomes disconnected
- Headphones could be damaged if one battery dies before the other
How do i know when i'm running low, because i really don't want to damage my new headphones as i cant afford a new pair for several months.
This kind of problem can occur on any 'direct coupled' amplifier but as regards the CMOY, if you build it as in the PDF in post #3 then you should basically be OK. The headphones are essentially AC coupled via the 220uf caps and the only DC path available is via the 4.7k resistors. The 4.7k's would not allow enough current to pass to cause damage.
With the above design there is no imbalance due to different battery voltages.
All that would change if you constructed it as a true DC coupled dual rail design, but as drawn it isn't and so those problems wont occur.
With the above design there is no imbalance due to different battery voltages.
All that would change if you constructed it as a true DC coupled dual rail design, but as drawn it isn't and so those problems wont occur.
Well im following this; Strip Board CMOY Revisited
Its easier to follow, but as far as i understand it is still the same as the schematic i posted earlier
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