CMoy headphone amp - will layout work + questions

[MrStab]

hi guys,

i need to build a boring non-guitarist a gift this weekend and after much searching (and ruling out a "stun gun" schematic ), i've decided to go for the CMoy headphone amp. i searched the forum and there are a few posts on this circuit already, despite it not being strictly guitar-related, so please don't castrate me for posting in the wrong section.

anyways, i pretty much just found out this thing even exists about 2 hours ago, then i had an internet outage, so please excuse any stupidity.
i used this schematic: http://tangentsoft.net/audio/cmoy-tutorial/misc/cmoy-tangent-sch.pdf , and here's my layout attempt:



so, questions!

• Will it work?
• My instinct is to go about this in a normal stompbox-kinda way, ie. battery negative & grounds all together, but i'm guessing this isn't the case? or is it?
• Just to confirm what i've read elsewhere, would this schematic work with just one battery?
• Should a TL072 suffice?

frankly, this will probably end up in a drawer somewhere never to be used again. and the person in question has probably lost most of their upper hearing range anyway. but it's the thought that counts. i have a coupla days to learn more about this circuit before the parts arrive.

cheers!

[aron]

All ground symbols go together. Note that battery negative is -9 and goes to the IC pin 4 (TL072). I would think the TL072 would work. I guess it would work with one battery with half the headroom.

[TOPLEL]

It would work with one battery but after that you would have only 4.5V per rail, you gotta check if your opamp would work at that low voltage.

TL072 sounded pretty bad in my CMoy, try something better like some Burr-Browns (i liked OPA2134, OPA2227) (these might not work with a single battery)

Use some better film caps for the input caps (polypropylene)

[Electric Warrior]

you're missing lots of trace cuts..

[MrStab]

It would work with one battery but after that you would have only 4.5V per rail, you gotta check if your opamp would work at that low voltage.

min supply voltage for TL072 is 5V, thanks for pointing that out! how could i change the power section to accomodate? just take all that crap out, apart from a cap/resistor or two?

you're missing lots of trace cuts..

do you mean under horizontal components? damnit! and/or somewhere else? i kinda just rushed it together and didn't think. would hopefully have noticed after a few weeks. lol

All ground symbols go together.

i know all grounds go together, but it just seemed in this schematic that there was a distinction being made between ground and battery negative, whereas i usually just wire both to the in or output jack when i'm making effects, am i just being paranoid and the do still go together? (i'm still a hopeless novice)

cheers for the help so far, guys

[davent]

I've auditioned a pile of different ic's in my cmoys any dual with the same pinout and the TL072 is no good, sounds like trash. If you don't want to spend much the NE5532 is inexpensive and sounds very good.

dave

[MrStab]

sorry, been busy the past coupla days. sucks that the TL072 isn't too great in this application, all i have available are those and 4558's at the moment. are either of those completely unusable or just a bit crap?

unsure whether to proceed with the intent of a future upgrade, or switch to a different project as i won't be able to score more parts for a week or 2. is hard to find stuff that non-musicians might enjoy when most of the parts i have lying around are for stompboxes etc! lol

[gritz]

sorry, been busy the past coupla days. sucks that the TL072 isn't too great in this application, all i have available are those and 4558's at the moment. are either of those completely unusable or just a bit crap?

unsure whether to proceed with the intent of a future upgrade, or switch to a different project as i won't be able to score more parts for a week or 2. is hard to find stuff that non-musicians might enjoy when most of the parts i have lying around are for stompboxes etc! lol

Yeah, the TL07x wasn't really designed for sinking a snotload of current into a low impedance source. Have a snoop through Google - there are designs around for headphone amps that use opamps with their outputs buffered by a couple of bipolar transistors. I've not built one, so I can't really comment further, but maybe someone here can recommend something.

[artifus]

from: http://mp3forkidz.com/mic/circuits.html

[MrStab]

cheers for the pointer, Jonathan - i'll have a look on google for stuff like that. no chance of just making a fully transistor-based one?

thanks for the schem, artifus - saved!
i'm gonna look for something that i can do with the parts i have in the meantime and just resort to a postponed headphone amp in a week or so when i have the time to get a better opamp.

(haven't abandoned the "sound-light" thread btw, considering a rebuild to double-confirm any schematic!)

[artifus]

you could also look at the headbanger circuit:



from: http://www.minidisc.org/headbanger.html

[davent]

Just up from the hole after playing around with one of my Cmoys and various opamps. Lineout of a Sony discman to Cmoy driving Grado SR80's. The usual chip i have in there is an OPA2132, also auditioned an NE5532 and an MC4558. If you have a 4558 sitting around by all means build the Cmoy, just don't tell anyone that's what you're using. Socket it so you can swap in a more expensive chip later but you may not see any reason to do that.

On a similar note i was visiting a friend's recently and noticed he's using a Grado RA-1 headphone amp in his extremely impressive hifi system. Didn't have the heart to tell him that his 10 year old son who's very into electronics could have soldered him up the circuit for very little cash outlay.

http://vintageking.com/grado-ra-1-hg-high-gain-headphone-amp

http://4.bp.blogspot.com/_ZVgJtItVgnk/RsBc8Bf9CWI/AAAAAAAAAEg/vO09ZBa6m00/s1600/Grado-RA1-Headphone-Amplifier-Schematic.png

I built my daughter a headphone amp as part of her system that uses a TL082 at it's heart but it also has 3904/3906 pair as well as a TIP29/30 pair on the output. That one sounds great and one day need to get around to building one for myself. Was published in an old AudioXpress article by Dennis Colin.

dave

[PRR]

> this schematic that there was a distinction being made between ground and battery negative

Correct. It's a bus/subway amp, one battery, NOT grounded at either end.

It will work with a dedicated 9V (to 18V) wall-wart. It will not work from the typical daisy-chain pedalboard supply if any other box on the same supply is connected to the amp.

TL07x is great for loads above 2K, functional for loads a bit below 1,000 ohms, but totally gobsmacked by the usual modern 32 ohm headphone. Like my Corgi pulling a plow. (Cmoy was designing for higher-Z phones which did not drive well from 3V Walkmans.)

5532 is a better bet, but still struggles. Artifus' teamwork plan is better, but a lot of pins.

The LM386 plan is really quite excellent, *if* you find good-sounding '386es. And it is very happy with a 4-pack of AA cells, for *much* better battery life/cost/economy than 9V batts. (Use four D-cells and you can stay in the woods for weeks.)

[MrStab]

i have exactly two 386's lying around. it's a sign. thanks for that, artifus, i think i'm gonna try out the Headbanger.

i'm thinking of using this layout. it's unverified but seems to check out.
http://www.diystompboxes.com/smfforum/index.php?topic=90990.msg777316#msg777316

i'll probably have to use two pots as i don't have a dual-gang one, but pointless, aesthetic complexity can only be a good thing. i'll let you guys know how it goes.

thanks for clearing up the battery/ground thing, Paul - could save me a lot of hassle someday, even if the Headbanger circuit seems to not follow that rule