L'Amp: A simple SIT Amp

[OlavHaal]

Thanks Michael & all...

Hi again.

No - and yes - I have two sources: Squeezbox Touch that feeds through a DacMagic. And a HD980 CD-player that also is connected to the DacMagic. So I run both through the B1. And I can run the pre-out from my HK980 which also is relative good. But I think the B1 is so good - so you really relieved me now Michael.

Just a couple of resistors and soon ready to go.....rock and roll!!!
🙂

Best to all

Olav

 

[Roscoe Primrose]

Sounds like a job for a BOZ or JBOZ... My battery powered J310 based JBOZ works quite well...

Roscoe

 

[KASUMI]

Hi,how do you guys get rid of the switch on thump,though I get no thump just the drivers cone popping out alarmingly 😱
only just noticed today

 

[ra7]

One of the simplest ways to get rid of turn on thump is to put an inductor in the power supply. It resists a change in current, and so, turns on the power supply slowly. Result = no turn on thump. As a bonus, you get a quieter supply compared to a standard CRC. Start with 2mh, 16ga. Read the Zen articles.

Another way is to disconnect the speaker before turn on. And then are more complicated ways.

 

[Zen Mod]

and another way is to put delayed shortie in paralel with spk

there is cap , so no harm

 

[KASUMI]

Hi thanks for that I still get the excursion when the amps have been switched on and then I reconnect the speakers 😕
problem existed before the new caps.

Installed some new caps today,only one amp done at the mo

 

[Zen Mod]

do you have bleeder resistor , in parallel with speaker ?

 

[KASUMI]

do you have bleeder resistor , in parallel with speaker ?

nope,just using the basic cct.

 

[Michael Rothacher]

A "bleeder" resistor across the speaker terminals will discharge the big output capacitor, which is a good idea. You could try a 3W 100 Ohm, for instance. A bigger value will discharge more slowly / smaller value more quickly.

As far as turn-on thump goes, my low-tech approach is to install a shorting banana plug across the speaker terminals, temporarily shorting the output to ground for a few seconds during power up, then I remove it. I may have mentioned this in the text.

Also, see the Zen Lite article for an automated version of the same idea.

Is that fancy square thing a capacitor?

 

[Zen Mod]

nope,just using the basic cct.

then put it

 

[stefanobilliani]

Hi thanks for that I still get the excursion when the amps have been switched on and then I reconnect the speakers 😕
problem existed before the new caps.

Installed some new caps today,only one amp done at the mo

For that you may also consider stabilizing and filter the PS with capacitor multiplier build with a power mosfet ( see Zen 2 ) , and apply a rather big capacitor to its gate to obtain a rather slow turn on of the amp an by doing so tumb free for the driver .
I also going to apply that to my Amp A for the reason that I believe my preferred version will be light bulbed and PS stabilized ( and I did some days with the current source ) .

😎

 

[KASUMI]

well thankfully the shorting of the spk terminals solves the problem that Mike uses.
Just need to find the article on the automated version,can someone supply a link please ?

Do I still require a bleeder resistor across the cap ?

thanks again
Rob

 

[stefanobilliani]

Do I still require a bleeder resistor across the cap ?

thanks again
Rob

That is mainly a matter of tastes , I like it . If the driver is equalized with a parallel RC network , you may want to take the (bleeding) resistor into account .

 

[Dennis Hui]

I've been thinking about building this with a capacitance multiplier a la Zen v9.
Would it be advantageous to use something like IRL640 instead of IRFP240
because of the higher transconductance and lower Vgs of the former part?

Thanks,
Dennis

 

[Michael Rothacher]

Do I still require a bleeder resistor across the cap ?

If the amp is to be energized without a load connected, the bleeder ensures the cap is discharged a few seconds after power down, perhaps saving you or your speakers a shock. This is why Zen Mod suggested the resistor after you mentioned hooking up speaker cables post start-up. When a load is connected, the cap discharges through the load.

It's a good safety measure if nothing else.

Zen Lite

 

[Zen Mod]

.......

It's a good safety measure if nothing else.

no more , no less

good engineering practice

through bleeder resistor , cap is both charging (powering on) and discharging (powering off) if load is absent

 

[Michael Rothacher]

Finished Motorcycle Maintenance. Re-reading Watership Down now. 🙂

 

[Zen Mod]

wakoo wabbit

 

[vdi_nenna]

Is that fancy square thing a capacitor?

Looks like a Jupiter cap.

 

[juanitox]

yes it is a Jupiter FLAT stacks , but KASUMI what is this big 10000uf output caps? 🙂