My MacSD Upgrade for the Colour Classic [and Stereo Mod]

[Fizzbinn]

You must have received your chip from EBAY by now. Does what you received look like the EBAY photo? And how well does it work?

In preparation for my Color Classic STEREO MOD video, I've been looking around for sources of those chips, for people who don't have a working yet gutted LC575 like I do (which acts as a donor machine). Aside from your EBAY find (which has rather expensive shipping), I've found these:

UT Source (expensive shipping if only buying the chips -- not worth it!)

1. TDA7052AN (used, $0.94EA + $26.99 shipping)
2. TDA7052A/N2 (used, $1.25EA + $26.99 shipping)
3. TDA7052A/N2,112 (used, $1.85EA + $26.99 shipping)

Aliexpress (probably fake, which means maybe not truly 1W?)

• TDA7052A (new? used? 10pcs = $4.76, which INCLUDES Aliexpress shipping to Japan!)

There are many other Aliexpress sellers of the same, but I linked that one because it was rated 4.8 stars and had 62 orders.

Yes, looks right as far as I can tell:

I actually don’t have the other parts yet, I didn’t have the values for the resistors needed. I think they are in this thread, just need to get a Mouser order together. …I do have two Color Classics, I might try to steal/barrow the components to test. Perhaps a project for the weekend.

 

[JDW]

I didn’t have the values for the resistors needed. I think they are in this thread, just need to get a Mouser order together.

I first mentioned the list of needed parts and the procedure in this post, but here's an update based on what I bought in my last Mouser order...

STEREO MOD Required Parts:

• IS1 = TDA7052A (will extract from my gutted LT575)
• CS3 = 1µF 50V radial capacitor (my pick: 50YXF1MEFC5X11) — same as CS4: D=5mm, L=11mm
• CS1 (my pick: Kemet C1206C104K5RAC7210) — same as CS2: L=3.18mm, W=1.6mm
• CS5 (my pick: 3300pF, C0G, 100V) — same as CS6: L=3.2mm, W=1.65mm
• RS1 (my pick: 5.1kΩ, 1/4W 1%) — same as RS4: L=3.2mm, W=1.6mm
• RS2 — Desolder RS7 and solder it to RS2 pads.
• SS1 = Speaker with Enclosure (pulled from a cheap/junked Quadra/ LC 630)

You have many great choices for CS1 (0.1uF), but the case size is important so as to fit the pads. I chose that 50V rated Kemet cap because of the DC Bias issue affected all ceramic caps except C0G, whereby the capacitance drops as applied voltage increases. Even at 12V across that particular Kemet cap though, it's capacitance only drops by 2%, which I deem acceptable.

Since we have just discussed possible sources for the TDA7052A chip, the hardest part of this mod would be sourcing the required speaker & enclosure. Kay Koba was the one who recommended I buy a dirt cheap Q630, which I was able to grab off Yahoo Auctions for a mere ¥3960, which included domestic shipping to me within Japan. That's where I got my speaker.

 

[Jagmn]

FYI: For the speaker, I've put together a STL of the speaker case and it seems you can find 70x30mm 8Ohm speakers from a few sources. The STL is linked to this 68kmla thread - and I can change its parameters reasonably easily if anyone needs/wants different variants.

Interestingly the speaker in my CC is 16Ohm but the 630 is 8Ohm. And the specs on the amplifier chip specify 8Ohm (mine does not have the -TA extension as mentioned in the datasheet). I've tried swapping it with an 8Ohm in original and printed cases and it sounds the same with what I've run through it.

 

[JDW]

FYI: For the speaker, I've put together a STL of the speaker case and it seems you can find 70x30mm 8Ohm speakers from a few sources. The STL is linked to this 68kmla thread - and I can change its parameters reasonably easily if anyone needs/wants different variants.

Interestingly the speaker in my CC is 16Ohm but the 630 is 8Ohm. And the specs on the amplifier chip specify 8Ohm (mine does not have the -TA extension as mentioned in the datasheet). I've tried swapping it with an 8Ohm in original and printed cases and it sounds the same with what I've run through it.

