Amplifier Settings Advice

[Soulbear]

Hi Trolls
After many many "False Starts" and "Major Setbacks" I am currently slowly "Inching" ever closer to losing my "Lathe Cutting Virginity" and could do with a little advice I currently have been working on this :-

Rackmount Units.mp4

I might add, that things have not been going too well!! However, things could have been worse, much much worse!!! I will explain, in order to avoid the catastrophe of an "Expensively Blown Cutterhead" I have been trying to mimic (As far as is practicable) and "Dial In" the Set-Up, using some Very Basic low Wattage (4Watt) Loudspeakers. Other Trolls will never Know just how glad I took this little precaution because disaster struck!!

Even though I had inserted 2x 200mA Inline Fuses into the Loudspeaker Lines I somehow contrived to Completely destroy the first pair of Loudspeakers Following my House Move, I could not lay my hands on the Literature pertaining to the Gear in the Racks, but I'd taken the trouble to insert the Fuses into the Loudspeaker Lines, so, if I had a little Mess About, Play with a Few Things, Twiddle a Few Knobs, what Harm could be done????

Massive Error

The Smoke damage to the Room will be soon be sorted out with a little call, in the very near future to my Painting and Decorating Contractor I had assumed (Wrongly!!) that because I could not see any Levels on the Stageline LED VU Meter that I was not outputting anything from the CD Audio Source. The FBQ6200 Equaliser has a Mind of its Own however, and unnoticed by me, the Pink Noise Generator Function Switch was Operated and so was Simultaneously Dumping a "Max Crap Load" of "Noise" into the Amplifier. Now in Combination with the VU Meter Sensitivity Presets being out of the normal or correct position, and somewhat askew and awry, its little wonder I toasted the Loadspeakers. I do not know as yet, whether I have destroyed the Amplifirer too, only time will tell

I am somewhat puzzled why the Fuses did nothing to Protect the Loudspeakers, they were purchased Many Moons Ago, I don't remember if they were Slow Blow or not, possibly I have Mis-labelled them when moving home and they are a Higher Rating, but hey, better a Basic Loudspeaker Burn-Out, than a Priceless Cutterhead eh??

Now, having cleaned up most of the mess and damage to the room, I am in the process of having another attempt to dial things in. I no-longer "Trust" the LED Displays on either the FBQ6200 or the VU Meter and as an extra precaution, have taken the FBQ1000 and the MDX1600 out of the Audio chain, and have ((For Now) inserted a 50K Linear Stereo Pot into the Audio Lines in a "Belt and Braces" attempt to further attenuate the Signal to the Amplifier and avoid a repetition of this Faux Par.

The Amp is this one :- https://www.hifi-tower.co.uk/Sound-Light/PA-Systems-Audio/PA-Amplifiers/SPL700-Watt-DJ-PA-Amplifier-EQ-Hi-Fi-Audio-Amp-Black-Equalizer-2x-350-W-4-Ohm-2x-250-W-8-Ohm.html

When I bought this it was around twice the price, but was just about all I could afford, the Specifications seemed to fit the bill for what I was trying to acheive, I am not a Mastering Studio where the "Big Bucks" usually buys the "Best Gear" I'm just a "Hobbyist" after all!!!
Now Trolls, I have finally, afer hours of searching, located the errant literature relating to the FBQ6200 Equaliser et al. While I continue endeavours to fulfill my long held ambitions to Cut my Very Own Records, I am hoping someone can help me out here??

Firstly, apologies if this has been asked a million times before, but my questions are these :-
Q1) Without opening it up, I am assuming that the "Volume Controls" on the SPL700 Amplifier simply attenuate the incoming Audio Signal, is this Correct??

Q2) Do Most Lathetrolls? All Lathetrolls? Any Lathetrolls? No Lathetrolls? Set the Audio Signal Levels "Back in the Audio Chain" and leave the Amplifier "Volume Controls" Cranked Up?? I don't know if this is correct, but I am assuming this is how the Amplifiers have the "Headroom" to deliver the short duration peaks??

Q3, Having somewhat lost my faith in Rupturable Fuses, has any Lathetroll devised a ((VERY)) "Simple to Make" Adjustable Overload Cut-Out Circuit, that does not need Computer programming Skills using something like the Current Sensor ACS712 Module?? 185mV per Amp output must surely be plenty to drive some form of Small Boost Amplifier in order to trip/drive a protection relay??

