ricktate Posted June 5, 2013 Share Posted June 5, 2013 I have Mac 2125 when I connect it to sony discman straight to the amp I have good bass but when I hook it to avr pre-outs it lacks bass. Does anyone know a reason for this would a Mac pre amp be more suited to the amp? I been thinking about fellow members Mac pre-amp want to make sure this will fix the problem. Thanks Rick Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted June 5, 2013 Share Posted June 5, 2013 If it's an AVR with bass management and your speakers are set to "small", it's redirecting the bass to your mains. Try setting them to large. Quote Link to comment Share on other sites More sharing options...
ricktate Posted June 5, 2013 Author Share Posted June 5, 2013 It is an old avr[HK avr 20] so not sure it has large and small, but aren't the pre outs for the mains anyway? If I get a newer AVR will the pre outs supply the bass then?If I buy the Mac pre amp will bass be ok then?Is dampaning[spelling?] factor involved in this problem? Thanks Rick Quote Link to comment Share on other sites More sharing options...
babadono Posted June 5, 2013 Share Posted June 5, 2013 RickTate, I could be way off here but I think Carl meant the bass is being redirected to the SUBWOOFER output and taken out of the main pre outputs if the mains are set to small. babadono Quote Link to comment Share on other sites More sharing options...
ricktate Posted June 5, 2013 Author Share Posted June 5, 2013 Oh ok I get it now.......Does this old avr have small and large ? Rick Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted June 5, 2013 Share Posted June 5, 2013 I have no idea. If it's REALLY old, it may not. All AVR's as of late have bass management. Do you have an owners manual? Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted June 5, 2013 Share Posted June 5, 2013 RickTate, I could be way off here but I think Carl meant the bass is being redirected to the SUBWOOFER output and taken out of the main pre outputs if the mains are set to small. babadono That's correct. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted June 6, 2013 Share Posted June 6, 2013 I don't think that receiver has bass management for the front speakers, it may have an impedance mismatch issue. I am sure the Mac pre would work nicely. Manual link. http://www.harmankardon.com/resources/Brands/harmankardon/Products/ProductRelatedDocuments/en-US/OwnersManual/AVR20om.pdf Dave Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted June 6, 2013 Share Posted June 6, 2013 I don't think that receiver has bass management for the front speakers, it may have an impedance mismatch issue. I am sure the Mac pre would work nicely. Dave, wouldn't an impedance mismatch effect 20 to 20K and not just bass? Quote Link to comment Share on other sites More sharing options...
babadono Posted June 6, 2013 Share Posted June 6, 2013 RickTate, I don't even see any subwoofer output on the unit Dave linked the data sheet of. If this is your unit then definitely the main pre outs should have the full range signal. Do you know what the input impedance of the Mac is? It should be high compared to the output impedance of the AVR pre outs but perhaps the output coupling capacitors are too small in value or they have degraded with age. This is all speculation on my part. Do the pre outs sound OK when coupled into the internal amp of the AVR? babadono Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted June 6, 2013 Share Posted June 6, 2013 I didn't use the link but looked up the model. It does not have bass management but does have a sub out. The L and R front outputs should receive a full signal. Quote Link to comment Share on other sites More sharing options...
ricktate Posted June 7, 2013 Author Share Posted June 7, 2013 Yes it sounds good with the internal amp hooked up that is what I do not understand. Must be something mis matched I guess thanks for the help though. Rick Quote Link to comment Share on other sites More sharing options...
djk Posted June 7, 2013 Share Posted June 7, 2013 Are you using the same discman as a source with the AV receiver? Most of those discman type products have built-in loudness compensation. If using a normal CD/DVD player with the AV piece you won't be getting the bass boost from the loudness circuit of the discman product. The McIntosh should have plenty of bass, they tend to sound warmer than most amplifiers. If the loudness function is not the issue, all the small electrolytics should be replaced in the McIntosh. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted June 7, 2013 Share Posted June 7, 2013 Are you using the same discman as a source with the AV receiver? Most of those discman type products have built-in loudness compensation. If using a normal CD/DVD player with the AV piece you won't be getting the bass boost from the loudness circuit of the discman product. The McIntosh should have plenty of bass, they tend to sound warmer than most amplifiers. If the loudness function is not the issue, all the small electrolytics should be replaced in the McIntosh. Makes sense. Quote Link to comment Share on other sites More sharing options...