The existence of an STL for the speaker case is fantastic!

I can verify that on the speaker I extracted from the Q630, it is stamped with 16Ω on the outside of the plastic case. But when I removed the stock speaker from inside my Color Classic and examined it, I see no markings at all. (I have not tried to remove the speaker from its plastic housing.)

If indeed the stock CC speaker is 8Ω, there ought to be some noticeable difference in volume when the two speaks are used inside the Color Classic. @Kay K.M.Mods should know about that though, because he has done the mod. I've not had time to do it yet.

 

[Jagmn]

The existence of an STL for the speaker case is fantastic!

I can verify that on the speaker I extracted from the Q630, it is stamped with 16Ω on the outside of the plastic case. But when I removed the stock speaker from inside my Color Classic and examined it, I see no markings at all. (I have not tried to remove the speaker from its plastic housing.)

If indeed the stock CC speaker is 8Ω, there ought to be some noticeable difference in volume when the two speaks are used inside the Color Classic. @Kay K.M.Mods should know about that though, because he has done the mod. I've not had time to do it yet.

That's interesting that your Q630 had a speaker stamped with 16Ω - the one in my LC630 is stamped with 8Ω. You can get a rough measurement of the impedance with a multimeter set to resistance on these smaller speakers.

 

[JDW]

That's interesting that your Q630 had a speaker stamped with 16Ω - the one in my LC630 is stamped with 8Ω. You can get a rough measurement of the impedance with a multimeter set to resistance on these smaller speakers.

I just measured. They both measure roughly 16Ω.

 

[Kay K.M.Mods]

In addition to the TDA7052A, the LM3080N was also commonly used as a power amplifier of this generation. In the case of TDA7052A, it is hard to say that it is limited to 8Ω. There are 8Ω and 16Ω speakers, but it seems that they are selecting the right number of ohms according to the power output.

 

[JDW]

In addition to the TDA7052A, the LM3080N was also commonly used as a power amplifier of this generation. In the case of TDA7052A, it is hard to say that it is limited to 8Ω. There are 8Ω and 16Ω speakers, but it seems that they are selecting the right number of ohms according to the power output.

For the sake of clarity, it is important to note that the TDA7052A (click for data sheet) is a dedicated audio amplifier IC, whereas the LM3080N is a special kind of op-amp called an Operational Transconductance Amplifier, which is used as a voltage-controlled current source. So if indeed, the LM3080N was used in an audio amplifier circuit, there would need to be dedicated external circuitry required to make it work like that.

In other words, the LM3080N is absolutely NOT a drop-in, pin-compatible replacement for the TDA7052A used on the Analog Board of the Macintosh Color Classic.

---

@MacinJosh
I re-read your posts here & here. Did you re-solder, change wires or otherwise do anything to resolve the snapping and popping problem with your audio? Also, did you confirm with @Kay K.M.Mods if he can see this control panel in OS 7.6 or 8.1 with QT4 installed?

I myself cannot confirm anything because I am only now doing the prep work for my upcoming video on this mod.

 

[MacinJosh]

I re-read your posts here & here. Did you re-solder, change wires or otherwise do anything to resolve the snapping and popping problem with your audio? Also, did you confirm with @Kay K.M.Mods if he can see this control panel in OS 7.6 or 8.1 with QT4 installed?

View attachment 7882

I myself cannot confirm anything because I am only now doing the prep work for my upcoming video on this mod.

Yes, I managed to solve the snapping and popping issue. It wasn't the wire but something funky going on with the plastic housing (where and logic and analog board reside) and where it mounts to the front of the CC. It has some play in it and moving it while turned on resulted in the weird noises. I took everything apart, made sure all contacts were good and nothing was pinched and put everything back and haven't had any problems since.

Kay did reply and asked to make sure that the gestalt ID was set properly, which it was. Kay did the stereo mod some time ago and that Mystic is now a Takky. He currently doesn't have a Mystic with a stereo mod to check but he indicated that he does have the parts to do it.

Josh.

 

[JDW]

Folks, I'm in the middle of filming the STEREO MOD, and I want to mention a few things...

