I have been reading a lot of information regarding the use of either active or passive pre-amps, and I have yet to find any agreement as to which is best. I am building, well I am about to build a pair of mono block power amps (Lynx) to which I need to add a pre-amp with remote volume control. Question; which is better, to have an amp next to each speaker giving the shortest speaker leads using an active pre-amp, or having the amps together and having the shortest interconnect leads using a passive pre-amp? What other alternatives are there? I would welcome any ideas and opinions on this. Thanks in advance for your input.
Hi
I am also building a pair of lynx monoblocks - when I collect all the parts.
To help you make a decision on active or pasive pre amp you need to look at the output impedance of your sources and the input impedance of the power amp. You need a relatively low output impedance feeding into a high input impedance. This is normally easy to achieve with an active pre amp. However this is difficult, and often impossible, to achieve with a passive pre amp unless you operate it with a buffer stage.
It is normally best to keep the speaker cable short and have a longer run of interconnect between the pre and power amp. If the pre amp output impedance is low ( around 100 ohm ) and the power amp impedance is high ( around 10k ohm ) an interconnect between the pre and power amps of 5 meter should not be unduly affected by capacitance in the interconnect. However if the interconnect is longer or the interconnect has a high capacitance then you may experience high frequancy attenuation.
So I find it safest to use an active pre amp with short speaker cables and longer incerconnect cables.
Don
I am also building a pair of lynx monoblocks - when I collect all the parts.
To help you make a decision on active or pasive pre amp you need to look at the output impedance of your sources and the input impedance of the power amp. You need a relatively low output impedance feeding into a high input impedance. This is normally easy to achieve with an active pre amp. However this is difficult, and often impossible, to achieve with a passive pre amp unless you operate it with a buffer stage.
It is normally best to keep the speaker cable short and have a longer run of interconnect between the pre and power amp. If the pre amp output impedance is low ( around 100 ohm ) and the power amp impedance is high ( around 10k ohm ) an interconnect between the pre and power amps of 5 meter should not be unduly affected by capacitance in the interconnect. However if the interconnect is longer or the interconnect has a high capacitance then you may experience high frequancy attenuation.
So I find it safest to use an active pre amp with short speaker cables and longer incerconnect cables.
Don
How about both? IMO short low level interconnects are desirable with either a passive or active preamp. Short speaker cables are also desirable, but you can compensate for distance with wire gage to some extent. Not so for the low level runs- go for low capacitance. You mention a remote volume control, so why not split the difference with a couple feet of low level and a few feet of high level? The choice of a passive pre involves many things, including how loud you like to listen. I find most active preamps have far more gain than I'd ever need, so passive works just fine. The safe rule is low output impedance from the pre, and high input impedance to the power amp, but it's really more complicated than that. If the input impedance to the power amp is flat over frequency, the value is far less important, and the only penalty is signal level. That's often the case, but the only way to know is to measure it. I run a 7kohm stepped attenuator, so the typical output impedance is around 3k. That feeds a flat load of about 10-20k with no problem. EMMV (everybody's milage may vary, not just yours!)
Hello Conrad, Mooly and AMV8, thanks for your replies. There are a couple of factors affecting the choice, one of which is my wife who has a great dislike for thick speaker cables (interconnects are a lot easier to hide) so having the power amps under the speakers has two advantages.(one sonic and one quieter life)! Also, I recently took my current pre amp (a pretty bad NAD thing) out of my system so the dvd player that I am using at the moment feeds straight into my NAD power amp. The effect was like taking a blanket off the speakers. The dvd player has a built in volume control but its replacement does not, hence the need for a pre amp with remote volume control. I would prefer to add as little circuitry as possible back into the signal path. There are quite a few choices with regards attenuation methods; any preferences? I have been looking at the kits from Dantimax (passive and active) which look like they might do. Thanks again.
Why not build a preamp with buffered output ?
Let it have a gain of 2 and output impedance of 50 Ohm.
Then just add 50 Ohm resistor across the inputs of the power amps to get gain = 1 again.
Use any interconnect cable you want or better a 50 Ohm Coax cable, e.g. RG233
You won't believe your ears! Totally noise free
Let it have a gain of 2 and output impedance of 50 Ohm.
Then just add 50 Ohm resistor across the inputs of the power amps to get gain = 1 again.
Use any interconnect cable you want or better a 50 Ohm Coax cable, e.g. RG233
You won't believe your ears! Totally noise free
Re: Re: 50ohm interconnect
What is the characteristic impedance of the cable you recommend?
What series resistor will you fit at the power amp end?
What load resistor value will you fit at the speaker end?
What effect will the speaker impedance have on the terminating resistor?
What power will be dissipated in the terminating resistors?
Again, How?
How?Mooly said:
What is the characteristic impedance of the cable you recommend?
What series resistor will you fit at the power amp end?
What load resistor value will you fit at the speaker end?
What effect will the speaker impedance have on the terminating resistor?
