I’ve had and repaired a few of these Anthems and usually easy to repair and usually it’s been the caps I highlighted or a small voltage TO-92. Not seen any film capacitors go bad, and any resistors were identifiable from high heat marks.
Replace the capacitors indicated in this order, Red (1st), then Yellow and then Blue.
No reason to change PSU caps, they are within 20% spec and working fine (not had any outside the 20% when pulled out of circuit)
BE VERY CAREFUL if you take the boards off, the ribbon cable linking input board to output board is easily damaged and is 11/12 wires, and if you don’t get one of the power wires right, it can cause serious damage and throw it into protection or worse.
IMO if you are pulling the board and taking the risk, replace all the electrolytic capacitors, and take the time to unsolder the ribbon cable or you will break a wire or 4, ask me how I know.
Replace the capacitors indicated in this order, Red (1st), then Yellow and then Blue.
No reason to change PSU caps, they are within 20% spec and working fine (not had any outside the 20% when pulled out of circuit)
BE VERY CAREFUL if you take the boards off, the ribbon cable linking input board to output board is easily damaged and is 11/12 wires, and if you don’t get one of the power wires right, it can cause serious damage and throw it into protection or worse.
IMO if you are pulling the board and taking the risk, replace all the electrolytic capacitors, and take the time to unsolder the ribbon cable or you will break a wire or 4, ask me how I know.
Attachments
Did those repairs extend the dynamic range? That is what I am trying to fix here.
Thank you!
-Geoff
Thank you!
-Geoff
Hard to say with certainty, but if it’s lacking I would guess it has an issue somewhere and I’d start with caps and checking bias and dc offset.
The one I got most recently was not working and since it was coming apart for repair replaced all the electrolytic caps and the input pair actives with set of matched ones and repaired the amp.
Personally I think it sounds really good now, compared to 4-5 other mid level amps I have, but I wouldn’t lie and say I’m an audiophile, more that fix amps I couldn’t otherwise afford and then sell when I have an itch to try something new. I rotate between Legacy, B&K, Golden Theater, Anthem and Wolverine (diy) and a M2x and SIT class-A clones by Nelson Pass. The Anthem holds its own IMO.
The one I got most recently was not working and since it was coming apart for repair replaced all the electrolytic caps and the input pair actives with set of matched ones and repaired the amp.
Personally I think it sounds really good now, compared to 4-5 other mid level amps I have, but I wouldn’t lie and say I’m an audiophile, more that fix amps I couldn’t otherwise afford and then sell when I have an itch to try something new. I rotate between Legacy, B&K, Golden Theater, Anthem and Wolverine (diy) and a M2x and SIT class-A clones by Nelson Pass. The Anthem holds its own IMO.
Is the “issue” I one channel or both? Have you done any testing with a scope and sine waves to see exactly what range is low?
I don't have a scope yet - it is on the list of things I need. The test is simply by listening. I ran the amp off the same signal and it was noticeably different sounding on the low end. The mid's and highs sounded similar to my Receiver. I ran the amp off the processor loop in the receiver, so it was getting the exact same signal. It sounded similar with a different preamp too.
-Geoff
-Geoff
This may be news to you but preamps do sound different even when nothing is broken. Tonally, dynamically, spatially. Some of the underlying causes for such perceived differences are understood, others not so much. Circuit topology, component types, PS parts may all have their influence.
The easiest thing to do is measure basic parameters like bandwidth, noise and distortion spectrum. If those correspond to the factory specs there isn't much you can do without completely redesigning the unit.
I agree with you 100% But with the same preamp and two different amps, one amp lost all the low bass. The MAC6700 has a processor loop on the back where the preamp output enters the amplifier. McIntosh supplies U-Shaped RCA Plugs for this. I unplugged it and ran RCA's to the anthem and the bass disappeared. It wasn't slight, my wife heard it too. I played "Hypnotized" by Ani DiFranco which has a great string bass line in the opening minute. It was very clear and audible.
Thank you.
-Geoff
It bothered me so much the first time I ran the comparison, that a couple days later I set it up again and triple checked everything. So yes, phase was one of the things I confirmed was correct.
Honestly, I posted this here hoping that it was something that someone else had experienced and solved. The fact that nobody has seen it makes me want to set it up and run the comparison a third time. Tearing out those input boards is going to be a royal pain. Not sure I really want to. Maybe I'll just get a better sub and call it a day...
-Geoff
Two ideas for testing to confirm your findings, if you're uncertain. I saw you don't have a scope, but you've got a computer and maybe a multimeter. You can check the relative levels of a 60hz sine with multimeter, and you can run frequency response sweeps from your amps' speaker output into your PC audio input, analyze with REW or other suitable program. Make sure the level is fairly low for the PC test (under 1v) to ensure you don't damage anything. Since you have a known good unit, absolute accuracy isn't important, you just need relative levels.
Edit: you'll need to level match at a higher frequency to make the results of the multimeter test useful. As long as the meter gives repeatable results at 1k or a little lower, you can level match with the meter, even if its response rolls off at HF.
Edit: you'll need to level match at a higher frequency to make the results of the multimeter test useful. As long as the meter gives repeatable results at 1k or a little lower, you can level match with the meter, even if its response rolls off at HF.
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I will tag on to dkfan9 and his suggestion above - normally you would use your scope and do a frequency sweep (or computer w REW as he mentions). If this "loss of bass" is that noticeable to your ears - a basic way of checking is to use a DMM to check AC voltage at different frequencies. the voltage will dramatically lower or disappear if there is an issue with the amplifier.
Get your DMM and a 1khz/100Hz/50Hz test tone (Youtube, or a phone app) then set your preamp output signal to a known value, say 0.500Vac measured with a 1KHz signal with your DMM. Then play the 100Hz and 50Hz test tones on your MAC6700 and the only thing you will change is move the DMM to your speaker outputs and document the AC voltage showing on your DMM. Be careful you make all changes with the amplifiers unplugged from AC
Power off and without changing the preamp volume (should still be at 0.500V) connect the Anthem and do the same tests - what is the voltage output at 1k and then at 100Hz and 50Hz and you will "see" if there is a significant voltage difference from your MAC6700. Then let us know and we can hopefully point you in a more specific location to check for an issue. Keep in mind there will be some voltage drop from 1KHz to 50Hz, but it should be consistent between the two amplifiers.
If you have trouble seeing difference, you can increase preamp output signal to 0.75Vac or even 1Vac - just be careful, you don't want to short any wires.
Get your DMM and a 1khz/100Hz/50Hz test tone (Youtube, or a phone app) then set your preamp output signal to a known value, say 0.500Vac measured with a 1KHz signal with your DMM. Then play the 100Hz and 50Hz test tones on your MAC6700 and the only thing you will change is move the DMM to your speaker outputs and document the AC voltage showing on your DMM. Be careful you make all changes with the amplifiers unplugged from AC
Power off and without changing the preamp volume (should still be at 0.500V) connect the Anthem and do the same tests - what is the voltage output at 1k and then at 100Hz and 50Hz and you will "see" if there is a significant voltage difference from your MAC6700. Then let us know and we can hopefully point you in a more specific location to check for an issue. Keep in mind there will be some voltage drop from 1KHz to 50Hz, but it should be consistent between the two amplifiers.
If you have trouble seeing difference, you can increase preamp output signal to 0.75Vac or even 1Vac - just be careful, you don't want to short any wires.