Q4) If relying solely on Fuses for Cutterhead Protection, would "Quick Blow" be the most prudent approach??
Looking Forward to a little guidance here,
Many thanks Best Regards Soulbear

[Soulbear]

Hi Trolls
After many many "False Starts" and "Major Setbacks" I am currently slowly "Inching" ever closer to losing my "Lathe Cutting Virginity" and could do with a little advice I currently have been working on this :-
Rackmount Units.mp4

I might add, that things have not been going too well!! However, things could have been worse, much much worse!!! I will explain, in order to avoid the catastrophe of an "Expensively Blown Cutterhead" I have been trying to mimic (As far as is practicable) and "Dial In" the Set-Up, using some Very Basic low Wattage (4Watt) Loudspeakers. Other Trolls will never Know just how glad I am that I took this little precaution because disaster struck!!

Even though I had inserted 2x 200mA Inline Fuses into the Loudspeaker Lines I somehow contrived to Completely destroy the first pair of Loudspeakers Following my House Move, I could not lay my hands on the Literature pertaining to the Gear in the Racks, but I'd taken the trouble to insert the Fuses into the Loudspeaker Lines, so, if I had a little Mess About, Play with a Few Things, Twiddle a Few Knobs, what Harm could be done????

Massive Error

The Smoke damage to the Room will be soon be sorted out with a little call, in the very near future to my Painting and Decorating Contractor I had assumed (Wrongly!!) that because I could not see any Levels on the Stageline LED VU Meter that I was not outputting anything from the CD Audio Source. The FBQ6200 Equaliser has a Mind of its Own however, and unnoticed by me, the Pink Noise Generator Function Switch was Operated and so was Simultaneously Dumping a "Max Crap Load" of "Noise" into the Amplifier. Now in Combination with the VU Meter Sensitivity Presets being out of the normal or correct position, and somewhat askew and awry, its little wonder I toasted the Loadspeakers. I do not know as yet, whether I have destroyed the Amplifirer too, only time will tell

I am somewhat puzzled why the Fuses did nothing to Protect the Loudspeakers, they were purchased Many Moons Ago, I don't remember if they were Slow Blow or not, possibly I have Mis-labelled them when moving home and they are a Higher Rating, but hey, better a Basic Loudspeaker Burn-Out, than a Priceless Cutterhead eh??

Now, having cleaned up most of the mess and damage to the room, I am in the process of having another attempt to dial things in. I no-longer "Trust" the LED Displays on either the FBQ6200 or the VU Meter and as an extra precaution, have taken the FBQ1000 and the MDX1600 out of the Audio chain, and have ((For Now) inserted a 50K Linear Stereo Pot into the Audio Lines in a "Belt and Braces" attempt to further attenuate the Signal to the Amplifier and avoid a repetition of this Faux Par.

The Amp is this one :- https://www.hifi-tower.co.uk/Sound-Light/PA-Systems-Audio/PA-Amplifiers/SPL700-Watt-DJ-PA-Amplifier-EQ-Hi-Fi-Audio-Amp-Black-Equalizer-2x-350-W-4-Ohm-2x-250-W-8-Ohm.html

When I bought this it was around twice the price, but was just about all I could afford, the Specifications seemed to fit the bill for what I was trying to acheive, I am not a Mastering Studio where the "Big Bucks" usually buys the "Best Gear" I'm just a "Hobbyist" after all!!!
Now Trolls, I have finally, afer hours of searching, located the errant literature relating to the FBQ6200 Equaliser et al. While I continue endeavours to fulfill my long held ambitions to Cut my Very Own Records, I am hoping someone can help me out here??

Firstly, apologies if this has been asked a million times before, but my questions are these :-
Q1) Without opening it up, I am assuming that the "Volume Controls" on the SPL700 Amplifier simply attenuate the incoming Audio Signal, is this Correct??

Q2) Do Most Lathetrolls? All Lathetrolls? Any Lathetrolls? No Lathetrolls? Set the Audio Signal Levels "Back in the Audio Chain" and leave the Amplifier "Volume Controls" Cranked Up?? I don't know if this is correct, but I am assuming this is how the Amplifiers have the "Headroom" to deliver the short duration peaks??

Q3, Having somewhat lost my faith in Rupturable Fuses, has any Lathetroll devised a ((VERY)) "Simple to Make" Adjustable Overload Cut-Out Circuit, that does not need Computer programming Skills using something like the Current Sensor ACS712 Module?? 185mV per Amp output must surely be plenty to drive some form of Small Boost Amplifier in order to trip/drive a protection relay??

