Quality Service for Quality Equipment

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305 East Braker Ln. / Austin, TX 78753-2746
Phone: (512) 458-8292 Fax: (512) 453-4542
tech@Pyramid-Audio.com

LEVINSON MUSINGS
No26 and No28

Before we became the authorized service center, the first time I saw a Levinson preamp I thought it was senselessly complex. Years later when I looked at the measurements, schematic and after a couple of minutes I realized that it was a flawless implementation of current sources, differential pairs and cascode configurations.  Even with my Audio Precision test set the distortion is virtually un-measurable 0.0009% and the signal to noise ratio is typically over 110 dB. The typical problem is bad relay contacts, so we replace all of the relays. We also replace all of the capacitors with a history of issues and the result is like new.

No38/380   sometimes bad caps or  Harris  CMOS here and there but quite reliable.  No phono input.

 

The No32 320 326 are very  similar using an electronic volume control built up of discrete component switches improving the s/n to over 120 dB and still use  the same output buffer design.

No30 30.5 and 35   
The heart of these Levinson D/A converters is the Ultra Analog D20400 block. Fantastic performance even by today standards for a 20 bit design. Unfortunately UltraAnalog went out of business with no notice. Then the part started failing and no one had spare parts. The Levinson solution implemented in the No30.6 was to switch to hand selected PCM 1704 and OPA627. Based on that idea we made two drop in solutions that works for both the No35 and the No30.5

On top of the D20400 issue the more common problem with all three of these models is heat. When dealing with shielding and digital circuitry heat can get trapped and capacitors age very quickly. So far we have been able to complete every repair of this generation we have seen.

The No36 is a later design that used the PCM 1702. The follow up No360 uses the PCM1704. Both once again use the fabulous discrete Levinson output buffer stage. The No36 has bad caps that can ruin the main circuit board. The great news is we have a stock of No36s boards as replacements.

 

My personal opinions of two channel Mark Levinson amplifiers.

Have you checked the price of modern amplifiers lately? Almost any first class amplifier in the 200 W per channel range is costing $10 to $20 THOUSAND. I think you should seriously consider having your old amplifier repaired. First class designs from 20 years ago are still awesome and rarely been improved upon.

No23 and No23.5 have amazing build quality.
Most problems have nothing to do with a design weakness but are simply due to their age. For almost 30 years now they have cooked themselves to the point of failure. Service is difficult because the internal construction has no connectors. That’s right, everything is soldered in place.
Not only that but the common problems are not so much capacitors but a fair number of resistors that have aged and have become noisy and there are a number of capacitors that need to be replaced. The good news is the very largest electrolytic capacitors almost never fail and that does keep the price down to some extent. However the repair takes in the neighborhood of 30 hours. The result is an amplifier with the original specifications and classic Mark Levinson sound. So the bill for overhauling the No23 or No23.5 typically runs about $3000, maybe a fifth of the replacement cost.

The No27 amplifier is another favorite classic of mine. While less power than the No23 the No27 is especially well-suited for very high efficiency speakers. This is due to the unusually low noise floor of the No27.

The 300 series of Mark Levinson amplifiers are arguably the best Levinson amplifiers I know of. The first series 331/332/333 is about  4  dB noisier than the follow up 334/335/336.  Unlike the 400 series the 300 series heat sinks are external and larger than any other 2 channel Levinson. They are mechanically silent yet new enough to have not cooked themselves to death like the No23. There are a couple of known issues with the 300 series related to the main capacitors. This has nothing to do with Levinson but instead a bad batch of capacitors supplied by Philips. When these capacitors fail there will either be distortion or hum. Yes there are small capacitors that do fail and unfortunately when these capacitors short out there are a fair number of parts that burn. It is a very good idea to have this work done before failure.

No431 432 433 434 436
Of the 400 series of amplifiers my favorite is the No436 monoblock. You get: fan cooled internal heat sink, very low noise,very low distortion, and lots of power. The 436 is arguably the best measuring of the 300 or 400 series of amplifiers. Down side I you need two to make stereo.  The rest of the 400 series can get noisy and like the No23/23.5 usually has noisy resistors. 

 

No33 and No33H
What great fun, build an amplifier like no one else. These are monophonic amplifiers so yes you need two for stereo. The internal design is actually two amplifiers in a single chassis brought out in a bridge. The No33 reference amplifier weighs approximately 400 pounds in the crate. The H suffix of the  smaller brother stands for half size. I have seen references to a 33junior but the final production name was the 33H. Both of these models included another amplifier that was simply used to generate clean AC for the driver stage. Unfortunately that is the weak spot in theses amplifiers. So far we have been able to repair every amp we have taken in. The Levinson goal is to service a piece of equipment and restore it to the original performance and reliability. So like the 23, the 33 and 33H are moderately expensive to repair, but nothing compared to the replacement cost.

 

TEST JIGS
We have test jigs for several Harman circuit boards.
Test jigs allow us to repair a circuit board and test it before re-installation, certain that it is working properly. We also have complete models. We can swap boards if necessary to determine where the problem is. For Levinson the: 300 series, the 400 series, the No35, the No40, and the No502. For Proceed we can support the HPA2 HPA3 and the AMP5.  Please contact us about PCB  support.