Those are the residual mains hum components. Just to be clear. The overall noise is noise level integrated over (~added up across) the audio band. But yeah... 0.5 uV of mains hum is unheard of in other amps. Some of that comes from my lab setup. I'm running the MOD686 naked on a heat sink. No chassis.
Tom
The base of all references here is post #245
From that post one can deduct more things:
1M FFT, 8 averages, ~-142dBV noise floor, -125dBv spuries from hum,
measured / stated 31.uV total integrated noise (supposedly 20-20kHz)
-125dBV spuries >> 500nV > .5uV power line originated noise hum level
31,5uV in ~20kHz bandwith gives 31,5uV / sqrt(20kHz) V/sqrtHz spectral power density.
that is -133dBV noise floor --- before averaging.
Noise is adding quadratically, so 8 times averaging gives sqrt(8) times lower noise floor, that is 9dB lower noise floor.
-133 dBV (before avg) -9dBV (of avg) = -142dBV visible noise floor.
(I did this above calculation to show that the declared/ measured noise is in agreement with the graphs)
-133dBV = ~220nV noise spectral density.
The amp gain is declared to be 26dB = 20.
The input referred noise density for this amp is 220nV/sqrtHz / 20 = 11nV/sqrtHz
Ciao, George
From that post one can deduct more things:
1M FFT, 8 averages, ~-142dBV noise floor, -125dBv spuries from hum,
measured / stated 31.uV total integrated noise (supposedly 20-20kHz)
-125dBV spuries >> 500nV > .5uV power line originated noise hum level
31,5uV in ~20kHz bandwith gives 31,5uV / sqrt(20kHz) V/sqrtHz spectral power density.
that is -133dBV noise floor --- before averaging.
Noise is adding quadratically, so 8 times averaging gives sqrt(8) times lower noise floor, that is 9dB lower noise floor.
-133 dBV (before avg) -9dBV (of avg) = -142dBV visible noise floor.
(I did this above calculation to show that the declared/ measured noise is in agreement with the graphs)
-133dBV = ~220nV noise spectral density.
The amp gain is declared to be 26dB = 20.
The input referred noise density for this amp is 220nV/sqrtHz / 20 = 11nV/sqrtHz
Ciao, George
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One note about the Wakefield phase-change heat sink pads. Since they activate with temperature, the datasheet points out that one must not expose them to high temperatures in shipment and storage. For those who live in hot climates, you don't want to store in a garage and may not want to order from Mouser during the summer months when they might sit in a hot delivery truck for most of the day.
Note also that the phase change is activated by heat, so to properly 'seat' them you need to crank up the volume. ;-)
Note also that the phase change is activated by heat, so to properly 'seat' them you need to crank up the volume. ;-)
That's a very good point, actually. Mouser also will not ship these using ground shipping.
True. Though the back side of the IC reaches the phase change temperature (60 ºC) rather quickly, so I suspect the ICs will seat within a few minutes of the first power-up. Of course for the best thermal performance, you'll have to get the heat sinks up to 60 ºC.
I think I'll keep looking for a good thermal pad. The Wakefield CD-02-05-264 is nice. The Bergquist K10 is good too. It would be nice to find something that is a little better than K10 but isn't quite as finicky as the phase change materials.
Great numbers so far Tom, about PSU for the discerning customer can you make them a version with two more 686 modules configured as a floating DC voltage regulator to steer PSU output free of any pico volts grass
Ha! Yeah. That's pretty funny. I'll introduce you to a North American idiom: "Putting ten pounds of sh!t into a five-pound bag." I think this qualifies.
Actually on a sorta related topic: The LM3886 is remarkably useful in many applications. One could easily set up an LM3886 for PSRR/line regulation testing of LDOs for example.
Tom
Phase shift pads are a PITA if you have to reposition things. Need isopropyl or other solvent to clean up, plus you have to remove when warm, or risk breaking your device (dont ask how I know....)
Try the Keratherms....Love them on Class A First Watt builds...
Keratherm Transistor Insulators – diyAudio Store
Try the Keratherms....Love them on Class A First Watt builds...
