SSR is unfamiliar to me, but from your post, did you mean 'SCR'? The latter were used in crowbar circuits for speaker protection...
This question is aimed to TRUE Elec Engineers, not fuse or wire directionality believers.
Has any of you ACTUALLY worked with and recommend a SSR which does not introduce any audible distortion on the speaker line and which can operate with a large range of trigger voltages (12 - 48 VDC, may need to have on board voltage regulator for this range). I am building a speaker DC protector and do not want to use electro mechanical relays becoz of DC arcing and contact erosion issues. It needs to be capable of switching up to 15 amps at about 100 volts.
Only TRUE engineers reply please.
Thanks
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@atmasphere , yes I meant SSR = solid state relay, not SCR. Thanks Has anyone used one of these before: https://holtonprecisionaudio.com/collections/diy-audio-products/products/audio-solid-state-relay-hpa... |
Has anyone used one of these before:Not used it but I see no reason why it shouldn't work just fine. |
Thanx but one has to be very careful with other SSRs. Most of them are made for motor control and are not suitable for audio freq range (20 - 20k) and some of them cannot stop DC and are only made for AC. There are so many out there but only a VERY FEW are suitable for audio. That is why I wanted to know if anyone had specifically used one and hence happy with the results. Thanks |
Hi Cakyol Darn, a legitimate question on this forum. Ok, I'm a real EE. I'm not aware of a high failure rate in amplifiers, but perhaps just that...unaware. Are you concerned with a specific aspect of your system that you want to protect your speakers with something faster than a fast acting fuse? I admit to not having used an SSR in your application, but like you, would be curious about any acoustic artifacts associated with putting even a low impedance semiconductor in series with the speaker wiring. On the other hand, as infrequently as a mechanical relay would be switched hot, i.e., under heavy load, I wouldn't have any concerns about contact erosion or wear for one with contacts that are properly sized. Also, I'm curious what you were going to use as a derived control signal for the relay of your choice. Keep us posted on your progress and results! |
Hi Cakyol It might save some time and effort by going to (as suggested above) some engineering or diy audio sites to ask this question. Reason I say this is because finding someone here who is experienced at swapping out different solid state relays is more than likely to be over the engineering pay grade here. Not saying there aren't some smart people here, just saying maybe not as specialized as what your hunting for. good luck Michael Green |
Just on the surface analysis, an SSR would sound like crap, overall, in any audio application. This is so obvious to me, that I’ve never made it past the idea of looking at the acronym of SSR, and then moved along and away from such an idea. Ie, that the thought was discarded as thoroughly as possible, before it even began. Like the idea of taking the tuna sandwich I might be holding and smearing it on my face, as a way of ingesting it. Silly beyond belief, not to be considered a thought whatsoever. And that’s what I think of the idea of SSR’s in audio gear. That the thought was discarded long ago, by just about anyone in the world of audio that you can imagine. A gentle but quick mental/internal ’no, that’s not going to work’, and then they moved on. Relay or circuit breakers is better, as the quality in sound, is better. Better than any SSR. And all those audio designers and engineers you might want to get an opinion from, they invariably understand audio quality and that definitely includes the power cords, the fuses, and the cables -- all as being important. This is about audio quality, not some numbers squeezed out on the face of a meter and analyzed via spec sheet. 1000 kilos of raw dung will, displacement wise... fit inside my car, and the volumetric spec is there for it, but I’m not about to test that or do it. My response is mildly over the top but honest in my analysis of SSR’s and my opinion on them in quality audio... I’m just reflecting the seeming mood of the OP itself.... |
I’ve never put a relay int he signal path. But Omron made nice, reliable relays electro-mechanical relays that I used in many commercial products for soft turn-in. triggered by DC - just what you need. The relay chatter issue typically comes when one uses AC to control AC with predictable, feedback-induced results. Ask me how I know. I cant comment on SSRs. I do believe that solid state switches are superior to mechanical ones in low level signal paths, but they vary all over the lot. Most power SSRs are intended for just that - power. But where is the DC coming from? If unreliable equipment or prototypes/etc do what IO do and insert a fuse box during those periods. |
Even NASA uses fuses, just like most everyone in high end audio does. Fuses have come a long way, baby. NASA started studying advanced fuse concepts twenty years ago which, ironically perhaps, is about the same time advanced audiophile fuses were introduced. Coincidence? Now, NASA might not give a hoot about sound quality but audiophiles certainly do. - Ex NASA Range Rat |
