which DIY amps free of turn on/off thump?

[Bigun]

I thought this would be a useful thing to know, for people who are, like I have become, fed up with turn-on/off noises. I know a speaker protection relay will also be a solution, but I would also like to know which amps are by-design, free of such problems (unless caused by bad power supply design). Can you share your experience ?

As far as I am aware:

No turn-on thump: no. 2, 3, 7 & 8 are symmetrical amps
===================================
1/ Symasym (Mike Bitner) http://www.lf-pro.net/mbittner/Sym5_Webpage/symasym5_3.html
2/ Leach - make sure psu caps have bleeder resitors http://www.diyaudio.com/forums/solid-state/74962-leach-amp-turn-thump.html
3/ VSSA (Lazy Cat) http://www.diyaudio.com/forums/vendors-bazaar/225747-vssa-lateral-mosfet-amplifier.html
4/ FC-100 (Roender) http://www.diyaudio.com/forums/solid-state/111756-rmi-fc100-single-stage-audio-power-amplifier.html
5/ Circlophone (Elvee) http://www.diyaudio.com/forums/solid-state/189599-my-little-cheap-circlophone.html
6/ Moscode (Mr. Moscode) - if build right version http://www.diyaudio.com/forums/tubes-valves/95240-moscode-600-hum-turn-off-thump.html
7/ Pass F5 (The One and Only)
8/ Ovation SX-Amp (Bonsia) http://hifisonix.com/
9/ Dynaco 120 (with Dan's mods) - http://www.diyaudio.com/forums/solid-state/156627-dynaco-stereo-120-can-beautiful.html
10/ TGM7 (based on Greg Ball SKA GB150) http://www.diyaudio.com/forums/solid-state/239418-tgm7-amplifier-based-greg-ball-ska.html



Does have turn-on thump but might be minor: so far none of these amps are symmetrical
========================================================
1/ TGM1, TGM2 (my own) - minor but present (true for most bootstrap VAS amps)
2/ TGM3 (my own) - single transistor dc-servo takes time to settle
3/ Fetzilla (Hugh Dean, Greg Peters, Lineup & Mikelm)- minor http://www.diyaudio.com/forums/aksa/191053-swordfishy-aspen-fetzilla-power-amp.html
4/ DX (Carlos the Destroyer) http://www.diyaudio.com/forums/solid-state/96237-destroyer-x-amplifier-dx-amp-my-amplifier.html
5/ Akitika GT-101 (Dan Joffe - has commercial interest in selling kits; "small click on start up") https://www.akitika.com
6/ MJR7-Mk5 (Renardson) "just a small unobtrusive sound" http://www.renardson-audio.com/mjr7-mk5.html
7/ P3a (Rod Elliot - commercial interest - sells pcb's) PMI says "small 'click'' designer says "minimum 'switch on' or 'switch off' http://sound.westhost.com/project3a.htm
8/ TGM8 (inspired by P3A) but pcb has speaker protection on board with delay so no turn-on thump in practice http://www.diyaudio.com/forums/solid-state/245619-tgm8-amplifier-based-rod-elliot-p3a.html

Edit: I'm referring here to DIY amps that we can build ourselves - so schematics and other necessary details are freely available. I'm not so much trying to capture information on commercial amps or kits.

 

[jkuetemann]

Hi Bigun,

I think you can put the VSSA (the PeeCeeBee version for sure) on the list of nice quiet amplifiers during turn on / off. I don't find there to be any noise or discernable cone movement during the transition from off to on or on to off.

 

[atupi]

Roender's Fc-100 is also free of anu thumps, bumps or other noise.

 

[Bigun]

As the OP, I have the ability to edit the first post - so I can edit the list to incorporate your input. If you have links to the thread where the amplifier is discussed I will add those too (but I don't promise to maintain them if they go bad).

 

[Headbanger]

I never experienced any thumps from any amplifiers I've built even simple chipamps, few times I had turn off thump, which was cured by paralleling mains switch with small value X1 capacitor. That includes modified Pass F4, Citation 12, LME49830 based amp, Elvee's Circlophone and others with no specific names. I haven't used any pre-made PCB's, so I cannot comment on that, as layout is really important.

 

[balerit]

My Moscode amp (originally a Jeff MaCaulay design) has built in slow turn on.🙂
My TDA 1557 amps have no turn on thump either, they have special turn on circuitry to prevent this phenominon..

 

[AndrewT]

Roender's Fc-100 is also free of anu thumps, bumps or other noise.

it whistles and has VLF variations on shut down.
Virtually, but not completely silent at start up.

 

[djoffe]

Akitika GT-101 kit

Akitika GT-101 Audio Power Amplifier Kit

is a single rail regulated power supply design. There is a small click on start up, and no noises at all on turn-off. Note also that there is no speaker relay in the design.

 

[Bigun]

Akitika GT-101 kit

Akitika GT-101 Audio Power Amplifier Kit

is a single rail regulated power supply design. There is a small click on start up, and no noises at all on turn-off. Note also that there is no speaker relay in the design.

Is this a DIY amp - I didn't see any schematics ?

 

[djoffe]

Schematics may be found on pages 39, 40, and 41 of the assembly manual.

http://www.akitika.com/documents/AssemblyManualGT101rev1p35.pdf

 

[lanchile]

Quiet as a mouse!2sk1058 2sk2221 irfp9240 mosfet amplifier schematic

 

[nigelwright7557]

I built a class d 2092 based amplifier.
On power down I would either gets huge thumps or a siren type noise.

I found it was due to having very large power supply capacitors causing the discharge to be very slow and upset the 2092.
I found the only way around was to add a small PIC based circuit which monitored VCC and held the 2092 in reset if the voltage got less than 15 volts.

I talked to IR about it and they said it was a rare problem and I had done the right thing to fix it.

 

[Bigun]

Quiet as a mouse!2sk1058 2sk2221 irfp9240 mosfet amplifier schematic

Is it DIY'able - schematics freely available ?

 

[jaycee]

I have to wonder if it really matters, since as you should have a DC protection circuit anyway. It's nothing to add a 3-5s delay on powerup in this case.

 

[Bigun]

I have to wonder if it really matters

oh come on now, we're DIY fanatics 😀

 

[wahab]

Simulated thump of Gaborbela s 20 years old amp
modded as in the relevant thread , version with BJTs.

 

[PMI]

what can you add to these lists ? - what about P3A...

No thump (tested).

Strictly speaking, not a "free" design, because the schematic for the board is copyright protected and not available to be published, you only get it when you purchase a set of boards from the designer. However, it IS diy, and quite simple to assemble and test.

 

[Bigun]

Wahab - simulations are useful, but we want field-tested confirmation

PMI - I'm surprised P3A is thump-free as it uses bootstrap VAS, why is it thump-free ? I checked Rod's web site and he says 'minimum' noise so I take it there is some noise so I put in the 2nd list for now...

 

[meanman1964]

The FetZilla has indeed a slight turn on thump but it's left there with a reason.It was possible to remove the thump but it had to much influence on the sound.

 

[lanchile]

Is it DIY'able - schematics freely available ?

it is a diy amp kit! But not schematic available.😱