Pertaining to the Aengus EQ thread elsewhere here, in London we used the APSI version of this switched graphic unit, the 559. I don’t think I ever saw an Aengus one, although I knew of them. And yes, very good on drums.
The APSI 559 had an extra band, (hence the 9), and used multiple feedback tuned circuits as opposed to the Aengus gyrators. These MFBs could have come straight from the Don Lancaster book, Active Filter Cookbook, p.153. I use the phrase “tuned circuits” because filters means something quite different in Audioland, as we know.
APSI also did an AE version with the Aengus frequencies instead, whilst keeping the 16K. Thus with one (or two) of each, you could get to pretty much wherever you wanted.
The circuit is quite simple and has the odd and even switches set around the 2 inverting pass amps to minimise interaction. The switches were custom from Cherry as I recall. Transformer is a dedicated 1:2 JE-123 size, but the ones I have are not Jensen. For DIY use, the UTM3505 will suffice. Also, from a homebrew standpoint, you could have 4 pass amps and have both APSI and Aengus frequencies across a 1U unit. Bit tight on the rotary switch spacing, though.
I’ve put the documentation I have in the Technical Documents, but has anyone got the 562 schematic?
The APSI 559 had an extra band, (hence the 9), and used multiple feedback tuned circuits as opposed to the Aengus gyrators. These MFBs could have come straight from the Don Lancaster book, Active Filter Cookbook, p.153. I use the phrase “tuned circuits” because filters means something quite different in Audioland, as we know.
APSI also did an AE version with the Aengus frequencies instead, whilst keeping the 16K. Thus with one (or two) of each, you could get to pretty much wherever you wanted.
The circuit is quite simple and has the odd and even switches set around the 2 inverting pass amps to minimise interaction. The switches were custom from Cherry as I recall. Transformer is a dedicated 1:2 JE-123 size, but the ones I have are not Jensen. For DIY use, the UTM3505 will suffice. Also, from a homebrew standpoint, you could have 4 pass amps and have both APSI and Aengus frequencies across a 1U unit. Bit tight on the rotary switch spacing, though.
I’ve put the documentation I have in the Technical Documents, but has anyone got the 562 schematic?