Let me try & respond to some of the comments made recently. - First, a fuse will NOT protect a speaker from a DC fault. If and when a fault occurs, the speaker wire, especially the tweeter wire will melt and catch fire WELL BEFORE a fuse has time to act. Therefore your speaker will be destroyed, saving the fuse. The ONLY sure way to ensure that the fuse will blow before the speaker is to use a crowbar circuit. I dont like the idea of that. - Secondly, normal relays, regardless of whether they can carry HUNDREDS of AC amps will NOT be able to break a DC circuit, In a fault condition, The DC will arc and continue destroying the speaker and the relay. At most, if one is lucky, the relay may save the speaker but it itself will most definitely be destroyed. Look at relay specs CAREFULLY and note that MOST are rated at no more than 30 Volts DC. I have +/- 90 Volt rails. - The amp I am building is high power BIPOLAR transistor based so in case of a fault, it is more likely to fail as a short than an open circuit and hence more likely to destroy speakers as compared to a MOSFET output stage one. Hence the need for a reliable speaker protector. - Most commercial amps use a relay in the output MOSTLY to avoid thumps when first powered on. Altho they MAY protect the speakers in DC fault cases, their intention is the former not the latter. - Thirdly, SSRs made with back to back MOSFETS driven down to a few milliohms will make a PERFECT wire, nobody (except the superhumans on some of these threads on this site) will hear the existence. - As for the NASA fuses/relays, I know about them, they are encapsulated in nitrogen under pressure so that they MAY be able to break DC but they cost in excess of $200 or so for a 15 amp relay. - The control circuit I intend to use is one by Rod Elliott and here it is: http://sound.whsites.net/project33.htm Thanks |
cakyol - As for the NASA fuses/relays, I know about them, they are encapsulated in nitrogen under pressure so that they MAY be able to break DC but they cost in excess of $200 or so for a 15 amp relay. >>>>Nice that you know all about them but apparently what you don’t know is that advanced audiophile fuses can oft exceed $149 and sometimes even exceed $200. Maybe NASA needs to step up their game. Audiophiles have two or maybe three conflicting requirements, cost, sound quality and protection. |
This is more like it: https://www.mouser.com/ProductDetail/Infineon-Technologies/IPB017N10N5LFATMA1?qs=sGAEpiMZZMshyDBzk1%... 100V, 180 amps, 1.5mohms (almost lower than the speaker wire itself), about 80 nanosecond turn off time (increase that becoz of inductive speaker load) and only about 8 bucks a piece. In theory, it looks perfect, the only issue is with switching MOSFETS, they dont unfortunately specify the frequency response.... |
Unfortunately, these are about $220 -> $320 on average: https://omronfs.omron.com/en_US/ecb/products/pdf/J144-E1-05.pdf Hopefully an SSR will replace this. |
I have +/- 90 Volt rails. This is more like it:I think you need higher voltage rating than 100V http://www.geofex.com/Article_Folders/ampprot/dcprot.htm |
Most speakers have a capacitor in circuit before the tweeter which blocks all DC. The tweeter won't be harmed in this case. I used a Phase Linear 700 without output relay for years, (original design had no relay) and it had multiple issues and would go full DC (105V) on occasion. Fuses protected the speakers each time this happened. Mechanical relays work as well to protect speakers. Two solutions out there already, that are time tested, and my empirical experience confirms it quite well. |
It’s an expression used by someone who still thinks there’s room for argument regarding aftermarket fuses and fuse directionality. A renegade. A refusenik.
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I did not mean to say I wont use a fuse. This is an ADDİTİONAL protection. Fuses will of course be there. And yes I will need a mosfet for at least 150 Vdc since 100 v is too close for comfort. As for fuse directionality changing the quality of sound I am sorry to say that I have done tests on this and have not observed ANY sound changes whatsoever. My ears are normal human ears not superhuman :). So as far as PERSONALLY I am concerned fuses and how they are inserted, do NOT AFFECT sound. |
Take a look at this link: http://sound.whsites.net/articles/mosfet-relay.htm |
3:18am Hi Gibbs A simple in line fuse will protect your main drivers that have no blocking capacitor. I have much experience with this as well. |
Hope I don't get into hot water here for the link. https://www.ebay.com/itm/New-VHC-1-SPDT-Vacuum-Relay-26-VDC-for-RF-Switching/390332847631?hash=item5... These could be triggered by a conventional circuit. I've used them to handle a couple kilowatts of RF. Trigger time is in the low milliseconds. There may even be quicker ones. Contacts are vacuum sealed and very tough. There are RF types and high current DC types. Either should handle anything you can throw at them. |
@rodman99999 Without a load it will appear that the cap is passing a voltage in your example. The voltmeter, which is typically 10 megohms, is high enough impedance that it will appear as if the cap is passing voltage, but if there were any significant load you would not see anything like this. In fact a non-polar will block DC quite effectively- and protect a tweeter from DC coming from an amplifier. The problem with non-polar caps is that they are actually two electrolytics in series. As a result, they make distortion in both directions since electrolytics can draw considerable current if reverse biased. Now if you took two electrolytics and put them in series ('back to back', so to speak, which is how a non-polar is built) but then **also** biased their junction with a DC voltage, as long as the AC waveform going through them has less amplitude then the DC voltage (thus keeping them forward biased) they can be as low distortion as a good film cap. Electrolytics have a bad reputation as coupling caps but they can work quite well if one understands how they work. |
Less than one minute ago, I concluded an experiment. In series, I connected a .1uF Jupiter, copper foil/paper/wax capacitor, a Quart, 8 Ohm tweeter and the negative, of my Fluke multimeter(set to 2 VDC). Touching the multimeter’s positive lead to the + end of a 1.5V, C cell battery and the capacitor’s open lead, to the battery’s - end, results in a momentary(1-2 sec), 1.5VDC reading on my multimeter. Reversing the polarity, results in the same, every time. If there is full DC getting through, long enough for my multimeter’s digital display to recognize and register it, It’s difficult for me to believe, that(perhaps) 80VDC, from a toasted SS amp’s outputs, wouldn’t fry a tweeter. Color me skeptical. |
@Rodman99999, I'm not sure how to explain those results, but if I understand correctly the meter was indicating the voltage across a series combination of the battery, the cap, and the tweeter. Wouldn't it be more meaningful to put the meter across just the tweeter, and put the battery across the series combination of the cap and the tweeter? Regards, -- Al |
