Buffer To avoid Magic cables.
I used to have a passive volume control. I also can confirm that with a passive volume control cable length, and amplifier and source had a great effect on the sound. My home built record player preamp with LM833 chips sounded best, but my CD player sounded different with each amplifier. The preamp was made with LM833 chips and had low output impedance.
This experience led me to build a simple transistor beffer called NPN Common Collector Amplifier This has relatively small numbers of parts, a small amount of cost (if you have a supply of batteries or a convenient smoothed power supply), no noticeable degradation, and a considerable improvement, with a total build cost of less than 10 Euro.
Before I had the active cross over each amp had strengths and weaknesses, with all sources other than the LM833's, The CD player I had then with a Hardon Carmon receiver (now in scarp yard in sky),JLH 10W amplifier , a Rodgers cadet III valve amplifier, Quad 303, Quad 405-1 and ESL 57's.
After the active buffer was added before the volume control, The CD player and amplifier combinations improved and no combination degraded. Cables no longer seemed to have an effect on the system thankfully.
After the active cross over I could clearly liked the midrange of the Rodgers best but felt it was a distorted like sound, anyway its treble roll off was to early, The JLH 1969 was excellent, and bettered low bass roll off of the Rodgers. The 303 then came in next clearly bettering the Receiver or the 405. I then fixed the JLH 1969->1996 and got the Bass with that to equal the Quad 405's which no other matched, this was much more confusing with a passive preamp and a cheap CD player.
I recommend you build a Op-amp 100% feedback, or the NPN Common Collector Amplifier a buffer and try it out with your passive system, it will probably improve things, or save money on Magic Cables.
I used to have a passive volume control. I also can confirm that with a passive volume control cable length, and amplifier and source had a great effect on the sound. My home built record player preamp with LM833 chips sounded best, but my CD player sounded different with each amplifier. The preamp was made with LM833 chips and had low output impedance.
This experience led me to build a simple transistor beffer called NPN Common Collector Amplifier This has relatively small numbers of parts, a small amount of cost (if you have a supply of batteries or a convenient smoothed power supply), no noticeable degradation, and a considerable improvement, with a total build cost of less than 10 Euro.
Before I had the active cross over each amp had strengths and weaknesses, with all sources other than the LM833's, The CD player I had then with a Hardon Carmon receiver (now in scarp yard in sky),JLH 10W amplifier , a Rodgers cadet III valve amplifier, Quad 303, Quad 405-1 and ESL 57's.
After the active buffer was added before the volume control, The CD player and amplifier combinations improved and no combination degraded. Cables no longer seemed to have an effect on the system thankfully.
After the active cross over I could clearly liked the midrange of the Rodgers best but felt it was a distorted like sound, anyway its treble roll off was to early, The JLH 1969 was excellent, and bettered low bass roll off of the Rodgers. The 303 then came in next clearly bettering the Receiver or the 405. I then fixed the JLH 1969->1996 and got the Bass with that to equal the Quad 405's which no other matched, this was much more confusing with a passive preamp and a cheap CD player.
I recommend you build a Op-amp 100% feedback, or the NPN Common Collector Amplifier a buffer and try it out with your passive system, it will probably improve things, or save money on Magic Cables.
Me tinks he said everyone favored passive until they heard a good active , then it was all over ..😉
A good Active pre-amp will wake up any system, passive units lack dynamics and are dead sounding by comparison. well IMO.
A good Active pre-amp will wake up any system, passive units lack dynamics and are dead sounding by comparison. well IMO.
The chances of hearing a good active are about nil for most people, diyers included. Most units have at least one severe compromise in either the attenuator, active stage, coupling components or power supply. It's usually enough to skew the comparison in favour of a decent passive pre.
I find it relatively easy to pick a good sounding commercial power amp. Not so with preamps, which at least up to the 3-4k price level are universally bad.
Hi,
as I wrote in #29, the path to Endor leads not via a simple pot but a switched resitor network. At typical listening levels and a well designed network of the described type there will be only 2-4 resistors in the signal path. Does anyone really think one could come closer to the ideal of a ´piece of wire´ with a bunch of active devices?
Well, I don´t ;-)
jauu
Calvin
as I wrote in #29, the path to Endor leads not via a simple pot but a switched resitor network. At typical listening levels and a well designed network of the described type there will be only 2-4 resistors in the signal path. Does anyone really think one could come closer to the ideal of a ´piece of wire´ with a bunch of active devices?
Well, I don´t ;-)
jauu
Calvin
Dear Calvin,
In my opinion, the ideal has less to do with the ideal nature of wire but rather the thing driving the wire and the thing being driven by the wire. In other words; if your sources all have low output impedance and your destination (I guess power amplifier) has high input impedance then a wire can be fine, and cable issues will be insignificant and the effects of your potentiometer stepped or simple will be insignificant.
If the output impedance is high from the source, cable effects become significant, and combining them with the stepped attenuator or for that matter the simple pot, will make a passive filter, depending upon the inductance or capacitance of the wire, this filter will have different sounds.
Worse still happens if the source is forced into class B operation due to the low input impedance of the amplifier, so significantly increasing distortion.
A simple impedance buffer such as a NPN Common Collector Amplifier costs so little you might find it interesting to try it, and depending on sources and amplifiers it may improve the sound and I very much doubt it will degrade the sound, although the slightly less than unity gain (slight voltage signal attenuation) may be seen as negative on direct AB switching.
I do agree with you on the issue that duel gang potentiometers do not match channels well, but have yet to worry about this issue significantly, though it is on the list, and ALPS pot has been good enough for me for a while. I am considering a stepped attenuator, and have looked at some relay driving kits on ebay, as I do like a rotary volume control and 127 step single switch attenuators are prohibitively expensive.
