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Vintage Audio Suggestions? Considering Marantz and NAD. "Snowy" sound in my current amp.

post #1 of 12
6/22/11 at 1:59pm
Thread Starter 

Hi, this is my first post here, and I am just getting into higher end audio. Right now the headphones that I use are Sony MDR-7509HD. They have low impedance, so I don't think I will need any sort of dedicated headphone amp for them. What I do want is a vintage amplifier with a clean phones output and a good phono stage.

 

Currently I have a Kenwood KA-2002a amplifier from the 70s. I like the sound, but it has a slight "snowy" sound that is always audible when there is no source playing or when there is a quiet part to a song. This bothers me. I have skills in soldering and electronics, so I think I may try to change the filter capacitors in it. It still has the originals, and I think these may be responsible for the snowy-sounding hum.

 

Another amplifier I have is a Marantz SR4000. It is not nearly as old; it's from around 1999 or early 2000 and has clean output, but I would rather get something better for headphone output.

 

So does anybody have any vintage amplifier recommendations that I should look at? As the title says, I am considering vintage NAD and Marantz gear. I shop on ebay, so specific model number suggestions would be helpful. Or does anybody think I should skip buying another amp for now and just try to replace some components in my vintage Kenwood amp? Thanks in advance.

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post #2 of 12
6/23/11 at 12:09am
You're right on track. I'd drop some new filters into the Kenwood. Maybe replace the rectifiers, too. Won't cost much and that should clean it up.

Though NAD and Marantz made excellent stuff. If you want to pick up something from them, you can't go wrong. If tubes interest you, think about the old H.H. Scott and Stromberg-Carlson integrated amps. In my opinion, they're undervalued and just waiting for collectors to drive prices up. You might want to grab one while you can for a few hundred. Most will require surgery, but it sounds like you can handle it.

Also, the MDR-7509HD is a great headphone. I've had a pair for a couple years and think highly of them. I'm not sure why they aren't more popular here.

Anyhow, I'm glad you showed up at Head-Fi. Please stick around - we need more people like you. smily_headphones1.gif
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post #3 of 12
6/23/11 at 6:10pm
Thread Starter 

Thanks for the suggestions! I had not heard of changing the rectifiers, so I will research that. I am interested in tubes, but I have never even had the opportunity to listen to them since I don't know anybody else in real life that cares about audio quality. Someday I will buy that kind of gear once I can afford it. Right now I'm on a very low budget, so solid state is my best bet.

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post #4 of 12
6/24/11 at 3:28pm
Quote:
Originally Posted by CAT5e View Post

I don't know anybody else in real life that cares about audio quality




i know what you mean...anyways the filter caps can help clean up the hissing and humming a bit but most likely sign of humming is the dc offset is kinda out of whack as well. might have to reset the current bias also cause it could of drifted off over the years. only lot of direct coupled amps you really don't have to worry about when it comes to current bias cause they tend to stay better stabled over the years of use.

you can go to hi-fi engine for schematics and manuals for speakers and amps. they might have it or not. you have to join tho but it's free and quick so it shouldn't be a big hassle. for marantz and NAD opinions. i can't really say. i barely had experience with any. i know of others. H.H scott is a great suggestion above. they also have wonderful under rated solid state gear. i had good experience with sansui,yamaha,kenwood, rotel and Fisher amps too.

it most likely be cheaper to bring your kenwood up to spec defiantly over buying vintage marantz gear cause marantz gear(even low end) go for crazy prices and continue to sky rocket in price just cause of the popular name brand.Pioneer is another that hits crazy prices i think. if it was me i'll probably try to fix up the kenwood first and see how it goes if you are positive you can can fix it and if still not pleased with the results then you can search for other amps as an replacement.
Edited by RexAeterna - 6/24/11 at 3:30pm
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post #5 of 12
6/24/11 at 5:39pm
Thread Starter 

I'll check out that site for the service manual. I probably won't find it since I have somewhat of an obscure model, but it's worth a try. I'll look into how to correct the DC offset since I had never heard of that being a possible issue. Thanks for the suggestions!

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post #6 of 12
6/25/11 at 7:22am

Quote:

So does anybody have any vintage amplifier recommendations that I should look at? As the title says, I am considering vintage NAD and Marantz gear. I shop on ebay, so specific model number suggestions would be helpful. Or does anybody think I should skip buying another amp for now and just try to replace some components in my vintage Kenwood amp? Thanks in advance.


Not sure if it's considered vintage, but my old NAD C370 was marvellous. Bags of power - drove effortlessly my 6ohm floorstanders - and a fantastic headphone out. 

 

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post #7 of 12
6/26/11 at 8:28am
Thread Starter 

Hmm that particular model must be rare because there are currently none listed on eBay, and there is only one listed under completed items. It went for $350 with one bid.

 

I have ordered a few parts to put into my Kenwood to see if they help clean up the signal. I ordered an 80V Rubycon 2200uF capacitor to replace the large old 50V ELNA 2200uF capacitor. I ordered a replacement pair for the two second-largest capacitors. It looks like at least one of these is wired directly before the phones output. They are 25V ELNA 1000uF axial capacitors and I will be replacing them with axial capacitors of the same value but from some German brand called Roederstein. Hopefully these will make a positive difference. Since the amp is so old I may also eventually replace all of the capacitors on the board, but the three that I will be replacing are too large and mounted off of the board.

