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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 23 reviews
Soft Start/Speaker Protection Boards

Built 2 pairs. These boards are quick and easy to build and work great. Would highly recommend!

James W.
Soft Start board working well

The documentation for the soft-start board is a bit stale, but generally adequate. The PCB quality is first rate, and the overall design is good as well. I substituted an Omron GSLE-1A4 (24Vdc) relay because the specified part was no longer available. It fits and works well. This relay has a 10 amp rating @ 250Vac. I used a 1.0 uF MKT X2 rated capacitor for the input power supply. Smaller capacitors I experimented with, did not seem to supply adequate current. I wanted a long delay, so I up-sized the timing capacitor to 4700 uF, which gave me about 2.6 seconds delay to relay closure.

Rich W.
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.

Edward M.

Awesome fast shipping and worked perfectly! Thanks!

Back panel kit

What can I say. Always nice parts and fast delivery.

All perfect

I have received everything well and it looks very good quality.
I have already mounted all the components on the PSU board and the rest as well, but have not been able to test it yet.
I have another order for an F5 kit pending and I think some other item, but I imagine it will be stopped at customs.
I am eager to receive it and be able to finish the project. Surely this will be the first of several (looking at the quality of the material, I am already waiting for there to be stocks for an aleph J).
I hope that at least it brings back memories of an pass labs aleph 0s that I had years ago and that I will always regret selling.
Many thanks to diyaudio and first Watt for giving us the opportunity to enjoy these projects.

david b.
Perfect, just as always

diyaudiostore is just as reliable as a shop could be. Plus, they're friendly, helpful, and have a sense of humor. They make one feel a bit at home.

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