Keratherm Transistor Insulators – diyAudio Store
It's nice material indeed. You can see the data sheet here: http://www.kerafol.com/fileadmin/us.../01-standardfolien/Datenblaetter_TM_86_82.pdf
Tom
Tom
Yeah. I took a closer look at the DIY Audio Store photo, which revealed the little punch-outs for the holes.
A little larger than I'd like, but large enough to cover the LM3886 and the additional length is easily trimmed off. $19 for ten is a pretty good deal.
Tom
This smps power supply could be interesting and convenient, being dual voltage (only a module is necessary):
SMPS500QRv2 | Connex Electronic
For european customer Audiophonics sell it already customized at +/- 35V:
SMPS500QRV2 500W / +/- 35V Switching Power Supply Module - Audiophonics
SMPS500QRv2 | Connex Electronic
For european customer Audiophonics sell it already customized at +/- 35V:
SMPS500QRV2 500W / +/- 35V Switching Power Supply Module - Audiophonics
Sadly, the Connex supplies (and Hypex too) are rated in "music power". Their "500 W" supply is actually only a 160 W supply as it's intended for use in a 500 W Class D amp and assumes a 10 dB crest factor.
Connex's "800 W" (= 250 W RMS) SMPS800RE would work for a single channel. So you'll need one custom SMPS800RE (±35 V is a special order voltage) and one MOD686 per channel.
Note that the SMPS800RE product page mentions that if the supply needs to deliver high power for an extended period of time, it should be fitted with a fan. There's no mention of how much power the supply will deliver without forced air cooling.
The Mean Well RPS-400 series is similar in that it requires forced air cooling to get the maximum output power. But at least Mean Well specifies the supply at convection cooling as well, so you know what you're getting.
I have nothing against Connex and have no ownership in Mean Well. However, I generally prefer to buy products that have actual specifications.
Tom
Connex's "800 W" (= 250 W RMS) SMPS800RE would work for a single channel. So you'll need one custom SMPS800RE (±35 V is a special order voltage) and one MOD686 per channel.
Note that the SMPS800RE product page mentions that if the supply needs to deliver high power for an extended period of time, it should be fitted with a fan. There's no mention of how much power the supply will deliver without forced air cooling.
The Mean Well RPS-400 series is similar in that it requires forced air cooling to get the maximum output power. But at least Mean Well specifies the supply at convection cooling as well, so you know what you're getting.
I have nothing against Connex and have no ownership in Mean Well. However, I generally prefer to buy products that have actual specifications.
Tom
Also the Connex info is unclear on the maximum line input voltage. One place says 127VAC, another says 130V, and yet another says 120V. Input above the max (which one?) can damage the supply, they say. When I lived north of Seattle, the Snohomish County PUD considered 120V to be the absolute minimum a customer should ever see. The nominal line voltage at our house was 130 and could go higher. Didn't make for long light bulb life and could have been bad for a Connex.
As Tom said, it's good to have real specs. The Connex is an appealing concept if only the specs were a bit more solid and perhaps a bit more robustness overall.
Note: There are smaller MeanWell units in the RPS series that might be a good match to the smaller Modulus amp models -- lower power output (and price) as well as lower output voltages
As Tom said, it's good to have real specs. The Connex is an appealing concept if only the specs were a bit more solid and perhaps a bit more robustness overall.
Note: There are smaller MeanWell units in the RPS series that might be a good match to the smaller Modulus amp models -- lower power output (and price) as well as lower output voltages
For sure many of the specs declared are not so clear.
However reading this http://connexelectronic.com/wp-content/uploads/2017/09/SMPS500QRv2.pdf
You can read: total output power 500W, peak output power 700W when used for audio amplifier with crest ratio of 3
Main output current: nominal 8A, peak 11A
No need of fan
I will ask them informations about all these ...
However reading this http://connexelectronic.com/wp-content/uploads/2017/09/SMPS500QRv2.pdf
You can read: total output power 500W, peak output power 700W when used for audio amplifier with crest ratio of 3
Main output current: nominal 8A, peak 11A
No need of fan
I will ask them informations about all these ...
