300DC Question: AC or DC Coupling and Why?
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jstang
Honey,I can't hear you...
The switch shorts the input coupling cap.
Its the only cap in the forward signal path... 10uf / 16v on the 300dc.
If you used a really good film cap and bumped the value up a little...and threw a .1uf film in parallel...
I doubt you would ever hear it....but you would still have the coupling protection.
But I don't own one...so I will put a zipper on it.....
Its the only cap in the forward signal path... 10uf / 16v on the 300dc.
If you used a really good film cap and bumped the value up a little...and threw a .1uf film in parallel...
I doubt you would ever hear it....but you would still have the coupling protection.
But I don't own one...so I will put a zipper on it.....
thefragger
Certified Crazy.
Great to know for when I'm restore mine!
SoCal Sam
Lunatic Member
To sum, AC is better for protection and DC gives slightly better sound??
Just ran into this. Been running Kenwood L-07M's for the summer and every time I ran the clothes dryer they would pop in and out of protection. They are DC coupled with no switch and no coupling cap. The coupling caps on my tube pre-amp are 10uF and it was enough to pass the low fluctuation when the drier heater turn on it and off changing the DC off set. I made up a set of cables with a built in 1uF film cap and no more problems. Best to run Marantz's in AC.
BeerLegs
Super Member
I have a 170 DC amp, 3250B pre, and a 2110 tuner. From my owners manual:
DC Coupling & AC Coupling Switch
This switch is provided to protect Model 170DC from large output popping noise due to erroneous connection of expensive speakers, troubles of preamplifier or using a preamplifier not designed for DC amplifier.
Therefore, whenever there are possibilities of the above cases, please set this switch to the AC COUPLING position.
Since I have the matching pre amp, I have it set at the DC position like slomar and have had no problem. I think slomar and I have it right. If your pre amp is not designed for a DC amplifier, you may want to leave it on the AC position.
....but I could be wrong...
DC Coupling & AC Coupling Switch
This switch is provided to protect Model 170DC from large output popping noise due to erroneous connection of expensive speakers, troubles of preamplifier or using a preamplifier not designed for DC amplifier.
Therefore, whenever there are possibilities of the above cases, please set this switch to the AC COUPLING position.
Since I have the matching pre amp, I have it set at the DC position like slomar and have had no problem. I think slomar and I have it right. If your pre amp is not designed for a DC amplifier, you may want to leave it on the AC position.
....but I could be wrong...
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SoCal Sam
Lunatic Member
Is it possible for a misbehaving input to deliver excessive voltage to the amp which the amp in DC mode amplifies and delivers to the speakers?
BeerLegs
Super Member
I believe so, but I haven't had a problem with my 170 DC. To play it safe, play it in AC mode. I do leave the 15 Hz filter on.
My SR 6010 DC on the other hand developed a problem about 15 years ago where it would pop loudly and erratically until it would warm up. I left the 20 Hz filter on and it never blew a speaker. I think it would of if I hadn't done that. I ended up getting it repaired and it hasn't done it since. There is no AC-DC Coupling switch on it like the 170 DC.
My SR 6010 DC on the other hand developed a problem about 15 years ago where it would pop loudly and erratically until it would warm up. I left the 20 Hz filter on and it never blew a speaker. I think it would of if I hadn't done that. I ended up getting it repaired and it hasn't done it since. There is no AC-DC Coupling switch on it like the 170 DC.
jblmar
JBL & marantz
Actually, if you have a DC preamp, (ie 3650) set the 300DC/170DC to Ac position.
anatech
Audio service specialist
Leave it in the AC position. When I rebuilt my 300DC, I replaced the electrolytic caps with film types. There is no difference in sound between either position now.
The rebuild vastly improved the sound of my 300DC. It is easily my best amplifier and you can really hear the differences between pre-amps. The best are the 3650s or SC-9s (both Marantz). It's even better than the new Cyrus Mono X amplifiers out of the box. They are next on my bench <evil laugh>.
Hi jstang,
I love your 500! The last one I rebuilt easily bettered most new products (maybe all). The Nakamichi rep at the time borrowed it for a couple weeks and didn't want to bring it back, the PA-7II was current at the time.
