potatomasher Posted February 18, 2017 Share Posted February 18, 2017 (edited) I'm in the middle of redecorating and I think i need to move the electronics from where they currently are. At the moment I am using about 20 feet or so of speaker cable and I need to put the equipment in another position. The power amp wont fit in this new position with the other bits as it is too big so i am going to have to put it between the speakers if i move it all. So the question is.....should i leave it as is, or move the electronics and run a longer balanced cable [about 8-10 feet] from the preamp to the power amp? Edited February 18, 2017 by potatomasher clarity Link to comment Share on other sites More sharing options...
Telecine Posted February 18, 2017 Share Posted February 18, 2017 What is the output impedance of your preamp? 1 Link to comment Share on other sites More sharing options...
Zaphod Beeblebrox Posted February 18, 2017 Share Posted February 18, 2017 10 minutes ago, Telecine said: What is the output impedance of your preamp? This is, by far, the most important question. However, it would be helpful to know EVERYTHING about the system, including: * Speaker impedance (curve) * What cables are being used. * Power amp. * Etc. Way too little information provided. 1 Link to comment Share on other sites More sharing options...
Cafad Posted February 18, 2017 Share Posted February 18, 2017 Is it not possible to move the stereo and then redecorate around it? 1 Link to comment Share on other sites More sharing options...
potatomasher Posted February 18, 2017 Author Share Posted February 18, 2017 (edited) there's a modified oppo 105 player, a vincent sp994 power amp [Damping factor: 245 Input impedance: 47 kOhm Input sensitivity: 1V Frequency response: 16 Hz ~ 100 kHz] a vincent SA94 preamp [Frequency response: 10 Hz - 50 KHz +/- 0.5 dB,Nominal output voltage: 2 V,Harmonic distortion: < 0.1 % (1 KHz, 1 Watt),Input sensitivity: 380 mV,Signal-noise ratio: > 95 dB,Input impedance: 47 kOhm,Inputs: 5 x stereo RCA, 1 x stereo XLR, Outputs: 2 x stereo RCA, 1 x stereo XLR, 1 x stereo RCA Rec Out2 x 3.5 mm Jack sockets (Power Control),Colour: black/silver,Weight: 10.9 kg,Dimensions (WxHxD): 430 x 84 x 360 mm] and Lenehan ML3 speakers and i am using very thick speaker cable from Ugly Cable and balanced interconnects from Cable Chick. not sure about the output impedance though - Edited February 18, 2017 by potatomasher Link to comment Share on other sites More sharing options...
GregWormald Posted February 18, 2017 Share Posted February 18, 2017 The GENERAL consensus seems to be that long interconnects are preferred to long speaker cables--HOWEVER the specifics of your system/configuration may affect this. Unfortunately I cannot comment further as I have no experience with your equipment. Trevor may be able to give some recommendations. Good luck. Greg Link to comment Share on other sites More sharing options...
Zaphod Beeblebrox Posted February 19, 2017 Share Posted February 19, 2017 15 hours ago, potatomasher said: there's a modified oppo 105 player, a vincent sp994 power amp [Damping factor: 245 Input impedance: 47 kOhm Input sensitivity: 1V Frequency response: 16 Hz ~ 100 kHz] a vincent SA94 preamp [Frequency response: 10 Hz - 50 KHz +/- 0.5 dB,Nominal output voltage: 2 V,Harmonic distortion: < 0.1 % (1 KHz, 1 Watt),Input sensitivity: 380 mV,Signal-noise ratio: > 95 dB,Input impedance: 47 kOhm,Inputs: 5 x stereo RCA, 1 x stereo XLR, Outputs: 2 x stereo RCA, 1 x stereo XLR, 1 x stereo RCA Rec Out2 x 3.5 mm Jack sockets (Power Control),Colour: black/silver,Weight: 10.9 kg,Dimensions (WxHxD): 430 x 84 x 360 mm] and Lenehan ML3 speakers and i am using very thick speaker cable from Ugly Cable and balanced interconnects from Cable Chick. not sure about the output impedance though - We need to establish the output impedance of the preamp and the capacitance of the cables. You will need to ask some questions to the manufacturers. Link to comment Share on other sites More sharing options...
