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Whats the differnce in outputs?

FreshMaker

FreshMaker

Member
FYI this is a nub post.
I was wondering if someone could explain the difference between Speaker outputs from a reciever and Pre-out's?
I know what they each look like and what they go to, I am more intrested in how a reciever handles them. Are they identical? Is one amplified more than the other?
 
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The speaker outputs are amplified more - in terms of gain, probably 25-30 dB more. Preamp outputs are designed to drive an amplifier, not speakers, with the amplifier providing additional gain to provide a signal suitable for driving speakers.

Oh, and welcome to AK!
 
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Ok, don't get mad at me for asking this then :P

I have a Mac 1700 And a Mc2205. For sake of conversation say i am not willing to part with either of them for sentimental value. The Mac 1700 doesn't have pre-outs. Would I hurt the Mc2105 if I ran it with the 1700? According to specs the Mc2105 has "Level control provided for higher input voltages."
 
I'm not a Mac guy but the 1700 is a receiver and the 2205 is a power amp correct? If the 1700 can be split between the pre and power amp then you sure can run RCA cables from the pre out to your 2205. Whether it's better than your present pre-amp is up to you to decide.
 
I have a surround system, but I would love to have a Mc system for only listening to music through 2 channels.
My main concern is that I will do damage to the Mc2205 by running it with the 1700. That would mean running from the speaker outputs from the 1700 to the RCA inputs of the Mc2205.
 
FreshMaker said:
I have a surround system, but I would love to have a Mc system for only listening to music through 2 channels.
My main concern is that I will do damage to the Mc2205 by running it with the 1700. That would mean running from the speaker outputs from the 1700 to the RCA inputs of the Mc2205.
Click to expand...
There is a VERY high likelyhood of damaging your 2205 by trying to run it with the speaker outputs of a receiver. Most car stereo shops sell level matching devices pretty cheap, those would get you by until you could get a decent pre-amp.
 
If the 1700 doesn't have pre-outs, then the two units are incompatible.

That's the bad news. The good news is you might be able to make them compatible, if the line level output jacks are NOT soldered directly to a circuit board. If you can get to the jacks easily, you can convert a tape out jack to a pre-out jack.

It's just a matter of picking up the audio signal after a blocking cap and routing to the jack.

Good luck!

Jerry
 
onplane, that sounds like an option I would like to look into. I am perfectly comfortable soldering, but where would I find these line level output jacks? I am surounded by electrical and computer engineers here at college so I could track down the pins if you give me some directions.
 
onplane said:
If the 1700 doesn't have pre-outs, then the two units are incompatible.

That's the bad news. The good news is you might be able to make them compatible, if the line level output jacks are NOT soldered directly to a circuit board. If you can get to the jacks easily, you can convert a tape out jack to a pre-out jack.

It's just a matter of picking up the audio signal after a blocking cap and routing to the jack.

Good luck!

Jerry
Click to expand...
Sometimes the pre-amp in a receiver doesn't have enough oomph to drive an external power amplifier, and you may need to graft an op-amp in there somewhere. Most pro amplifiers require about 1.23v input to drive them to full power, I don't know how much it takes to drive a 2205, though.
I mention this because I had a Harman/Kardon receiver that I used to run a power amp, and the tech I used (before I became a tech myself) had to build an op-amp circuit into the receiver to bring the level up high enough to drive an amplifier.
 
Tarior, how can I track down the pre-amp circut in my reciever? Will I be able to use a multimeter to check the voltage?
 
A schematic would be extremely helpful, likely still available from McIntosh. You will need an audio signal generator and an oscilloscope.
 
To bad there isn't an online source for those schematics huh? We do have both those pieces of equipment in the labs at school, so I guess I need to contact Mac for a Schematic.
 
I have ordered several service manuals from Mc and they have been quite reasonable. McIntosh still offer great customer service.
 
Freshmaker,

I would NOT get too complex here. You have more than a good chance that the pre-amp in the Mc2205 is putting out plenty of voltage.

The real problem is can you get access to the output jacks on the back of the receiver? Take the cover off and look at the jack for tape out on the INSIDE of the receiver. If it's soldered directly to a circuit board, now you have a problem.

If wires are soldered to the jacks, then it's easy to cut those wires and replace with wires picking up a signal in the power amp right after the initial blocking cap on the power amp board. Your new wires must be shielded, because the signal level is low.

Good luck!

Jerry
 
This whole project is not for a beginner...

If the 1700 does not give you access to the output of the preamp to allow routing to another amp (such as the 2205), then sometimes it is feasible to modify the unit and add 'pre-out/main-in' jacks, but this requires a good working knowledge of electronics, AND some room on the rear panel to add four RCA jacks. I can't see hacking into a 1700 to do this, and IIRC the 1700 doesn't have much room on the rear panel. Plus, units that have no 'pre-out/main-in' jacks tend not to have the drive level capable of pushing an external amplifier, being designed simply to drive the internal amp (I do not know if this is the case with the 1700). The output can be boosted with a high-quality opamp, but this is a project that is best left to a pro, and you have to consider that you're hacking on a classic unit.

As was suggested, you can use the tape output to feed to the 2205, but you lose volume control and tone control at the 1700 and would have to use the 2205 level controls to adjust listening level.
 
Thanks for the warning echowars. I am a beginner as far as amplifiers go, but I will know when I don't want to go any further. Pretty much when if the project requires me modifing the 1700 to the point of no return I wont do it. If the mod is jumping wires from a pre-amp to tape out that seems reversable to me.

onplane, the solder connections are very easy to reach. Looks like they use the body as a ground so its 2 solder points on the back of the tape out jacks.

Can anyone confirm the lose of volume control if I do the mod?
 
ANYTHING exiting the tape-out jacks bypasses all the preamp functions, except the phono amp, any dubbing controls, and the source selector.

I really don't understand what onplane is wanting you to do. If you want to use the tape out, use the RCA jack on the back panel. If the unit has no pre-out/main-in, then there's no connection for such at the back panel or anywhere else that I'm aware of...
 
If I follow onplane, I would be de-soldering the existing tape-out connection. Then, I would track down the Line level wires before they hit the power amp and jump those to the tape out jacks.
Sounds like a great idea to me since I have zero use for the tape out as it is currently.
 
FreshMaker,

That is exactly what we are doing. Now, you need to locate on the power amp board the signal coming in and most of the time, the very first component will be a blocking cap. You pick up the signal immediately after that cap.

The center of the shielded cable gets soldered to the PC board there. Then you need to find a ground for the shielding (same as they do on the other end at the jacks).

You will NOT lose the volume control function with this mod; nor will you lose the tone controls and all of the other controls in the receiver's pre-amp.

Some folks mentioned that you may NOT get enough voltage out of the receiver, and there is a simple way to determine whether this is a concern. Vast majority of pre-amps are very close to unity gain (with the trivial exception of the phono stage). Now they do plenty of shaping and can boost frequencies, but average is still close to unity.

So, you feed the tape out as it currently exists to the power amp and see whether you have sufficient signal to drive your speakers. Now be careful, because the tape out will be close to full volume and your volume control has zero impact on the tape out signal. If you get plenty of volume, then you can be fairly certain that once you implement the mod the pre-amp won't drop the signal so much that you'll lose significant volume.

Regards,
Jerry
 
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