Soody Posted November 1, 2020 Share Posted November 1, 2020 I thought i'd make this thread about the process of getting my grandad's old stereo going again. Maybe people will find this experience helpful and i'd certainly like some advice. It's a quad 303/33 system and some (i think) custom Kef speakers that he built in the 70s. This is the starting point. The amplifiers work but they sound terrible. The speakers on the other hand, after tightening the drivers, sound fantastic with my technics amp. I thought about buying a kit myself to restore the Power Amp, but i suck at soldering at would like to practice first. So I took it to a pro, Robert at Lynx Electronics NZ, who repaired it. His comments "The THD figures show that its left channel is pretty bad, some resistors / capacitors must be faulty, but at this stage, I reckon some shifted value resistors are most likely causing the problem." "Upon further examination of your Quad 303. As my previous prediction, I found a couple of shifted value resistors. Most of the resistors are very good. I took some electrolytic capacitors off PCB and measured their characteristics, all great apart from one that is considered OK. Also, the amp is the later version. Thus, I don't see any reason that the unit needs to be restored. What it needs is a general repair. After servicing, it will be back to its shining life again." before: after: This cost $138. He also made me a new Din-RCA cable. So now i'm using the amp with just the source (computer or pmp) volume control which I don't like. So i bought a $10 passive volume control. It sounds fantastic now. The sound is not only 'better' (cleaner, higher fidelity) than my technics amp, but it seems charmingly different also. I wasn't even sure the amp would make much of a difference, I always thought speakers mattered and as long as an amp could drive them it was moot. But this amp has made a huge difference. I'm really happy with the repair. But i'm not so happy with the passive volume controller. The range of attenuation is tiny and it's just not nice to use. I was sceptical about if it was worsening the sound or not, so I bought a nicer version of aliexpress for $50, the WEILIANG AUDIO FV3 high precision passive preamplifier volume controller with Japanese ALPS27 high precision potentiometer & US pure copper plated CMC816 input and output RCAs. This cost $50 and took several months to arrive. And i bought a higher end aux cable off ali too. Firstly, it's just really nice using nice things. Secondly it sounds a lot better. I don't know how exactly to describe this but where say Joanna Newsom vocals suffered before, now they sound better. That is the most noticeable thing it changes. Higher pitched vocals. Infact just across the board the system sounds better now. I see a lot of people liking or disliking the Quad 303 with a passive pre-amplifier and I like it a lot. Does a high quality one make a difference? Yes. Maybe some of that is shorter high quality cables too. So at this point i'm in love with how this stereo sounds. But also well... It's always good to improve. I have zero desire to upgrade past this point but I would like to tweak the system. Things i'm considering A Dac for my computer. SMSL 10th mk2. Would actually look quite cool because it's the same shape as the 303 and the volume controller. Or a topping. Buying a DADA electronics kit for the 33 preamp and attempting to restore it myself and seeing how it compares. Opening the speakers and looking at the crossovers etc. I want advice on this. I'm not sure what the speakers even are or if that is a good idea or not. I really hate to fix what isn't broken and broke it. Potentially a more comprehensive overhaul of the 303. I'm really not sure about this. The tech guy didn't seem to think it was a good idea. Same deal as above. Biggest upgrade would probably be a room with better acoustics. Maybe some stands for the speakers. I'd love any thoughts or advice on this. 4 Link to comment Share on other sites More sharing options...
muon* Posted November 1, 2020 Share Posted November 1, 2020 Nice, and looks like some fun There may be electrolytic capacitors in the XO's and they would be passed their used by date if they do exist, replace with poly's or a nice sounding electrolytic like Silmic ll 100v. Same with the electrolytic caps in the amp, after 20+ years they are often not working as they originally did. Link to comment Share on other sites More sharing options...
stereo coffee Posted November 1, 2020 Share Posted November 1, 2020 This is a nice change to the 33, that neatly fits the three boards that provide 6 stereo inputs. The power supply is a 12vAC 20VA toroidal , mounted in an external case. Its possible to use the original push button switches, but I quite like using one of the round dials for selecting inputs. 1 Link to comment Share on other sites More sharing options...
Al.M Posted November 1, 2020 Share Posted November 1, 2020 (edited) The Quad preamp and power amp are quite nice sounding so worth restoring and will match the speakers. However, there are also some very good alternative preamps like the world class sounding Stereo Coffee kit preamp in NZ for around $250 that would be way better sound than the 303. Check it out online if you like. Badly matched passive volume controls can really sound dull. Edited November 1, 2020 by Al.M 1 Link to comment Share on other sites More sharing options...
Soody Posted November 1, 2020 Author Share Posted November 1, 2020 25 minutes ago, Al.M said: Badly matched passive volume controls can really sound dull. I don't think it sounds dull, I think it sounds great. Maybe just my poor point of reference though. The range of attenuation I think is also right. How would you quantify what makes a good match? It's this. 50KA x 2 alps27 pot. (Well supposedly. I could open it up and it's not that, knowing aliexpress traders) 1 Link to comment Share on other sites More sharing options...
Soody Posted November 1, 2020 Author Share Posted November 1, 2020 1 hour ago, stereo coffee said: This is a nice change to the 33, that neatly fits the three boards that provide 6 stereo inputs. The power supply is a 12vAC 20VA toroidal , mounted in an external case. Its possible to use the original push button switches, but I quite like using one of the round dials for selecting inputs. Pretty cool. Photo I took of my 33 guts for comparison. I think this is a great idea to do when I need more inputs. Not sure how i feel about butchering it though. Maybe sort some other case. Link to comment Share on other sites More sharing options...
Soody Posted November 1, 2020 Author Share Posted November 1, 2020 2 hours ago, muon* said: Nice, and looks like some fun There may be electrolytic capacitors in the XO's and they would be passed their used by date if they do exist, replace with poly's or a nice sounding electrolytic like Silmic ll 100v. Same with the electrolytic caps in the amp, after 20+ years they are often not working as they originally did. cheers : ) XO's, that's the speakers? Can anyone tell anything else about them? I will open them up when I have some time and see. Link to comment Share on other sites More sharing options...
GregWormald Posted November 1, 2020 Share Posted November 1, 2020 I sold my 33/303 when I left Auckland for Adelaide about 1977. (I wonder if it's my old one?) It was a great bit of gear back then, worked great with my AR 2ax speakers (also sold), and I've often wondered how it would compare these days. Keep us up-to-date please. Link to comment Share on other sites More sharing options...
muon* Posted November 1, 2020 Share Posted November 1, 2020 51 minutes ago, Soody said: cheers : ) XO's, that's the speakers? Can anyone tell anything else about them? I will open them up when I have some time and see. XO = crossover Link to comment Share on other sites More sharing options...
Graywulf Posted November 29, 2020 Share Posted November 29, 2020 On 01/11/2020 at 11:12 PM, Soody said: cheers : ) XO's, that's the speakers? Can anyone tell anything else about them? I will open them up when I have some time and see. it is highly likely they will be 'hunts' capacitors (black with red, or blue, ends) they are a known weakspot on old KEF XO's. Those speakers will likely show a noticeable 'lift' in performance with an XO rebuild. It will be worth seeing if it's a KEF, or a Falcon XO, if so Falcon did those KEF XO's so you may well be able to get a kit, or, if you feel adventurous choose the brand you want. (depending on the actual age of the speakers, it's worth looking at just what XO is in there, as from the driver line up, it looks like it could be a KEF 'Concerto' type XO (these KEF XO's have a couple of noted weaknesses, that an upgrade pair can be got from either Falcon, or, Wilmslow. 1 Link to comment Share on other sites More sharing options...
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