[Daniel Pumphrey]

Hi,

I was wondering how many have amps built with the Hansen board. The reason is to ask about power-up thumps and if anyone else has absolute silence on power-up. I have built quite a few amps and have always had an ever-so-slight thump on power-up when using the BB chips 2132 and 2134.
This is nothing like the loud pop when powering up a Grado amp, it is just enough to notice.
This most recent amp is different than others only in that I am using two really nice Cerafine caps from Apheared and a Panasonic 10K pot, plus it also has the second current stage. It does have all the caps for crossfeed but I have bypassed this. All my amps use the Vishay resistors. I was wondering if this is caused by the really good caps . Apheared could answer this question. This is also the first amp I have built with a gain of ten. My earlier one opamp Cmoys exhibited noise at a gain of ten, so I usually backed this off to 3 to 5 depending on headphones used. Maybe I should try my original Denon CD player too as now I am using an older Panasonic.
Thanks,
Dan
Anyway I was just wondering about the experiences of others with the Hansen board.

 

[Possum]

It might be because the Hansen board doesn't use large capacity electrolytics from the voltage rails to ground. I used to also notice a pretty loud pop when powering on and off my Szerekes amp, then following Tomo's suggestion, I put on a few more capacitors (I ended up adding 8,700 total across the single voltage rail to ground in the DC-coupled Szekeres). The thump is about 95% gone. I won't notice the thump unless I strain to listen for it.

 

[Apheared]

Hmm. No turn-on thump at all? not even a mid-freq "chccchk" sound, no matter how faint? that would be incredible!

I've heard that turn-on thump can be caused by in-rush, that it's the input transistors getting nailed with sudden current, that generic "the sytem needs to stabalize" comment...

Cerafines are a different forumlation than other electrolytics, true. They could be slower on charging or somehow prevent thump... I have no idea but wow, what a selling point if so!

I have a Szekeres that's AC thru-and-thru and it's all ROA series Cerafines, power supply thru output caps... and it thumps. A deep, solid whump! I have a mute switch. that much thump.

 

[Daniel Pumphrey]

Then why is there absolutely no thump at all what-so-ever? It is just on and thats it. I thought it didn't work until I saw the LED come up.
These are the caps you sent, resistive divider because I don't have any 2426's yet. I did change the 4.7K dividing resistors to 3K I think.
Apheared,
Thanks for the great parts trade too. I also have removed the input cap and the sound improved.
Dan

 

[geom_tol]

My amp is built on a Hansen board. Direct coupled, ad825 opamps. Lots of ps decoupling.
I hear a very small pop when turning the amp on. However my on/off switch makes a louder click than the pop, even with very good sealing cans like the dt770's.
I have no hum or noise whatsoever, even at max volume.

There is a small noise when powering off, not a pop, more like a 'phffttt' noise.

The natural crossfeed (not bassenhanced) makes a very slight pop both when switching on and off.