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Soft Start & Speaker Turn-On Delay / DC Protector Combo

  • 2500


This pack includes one Soft Start Board and one Speaker Turn-On Delay and DC protector board.  They are not available for purchase separately.

Soft Start Board

Every time you switch on your monster (or not so monster) power amplifier, the initial current drawn from the mains can be many times that of full power. This is more commonly known as inrush current, caused primarily by huge power transformer switch on currents and empty capacitor banks. At power on, the filter capacitors in your power supply are completely discharged, and acts as a short circuit for a brief period of time until a certain amount of voltage has been reached. This brief period of time can be very harmful to your Power Switch, Fuse, Power Transformer, Rectifiers and Filter Capacitors. This Softstart project is employed to limit these destructive inrush currents by momentarily introducing a resistance between the power transformer’s primary winding and the mains supply, which, after a brief moment, is completely connected to the mains. This momentary delay is already enough to charge the filter caps and limit the inrush current draw.

If you have any questions please visit the Power Supply Soft Start V3 thread in the store support forum.

Dimensions 110mm x 55mm
Mounting holes Holes are on a 10mm x 10mm grid
Number of boards included 1


Board Revision 3.0


Speaker Turn-On Delay and DC Protector Board

Protect your precious speakers from power amplifier turn-on and turn-off transients and amplifier faults such as DC voltage presence at the output. The Speaker Protector connects your speaker after a few seconds from powering on your amplifier, long enough for the power amp to settle down thus eliminating any nasty thumps that you hear on your speakers. It also provides speaker cut-off in the event there’s DC voltage present in your amp’s output protecting your speaker’s voice coil from burning out.

If you have any questions please visit the Speaker Turn-On Delay and DC Protector V3 thread in the store support forum.

Dimensions 100mm x 50mm
Mounting holes Holes are on a 10mm x 10mm grid
Number of boards included 1
Layers 2
Board Revision 3.0

Customer Reviews

Based on 17 reviews
Soft Start & Speaker Delay Boards

I bought this kit to add to a commercially produced amplifier that is direct coupled. Due to it age, some of the components have drifted and the amp started to have some instability at initial power up and while shutting down.

The circuit boards are not all that large and I had plenty of room to install them in my amp. The boards themselves are of high quality. As others have said, I had to deviate a bit on the relay selection from the supplied BOM. I used two of the Omron G5LE-1A4-DC12 for the speaker delay and one Omron G5LE-14-DC24 for the soft start. For the transformer, I used a Triad F5-24. The kit is super easy to assemble and it works perfectly, the delay timing is perfect as my amplifier is stabilized before the speaker jacks are active now.

Thank for a great product, I plan to buy more in the future to add to my other Direct Coupled amplifiers.

good quality board

I am using only DC protection board, It is a very nice board, I ordered different series resistors than those mentioned in BOM, so mine were bigger, be mindful of that. Also I am going to use part# G5LE-14-DC5 for Relay, please check before ordering component.

Soft Start & Speaker Delay Boards

Good overall

Speaker turn on delay used with Amp Camp amp with a minor modification

The board quality is very good. Very nicely done.
I used the board with a Amp Camp amplifier and found that the relays would oscillate for several seconds until they finally settled.
When the amp turns on there is a charge transfer across the output cap. Without a load on the amp the voltage causes the control circuit to sense a fault and turn off. The solution seemed obvious to me so I didn't spend a lot of time analyzing the problem. Instead I put a 25 Ohm 10 W resistors on the normally closed relay contact to ground. This dissipated the turn on voltage pulse. This made the amp happy again. The value of the resistor was a what I had on hand at the time and wasn't anything special. An 8 Ohm might work better, but it would dissipate more power at turn on as the amp starts up with a signal present. I will try the 8 ohm resistors when I get around to it.

F5t v3

I'm building a pair of mono block F5t v3 balanced amps, I bought two sets of the soft start and speaker protection pc boards. With a 800 va 36v secondary torroids, the soft start I felt was a requirement. The speaker protection boards I wasn't going to use until several people explained the DC coupled amps can destroy my speakers if DC leaked to the outputs. The only interface with the audio signal is through the relays so no big deal. I'm glad they are sold together. Thank you diy!

soft start DC protection

arrived promptly as ordered, cant wait to start the next project

Anti thump

Products where bought to be used with my de-lite amp I'm building as it's told that it has a turn on thump. The boards from diyaudiostore are of the top quality as you come to expect. Nothing short of perfect.

Good pcb

The pcb quality is good, i am happy with the board and the quick delivery. Yet, really appreciated if the official building guide is attached (or a link is fine enough). The reason is the thread not easy to follow. I wish to make it work first then dig into the thread to modify the board. Thanks

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