Q4) If relying solely on Fuses for Cutterhead Protection, would "Quick Blow" be the most prudent approach??
Looking Forward to a little guidance here,
Many thanks Best Regards Soulbear

[markrob]

Hi,

How long was the overdrive present until the speakers burst into flames? I assume you hear them scream prior to their death.
Were they hit with the full power or worse yet a heavily clipped signal?
Have you verified that the fuses were really 200ma slow blow?
Are the speakers really rated 4 watts RMS continuous or is that wishful thinking on the part of the manufacturer?
Were they stone cold at the time the surge was applied or were they running for some time near their rating?

Fusing can be tricky, especially when hit with such a large extended overdrive conditions. To really size them, you would have to know the i^2t (basically watt-sec) rating of the fuse from the mfg datasheet and the thermal resistance, thermal mass, and max voice coil temperature of the drivers. Still, it would seem that a fast blow 200ma fuse should be pretty conservative. Not sure about a slow blow fuse though. They are pretty beefy in terms of the i^2t rating as compared to a fast acting fuse.

Mark

[Soulbear]

Hi Mark,
Reliance on the Technology (VU Metering, Fusing) and making False Assumptions about the inherent risks (Disregarding finding and Reading the Literature!!) seem to have proved to be my downfall in this regard. Sad to say I was lackadaisical in the extreme, in a way showing more than a casual impatience in an attempt to progress further, rather than taking a more methodical approach to the task in hand. Tiredness and Currently feeling particularly unwell from a recurring health issue are my only excuses

Markrob wrote :-

Were they hit with the full power or worse yet a heavily clipped signal?

SPL Amplifier -1.jpg

SPL Amplifier -2.jpg

SPL Amplifier -3.jpg

SPL Amplifier -4.jpg

Looks very much like it Mark, I've also destroyed one side of the Amplifier Board too!! Upon testing the Amp (Once I got it out of the Rack) I found one side was outputting arount 40V DC which maybe accounts for the ruined Loudspeaker from that side, I'm still mystified why the Fuses didn't offer more protection from damage though. I have now had two failed attempts at at replacing the Blown TIP41C Output Transistors and those other components on the Amp Board that were obviously blown or that tested bad!! I've now given up on trying to attempt a repair on the Amp!!

Markrob wrote :-

Have you verified that the fuses were really 200ma slow blow?

The fuses came out of storage contained in a Zip-Lock Bag with my Handwritten label denoting that the Fuses were indeed 200mA, so I took it as read that these Fuses were OK. Actually Mark, I think they are more than likely "Quick Blow" as this Photo of the Fuse End Cap reads F 0.2 (F = Fast or Quick Blow??)

Fuse-1.jpg

Soulbear wrote

The FBQ6200 Equaliser has a Mind of its Own however, and unnoticed by me, the Pink Noise Generator Function Switch was Operated and so was Simultaneously Dumping a "Max Crap Load" of "Noise" into the Amplifier.

Just shows how destructive it can be by being inattentive to detail!! Teach me to be more carefull in the future However, I would still like to know if there's a better (Relatively Simple!!) solution to protect from excessive overloading of the Cutterhead??
Best Regards Soulbear

[markrob]

The ACS712 or others in that series would be a great way to implement a fast acting protection circuit. The problem is that you would still need to model the time energy characteristics of the head to be able to predict the real-time voice coil temperature. That would take some doing.

One think to think about would be to hang a fast audio limiter in front of the power amp and when testing, make sure that its attack time and limiting level keeps the amp in check. You can start very conservative and then open up the settings as you go.

I wonder what the chain of events was here. Did the amp pop and dump DC to the voice coils or did they short and kill the amp?

I also wonder if the that fuse might be 2A, not 200ma. Many of the small current fuses I've run into are marked in ma to avoid the just that problem.

[Soulbear]

Hi Mark,
Though my eyesight is deteriorationg I'm pretty sure the Fuse Cap is showing a rating of 0.2A (200mA) However, maybe come the morrow, I will concoct a Variable Power Supply, or simply use a 100W Wirewound Pot (I have a Half-completed Variable Power Supply Unit made from an ATX Computer Supply or the Wirewound Pot and Transformers somewhere around)) I have some High Wattage Resistors around too (Also Probably Hiding!!) If I get the chance I'll make some "Dummy Loads" out of the Resistors and Run the Current Loads through the Resistors, Fuses and a Bench Ammeter or a Multimeter and find out for sure, I'll let you know when I've made these tests
Regards Soulbear

[Soulbear]

Well Now!!!
Markrob wrote :-

Have you verified that the fuses were really 200ma slow blow?

Fuse Test-0.jpg

Soulbear wrote :-

If I get the chance I'll make some "Dummy Loads" out of the Resistors and Run the Current Loads through the Resistors, Fuses and a Bench Ammeter or a Multimeter and find out for sure, I'll let you know when I've made these tests

Thank You Mark!! What cannot speak, cannot tell Lies!!!!!

