Leaving the amp on 24/7 Is it ok?

[Craig Sawyers]

All down to  Arrhenius for semiconductors.  And electrolytic capacitor life about halving for every 10C temperature increase. Not counting infant mortality.  And thermal shock every time it is turned on.

So in this context, what do you mean by MTBF?

Edited April 15, 2016 by Craig Sawyers

[DefQon]

Quote

MTBF (mean time between failures) is a measure of how reliable a hardware product or component is. For most components, the measure is typically in thousands or even tens of thousands of hours between failures. For example, a hard disk drive may have a mean time between failures of 300,000 hours.

 

Edited April 16, 2016 by DefQon

[grawk]

I am pretty sure Craig wasn't looking for the definition, given what he wrote.  He was pointing out that the question wasn't particularly condusive to a useful answer.

[DefQon]

Ah true. Didn't catch the last bit of his post.

[astrostar59]

Most capacitors have 1000 hours at either 85°C or 105°C unless they are for special applications. I wonder what the temperature at the capacitor on the power supply of a Carbon (for example) sit at in normal operation. The heat sinks would be say 20°C above ambient, so maybe 45°C but the capacitor sat on a PCB some distance away would be much lower I suspect, maybe 35°C. Thus a long life should of 10,000 hours be pretty much expect.

The life of any electrical component is not just the heat in operation, there is the cooling down and warming up when switched on and off and the 'thermal shock'. Plus a surge of electricity on switch on. It is possibly why some amplifier manufacturers recommend leaving it on 24/7?

[johnwmclean]

The capacitors are not in contact with the heatsink therefore not going to be anywhere near those temps.

[Craig Sawyers]

Easy thing to check with a thermocouple for anyone with a carbon or kgsshv.

The caps in the KG-T2 probably get pretty toasty, but that animal drags ~200W out of the mains, the transformers run hot, and there are two massive heatsinks along each side of the case that also get hot.  So although I have not measured the temp of the reservoir caps I suspect that they get pretty hot through association with their surroundings.  But noone is gong to leave the T2 on for much longer than you are listening; I let mine warm up for an hour (two max).

[astrostar59]

Hi All

Anyone heard this commercial KGBH? Looks nice but no idea how good it is built.

http://www.fluxlab-acoustics.com/Products/18

 

[Craig Sawyers]

I sure hope they are paying Kevin a royalty on sales.

The Sowter (UK, Ipswich) attenuation transformers used are really good though, and very well thought of.

[spritzer]

They didn't even ask for permission to use the circuit so yeah.... 

[DefQon]

Looks very nicely built.

[grawk]

Can you tell it's nicely built without seeing the bottom of the board?

[spritzer]

Indeed and obscured heatsinks are a terrible idea. 

[johnwmclean]

Translation:

Amplifier for true music lovers! This model is the evolution of development already well-proven design amplifier for electrostatic headphones-KGBH. Author of circuitry solutions is a great enthusiast of electrostatic sound-Kevin Gilmore. Inspired by the legendary amplifier STAX SRM-T2, he applied in its development of semiconductor amplifier similar to the balanced output stage arrangements. It is possible to obtain high output signal amplitude at low distortion and wide band audio signal.
This model meets with two types of volume control. The base variant of the regulator is an attenuator relay type using signal relays Fujitsu Takamisawa touchpad Japanese version "Analog"-is a high-quality attenuator transformer type. Amp attenuators are used in the construction of the English company Sowter, and to switch findings from transformers use regulator precision rotary switch Swiss company Elma.
Also in the configuration with the transformer pad appears able to use this model as a passive pre-amp.
Technical characteristics
Frequency response: 
5 Hz-100 kHz -0, 1dB 
0Gc-180kGc-3dB 
10 Hz-120kGc-3 DB (Analog)
Total harmonic distortion: 0.01% <
The output signal amplitude: 1600w (peak-peak)
Gain: 60dB
Standard bias voltage: 580V (Pro)
Input connectors: XLR (two inputs), RCA (two entries)
Supply voltage: AC 230 v, 50/60 Hz
Power consumption: 180W
Dimensions: 440 mm (w) 325 mm (d) 180 mm (in) excluding the height of the lamps.
Weight: 16 kg 
Applied electronic lamps in the amplifier:
4pcs. EL34 (6CA7)

[Craig Sawyers]

7 hours ago, spritzer said:

They didn't even ask for permission to use the circuit so yeah.... 

If it isn't the Chinese plagiarizing products it is the Russians.  In a business meeting a year ago or so, the visiting guy had been shown the inside of a unit in China where they had a team of 200 whose job was to decompile embedded code, FPGA code, ROM contents etc of Western products.  We don't stand a chance in hell against that level of industrial scale ripping off.

[astrostar59]

20 hours ago, johnwmclean said:

The capacitors are not in contact with the heatsink therefore not going to be anywhere near those temps.

Ok, that is good news then.

[spritzer]

3 hours ago, Craig Sawyers said:

If it isn't the Chinese plagiarizing products it is the Russians.  In a business meeting a year ago or so, the visiting guy had been shown the inside of a unit in China where they had a team of 200 whose job was to decompile embedded code, FPGA code, ROM contents etc of Western products.  We don't stand a chance in hell against that level of industrial scale ripping off.

It is truly shocking how far they go with this stuff.  Kevin and I are seeing it as they now have our version of the KSA-5 for sale, complete unit which really doesn't give me a warm and fuzzy feeling.  From now on I'll never release board files for the final optimized version of something. 

