Many power amps sound better when driven from defined, constant, low output impedance. Secondly, good preamp may serve as an efficient RFI filter.
Well, if you like it this way, what exactly is wrong with an amplifier that it needs a preamp to "improve" the reproduction of source signal?
And, good preamp output is "immune" compared to pot output or opamp + 1k resistor output, less influenced by cables and EMI/RFI.
Did any of you guys ever listen to a source connected directly to an amp without any attenuators, selector switches, buffers or line stages, providing of course that gains are suitable for proper listening levels?
Yes I have listened to amplifiers directly connected to signal source with no volume control, preamp etc., Most often if the amp is not being overdriven even marginally, the sound is more dynamic; however, often because the density of music is a wee bit more, you perceive a loss of resolution and spatial information.
On the contrary, a volume control between a signal source and amp alone, with a preamp, seems to have impedance matching issues where at some settings of the volume control, a bit of life is sucked out of the music. At higher listening levels, it is generally not a problem.
On the contrary, a volume control between a signal source and amp alone, with a preamp, seems to have impedance matching issues where at some settings of the volume control, a bit of life is sucked out of the music. At higher listening levels, it is generally not a problem.
Yes.Peter Daniel said:
Even with headphones, so room acoustics weren't part of the equation.
Even with no mains connection (using big, big batteries) so the power system wasn't part of the equation.
Your point?
CG said:
You are not quite correct assuming that using batteries takes "power system out of the equasion". You are simply replacing one power system with another, but each type has its own problems.
Peter Daniel said:
I had thought that the earlier part of that sentence would have made it clear; my fault for being less specfic.
CG, you made your point, OK. Batteries do tend to isolate better than almost any mains connection, and this has been demonstrated by Dick Sequerra and others for years.
I, too, first felt that I would not hear any difference between direct (just a quality pot) and a preamp. In fact my modified (by me) JC-80 did not fare well in the comparison, and I had put it in the closet. However, when I tried the CTC Blowtorch, there was an actual apparent improvement in the sound quality, to my surprise. I think that it is partially the buffered loading on the quality pot that makes the difference, however to make that buffer took a lot of effort, and much support circuitry.
These independent reports from around the world make sense to me.
I, too, first felt that I would not hear any difference between direct (just a quality pot) and a preamp. In fact my modified (by me) JC-80 did not fare well in the comparison, and I had put it in the closet. However, when I tried the CTC Blowtorch, there was an actual apparent improvement in the sound quality, to my surprise. I think that it is partially the buffered loading on the quality pot that makes the difference, however to make that buffer took a lot of effort, and much support circuitry.
These independent reports from around the world make sense to me.
john curl said:
Could such "buffered loading on the quality pot" be provided by a properly designed amplifier input stage when pot is installed directly at the amp's input?
We measured LOWER THD 10kHz at higher harmonics with a good preamp than without preamp. 10kHz was generated by AP1. The issue was probably non-linear input capacitance of the sound card used (input opamp circuit). The 2nd was higher with the preamp, BUT 3rd, 5th and 7th were higher WITHOUT the preamp. Then, the dependence on opamp type of high order harmonics of the soundcard was measured, at 10kHz.
Hopefully not O.T.
So far in this thread, volume control has been discussed along the voltage divider/resistive method and its resultant raising source impedance the amp sees at lower listening levels.
As I am using a Dave Slage designed Autoformer Volume Control to good effect. At lower volume levels, the source impedance the amp sees will be lower than at WOT.
What are the theoretical and practical advantages/disadvantages of using magnetic coupling vs resistive volume control?
IMHO, transformer volume control sounds *very* good in relation to the pots it replaced.
Has anyone here used one?
So far in this thread, volume control has been discussed along the voltage divider/resistive method and its resultant raising source impedance the amp sees at lower listening levels.
As I am using a Dave Slage designed Autoformer Volume Control to good effect. At lower volume levels, the source impedance the amp sees will be lower than at WOT.
What are the theoretical and practical advantages/disadvantages of using magnetic coupling vs resistive volume control?
IMHO, transformer volume control sounds *very* good in relation to the pots it replaced.
Has anyone here used one?
Re: Hopefully not O.T.
I use them in both of my reference systems and prefer over resistive attenuator. However, it seems like their performance is system dependant and depends even on particular production batch.
You can find more info and opinions on magnetic coupling in following links:
http://www.high-endaudio.com/RC-Linestages.html (bottom of the page)
http://www.6moons.com/audioreviews/musicfirst/passive.html
http://www.goodsoundclub.com/Forums/ShowPost.aspx?postID=3976#3976
steve jones said:
I use them in both of my reference systems and prefer over resistive attenuator. However, it seems like their performance is system dependant and depends even on particular production batch.
You can find more info and opinions on magnetic coupling in following links:
http://www.high-endaudio.com/RC-Linestages.html (bottom of the page)
http://www.6moons.com/audioreviews/musicfirst/passive.html
http://www.goodsoundclub.com/Forums/ShowPost.aspx?postID=3976#3976
Sorry to be late to today's game.SY said:
Yes, but we did use a resistor pair for gain matching.
The source was a Levinson No. 36 DAC whose output impedance spec. is 8 Ohms.
The amplifier was a Bryston 4BSST input Z (single ended) 50K Ohms.
Cardas best RCA plugs and jacks, Cardas silver (5 nines) wire on small vector board. The Vector board plugged directly into amplifier. The only cables were the pair from the DAC to the attenuator board.
Vishay S102 foil resistors. Sorry don't recall the exact values (I want say about 3K total) set to around 11 dB attenuation.
