FWIW, I am rebuilding an amp built by myself that said 'no more' a while back, and as simple as it is, the rebuild has become tiresome. Be nice to your amp. Put the lid back on with one way screws.
Nice way to destroy an amplifier.
Clearly said in post #12:
As of:
THAT.
63V rated caps already too close to the (reliability) edge , currently standing 60V
Mere swapping 120V primary for 110V tap will raise that to 65.5V , go figure.
For an inaudible power increase.
I can't believe you wrote that. If you're making jokes, please use a proper emoticon. Like this one --> 😛
Not only that. The power grid can vary at least 10% up and down. So, it can push the power supply voltage even more.
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60 V is too close to the rated 63 V for my taste. Now, we don't know what the mains voltage was when this measurement was taken. If it was the nominal 120 VAC mains, ±5% mains variation would push the caps to their rated voltage. ±10% mains variation (which is not uncommon in North America) would push the voltage past the rated voltage of the supply caps. I would have used 80 V caps.
Basically this amp is already maxed out. Don't push it further. If you want the supply caps to last, don't leave the amp on 24/7/365.
But hey... The BOOM! of the capacitors "expiring" catastrophically will be deafening. 🙂
Tom
Ha! Yeah. Weld it shut! 😉
In all seriousness: It looks like a quality build. Don't mess with it. Use it. Just don't leave it on 24/7/365 for the reasons mentioned above. But also don't be afraid to use it.
Tom
Replace that dinky little amplifier module with a couple serious modules wired in bridge. You need something with two (or 3) pair of 15A FETs and not one pair of 7A transistors. A serious amplifier has about 16 transistors.
However, I agree that 100W should be enough. Significant more power would be +10dB, ie 1KW. Are the speakers really that bad? +/-60VDC should give you over 200W into 8 Ohms, up to 800W from a bridged pair.
However, I agree that 100W should be enough. Significant more power would be +10dB, ie 1KW. Are the speakers really that bad? +/-60VDC should give you over 200W into 8 Ohms, up to 800W from a bridged pair.
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Raise the rails 5v for the pre driver section.
More outputs should be required. Max stress happens at roughly 60% of full power. In this case 225 watts into 8 ohms.
More outputs should be required. Max stress happens at roughly 60% of full power. In this case 225 watts into 8 ohms.
I’m not about to change anything on the amps , they are simply too good to fettle with , I asked the question.
A hundred watts is quite powerful.
Matched with some high efficiency speakers should be fine for home or small gigs.
I used 220WRMS amp and four Fane 12-50WRMS speakers for a mobile disco and that blew the roof off.
220W isnt much more than 100 watts loudness wise.
Remember you need 10 times as many watts to be twice as loud.
So next step up from 100 watts is 1000 watts.
Matched with some high efficiency speakers should be fine for home or small gigs.
I used 220WRMS amp and four Fane 12-50WRMS speakers for a mobile disco and that blew the roof off.
220W isnt much more than 100 watts loudness wise.
Remember you need 10 times as many watts to be twice as loud.
So next step up from 100 watts is 1000 watts.
Likely a follower output configuration (2sk on the positive supply), the Fet manages 100 watts at room temp, 7 amps max, at 12 VGS.
This means that of the 60 volts, approximately 48 can be delivered to the output, in 8 ohms around 150 watts.
The schematic would provide some insight into how precise these guesstimations are, but it should be enough for the speaker you're connecting it to.
This means that of the 60 volts, approximately 48 can be delivered to the output, in 8 ohms around 150 watts.
The schematic would provide some insight into how precise these guesstimations are, but it should be enough for the speaker you're connecting it to.
Sorry. I didn't see you were in the UK. So you're looking at 240 V +5/-15 % if I recall correctly. -15 % is no issue. +5 % would bring you right to the hairy edge of what the supply capacitors can handle - assuming you measured 60 V at the nominal 240 V mains.
As I mentioned earlier, I'm not suggesting you change anything. Only that I would prefer to see 80 V capacitors for better reliability. If the supply caps ever give up the ghost, replace them with 80 V types.
±60 V should result in 200+ W into 8 Ω. Is that really not enough for you? Bridging would result in 800+ W into 8 Ω. Bridging would also require a different power transformer as the one currently in the chassis was probably sized for way less than an 800 W amp. Same for the heat sink.
If the amp really "only" delivers 100 W from a ±60 V supply and you really, really want more power, I'd replace the amp module with one that makes better use of the available rail voltage. Then again, the difference between 100 W and 200 W is 3 dB, which is a little more than barely noticeably louder. As Nigel points out above, you need a 10 dB difference (10x difference) in power for the resulting SPL to be perceived as twice as loud.
Based on what measure of seriousness? A serious 10 W amplifier can easily run on a single pair of TO-220 devices.
The number of output devices depends entirely on how well the devices can conduct the dissipated power as heat to the heat sink. You'll need more devices if they're in TO-220 packages than you do if the devices are in TO-247 or TO-3P, so claiming 16 as the magic number for a "serious" amp seems rather arbitrary.
The devices used in the amp here seem like they were designed to dissipate some heat. Their rather beefy packages with two mounting screws seem to indicate this. We could check the data sheet...
Tom
Thanks for your input mate ( excellent )
I will NOT be changing anything in these wonderful monoblocks, they have clearly run reliably for almost 40 years so I doubt that the caps will give up now 😊.
So is 100w quoted by someone on here correct for the measured 60v ?
I will NOT be changing anything in these wonderful monoblocks, they have clearly run reliably for almost 40 years so I doubt that the caps will give up now 😊.
So is 100w quoted by someone on here correct for the measured 60v ?
Historically it was 240 -/+6%, then it changed in name only to 230v -6% +10%.
Guitar amps get a mention...
https://www.ampworks.co.uk/myth-bus...and-the-eu-and-what-it-means-for-guitar-amps/
If I’m reading this correctly….±60 V should result in 200+ W into 8 Ω
Then they are not 100w but 200w ? That is more than enough for the ATC’s .
Ah. You're right. I got the EU harmonization backwards.
I do recall that all that changed was the nominal voltage (220 -> 230 V for EU minus UK; 240 -> 230 V for the UK). The tolerances were redefined such that the old 220 V (±whatever) and 240 V (±whatever) would be covered by the new 230 V (±whatever) spec.
Tom
100 W could be a typo or it could be due to the topology of the amp.
Why not measure it? Run a 400 Hz sine wave into the amp and raise the volume until the amp clips. Then turn the volume down just enough that the amp provides a clean sine wave output. You can do this with a function generator and an oscilloscope. If you don't have a function generator, use this online one: https://www.wavtones.com/functiongenerator.php If you don't have a scope, plot the output voltage versus the input voltage as you increase the input voltage. You'll find Vout/Vin is a straight line until it hits a knee. That knee is when the amp clips. Take the last output voltage before the knee and do P = E^2/R. That'll give you the output power.
Ideally load the amp with an 8 Ω, 250 W resistor for this. If you don't have such a load resistor, you can measure the amp without load. It won't give you a very accurate measurement, but it should at least tell you whether the 100 W number is somewhat close.
Do note that if the amp is as under-designed as @steveu implies, you can end up frying the amp if you leave it running at high power levels into an 8 Ω load. Running the amp without a load won't break anything.
Tom