On this note though I had a stroll through Aliexpress and they are ripping off a lot of stuff.  Full Dartzeel clones in the same livery and everything. 

3 hours ago, astrostar59 said:

Ok, that is good news then.

I for one only use high life caps though it is a struggle to keep stuff small while doing that.  The main PSU caps usually have a lifetime of 3000hr at 105°C (some more than that) and they run at less than 50°C so at least 10000hr of life in them. 

[Craig Sawyers]

30 minutes ago, spritzer said:

From now on I'll never release board files for the final optimized version of something. 

I'd do it somewhat differently - release final Gerbers, BOM etc but only to those on the list who are (a) trustworthy (by some criterion like long term, regular contributors, no newbies etc (b) agree formally not to release to a third party.  Something like that might be workable and prevent blatant commercial design duplication.

Probably achieve nothing other than satisfaction, but why not send a letter to the Russians who are selling the BHSE.  Also I know Brian Sowter - I am sure he would be devastated to know that he is supplying his attenuator transformers to someone ripping off the hard work of someone else.

[spritzer]

I might also sell the boards but it's not really something I'm interested in doing.  It might work out later on if I step up production and can leverage that into cheaper boards.  We'll see

[Craig Sawyers]

14 hours ago, spritzer said:

Indeed and obscured heatsinks are a terrible idea. 

From a purely thermal management point of view - absolutely, 100%.  

But from the product safety perspective to CE or UL, the general rule is 25C above ambient (to max ambient of 40C and external part temperature of 65C) for touchable anodised casework - and an external heatsink counts as casework.  So most manufacturers of power hungry audio gear now put the heatsinks inboard.  Like Krell and Emotiva - but not interestingly Mark Levinson who still put their heatsinks on the outside and don't bother to certify for external temperatures.

[joehpj]

6 hours ago, spritzer said:

It is truly shocking how far they go with this stuff.  Kevin and I are seeing it as they now have our version of the KSA-5 for sale, complete unit which really doesn't give me a warm and fuzzy feeling.  From now on I'll never release board files for the final optimized version of something. 

Copied means you are good.

You really can't stop people doing reverse-engineering. There are all kinds of copies all over the world not limited to Taobao. B22, Dartzeel, HA5000, Rudistor, ML amps....

The best copy of Dartzeel was even a 1:1 pcb copy, because they bought a brand new one to rip apart.

So, my point is, if there's market, there's copy. It's simply different market for those who bought a genuine Dartzeel or a copied one. I for one hate copy cat but there's really nothing we can do. (at least now)

[Dusty Chalk]

3 hours ago, joehpj said:

Copied means you are good.

You really can't stop people doing reverse-engineering. There are all kinds of copies all over the world not limited to Taobao. B22, Dartzeel, HA5000, Rudistor, ML amps....

The best copy of Dartzeel was even a 1:1 pcb copy, because they bought a brand new one to rip apart.

So, my point is, if there's market, there's copy. It's simply different market for those who bought a genuine Dartzeel or a copied one. I for one hate copy cat but there's really nothing we can do. (at least now)

That doesn't make it okay, and it doesn't mean you should just give up on trying to protect your IP. 

[Craig Sawyers]

^This

[spritzer]

Indeed.  Kevin has a much more Zen approach to this but then again, I'm the hothead...   

[justin]

On 4/9/2016 at 2:38 AM, Craig Sawyers said:

This is the reason that Krell went over to some sort of dynamic biassing scheme, because running flat out class A was just not reliable.  I had a late model KSA100 that demonstrated that perfectly.  Typical Krell battleship construction, with superb engineering, and two fan cooled heatsink chimneys.  Power transistors were rebranded as KrellA and KrellAA.  It blew up three times in my ownership - same symptom each time, power transistors going into second breakdown failure accompanied by lots of smoke.  Lat time it happened was after I had sold it on eBay for quite a lot of money.  The buyer was actually on his way to collect from about 150 miles away - and I thought I'd turn it on so he could listen to it.  Major league failure with plumes of smoke; phoned him in the car, apologised profusely and he went back home.  This time it had taken out the drivers too, and the associated driver load resistors had ignited and burned part way through the board.

Replaced the sand, using generic high power transistors and NOS obsolete drivers.  Dremelled out the char and coated with conformal coating before replacing the load resistors. Worked perfectly, and the guy honoured the sale, paid the money after auditioning and off he went leaving positive feedback.

I've also seen the same generation of KSA50 ignite too.

But it is all down to component stresses - high power class A puts a combination of high voltage and high current through the power devices all the time.  Smoothing caps and power transformers likewise need to be carefully thought about, since they are running flat out all the time too.  But non-linear distortions, including induction distortion are much lower than class B or AB, which is why high end users like it.

i was on my way to buy a Krell SACD player when the owner dropped it. This must be a Krell problem

On 4/17/2016 at 4:06 PM, astrostar59 said:

Hi All

Anyone heard this commercial KGBH? Looks nice but no idea how good it is built.

http://www.fluxlab-acoustics.com/Products/18

 

i think this has actually been around for quite a while. The company is, or was, buying teflon Stax jacks from me so i had an idea of how many they were building. 

Someone who paid 5k for a BHSE 5 years ago could turn around today and sell it for 5-6k. 

That will not be the case for this amp. In case of repairs it would also be sent to Russia which from my experience, about 20% of packages never make it to delivery - a major reason why I stopped shipping the jacks directly to Russia