Mark Levinson 331 amplifier repair.

daddyjt · August 28

I started this project earlier this year, and just wrapped it up this week. I posted a step by step on another forum, and thought I’d post some of the highlights here since it had a happy ending…

Posted February 10
A little backstory on this amplifier…

I bought this used at an estate sale about 7 years ago for $900. The guy that owned it had the power supply caps and intended to replace them to correct a “known issue” with the Levinson 3xx series (more on that in a minute). The gal I bought it from (daughter) had even located the original box and packing material. This is a BEAST of an amplifier, weighing in at 120lbs - with lots of sharp edges, lol. A couple years ago, it developed a 60hz buzz in the left channel, which is a hallmark of the aforementioned “known issue” - The power supply has 4x 44,000uf 75v caps, and 4x 1,900uf 150v caps. That’s 183,000uf of power supply capacitance! Anyway, the “known issue” is the 1,900uf 150v caps. Apparently they were under-speced and virtually always fail. The solution is to bump up to 1,900uf 250v. This is a true dual-mono amp, with dual .8 kva transformers, which contributes substantially to the weight.

When the amp developed the buzz, I popped it open to replace the caps… Full stop. This thing is built like a jigsaw puzzle (see photos below). I had neither the time nor inclination to tear into it, so into the storage room it went. Fast forward to October of 2023, this amp was in the path of the flood we had at our home, where it suffered very minor water exposure (water did not even enter the internals of the amplifier). I learned about how insurance works on items such as this - they take the original value of the item and pay you half. Then, if you replace the item, they will pay anything you spend OVER the half they paid you, up to the original value. For this amplifier, they calculated original value at $8,000 - so they paid me 4k, and would have paid an additional 4k, IF I spent over 4k on a replacement. Needless to say, I have no need (or desire) for an $8,000 amplifier. My plan was to ship in to Levinson and have the caps done. Well…. Levinson refuses to work on this amplifier, as it’s “aged out” of their service agreement. Further, Levinson (Madrigal) refuses to release schematics. That leads to a service network of exactly THREE people in the country. Worse, a recap on this amplifier can be expected to run between $2,000 and $3,000 (NOT including shipping). Ouch.

Theres something liberating about having nothing to lose. I decided that since I’ve been paid out 4x what I spent, I’m going to take a stab at it, and I figured you all might want to tag along…

daddyjt · August 28

I have never dealt with an amplifier that had such an extensive mechanical component to assembly/disassembly. I’m in to this about 6 hours already, and I just barely got to the caps…

daddyjt · August 28

Ok, so first quandary.

The stock caps are 4x 44,000uf 75v (the big ones), and 4x 1,900uf 150v (the PROBLEMATIC ones).
The caps I received with the amp are 4x 47,000uf 80v, and 4x 1,900uf 250v (which solves the PROBLEMATIC)

There is no issue whatsoever with the 1,900uf replacement - they are the same diameter (35mm), and the increased height (80mm to 94mm) poses zero issues.

The PROBLEM is the large caps. Stock are 52mm diameter X 144mm height. The replacements I got with the amp are 76mm diameter X 92mm height. (See photo)

So the first decision is, do I use the caps I have (more on how this would work in a second), or do I order the actual spec caps from Mouser for about $200. The caps I found are 46,000uf (+2,000uf) 75v (same) and same dimensions - easy pesy. This is the Mouser replacement: https://www.mouser.com/ProductDetail/Cornell-Dubilier-CDE/DCMC463U075BF2B?qs=asKUzMMwyr6J4YVZ97Zq9Q==

If I use the ones I have, there is plenty of physical space for them, BUT… it would require fabricating a new bracket (x4) to hold them (which I CAN do), and worse, it would require modification of the metal connecting “straps”. As you can see in the photos below, these large caps are not electrically connected with wires (that would be FAR too easy!), but rather with an intricate labyrinth of 12 gage (0.1” or 2.7mm) thick steel “straps”. It is one of the most asinine things I’ve seen, as I am fairly certain that the current involved with these caps could easily be handled by 10 or 12 gage wire, but apparently the engineers at Levinson thought otherwise.

the modifications would be to notch the grounding strap to accommodate the ~5mm shift away from the center of the amp(red square) and drill a new hole (red circle) for the opposite screw mount in the + strap. OR, cut the positive strap (blue arrow), drill a hole (blue circle) and run a small 10g wire from the cap to the strap.

daddyjt · August 28

Posted February 13
Ok, that didn’t take long - I realized that the modification I outlined above would have to be completed FOUR (4) times. FOUR.

