No they don't. If I designed a preamp I would put a buffer after the volume pot. Why? Because I have already decided to introduce an extra item in the audio chain (for some reason or another, good or bad) and as I already have a case and a power supply it does no harm to add a buffer just in case it might one day be useful. Doing something which is probably unnecessary cannot be taken as proof that it is necessary. This is your logical fallacy.east electronics said:
Good circuit design. A buffer after the pot potentially does more good than a buffer before the pot. Ending a preamp with just a volume control is poor engineering. Omitting the preamp and just having a volume control is good engineering.
So according to DF96 hundreds of manufacturers included buffers in their amplifiers just for fun and no obvious reason or since they had all the peripherals like housing , space and power supply
And according to Df 96 anything that has a preamplifier inside should vanish from the market and give its position to passive preamps only
Are you serious ????
I wonder if we both come crossed again in a thread that the discussion is VI limiters ...What will happen ? word war III ???
And according to Df 96 anything that has a preamplifier inside should vanish from the market and give its position to passive preamps only
Are you serious ????
I wonder if we both come crossed again in a thread that the discussion is VI limiters ...What will happen ? word war III ???
Did I say "just for fun"? Caricaturing your opponent's position instead of addressing it is a good way to avoid an issue.
Readers will search in vain for the post where I said that such preamps should vanish from the market.
I am, but I didn't say anything like what you allege I said. Why not address the issue, instead of getting all worked up by things I didn't say?
You are acting like someone who sells preamps for a living, and is worried that his market is about to shrink when people learn that preamps are mostly unnecessary. As I don't read Greek I have no way of telling whether this is true or not. My apologies if all your living comes from power amps or repairs alone.
DF96
at east electronics we repair an average of 1000 audio devices per year that means that after almost 30 years of operation we have seen pretty much everything every possible combination you can imagine and from every school you can imagine American UK Japanese vintage, 2000 ,90's ,now days, name it and have done it and listen to it
Could you please explain where do you stand from ?
A term like ""does no harm" does not apply either in consumer nor in hiend equipment In consumer since its adding cost and in hi end since in the signal path ...
So excuse me for rushing into a conclusion but this is what you said more or less ...
I dont sell preamps for living i just said that having an active one improves the performance in low listening level obviously with some cost That simple ....
at east electronics we repair an average of 1000 audio devices per year that means that after almost 30 years of operation we have seen pretty much everything every possible combination you can imagine and from every school you can imagine American UK Japanese vintage, 2000 ,90's ,now days, name it and have done it and listen to it
Could you please explain where do you stand from ?
A term like ""does no harm" does not apply either in consumer nor in hiend equipment In consumer since its adding cost and in hi end since in the signal path ...
So excuse me for rushing into a conclusion but this is what you said more or less ...
I dont sell preamps for living i just said that having an active one improves the performance in low listening level obviously with some cost That simple ....
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That is too general a statement, MAY improve would be more reasonable, but even that depends on the details of what is being driven.
Remember that if a 10K control is backed off 20dB or so, the source impedance may well be less then 1K even without a buffer.
You buffer when driving external interfaces (On the principle of being conservative in what you generate), or if for some reason you need a lower impedance then you have to drive a downstream stage, both of which are sensible uses otherwise you don't bother.
One good reason for a buffer before a volume control, is that getting the high pass RC pole down well below 20Hz (Ideally below 2Hz, to avoid phase shifts in the audio band) requires much less coupling cap when the impedance is hundreds of K ohms then it does when the impedance is 10K, and that means you can use small film or C0G coupling caps rather then honking great elcos (Which are a problem for the marketing guys).
Often the opamp and good quality small cap is very much cheaper and more compact then some honking great 10 or 100uF in an audiophile approved dielectric.
Regards, Dan.
