[Ikrit42]

It depends entirely on where in the circuit you hook up your led, and how you hook up the batteries (i.e. series vs. parallel).
If you follow Tangent's guide, it'll probably get the full 18 Volts.

 

[Joshatdot]

Well its basicly the same schmatic as Tangents with a TLE2426CLP railsplitter. Dual 9v batts in Series.

 

[Seaside]

Quote:

Originally Posted by Joshatdot /img/forum/go_quote.gif On LED's, I have on order a 3mm, Diffused Blue, 12.5mcd, 3.5v, 10mA. I am going to use it with my CMoy w/dual 9v batts. With the CMoy's resistor divider or TLE2426, the LED will get 9v only right? or the full 18v?

That will be full 18V.
Anything that does not reqire virtual ground, for ie. LED, should be connected to power source, not to virtual ground. Virtual ground will be shifted by the amount of power that part(LED) consumes, and which eventually makes virtual ground instable. One LED connected to virtual ground may be alright, but better not do that.

 

[fordgtlover]

You should be able to make your first one for about $25 in parts. I would recommend following Tangent's guide very closely for your first one and then get fancy after that.

 

[AudioCats]

get some super cheap yet ok sounding op amps such as 5532, use them as guinea pigs during circuit testing/trouble shooting stage. The chance of messing up is pretty low since the circuit is so simple, but nevertherless exist.

 

[balou]

does the NE5532 work in the simple cmoy without problems? I thought such older chips needed greater care, but I'd be glad if I'd be able to just use them in my cmoy.

oh, and do you know if the even cheaper RC4558 will also work?

 

[qpoiz]

My first amp I got as a half-built kit on ebay. you can also buy a pot, jacks, and LED in addition to the assembled board for around $25

After that I made my own from scratch. About $40-$50 in parts for two amps from Digikey

 

[Seaside]

Quote:

Originally Posted by balou /img/forum/go_quote.gif does the NE5532 work in the simple cmoy without problems? I thought such older chips needed greater care, but I'd be glad if I'd be able to just use them in my cmoy. oh, and do you know if the even cheaper RC4558 will also work?

You're right about some old chips. Not all of them, but some of them need little more voltage to compare with other OPs, and may need additional care to make them work with Cmoy.
But as for your question.... Dunno about RC4558, but if you mean "JRC4558" then, I would say "Yes". I happen to have bunch of JRC5532, 4556, 4558, 4680 at my drawer, and they all worked fine with my cmoy and A47 without problem... even though the sound is not as good as other OPs that cost 10x more.

 

[ericj]

Keep in mind that the ne5532 and jrc455x have fairly high offset currents, so you can't safely use the same resistor values as the default cmoy. You will have DC offset at the output unless the feedback loop resistors, when paralleled, have the same resistance as the ground reference resistor.

but as long as we're on the subject of cheapies, try the jrc2068 as well. which also needs carefully chosen resistors.

 

[balou]

I really mean the RC4558. It's an ancient chip, directly based on the 741 (seems to be just a dual version of it). Currently manufactured by TI, dunno if they were the original manufacturer. found it in a phono amp from the 80s, but I most likely fried it while desoldering. Also found a clone, Rohm BA4558 in a 80ies cdp. It's the cheapest dual opamp you can get from farnell.

Got the original date from the datasheet. First revision of it is from march 1976. Well, I order one or two and try if they work

edit: lol, just found a forum about guitar effect pedals. found a thread in which they discussed how they like the distortion of the original rc4558 (seems to be made by raytheon, the TI one is just a clone). Quite the reverse requirements as we have here

edit2: the jrc4558 seems to be a clone of the rc4558, or vice versa.
If I don't hear a difference between an ad843 and an rc4558, I'm giving up this whole amplifier thing. Then I will at least save some money. but I hope I'll hear something, because building amps is a nice hobby

 

[Seaside]

Quote:

Originally Posted by balou /img/forum/go_quote.gif I really mean the RC4558. It's an ancient chip, directly based on the 741 (seems to be just a dual version of it). Currently manufactured by TI, dunno if they were the original manufacturer. found it in a phono amp from the 80s, but I most likely fried it while desoldering. Also found a clone, Rohm BA4558 in a 80ies cdp. It's the cheapest dual opamp you can get from farnell. Got the original date from the datasheet. First revision of it is from march 1976. Well, I order one or two and try if they work edit: lol, just found a forum about guitar effect pedals. found a thread in which they discussed how they like the distortion of the original rc4558 (seems to be made by raytheon, the TI one is just a clone). Quite the reverse requirements as we have here edit2: the jrc4558 seems to be a clone of the rc4558, or vice versa. If I don't hear a difference between an ad843 and an rc4558, I'm giving up this whole amplifier thing. Then I will at least save some money. but I hope I'll hear something, because building amps is a nice hobby

I see.
I haven't had that ancient fossil RC4558, so I can not comment on that. But RC4558 can be used at Cmoy if it used at guitar amp, since simple guitar amp is quite similiar with cmoy. I am sure that you can hear differences b/w AD843 and "JRC"4558 as you already know every OPamp has its own sound signature. I am in no way to say that I have golden ears, but I can hear difference between some OPamps. I think you too can hear it.

And eric, I haven't checked DC of my cmoy. I stopped use it long time ago. But I do not have any problem at neither the amp nor my earphones with cmoy with cheap JRCs back then. Of cause, you knew I always set my gain about 3 or 4 at most amps I made.

 

[ericj]

Yeah, at a gain of 3 it won't make a huge impact.

My wall-powered a47 is currently at a gain of 15, though, which would be whole volts of dc with unbalanced resistors and a 4556 in the gain stage.

The other option is to build the PRR cmoy variant with output capacitors and a single-rail power supply.