Caps are on the way.

Next topic - binding posts…

daddyjt · August 28

I finally got some time with this beast today. A couple things - The capacitor “straps” seem to indeed be copper. I got them on the buffing wheel today with a mild cutting agent to remove the discoloration/Schmitz that coated them. A bit of buffing revealed…. Copper. Though it appears to be some sort of alloy, as it has a decidedly light look. Anyway, I buffed all the visible surfaces (from the top of the amp), and then I just buffed the points where caps/wires connect.

Next up is binding posts. Levinson uses these stupid “winged” nuts on their posts. They seem like a good idea (the wings add leverage to torque the spades down tight), BUT - the wings break under heavy torque - 3 of the ones on mine were glued from previous breaks. PLUS, they don’t accept bananas.

id like to replace them, but 2 things - I don’t want to spend $20 a post (x8), AND they have a square plastic protrusion that seats in a square hole in the amp chassis. The square cutout in the chassis is too big for most posts unless I use some kind of washer. So I don’t want to spend a lot, but I want to be able to use bananas, and I don’t want it to look trailer-park.

I might have a solution. I have 2 pair of these nice Rhodium plated posts that are nice, heavy and accept bananas. The clear round plastic bushing fits almost perfectly in the circle surrounding the square hole - this circle is cut in the sheet material that displays all the printing on the back of the amp. It’s about the thickness of a piece of construction paper, so it creates just enough of a “well” to center the post bushing (see photos).

The length of the post threading is going to be VERY close to long enough because…..

The Levinson does not use any wires to supply the binding posts. Nope - you guessed it - more metal strapping. So, each post has to accommodate: The plastic bushing, the amplifier chassis, a nylon washer, a steel washer, a jamb nut, 2x metal straps, and the final nut. (See photos)

Also, I only have 4 of these, and I need 8 - and I can’t remember where I got them:-(

daddyjt · August 28

I member on the Carversite had 4 of these sitting around, and shipped them off to me…!

Posted July 26
Well, it’s been a minute (or 4 months!), but I’m getting back into this thing - mainly because the wife is starting to ask gentile but direct questions. “Do you need parts for the project on the ping pong table?”…. “Did you get in over your head with that amplifier?”… “I wonder how it will sound when it’s fixed…”

So I got the new supply caps installed in the right channel today, as well as all the strapping and new binding posts.

When I started disassembling the left channel, I immediately discovered the source of the aforementioned buzz…

daddyjt · August 28

Posted July 28
Got a bit more done today. A few notes here, if you ever have the misfortune of working on one of these beasts -

Each channel has four (4) supply caps - 2 of the big ones (46,000uf) and 2 of the smaller ones (1,900uf), broken up in pairs, one big and one small. They are held in place by a very thick bracket that is mounted to the chassis by 3 screws - 1 on each end, and 1 in the middle. The thing you don’t realize until you remove one, is that they are very “springy”, and expand in length by over an inch when removed. Getting the one I removed back in place took close to 3 hours - trying to compress it and find/thread the screws at the same time… needless to say, I did NOT remove the other 3 - I just loosened the screws so I could slide the old caps out, and the new ones in. Here’s the bracket I removed, and where it lives within the amp…

Next thing is the strapping or bars that connect the caps and binding posts. This is the real headache of the amp. Seriously, 10ga wire would have been MORE than sufficient…

anyway, the straps are a puzzle in the order in which they must be removed/installed, and they were VERY oxidized. They appear to be Copper with some other metallic coating. On the first channel I did, I spent hours buffing the bars. On the second, I just buffed the contact points (still took over an hour).

daddyjt · August 28

Posted Monday at 11:32 AM
Standing back with my arm outstretched, fire extinguisher on the table (I’m not kidding), I tapped the power button this morning. Standby mode activated without a problem. Next, the moment of truth…

a second push of the power button. Relays clicking, then a solid red light - so far, so good. A quick voltage check across the test point (capacitor) shows voltage within 2v of spec! We have a heartbeat!

all 4 voltage points are very close, but the service manual advises a TWO HOUR warmup before adjustment. Another quick check of the binding posts shows no significant DC offset either…:-)

Just got all the settings - voltage rails x4, bias x2, and DC offset x2 - done, and got the whole thing reassembled. Going to grab an old pair of bookshelf speakers to test it out, before moving it into my 2ch system…

daddyjt · August 28

Posted Monday at 06:50 PM
I hooked it up to an old AMC preamp, NHT ST4 speakers and my IPad playing some music ro make sure it wouldn’t damage my 3.3 speakers. All good, so I had my son help me relocate the Levinson to the wheeled dolly, and got it hooked up in the 2ch system (Oppo 105 to a BiilD C1 (with new black faceplate) to the Levinson to the NHT 3.3 pair).

