Probably someone who wants lower acoustic distortion, Current-Drive - The Natural Way of Loudspeaker Operation.
I never said that. Read what I said again and this time try to comprehend it. I think there are some great tube amps,but they dont change the sound. And if the truth is condescending, ignore it, your problem.
Since most speakers are designed for voltage sources they are more acurate with voltage sources, which implies low output impedance. If you want your amp to be an EQ that is different with every speaker use a high output impedance one. This is realy the only point I was trying to make. Is it wrong? No. Then why all the flack? I thought people were here to learn. Guess not.
I guess we are talking about amplifiers on the fringe. SETs, SEPs, FirstWatt F1, F2, PP Pentode amps with little or no feedback, specifically designed amps like Rasmussen’s LM3875 current amp (really similar to Duo’s earlier TransAmp which had a control for dialing output impedance from near ero to near infinity, one based on LM3875 and one based on an amp originally designed to drive the electrodes in a CRT (it was batter). I have seen a couple reviews of current amps from eastern Europe, and at least one from Japan in the glossies, but the reviewers did not have a good hand on the system matching required.
Let me mention the ACA here. Say Rout is the output impedance of a single channel, then bridged it has Rb = Rout x 2 or if a set of paralleled channels, Rp = Rout/2 which makes it a cheap and interesting amp to play with.
On the speaker front, anything with real flat impedance curve (ie Elsinire Mk6) which won’t care what the output impedance or the amplifier is, or speakers with well behaved impedance curves where any deviation from flat is synergistic with the FR (as measured with a low R amp), which are trickier to get right (ie a Fostex horn such as Vulcan), or used over a limited bandwidth when biamping and over that bandwidth impedance is flat. The Heil ribbon has an almost ruler flat impedance.
Those are broad strokes.
dave
Sure, show some comercial speakers that are designed for current drive. Again the 1% is supposed prove a point.
Sure agree with all of that, but as you say tricky to get right. As oppossed to low output impedance amps and voltage drive speakers. Why do you think this has been the standard for at least 60 years? And your saying the same thing as me, they effect the freq response and therefore are EQs, and sure sometimes that EQ helps but its a crap shoot.
I’d have to do a deep dive for links, Indra1 has posted a good link on current drive (ESA also has a good thread here, i always find it hard to find).
There is a lot of SE tube stuff out there but often little understanding of the real meat is missing.
Some good stuff at Broskie's site but you are looking for a gem amoungst a pile of jewels.
Needs of current amps and of voltage amps are fairly clear, but getting the synergy right when Rout is nearish Rspeaker.
dave
Arent you arrogant. My understanding comes from an EE degree, designing electronics and 30 years working in recording studios listening to gear 8 hours a day. But I guess you know it all so goodbuy.
That is exactly true. Speakers with non-flat (ugly) impedance curves. But the rest does not follow, particularily if you are diying your own.
dave
No, i’m not. I am just stating a fact. Your knowledge of that particualr design space sounds like it is pretty high, but your very statements signify that you only understand a skim of the surface of knowledge of the larger design space that exists.
dave
99% is not all. This is DIY, we can do current drive, RePhase, REW and even motional feedback if we want. You can keep the nonsense, effects box, complete with all the distortion if you want, but some people will refuse your forcing it down their throat.
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Here is a graphic example, the same driver, but 3 different boxes designed with specific attention to the output impedance of the amplifier.
http://wodendesign.com/downloads/King-of-Swingers.pdf
dave
25 years ago I corresponded with an engineer who for a living designed switching power supplies - his journey took him from push pull tube amps with good transformers finally to a single ended tube amp. A banned member of this forum currently builds the Loftin-White variety SE with one gain stage and I trust his judgement as has built and heard many amplifiers with many different power supply variations.
here's a single ended parallel 2A3 amp with 5842Q front end I made about 27 years ago - I grew up with tubes such as Knight as EICO - so probably a bit biased
The world of front loaded full horn systems which may run 103dB upwards for 1 watt/1M can be tolerant and even subjectively shine with SE tube amplifiers.
