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  • Are you sure you’re sure there’s nothing to an amp?

    2011 - 12.12

    Finding out you’ve been wrong about a long-held assumption is both a triumph and a defeat in the same breath. On one hand it’s awesome learning something and then moving forward with newly discovered truth; on the other hand, oh the wasted years!

    Maybe that’s a tad overdramatic for this particular instance, but I did learn an important lesson this week: amps matter! Being a loudspeaker-building hobbyist, I’ve long been of the opinion that if you’re getting a stereo, you should spend like 90% of your money on the speakers and then just get whatever crappy amp and CD player you find for the cheapest price possible, within reason. I mean, my living room stereo with my large main speakers have been powered by an Aiwa receiver for over a decade now, and it sounds extremely, extremely good. I spent somewhere around $1500 building those speakers and I power them with an amp that costed maybe $150, tops? And the resultant sound quality is, to my ears, better than any speaker system I’ve ever heard in any showroom, anywhere… with the exception of the DALI Helicon 800 which I heard at Decibel Audio in Chicago. Those were mind-blowing speakers. I forget how much those retailed for, but it was well over 5k. And hey, Danish Audiophile Loudspeaker Industries (DALI)? The danes know their speakers. If I have to lose out to someone, it’d be them, for sure. But I digress…

    For the last several months, I’ve had the speakers I built for my brother hooked up to an Onkyo TX-8210 reciever. I figured hey Onkyo is a Japanese brand, reputable name, should be a solid unit, fidelity-wise. When I finally got the speakers finished and started doing my critical listening, I was very happy with the treble, but disappointed in the bass. It sounded a bit bloated, boomy. Certain basslines would have notes that were noticably louder than the rest of the bassline. That should never happen. Some songs which happened to be rooted on those notes were almost unlistenable. I double checked my enclosure math, tried messing with the port length, added more stuffing inside the enclosure. Still boomy. I checked the driver response curves and scratched my head–these drivers both have very flat curves, with the exception of a slight dip at 2.5kHz (the crossover point). Man, did I mess up the enclosure somehow?? It should not be sounding like this. I kinda felt let down, like I was disappointed in my own skills. Maybe I’m not as good at this as I thought.

    Fast forward to last week, when I spotted this puppy on Craigslist for $80–a Marantz PM 750 DC integrated amp from circa 1982 with 80W per channel into 8Ω. Score!

    I’ve always really dug the looks of vintage Marantz gear, with that slightly-gold-tinged silver finish, and the fancy looking typography. It just looks quality, substantial, solidly built, you know? So I jumped at the chance to join the owners club for cheap. This baby was rescued from a junk pile, so it has a few scratches and dings, but so far it seems to be working as it should. All the LEDs light up and all knobs, sliders, and inputs seem functional. There is plenty of crackling when I hit the EQ switches, but hopefully some deoxit on its way in the mail will clear that up. I see on this guy’s page that none of those potentiometers are sealed against dust, so it figures that they’ll be crackly (update: DeoxIT worked wonders, even restoring the right channel which had gotten mighty cracklin). I may also follow his footsteps and swap out the caps in there too as they do wear out with age. This baby’s at least 25 years old. He also notes that maybe ’82 was a little past the golden years for Marantz, but stilllllllll:

    This unit has made a tremendous difference in the sound. As in, major, immediately noticable difference. All the boominess is gone and the treble seems even clearer yet. Those Scan-Speak tweeters sounded awesome before–they are spellbinding now. I’ve been kinda glued to this stereo in the evenings this last week, going back through my playlists, re-listening to favorite tracks, and evaluating the bass on ones that I remember were previously problematic. I’m sort of shocked by the fact that everything now sounds perfect. No more weird notes popping out in the basslines anymore. I had no idea an amp could cause weird EQ issues like that! For what it’s worth, I ran it with any EQ functionality on the Onkyo disabled, and anyway a bass EQ should not cause single-note resonances like that. So STRANGE!! I’m still kind of scratching my head, thinking WTF, that was the AMP causing this, that whole time?! And an Onkyo amp at that?

    So I’ve reached three conclusions:

    1. This Marantz unit rocks. It’s clear. Clean. Detailed. And all of those things at authoritive volume levels. Two nights this week as I laid down to go to sleep I noticed that my ears were ringing! That’s a definite indicator of a quality stereo: one that you keep turning up the volume because it just sounds so good!–until you’ve turned up the volume well beyond a reasonable level and you don’t even realize it because the sound quality remains solid. I definitely fell head first into that trap with the Marantz. Searching around the internet I see plenty of people scoffing at this amp saying that it’s not as good as Marantz’s older stuff.  That may be true, but it’s a giant step up from that Onkyo, and to my ears it sounds excellent.  I’m really impressed with the detail on Telefon Tel Aviv’s “TTV” from Fahrenheit Fair Enough (a reference listening electronic track, to be sure): I had the intro, filled with quiet sonic subtleties, cranked up VERY loud. Unreasonably loud. And when the beat drops, I had my hand resting on the volume control, expecting to need to turn it way down. I didn’t have to. Because:

    2. My bro’s speakers are like 5-10X more badass than I even knew they were. The TTV bassline and kick drum came in at seriously thumping volume, tight and clear, with no distortion or buzzing. That means that those Silver Swan woofers can pump out the volume, and without the bloated notes I was getting from the Onkyo. Oh man. It’s a combination of relief and delight. Turns out I didn’t screw up the design afterall, and not only that, the finished product ended up sounding superlative. These babies can’t top my living room system, but they can nip at its heels. WOW. And as mentioned previously, the Scan-Speak tweeters now sound even richer, more full of detail.  Cymbals sound more present, acoustic guitars seem richer.

