Marantz Model 15 Amp Questions

nelsress

AK Subscriber
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This past spring I was fortunate to pick up a Marantz Model 15 which I'd wanted for quite a while. It is in nice cosmetic condition and seems to function fine in the brief testing that I did. My intent was to have this restored before using it too much but am now considering using it for a while with a pair of AR 90's I'll be getting this coming Sunday.

As most of you know, it's an old amp, Marantz's first solid state stereo (dual mono) amplifier and as such should no doubt at least be recapped to expect to get the great sound these are known for. The question/concern I have is am I putting speakers (or any other component) at risk using an amp this old that is all original or am I just risking passive component failure in the amp itself? Should wait at least until I can recap the power supply?

Another option I have is to use my Tandberg 2055 receiver to drive the ARs but that hasn't been recapped yet either and though it's not as old as the Marantz, it's no spring chicken either. Thanks for any advice regarding this "experiment".
 
Good luck with your Model 15.
Download the service manual and follow the instructions to check the
DC offset. It's the opinion of many that these are built for the ages, and the components used were the best available at that time.
Try a cheap pair of speakers for a few days.
A recap should be relatively easy, not many in there. Most are on the driver board.
Happy listening!
 
Hi Dobieguy and thanks for your reply. I've got a copy of the service manual, when you say to check the "DC offset" is that the same as the "DC balance"? If I am correct in that assumption I am still at a loss as I don't own an oscilloscope, nor do I know how to use one if I did and I don't own a watt meter either.

The guy I got it from installed new power on green bulbs and new correct voltage overload protection bulbs. He then test played it and said it had good audio and that the relay was clean and quiet.

That being said, it looks like I need to take it somewhere to have the DC offset checked and adjusted, if need be? Is that correct? Thanks again.
 
Well, the AR 90s showed up late Sunday and we auditioned them for a while with a good variety of tunes but they weren't my cup of tea. To make sure it wasn't the Marantz, I inserted the Heathkit AE-40 cabinets with Jensen H222 coaxial drivers into the sytem and loved their sound so I passed on the ARs.

From what I've read, the general consensus is that these Jensens sound best with a tube amp but this Marantz 15 really makes them sing, I thought it was a great combination. I am using a Dynaco PAS-4 tube preamp though so perhaps that has something to do with it, I don't know. Or perhaps it's the fact that many say the Marantz 15, being their first solid state stereo (dual mono) amp, has a "tubey" sound. Either way, I like it a lot so far stock.
 
Hello,

i can say without any doubt that the model fifteen is one of the best sounding Marantz solid state power amp and i have owned a few of them except the model 500/510 :)
 
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Hello,

i can say without any doubt that the model fifteen is one of the best sounding Marantz solid state power amp and i have owned a few of them except the model 500/510 :)

I see you have a 16B. Does the 15 sound better to you?
 
Good question :tresbon:

They are both excellent but for me the fifteen sound more natural .
I have not listen to my 16B since a few month so it's time to hook it up and see how good it is :music:
 
I see you have a 16B. Does the 15 sound better to you?

I have been using a completely rebuilt Model 15 with a 7T preamp as my daily work shop setup for the past 4 months, it replaced my rebuilt 16B and Model 33.

I would say that there is noticeable difference in the presence of the music with this set up. I attribute this not only to the Model 15 but the 7T also. I find that the 7T adds a measurable improvement to every early Marantz amplifier I have used it with.
 
Thanks for the input, Chris. Did you do the work on your Model 15 or did you have someone else do it? My plan was to send it to Marantz Instrument Resources eventually since he (I think his name is John but can't remember for sure) specializes in the Model 15 & Model 16 and seems to know a lot about these amps from the phone conversations I've had with him. He also recommended the 7T, which I found and purchased but after a couple years of not being able to find a Model 15, I got rid of that preamp and picked up this 15 about a year later. So far though, without being rebuilt, it sounds excellent with the tube pre I've got it paired with. Thanks again, Chris.
 
Thanks for the input, Chris. Did you do the work on your Model 15 or did you have someone else do it? My plan was to send it to Marantz Instrument Resources eventually since he (I think his name is John but can't remember for sure) specializes in the Model 15 & Model 16 and seems to know a lot about these amps from the phone conversations I've had with him. He also recommended the 7T, which I found and purchased but after a couple years of not being able to find a Model 15, I got rid of that preamp and picked up this 15 about a year later. So far though, without being rebuilt, it sounds excellent with the tube pre I've got it paired with. Thanks again, Chris.

I did the rebuild myself. John at MIR is an excellent guy and he really understands these early amplifiers.

