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Old 28th Feb 2021, 9:16 pm   #2121
Dickie
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Default Re: The Audiophoolery Thread.

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Originally Posted by slidertogrid View Post
Based on that do you think that an owner may have comeback on this amp because of the potential danger caused by mains wiring with no grommets ?

Its a long time since I was involved in CE certification but those mains conductors going through an earthed metal chassis without a grommet or other insulation would not meet the safety standard EN61010 and would thus not get CE approval.
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Old 28th Feb 2021, 9:47 pm   #2122
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Default Re: The Audiophoolery Thread.

This may well be contender for the most expensive 4 way mains block

in the world

https://nvahifi.co.uk/products/nva-b...-unit-bmu-1kva
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Old 28th Feb 2021, 10:10 pm   #2123
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Default Re: The Audiophoolery Thread.

The cover says "do not remove cover No user servicable parts inside"
Nothing to see here.................


Peter
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Old 28th Feb 2021, 11:22 pm   #2124
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Default Re: The Audiophoolery Thread.

Dodgy mains wiring, cabinetry glued together, earthing by hope.... and used in a room with a wetted floor?

We aren't in Kansas any more.

That sonic boom was the CE, UL, CSA, S+, BSI, etc marks getting the hell out.

David
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Old 1st Mar 2021, 12:30 am   #2125
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Default Re: The Audiophoolery Thread.

If it's anything like the NVA amp upthread inside, then "Do not remove cover" is to guard against jaws dropping and hearts stopping.
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Old 1st Mar 2021, 1:10 am   #2126
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Default Re: The Audiophoolery Thread.

Surely it was never possible to legally sell stuff like that?

Steve.
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Old 1st Mar 2021, 2:06 am   #2127
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Default Re: The Audiophoolery Thread.

I still cannot get over the fact that they used such cheap and cheerful "Suntan" branded capacitors. Obviously just built for maximum profit. ��
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Old 1st Mar 2021, 9:58 am   #2128
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Default Re: The Audiophoolery Thread.

I have come across boutique brands where the (let's be polite) 'ordinariness' of the components is explained by saying that inexpensive parts will always be somewhat compromised, but the designer has actually put an unbelievable amount of time and expertise into selecting them so that all the faults cancel one another out, opening up a near-miraculous gateway to audio nirvana. It makes it a real nuisance when, 20-30 years down the line, one of the electrolytics has gone pop and that particular range went out of production in the last millennium.

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Old 1st Mar 2021, 12:13 pm   #2129
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Default Re: The Audiophoolery Thread.

The strange thing about this is that despite it being badly built and using cheap standard parts it must sound good. I didn't test it with a signal as I quickly found the reason why it was crackling so I just ran it on a pair of test speakers which just by sheer chance had short separate leads. I now realise that was lucky as had I used some speakers with long flex the thing could have "hooted" and probably blown up.
Once I was happy the crackle had gone I disconnected it and stuck it back together.
The reason I say it must sound good is because whilst the purchaser cannot see inside it would have surely been demonstrated prior to purchase wet floor or not.. and surely the buyer would agree it sounded good enough to justify the price? I doubt the thing would be bought just for the "bling factor"?
When running with no signal I can say that it was silent, not a hint of hum or hiss. I had to buzz test the input to make sure it was working.
Thinking about it maybe with a good signal source the sound quality is more dependant on good speakers than the amplifier?
I am glad I posted this thread.. I have learned a lot about Hi-Fi !
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Old 1st Mar 2021, 1:00 pm   #2130
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Default Re: The Audiophoolery Thread.

I'd imagine replacing those Suntan capacitors with something approaching quality would improve the sound - or at least the longevity of the amplifier.
A few weeks ago i had a valved bass preamp in for repair. I'd assumed it was a power amplifier because of the big valves and heavy transformers. But no, it's a £1500 preamp. It had a dry joint, and came with several pages of repair notes while someone had spent five hours trying to find it. On opening it I could see why. It's point-to-point wiring, tagstrips and all at crazy angles. "Everything is soldered by hand in Santa Cruz, California" boasts the blurb proudly. "There are no circuit boards". However, after soldering everything is held in place with hot-melt glue. The components are top quality and the soldering excellent. But I don't think I found the dry joint either.
The owner is selling it.
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Old 1st Mar 2021, 1:42 pm   #2131
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Default Re: The Audiophoolery Thread.

Looking at the circuit boards on the photos in post 2097 it looks like the transistors around the centre of the board run hot as the board is discoloured. As it is mounted upside down the heat will rise and cook the board and in time will make the solder joints fail. Leaving on all the time will help it to fail even quicker. There are many noticeable poor solder joints visible in those photos, but then maybe wrapping one wire around another to make a good mechanical connection before soldering might cause unwanted sound effects.
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Old 1st Mar 2021, 2:15 pm   #2132
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Default Re: The Audiophoolery Thread.