Fuse Test-1.jpg

I have been somewhat busy doing other things today, however, I managed to find a Spare Half an Hour, so I checked these so-called 200mA Fuses with a very "Rough and Ready Lash Up" on the Bench using a Notional 22-ish Volts DC Power Supply, delivered from a Small Transformer, Full-Wave Bridge Rectifier with a Pretty Meaty Electrolytic Smoothing Capacitor via a 100 Watt Wirewound Potentiometer
Suprise Su... Effing... Suprise!!!!!!!!

Mark, you are correct as per usual The Fuses took a Full 2 Amps to BLOW.......!! Here they are getting close to Popping!!

Fuse Test-2.jpg

I don't know how I managed to mis-label these Fuses way back when I bought them, I probably simply relied on the Sellers description when Purchasing and did not perform these rudimentary tests!!!!

Now I have yet another little challenge to Add to the List of things to do I have around 300 to 400 of these 20mm Glass Fuses, in batches of 10 to 20 or more of each type, ranging from an alleged 32mA..40mA..63mA... 80mA...etc, all the way up to around 5A or maybe even Higher. A couple of samples of each will be Tested rather than relying on the Labelling on the Boxes these Fuses were supplied in..!!!!

Little wonder that the Low Wattage Loudspeakers that I was using for testing purposes got "Fried"!!! Oh well, Looking on the Bright Side , at least I found this out, before "Blowing" a Cutterhead.
So great advice from you Mark!!! Thank You Again!!!
Check...... Check.... then Check AGAIN TROLLS
Regards Soulbear

[markrob]

That sucks. I've had that exact same issue with the fuse marking. Why the manufacturer uses the decimal point on the marking is beyond me.

[jjwharris]

I've written a circuit protection program in arduino, it takes 500 samples and averages them giving a sort of RMS value, then displays that on an ammeter and controls a relay to cut the signal if the current gets too high, then there is a little reset button to reset the fuse.

Hardware wise it's just a cheap AliExpress 'doughnut' ammeter and NO relay, I still use a glass fuse as a failsafe because I don't trust my programming, but PM me if you would like a copy.

It's been very nice to have when trying to EQ heads.

[Soulbear]

I've written a circuit protection program in arduino, it takes 500 samples and averages them giving a sort of RMS value, then displays that on an ammeter and controls a relay to cut the signal if the current gets too high, then there is a little reset button to reset the fuse.

Hardware wise it's just a cheap AliExpress 'doughnut' ammeter and NO relay, I still use a glass fuse as a failsafe because I don't trust my programming, but PM me if you would like a copy.

It's been very nice to have when trying to EQ heads.

Thank You JJ

Whilst I'm still attempting getting my head around this "Arduino Stuff" from JJW(And Failing!! ) I have at least taken delivery of some "New Fuses"

Fuse-2.jpg

Fuse-3.jpg

Fuse-4.jpg

After running many hours of Testing on them I've discovered that most of the Fuses I mentioned earlier in the Post, are NOT of the values I thought I was purchasing!!

Rather than waste money taking a chance on the "Mis-labeled and Non-Descripts" sold on the Bay and elsewhere, I got me some of these Fuses. RoHS Certified (RoHS stands for Restriction of Hazardous Substances. RoHS, also known as Directive 2002/95/EC, which originated in the European Union and restricts the use of specific hazardous materials found in electrical and electronic products (known as EEE) One of the more Obvious Hazards with Fuses, being that they really ought to Rupture at the Rated/Stated Capacity!!!

Reassuringly they also carry the British Standards Institute "Kitemark" which really means they'll do what they say they will do on the Box!! Over the Pond Stateside, I guess the US equivalent would be the American National Standards Institute (ANSI) or the Certification of the ISO (International Standards Organisation)
These Fuses were a little "Pricier" than the "Mis-labeled and Non-Descripts" however, NOT as Pricey as Destroyed Cutterhead or in my Case "Luckily" only a "BLOWN AMPLIFIER"
We live and Learn!!! Regards Soulbear

[Soulbear]

Hi Trolls,
JJWHarris wrote :-

“I've written a circuit protection program in arduino, it takes 500 samples and averages them giving a sort of RMS value, then displays that on an ammeter and controls a relay to cut the signal if the current gets too high, then there is a little reset button to reset the fuse”