What power will be dissipated in the terminating resistors?
Again, How?
Re: 50ohm interconnect
It so happend, that a couple of weeks ago, I visited your site, neighbour countryman ACD.
(Mr. Lineup sits in very north of Sweden, Lapland, writing this to you )
I turns out you have developed and provide a cable driver circuit/buffer.
For use, for example, to optimally transfer of audio signals into a specific impedance terminated cable.
Great and rather unique device, with very good data
Output Impedance: 50 Ohms
Here you are, our dear uk-fellow Andrew:
Image:
http://audio-innovation.eu/images/BUFFER v1-1/BUFFER 1 v1-1 RCA 650.jpg
Details, PDF:
Cable Driver principal theory - and why it is good
Website & lniks, see ACD signature.
lineup good audio greetings
AndrewT said:
ACD said:Andrew
Try do a search here on diyAudio
It so happend, that a couple of weeks ago, I visited your site, neighbour countryman ACD.
(Mr. Lineup sits in very north of Sweden, Lapland, writing this to you )
I turns out you have developed and provide a cable driver circuit/buffer.
For use, for example, to optimally transfer of audio signals into a specific impedance terminated cable.
Great and rather unique device, with very good data
Output Impedance: 50 Ohms
Here you are, our dear uk-fellow Andrew:
Image:
http://audio-innovation.eu/images/BUFFER v1-1/BUFFER 1 v1-1 RCA 650.jpg
Details, PDF:
Cable Driver principal theory - and why it is good
Website & lniks, see ACD signature.
lineup
good audio greetingsAttachments
Hello lineup from the great north
I wouldn't promote my self and therefore didn't made a link to this, however now when you have pulled it all into public attention, I can say that for line level interconnections it makes a h*** of a difference
I did post some pictures in this thread
http://www.diyaudio.com/forums/showthread.php?s=&threadid=96192&perpage=50&highlight=&pagenumber=7 some times ago. I have attached the picture here again.
However I have never tried Coax as speaker cables.....
Maybe I should give it a try
I wouldn't promote my self and therefore didn't made a link to this, however now when you have pulled it all into public attention, I can say that for line level interconnections it makes a h*** of a difference
I did post some pictures in this thread
http://www.diyaudio.com/forums/showthread.php?s=&threadid=96192&perpage=50&highlight=&pagenumber=7 some times ago. I have attached the picture here again.
However I have never tried Coax as speaker cables.....
Maybe I should give it a try
Attachments
Belden 89259 coax is what I use for all my Interconnects, And just to spice them up, I used Eichmann Bullets for the RCAs.
75 ohms and very low capacitance (17.3 pf per foot) and the shielding works just right!
Research it, much has been written about it and from what I remember....all positive.
http://www.google.com/search?hl=en&q=Belden+89259
Sorry to keep this off topic!
Regards//Keith
75 ohms and very low capacitance (17.3 pf per foot) and the shielding works just right!
Research it, much has been written about it and from what I remember....all positive.
http://www.google.com/search?hl=en&q=Belden+89259
Sorry to keep this off topic!
Regards//Keith
http://web.telecom.cz/macura/buffer_en.html
This is brought to you by our own PMA (Pavel Macura).
This is for interconnects ONLY, not speaker cables!! (Speaker cables ?! YIKES!!
)
This is brought to you by our own PMA (Pavel Macura).
This is for interconnects ONLY, not speaker cables!! (Speaker cables ?! YIKES!!
)
Well Coax in general is just a little too wide and I (me) wouldn't assume that meant any coax. But these threads are perused by people of many levels of technical knowledge so I guess a better definition might be appropriate.
I would bet most of us just jumped to that step automatically and thank you for reminding us not to combine steps as that can be confusing for newbies (guilty). Children are better at reminding us that things that adults think are one step are really ten smaller steps. Being a teacher keeps you reminded of that daily. My cat is my child and she doesn't do a good job! But you should see what she can do with a toy mouse.
See my prevoius thread for an example of something that fits the definition remarkably well (whatever the definition is. LOL)!
The Belden cable can be bought by the foot and terminated to the PCB at both ends to bypass mechanical breakdown of the connectors if desired AND you don't care about inconvenience! Preamp/Passive Linestage to Amp (What this thread is about).
Is that better?
Regards//Keith
I would bet most of us just jumped to that step automatically and thank you for reminding us not to combine steps as that can be confusing for newbies (guilty). Children are better at reminding us that things that adults think are one step are really ten smaller steps. Being a teacher keeps you reminded of that daily. My cat is my child and she doesn't do a good job! But you should see what she can do with a toy mouse.
See my prevoius thread for an example of something that fits the definition remarkably well (whatever the definition is. LOL)!
The Belden cable can be bought by the foot and terminated to the PCB at both ends to bypass mechanical breakdown of the connectors if desired AND you don't care about inconvenience! Preamp/Passive Linestage to Amp (What this thread is about).
Is that better?
Regards//Keith
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.