I wish I owned one and I do know where there were two disassembled. The guy wants the world for them in that state. You have something very special there, don't sell it.
-Chris
The rebuild vastly improved the sound of my 300DC. It is easily my best amplifier and you can really hear the differences between pre-amps. The best are the 3650s or SC-9s (both Marantz). It's even better than the new Cyrus Mono X amplifiers out of the box. They are next on my bench <evil laugh>.
Hi jstang,
I love your 500! The last one I rebuilt easily bettered most new products (maybe all). The Nakamichi rep at the time borrowed it for a couple weeks and didn't want to bring it back, the PA-7II was current at the time.
I wish I owned one and I do know where there were two disassembled. The guy wants the world for them in that state. You have something very special there, don't sell it.
-Chris
The original coupling cap was a crappy standard cap. Consider switching to a better audio grade level cap. I tried film and electrolytics (non polar). I found the film to be fuller and richer in sound. But they are significantly larger. So fitting it in there may be an issue?
I also vote for the AC for protection. When that surge comes you don't want your amp doubling as the circuit breaker!
charles
I also vote for the AC for protection. When that surge comes you don't want your amp doubling as the circuit breaker!
charles
anatech
Audio service specialist
Hi Charles,
Well, the original is not
Those orange capacitors are better than standard, you may see an epoxy seal that prevents the electrolyte from escaping. Those are really good caps,and they paid extra for them.
Sorry for picking on your comment, but my point is really one aimed at the entire audio community. In truth, and good quality capacitor is great for audio. Doesn't matter the brand name (sorry), just the quality. The amount of money spent on signal handling for industry is well i excess of what the audio market demands. Their requirements are often tighter than a stereo needs, so the requirements of industry drives the availability of parts for us here. If it weren't for test and measurement, or process control, the cool parts we like would not exist at all. We just use the better (you hope!) of the parts available to the world. I'm sure there are "modders" that will get all bitter and twisted over that comment, but it is the truth.
Anyway, the ones I yanked were orange with epoxy covering the terminal entrances. They tested fine as electrolytics, but the film types have better characteristics for that location in the circuit.
Matching some transistors has a far greater effect than picking magic parts will.
-Chris
Well, the original is not
at all. In fact, Marantz used capacitors that withstood the passage of time pretty well.
Those orange capacitors are better than standard, you may see an epoxy seal that prevents the electrolyte from escaping. Those are really good caps,and they paid extra for them.
Sorry for picking on your comment, but my point is really one aimed at the entire audio community. In truth, and good quality capacitor is great for audio. Doesn't matter the brand name (sorry), just the quality. The amount of money spent on signal handling for industry is well i excess of what the audio market demands. Their requirements are often tighter than a stereo needs, so the requirements of industry drives the availability of parts for us here. If it weren't for test and measurement, or process control, the cool parts we like would not exist at all. We just use the better (you hope!) of the parts available to the world. I'm sure there are "modders" that will get all bitter and twisted over that comment, but it is the truth.
Anyway, the ones I yanked were orange with epoxy covering the terminal entrances. They tested fine as electrolytics, but the film types have better characteristics for that location in the circuit.
Matching some transistors has a far greater effect than picking magic parts will.
-Chris
Be careful replacing film caps where electrolytics "were". I've been down that road a few times. And found that yes, a quality polar cap can, and usually does, sound better. The circuits were what might be called forward biased by the electrolytic. And in the upper level gear it was "voiced" with that type of cap.
What the engineers wanted and what the accounts ordered usually were two different capacitors. So in the end it was a matter of economics and not the love of audio that ruled. Marantz did try to use the better cap in a key position. But you have to remember it was price point engineering.
Electrolytic caps - good, bad, or what ever, after ten years or so they do degrade in function. They may test fine, eg high resistance and proper uf value, but they are like an old dried out battery.
In my 170dc that coupling cap I was talking about. It was a pretty crappy cheap cap. I don't know what they put in the 300's. Perhaps a better one????
