Folks, here’s another ADCOM GFA-535 II for sale! This one is in MINT condition. Not a scratch on it, and I’ve installed a freshly powder-coated top cover! It’s gorgeous. If you love the Adcom GFA-535, this is the one for you.
As with all the amps I sell, this unit has been completely torn down, rebuilt, refurbished, and obsessed over. This amp not only sounds better than new, but I intend it to last another 30 years or more! I go way beyond a simple re-cap. Any and all parts that may potentially deteriorate have been replaced, and I’ve paid a lot more attention to detail than the factory with things like wiring and matching components. Every component is checked, and every solder joint shines.
And this one has a little special something. A powder coated top cover! (I got a deal on getting a bunch of covers done.)
Isn’t it beautiful? The powder-coat finish is major overkill, and much more abrasion-resistant than the factory finish.
- All electrolytic caps replaced: Power supply filters upgraded to 4x 10,000uF Cornell Dubilier 380LX, bypassed with WIMA MKP 0.1uF. Nichicon Fine-Gold audio-grade capacitors used in signal paths, and Panasonic FC bypassed with WIMA MKP for output stage local supply bypass.
- Carefully matched pairs of transistors are installed in the critical input stage. (Fairchild KSC1845) This step is important to assure low DC offset at the output, and low distortion. The stock transistors are rarely well-matched, especially on later models. (It’s labor-intensive to find really tightly matching pairs. I built a matching jig that simulates their operating conditions.)
These transistors must be perfectly balanced, or the sound of the whole amplifier is compromised.
- Output transistors are checked for good matching and replaced if necessary. (I did swap out one marginal pair in this amp.)
- Bias transistor is replaced with a physically larger 2sa1381. (Stock to-92 transistor runs very hot and burns the board eventually.)
- Input capacitors changed to WIMA MKS4 1uF 400V
- Emitter resistors changed from 5% tolerance sand-cast types to DALE LVR 1%. These are more reliable, and frankly, prettier.
- Sealed Bournes trim-pot installed for precise bias adjustment and better reliability.
- High-current bridge rectifiers are installed and heat-sinks attached. This helps prevents power supply droop while the amp is being run hard. The original bridges are known to fail if the amp is over-driven for too long.
- X2-type snubber capacitors installed across AC side of bridge rectifiers.
- New power switch and spark-suppression capacitor.
- New surge-protection MOV.
- Circuit boards are cleaned and solder joints inspected and touched-up wherever needed.
- Wire-wrap transformer connections removed and soldered permanently.
- All wiring meticulously and obsessively routed, twisted, braided and neatened.
- New 30A binding posts (Pomona 6883)
- New 14ga power cable with strain relief and heavy-duty plug
The final steps are to torture-test, set bias and do listening tests. The amp is run into a dummy load, and power output readings near clipping are recorded. (Approximately 80WPC into 8 ohms.) The amp is driven hard for 30 minutes, allowing it to heat up, and it should show no signs of distress. It should cool itself down in a reasonable time, and the bias should remain steady throughout the temperature range.
I measured 89WPC into 8ohms just before clipping, and 128WPC into 4 ohms.
I’ve been listening to this amp through my JBL 4208 near-field monitors for a couple of days now, and it sounds excellent as expected.
Cosmetics: Mint! In a former life, this amp was running surround speakers in a permanently installed home theater system, somewhere in Minneapolis.
It has a freshly powder-coated top cover, which is gorgeous. (The original cover had one scratch on it, and I couldn’t stand it not being 100% mint, so replaced it.
Please click on the pictures to see it in hi-rez, and judge for yourself.
I stand behind what I sell, and my intention is that you have a great sounding amp that lasts a long, long time.
Contact me here if you’re interested!