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Old 11th June 2012, 07:45 PM   #6111
Pano is offline Pano  United States
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According to my analog meter typical listening is done @ less than 10volts rms. with only the occasional peak exceeding , ok' speaker load is 1 ohm from 350hz-22k ,
You're running 100W average level if your meter is accurate. That's a lot for a domestic setting. A 1 ohm load means a lot of current. It's no surprise you need an amp with a big power supply. And amp rated at 400W/4ohms might give you enough voltage, but only that big power supply will give you the heavy current your speakers need. You need an amp you can weld with.
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Old 11th June 2012, 07:48 PM   #6112
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Agree Sy of too few words, could you expound a bit more ...
See the Red Light District article on my website.
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Old 11th June 2012, 08:01 PM   #6113
tvrgeek is offline tvrgeek  United States
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See the Red Light District article on my website.
Could you hit me with a link? I need to get back to finish my RLD takeoff on a Meng. I want to contemplate it a lot more after the "schooling" I got in this forum on amps in general. I also have an old HK A300 that probably has much better transformers and may result in a decent amp.
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Old 11th June 2012, 08:03 PM   #6114
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Duck! Incoming!

The Red Light District: A 15W Push-Pull Amplifier

Since publishing this, I've made a few changes- higher plate voltage (410V), lower idle current (35mA), yielding over 22W per channel. the overload recovery is not compromised.
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Old 11th June 2012, 10:13 PM   #6115
a.wayne is offline a.wayne  United States
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Quote:
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You're running 100W average level if your meter is accurate. That's a lot for a domestic setting. A 1 ohm load means a lot of current. It's no surprise you need an amp with a big power supply. And amp rated at 400W/4ohms might give you enough voltage, but only that big power supply will give you the heavy current your speakers need. You need an amp you can weld with.
Big current not voltage , avg is closer to 6volt rms, peaks is what exceeds 10volt ...I maybe able to get away with 25volt

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See the Red Light District article on my website.
Ok, will have to modify my browser it blocks any article below 50 watts
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Old 11th June 2012, 10:39 PM   #6116
tvrgeek is offline tvrgeek  United States
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Duck! Incoming!

The Red Light District: A 15W Push-Pull Amplifier

Since publishing this, I've made a few changes- higher plate voltage (410V), lower idle current (35mA), yielding over 22W per channel. the overload recovery is not compromised.
Wow, I doubt my transformers can do 22. I get about 6 out of it right now with 6P1's. Thanks. Gives me some good reading. I have to remember where I left off as I have built about 4 amps in that chassis. Got to re-read Jones so I can get Self out of my head. But than again, that's not a bad idea anyway.
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Old 11th June 2012, 10:55 PM   #6117
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This may pain you to find out, but Jones has copies of all of Self's books and thinks quite highly of him.
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Old 11th June 2012, 10:56 PM   #6118
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Recently Sony has been one of my un-favourite brands . I should have known better as Sony has often caused me troubles in the past .

Years ago I was forced to buy one of their big amps . It was a disaster . The rated power was considerably over 100 watts ( 175 ? ) . Hi Fi choice decided to do a new test of burst power into 1 ohms ( about 1983? ) . The NAD3020 managed to give 92 Watts , the Sony 2 Watts . That answered the doubts I had .

If completely penniless buy 2 x NAD 3020 and use one as a pre amp and the other as a power amp . Buy 3 and have monoblocs . Early ones are best .

Proton who made the 3020 also made their own version with posh transistors . It was not as good .

I often use a 3020 pre amp to do power amp tests . It has always surprised me and beat many expensive designs . I had an Audio Research once . Although better than a 3020 it wasn't as large a difference as I expected . Funny thing is a NAD was what I always said was just about OK to judge a front end with ( LP12 for example ) . I grew to like the 3020 more as time went on . I suspect speakers became more suited to NAD or it to them as time went on . EPOS ES14 a notable good combination . I have Nordost off cuts , I make them into NAD bridging conductors for friends ( Silver plated OFC for mains use ) .

Best ever surprise amp was to me Rational Audio a Check Republic design . I suspect it is these people below who made it ? It eat a Naim NAP 250 for breakfast into Linn Isobariks ( a noted difficult load ) . The amp in question was about 30 watts .

Krell with Isobariks was remarkably ( Jimmy Hugues with DNM pre amp when I visited one day ) . Surprisingly well suited and monster loud . Which for KEF units is unusual .

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Old 11th June 2012, 11:21 PM   #6119
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This may pain you to find out, but Jones has copies of all of Self's books and thinks quite highly of him.
Hear, Hear.
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Old 12th June 2012, 07:02 AM   #6120
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Wayne, the short and curly of it is that when you have a decently done say 200 WPC amp, the ACTUAL say 50W it will be asked to deliver will very likely be more stable and less stressing for it than the same from a say 100 WPC amp.

Key word is "likely". It does not HAVE to be so, but in practice, due to mostly economic and marketing reasons, it very often is so. Should the manufacturer of a say 80 WPC amp decide to endow it with a full electronic regulation, then this will most probably NOT be so, and in fact, you might find that the lesser power amp plays better music.

Once upon a time, there was a small time operation called R.E. Designs, somewhere in the greater Boston area, run by a great guy and an excellent engineer called Dan Baquer. He made just one power amp, a nominally 80 WPC amp, which used two pairs of 250 W devices in its output (sic!) and had a fully regulated power supply. By listening to it, you would think the amp was more like 200 or 300 WPC - absolutely stable, rock steady imaging, and lots of it.

Unfortunately, Dan had a double family vrisis related to health and was forced to go out of business, but he did transfer all his copyrights to me, and I will produce both the original version and an enhanced version of it (DC coupled, servoed). But the first jury rigged version was way more than convincing, there's no doubt in my mind that he got it right and then some.

Because of the added complexity and parts, obviously that amp will need to cost more than its similar bretheren, but my feeling is that it will outplay them hands (er, transistors) down.

SY has a point. Solid state circuits in most audio gear that I have seen do not often consider the problem of overload recovery. And that is not something to be toyed with. But that's only one of several points one needs to consider.

This is one of the reasons why over the last 25 years, I have never made an amp which did not have separate power supply lines and which were not fully electronically regulated for the voltage gain amp and the predriver at least. Not that I made many of them, but I did follow this logic very consistently and will continue to do so.

And if your speakers do have an "impedance" of 1 Ohm, which is almost a short ciruit, then you do need an amp of heavy proportions capable of powering a welding iron.

As for protection circuits, I beg to differ. I have seen far too many amps which were wasted altogether, while their "protection" fuses remaind intact. But there's no doubt that one needs to be very careful with such ciruits, because they have a conflicting job to do, to protect the amp but to be non-intrusive right up to the very last stand position. That's why I make mine stay passive until the impedance drops to 1.8 Ohms, and even so to first stay passive for a short period in case that's only a transient.
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