    3. I’m suddenly beginning to seriously question if my Aiwa receiver in the living room shouldn’t be replaced. It’s sounded excellent for many years now, but the lion’s share of the credit (and then some) goes to the speakers. I now have an itching curiousity to know what my full-size units would sound like with a better amp supplying the juice. Maybe this weekend I will hook up the Marantz and do some listening.

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    12 Responses to “Are you sure you’re sure there’s nothing to an amp?”

    1. Mohamed says:

      I have all unit and speaker for this model

    2. Marantz in the pants says:

      Came across your other post on the Marantz 6100 turntable after buying one myself. Your post was spooky because my TT had EXACTLY the same problems – right channel dead, speed too low. Reading your post helped a lot. I turned out not to need the extra girth on the motor shaft, just a new belt and some lubrication. And the electrical fault was in the output wiring. I have an old Shure cartridge in it and, through my Marantz 2238 receiver, it sounds very sweet. I appreciate your posts.

    3. Frank Furtive says:

      Same amp on CL for 175.00 Overpriced? I’m leaning towards taking my 1973 Kenwood 8004 Amp to the shop to diagnose flaky
      channel. Sounds like a POT but who knows. 60/Channel and unlike most units can drive 3 sets of speakers hard without shutting
      down. Took it to a MacIntosh Clinic when new and the insignificant distortion specs were equal to Mac. 60 was conservative rating according the graph. $285 for the Kenwood in 1973, adjusted for inflation, is $1,400. Seem to recall Sugg Retail back then was around $400.

      (never realized amps can shut down until hooking up useless Pioneer SX-880 toy receiver. It konks out at minimal demand levels driving Bose and/or JBL speakers.

    4. stumbled upon your blog.
      I have the same amp that you have, I am currently struggling to connect my passive speaker ( a pioneer cs 77) and I am finding hard to connect them together. How did you connect yours.

    5. Murat Sahan says:

      Hi! Wonderful nostaligia :) The PM 750 was my first integrated amp that I bought as a teenager. Had a pair of huge gooodman speakers with it. Always loved the Marantz sound but as someone writes, the 750 did have som high noise levels. Eventually I did replace it with an PM 84 MkII, now that was something in its own class.

      Good Luck with your 750!

    6. William Stevenson says:

      I’m amazed that someone with the technical know how to build speakers would give short shift to the rest of the music chain. Garbage in garbage out–your signal source onward will all affect the sound quality. In my experience the preamp has the most influence, the amp next (both contained in your Marantz) and the signal source after that–most inexpensive cd players are closer in sound quality than the variability you encounter in preamps. It’s neat you’re discovering this–for very modest additional investments there is a ton of great used gear which always surfaces on Craigslist.

      • Well, I do stand by the philosophy that dollar for dollar, nothing else gives you more for your money than good speakers do. Building any setup from scratch, I’d definitely assign most cash toward speakers. But yes, as I grow older, some new things have gotten through this thick skull of mine! The proof has been in the pudding here with this Marantz, and going forward, I intend to pay much closer attention to amp choice…

    7. Mike Graham says:

      Thanks for taking the time do a writeup on this. I scored the same amp this afternoon for 84$ tax in, and I am sitting here in awe. my speakers are by no means true audiophile gear, ( fisher stv9705 1oo watts, and pioneer CS-G405’s) . Its still just blowing my mind. I cant seem to find much on the web about it though!!

    8. Nicolai says:

      I realized this a couple of years ago myself!
      Today, I also own the PM750DC, and I must admit that I love it! :)

      It does have a high noise floor, but that’s not something I can’t live with, cause in return it gives a great sound.
      Nice to see that someone else happily owns this amp ;)

    9. ninetenthsofshavinpowda says:

      Dude. Your amp sucks. It’s sucked for a long time. I’m glad you finally discovered that amps matter, and that it’s time to step up. But not only do amps matter, wattage matters a lot. You know this. Now pick up a SA-1000 or something. Your speakers deserve it.


      And if you do pick up something vintage…. you can always get a seperate DA convertor with a remote. That’s what I did, and it was awesome to combine vintage power with a remote. :)

    10. Sheilaa stylie says:

      Nice pics. I’ve been doing a bit of listening today and can hear the difference. Your brother is never going to get these speakers!