Details on the remarkable PROTON D540 Integrated amp's huge 530 watt power output.

Gentle reader,

I have written about the marvelous series of amplifier that PROTON once produced with their exclusive and very effective Dynamic Power On Demand or DPD as they called it.

Unique PROTON D540 Integrated Amplifier has entered the Listening Room and here: 

Unique PROTON D540 Integrated Amplifier has entered the Listening Room. Part TWO 

I wrote in the first article: They designed the power amplifier section with two transformers and sets of capacitors. In normal operation it is Class A. When a crescendo (I love that word, say it out loud: cre-shen-doe) happens, super-high-speed switches cut in the second transformer and it provides the needed power, up to 150 watts into 8 ohms, 280 into 4 ohms and a staggering 530 watts into a 2, yes a TWO ohm load! It will last up to 1/2 second! It revolutionized audio thinking. Hirsch concluded that this design practically negated the need for large heavy expensive and power hungry amplifiers. It was more than capable of meeting 99% of music needs for a fraction of the size, weight and price of far more powerful amps.

First, here are some photos of one of mine, I have two, one as a spare:

Less often used controls are hidden, above.

Above shows their DPD logo.

There are those that refer to PROTON products as being NADs of another name. I was looking at NAD amps on eBay and came across one that was very similar on the rear as PROTONs. The differences are inside. I should have saved a photo of the inside to show you, but didn't. Just because a factory uses the same chassis and other common parts does not make them the same items. I saved this photo from one auction of the rear.

Very similar indeed. I wish the D540 had these proper three-way binding/banana speaker terminals. Otherwise, I choose PROTON.

Those U shaped devices connect the preamplifier section with the power amplifier portion. The D540 can be used as an integrated amp, preamp or power amplifier, simply by removing those connectors and connecting to either a preamp into the MAIN-IN or to a power amp from the PRE-OUT RCA terminals. The manual asks that you plug the unused terminals in this case with what's called "shorting plug". I did so when I have used the D540 as a preamplifier.

Now, I will show interior shots and describe what you are looking at:

Above shows the entire interior. Interesting heat sink design with those curved vanes. The heat sink disipates the heat that the power transistors produce while amplifying the music. The large black cylinders are capacitors that store energy from the transformers. The smaller four are for normal 40 watt max operation. The larger two are for DPD output.

The board above is the phono (turntable) section.

Above are the two power transformers that make up most of the weight of the amp. One powers the 40 watts and the below transistors, the other powers the DPD's above 40 watts crescendo signals.

Above and the two photos below show the bottom of the components. Unusual design in having the power transistors on the bottom, but it helps make the chassis more compact.

Above and below are the previously mentioned music power transformers. The smaller (C2837) units provide Class A performance up to the 40 watt threshold. The much larger (2SA1215) transistors enable the music to remain undistorted during peaks of loud music.

I recently had a problem develop with my first D540: In one channel while playing records, a sound like loud Pink Noise started joining the music. An audio expert friend of mine told me the main transistor in the phono section, shown again, below is at fault. Well, I assembled kit equipment when I was young and even troubleshot and repaired our first color TV long ago, but getting into fixing that issue, I will pass.

As a result of that issue, I pulled out the "spare" D540 and swapped the two. But since I wasn't using my super rare Dynaco Stereo 200 power amplifier, I decided to use the new D540 in a preamplifier role. I found it too has a quirk. The balance control works backwards! All right channel sound comes out of the left side and vice versa. So, I simply swapped the cables connecting to the inputs on the Dynaco and all is right in the stereo system again. Below is a link to that blog post:
Stereo System: Time to make some changes: Dynaco Stereo 200 PLUS Banana Plug lesson.

Thanks once again for looking, there has been unprecedented readership lately since I joined the now-closed FaceBook group: Vintage HiFi and Stereo. The quickly are generating multiple hundreds of page views. Your taking the time to read my humble blog truly warms my heart!

Scott