Hi all, I have a pending issue to address.
Recently I diy a tube preamp wif a matching tube rectifier power supply. I used this combo on my existing old Sansui amp.
It seems like the amp relay un-triggered(protection led blinking) as it sensed dc on the preamp pre-out stage.
Hence do I have any solution to rectify this issue? Meaning that I able to block any dc from pre-out stage of the tubes entering the power amp stage?
Tks for the feedback.
Recently I diy a tube preamp wif a matching tube rectifier power supply. I used this combo on my existing old Sansui amp.
It seems like the amp relay un-triggered(protection led blinking) as it sensed dc on the preamp pre-out stage.
Hence do I have any solution to rectify this issue? Meaning that I able to block any dc from pre-out stage of the tubes entering the power amp stage?
Tks for the feedback.
Schematic? Is this a published design or your own design? Is there any anything in the design that addresses AC coupling of the output, such as a capacitor or a servo?
Yes it a published circuit diagram of the M7.
Unaware of uploading the diagram though.
Has the output socket, on the preamp, got zero volts DC on it?
If not, it's a bad output coupling capacitor.
It seems like the amp relay un-triggered(protection led blinking) as it sensed dc on the preamp pre-out stage.
Hence do I have any solution to rectify this issue? Meaning that I able to block any dc from pre-out stage
of the tubes entering the power amp stage?
If the circuit is otherwise sound, there may be a turn-on transient from the preamp that the amplifier sees.
I've always added muting at the outputs of tube preamps, in the form of a normally closed relay that shorts
the outputs to ground. It's run by a 555 timer that enables the output after 30 seconds (or more).
Another option instead of the above would be significantly reducing the size of the output coupling capacitors.
Last edited:
Difficult to tell from a fuzzy picture, but it looks like a 3.3uF output cap with a 1M ground leak resistor. This could put out a significant voltage for quite a lot of seconds after switching on, even with the slow start of a valve rectifier. Change the resistor to 100k and see if that fixes it.
Difficult to tell from a fuzzy picture, but it looks like a 3.3uF output cap with a 1M ground leak resistor.
This could put out a significant voltage for quite a lot of seconds after switching on, even with the slow
start of a valve rectifier. Change the resistor to 100k and see if that fixes it.
Yes, or decrease the cap size by a similar factor, which may also improve the sound.
What's the amplifier's input impedance?
Last edited:
Yes, or decrease the cap size by a similar factor, which may also improve the sound.
What's the amplifier's input impedance?
Fyi amplifier input impedance is 50kohm.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
- Home
- Amplifiers
- Tubes / Valves
- Filtering of DC volts?