dsrance

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About dsrance

  1. A shame that no-one could help here, but just in case anyone lurks here and wishes to have a go for themselves, AT THEIR OWN RISK, I've found that the OPA134 IC is a straight drop-in replacement, doesn't have a race-tuned bandwidth so hopefully shouldn't cause any instability. The +/- 18V rail voltage of the IC150 is at the top of the range for this chip, so since it can be reduced a little, this might be a good idea? I've checked the rails on mine and left them at 18V each side for now. I was able to find a "bitser" which has donated a perfect volume pot and better top and bottom covers too I know sonics are a tricky thing and fraught with opinion, rather than cold hard facts, but my impression is that the above chips offer a far better sound at very low volume levels (9 o'clock rather than the recommended 2 - 3 o'clock setting) and my impressions are of a better reproduction of reverb and atmosphere in the recordings played through it. I have played around with the 1uF and 25uF coupling-cap replacement in the audio path but the difference, if anything, wasn't really worth the aggravation compared to the fundamental sonic refinement made by the IC change above. Hope it's ok to post this, as I know that engineers prefer cold hard facts, rather than opinions and "feelings" on these sort of things. This product has been long discontinued though (1976?) and in my view, to get such a wonderful all-round performance from it for such a small amount of money was worth every penny..
  2. Sorry to bother you all again, but since I may have the IC150 volume pot replacement issue under control (with luck), I'd like to go further, as apparently there are genuine gains to be made with updating the IC's and replacing the tant and electrolytics inside. I've trawled the net regarding updates for this preamp and haven't really come up with anything definitive. On the capacitor side, I understand the 1uF tants on the main board and the 4.7uF beads on the phono board could be changed now, but what of the electrolytics, some of which are odd values in today's market? For the power supply, I've found some 1000uF long life ones which may be suitable, but what of the 5uF and 25uF ones? Next question - the IC's themselves. I've read much about OPA604's, LM833N's? and the LME49710N, most or all of which claiming to offer lower noise and distortion, as well as superior sonics. The IC's fitted seem to be 3532's and not LM301's. The serial number of this preamp sample is IC 6684, so a middle production period one? I'm only making a fuss about it because it has been inherited, I sold these when current (and have some loyalty to them) and in the secondary system I'd like to use it in, the facilities (including the tone controls and "loudness feature") would be useful. The "upgrades" suggested above would hopefully help low level listening, as it seems that this was the preamps main weakness (few it seems followed instructions to back off the power amp gain and run the preamp quite hard). PLEASE can someone take pity on me and suggest which IC's I could try, whether they'd simply "drop in" the sockets with little to no other changes/mods to the circuit, and also possible value and type replacements for the caps (I have some WIMA 1uF to replace the main board tants if they're ok to use and have seen some bead-electrolytics from RS-Online at 4.7uF that may be good for the phono board). Perhaps Crown's service dept still have the capacitor update kits????? Thanks in advance for any assistance Dave
  3. Oh ******************************************** Not even the update kits, or even the 150A stepped atenuator, which may not even be the same law??????? OK. next question please.. I understand the basic pot seems to be a 400Klog for volume use. Would a 500K one be ok as a generic replacement, with maybe fixed resistors on the additional "loudness" tappings to simulate a gentle fixed "loudness" curve when the button is depressed? One final thought. the Swedish form DACT make a 500K stepped attenuator which isn't totally out of bounds in costs. maybe one of these could be used, with approximate tappings taken to the loudness connections? Mind you, a cheap donor looks to be the best alternative..... The pot that was used on the IC150 was specifically made for that product back in those days. There was never a replacement kit or some type of retro fit of another type or style of pot tried. All you can do is try it and see if it works. We stopped repairing these models more than 15 yrs ago because parts ran out and since many of them where special ordered type components you can't get anything like them somewhere else. Sorry could be more help. Thanks, Kip Whitehead Crown Technical Support Thanks so much for your trouble.
  4. Oh ******************************************** Not even the update kits, or even the 150A stepped atenuator, which may not even be the same law??????? OK. next question please.. I understand the basic pot seems to be a 400Klog for volume use. Would a 500K one be ok as a generic replacement, with maybe fixed resistors on the additional "loudness" tappings to simulate a gentle fixed "loudness" curve when the button is depressed? One final thought. the Swedish form DACT make a 500K stepped attenuator which isn't totally out of bounds in costs. maybe one of these could be used, with approximate tappings taken to the loudness connections? Mind you, a cheap donor looks to be the best alternative.....