Anyway - nothing makes a bigger difference than the right part. Not the most expensive.
charles
What the engineers wanted and what the accounts ordered usually were two different capacitors. So in the end it was a matter of economics and not the love of audio that ruled. Marantz did try to use the better cap in a key position. But you have to remember it was price point engineering.
Electrolytic caps - good, bad, or what ever, after ten years or so they do degrade in function. They may test fine, eg high resistance and proper uf value, but they are like an old dried out battery.
In my 170dc that coupling cap I was talking about. It was a pretty crappy cheap cap. I don't know what they put in the 300's. Perhaps a better one????
Anyway - nothing makes a bigger difference than the right part. Not the most expensive.
charles
anatech
Audio service specialist
Hi Charles,
The last 170DC I worked on used the same part as was in my 300DC. I can't say what was in yours as a running production change is certainly possible.
Now, what you say about capacitor types is very true in speaker crossovers. However, people who "voice" amplifiers will be playing with various types of film caps. It's a fact that after a "designer" comments on how bad an electrolytic may be, they will not be caught dead using them in a signal path.
You are correct that all production is cost vs performance based. It depends greatly on the price point and historical performance as much as $$. Also recall that a Marantz was often $150 ~ $200 higher by list price than other brands like Pioneer and so forth. They did have a reputation to protect and were expected to have better sound quality. I used to sell them years ago.
As for how a capacitor tests, I use an HP 4263A to do this. I'm looking at losses and I check audio capacitors at 1 KHz and 10 KHz. Electrolytic capacitors do poorly at 10 KHz but good ones aren't that bad at 1 KHz. Look up the HP 4263A and the 1 meter kelvin test fixture. Let's just say that some of those older capacitors are better than some brand new ones. You have to know what type of new capacitor to install that is as good as the original. I do see some bad, depending on ambient temperature and current levels.
-Chris
The last 170DC I worked on used the same part as was in my 300DC. I can't say what was in yours as a running production change is certainly possible.
Now, what you say about capacitor types is very true in speaker crossovers. However, people who "voice" amplifiers will be playing with various types of film caps. It's a fact that after a "designer" comments on how bad an electrolytic may be, they will not be caught dead using them in a signal path.
You are correct that all production is cost vs performance based. It depends greatly on the price point and historical performance as much as $$. Also recall that a Marantz was often $150 ~ $200 higher by list price than other brands like Pioneer and so forth. They did have a reputation to protect and were expected to have better sound quality. I used to sell them years ago.
As for how a capacitor tests, I use an HP 4263A to do this. I'm looking at losses and I check audio capacitors at 1 KHz and 10 KHz. Electrolytic capacitors do poorly at 10 KHz but good ones aren't that bad at 1 KHz. Look up the HP 4263A and the 1 meter kelvin test fixture. Let's just say that some of those older capacitors are better than some brand new ones. You have to know what type of new capacitor to install that is as good as the original. I do see some bad, depending on ambient temperature and current levels.
We are in complete agreement there! Also, I should mention that I agree that many service grade "capacitor testers" do not properly test a capacitor, and that is what I think you were getting at. In general, it is safer to say that a 20 year old capacitor is bad on average if you consider all brands. I just happen to have found that in Marantz equipment, that isn't always a safe assumption. Yeah, I actually test them and put the originals back if they test better than the new ones. It would be easier to simpler replace them all.
-Chris
jstang
Honey,I can't hear you...
I have replaced the input coupling (electrolytics ) with films on several amps. Last of which was my 500. Tried several types of electolytics and films....the best sound was with a ERO MKII 10uf film...with a .1uf filmbypass.
Very noticeable improvement...
Even through films are not polarized, some makes have a Negative band marked on them... That side should be placed closest to the "Ground" potential. If not you can increase noise and negate the positive affects of the Film cap upgrade.
Pick and install your film caps wisely...
jk
Very noticeable improvement...
Even through films are not polarized, some makes have a Negative band marked on them... That side should be placed closest to the "Ground" potential. If not you can increase noise and negate the positive affects of the Film cap upgrade.
Pick and install your film caps wisely...
jk
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