I am really appreciative JJ, your Email with the codes and the “Hardware Purchasing Links” has duly arrived and been downloaded and Studied. I don’t want to appear inordinately stupid, but “Coding” in any form is a discipline I have never quite got the hang of. Computer usage, doing “Regression Modelling” using “SuperCalc 2 or 3” or some such, on what is now antiquated Software, and devising a “Quality Management System” to BS5750 (Laterly EN 9000 now ISO 9000, and all written in “Word Perfect” (Also Ancient)) was about my limits. I have had some nice offers of a little bit of “Hand Holding” to “Guide me through” the “Coding Process” which I will avail myself of in due course and when the stars are in alignment, just for now, this Arduino derived Protection is on the “Back Burner”

Mulling over this issue, while still “Spitting Feathers” over my “Blown Amplifier and “Wrong Fuses” Fiasco, I initially had some thoughts about how good is would be to have some Safer/Lower "Selectable" Cut-off Levels, Calibrated by perhaps using some DAW Generated Sinewave Test Tones at different frequencies. And then using the 3db per step function of the LM3915 Microchip LED VU Meter Driver. I had the idea to test this out.

VU Cutterhead Protection Circuit-3.jpg

So Trolls, I Conducted some initial tests. I know that theoretically that the LED’s used in this type of VU Meter should not pass current until the Threshold Voltage to turn on the LED is reached, but found from experimentation that this is not quite true. The LED’s pass enough Current to the base of a 2N3904 to switch on the Transistor. The downside is that the LED Glows slightly, caused in part by the 500microamps or so passing through! I simulated the LM3915 Pin “Grounding” the Cathode of the LED (Thereby Grounding the Selected Input from Whichever LED Pin to the Multi-Position Selsctor Switch) by virtue of a simple switch, which fully turns on the LED, presumably in the same way as the LM 3915 by switching the input to ground???

VU Cutterhead Protection Circuit-4.jpg

So Trolls, the idea is to now do this over, but to use Op Amps to Capture the V+ at the LED
The High Input Impedance of an Op Amp, theoretically will not "Load the LED" and when the LM3915 switches the LED input pin to ground Voila, I trigger the Op Amp Comparator Output to the base of the 2N3904 and thereby Kill the relay in turn Knocking out the Audio Amp Output to the Cutterhead. Depending on which of the LED#s are selected, we can have Cut-Off in Progamable-ish! 3db Steps!!

Following some Sterling Advice from Markrob, who reminded me that it is the Excess Current in the Drive Coils that will Destroy any Cutterhead, So following Marks advice, I revisited the idea utilised by JJW Harris, of incorporating Cutterhead Coil Current Sensing with the Hall Effect ACS712 Current Sensor and so I’ve placed an order to purchase. Thought I had some of these Current Sensors lying around, but after a wasted day fruitlessly searching for them, I admitted defeat and ordered more!!!

VU Cutterhead Protection Circuit-5.jpg

I Simply Added a further 2N3904 into the Relay Circuit, The base of which is energised by the additional Op Amp Comparator Output. The Reference and Cutterhead Drive levels will be set as far as is practicable using “Dummy Loads” and the values determined by a little further Experimentation. I let you know how it goes
Best Regards Soulbear

[Soulbear]

Soulbear wrote :-

"Following some Sterling Advice from Markrob, who reminded me that it is the Excess Current in the Drive Coils that will Destroy any Cutterhead, So following Marks advice, I revisited the idea utilised by JJW Harris, of incorporating Cutterhead Coil Current Sensing with the Hall Effect ACS712 Current Sensor and so I’ve placed an order to purchase. Thought I had some of these Current Sensors lying around, but after a wasted day fruitlessly searching for them, I admitted defeat and ordered more!!!"

Current Sensor Testing.mp4

The ACS712 landed!! So today I have been running a few Tests to "Check it Out" I Made a little 5V supply on a Stripboard picking up off my 24V DC Transformer/Rectifier Bench Set up using a LM317 Voltage Regulator and a trim pot. I found all the Output values on the various Bay sellers offerings I looked at conflicted, and seemed to quote a different mV/A for the outputs of these ACS712's ranging from 63mV/A up to 185mv/A, so best to check eh!!

Initial testing was a bit "Hit and Miss" which I eventually discovered was being caused be a "Dry Solder" Connection I'd made on the Stripboard ((Gotta get my eyes checked)) Had my 5V off the LM317 Board with no problems reading it with the Fluke MM, but when hooked up, the ACS712 just wasn't responding! Went a hunting for a "Fusion 5-15V Power Supply" that I bought ages ago and have never used, typical of most things when I want to lay my hands on, it was hidden somewhere!! Using this Power Supply, Low and behold the ACS712 powered up!! After fixing my Stripboard I hooked up a 100W 8 Ohm Power Resistor in series with an 100 Ohm wirewound pot and began to test. To be more thorough Tomorrow I'll add more resistance to the circuit, so I can start "Lower" than the 250mA minimum I got running through the sensor today. At that level (250mA) it was kicking out around 40mV and up at 500mA around 100 mV, none of these values are consistent with the "Claimed Values" in the various Online Sellers "Blurb"