It is this "low listening level" criterion which I dispute. Nothing different happens at low level, apart from a reduction in nonlinear distortion. Potential dividers work perfectly well at all levels from noise level up to the point where thermal effects start to be significant. A circuit either needs a buffer or it doesn't. At very low levels a buffer may do more harm, by adding noise.east electronics said:
An unbuffered volume pot driving an interconnect cable can produce a variable HF rolloff. This HF droop is at its worst at -6dB (almost full volume), not low level. Why this obsession with low level?
Why you are calling my statement obsession ??? or my need if you like
There is listeners that will have a huge variety of needs : one may like power, one may have difficult speakers to drive , one may have babies at home and he likes to have all the information within the first 0.5W
Point is i think that you cannot reject an approach by saying that this is right and this is wrong ( this is what you did ) let us not forget that every manufacturer will approach a variety of targets and doing this with his own means .
People that like to have small systems as co workers in the office while also need the best available quality in low listening level either for home use or for work use is a big part of the market .
In the repair business i found very strange that people invest money to upgrade small and old amplifiers we actually do plenty of those ...some stupid stuff quasi complementary single rail supply and capacitor coupled no more than 15-20W .
Obviously we ask our costumer WHY they invest so much money in such stupid amplifiers clearly outdated from any aspect . The answer was common
In low listening levels with sensitive speakers these amplifier produce rich and full sound and plenty of harmonics ( which is another issue ) and are ideal for that as a secondary system for 24/7 listening as described above
Same costumers often own very expensive main systems ....
There is listeners that will have a huge variety of needs : one may like power, one may have difficult speakers to drive , one may have babies at home and he likes to have all the information within the first 0.5W
Point is i think that you cannot reject an approach by saying that this is right and this is wrong ( this is what you did ) let us not forget that every manufacturer will approach a variety of targets and doing this with his own means .
People that like to have small systems as co workers in the office while also need the best available quality in low listening level either for home use or for work use is a big part of the market .
In the repair business i found very strange that people invest money to upgrade small and old amplifiers we actually do plenty of those ...some stupid stuff quasi complementary single rail supply and capacitor coupled no more than 15-20W .
Obviously we ask our costumer WHY they invest so much money in such stupid amplifiers clearly outdated from any aspect . The answer was common
In low listening levels with sensitive speakers these amplifier produce rich and full sound and plenty of harmonics ( which is another issue ) and are ideal for that as a secondary system for 24/7 listening as described above
Same costumers often own very expensive main systems ....
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let me try to simplify my thought to see if we can get somewhere
In the input of one amplifier exist a pot so the input at full level is 47K above ground and at low listening level is just a few ohms above ground
Anyone expects that the circuit will have the exact same behavior in dynamics in both conditions ? I think not
that is why you need to have the pot behind the buffer and make sure that amplifier input is always 47K above ground
is that easy to understand ?
Farther more i expect both configurations to play the same from a certain level and above only the second one will include some amount of noise, distortion, and anything else introduce by the preamp in the signal path .
is it better to understand now ?
In the input of one amplifier exist a pot so the input at full level is 47K above ground and at low listening level is just a few ohms above ground
Anyone expects that the circuit will have the exact same behavior in dynamics in both conditions ? I think not
that is why you need to have the pot behind the buffer and make sure that amplifier input is always 47K above ground
is that easy to understand ?
Farther more i expect both configurations to play the same from a certain level and above only the second one will include some amount of noise, distortion, and anything else introduce by the preamp in the signal path .
is it better to understand now ?
did i spelled costumers the wrong way ? English is not my native language sorry ...
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I think so. Anyone who knows anything about circuits will know that the electronic behaviour in 'dynamics' will be exactly the same. Adding a buffer will make no difference whatsoever. You clearly have some deep-seated misconceptions about audio electronics.east electronics said:
Most of those are receivers or integrated amps which have additional gain either for a phono-stage or have one built in.
FWIW, I wondered about the input impedance of power amps for many of the reasons discussed here, so I measured a few. Admittedly not a lot, but for the usual arrangement of diff input stage the way most people do it, the input impedance is remarkably flat with frequency over the whole audio band.
