Search found 11526 matches

by Nick
Fri Feb 15, 2019 5:18 pm
Forum: Everyones Projects
Topic: Warning LED when valve stops conducting - a little SS help needed
Replies: 102
Views: 665

Re: Warning LED when valve stops conducting - a little SS help needed

I would expect the bridge to impact the sound, but should be easy to prove
Bet it wont be easy to "prove" given that you expect it will :-)
by Nick
Fri Feb 15, 2019 5:00 pm
Forum: Everyones Projects
Topic: Warning LED when valve stops conducting - a little SS help needed
Replies: 102
Views: 665

Re: Warning LED when valve stops conducting - a little SS help needed

No external power, so the led lights IF the difference between the voltages at the ends of the resistors differs by more than 3 diode drops plus the drop over the current limiting resistor. Interesting, but wouldn't that be directly in the music path ? Yep, thats it, throw a cap across it of you li...
by Nick
Fri Feb 15, 2019 3:39 pm
Forum: Everyones Projects
Topic: Warning LED when valve stops conducting - a little SS help needed
Replies: 102
Views: 665

Re: Warning LED when valve stops conducting - a little SS help needed

You could try a LED inside a bridge rectifier. ok quick bit of googling and ... Capture.PNG Is that something like what you had in mind ? No, literally a LED inside a bridge rectifier. Rectifier with ac terminal one to each resistor cathode, LED with dropper resistor between the bridge + and - term...
by Nick
Fri Feb 15, 2019 1:35 pm
Forum: Everyones Projects
Topic: Warning LED when valve stops conducting - a little SS help needed
Replies: 102
Views: 665

Re: Warning LED when valve stops conducting - a little SS help needed

You could try a LED inside a bridge rectifier.
by Nick
Fri Feb 15, 2019 11:49 am
Forum: Everyones Projects
Topic: Warning LED when valve stops conducting - a little SS help needed
Replies: 102
Views: 665

Re: Warning LED when valve stops conducting - a little SS help needed

Yes, you are trying to detect when the two currents are different, you have two equal resistors, one in each current with a common tail, if the currents are different, the voltage at the top of each resistor will be different.
by Nick
Fri Feb 15, 2019 10:11 am
Forum: Everyones Projects
Topic: Warning LED when valve stops conducting - a little SS help needed
Replies: 102
Views: 665

Re: Warning LED when valve stops conducting - a little SS help needed

RhythMick wrote:
Fri Feb 15, 2019 9:22 am
Or combine the outputs in a NOR. Single led lights if either of the comparator outputs goes low, but not both.
In that case you may as well just compare the voltages on the top of the to sense resistors. What is unknown is will it trigger with a audio signal.
by Nick
Fri Feb 15, 2019 8:56 am
Forum: Everyones Projects
Topic: Warning LED when valve stops conducting - a little SS help needed
Replies: 102
Views: 665

Re: Warning LED when valve stops conducting - a little SS help needed

It would light the LED's when you turn the amp off.
by Nick
Thu Feb 14, 2019 5:00 pm
Forum: Everyones Projects
Topic: Warning LED when valve stops conducting - a little SS help needed
Replies: 102
Views: 665

Re: Warning LED when valve stops conducting - a little SS help needed

RhythMick wrote:
Thu Feb 14, 2019 4:37 pm

Isolated means the output is floating, right ? So I can ground to the top of the cathode resistor per the diagram. I know that's obvious, just checking my terminology.
Well, you can connect to the cathode resistor without grounding anything which I think is what you are asking.
by Nick
Wed Feb 13, 2019 11:45 pm
Forum: Everyones Projects
Topic: Warning LED when valve stops conducting - a little SS help needed
Replies: 102
Views: 665

Re: Warning LED when valve stops conducting - a little SS help needed

These sort of isolated supplies can be great for providing a floating supply from a existing DC supply.

https://uk.rs-online.com/web/p/isolated ... s/3965174/
by Nick
Wed Feb 13, 2019 3:14 pm
Forum: Everyones Projects
Topic: Niobium - Valve pre for SS Power Amp
Replies: 48
Views: 3725

Re: Niobium - Valve pre for SS Power Amp

The electrostatic screen is to prevent capacitive coupling between the primary and secondary. Doesn't affect hum field.

Just try rotating one of the transformers and see if the hum changes.

Is it hum (50Hz) or does it have edges? (100Hz+charging)
by Nick
Wed Feb 13, 2019 3:11 pm
Forum: Everyones Projects
Topic: Warning LED when valve stops conducting - a little SS help needed
Replies: 102
Views: 665

Re: Warning LED when valve stops conducting - a little SS help needed

RhythMick wrote:
Wed Feb 13, 2019 2:30 pm
Nick wrote:
Wed Feb 13, 2019 2:24 pm
Transistors never fully turn off. I would consider the resistor on the same side as the LED.
Ok thanks
And consider taking the collector of the PNP to the emitter of the NPN.
by Nick
Wed Feb 13, 2019 2:24 pm
Forum: Everyones Projects
Topic: Warning LED when valve stops conducting - a little SS help needed
Replies: 102
Views: 665

Re: Warning LED when valve stops conducting - a little SS help needed

Transistors never fully turn off. I would consider the resistor on the same side as the LED.
by Nick
Wed Feb 13, 2019 1:51 pm
Forum: Everyones Projects
Topic: Niobium - Valve pre for SS Power Amp
Replies: 48
Views: 3725

Re: Niobium - Valve pre for SS Power Amp

Should the VR tubes introduce any hum; should I try without the parallel cap? You may be assuming that because the hum increases when the vr tubes light, the vr tubes are generating the hum. More likely the arrival of B= which will cause the vr tubes to light is causing the hum. If it hums a bit be...