I will retest using AC, which also reminded me, that if I tabulate the results while testing, I will then need to run whatever Value I arrive at, through a Precision Full-Wave Rectifier to give me DC before it goes into the Comparator!! Talk about forgetting the Basics Anyhows, I thought something Like this will do :-

Op-Amp Precision Full Wave Rectifier Circuit-V2.jpg

Keep you Posted with the Results
Regards Soulbear

[Discomo]

am somewhat puzzled why the Fuses did nothing to Protect the Loudspeakers, they were purchased Many Moons Ago, I don't remember if they were Slow Blow or not, possibly I have Mis-labelled them when moving home and they are a Higher Rating, but hey, better a Basic Loudspeaker Burn-Out, than a Priceless Cutterhead eh??

Hi Soulbear, that's quite an impressive project you started. Sorry about the destruction.

I don't know anything about electronics nor electricity, but I heard from a technician that fuses do not protect your gear (???) . They, apparently are merely there to make sure there's no fire. So the power first goes through your equipment and when it reaches a certain level, they blow the fuses. But your equipment can still be done.
If I'm wrong, please correct me, but this is how it was explained to me by a tech. So more a question from me than an advice basically...

[Ciuens]

Hi Trolls
After many many "False Starts" and "Major Setbacks" I am currently slowly "Inching" ever closer to losing my "Lathe Cutting Virginity" and could do with a little advice I currently have been working on this :-
Rackmount Units.mp4

I might add, that things have not been going too well!! However, things could have been worse, much much worse!!! I will explain, in order to avoid the catastrophe of an "Expensively Blown Cutterhead" I have been trying to mimic (As far as is practicable) and "Dial In" the Set-Up, using some Very Basic low Wattage (4Watt) Loudspeakers. Other Trolls will never Know just how glad I took this little precaution because disaster struck!!

Even though I had inserted 2x 200mA Inline Fuses into the Loudspeaker Lines I somehow contrived to Completely destroy the first pair of Loudspeakers Following my House Move, I could not lay my hands on the Literature pertaining to the Gear in the Racks, but I'd taken the trouble to insert the Fuses into the Loudspeaker Lines, so, if I had a little Mess About, Play with a Few Things, Twiddle a Few Knobs, what Harm could be done????

Massive Error

The Smoke damage to the Room will be soon be sorted out with a little call, in the very near future to my Painting and Decorating Contractor I had assumed (Wrongly!!) that because I could not see any Levels on the Stageline LED VU Meter that I was not outputting anything from the CD Audio Source. The FBQ6200 Equaliser has a Mind of its Own however, and unnoticed by me, the Pink Noise Generator Function Switch was Operated and so was Simultaneously Dumping a "Max Crap Load" of "Noise" into the Amplifier. Now in Combination with the VU Meter Sensitivity Presets being out of the normal or correct position, and somewhat askew and awry, its little wonder I toasted the Loadspeakers. I do not know as yet, whether I have destroyed the Amplifirer too, only time will tell

I am somewhat puzzled why the Fuses did nothing to Protect the Loudspeakers, they were purchased Many Moons Ago, I don't remember if they were Slow Blow or not, possibly I have Mis-labelled them when moving home and they are a Higher Rating, but hey, better a Basic Loudspeaker Burn-Out, than a Priceless Cutterhead eh??

Now, having cleaned up most of the mess and damage to the room, I am in the process of having another attempt to dial things in. I no-longer "Trust" the LED Displays on either the FBQ6200 or the VU Meter and as an extra precaution, have taken the FBQ1000 and the MDX1600 out of the Audio chain, and have ((For Now) inserted a 50K Linear Stereo Pot into the Audio Lines in a "Belt and Braces" attempt to further attenuate the Signal to the Amplifier and avoid a repetition of this Faux Par.

The Amp is this one :- https://www.hifi-tower.co.uk/Sound-Light/PA-Systems-Audio/PA-Amplifiers/SPL700-Watt-DJ-PA-Amplifier-EQ-Hi-Fi-Audio-Amp-Black-Equalizer-2x-350-W-4-Ohm-2x-250-W-8-Ohm.html

When I bought this it was around twice the price, but was just about all I could afford, the Specifications seemed to fit the bill for what I was trying to acheive, I am not a Mastering Studio where the "Big Bucks" usually buys the "Best Gear" I'm just a "Hobbyist" after all!!!
Now Trolls, I have finally, afer hours of searching, located the errant literature relating to the FBQ6200 Equaliser et al. While I continue endeavours to fulfill my long held ambitions to Cut my Very Own Records, I am hoping someone can help me out here??