The ramification of that is they can be driven by a fairly high impedance with no response penalty. The 10:1 rule of thumb you often hear has no basis in fact. Score 1 for passive preamps.
Self talks about signal to noise ratio and pot values in his small signal book It seems that s/n ratio is limited by higher value pots, but you can do far better than is commonly done by using a decent opamp driving a lower-than-normal resistance pot. Since we now have opamps that can drive 600 ohms, or even less, with little penalty, it's entirely practical to use a 1 kohm or so pot, giving an output impedance low enough to drive any practical load, and the combination having a s/n ratio far beyond the typical circuits of the past. Score 1 for not needing an output buffer.
The obvious reason for putting a level control ahead of a gain circuit is you can handle whatever signal comes in without overloading the gain stage. Still, I find extra preamp gain is something I neither need nor want. I don't want the volume pot operating just off the peg for reasons of both control and matching. With a stepped attenuator there isn't enough resolution down there. Score 1 for passive preamps.
Naturally YMMV, but I don't see how dynamics gets involved, only s/n ratio and useful gain distribution (yes, they say "structure", but I don't).
The ramification of that is they can be driven by a fairly high impedance with no response penalty. The 10:1 rule of thumb you often hear has no basis in fact. Score 1 for passive preamps.
Self talks about signal to noise ratio and pot values in his small signal book It seems that s/n ratio is limited by higher value pots, but you can do far better than is commonly done by using a decent opamp driving a lower-than-normal resistance pot. Since we now have opamps that can drive 600 ohms, or even less, with little penalty, it's entirely practical to use a 1 kohm or so pot, giving an output impedance low enough to drive any practical load, and the combination having a s/n ratio far beyond the typical circuits of the past. Score 1 for not needing an output buffer.
The obvious reason for putting a level control ahead of a gain circuit is you can handle whatever signal comes in without overloading the gain stage. Still, I find extra preamp gain is something I neither need nor want. I don't want the volume pot operating just off the peg for reasons of both control and matching. With a stepped attenuator there isn't enough resolution down there. Score 1 for passive preamps.
Naturally YMMV, but I don't see how dynamics gets involved, only s/n ratio and useful gain distribution (yes, they say "structure", but I don't).
I think so too. I have to wonder about the technical background of Sakis. Hopefully he's the business guy of East Electronics and not involved with the equipment servicing/modification aspect.
Dave.
Fine DF 96 i will just take your word for it had enough of this .....Anything you say ...
You failed a more than once to answer any of my questions yet you continue to question both my knowledge and the practical examples i gave you from existing equipment
A) Why consumer amplifiers do that so commonly if its so wrong and will do nothing as you said ?
B) Why any preamplifier schematic i have in hand has the pot before the buffer
You failed a more than once to answer any of my questions yet you continue to question both my knowledge and the practical examples i gave you from existing equipment
A) Why consumer amplifiers do that so commonly if its so wrong and will do nothing as you said ?
B) Why any preamplifier schematic i have in hand has the pot before the buffer
DAvey this was very insulting .....
Ihave been engineering above 10.000 amplifiers at my 50 what are you talking about?
Ihave been engineering above 10.000 amplifiers at my 50 what are you talking about?
The structure of a consumer integrated amplifier normally is
-- a phono stage or not with gain enough to a line level signal
-- a selector switch between line inputs
--probably a tape monitor circuit for recording use
--and after that you have the combinations we discuss here
1) passive till the amp
2) a pot after the selector driving a buffer or preamp then to the main amp
3) a buffer or preamp after the selector then the pot and then to the amp
4) possible combinations of 2-3 including a tone control stage either in the preamp or as a separated stage
other than that i didnt get the meaning of your post
Dynamics will get involved in low listening level low might mean 0.5W -3W which is more than plenty for casual everyday listening Other than this i have nothing against your sayings Conrad, Blues
I am trying to explain that if any differences this will be present at very low power and probably if you push the amp above that point the problem goes a way ...
I am trying to explain that if any differences this will be present at very low power and probably if you push the amp above that point the problem goes a way ...
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