How to Bypass electrolytic caps

The type of cap you select to bypass is also key. Poster Spectron made the comment that the bypasses cleaned the highs, but did not help with the dryness. He is correct, the life of the music is in lower frequencies. If you bypass with very small value caps, you will end up with that very detailed upper end, but in long term listening, becomes boring or worse, fatiguing. Stay away from the teflon and polyprop caps of small values. You need a larger value. I'd suggest you visit the mouser web site and order an assortment of film and foil caps of a high enough voltage rating (check the voltage on the filter caps) and do some experimenting. You'll find the voice of the amp or pre amp changes drastically as these bypass cap values are changed.

The larger values will help the midrange. Using a bunch of small value caps to clean up the upper frequencies can easily be over done.

good luck.

I have no knowledge of what Spectral has been doing in recent years, but I recall back in the 1980's that their designs tended to be of the "dc to light" school, meaning ultra-wide bandwidth. If your amp is like that, it would mean that it would let through any ultra-sonic garbage that may be present at its inputs, that most other amps would filter out. That in turn could conceivably intermodulate with lower frequencies, producing audible results.

So if you happen to be considering a preamp upgrade at some point, you might want to select one with relatively limited bandwidth, perhaps a tube design.

Just a thought.

Regards,
-- Al

"i am exploring using some film caps to bypass these to cope with the inherent dryness of the amp."

You can't. Its dry. At best you will,extend and clean the highs a bit. "life" is not in the highs.

Sell this terrble creature. My ears were bleading every time I heard "it"

Buy normal amp, buy good amp. Buy Nelson Pass if you like solid state, buy Joule-Electra - tube OTL amps (well, its depend if your speaker's impedance dip low, of course).

Buy cheaper Parasound JC-1 or new Bel Canto Ref1000 Mk2 for solid state (something new and excellent!!!!) and... Mcintosh 275 for tube or BAT or ... something

Entire world is open for you. You cannot do anything with, and I quote "inherent dryness". I been on live concerts, once or twice in my long life - no dryness there. NONE!

Good Luck

Another suggestion that I learned while upgrading my amp some years ago. The bypass should be physically closer to the transistors in the amp. Technically the electrolytics are powering the transistors. So a small value film cap would do more good closer to the transistor than just where the electrolytic connects to its board.

However, there can be too much of a good thing here. You may not want to bypass every transistor since that could tilt the balance of the amp too much to the top end. You also want to voice the bypass differently depending on the type of electrolytic used. For example the JC1 uses Nichicon Gold electrolytics, and a Relcap RT as its bypass at the end of the rail (this per Bob Crump who voiced that amp for John Curl).

Disclaimer: Please consult an engineer about the viability of doing this in your amp, and I make no claims to knowing anything about MOSFET based circuits.

Enjoy,
Bob

Bypassing in this case means simply wiring the film caps in parallel with the electrolytics. Connect one end of a film cap to one terminal of an electrolytic, and the other end of the film cap to the other terminal of the electrolytic. When I say "to one terminal of the electrolytic" I mean connect either directly to the terminal, or to a nearby circuit point that is in turn wired to the terminal (whichever is physically most convenient).

Electrolytics often have multiple capacitors enclosed in a single housing, so you would have to connect a film cap for each section. You will probably find that one side of each of those multiple capacitor sections is common to all the sections, while the other sides of the sections are present on separate terminals that are wired individually.

I assume the film caps would be non-polarized, so either end of those caps could be connected to either end of the electrolytics. Electrolytics themselves are usually polarized, with one end defined as positive and the other as negative, but that does not affect what you want to do as long as the film caps are non-polarized.

The basic point to "bypassing" is that the film caps provide better performance at high frequencies, so they will be more effective at filtering noise. The electrolytics, having larger capacitance values, are mainly effective for filtering low frequency ripple (corresponding to the power line frequency and its harmonics), and for providing energy storage that can maintain the power supply output voltages through brief peaks in output demand or brief drops in input voltage.

The film caps that you choose should be rated to handle voltages that are at least as high as what the electrolytics are rated for, and preferably higher.

I have no idea whether or not the film caps will improve the dryness you have noted.

Regards,
-- Al