[EdHolland]

Meanwhile, 10 KOhm pots arrived over the weekend, so I can begin construction of the IBAM circuitry. I did note the alternative Bias-balance adjustment, said to be a little easier to tweak, and wondered about implementing it. It was claimed that at least one design eliminated the risk of failure of bias supply, should one of the pots lose wiper contact. A couple of things put me off. First, I could not find a schematic, second, it was noted that the bias voltage range was limited, and not necessarily sufficient for all replacement 7591 valves.

Pondering a little more, it seems that with the addition of one extra resistor, one might be able to configure a fail-safe IBAM, but I want to sketch something out and run the numbers to be sure. I'll write up here if it looks like there is any progress on that.

Cheers

Ed