Ultimate amps for the ultimate loudspeaker

From left to right, the Quad 303 power amp, 33 pre-amp and matching FM3 tuner.
From left to right, the Quad 303 power amp, 33 pre-amp and matching FM3 tuner.Quad

Even though my search for the ultimate home music-reproduction system will probably never end, I think I’ve gotten very, very close to what I believe is near-perfection. At least, mind you, near-perfection in my price range.

Previously, I told you about my search for the perfect loudspeaker and also about the months and months of testing of amplifiers and associated equipment to make my dream speakers sound their best.

But I’ve saved the best for last: I’ve finally settled on what I think is some of the most amazing-sounding hi-fi gear I’ve auditioned to date.  And the best part is that what I’ve settled on is comparatively affordable.

My friend Robin Wyatt, who spent his formative years in Britain, has owned many, many stereo systems. Some included Quad ESL-57s. A year ago, his living room was fitted with some giant pairs of loudspeakers and lots and lots of associated equipment.

Then, he came to listen to my Quads. Within days he bought a pair for himself and started selling nearly all the other gear. Robin puts it this way: “The classic Quad speakers are limitless in their transparency and their ability to resolve what is put in front of them.” That means the speakers are as good as the associated equipment you use with them. A good amplifier makes them sound good and a terrific amp lets them sound terrific.

It's all about the amp
That’s why Robin settled on the amazing ASR Emitter I Exclusiv Blue amplifier. I must agree that the ASR and his Quads are an incredible synergistic match. They reproduce music that sounds amazingly real. It should: Robin’s ASR sports a suggested retail price of $17,000. That is way out of my reach.

Luckily, I’ve found something nearly as good. As I’ve told you before, I bought a set of old Quad electronic gear way before I found a good pair of Quad speakers. I’ve auditioned these Quad amps on many systems with pleasing results.

The Quad model 33 control or pre-amplifier and the model 303 power amplifier were the company’s first transistor amps. In the late 60’s their design and looks were startling and their sound was very good. To this day, you can find a set in good condition and they still sound good.  But four decades of technical advances have left this old Quad gear behind, somewhat.

That’s why I contacted David Pritchard, proprietor of a small British company called Net Audio. David makes a number of special hi-fi items including upgrades for older Quad transistor equipment. Net Audio can sell you the new circuit boards, specific parts along with instructions or, if you prefer, will do the upgrades for you.

There are all different levels and combinations of improvements you can make. For the 33 preamp you can change some or most of the plug-in boards. You can also solder a new power supply board into your 303 power amplifier – or change nearly everything inside and out — from circuits, capacitors and output transistors to the faceplate and on/off switch. After months of testing on multiple Quads 33s and 303s I believe Net Audio is on the right track.

Upgrading for better sound
I upgraded a 33 preamp by myself. The most difficult part was locating a screwdriver buried under all the stuff on my test bench. I went for the full upgrade: replacing the two main audio output boards, the tape board and the disc amplifier (for LPs) for a total of £156 U.K.  David made sure my upgraded boards included optional, “maximum performance” OPA627AP opamps (miniature amplifier circuitry). The full pre-amp mod also requires a separate, external, plug-in AC power supply. David can suggest a U.S. alternative (120V) to the U.K. version (220V) he lists on his Website.

Updating the 303 power amp was a different story. I changed one of my 303s with a Net Audio power supply board (£50 U.K.). It was easy. But, if you’ve ever seen me wielding a soldering iron you know I shouldn’t try tackling a big job. That’s why I sent my second 303 to Net Audio for a complete overhaul.  He charges £220 U.K. plus shipping.

I wish I could invite all of you to hear how good my hi-fi sounds now. The Net Audio 33 preamp is just plain amazing. Clear, clean and accurate. David has actually improved upon what Quad created 40 years ago by bringing the circuitry into the 21st century. He was even able to get the old Quad’s disc circuitry to excel using a modern-day moving-coil cartridge (a Reson Aciore sounds fantastic). Overall, to my ears, David's new 33 is one of the best sounding preamplifiers I’ve ever auditioned. 

I also spent a long time listening to both of the modified 303s.  More about that in a minute. First, the power supply-only modded amp. That one had previously been brought up to spec by QS&D, Quad’s U.S. repair agents before I changed anything. 

I was able to swap-out the original 303 power supply board for the Net Audio replacement. It required un-soldering four wires from the old board and re-soldered them to the new. (For the record, Robin supervised). Total upgrade time was less than five minutes.

The second amp I sent off to David. He performed all the upgraded as listed on his Website and sent it back. Total turnaround time was less than two weeks.

After many extended auditioning sessions I must report that both amps sound great. Different, but great. I agree with David that the simple power supply upgrade is probably the most essential to bring the 303’s sound up to date. The amp with this single board swap is probably one of the best audio bargains on the planet today. It improves upon the 303’s inherent musical qualities and creates an amazingly terrific sounding amp.

The fully modified 303 sounds even more up-to-date and modern.  It greatly improves upon the 303’s high frequency reproduction while maintaining its other good qualities.  After a few months of constant break-in and use, I can happily report that Net Audio’s modifications have been safe and, as far as I can tell, electronically stable.

Here is my recommendation: go for the full upgrade on the 33.  As for the 303, without hesitation, you owe it to yourself to upgrade the power supply board. Do so now.  It makes a huge difference. On the other hand, if you can afford it, the full upgrade will reward you with a detailed, terrific sounding amp.

The value of the dollar is low (when compared to the U.K. pound) so these upgrades are more expensive than they were when I first started on this quest. I figure I spent a little over $1,000 for the modified amplifiers, not including the cost of shipping, which is very reasonable in today's marketplace.

Any way you look at them, the Net Audio upgrades are a comparative bargain. Very, very highly recommended. And music to my ears.