I am fairly sure that the mantra of "leave it switched on so that all the parts are at operating temperature for best/most consistent quality etc etc" is no longer preached by most and usually the advice you'll get is "give it 30 minutes to warm through". That does make a little bit of sense to me as by then the resistors etc will be at a steady temperature and the equipment will be about as stable as it ever would be?
I admit to being one of those who would leave the hifi switched on back in the 80s when this was the flat earth gospel and I hadn't any more sense. But being of a suspicious nature I tried using the stereo without this recommended precaution and shockingly I found out I had been wasting electricity.
As to the 30 minutes warm up, I have a theory that the psychological effect of sitting down, getting oneself relaxed and in a receptive frame of mind may have more to do with this than any other factor.

I can remember the first impressions of NVA from their ads and reasoning when I stumbled across them in the earlier days of the web. And I remember thinking what the heck is this all about? And Why would anybody hermetically seal the workings of an amp in a perspex case with no easy way to access for servicing or inspection unless they really did have something to hide.
Told you i was suspicious.
Andy.
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Old 1st Mar 2021, 2:29 pm   #2133
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Default Re: The Audiophoolery Thread.

Doug Self's view is that if a solid state amp takes more than 5 to 10 minutes to stabilise there is something very questionable in the design.

Valved gear takes somewhat longer, but half an hour is the maximum you need. Unless you are into single ended class A, which does time time for the magnetics to heat up and stabilise to deliver the 5 to 9W of 1% distortion output

I forget on which forum, or whether it was a private mail from someone who left their valved gear on 24/7 on the basis that valves were at their most reliable when permanently switched on. I pointed out that he was spending well over £200 a year in electricity, plus the cost of replacement valves. Don't know if it had any effect.

Craig
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Old 1st Mar 2021, 2:59 pm   #2134
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Default Re: The Audiophoolery Thread.

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Originally Posted by Craig Sawyers View Post
Doug Self's view is that if a solid state amp takes more than 5 to 10 minutes to stabilise there is something very questionable in the design.

Valved gear takes somewhat longer, but half an hour is the maximum you need. Unless you are into single ended class A, which does time time for the magnetics to heat up and stabilise to deliver the 5 to 9W of 1% distortion output

I forget on which forum, or whether it was a private mail from someone who left their valved gear on 24/7 on the basis that valves were at their most reliable when permanently switched on. I pointed out that he was spending well over £200 a year in electricity, plus the cost of replacement valves. Don't know if it had any effect.

Craig
When the Post Office engineer Tommy Flowers was proposing the design of a valve computer for Bletchley Park, he was told valves were not reliable enough for use in very large numbers as there waould always be at least one faulty. He replied they were only unreliable when filaments were turned on and off. Left on continuosly, he was vindicated. I imagine the electricity bill was irrelevant in the context.

I take the comments in a domestic context as reasonable of course.
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Old 1st Mar 2021, 3:08 pm   #2135
bikerhifinut
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Default Re: The Audiophoolery Thread.

Quote:
Originally Posted by Craig Sawyers View Post
Doug Self's view is that if a solid state amp takes more than 5 to 10 minutes to stabilise there is something very questionable in the design.

Valved gear takes somewhat longer, but half an hour is the maximum you need. Unless you are into single ended class A, which does time time for the magnetics to heat up and stabilise to deliver the 5 to 9W of 1% distortion output

I forget on which forum, or whether it was a private mail from someone who left their valved gear on 24/7 on the basis that valves were at their most reliable when permanently switched on. I pointed out that he was spending well over £200 a year in electricity, plus the cost of replacement valves. Don't know if it had any effect.

Craig
I hope his fire insurance was paid up!
My take on this is, apart from wasting juice and a big stereo Amp using KT88/6550 in pushpull is a greedy beast that makes a nice supplementary heat source, and wearing out Valves that will cost a minimum of £200 for a matched quad, is that even the best built and designed amplifier can suffer a critical component failure and if that leads to any form of pyrotechnic valve failure or smoking parts under the hood, you can at least yank the plug out of the mains socket sharpish as long as you are in the room with the amp.
I guess even solid state can have its moments too but mercifully usually not as dramatic as that.
This has happened to me, by the way, when a small grid stopper resistor failed on a cathode biased output EL34 and in the few seconds from realising there was a fault to seeing the affected valve get almost white hot I managed to pull the mains plug. I wasn't going near the on off switch on the amp!

Andy.
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Old 1st Mar 2021, 3:09 pm   #2136
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Default Re: The Audiophoolery Thread.