Firstly, apologies if this has been asked a million times before, but my questions are these :-
Q1) Without opening it up, I am assuming that the "Volume Controls" on the SPL700 Amplifier simply attenuate the incoming Audio Signal, is this Correct??

Q2) Do Most Lathetrolls? All Lathetrolls? Any Lathetrolls? No Lathetrolls? Set the Audio Signal Levels "Back in the Audio Chain" and leave the Amplifier "Volume Controls" Cranked Up?? I don't know if this is correct, but I am assuming this is how the Amplifiers have the "Headroom" to deliver the short duration peaks??

Q3, Having somewhat lost my faith in Rupturable Fuses, has any Lathetroll devised a ((VERY)) "Simple to Make" Adjustable Overload Cut-Out Circuit, that does not need Computer programming Skills using something like the Current Sensor ACS712 Module?? 185mV per Amp output must surely be plenty to drive some form of Small Boost Amplifier in order to trip/drive a protection relay??

Q4) If relying solely on Fuses for Cutterhead Protection, would "Quick Blow" be the most prudent approach??
Looking Forward to a little guidance here,
Many thanks Best Regards Soulbear

Hi Soulbear.
I don't know what type of cutterhead you're using, but I can tell you a few things.

1 - This Behringer equalizer is horrible, I have one here and I don’t recommend using it, it inserts a lot of noise in the signal, it inverts the phases constantly, which can completely destroy your cut and your cutterhead.


2 - Use an RC filter on the speaker output of your amplifier. Here I use a capacitor with 2.2 microfarads x 250 volts in parallel with a wire or ceramic resistor with a value of 4.4 ohms x 10 watts. This will control the current going to your cutterhead and instead of heating and burning the coils, it will heat the resistor and consequently burn the fuse.

3 - Use a pure class AB amplifier, without any type of built-in signal processor. For good results, an amplifier with at least 300 watts rms per channel is recommended.

Cheers,

Ciuens Silva

ZEZ Cutters

[Soulbear]

Discomo wrote
"Hi Soulbear, that's quite an impressive project you started. Sorry about the destruction. I don't know anything about electronics nor electricity, but I heard from a technician that fuses do not protect your gear (???) . They, apparently are merely there to make sure there's no fire. So the power first goes through your equipment and when it reaches a certain level, they blow the fuses. But your equipment can still be done.
If I'm wrong, please correct me, but this is how it was explained to me by a tech. So more a question from me than an advice basically..."

Hi Discomo,
Sorta half-right and sorta not. I think your "Techie" Friend was probably thinking in terms of a full on "Short-Circuit" In that situation yes, the instantaneous values of the Current flowing through the Equipment would almost certainly Kill whatever you are trying to Protect. Similarly, if a Fuse with a Carrying Capacity that is Higher than the Carrying Capacity of whatever you are trying to "Protect" is installed, then this too will "Kill it" because the circuit cannot carry as much amperage as the fuse.

But in my case, I actually made this mistake, and erroneously installed Fuses with a Current Carrying Capacity of a 2 Full Amps!! and not the 200milliamps (0.2A) which I thought I had fitted!!!! 10 x Higher Capacity!!! If a Fuse is rated "Less" or "Lower" than whatever the Equipment you are using is capable of Carrying, then the Fuse should offer some level of "Protection" to the Equipment (Barring Shorts or other Faults) as the Fuse would Rupture BEFORE the Current reached the "Danger Point" and equipment is damaged. Trying to stop "Pushing" too much Power where it should not "Normally" go, is a Great Use of Fuses.

It can be a bit of a Minefield with Fuses however, because Standard Fuses might rupture "after" a second of reaching their rating, a "Quick Blow" Fuse might Blow in a tenth of a Second, and Time Delay, Time lag, or Slow Blow type Fuses might carry a sustained "Over-Current" for a much Longer period after an "Overload Point" is reached. When you then "Add-In" the Variability of the Standards and Quality of the Manufacture of some of these Fuses, you will begin to understand my reluctance to be "Soley Dependant" on "Fusing" as the only means of Cutterhead Protection

After a few Failures trying to make a "Precision Rectifier" to use with the ACS Hall Effect Current Sensor, caused in part by a combination of failing eyesight, Poor Quality Solder, Oxidised Soldering Iron Tips et al... I moved onto making the Little Op Amp Comparator Board to "Test" the LED VU Meter Activated Cut-Out idea further. Another 2 "Non-working" further wasted Board Making efforts were later binned, before I got a result with Board number3, only to find I'd made the first "Successful" Comparator Board "Arse about Face"

I managed to get confused in a Long Forgotten World of "inverting and Non-Inverting" Inputs and Put my Reference Voltages and Trigger Voltages the WRONG WAY AROUND!!
Anyhows Op Amp Comparator Board Number 4 is working fine, and Seems to have overcome the "Little Problem" of "Partial LED Illumination" that I encountered when I was trying to drive the Transistor Base directly from the LED Cathode.