Now you've gotta find a 7T:D
 
Hello Chris ,
good to hear you :thmbsp:
When you say completely rebuilt about your model 15 could you tell which parts do you have changed and if you have listen the amp before ?
Congratulations , i have heard that the model 15 is not the easiest amp to repair ...
 
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I would refurb the 15 before using it... They have some odds and ends that like the bulbs that wear. If a lamp blows it can burn out some resistors...and worse.

There are 3 different versions of 15.

I have to say, I like my 15 over my tube amp... I fully refubbed the 15.

Right now I am running the 7C with the 15 and a pair of Ohm Walsh 4s. Oh my my.....

Johnk
 
to roughly check the dc balance without a scope is quite simple ..just measure with reference to chassis ground the outside cases of the output transistors .the collectors .. one of each side should measure rail voltage the other ones measure roughly half that .
i am assuming by what has been written in this thread it is a cap coupled amplifier and if correct the above is correct .
this cannot be accurately set without a scope so if way out it needs servicing .

i should have checked the schematic instead of assuming .. the 15 isn't cap coupled so the above doesn't apply .
 
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The guy I bought it from did install new power on green bulbs and new "correct voltage overload protection bulbs" before he sold it to me. He also said that he checked the relay and that it was clean. The example I own is either version I or II. I remember reading about the differences and figuring out which it was but have since forgotten and (as usual) didn't write it down.

Thanks for the "rough" DC offset checking instructions jstang, when I get a chance I'll look over the manual and see which are the output transistors (if I recall they're the ones on each side under the perforated covers) and put my meter to work. Nice to hear that you like your 15 over your tube amp-what tube amp do you have? If you don't mind me asking, what does fully refurbing a 15 entail and? Drop me a pm if you ever provide that service to other AK members. Thanks again.
Nelson
 
All electrolytics need replacement, sometime the bias circuits need some help, the transistor need new grease and micas... Some of the heat sinks were machined incorrectly and cause mica shorting...

Lamps ( over load and pilots ) need replacement....

Full testing... Load, DC, freq range, bias,....critical voltages. They really should be tested fully, as age can cause drifting that would be normally not be seen in newer units.

They are a little difficult mechanically to deal with.

But they are well worth the effort... They run cool and have enough transformer kva capacity for twice the power....

Oh the tube amp is an 8 clone...sounds really nice, but the dual mono block design of 15 can be heard the second you turn up the volume... And my speakers tend to need more power.

Johnk
 
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Thanks for the info John. Sorry for the delay, I got engrossed in trying to get enough info so I could recap these Jensen coax drivers... still looking. Anyway, I realized about a year and a half ago or so, when I spoke with John at Marantz Instrument Resources for the first time, that there was a LOT to go over in these old amps and potentially a lot to change out. Quite the time consuming process to go over them completely and get them back to spec or better. Parts too can be quite costly as he told me the specs for the transistors for example can be all over the place so he tests each one and matches them with others of the same reading to make groups for individual amps. The prices have gone up, plus he's got to but a LOT of transistors to get matching sets like that. It all adds up.

I'm not sure what you meant when you said the dual mono block design of the 15 can be heard the second you turn up the volume? Was that a testament to dual mono block design in general or the Marantz Model 15 specifically? Thanks again John!
 
Like the 15 a lot, but mono blocks have a special place in my ears.... They just seem to maintain a purity as they are pushed hard. The first amp I built was a dual mono block.

So my ears tend to tune in to them.... Very clean left-right regardless of what is taking place.


Johnk
 
I agree on the positive review of the 15s. The 15 sounds best compared to the 16s and the 250. I use the 3800 as preamp and it has more ample bass than the 7t. The 3800 + 15 combo is very 3D like and fantastic mid to die for.
 
Fabulous Amp! The 15 is my new buddy. The Marantz 2226B hit the shelf for now. Beautiful wood case! All operations through the Bluesound Node. No preamp needed for this pup. Sounds as good as my Cary SLI-80 tube I use in the Winter to heat the Mancave here in TN. Of course… my Klipsch Cornwalls sound incredible… soft or loud.
 
Fabulous Amp! The 15 is my new buddy. The Marantz 2226B hit the shelf for now. Beautiful wood case! All operations through the Bluesound Node. No preamp needed for this pup. Sounds as good as my Cary SLI-80 tube I use in the Winter to heat the Mancave here in TN. Of course… my Klipsch Cornwalls sound incredible… soft or loud.
I really liked the model 16 I restored about 10 years ago. I've switched to tubes since then, but the amp is still humming along just fine for the new owner.
 
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