 

One other product that I ordered was a 2mL tube of DeoxIT. That stuff is so expensive for a tiny bit, but everything I've read about it was pure praise. Originally the potentiometers in this amp were very scratchy. The whole inside of the amp was covered in filth and dust, so naturally the pots were rough. I sprayed some special electronics contact cleaner down into the pots. It was just some old stuff in a spray can that my dad had in our basement. It actually did clean up the scratchiness without destroying anything, but it did not say that it would lubricate. That is why I figured it would be a good idea to go ahead and buy the almighty DeoxIT.

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post #8 of 12
6/26/11 at 3:28pm
i use radioshack stuff and it works fine for me. not only for cleaning controls of amps but great for cleaning thermal paste off of cpus/gpus and cpu/gpu heatsinks. if you ever looking for an amplifier for good price with lots of power and low impedance speaker driving i suggest look into yamaha R-9. under rated amp of all yamaha brand. powerful amp and natural sounding. great for low impedance loads 4ohms and under and great for driving PA speakers or as a dedicated subwoofer amp or subwoofers through bi-amping. you can score one around 100 bucks mint condition if you find one. i have one and love it.well for speaker use. i never really enjoyed any of my headphones out of it. i use as my main amp for speakers and for high impedance headphones(like my 600ohm sextetts) i like to use either my sansui 5000x or my smaller guy hitachi HA-2 amp. my little hitachi surprisingly sounds wonderful and natural with my akg 240 sextetts LP and has an output impedance of 680ohms. i mostly use my little hitachi cause it doesn't do so well with my speakers(cause can only handle 8ohm loads for speakers. if any lower or impedance dips too low it'll go into protection mode).
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post #9 of 12
6/26/11 at 4:45pm
Thread Starter 

Thanks for the suggestions, though right now I'm not really looking for a amp to drive speakers. I became interested in headphones because I will be going off to college in the fall and didn't want to have to leave my music behind! I will however take some small speakers with me. The best smaller pair that I have right now are my  Mini Advents. They sound pretty good and surprisingly the foam has not yet rotted. They lack in bass, but I guess for a dorm room I really don't want booming bass.

 

In my room at home right now I have a pair of NHT VT-2 tower speakers. I got them at a pawn shop for what I thought was a bargain (paid $100 and I knew they were originally a $1,700 pair of speakers), but when I got home I realized that the dome tweeters were not functioning on each speaker and the four mid-range drivers had all been removed and replaced with terrible Optimus speakers. However the original woofer on each was intact and working. I'm pretty sure that I am going to buy a pair of VS-2 (same speakers but without the woofer) and swap all of those parts into these. Another problem is that these are power hungry, so I will need some kind of amp that can really put out the watts that they demand.

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post #10 of 12
6/26/11 at 6:19pm
if you ever need a second small amp capable of driving high impedance headphones if you can find one the little hitachi HA-2 is great and way out of the radar for vintage amps. i got mine at a local goodwill for 5 bucks. it seems to be a great all rounder even tho it has a high output impedance of 680ohms. i driven some low impedance akg 240s and sennheiser hd555's out of them and sounded great as well. it's great as a dedicated headamp i think and small and compact. i just don't and probably never recommend it for speaker use unless your light on the volume knob and know for sure your speakers are at least an avg of 8ohms across the full frequency range. hope you get the kenwood up and running. i like kenwood amps myself.
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post #11 of 12
6/29/11 at 9:00pm
if you want to tweak your amp, it is good to have the service manual or diagram of the amp.

try to google " service manual".

if you cannot found anything, for Vintage audio equipment servive manual diagram you can try www.nostatech.nl or www.nostatech.com

I got my old cd751 cd player complete service manual and diagram from this site.
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post #12 of 12
6/30/11 at 9:22pm
Thread Starter 

Thanks, I checked on that site and still didn't find any documentation for my KA2002A. Previously I checked on the Hi-Fi Engine site that RexAeterna mentioned, but I only came up with the schematic for the KA2002 model which is different than mine. However I guess I'm not really in need of a schematic right now since all of the functions are working and the only issues is some slight noise.

 

Today I got my 2 mL vial of DeoxIT and I dripped it into the potentiometers and put some on the headphone output and source inputs. It definitely further improved the potentiometers. They're not scratchy at all any more and turn very smoothly. I think it even reduced the unwanted noise a bit. I haven't received the three replacement capacitors yet, so hopefully they'll do the trick.

 

 

Oh and another thing to add: Just yesterday I ordered an M-Audio Audiophile 2496 PCI card so that I can make high quality vinyl (or any other analog source) to digital conversions using the tape output on my Kenwood amp. Since I really like the phono stage in my Kenwood I'm hoping that this is a great solution for what I want to do. I looked at a lot of the gear out there that is USB based and it just didn't seem like it could be as good as this setup. Once I get that card I can comment on the quality.


Edited by CAT5e - 6/30/11 at 9:29pm
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