Thanks, I will try that.
How does one calculate the values for the zobel? Is it partly down to trial an error?
Hi!
Try simple resistive loading first. Soundwise you might prefer the unloaded secondary
Thomas
Try simple resistive loading first. Soundwise you might prefer the unloaded secondary
Thomas
Try with a 5K multitrim and 3.3nF as starting point, or only with the trimmer, as Thomas said, and see what you like. Then change to a fixed resistor.
Thanks Thomas, Loaded it with 10K and it is certainly looking better. Will hunt down the remaining hum issues and lug it back to the house for listening.
You can check the ringing by doing a frequency sweep with a signal generator and watch the frequency were the output increases. Usually about 50kHz with ll1660 if I remember correctly.
Mine LL1660 ringing 51KHz, measured the trimmer and reads 627 ohms but I only have on hand 604R Welwyn or 681R Vishay S102K wich one to use?
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I experimented with Intact Audio autoformers on output but I prefer step attenuator with resistor ladder configured.
Yes, my 26 preamp uses the Bent as the output "transformer" and as the volume control, laminations stacked 3x3 for ~150H primary inductance. I also use a Lundahl LL1676 2:1 step-down on the input through which I apply battery bias, so no need for an input cap, and the cathode is directly grounded. Output from the 26 is taken from the mu output of the plate CCS, so impedance is plenty low enough to drive the Bent. Details including frequency response at different volume settings are in this thread a few months ago.
It sounds excellent.
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Merlin,
Have you tried LL2745 for your 26 preamp?
With 5.6:1 step down, lower output impedence will better match with your low impedence AVC.
Cheah