End result: I sold my Conrad Johnson PV12 and my friend sold his Classe pre (older model) we both switched immediately to stepped attenuator passive pre. Still seems like a good decision.
I can easily imagine situations where passive pre R values are too high or driver source Z is too high leading to poor dynamics which is what many claim to be the weakness of passive pre-amps.
I built my own passive using a Shallco switch and Vishay foils (for all most likely gain settings Holcos otherwise to save a few bucks). I designed mine around a mean impedance of 3 K Ohms. My friend bought a Passion passive pre I think its 10K so it's somewhat more sensitive to loading and cables. He uses the Bryston, I use a a Pass Labs X250 (22K Ohms in, if memory serves).
I do not hear the dynamics problems, but as I have explained we did pay attention to source Z and input Z of the power amp. It is very possible that an active pre-amp is superior. I sure can't afford a Blowtorch and other well reviewed pre-amps seem to run in the $4K and up region. I'm quite sure the passive is the best answer if your budget prevents purchasing a first class pre. Of course if you need a Phono stage the whole discussion changes.
(I favor used equipment, obviously the JC-2 is not available that way yet.)
PMA said:
The topic is not about "sound better", but about "sound real", as if there is no amplification.
I can judge John's designs by schematics, constructions, attention to particular details, and according to my own subjective experience they are very optimal, in terms of money per sound quality. And I believe he can build better stuff if somebody can value properly it's significance, but unfortunately "fast food" approach made fashions that contradict to reproduction of real sound. My English is not so good to explain what I mean, but some of you may understand what I am trying to say...
I would say that a nearly ideal preamp has some advantages over no preamp at all, IF you have to remotely locate the pot, and NOT put it directly in front of the amplifier. IF you have to run more than 1 meter of cable, I would think that a BUFFERED pot would be better IF you use the best buffer possible, and not just an IC. In my case, I locate the preamp fairly far from the amp which is between to loudspeakers. I run single end in, BUT balanced out, and this seems to help with the cable run of more than 3 meters. I need to remotely locate the preamp in order to be close to the turntable, and the turntable cannot be too close to the speakers without creating acoustic feedback. It is ALL these factors that give the CTC a small advantage over directly coupling the phono stage (Vendetta) to a very high quality pot, either P&G linear throw, like they use on studio boards, or a multi-turn rotary wirewound pot that I have, through a cable and driving another cable to the power amp. This is the straightest through-path that I can make, and I used it for years, but the CTC seems to do the job slighly better, mostly, I think, because of the cable loading tradeoffs.
turntable not too close to speakers
phono preamp in the best place in relation to turntable-power amplifier
Good thinking, John!
This is to make the best of an Audio System
... and the result will be as good as we think such an audio system can be
.. if the designer has played all his cards right!
And with your knowledge, Mr Curl, I have no doubt This one System is close to optimal.
----------------------------
Here comes questions related and maybe of concern to more diy audio people:
1. CD-Player vs. Speakers.
Concerns when place them in same room?
2. Pre Amplifier vs. Power Amplifier vs. Speakers
Can we without 'problems' use only:
CD -> Power Amp -> Speakers
3. Issues if CD-player have digitally controlled output level
4. Issues If CD-player has not output level attenuator
5. What are the concerns when sending very low level CD-signal/Audio signals several meters to my Power Amplifier?
6. How important is putting the Volume Potentiometer (Attenuator)
very close to Power Amplifier input?
thanks for give some general thinking on these not too often discussed Audio System matters
Hope you will give me an answer, this time, John
yours 🙂 lineup
phono preamp in the best place in relation to turntable-power amplifier
Good thinking, John!
This is to make the best of an Audio System
... and the result will be as good as we think such an audio system can be
.. if the designer has played all his cards right!
And with your knowledge, Mr Curl, I have no doubt This one System is close to optimal.
----------------------------
Here comes questions related and maybe of concern to more diy audio people:
1. CD-Player vs. Speakers.
Concerns when place them in same room?
2. Pre Amplifier vs. Power Amplifier vs. Speakers
Can we without 'problems' use only:
CD -> Power Amp -> Speakers
3. Issues if CD-player have digitally controlled output level
4. Issues If CD-player has not output level attenuator
5. What are the concerns when sending very low level CD-signal/Audio signals several meters to my Power Amplifier?
6. How important is putting the Volume Potentiometer (Attenuator)
very close to Power Amplifier input?
thanks for give some general thinking on these not too often discussed Audio System matters
Hope you will give me an answer, this time, John
yours 🙂 lineup
It should not come as a great surprise that it is quite clever to put the turntable both away from the speakers and close to the listening chair for convenience. And the low level signal from the pick-up should of course travel as short a distance as possible to the RIAA/MC stage. Preferably balanced. And it can of course be discussed, but I am pretty sure the power amplifier(s) should sit close to the speakers. From this follows.... The obvious. The need for a buffer/active preamplifier.
So, not surprisingly, John has had more than one thought in his head simultaneously: System thinking and care for details.
RK
So, not surprisingly, John has had more than one thought in his head simultaneously: System thinking and care for details.
RK
Lineup;
you are welcome to attend one of my home concerts.
As SY said, it is a sobering experience.
All together we may design something.
As for now, I need good acceleration sensors, up to 300 Hz is enough.
Anyone to contribute?
you are welcome to attend one of my home concerts.
As SY said, it is a sobering experience.
All together we may design something.
As for now, I need good acceleration sensors, up to 300 Hz is enough.
Anyone to contribute?
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