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Ready-to-Run (RTR) SSR DC Speaker Protection and Delay GB

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Kokanee

Kokanee

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Joined 2010
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Fellow builders, I am a little confused / drawing a mental block about how much resistance I should plan for when building the low capacitance PSU based on the voltage as xrk971 has explained in post #875

I have tapped off the transformer secondaries before the All C's psu and the voltage I am receiving for the input of the low capacitance PSU is around 68VAC. I am powering up with Variac to DBT to power inlet and to psu and amp is no problem, operates as expected. I powered up once w/o the DBT to see what I am receiving at the tapped points, it was 72 Vac p-p at 110V on the Variac

I know that I cannot use this value of 68Vac or 72Vac p-p which would give 68V/2ma = 34kohms or 36kohms. Should I be using the secondary voltage of one of the windings (36Vac) which would give a something like 36V- 2.8 V for the diode drop and design on a voltage of 33Vac which would yield a voltage of 16.5K ohms.

One other scenario I thought of, was to build the low cap psu board based on the 72Vac being applied and build the board to past the capacitor. Then apply power to the circuit and measure the voltage after the capacitor ( capacitor would be attached properly to ground). Then measure this voltage and design the resistance on that voltage.

Sorry if this sounds way out there, trying to figure it out. Help please

MM
 
xrk971

xrk971

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Just one secondary is enough - it doesn’t matter which as it’s a very small load. 36vac is 51vdc. You don’t want it too high because the SSR has a voltage regulator to drop that to 15vdc. So you will just be burning off more power. About 22uF is all you need and the load that SSR presents is 20mA. This should decay in about 100ms.
 
G

gary s

Member
Joined 2002
Hi X, talking about the low cap fast turn off small PSU to power the SSR - can I ask if one of these tiny PSU's is OK to power both channel's SSR boards, or should you have a separate PSU for each SSR? Just making this up now, so opportune time to ask the question.

Regards,

Gary..
 
sp33ls

sp33ls

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This will be my first time using active speaker protection, but seems simple enough -- just three connections. ;)

1) I plan on grabbing power from Pvout on my SLB PSU (~24VDC). Anything I need to worry about there (re: noise/additional CRC filtering)?

2) Should I try to keep the SSR a good distance from my Cinemag input transformer? Or is noise not so much an issue.

Thanks for offering a high-end solution for DIYers. :)
 
xrk971

xrk971

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If you have access to your main trafo secondary (AC input to your SLB), use that to power the simple low capacitance PSU board that comes with the RTR SSR. It needs 2 1n400x diodes, a 22uF cap, an optional LED and current limiting resistor for LED to get 2mA. This simple PSU will cut power to SSR in 100ms after power off and it disconnects speakers immediately to prevent turn off thump. It will act like a wire when on so no more noise emitted than a speaker wire. So what ever precautions you keep your cinemag trafo quiet is good but I don’t think it’s inherently noisy

Schematics for the connections here:
https://www.diyaudio.com/community/threads/rtr-ssr-speaker-protection-gb-4.378742/post-6971387

Hope that helps.
Good luck!
xrk971
 
sp33ls

sp33ls

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Thanks again, X!

Looking through my drawer of spares, I found a couple Silmic II 50V 33uF. Should be close enough, yeah?

Is the easiest/cleanest way to tap into trafo secondaries by using terminal blocks? Would be convenient to tap into them from the SLB board itself. :p
 
xrk971

xrk971

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Joined 2012
etsy.com/shop/XRKAudio
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What I do is to take a 22ga wire and twist it with the 16ga wire that I crimp on the Fastons going from the trafo to the SLB. That gives me a neat and clean connection. Twist the 22ga wires together and run it to the low capacitance PSU for the SSR. 33uF should be ok - if you experience thump then change to a 22uF value later. Or power both SSRs from one of the small PSU’s.
 
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sp33ls

sp33ls

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bloqhed said:
I suppose I should change from my 4.7uF, seems I went a bit extreme when I read the words low capacitance. :D
Click to expand...
Lol well -- if it's better to go lower than higher, I also have some 10uF 50V I could use..? The schematic does indeed show 4u7 on it.

Oh, and it seems I just need to tap into both of the hot/line secondaries (not the neutral), and then also connect to just one of the neutral connections? So, I need to make three additional connections from crimping Is that correct? I have a shielded cable I could try to use, but that's only 2 conductors.
 
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Kokanee

Kokanee

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Joined 2010
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Hi X and others,

A quick question about the 22uF cap used on the low capacitance power supply. What is the minimum voltage rating I could use if I am running close to 50VDC into the low cap module. Is it the 50 V or greater, or can I get away with much less.?

Reason I am asking is that my capacitor inventory is very low, so would like to use what I have, rather than ordering new. Thanks for the help.
 
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