VU Cutterhead Protection Circuit Led Comparator Test.MOV

Grounding the Cathode of the LED (As I think the LM3915 VU Meter Chip Does) turns on the LED, reduces to zero the Input voltage to a Grounded Voltage Divider Circuit and thence the Comparator Input, the Reference Pin is therefore now Higher than the Pin that hitherto was reading the OC Voltage from the LED, thus the Op Amp output Falls to Ground and Turns Off the Transistor Base, which in turn Kills the Relay Carrying the Audio from the Power Amplifier to the Cutterhead PHEW!!! I think that expained the Principles of Operation, Remembering that the LEDs on the LM3915 Controlled VU Meter are "Graduated" into 3db "Steps" so a "Current Measurement Correlation" with these "Steps" will be one of the next challenges
Onwards and Upwards. The Experimentation Continues
Regards Soulbear

[Soulbear]

Soulbear wrote :-

"I managed to get confused in a Long Forgotten World of "inverting and Non-Inverting" Inputs and Put my Reference Voltages and Trigger Voltages the WRONG WAY AROUND!!
Anyhows Op Amp Comparator Board Number 4 is working fine, and Seems to have overcome the "Little Problem" of "Partial LED Illumination"that I encountered when I was trying to drive the Transistor Base directly from the LED Cathode."

With reference to the "Partial LED Illumination" I referred to in the earlier post, when I was trying to drive the Transistor base directly from the LED Cathode. Whilst having another look on the interweb while awaiting delivery of more Prototyping Stripboards due to needing more, because of the boards I managed to "Screw UP" I came across another "Alarm/Cutout Circuit" which exploits and utilises the LM 3915 "Step Function"

(And there I was, thinking I'd been creative and thought of something new!! WRONG!!)

Anyhows, in this Circuit, the problem I encountered is overcome quite simply by "Shunting the LED" with a High Value Resistor, the Transistor Base being energised via this "Shunt"

VU Cutterhead Protection Circuit-9.jpg

When the LM3915 Grounds the LED Cathode the "Shunt Resistor" is effectively bypassed by the LED and voila, "System Triggered" Wished I'd have thought about doing that!! Woulda saved a whole lot of Soldering "Cock-Ups" while making Comparator Boards, and quite a lot more of "Expletive Use" by yours truly into the bargain!!!!!

A little bit like finding that you did have the Taxi Fare Money in your Pocket, and did not have to walk home after all!! Ah well, too late now,to let these things irritate
The mission continues, Soulbear

[Soulbear]

Hi Trolls,
Well now, I've only made a little progress, because of many problems I encountered relating to making new Prototype Boards
Quote >>>>> :- "Poor Quality Solder, Oxidised Soldering Iron Tips et al..." I had thought to adapt a "Stageline VU Meter" I purchased many moons ago thinking that this might be easier.

Luckily for me, before I embarked on that course of action/destruction , the Mailman arrived with New Soldering Tips and "Lead Alloy" Solder!!!!

What a difference from the "Lead Free" Solder!!!! Yippee!!!!
Massively lower melting point, with the Lead Alloy and it flows much more readily, best of all, the soldering iron Tips did NOT Oxidise within 3 seconds of every time I made a connection!! So I went back and continued with the LM3915 VU Meter Board. Result

VU Cutterhead Protection LM3915 Board Test.MOV

For whatever reason I can not get a result with the ACS712 Module when trying to measure an AC input. A DC input works just fine, but with an AC Input Zilch!!! I'm in the process of buying some more LM337 Negative Voltage regulators to make another Symetrical Power Supply althought the one I made "Appears" to be Testing Ok!!! I thought I had a couple of these Symetrical Supplies already made by Cebek/Ceebek?? but can I find them????

I need to make a Correlation between the VU trigger and the Amperage into the Cutterhead and thought the ACS712 Module might offer the best solution. I am however still experimenting, and next on the Agenda is to Experiment and try and get a usable Analoge Signal using a HMCT103 by Passing the Amplifier Output to the Cutterhead, through the CT

Oh HUm!! The Work Continues
Best Regards Soulbear