potatomasher Posted February 19, 2017 Author Share Posted February 19, 2017 ok thanks - I will see what i can find Link to comment Share on other sites More sharing options...
obitankenobi Posted February 19, 2017 Share Posted February 19, 2017 We need to establish the output impedance of the preamp and the capacitance of the cables. You will need to ask some questions to the manufacturers. Hi ZB,Can you explain this concept further? Eg my preamp has output impedance of 600ohmSent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
SAVI Systems Posted February 19, 2017 Share Posted February 19, 2017 Balanced cables are designed to run quite long with no noise added due to that length - this is why all pro, stage and studio gear use balanced. You will be pushing small (approx 4V) through this cable designed specifically for long runs. Speaker cable is not designed to run in long lengths (especially near power) plus your amp will have to push more voltage and current to overcome the cable, inevitably there will also be a longer delay between the speaker and the amp.So in a nutshell, you are lucky to have the balanced option, and I would make use of it ;-) 3 Link to comment Share on other sites More sharing options...
Zaphod Beeblebrox Posted February 19, 2017 Share Posted February 19, 2017 12 hours ago, obitankenobi said: Hi ZB, Can you explain this concept further? Eg my preamp has output impedance of 600ohm Sent from my iPhone using Tapatalk An output impedance of 600 Ohms, for a preamp, is what I would term: 'moderately high'. It is an unacceptably large number in this day, given it is very, very easy to achieve 10 Ohms or less. For any source, the closer to zero Ohms, the better. My own preamp possesses an output impedance of 2 Ohms (open loop). Anyway, getting down to the numbers: Using a modestly high interconnect cable (which is typical of most high end cables) of 300pF/M, we have a total capacitance of 3,000pF for a 10 Metre run. That represents a reactance of a little less than 400 Ohms. Doesn't sound like a big deal, does it? It represents a small(ish) loss of a couple of dB at 20kHz. However, the big problem is this: Since the roll-off will be at close to 6dB/octave, phase shift can be expected all the way down to around 3-4kHz. To solve this problem, you need to do one of several things: * Use MUCH shorter interconnects. * Use MUCH lower capacitance interconnects. * Choose a properly designed preamp, which possesses a MUCH lower output impedance. The last option is best, because interconnect capacitive reactance becomes a non-issue. You can use any cable type and any length (within reason) you desire. 1 Link to comment Share on other sites More sharing options...
frankn Posted February 19, 2017 Share Posted February 19, 2017 @Zaphod Beeblebrox , hi Trev. Would 60 pF/m be reasonable? Companies such as Klotz (my206), Mogami and Belden make affordable high quality microphone cable which can be used as interconnects. And cheap compared to many HiFi cables. Link to comment Share on other sites More sharing options...
Zaphod Beeblebrox Posted February 19, 2017 Share Posted February 19, 2017 (edited) 3 minutes ago, frankn said: @Zaphod Beeblebrox , hi Trev. Would 60 pF/m be reasonable? Companies such as Klotz (my206), Mogami and Belden make affordable high quality microphone cable which can be used as interconnects. And cheap compared to many HiFi cables. Depends on the output impedance of the source (preamp) and the length of the cables. I've seen some really badly designed preamps with output impedance figures of more than 3,000 Ohms. [EDIT] I see you still have your ME25. Your ME25 is limited to high capacitance cables (say-300pF/M) and about 200 Metres of cable. With 60pF/M, I would caution you to keep the cable shorter than a 1,000 Metres or so. Edited February 19, 2017 by Zaphod Beeblebrox 3 Link to comment Share on other sites More sharing options...
Cafad Posted February 19, 2017 Share Posted February 19, 2017 27 minutes ago, Zaphod Beeblebrox said: Depends on the output impedance of the source (preamp) and the length of the cables. I've seen some really badly designed preamps with output impedance figures of more than 3,000 Ohms. [EDIT] I see you still have your ME25. Your ME25 is limited to high capacitance cables (say-300pF/M) and about 200 Metres of cable. With 60pF/M, I would caution you to keep the cable shorter than a 1,000 Metres or so. So the power amp has to be in the same suburb as the preamp then. That seems like a fairly reasonable limitation. 9 Link to comment Share on other sites More sharing options...