Many guitar amps have a standby switch which just runs the valves' heaters. You let them get to temperature before giving them HT. This seems a good idea in theory.
At Uni, I remember going to check on the Students' Union PA system used for general address through the building. The mike was duly repaired, but I was surprised on looking in the cupboard to see an amplifier boasting four happy KT88s. No-one could remember it ever having been switched off in well over ten years - and it hadn't gone wrong either!
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Old 1st Mar 2021, 3:17 pm   #2137
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Default Re: The Audiophoolery Thread.

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Many guitar amps have a standby switch which just runs the valves' heaters. You let them get to temperature before giving them HT. This seems a good idea in theory.
At Uni, I remember going to check on the Students' Union PA system used for general address through the building. The mike was duly repaired, but I was surprised on looking in the cupboard to see an amplifier boasting four happy KT88s. No-one could remember it ever having been switched off in well over ten years - and it hadn't gone wrong either!
I bet they were proper GEC MOV KT88s, Modern production seems to have a definite lifespan, but the original ones have a legendary reputation, not so much for any perceived sound quality (That I guess would be a suitable topic here!) rather than their longevity.
But they are tough Valves.

Andy
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Old 1st Mar 2021, 3:17 pm   #2138
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Default Re: The Audiophoolery Thread.

The Quad II valve amp was sometimes used in factory PA systems and railway station announcement racks. Apparently these were rarely, if ever, powered down. In the winter the heat reduces the demand on whatever other source of heating you're using, so the electricity cost is not 100% wasted. But in warmer weather it is, and the gradual loss in valve emission is a cost too.

Cheers,

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Old 1st Mar 2021, 4:17 pm   #2139
Craig Sawyers
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Default Re: The Audiophoolery Thread.

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Quote:
Originally Posted by Craig Sawyers View Post
Doug Self's view is that if a solid state amp takes more than 5 to 10 minutes to stabilise there is something very questionable in the design.

Valved gear takes somewhat longer, but half an hour is the maximum you need. Unless you are into single ended class A, which does time time for the magnetics to heat up and stabilise to deliver the 5 to 9W of 1% distortion output

I forget on which forum, or whether it was a private mail from someone who left their valved gear on 24/7 on the basis that valves were at their most reliable when permanently switched on. I pointed out that he was spending well over £200 a year in electricity, plus the cost of replacement valves. Don't know if it had any effect.

Craig
When the Post Office engineer Tommy Flowers was proposing the design of a valve computer for Bletchley Park, he was told valves were not reliable enough for use in very large numbers as there waould always be at least one faulty. He replied they were only unreliable when filaments were turned on and off. Left on continuosly, he was vindicated. I imagine the electricity bill was irrelevant in the context.

I take the comments in a domestic context as reasonable of course.
Indeed that is absolutely true about Tommy Flowers and Colossus. I worked for a while as a volunteer restoring a cipher machine at Bletchley, and for several days was ensconced at a desk behind the rebuilt replica Colossus - on the side of the rack that had the thyratron counting rings. I absolutely roasted!

Back when the original five Colosusses (Colossi?) were running in WW2, the machine operators were ladies. And to survive in the heat from them, particularly in Summer, they used to strip down to knickers and bra. The gentlemen code breakers used to draw lots to decide who brought the intercept punched tapes in for the ladies.

Of course original valves for Colossus are really rare now, so to power the thing up the heaters are gradually warmed on one of the largest Variacs I've seen. Once the heaters are up to operating temperature, the HT is brought up. It is run most days to entertain visitors, (when Covid was not an issue of course), so maybe 40-50 hours a week - which is still pretty good going. Valve failures are fairly uncommon as a result of kid gloves powering.

Of course it is not a general purpose computer - its architecture was to break the Lorenz SZ42 codes - basically a valved DSP.

Craig

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Old 1st Mar 2021, 4:20 pm   #2140
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Default Re: The Audiophoolery Thread.

Well some of the Audiophoolery, if somewhat muted? seems to me to have started when my latest acquisition was built. A very poorly Leak Stereo 30 which must have spent the last 40+ years in a shed. It is full of Germanium only transistors and what a mix, OC44, AF118, AC107, AC127 and a pair of AD140 output transistors. Mr. H.J. Leak demonstrated it as a high quality transistor amplifier giving indistinguishable results from his valve amplifiers. (Was he trying to say his valve amps were not the best?)
"The amp incorporates over 60dB of negative feedback to reduce all forms of distortion to vanishing point"
It's a shame that this amp is in such a bad shape but I am tempted to get it going by all means possible just to see how good (or bad) this amplifier really is. I mean the sound stage could be incredible and I may be tempted to junk all of my valve amplifiers.
It is full of those horrible little Red Electrolytic's and carbon composition resistors so it won't be cheap to try to get it back to its claimed superiority over valves, or am I dreaming? But the adverts of that time say it all.
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