Regards
Owen
In my opinion, the ideal has less to do with the ideal nature of wire but rather the thing driving the wire and the thing being driven by the wire. In other words; if your sources all have low output impedance and your destination (I guess power amplifier) has high input impedance then a wire can be fine, and cable issues will be insignificant and the effects of your potentiometer stepped or simple will be insignificant.
If the output impedance is high from the source, cable effects become significant, and combining them with the stepped attenuator or for that matter the simple pot, will make a passive filter, depending upon the inductance or capacitance of the wire, this filter will have different sounds.
Worse still happens if the source is forced into class B operation due to the low input impedance of the amplifier, so significantly increasing distortion.
A simple impedance buffer such as a NPN Common Collector Amplifier costs so little you might find it interesting to try it, and depending on sources and amplifiers it may improve the sound and I very much doubt it will degrade the sound, although the slightly less than unity gain (slight voltage signal attenuation) may be seen as negative on direct AB switching.
I do agree with you on the issue that duel gang potentiometers do not match channels well, but have yet to worry about this issue significantly, though it is on the list, and ALPS pot has been good enough for me for a while. I am considering a stepped attenuator, and have looked at some relay driving kits on ebay, as I do like a rotary volume control and 127 step single switch attenuators are prohibitively expensive.
Regards
Owen
Hi,
in how many cases would a gross impedance mismatch occur (source impedance >>1kOhm, load impedance <<10kOhm?).
To my experience this situation is very rare.
So why sacrifice sonics when only in less than 5% of all cases a switched resistor network would actually be inferior to a buffered volume control?
I rather prefer to listen 95%-99% of the time to superior sonics, hence passive.
In my preamp I chose to make the active stages switchable (there´s an input symmetrizer stage with switchable gains of 0dB and +6dB and a output Buffer), so I can configure the signal path on demand and always listen to the optimal configuration.
Guess what.......I rarely switch the active stages on, mostly just to see if they´re still functional.....I haven´t had a situation yet where I really needed or preferred active over passive mode and it´s not that the active stages were of lousy quality ;-) Put on a human voice or a string quartet and the differences especially in the mid-highs are revealing.
jauu
Calvin
in how many cases would a gross impedance mismatch occur (source impedance >>1kOhm, load impedance <<10kOhm?).
To my experience this situation is very rare.
So why sacrifice sonics when only in less than 5% of all cases a switched resistor network would actually be inferior to a buffered volume control?
I rather prefer to listen 95%-99% of the time to superior sonics, hence passive.
In my preamp I chose to make the active stages switchable (there´s an input symmetrizer stage with switchable gains of 0dB and +6dB and a output Buffer), so I can configure the signal path on demand and always listen to the optimal configuration.
Guess what.......I rarely switch the active stages on, mostly just to see if they´re still functional.....I haven´t had a situation yet where I really needed or preferred active over passive mode and it´s not that the active stages were of lousy quality ;-) Put on a human voice or a string quartet and the differences especially in the mid-highs are revealing.
jauu
Calvin
My observations are similar: a passive sounds more transparent and direct than even the best active. Yet, for some reason i (and others) find the active pre a more musically satisfying solution. Simply put i tend to listen to music more often and for longer periods using an active device. Crude impedance considerations have nothing to do with this not to mention my current pre does not even have particularly low output impedance (iirc nor does the Blowtorch). It may well be that the active pre helps to mask problems elsewhere in the system, in particular in the digital frontends. My analogue system does not benefit from an active pre in a similar degree.
let's take your less than rare example.
Source impedance =1k0 with a DC blocking cap of 470nF.
Receive impedance =10k with a 1uF DC blocking cap and a 47pF cap across input socket and an RF filter of 680r + 1nF (0.68us) at the receiver PCB.
Now add your passive or active volume control.
Decide whether it is in or next to the source or alternatively in or next to the receiver.
How long and what type of cables are to be used before and after the volume control.
Now do the sums.
If you are surprised at the differences that a buffer can make then you knew nothing about the subject.
If you are not surprised at the differences then consider why the buffer allowed these two pieces of equipment to be joined and why the buffer allows the volume control to be anywhere in the room, not just near the receiver/source.
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Hi,
well Andrew, Your try to schoolmaster me, hopelessly failed. Try something more appropiate. 😀
Below 5m of cable length I haven´t experienced any problems in passive mode and with rather common devices up to 10m presented no problem.
But in case, I just push a button on the IR-commander and switch the buffer stage into the signal path.
Anything else is a matter of Taste.
jauu
Calvin
well Andrew, Your try to schoolmaster me, hopelessly failed. Try something more appropiate. 😀
Below 5m of cable length I haven´t experienced any problems in passive mode and with rather common devices up to 10m presented no problem.
But in case, I just push a button on the IR-commander and switch the buffer stage into the signal path.
Anything else is a matter of Taste.
jauu
Calvin
I found, that passive is best, unless you have the very best class A, low or no feedback electronics.
Agree with these... So super duper expensive active pre do make sense...
Super expensive active pre I think mostly is not single ended. So transistor matching is a must. And so is oscilloscope at minimum (for DIY). To make it easier, I tried to pick cheap commercial preamp with matched input FET and try to upgrade the power supply, also use ears to find "matched" components.
Currently I'm working on Marantz Esotec SC-6.
"I find it relatively easy to pick a good sounding commercial power amp. Not so with preamps, which at least up to the 3-4k price level are universally bad. "
Really? I find this to be an amazing statement.
Really? I find this to be an amazing statement.
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