Pass Aleph 3 clone build and performance. 30W Class A Amplifier.

In this video, I review a Pass Aleph 3 amplifier board that I purchased on eBay. The Aleph 3 is a 30W Class A amplifier sold approximately 25 years ago (1997). Initial tests of performance and build are performed.
Purchased these boards on eBay for approximately $45 for the pair.
I plan on building a complete amplifier chassis with quite a bit of attention spent on thermal management.
Questions? Let me know.
Items used in this video can be purchased from Amazon. All items in this video were personally purchased. As an Amazon Associate I earn from qualifying purchases.
Rigol DP832 Power Supply: amzn.to/3YSqoii

[@AlanFenick]

Remember buying a Threshold Class A amplifier in 1978! Purchased it from Sound Components in Coral Gables. It was an incredible amp for my Chartwell LS3/5a’s which were 15ohm impedance. The amp got quite hot, but the sound was incredible and worth every cent it cost. Mr. Pass designs were always good sounding and well thought out. I would love to have an amp made with 30 watts per channel to drive my old QUAD ESL’s sitting well packed in the basement. At $40.00 it would be an incredible value for a Nelson Pass designed amplifier. For a couple hundred dollars for a power supply and chassis and fans it still would be a bargain. I just purchased two FOSI V3 mono block amps from Kickstarter with two 48volt 10amp power supplies for the Class D amps as a funding reward.

[@DanPattenAudioG33k]

Have always been a fan of Pass going back to the Threshold days. Also liked that many of his designs had schematics available.

[@SheikhN-bible-syndrome]

I've got a clone hood 1969 that uses 3 5200 transistors and I paid 19$ for it it sounds pretty good especially for the price

[@joshaas]

Hi first off all a nice video, i am building the same Aleph 3 clone, but i like to bring it more to Neson Pass original, so i did change the bc550 to the mpsa18, be aware you have to turn them around on the pcb, and nou i am thinking about the irfp250n on there, Nelson did use irf244 so i do not have these on hand, but i have the next best thing that are the irfp240, they have almost the same specs as the irf244 so maybe i do install them, and i did change the capacitors to Panasonic FC so more real audio caps

[@DanPattenAudioG33k]

I am working on a part 2 video. Changing the current source resistors increased output power. I am working on a heatsink solution and hope to have a rough prototype in a couple of weeks. Thanks for the kind comments.

[@rayc1557]

Cool stuff, Dan. Really enjoy your videos. I happen to have a similar addiction but mine evolves around Class-A headphone amps with built-in (gyrator-based) equalizers. I bet you don't know too many people whose headphone amps pull 15W out of the wall. Q: What model AP analyzer do you have there?

[@DanPattenAudioG33k]

Thanks. Sounds interesting and I am not familiar with gyrator equalizers. Had to look it up :) I have designed a few Class A amps but not exclusively for headphones. I am slowly working on a headphone design that is a magnetic planar type. Just do not have enough time. The Audio Precision instrument is an old Portable One Plus (P1+). Bought it about 25 years ago and it has been a real workhorse. Dread the day that it finally kicks the bucket.

[@rayc1557]

@@DanPattenAudioG33k Well Dan, if the AP bites the dust, it will be time to learn how to take one apart and fix it. Man, I was looking at new model$ and they are expen$ive. Be well and happy New Year. I hope all your projects are fun and successful.

[@gp1528]

Nice project, thank you for sharing more details. The input mosfet looks like Fu9210. I was thinking no more available in the online store. aleph 3 circuit recommend IRF9610. Do you think any benefit from Fu9210! Did you measure the heat dissipation. I would like to see more videos.

[@DanPattenAudioG33k]

Thanks. The input FET is an IRFU9210 and it looks like Digikey has stock on that item. Have not looked at the differences between the IRF9610 and IRFU9210 yet. I have done some preliminary tests with a 0.33ohm (instead of the 0.47ohm) and I did realize about 25% more current and was able to drive a 8 ohm load to max voltage. I will do another video detailing my power supply and bias changes.

[@hashtag-shaneiacs]

The specifications are great. How did it sound from speakers? 13:02

[@DanPattenAudioG33k]

Have not listened to it yet :) Need to get it a little more put together first. Possibly in another couple of weeks.

[@user-xh2qi7tn2l]

про Pass Aleph 3. Усилитель класса А