  5. Forgive me for asking, but I've emailed the spares dept twice in recent days and not had a reply as yet (is the IC150 really THAT bad news???? ) I've inherited a fairly late example of said preamp and found it very good if used as suggested in the manual - cough - volume turned well up and gain adjusted on the power amp! However, the volume control pot was worn on one channel at low settings and my attempts to "fix" this has all but ruined it Is a spare still avalable, or have I either got to bodge a replacement pot or buy a donor from the US? I reside in the UK and tatty donors just don't come up here. I'd be happy with a used pot as long as it's basically working to restore the unit to working condition. I understand that careful replacement of the original IC's can bring about worthwhile sonic benefits at lower volume settings too. PLEASE can someone help? Thanks in anticipation.. Dave
  6. A very late reply/addition to this, but which parts are not available now, apart from the usual case bits that were probably "specials" for this model? I've inherited an IC150 which a late friend used since bought new in the mid seventies. It's in very fair condition, although the volume pot is now U/S, mainly due to clumsiness on my part :angry: Is this item still available (I hope so), as it appears to be a non standard part (400K Log with extra taps for the "loudness" function)? When used as per instructions with my now serviced and still great D-60's and with volume turned well up (75%) and overall gain adjusted on the power amps, I was well impressed with the sonics when I had it working, although I did notice an excessive "crispness" with volume turned down and power amp gain turned up, as I suspect many others have done, judging by the negative comments read elsewhere on the web. if the original part is no longer available, might it be possible to obtain a 500K stepped atenuator for volume duties (I think DACT make one for not too much money) and maybe hard wire some resistors in the "loudness" terminals to simulate a fixed curve when this button is depressed? I'd like to keep all funtions reasonably intact if possible. Living in the UK, these preamps are pretty rare and usually working. Obtaining a unit for parts from the US is probably going to be hideously expensive once shipped over here. I've emailed the US parts dept but haven't as yet received a reply Hope someone somewhere can help with a working pot, used or otherwise.....
  7. Thank you for your reply and link. I've only used either headphones (three different types of Sennheisers, two of them fairly high impedance) OR a pair of new speakers of nominally 6-8 Ohms average, which check out fine on other amps... The headphones seem fine on other amps and it's easy on these to change the "capsules" over. It strikes me as if the output devices on the right hand channel aren't cutting in, or the protection (VI limiting) is fully on when driving a speaker load. If you can think of anything further I'd be grateful. I'll gather as much info as I can find and give the amp plus paperwork to our local engineer. Hopefully, he'll find something (I have the manual still, with circuit details). Thanks again for help so far.
  8. Hi everyone, I appreciate this question refers to a very old amp from the early to mid 70's (serial number 4395), but the D60 is a dear old thing and I'd like to get it going again. I bought this amp some years ago for next to nothing in a botched condition. The previous owner had drilled extra holes, fitted "phono" sockets, mostly removed the original input wiring (which looked to be plaited with two returns, one unused?), rather than lightly twisted) and destroyed one of the gain pots in the process! After 10 years of storage, I've obtained new pots from Crown US and re-wired the input from jack sockets to pots and then to the board using 0.8mm solid core wire lightly twisted and run in sleeving as a friends later D60's are and this seems to work fine. I received next to no help from the current UK importers regarding replacement pots and enquiries in general, but had splendid service from Crown's US office, so thought I'd ask here before letting any engineer attempt to fix my problem. The amp works almost fine into headphones, with only the slightest clipping on "sssssibilantssss" at very high levels on the right hand channel (channel 2) and with very "busy" mixes. Acoustic music is fine at most volumes. However, the right hand channel is terminally distorted into a loudspeaker load at all volumes. I've checked the output transistors and they appear not to be short across any of the pins (all 4 measure roughly the same) and I expect the drivers to be ok as well due to the generally clean headphone sound. I removed and cleaned the pins of the IC, together with the socket, which removed a slight trace of noise and all the caps look ok on the surface with no bulging or obvious distress. The D150 series gets mentioned here and there and the circuit looks to be related in part, but I've not seen any mention of the little D60, apart from a few comments suggesting that it (and the D40) might just be the best sounding of the 60/150/300A trilogy... Can anyone help please? I'd love not to have to scrap this little amp.