02-03-2018, 06:58 AM
Thanks Mark. Yes I've been careful of where I put probes, mains earth referenced scope probes are a pain in the article sometimes. The PSU is a tfmr, two big caps/RC filter and zener shunt regulated, it's floating.
I've also had to put a de-coupling cap on the IP to stop DC getting into the sig source, I've used a 100n. I'm using a HP3770B telephone line checker as the sweep. It goes from 200hz to 19.9khz in 160hz steps. Am monitoring the OP with a B&K valve AC voltmeter which has the meter in dB as well as RMS/Peak etc. I did try using REW a PC based speaker/room EQ "app" on PC which has a sweep/frequency response graph, but the sweep is modulated. not sure if this is intentional or a glich. REW is very fiddly to set up and calibrate, the soundcard and "app" controls are very touchy. It's OTT for this anyway.
CCS I is set to 5mA as I used an 18k R as reference and also bearing in mind what you said about the need for a CCS at all. I got a few high voltage Q's off line luckily before the weather got bad, EG TO92 Darlington's, Mosfet's and a few MPSA-42's to play with.I already had some HV Depletion mode Mosfets whose designation escapes me at present LND something I think. This will enable me to knock up ring of two's etc and keep within the SOA, so hopefully no bangs and smoke.
Thanks again Mark, A.
I've also had to put a de-coupling cap on the IP to stop DC getting into the sig source, I've used a 100n. I'm using a HP3770B telephone line checker as the sweep. It goes from 200hz to 19.9khz in 160hz steps. Am monitoring the OP with a B&K valve AC voltmeter which has the meter in dB as well as RMS/Peak etc. I did try using REW a PC based speaker/room EQ "app" on PC which has a sweep/frequency response graph, but the sweep is modulated. not sure if this is intentional or a glich. REW is very fiddly to set up and calibrate, the soundcard and "app" controls are very touchy. It's OTT for this anyway.
CCS I is set to 5mA as I used an 18k R as reference and also bearing in mind what you said about the need for a CCS at all. I got a few high voltage Q's off line luckily before the weather got bad, EG TO92 Darlington's, Mosfet's and a few MPSA-42's to play with.I already had some HV Depletion mode Mosfets whose designation escapes me at present LND something I think. This will enable me to knock up ring of two's etc and keep within the SOA, so hopefully no bangs and smoke.
Thanks again Mark, A.
