Chris,I did say mediocre rather than crap,but I would say that PP kt88 amps are not really my cup of tea either.Much nicer triode connected! :)
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Chris,I did say mediocre rather than crap,but I would say that PP kt88 amps are not really my cup of tea either.Much nicer triode connected! :)
HAHA... Aye, I'll remind you of that, wee man, when you've come down and heard the Copper amp in its natural habitat! :lol:Quote:
I would say that PP kt88 amps are not really my cup of tea either...
:ner:
Marco.
naa,Quote:
Originally Posted by Ali Tait
KT88's dont make very good triodes, KT66 are much better.:eyebrows:
Marco' regarding AE1's i think they work bloody well with high powered valve PP amps
the guy who run's V Audio in Bristol (ad in hifi world) confirmed this for me.
Good thread ..
feed back is a good subject, when you read the mullard enginers work from the 50's one would think an amplifier would be substandard without it
most modern push pull/ pentode amps are based on those circuits, so need feedback to operate
but there is a down side to feedback..
and it starts with your speakers..
so i'll start with your speakers..
if you connect a voltmeter onto a speaker( just the driver) and vibrate the cone in and out (its also a dynamo?) you can easily create 1/2 a volt or so.... so, if its moving at its real speed.. whats the voltage created? close to the signal thats moving it..?
next... the complicated sinewave that is the music signal, the height of the wave is volume, the length is frequency..
The speakers goal is to act on, and move the speaker cone to replicate that sine wave.. yes..
but none do....
transient attack is the speed the cone follows that sine wave, and effeciency(loudness) is the height achived by the speaker cone movement relative to the height of the sine wave.. ( that explains why hi eff are louder and follow that signal more.. think about that one...)
so now.. on the speakers wires.... there is the music signal voltage...and the signal thats created by the speaker not keeping up with the signal..
two different, yet very similalr voltage sinewaves, the latter more dependant on the speakers and associated components.
with the mullard type amps, global feedback is used ( nearly all amps use global) ... to put that simply, there's a tap from the speaker wire that feeds a portion of that signal back into your power amp input,
so a portion of the signal from the speaker wires is mixed with the source signal.... not a big portion of the amps output, but a large amount compared to the input or source signal that it mixed with
so..
the 'level' of feed back dictates how much signal goes back ito the amp,
and the speakers themselves are affecting the signal through the amplifier !!
The amount of distortion the amp is making at higher volumes is also fed back into the 'pot'...
These affects are only slight in most cases, usually a thinkening of the sound, giving a little more body to the presenation.. but it also takes away the finer details and the sweetness or musicallity that is maybe in the source
so many 'high' feed back (usually solidstate) amps, in use, can thicken the combined signal up, often resulting in a (futher?) lack of detail and a thicker (more solid ) sounding.. slightly false output...
now.. it is obvious to me that speakers and amps need to 'suit' each other
and very good results can be had with many combinations of all types of kit,
but don't forget all is not what it seems
think of a ducati V twin sound.. an impresive boom.... boom..... boom ...
but its not really..it just sounds like that.. its really boomboom...... boomboom......
many would say.. who cares it sounds good...
and there's nothing wrong with saying that about your hi fi too.. is there ?
steve
I don't think i mentioned this but i also had way back in the good old 90's a pair of Quad 2 mono's completely rebuilt and re badged as concordant exultant quad 2s they were lovely sounding and i had the option of either using GE kt66 or 6550 both very different but the amp was more suited to classical than rock , they sounded amazing with ESL57's a friend had at the time.
Anthony,yes you're right,kt66 is better.I like triode sound,45 is my favourite valve so far,but alas not enough power for my statics.813 is the best compromise I've heard so far,along with Nick's A2 211. I like my statics far too much to change them,so am stuck with the need for a bit of power. Steve,this back emf thing has been talked about before,but I hear the same sound with a PP amp on my statics,so I guess it can't all be down to that.What do you think?
Marco,yes I haven't forgotten!Yes your amp has huge amounts of headroom,and there is no shortage of "balls" but I still prefer se.I like the 813 amp(triode connected) because it gives me the se sound,but also has the authority of a PP amp.I also need a bit of power to drive my statics.It all comes down to personal taste....
nice one steve.Quote:
Originally Posted by SPS
when trying to explain feedback, i often akin its affects to a shock absorber on a car,[bear with me] if you took all of the shocks off your car the ride would be fine untill you hit a bump, then it would bounce from the affect of the bump and continue untill it gradually stopped [eventually] this i atribute to the damping factor in a power amp, now, put back the shocks, and when we do the bump thing the after shocks are damped, and the bouncing stops almost as fast as it started, now uprate the shocks and you get even more control over the stopping and starting, but as the shocks get harder it begins to have an adverse affect on the springs ability to absorb the shock in the first place, ie, it takes more effort to move the spring in the first place.
so just to clarify,,, i relate the spring to the speaker, the shocks as the damping factor acheived by the negative feedback, and the after shocks as the back emf produced by the speaker.
hope this makes sense.
anthony...
quite agree Ali, it not all down to that, there are many variables.. as you know..Quote:
Originally Posted by Ali Tait
but...if you hear the same sound with push pull, why do you prefer your se amp?
steve
hi ali,Quote:
Originally Posted by Ali Tait
i agree, the 45 is a great little valve, also the 813 can give excelent results in the right circuit.
anthony...