Author Topic: H11F1 observations  (Read 11239 times)

Beo

Re: H11F1 observations
« Reply #20 on: February 24, 2014, 04:19:26 PM »
Question: Why didn't you set it up so that the muted position turned off the internal LED instead of trying to dump signal to ground? That would stick 300M in series with the signal. Your guitar's pickups won't make a peep through that. That's the method used for optical bypass switching, also.

From my research, the optimal mute is to have both an in-series FET and a shunt to ground FET, triggered with inverse signals. I wanted to optimize a shunt to ground and avoid having the fet in the unmuted signal first, and see how silent I could get. A lot of the posts on this site seem to encourage that a shunt to ground can get really silent on its own. What I've found is that I can get the relay switching down to a soft click, but the shunt to ground mute is causing a transient about the same volume (so I get my 20 msec mute to block the relay click, but engaging the mute is giving me its own click). I'll try the optoFET in series and see how that goes, but TB snobs would scorn having the FET always in the signal path. (I'm not adverse to this for my own pedal switching but some pedals I build for friends come with silent TB requests).

Beo

Re: H11F1 observations
« Reply #21 on: February 24, 2014, 08:44:16 PM »
So I've been reading up on DC Blocking / AC Coupling capacitors. At a circuit input, these are usually biased (often to center of power supply) before going into the rest of the circuit. At a circuit output, these are usually at the very end of the chain or just before any output level adjusting resistors or volume pot. What this tells me is that an output capacitor charges up to the DC Level, holds that DC level and only allows any AC through on top of this DC level.

So, when I'm shunting to ground, even though I've DC blocked the signal, I'm still dropping quickly from some DC level to ground. If I can't "slow down" this transition to ground to get a quiet mute, could I shunt to the DC level (maybe charge some other capacitor to the DC level and shunt to this)?

Thanks
Travis

Beo

Re: H11F1 observations
« Reply #22 on: March 29, 2014, 12:15:34 AM »
For posterity sake, here's the solution to the issues I was having.

For the H11F1 shunt, I needed a bigger capacitor to slow down the LED... 47uF is what I'm using. I'm lighting the opto bright using a 1k led resistor. I have 10k in series resistor before the H11F1 (maybe this maybe could go down to 4.7k, definitely some clicks if I don't have a series R). And finally, my mute timing on my AVR was too tight, I was using 5ms mute before relay trigger and 10ms mute after... when I bumped this to 25ms mute before and 25ms mute after, this did the trick (50ms total mute).