DIY Audio....or how many solder burns have you had?

[Macca]

Hi Tony

Thanks for the comprehensive replies.

Regarding Class A amplifiers my point is the small number in circulation added to the fact that they are only switched on when in use means their contribution to emissions isn't worth considering. Likewise cost in use, at least for a little one like mine, is pretty much negligible. (I maybe get about 6 hours a week on mine).

I don't claim any advantages in sound quality compared to other amplifier classes. I am thinking about getting a Class D but only to get much higher power output. But it probably won't happen since I'm not sure I really need it anyway.

What were you using at Cranage? Belles? Which model was it? (In truth I'd rather have those TAD loudspeakers).

Regarding SMPS, well as I said I use one for the DAC, I don't perceive any problems. If it ain't broke....

[Barry]

only very, very few clients are specifying class 'a' designs these days for a multitude of reasons one being the physcial size, the weight of the unit, the power consumption and sheer heat they generate.

Lets look @ your Krell KSA50S it takes pretty much 345Watts of power @240Vac at idle which is roughly 450Va which for a quoted genuinely 50W class 'a' device is on the money at more realistic volume levels this isn't going to rise to much as the devices (FET's) are 100% duty cycle as in on permanently all of the time.

So, in 20 hours you will have used 0.35 of Kwh x 20 so around the 7Kwh @ the capped rate of 0.34p per Kwh gives you £2.38 for the amplifier total electrical use (plus whatever the rest of the system uses in that period) so compared to a EV being charge at bollock charge between £40-£70 yes its relative indeed.

A class a/b amplifier is around 55-65% efficient so you could reduce that outlay by a further 25-30% and with a class 'd' style amplification by at least 100%, this is not about which one sounds better purely on consumption.

Also you have a small amplifier in terms of most of the current class 'a' units which are out there, recently visited a cleint who use the older big krell mono's with the meters on them, you could literally wtach the electric meter jump to warp when he switched them on.

Although the big Gryphon Colosseum’s idle around 3.2Kw each and double up as house heaters but do sound superb.



Personally class 'a' has never worked for me, plenty of others yes most are overly safe and somewhat nice which is why the big fad for class 'a' was kicked off in the mid 80's due to the slew of forward, hard sounding glut of average solid state amps but a multitude of manufacturers.

One of the reasons why I stopped using the Mark Levinson ML-2 monoblocks (into Quad 57 ESLs). They are big, heavy, very inefficient and run hot (so much so, the black anodising of the heat sinks had started to bleach).

In theory class A amplifiers can never be more than 50% efficient. The ML-2s are true Class A designs, wherein the mean audio output power doubles for each halving of the load impedance. Specifically the ML-2 provides 25W into 8Ω; 50W into 4Ω; 100W into 2Ω, and 200W into 1Ω - that is, provides a constant rms voltage of 20V, although given the power supply current capacity of 7A, the power into 1Ω should be taken cum grano salis. The power consumption from the mains (described as "idling" power consumption) is "around" 400W, or 8x the audio power into 8Ω, that is an efficiency of 12.5%.

So for the Krell KSA50S 50W/channel amplifier, the idling power of 345W implies an efficiency of 29%; more than double that of the Levinson design.

I now use a pair of Quad 510 monoblocks (or a pair of 'monoblocked' Quad 405 amplifiers (upgraded to Keith Snook level 3) and with improved power supplies). Whilst legend has it that the combination of Levinson ML-2 amplifiers with the Quad ELS was a "match made in heaven", I can say that the replacement of the ML-2s has not resulted in a degradation of sound quality.

[Puffin]

I built a Class A Pass F2 about 10 years ago and that ran as hot as a very hot thing!. At the time I used it with a pair of monster BLH (Back Loaded Horns) with either Fostex or Lowther FR units. The F2 was 5w per channel with a massive linear supply. Of the Pass amps I have built in the last year the ACA Mini a Class 5w "power house" is by far the best and if you could tell it was only 5w I would give it to you! It gets quite warm but the heatsinks are so small it's effect on global warming is negligible IMO. If you can get to hear one you would be amazed at the SQ. Cost of build including PCB and quality parts was £120. Power supply was £30 (SMPS)

[Mr. C]

Barry

From the majority of my experinaces here with this amplifier technology, its around the 35% mark for class 'a' efficiency, not having looked at a great many manufuctures 'a' class models. Although one or two do dip below the that efficiency point to obtain big power numbers, hence why the heat sinks are way over the top!

That is exactly the power consumption coming out of the wall this morning after 15 minutes 'warming up' time lol I also measured the idling of a Puresound A30 class 'a' 30 watt valve amplifier those was 272W @ idle zero load.