Compare and contrast with Mean Well who gives you an actual data sheet.
Wow. When I lived just south of Seattle, I had 122 V mains and quite a few brownouts despite the fact that the transformer feeding my house was in my front yard. By happy coincidence, the line voltage today in Calgary is 122 V as well.
Funny. I was looking at that yesterday. A pair of RPS-200-24 would make a really nice supply for a MOD86.
Which makes me nervous when I'm combining their supplies with multiple $300 amplifier boards.
First off, 11 A peak is not enough for a Modulus-686. The '686 can deliver 33 A (typical). With a 4 Ω resistive load, it'll deliver 15-16 A peak to the load near clipping. So forget the SMPS500, please.
The potentially interesting supply in the Connex lineup is the SMPS800RE ($120 with custom ±36 V output voltage). The "Additional Information" tab on the SMPS800RE product page says, "Cooling fan: No, Yes". What does that mean? Schrödinger's Cooling Fan? The product description says: "For operation inside a tight case, an optional variable speed cooling fan is available, which should be used when the Power Supply delivers high power for long periods of time." What's considered a "tight case", "high power", and "long periods of time"? The "data sheet" reveals more information: "When the SMPS800RE is installed into an enclosure where the ambient temperature might rise above 50 ̊C, a cooling fan should be used to keep the power supply temperature at safe levels." The "data sheet" also introduces more ambiguity: "Note that when the power supply is working in burst mode due to low load, or no-load, the LED light might dim as well as the mains soft start relay might click ON-Off due to insufficient load on the output, especially when minimum voltage was set at no load." There's no mention of what constitutes a "low load" or the minimum current required to make the supply work properly. Is the 350 mA drawn by the MOD686 sufficient? It would rather suck if the supply started to cycle on/off during quiet passages in the music.
Last I dealt with Connex, it took them about a month to respond to my pre-sales inquiry (Do you have any in stock, how long does it take to ship, etc.). I knew from chatter here that they took a while to respond and I wasn't in a rush. Once I ordered the supply, it took about two weeks to arrive - which met my expectations. I proceeded to load test the SMPS300RE, which is how I discovered that drawing 250 W RMS from their "300 W" supply caused the supply to fail.
Now the good news is that Connex's post-sales and customer support response time was much, much faster. They responded within a day to my "your stuff broke" email and were very accommodating. The supply was pretty easy to fix. The dual diode on the secondary had blown, so I just bought a new one and the supply has worked well since then.
As I've said before, I do not have an axe to grind with Connex. Christie, the owner, seems to be an honest guy and I found his post-sales customer service to be excellent. His pre-sales support is lacklustre and I doubt you'll get an answer to your questions. Then again, he could have improved or chosen to hire employees to help with the questions. I hope he succeeds.
My specific concerns with Connex are:
- Response time on pre-sales correspondance.
- Availability of products.
- Lack of specifications and ambiguity in the specifications.
- No mention of EMI standards met or tested to.
I will continue to recommend the Connex SMPS300RE for the Modulus-86 as I've tested that in reality. I don't mind pointing people to the SMPS800RE for the Modulus-686, but will also point out that I have not tested that solution and am not planning to do so.
I am confident enough in the performance of Mean Well's products to recommend their RPS-400-36 and EPP-400-36 for the Modulus-686. You'll need two of these supplies in series to form ±36 V to power one Modulus-686 channel. The EPP-400-36 is $70/each at Mouser, so two of them will be $20 more than a ±36 V Connex SMPS800E supply. Mouser has four in stock and I can have them on my doorstep within one business day with free shipping.
Alternatively, I am currently working on a Power-686. Figure Power-86 with twice the capacitance, surge suppressor, soft start, and a small +5V SMPS aux supply (Mean Well IRM-series). The +5V will be used to control the power-on relay and an optional protection (over-temperature, output DC, etc.) board that I'll develop as well. The whole point is to have a solution which is as close to plug-n-play as I can get with a transformer involved. Should be pretty nice. I expect it to be available sometime in May (this year
).By all means ask Connex about the SMPS800RE. I'm certainly interested in what they have to say.
Tom