***NOTE: EACH AMP WILL BE INDIVIDUALLY DOUBLE-BOXED AND HEAVILY PADDED FOR SECURE SHIPPING *** Up for bid is a wonderful pair of Pass Aleph 60 monoblock clone amplifiers. These amps each provide 60 watts of Class A power. The Aleph 60 is the monoblock version of the famous stereo Aleph 5. The Aleph sound is known for fabulous air and space, liquid mids, authoritative bass, and shimmering highs - tube-like solid state. The amps are only 8 months young and now properly burned in. If you've not heard Pass Labs Aleph Series, here is a chance to do so with a modern pair of monoblocks that are hand matched and built with the finest parts. For the engineers and discriminating audiophiles among you, the following demonstrates the exceptional quality of these amplifiers and fidelity to the Pass Aleph build: The amps use a CRCRC power supply, shielded Antek toroids, and rectifier snubbers or a stiff and quiet power supply. The active parts are precision-matched Vishay current source and output MOSFETs, and precision-matched Harris/Fairchild input stage MOSFETs. The amp boards use top-tier Elna Silmic II capacitors bypassed with Wima film caps. The amps were burned in and calibrated for bias, gain, and offset. Balanced (XLR) and Single-Ended (RCA) Inputs. These Class A amps run hot by design, so they must be placed where they have plenty of ventilation. The amp stays true to the Aleph recipe with a few enhancements. The PCBs were designed based on the Aleph 30 and 60 schematics. They can be used to make the other MOSFET-based 2 gain stage Aleph variants (Aleph 3, Aleph 2, Aleph 5, Aleph 1.2). A few enhancements were added to the design: · Added film bypass caps to the 220uF caps in the circuit · Added pot to adjust Aleph Current to precisely 50% · Added pot to adjust DC Offset (in reality, don’t need it based on MOSFET matching, more below) · Added pot to adjust overall amp bias current. · Enhancements that Nelson called out on the “Aleph Design Reloaded” thread. https://www.diyaudio.com/community/threads/the-aleph-design-reloaded.267857/ For complete schematic detail, go to the “Classic Aleph” builder’s thread. The Aleph 60 build document is in post #1, and it shows all of the detailed schematics (original and this amp) and build details. https://www.diyaudio.com/community/threads/classic-aleph-amplifier-for-modern-ums-chassis-builders-thread.382316/ The power MOSFETs came from a pool of over 1000 for matching. This results in the 12 MOSFETs for each channel being matched within less than 5mV (extremely close). For context, Nelson has stated that within 0.1V (100mV) is good enough. 100mV is good, <5mV is great. The input stage MOSFETs are Nelson’s favorite Harris/Fairchild SFP9610. These came from a pool of 850 for matching. Most amps I have built or parts kits I have sold have the 6 required MOSFETs for 2 channels within 1mV across the 6. This results in very good output DC Offset performance. The original Aleph 60 has a 120,000 uf cap bank for the power supply filter, 60,000uF for the positive power supply rail, and 60,000uF for the negative power supply rail. It is a single cap bank without an additional filter stage. This build uses a CRCRC filter cap bank with a total of 176,000uF of capacitance. 44kuF per rail, then parallel 5W power resistors, 22kuF, then parallel 5W power resistors, and final 22kuF caps. This results in lower ripple voltage due to additional capacitance AND 2 filter stages. For context, the standard First Watt amps use a CRC power supply, and this build adds an additional filter stage. Dead silence is the design goal. Adding additional capacitance and using 2 RC stages in the power supply dropped the power supply ripple to very low levels. This build uses 400VA Antek transformers with a cover. The reason for this is the 400VA is the largest offering by Antek to use an integrated shield in the transformer, and the 400VA is the largest transformer cover they offer. This choice drops the noise floor as low as possible. The rectifier bridges use a snubber circuit that damps out ringing between the transformer and the rectifiers. This is one additional way to minimize power supply noise and lower the amplifier’s noise floor. Read all about the snubber concept here: https://www.diyaudio.com/community/threads/simple-no-math-transformer-snubber-using-quasimodo-test-jig.243100/ Thanks for looking and ENJOY THE MUSIC!