FIRST, I wish to thank @Jagmn once again because he posted a second speaker CASE design that doesn't have the tab on the back, which can be helpful when mounting two speakers inside the Color Classic.

SECOND, according to the apple-history website, the audio specs of 3 key Macs are as follows:

1. Color Classic Audio Out: 8-bit mono, Speaker: mono (single speaker inside)
2. Color Classic II Audio Out: 8-bit stereo, Speaker: mono (single speaker inside)
3. LC 575 (CC Mystic) Audio Out: 8-bit stereo, Speaker: mono (there are 2 speakers, so isn't this incorrect?)

There should only be 1 speaker inside the CC II as per Apple Service Source, which is just like the regular CC:



Perhaps @Kay K.M.Mods knows the answer to this, but I want to know if the LC 575 is sending true stereo to the dual onboard speakers.

What is true stereo anyway in this context? I know the LC575 has two TDA7052A amplifier chips for driving 2 speakers internally, so isn't that true stereo? And if it is true stereo, then the CC stereo mod would be giving you "true stereo" by way of two internal speakers, like like the LC575.

The external audio output (headphone jack) of the regular CC motherboard is only Mono, it seems. But doing the stereo mod on the analog board should yield true stereo, or am I misunderstanding how that works?

Maybe the answers to these questions can better explain what @MacinJosh described. I've not completed the mod yet, so I cannot test that.

 

[JDW]

Hmm... Not sure what's going on...

Sounds Control Panel indicates Stereo
View attachment 3198

But Monitors & Sound doesn't look like it is...
View attachment 3199

AppleCD Audio Player plays through all speakers even when selecting left or right. Am I missing something?

Anyway, as for the components, here are my findings:

CS1 is obviously a bypass cap, given its location. I still measured it to check my meter's accuracy; bang on 100nF
CS3 is an electrolytic 1µF 50v
CS5 is 3.2-3.3nF, not 3.3µF as has been stated in some guides.
RS1 is 5K1

I'm also getting slight popping sounds and interference now. Not sure I like this mod tbh...

I can confirm today that after doing the STEREO MOD on my own Color Classic and when booted into OS 8.1, the Monitors and Sound control panel looks exactly the same as yours, without the additional controls like Balance. :-(

What defines "stereo"? Is this dual Mono?

I must assume it is Stereo insofar as when I load Duke Nukem 3D and walk near the fire (with Flip Stereo enabled), I can hear the fire out of the left speaker as I put Duke's left ear to the fire side, and I hear the fire out of the right speaker when I move his right ear toward the crackling fire. So that tells me it is stereo of some sort. And yet, OS 8.1 does not recognize it, which is interesting because the LC575 motherboard has the PCB pads for that second Amplifier IC, as if it was designed to originally have that second chip for something. Even so, it's clear that OS support is lacking.

I also though the new speaker I added would not sound as loud as the stock speaker because I didn't drill any extra holes, but in fact, it sounds a tad louder. Could be the speaker. Could be the fact I added thicker wires than the stock speaker wires, or it could be that there's a huge gaping hole beneath my second speaker which isn't found under the stock speaker, thereby allowing more of the sound of the new speaker to get out.

I'm still working on my video. May take me another week.



Another interesting finding is that when I ran the Audio tests in Snooper 2, clicking on the Right Channel and doing the test causes it to speak into my Left Speaker (the one I added), and clicking the Left Channel makes it speak into the Right speaker (stock CC speaker). That explains why I needed to use Flip Stereo to make Duke Nukem' to sound right on both speakers. Hmmm...

I also connected my M6082 AppleDesign Powered Speakers to the headphone jack. Naturally, they sound superb, but when checking with Snooper 2, Left and Right were correct. That indicates the hardware is flipping the left & right channels on the internal speakers, but anything connected to the headphone jack is correct.

 

[JDW]

Well, folks, here's the finished Stereo Mod video which guides you through the entire process...

Special thanks to @Kay K.M.Mods, @MacinJosh, and "jagmn" (68kMLA) for their kind contributions and PM exchanges which helped shape the content.