babadono Posted June 7, 2013 Share Posted June 7, 2013 If the loudness function is not the issue, all the small electrolytics should be replaced in the McIntosh djk and ricktate, Wow really? I would want to put a signal generator and oscilloscope on that Mac before I started replacing parts in a Mac. Hey but that's just me. I am an electronic engineer. babadono Quote Link to comment Share on other sites More sharing options...
WMcD Posted June 7, 2013 Share Posted June 7, 2013 I don't know. When driving the Mac you have removed the jumpers so that you are using the pre-out of the HK, is that correct? Please let us know. If you use the center channel output there is a bass management (speaker size) adjustment shown in the HK manual. To clear up a technical issue. We are not trying to transfer power between the pre-amp out and a power amp in. All we want is to do is to make sure that the voltage of the pre-amp out is delivered to the power amp input. Very little current is flowing. The output impedance of the pre-amp should be relatively low (and typically is), meaning it can deliver all the current needed so that the pre-amp output does not sag down with a load. Let me pick a number of 1000 ohms output impedance. The input impedance of the power amp should be relatively high (and typically is), meaning that it is not drawing much current and does not impose a load which will cause the output of the pre-amp to sag down. Let me pick a number of 10000 ohms input impedance. It is difficult to get current through the high impedance of the load. So, you can see that this is perhaps bad for power transfer, but it is good for making sure the voltage (i.e. music) is transferred. One thing which can get in the way of the scheme is a very long connecting cable (one rule of thumb I've seen is to keep cable length to less than 16 feet if you're using RCA type unbalanced). The longer the cable length, the more the capacitance and this can, essentially, short circuit the signal to the ground or chassis. But the short circuiting effect typically affects high freqs, not low. The inductance and resistance of the cable can affect things too. But, just thinking about capacitance. This means that the wire has some capacity which requires it to be filled up with electrons during the positive part of a sine wave and drained out during a negative part of a sine wave. (Capacitance means that the effects of the electrons are stored in the electric field between the inner conductor and the shield, like a Leyden jar.) The relative low output impedance of the pre-amp out allows the pre-amp to do so. I would certainly not start fooling with the inside of the Mac. Do: Check what is plugged into what, where. Check cables themselves, and snug connections. Check settings on the HK like loudness, bass, and treble controls. Shut down Dolby processing. WMcD Quote Link to comment Share on other sites More sharing options...
djk Posted June 8, 2013 Share Posted June 8, 2013 "Wow really? I would want to put a signal generator and oscilloscope on that Mac before I started replacing parts in a Mac" So what would you do if you didn't have test equipment? The caps are over 30 years old, they could stand replacement even if they are working today. If it's not the loudness issue it's the caps, what else could it possibly be? C239, 240 (little board on the input jacks, very tight for space) C203, 204 (input coupling cap to impedance buffer) C207, 208 (output coupling cap from impedance buffer) C219, 220 (feedback cap) You may want to take off the glass front panel to avoid cracking it while working on the amplifier, the chassis can flex quite a bit with the covers removed on the amp Quote Link to comment Share on other sites More sharing options...
ricktate Posted June 8, 2013 Author Share Posted June 8, 2013 Well I will think about fixing it or selling it then. Thanks guys Rick Quote Link to comment Share on other sites More sharing options...
WMcD Posted June 8, 2013 Share Posted June 8, 2013 Let me know if you're selling it un-fixed. WMcD Quote Link to comment Share on other sites More sharing options...
babadono Posted June 10, 2013 Share Posted June 10, 2013 So what would you do if you didn't have test equipment? Ah.......take it to someone who does? I dunno that's just a guess. Is there anyone close to RickTate that can help him out? RickTate, Can you get any suppoort from MacIntosh? babadono Quote Link to comment Share on other sites More sharing options...
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