[Russ Arcuri]

Hi, all. I have three Hansen boards and will (eventually) be building a CMOY amp. I know little about amplifier circuit design (as will become obvious when I actually get to my question), but I was hoping this project would be a learning experience for me.

Anyhow, I took apart my Onkyo Integra 606 CD player, because (as I've mentioned a million times before) I like the sound of its headphone jack so much. It sounds beautiful even with hard-to-drive cans like the HD580s blah blah blah...

Anyway, what I found when I opened it up is perplexing me. I traced wires from the headphone jack and volume pot back to the circuit board, and found two opamps very close by (can't see the bottom of the board but logically these are what's driving the headphone output). Examining the board further, I found two other sets of opamps, where I expected to find only one other set. This CD player has one set of RCA outs, the headphone jack, and an optical output. What's the third set of opamps for?

The only thing that makes any sense to me is that the 606 (my model) is very similar to the 909 (the top model from the same timeframe). The 909 has two sets of analog outs -- one 'normal' unbalanced and one balanced set. Is it possible that they used the same circuit board for both? That would make one set of opamps on my circuit board redundant.

Just curious...

 

[Apheared]

Hmm, you'll have to do a bit more reverse engineering than that. It could be some are single amps, some are duals... they look the same unless you know. Might not even be related to the headphone circuit.

The easiest way to know is to contact Onkyo for a service manual, which will have a schematic with numbered parts list... saves a bucket of time. try support.onkyousa.com... if they're unhelpful then try Wizards Electronics or some place alike - they'll sell anyone a xerox'd version of any service manual from yesterdays to something 40 years old.

The harder way being to visually reverse engineer it. You're much better off if you can take the boards out and scan them on a flatbed at high resolution... you only handle them a little bit and can be back to listening while you take hours/days/years tracing out the board(s) on a graphic... you can draw signal flow and annotate too.

(I assume this is older? Integra now refers to a concortium between Onkyo and a bunch of other companies making AV gear? I dunno, check out www.integraresearch.com)

 

[tangent]

You can use dual inlined opamps per channel, one to amplify voltage and another to increase current. The Hansen boards do this, for example. Perhaps your Onkyo is doing this as well.

 

[Russ Arcuri]

Quote:

Originally posted by Apheared (I assume this is older? Integra now refers to a concortium between Onkyo and a bunch of other companies making AV gear? I dunno, check out www.integraresearch.com)

It's a 1993-era changer. At that time, Integra was to Onkyo what ES is to Sony. I'm not sure when it all changed.

I read the part numbers off the opamps. The two that I believe are part of the headphone amplification say on them:

45560
JRC
2206A

The other four look like this:

45600
JRC
2195D

As for obtaining a service manual... I took it apart simply out of idle curiosity. If I can obtain one cheap, that could solve the mystery. Otherwise, it's not all that incredibly important.

Thanks for your input...

 

[aos]

Datasheets should be here:

http://www.njr.co.jp/_efr005sem.htm

I found only 2206, and it's not an opamp, but FM radio stuff:

http://www.njr.co.jp/pdf/be/be04005.pdf

 

[Russ Arcuri]

Quote:

Originally posted by aos Datasheets should be here: http://www.njr.co.jp/_efr005sem.htm I found only 2206, and it's not an opamp, but FM radio stuff

That's not what I have; mine's definitely an opamp. It's an 8 pin device, unlike the part in the link you provided, and it's in a CD player -- a pretty unusual one if it contains FM radio parts.

It's entirely possible that these opamps aren't part of the current catalog. The CD player is 8 years old; the design could be a decade old.

I tried doing a search for the JRC 45560, and the only thing even remotely similar was a reference I found to the Grado RA-1 amplifier, which (apparently) uses an opamp called the JRC 4556.

Does anyone with more DIY knowledge than me know whether these opamps are still available, and whether they'll operate at a low enough voltage to be used in a battery-driven portable amp built on a Hansen board?

 

[aos]

Your chips are JRC (Japan Radio Co), and that's all I could find
on their web page.

I was doing lookup on the lower set of numbers but I should've looked up the top numbers. Your last "0" is most likely a "D", check it again. D stands for DIP I think. Both 4560D and 4556D
are dual opamps and can be found on the web page (4556 is now obsolete and replaced by 4556A).

 

[Russ Arcuri]

Actually, I couldn't decide originally whether that was a "D" or "0." It's likely that it is a "D" after all. Thanks for clearing that up.

However, the mystery now deepens, unless I just don't understand what a "dual" opamp is. Doesn't that imply that one opamp handles two channels? and if that's the case, then the DX-C 606, with one analog output and one headphone output, has enough opamps to handle (theoretically) six sets of outputs.

I guess I really do need a service manual. Tangent's suggestion that the opamps are being used in series to amplify voltage and current separately makes some sense, but then he goes on to say that the Hansen boards are like this.

I'm pretty sure the Hansen boards, which are the CMOY design, require only two opamps -- one per channel. Right?

 

[paulb]

Sometimes two opamps, or both channels of a dual opamp, are connected together to get more current. Look at Apheared's #47:
http://headwize.com/projects/apheared_prj.htm

 

[aos]

Dual opamp means it has two opamps in one package. You can find datasheets for both those chips following the JRC link I posted (chips are NJM4560D and NJM4556D). That will give you information you need to search for substitutions.

 

[tangent]

Russ,

The Hansen board has two opamp chips, but each chip has two opamp circuits inside. So, there are four opamps in that circuit, two per channel. The 8-pin DIP package can support either one or two channels; there are 4-opamp devices in DIP-14 packaging.