Best news right out of the gate is that the 60hz buzz in the left channel is completely gone. In fact, the amp is DEAD silent at idle - yay! Next great news is the binding post upgrade - while I’m sure Mark Levinson purists would argue the point, the stock posts were fundamentally flawed not only because they are prone to breakage (3 of mine had previously been broken and glued), but worse, they did not accept banana plugs. Thanks @wrf for the extra set of 4 that perfectly matched what I had on hand.

The first track I listened to was Sandman by America on SACD. This track throws the widest soundstage of anything I have ever heard. While the Levinson did well, it was not quite as good as my upgraded 9t pair.

Next was Takin’ it to the Streets by the Doobies on SACD. This is where we started to realize the allure of Levinson. It excelled at bass control, and this tack has a fantastic snappy bass line that can come across a bit muddy - the Levinson was magic here.

Next was my all-around go-to, Private Investigations by Dire straits on SACD. All I can say is wow - the separation, staging, dynamics… superb. Better than the 9t pair? Different…

then I ran through some FLAC files by Erasure, Katie Melua, Klymaxx and Adele. After my limited listening, I will summarize by saying that the Levinson is exceedingly forgiving, making less than perfect recordings really shine. The Silver 9t pair are brutally honest, and less than perfect recordings can sometimes suffer at their hands. But where the Levinson really shines is its bass control. NOTHING sounded even remotely boomy or muddy - phenomenal.

I will be playing with this for many more hours. More to come…

treitz3 · August 28

Natalie Merchant...I think that is the chick's name...try streaming the, "Peppery Man".

Tom

pitdogg2 · August 28

Very nice job @daddyjt !!

VR3 · August 28

very nice! I hope I can post similar conclusions to my repair! :-D

BlueBirdMusic · August 29

skipshot12 · August 29

Exceptional work right there, congratulations on the finished product.

SCompRacer · August 29

High marks! Nice work!

heiney9 · September 4

Nice, a job well done!

H9

HzTweaker · September 5

Cool thread, cool amp excellent work!

daddyjt · September 9

I’ve been living with this amp for a couple weeks now, and it’s safe to say it has earned its place in my 2ch system. I will keep the Silver 9t pair, but they have been benched for the foreseeable future. I was worried at first that I was tilting towards the Levinson out of both brand confirmation bias and pride that I was able to pull off the repair. However, I A/B swapped it with the Carvers over 20 times, and the differences were clear and undeniable to both me and my son.

It really comes down to 2 things - bass control and depth of soundstage. The Carver pair is no slouch in the bass department, but the Levinson adds a bit more depth and A LOT more control. Bass is “pulled out” of the drum sound to a high degree, allowing for a more snappy and distinct sound. As for imaging, the Carvers throw a great, wide soundstage, but the Levinson adds tons of front to back staging that’s impossible to walk away from.

Now I need to find a more permanent stand for it, and get it off the wheeled dolly🤣

maxward · September 9

Great thread!

Nothing says high end like a Harbor Freight dolly in the system.

VR3 · September 9

Love it.

I had a 335 before the 33 Monoblocks and it was an easy winner over many amps before it.

Like you said the front to back staging capabilities coupled with the bass was just in a class of its own!

daddyjt · September 9

maxward wrote: »

Great thread!

Nothing says high end like a Harbor Freight dolly in the system.

I’ll have you know that’s a top of the line Home Depot dolly…😎

agfrost · September 11

Hey, the carpet on the dolly isn't covered in dirt and oil stains, so that's pretty classy in my book!

Nice work, enjoy the (audible) fruits of your efforts!

bikerboy · September 11

Great job fixing this monster amp. What amazing straps to connect the caps. I bet you were relieved to find the bad cap. Happy listening and great job

Mark Levinson 331 amplifier repair.

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