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HackerNAP soft start

Well spotted Hacker. Certainly in my Starfish/ZAP250 combo the thump from turning on the preamp second is MUCH louder then that from turning on the power amp. Like you, I always hit the switch for the preamp before that for the poweramp, for this reason. I do the reverse on poweroff.
 
Harthold said:
a muting relay on the preamp ps? I thing i have some other circuit in my bits box that I could try Ta..
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No, in the preamp itself. It would need to be inline between the output of the gain stage and the actual output connector, so that the preamp circuits were disconnected from the power amp while the preamp stabilized. It should only take a few seconds unless you've got some crazy VBE arrangement in your pre/PSU that takes forever to come up to voltage.

Edit: what exactly is your setup?
 
simonbrown said:
Well spotted Hacker. Certainly in my Starfish/ZAP250 combo the thump from turning on the preamp second is MUCH louder then that from turning on the power amp. Like you, I always hit the switch for the preamp before that for the poweramp, for this reason. I do the reverse on poweroff.
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Yup, it's horrible and always gave me the willies. A relay and/or remembering to do it in the correct order is definitely in order!
 
Thanks for all the advice I have 2 K4700 kits at the ready but my question was raised after I read a note on the paperwork sent with my HN5 Canterbury Windings transformer which says ( Inrush current limiting required )now what ?
 
Pardo's STR's now sport an accelerator and tend to stbilize quicker than the old TeddyRegs. But a relay in the signal path has to be top notch not to degrade the signal. What do you you use Carl?
 
Harthold said:
Pardo's STR's now sport an accelerator and tend to stbilize quicker than the old TeddyRegs. But a relay in the signal path has to be top notch not to degrade the signal. What do you you use Carl?
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The trick with a pre-amp muting relay is to arrange to short the output to ground, using a normally closed contact, and open it when ready. The relay is then not in the signal path at all.

This is fine with Naim derived pre-amps; the B4 buffer would be happy with this too. If your pre-amp is something else, please ask here if it will mind starting up into a short.
 
Harthold said:
My Velleman circuit does indeed disconnect the speakers instantly when switching off and what is really important protects my speakers: There was a cold solder point in PS and the red light and relay didn''t let powered signal out.
The question is that the circuit is fast in switching on and the thump is apparent.
A caveat must be added here: this phenomenon only happens when I switch on the PS for the NAc and the NAP from the Hydra mains distributor. Nevetheless the relays don't wait +_6 seconds to trigger, that's the situation.
Cheers wise men
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at 16v, i've a 1000µf one on C11 pos, and my nap doesn't make any noise anymore ! switching on or off

it power "put relays on" 24s after start, got big tanks caps charging while 15s!

when you build this kit, take care to isolate the zener and plugg it to the right way!
 
Harthold said:
But a relay in the signal path has to be top notch not to degrade the signal. What do you you use Carl?
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I don't ;) I've got Vellemans in the monoblocks to stop the switch on thump, but I just make sure to switch the preamp on first and off last. Maybe one day I'll out output relays, maybe not. Eventually I'll be using an active XO so I might add relays in there.

PigletsDad said:
The trick with a pre-amp muting relay is to arrange to short the output to ground, using a normally closed contact, and open it when ready. The relay is then not in the signal path at all.

This is fine with Naim derived pre-amps; the B4 buffer would be happy with this too. If your pre-amp is something else, please ask here if it will mind starting up into a short.
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Wot PD said :)
 
Just heard from Terry at Canterbury Windings he recommends using a soft start circuit of some sort with his Toroids HN5 etc which soft start are other pfmers building HackerNAPs with these trafos using ?
 
I finally got my HackerNAP fully sorted with Kendeils on board. It's had many power cycles in build / test with the same fuse (5A anti surge). I powered up 3 maybe 4 times after fitting the Kendeils with no issues, rechecked bias and offset - all good. Put the lid on and heaved the thing to it's final destination on to my rack. The first subsequent power on blew the fuse to smithereens. I literally had to tip the amp up to get the 'remains' to fall out of the fuse holder. The plug fuse also blew (also 5A). After rechecking internally I suspect the internal fuse had got a bit 'tired' and that combined with the low ESR caps was too much for it. I replaced with another 5A and upped the plug fuse to 13A. Several power cycles later all is well but I suspect that if I turn on / off enough I'll blow more fuses.

I'm thinking of either adding a soft start module downstream of the power relay OR changing the relay for a zero crossing solid state job. Similar cost for both, replacing the relay would be easier.

Anyone have any recommendations for a relay (Crydom?) or other suggestions? I have 2 of Terry's HN3 traffos by the way
 
This is a well timed update, my HackerNAP with 2 x HN3 Tx blows the **** out of the 5A anti-surge fuse I have every time, the plugtop has a 13A which survives OK.

The two 406 VA traffo's should only be about 3.38A at 240VAC - is this correct? I need bigger fuses or a soft start I think.

Cheers

Gareth
 
I have some 10A a/s fuses - I'm wondering if it's safe to run these until I can implement a long term solution. I'm going to research solid state relays....
 
Try a 6 or 8a

One of my amps with 1kva and 260k uf caps starts fine on 8a.

A ss would be better.I like the Lede Audio ones.

Paul.
 
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