Another method would to calaculate the heat loss, a thermal camera can come in handy here, just check the top cover for constant temprature see how many are over 55C

The last class 'a' design I was involved with was absolutely rock stable @ 98Wrms into 4 ohms @ 290W Rms @ 1 ohm from a claimed 30W rms unit with 1.04% distrortion. Ultra low impedances right across the frequency spectrum and a very robust power supply.

Apologies about the table layouts

Output Impedance (re. 10.0W into 8ohm @ 1Khz and 20Hz it was still producing over 53Wrms) =

0.004ohm @ 20Hz 0.004ohm @ 21Hz 0.004ohm @ 23Hz 0.003ohm @ 26Hz
0.003ohm @ 30Hz 0.004ohm @ 33Hz 0.004ohm @ 37Hz 0.004ohm @ 42Hz
0.004ohm @ 47Hz 0.004ohm @ 53Hz 0.004ohm @ 59Hz 0.004ohm @ 66Hz
0.004ohm @ 74Hz 0.004ohm @ 83Hz 0.004ohm @ 94Hz 0.004ohm @ 105Hz
0.004ohm @ 118Hz 0.004ohm @ 132Hz 0.004ohm @ 149Hz 0.003ohm @ 167Hz
0.003ohm @ 187Hz 0.003ohm @ 210Hz 0.003ohm @ 236Hz 0.003ohm @ 265Hz
0.003ohm @ 297Hz 0.003ohm @ 334Hz 0.003ohm @ 375Hz 0.003ohm @ 420Hz
0.003ohm @ 472Hz 0.003ohm @ 530Hz 0.004ohm @ 590Hz 0.004ohm @ 670Hz
0.004ohm @ 750Hz 0.004ohm @ 840Hz 0.004ohm @ 940Hz 0.004ohm @ 1060Hz
0.004ohm @ 1190Hz 0.004ohm @ 1330Hz 0.004ohm @ 1500Hz 0.004ohm @ 1680Hz
0.004ohm @ 1890Hz 0.004ohm @ 2120Hz 0.004ohm @ 2380Hz 0.004ohm @ 2670Hz
0.004ohm @ 3000Hz 0.004ohm @ 3360Hz 0.004ohm @ 3780Hz 0.004ohm @ 4240Hz
0.004ohm @ 4760Hz 0.005ohm @ 5300Hz 0.005ohm @ 6000Hz 0.005ohm @ 6700Hz
0.005ohm @ 7600Hz 0.006ohm @ 8500Hz 0.006ohm @ 9500Hz 0.007ohm @ 10700Hz
0.007ohm @ 12000Hz 0.008ohm @ 13500Hz 0.009ohm @ 15100Hz 0.010ohm @ 17000Hz
0.012ohm @ 19000Hz 0.013ohm @ 21400Hz 0.016ohm @ 24000Hz 0.018ohm @ 26900Hz
0.021ohm @ 30200Hz 0.025ohm @ 33900Hz 0.030ohm @ 38100Hz 0.036ohm @ 42700Hz
0.042ohm @ 47900Hz 0.050ohm @ 54000Hz 0.059ohm @ 60000Hz 0.069ohm @ 68000Hz
0.079ohm @ 76000Hz 0.089ohm @ 85000Hz 0.099ohm @ 96000Hz 0.108ohm @ 100000Hz


We can measure ANY attribute on the incoming a/c mains both single and three phase and calculate pretty much what ever you you wish for. We have four methods of doing this via various test equipment. This morning I used the Tektronix PA3000 which is accurate to 0.04% after warm up, has some nice features like start up current measurment, idle power over time, draw charactoristics over time, transient repsonce etc.

We also have the R&D scope Teledyne Lecroy Wavepro which has a full power analysis suite and even three phase vector plotting/ harmonic & spectrum analysis at the same time. Gain accuarcy of 0.5% due to a 12 bit Adc scope

However I draw the line at paying £500 for a UK mains break out box, so I built my own lol!

If you guys wish to check this yourself, then the item in the last image is a great way for sensible money to enable you to perform these measursments you can use a normal multimeter providing it's CAT II rating or above and a simple hall effect current clamp to go around the squares in the device cost is about £30 from memory










Industry explanation

[majex45]

An engineer I worked with suggested rubbing instant coffee on iron burns. It works, a bit.

[struth]

An engineer I worked with suggested rubbing instant coffee on iron burns. It works, a bit.

green coffee beans ground very fine is supposedly the best for serious burn wounds.. dunno about instant tho.

never tried it tho