Standby sw wirinq question

[alexradium]

alex, 10nF meant allready 300k arround over switch for 50cps operation, Do you think reducing to 100-47k arround will help ?

try and see,every amp is different.
Anyway,i'd switch only the screen grids line.

[J M Fahey]

FWIW , simply out of lazyness, I never use switch snubbers, so in general most of my amps pop or thump.
MOST customers (as in 90-95%) of them never even mention it.
A few do, I say no problem, if in 10 days it still annoys you, bring amp back and we´ll try something.
Less than 1% does and all others, when asked, say, 1 year later or more, say "what thumop?" ... they grew so used to it that they forget.
The very very few who have a real problem with that, get my "improved standby" switch: it cuts (SS) or shorts (Tube) speaker out, and carries the instruction (valid for both):
"turn power ON, wait 10 seconds, turn Standby ON" To turn amp off do the exact opposite.

WORKS LIKE A CHARM

To comply with your friend´s wishes, who actually wants *no pop* rather than "switch high voltage on/off" which to him is Chinese, he{s interested in the function, not the Tech details, my "standby" might work.

Or use Univox´s and some Silvert6one´s infamous "standby": ground or join power tube drive signal (I faintly rememberv they shorted plate to plate at the PI, check their circuits).

[catalin gramada]

Thanks JMF. Is not a problem to implement a absolute silent standby. My problem was to get rid of the turn-on pop on this particular standby sw. Any mods to implement a proper switch including current limiters, relays etc did not worth in this build. I choosed the simplest solution and will remain as so with or without startup pops. Thanks.

[TonyZ]

That is the problem: No one has to be qualified. On this forum we have some very experienced techs, and we have guys who are lifting a volt meter for the first time. None of them had to get qualified to jump into an amp.

Excellently put. I find the trouble when dealing with subjects so broad as this is that you never know what you dont know, so it can be hard to accurately judge your own competence. Whether you have technical knowledge without practical experience, vice versa, or not much of either, it is the things you DONT know that catch you out - and when your dealing with high voltages there are no "small" mistakes.

So theres knowing enough to spot the dangers, then theres knowing how to eliminate or avoid them, but when do you know enough to know that there isnt still something unaccounted for going on?? When is knowledge in similar fields transferrable and when will it give you a false sense of security??

Once I tried compiling a "top tips" kind of list but it basically became a list of how many different ways you can say "BE ***ING CAREFUL"

BTW I didnt mean to suggest that the OPs particular issue was originating in the switch, I was just sharing experience.

[catalin gramada]

It is a bass gtr. amp.Think it will never be miced. Still have to instal half 12au7 in preamp tail as buffer stage line out. So my concern regards to not have disfunctions in this direction as time preamp stage share the same B supply line.Popping into few kw PA could be really annoying. Otherways this "pop" could be considered as be in "standard" limits...in the end.

[catalin gramada]

Did a little web search and found interesting possible explanation by Gingertube , Thanks

[catalin gramada]

Allright. Did some tests and found Gingertube was perfectly right.He sugested to use grid stop diodes to cure it. But I Put some tens kilos resistors in B supply rail between screen grids supply node and PI supply node it acts as real startup inrush limiter to PI cap and pop noise is gone. Connected screen grids and PI to the same suply node and get a loud "thump". Hiwatts did it and I think all this Hiwatt amps suffer from this. In my case I used a minimal 1K resistor between grids supply cap and PI supply cap (for decoupling reason not specialy for voltage dropping) to have as much voltage excursion in my cathodine PI. 1K is pretty small value, changed with 22k for test and act as real limiter at startup.- thump pop is gone completly-it is abolute silent standby startup. Unfortunately I cannot use such as big resistor values but many amps can and use it to drop some voltage to PI supply node. Think "thump" mistery closed. Thanks.

[nsubulysses]

I have asked this question before and got good answers but I didn't 100% understand the answer. But perhaps this is exactly what gingertube and Catalin are talking about now. Is that what these 1N5062 diodes are doing in the schematic posted?



http://music-electronics-forum.com/t44151/

now it makes sense.

I think

[catalin gramada]

For a very good reason found to not use a standby switch at all but a power limiter resistor in primary side and a "shunt" switch instead. The beneffit of soft start is huge in terms of reliability of amp. If a mute function is need it can be done in other better ways as JMF states.