Hello Everyone ! I found this neat little circuit and/or kit ! It can be found at > A Start-Up Delay For Vintage Amplifiers Also here is a pdf from "Audio-Express 2001" that give more details ect... > http://www.nervenet.info/HT_delay/ax_aug-2001.pdf Could someone voice there thoughts about using this and/or the pro's and con's of its use ? Thank's for listening !😕
I expect to see here all advocates of B+ delay myth, either directly or indirectly affiliated with sales and promotion of such obsolete superstitious devices and kits. Also, tube amp sellers who use the feature to brag may chime in soon. 😎
I always thought start up delays were for preventing blowing up rectifiers during the initial charge of the power supply caps, and blowing breakers during the same routine with larger amps😀
Will something like the above posted circuit help to get rid of turn-on thumps in a preamp or line-stage ? Also would it be better to use something like a CL90 type in-rush current limiter ? Basically just trying to understand how such things effect operation at start-up ect....
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Here you go: http://www.diyaudio.com/forums/tubes-valves/168981-lets-settle-b-cold-tubes-issue-9.html#post2226032
But first of all you have to find the cause of cracking and popping and solve the main problem. I had similar problem when used some tubes out of specs for max voltage between cathode and filament. I had to select tubes that don't crack and pop.
The only snap crackle or pop I can think of comes from "Rice Crispies" Lets hope you don't sweep them under your rug ! I'm talking about a turn on thump heard through speakers sometimes when first turning on some amps !
Valve amps come on slowly so there is rarely any turn on thump.
I have built valve amps for many years and never had any problems with power on upsetting the amp or the tubes. In fact I havent ever replaced a tube that I can remember.
I have built valve amps for many years and never had any problems with power on upsetting the amp or the tubes. In fact I havent ever replaced a tube that I can remember.
Hi Nigelwright7557 ! I'm kinda new to building tube amps ect... So time back I had built a SOHA tube HP amp, it was a very good sounding though the design had a few flaws. One of them being turn-on thumps, the current revised version takes care of such things ect... They used a relay based delay of some sort ! Its called The Super SE SOHA II and is getting rave reviews ! Its both a HP amp and Line-stage in one.
Unless your amp has turn on thumps I wouldnt add the extra complexity of a soft start.
Having read through DIY audio threads for a number of years now soft starts are always causing problem. If something can go wrong it will eventually go wrong. KISS keep it simple !
I diffidently support the "Kiss-rule" and agree with you ! But even Pass Lab amps use in-rush current protection like the CL90's ect... Check the schematics for the Aleph or F3 through 5 series. Do you think the above circuit has enough merit to be worth trying to implement into my old SOHA ? Here is a link to the SOHA > http://gilmore2.chem.northwestern.edu/projects/cavalli2_prj.php
At least the soft start doesnt use a relay and a relay is usually the cause of the circuits eventual failure.
I can understand not wanting to apply full mains in one go but the smoothing capacitors will take a little while to charge up slowing down the HT.
I am not quite sure what damage this does to the heaters.
I tend to use DC for my heaters so again I have the benefit of a smothing capacitor charging up to slow thinsg down.
I can understand not wanting to apply full mains in one go but the smoothing capacitors will take a little while to charge up slowing down the HT.
I am not quite sure what damage this does to the heaters.
I tend to use DC for my heaters so again I have the benefit of a smothing capacitor charging up to slow thinsg down.
This thyristor relay is harmful
It switches on abruptly
It is opposite to soft start that is actually desired to minimize inrush currents.
Stick a resistor across the SCR to allow a soft start, and the SCR will provide full power when switched on.
The problem with such soft start circuits is that as the tubes start to conduct the circuit is limiting current flow so voltage does not come all the way up till the relay closes any way.
The problem with such soft start circuits is that as the tubes start to conduct the circuit is limiting current flow so voltage does not come all the way up till the relay closes any way.
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It won't help. Look at schemo: the cap after this delayed relay may be softly charged up to the voltage equal only to rectified voltage minus the sum of all breakdown voltages in a commom Zener string. Then it will initiate it's hard start.
If you really want a soft start, you may go this way: http://www.diyaudio.com/forums/tubes-valves/168981-lets-settle-b-cold-tubes-issue-9.html#post2226032
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Does the SCR have a progressive on nature ? If not would a simple CL90 type in-rush current limiter in most cases do the trick ? I'm really not sure what I want, just trying to learn and understand about various soft start techniques used and why ! The diytube ST35 dynakit EL84 amp uses A CL90 also !
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No - yours is a hell of a lot more elegant and comprehensive (unsurprisingly!). The MOSFET follies approach is one even a simple motor mechanic like me can folllow
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