I have heard very microphonic octal tubes in RIAA preamps.
Some tube power amps to me seem overly complicated and sonically compromised using multiple diff amp front ends and drivers.
With a cheap solid state amp and CDs, my autoformer volume control seemed to add a layer of subtle harmonics to a La Scala type setup - subjectively making the blend more cohesive.
Bass guitar amps such as the old Traynor YBA3 with sagging screen supply sound nice to me.
here's a single ended parallel 2A3 amp with 5842Q front end I made about 27 years ago - I grew up with tubes such as Knight as EICO - so probably a bit biased
The world of front loaded full horn systems which may run 103dB upwards for 1 watt/1M can be tolerant and even subjectively shine with SE tube amplifiers.
I have heard very microphonic octal tubes in RIAA preamps.
Some tube power amps to me seem overly complicated and sonically compromised using multiple diff amp front ends and drivers.
With a cheap solid state amp and CDs, my autoformer volume control seemed to add a layer of subtle harmonics to a La Scala type setup - subjectively making the blend more cohesive.
Bass guitar amps such as the old Traynor YBA3 with sagging screen supply sound nice to me.
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@dave - very interesting. So there's a box for <2.5 Ohm, ~2.5 and ~4. Here's my curiosity: If you measure the drivers T/S parameters using these various amplifier output impedances - instead of the 0.1 Ohm standard - do these box designs reflect the parameters obtained in that way?
In other words, if you know your amplifier output impedance, could you re-run the driver spec-sheet T/S measurements using that impedance - and then successfully design an enclosure around the new parameters? Is this what Scott did? (We didnt inadvertently reveal any secret-sauce; this is all common knowledge, right?
)
To physically see what the amplifier output impedance (damping) does to the enclosure to compensate, as shown in these drawings, is amazing.
I guess that goes to show you cant design an enclosure using manufacturer data and then just hook it up to any type of amplifier and expect the design's performance to be invariant.
Thanks! (Joe wants to see the Trans-amp design with that output impedance control!)
In other words, if you know your amplifier output impedance, could you re-run the driver spec-sheet T/S measurements using that impedance - and then successfully design an enclosure around the new parameters? Is this what Scott did? (We didnt inadvertently reveal any secret-sauce; this is all common knowledge, right?
)To physically see what the amplifier output impedance (damping) does to the enclosure to compensate, as shown in these drawings, is amazing.
I guess that goes to show you cant design an enclosure using manufacturer data and then just hook it up to any type of amplifier and expect the design's performance to be invariant.
Thanks! (Joe wants to see the Trans-amp design with that output impedance control!)
I'd just like to point out that I think loudspeakers are a horribly inadequate tool for comparing amps compared to headphones.
A good top end pair of headphones will be quieter, more detailed, and lower distortion than any speaker and most importantly they don't have any room characteristics to interfere, it's like being in an anechoic chamber with an audio microscope.
I prefer speakers for listening but for testing purposes I don't see how it can be beat.
I suspect a lot of anecdotes are contaminated by the many unwanted variables that loudspeakers bring.
A good top end pair of headphones will be quieter, more detailed, and lower distortion than any speaker and most importantly they don't have any room characteristics to interfere, it's like being in an anechoic chamber with an audio microscope.
I prefer speakers for listening but for testing purposes I don't see how it can be beat.
I suspect a lot of anecdotes are contaminated by the many unwanted variables that loudspeakers bring.
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I've just made a video concerning this subject - YouTube where I compare a homebrew valve amp to a transistor amplifier, but I recorded the OP from dummy loads. The result has been mucked about digitally obviously in order to upload it Utube but there is a slight discernable difference.
Andy.
Andy.
Headphone comparisons tell you nothing about the performance of amps into loudspeakers. It may hold some value about the sound of the VA part but that is also limited thanks to the complete lack of soundstaging headphones achieve.
Different worlds which don't mix very well.
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