Panasonic A400

For the three and more legged things
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Paul Barker
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#31

Post by Paul Barker »

Neal wrote:No one has mentioned feedback yet ;)
I really liked the Rosenblit 6080 OTL which was loaded with feedback. That do you?
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Dave the bass
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#32

Post by Dave the bass »

I think everyones looking at it from the wrong direction....! Ergo, I'm really chuffed that our amps made from old stuff screwed to bits of wood sound nearly as good as professionally designed Japanese manufacturing standard commercially available consumer units.

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#33

Post by pre65 »

Dave the bass wrote:
sound nearly as good


DTB
Shame on you Bass. :wink: :lol:
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#34

Post by Cressy Snr »

Neal wrote:No one has mentioned feedback yet ;)
Or output stages using two or more elements, or class A/B, or device characteristics similar to pentodes. :lol: :lol:

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#35

Post by pre65 »

Do I remember reading somewhere that mosfets had "valve like" characteristics ? :)

Before I got into "valves" I had an urge to get a pair of Maplin 50W mosfet modules and build a power amp. Did anyone here actually use them ?

Perhaps Mike H will remember them. :lol:
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#36

Post by Mike H »

Paul Barker wrote:Thanks.

I think it is the damping factor more than the power.
Yes I was going to say.
Neal wrote:No one has mentioned feedback yet ;)
I was. :lol: Which where the damping comes from, massive open loop gain then NFB.

Nearly 30 years ago I was using infinite baffle speakers that I made with a 100W per channel Pioneer integrated, was going to get into porting but they worked so well with the Pioneer as they were, I never bothered. Completely useless for a valve amp though, which just couldn't subdue the excessive resonances.
 
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#37

Post by Mike H »

pre65 wrote:Do I remember reading somewhere that mosfets had "valve like" characteristics ? :)
Insofar as have behaviour basically same to pentodes. But as far as it goes I think.
Before I got into "valves" I had an urge to get a pair of Maplin 50W mosfet modules and build a power amp. Did anyone here actually use them ?

Perhaps Mike H will remember them. :lol:
Yes I do. Tried making a pair but couldn't stop them RF oscillating. Mind you I hadn't got the proper PCB's, which had a very specific track pattern in the area of the output stage to prevent such parasitic oscillations. Gave it up in disgust. Still got the MOSFET's somewhere.
 
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#38

Post by Paul Barker »

I think this amp is just BJT's isn't it?
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#39

Post by Lee S »

Inside of an AU719 showing dual PSUs, one per channel and also some info regarding the design. These things seemed to be at the peak of their game in the late 70s and early 80s.
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Nick
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#40

Post by Nick »

One more go, I wasnt trying to make any point, or have any dog in this race. I was just pointing out that if the amp Paul was comparing it to was the F5, then that is a highish damping factor, feedback, mosfet output amp.

F5, Damping factor 40
A500, Damping factor 100

Not a huge difference. So I was just pointing out we dont know what else was used in the comparison. So the F5 has a source impedance of 200mOhm, the A500 80mOhm, to the point where I can imagine speaker cables and connectors covering up the difference.

I was not questioning that Paul heard a difference, and had a preference, but if we are using that information to create a narrative where "amp A is better than B because of X", its worth knowing what other differences are present we don't know about before declaring what X is.
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#41

Post by Ali Tait »

Bring it to Owston Paul, it'll make an interesting comparison.
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#42

Post by Paul Barker »

Nick wrote:One more go, I wasnt trying to make any point, or have any dog in this race. I was just pointing out that if the amp Paul was comparing it to was the F5, then that is a highish damping factor, feedback, mosfet output amp.

F5, Damping factor 40
A500, Damping factor 100

Not a huge difference. So I was just pointing out we dont know what else was used in the comparison. So the F5 has a source impedance of 200mOhm, the A500 80mOhm, to the point where I can imagine speaker cables and connectors covering up the difference.

I was not questioning that Paul heard a difference, and had a preference, but if we are using that information to create a narrative where "amp A is better than B because of X", its worth knowing what other differences are present we don't know about before declaring what X is.
Absolutely. And also just because I have an experinec doesn't mean everyone elses system and for that matter their ears will have the same experience. but I am allowed to report my experience. And I wish more others would relate theirs. people seem spo scared to anounce things these days for fear of being shot at as in this thread.
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#43

Post by Paul Barker »

Didnt tell Diana what I was doing. Played some music through the PASS amp. Sounded good, spreads out into a soundstage very well, bass appears to be controlled, tone of singers seem to be very good. Diana sat doing something and saying nothing unaware I am AB comparing.

Then switched to Pioneer. Played a few tracks thought to myself the clear difference was deeper bass better control of bass and lighter top end with more HF extension, but not nearly as 3 dimensional. so the PAss amp is superior on in your face leap out at you in depth.

But then I played the same female vocal track again. Diana broke silence saying "Oh that's Lovely".

It is like this. The Pass amp is very very good at what it does. The Pioneer is more correct and wins hands down on tone of voice and bass.

Obviously on my speakers with my cables in my house to my ears in the mood I am in right now at this one atmospheric pressure.

The difference to me can better be explained in the following paragraph. When I first ever plugged in the Panasonic I was imediately emotively involved with what it played. When I got that Pass amp out again today I was reminded of why I don't normally listen to it, and would much rather have a valve amp. The pass amp is artificial, though it is a an excellent imitator of a valve amp and some of it's elements are superior in this respect to the panasonic. The paanasonic is better at voices and at extremes.

To sum up why the Pass amp never stays connected up for very long. Listener fatigue.

The Panasonic has not yet given me listener fatigue.

I hope that helps somebody out there. If it offends anyones pet ideas that wasn't my goal. It was to share an experience with open minded people.
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#44

Post by Nick »

Inside of an AU719 showing dual PSUs, one per channel and also some info regarding the design. These things seemed to be at the peak of their game in the late 70s and early 80s.
I have repaired one of those, they are good amps, the DC coupling means that if you look at it the wrong way it (a big transient will do it) it will kill its output transistors.
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#45

Post by Paul Barker »

Ali Tait wrote:Bring it to Owston Paul, it'll make an interesting comparison.
I don't mind doing that but personally I am not particularly interested in how it performs at Owsten and I won't be bringing these speakers to Owsten as the room kills them.

It is easy enough to bring.

What the heck for £40 it's an absolute bargain. I think someone said it has some nice component choices. Maybe worth buying broken ones for the components to use in other projects, if they are of the values we can use. I can assure you the components are making a great sound.
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