Krell has produced some stunning gear over the years and this Krell PAM-7 is a great example. Come with me as I repair and overhaul this lovely old girl.
The Krell PAM-7 preamplifier dates back to earliest days of Krell, but all the trademark features are present: thick boards, premium parts, class-A operation, separate power supply and the unique styling the company used back in the day.
I particularly like the industrial grey brushed aluminium finish. Nothing else looks like older Krell gear and certainly, the mechanical and electronic build quality is extraordinary, even now.
Sonically, this unit gives nothing away next to the most expensive modern preamps. There are no new circuits and parts in 2019 that these guys didn’t understand and have access to in the ’80s.
This unit has all the best features: premium switches and pots, zero wiring, FETs, lots of local capacitance, discrete & configurable phono preamp, multiple regulated power supplies, class-A, all discrete circuitry, and on it goes.
Krell still has the owner’s manual available and the excellent staff in the Krell service centre are always kind enough to assist me with what data they have available – thanks, Patrick!
This unit exhibited several issues and she had never been in for service until she came to me. Signals from the PAM-7 showed distortion and gain was low in one channel. Strange noises emanated from the phono preamp and it turned out that one of the 15V rails was sitting down at around 5V.
A couple of the on-board (as opposed to external) power supply capacitors looked suspicious and didn’t measure well. Obviously, the unit needed repair and at least some basic maintenance. Despite the impeccable service life and fantastic performance of this wonderful preamp, it took some convincing her owner that this was a worthwhile repair. He really didn’t want to spend any money on it.
First steps were to assess the unit and diagnose what was wrong. I traced the noises, distortion and low gain to a bad Zener diode voltage reference which sets one of the power supply rails. This failed diode caused that rail to fail, and the now asymmetrical rails caused the sonic problems in the form of distortion the owner and I heard.
Attending to all the little details that make something really look and feel like it’s had proper service is part of the value add that I provide for my customers. In this case, that meant a full clean of all panels, fascia, knobs, cleaning and treatment of connectors and lubrication of all switches and controls.
This repair and overhaul were critically important for this PAM-7. Without them, I suspect she might have been tossed out, or taken to a butcher.
Folks occasionally struggle with the idea that you need to periodically spend some money to have an expert look at beautiful equipment, like this. It’s fair to say the owner fell into this category.
This isn’t like taking a digital watch to a mall vendor to get a new battery. It’s much more like taking a Rolex to a good jeweller for its regular service, surely worth doing properly, right?! Remember, even Krell doesn’t make anything like this any more.
I think the results speak for themselves. The unit now sounds better than ever. Her sonic behaviour is perfect and she sounds sublime, especially via that stunning, adjustable phono preamp. If only all hi-fi equipment was this beautifully constructed.
When I explained to her owner that to replace the PAM-7 with a modern ‘equivalent’ with similar sound quality and likely cheaper build one would need to spend well over $5000 AUD, I think it began to sink in.
For example, you could buy a lovely Bryston BP6 for $5500, but that’s not really in the PAM-7’s league. How about a Musical Fidelity M8 for $6999 – do you imagine that this might sound better? Looking at the M8’s internals, I can guarantee it won’t.
So what can we learn from all this? Hopefully, you can see that humans could build this stuff perfectly, decades ago. Newer doesn’t mean better and in fact, it often means the opposite. Most of all, I hope it shows that spending just a few hundred dollars to have your beautiful old equipment professionally serviced, is some of the most sensible money you can spend.
If you would like me to look at your lovely vintage Krell equipment, you need only get in touch!