Sorry - forgot hit Reply.
The first letter is the gain range - Hfe. I remember looking up both the 547 & 557 data and choosing the B range. As long as you get both in the same range, you should be fine. I don’t recall if there was a big measured difference between the complimentary pairs (Q2 & Q3) when I built mine, but I think R14 & R15 on the emitters help balance the output stage.
I think they spec a 50k log pot.
I don’t really know anything about these. What does the all in cost end up being? Approximately
I had a lot of the parts in stock, but I’m guessing I’ve spent around $60 plus the cost for the board. It depends on which op amps and pot you choose. You’ll need some RCAs, power connections and a fuse. If you can build your own chassis, you can probably keep it under $100.
Trying to put together a build sheet and then I should know the out the door price.
Does this look right? Have the trans, rca jacks, wire and jack, etc. included in the parts list. Leave them out if you don’t need them. Mouser doesn’t seem to have the best parts selection right now, but wanting to get everything from one place.
Cost for everything is ~$130.
beeny pre parts list Doc1.docx (701.6 KB)
I haven’t compared the LME to the 5532 listening to music yet. I still need to mount the boards in the chassis and need to make some decisions about switching and remote control. But it’s interesting that this interesting read showed up in my FB feed today - https://www.headphonesty.com/2026/03/vintage-op-amp-embarrassed-modern-phono-chips/
High second order distortion FTW… again.
No new updates from Michael. I’ve been researching the logic aspect for IR control. I’ll use an Arduino Mini or Nano clone or ESP32. I had hoped to use the input switching IC from the old Acurus, a TC4066, but I don’t understand how they implemented it. I found a ULN2803 chip that will control most standard relays to select the inputs. It’s cheap as chips, but I’m still looking for a SS option so I can omit the relay board entirely.
I have another project brewing in tandem, a speaker/amp switcher. That will use the same basic building blocks as the preamp, but will have 8 relays and hopefully some kind of display. I’m currently looking at options for simple serial data control for the relays via a shift register chip, the 74HC595. That will reduce the pin count needed out of the microcontroller. If anyone has experience with these types of devices, please feel free to chime in because using a data packet to control something else is completely new to me.