Zaphod Beeblebrox Posted February 19, 2017 Share Posted February 19, 2017 Just now, Cafad said: So the power amp has to be in the same suburb as the preamp then. That seems like a fairly reasonable limitation. It's OK. Just. 4 Link to comment Share on other sites More sharing options...
potatomasher Posted February 20, 2017 Author Share Posted February 20, 2017 (edited) well so far I have found out the output impedance of the preamp is 300 ohms Edited February 20, 2017 by potatomasher Link to comment Share on other sites More sharing options...
frankn Posted February 20, 2017 Share Posted February 20, 2017 That is pretty normal for many pre-amps. Used in conjunction with low capacitance interconnects you should be okay running 3-10m pre-to-power. If that allows you to run shorter loudspeaker cables so much the better. 1 Link to comment Share on other sites More sharing options...
potatomasher Posted February 20, 2017 Author Share Posted February 20, 2017 so i guess it's a matter of confirming the capacitance of the cables then - will make inquiries. Do we know if there are low or high ones? what's low? If low capacitance is desired wouldn't they all be that? Link to comment Share on other sites More sharing options...
frankn Posted February 20, 2017 Share Posted February 20, 2017 Look for the cable specs from the manufacturer- the ones above publish them as do many others. 50-60 pF/m (many quote in pF/f so you need to convert) is on the lower side. Lower the better. Music (band) shops sell them pre-made or many have tech's who will make to order. Or buy parts yourself and solder up. There are also many HiFi cable manufacturers that publish their specs as well. Link to comment Share on other sites More sharing options...
Zaphod Beeblebrox Posted February 20, 2017 Share Posted February 20, 2017 1 hour ago, potatomasher said: so i guess it's a matter of confirming the capacitance of the cables then - will make inquiries. Do we know if there are low or high ones? Yes, we do. As a very big generalisation, expensive interconnects tend to be high capacitance. RF and video cables tend to be low capacitance. 1 hour ago, potatomasher said: what's low? If low capacitance is desired wouldn't they all be that? Low would be less than 100pF/M. The desirable trait in a system is a source with a low output impedance (<10 Ohms). That way, ANY interconnect can be used. 1 Link to comment Share on other sites More sharing options...
potatomasher Posted February 20, 2017 Author Share Posted February 20, 2017 ok thanks - I'm trying to find out the capacitance of the cables - no joy so far Link to comment Share on other sites More sharing options...
Zaphod Beeblebrox Posted February 21, 2017 Share Posted February 21, 2017 36 minutes ago, potatomasher said: ok thanks - I'm trying to find out the capacitance of the cables - no joy so far If the manufacturer is unable to supply the information, then measuring is the only way. That is a pretty easy thing to do. It will take about 30 seconds. Link to comment Share on other sites More sharing options...
Tasebass Posted February 21, 2017 Share Posted February 21, 2017 On 20/02/2017 at 7:52 AM, Zaphod Beeblebrox said: , I would caution you to keep the cable shorter than a 1,000 Metres or so. Er...I am reading this correct.. That's 1km..... Tase Link to comment Share on other sites More sharing options...
Zaphod Beeblebrox Posted February 21, 2017 Share Posted February 21, 2017 Just now, Tasebass said: Er...I am reading this correct.. That's 1km..... Tase Correct. 1 Link to comment Share on other sites More sharing options...
walker1000 Posted February 22, 2017 Share Posted February 22, 2017 (edited) Given the low output impedence of a power amp and the higher signal levels I would think longer speaker cables would be the best option , no worrys about preamp impedence or cable capacitance ( as long as sensible speaker cables are used). Noise problems are a lot less to due to the low impedence and higher signal level. Of course I could be missing something here but this is what I have done with my system , 8m speaker cable run and short interconnects . Edited February 22, 2017 by walker1000 Link to comment Share on other sites More sharing options...
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