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Post by PinkFloyd on Aug 21, 2013 19:07:49 GMT
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Post by PinkFloyd on Aug 21, 2013 20:04:07 GMT
A beauty that may be making it's way to Japan
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Post by Deleted on Aug 21, 2013 22:07:38 GMT
I still love this older Quad stuff. Perfect? No. Damn good value, built like a battle ship AND to last, hell yes.
FM4, 34, 44, 306, 405(I or II), 606. The very peak of Quad-ness. All turned to shite with the 66 series.
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Post by Deleted on Aug 21, 2013 22:12:58 GMT
BTW, Mike,
When I substituted OPA2134s into my Claymore that used TL072s, is was a definite backwards step and the 72s went back in. Admittedly they were in the pre-amp section. I assume you find the opposite to be true for the 405?
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Post by PinkFloyd on Aug 21, 2013 22:38:31 GMT
Hi Chris..... no point putting 2134 in a quad.... it won't work single channel chips in the quads.... a properly optimised OPA134 absolutely SHITS all over a TL071, any day of the week... absolutely ZERO doubt about that.
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Post by Deleted on Aug 21, 2013 22:47:17 GMT
Hi Chris..... no point putting 2134 in a quad.... it won't work single channel chips in the quads.... a properly optimised OPA134 absolutely SHITS all over a TL071, any day of the week... absolutely ZERO doubt about that. Mike What are the TO3 output devices in the Quad? Alex
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Post by Deleted on Aug 22, 2013 2:02:32 GMT
Hi Mike,
That's great work you do. Sam should be very happy.
regards
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Post by PinkFloyd on Aug 22, 2013 10:18:07 GMT
Hi Chris..... no point putting 2134 in a quad.... it won't work single channel chips in the quads.... a properly optimised OPA134 absolutely SHITS all over a TL071, any day of the week... absolutely ZERO doubt about that. Mike What are the TO3 output devices in the Quad? Alex Hi Alex, You should make them out from this photo
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jonclancy
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Post by jonclancy on Aug 22, 2013 23:35:00 GMT
Very tidy work, Mike. I like the wiring - very Quad!
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Post by PinkFloyd on Aug 23, 2013 9:25:39 GMT
Very tidy work, Mike. I like the wiring - very Quad! Yeh, I was going to redo the wiring but then thought "why?"..... it's perfectly good, quintessentially "Quad" and nice and colourful They're great amps to work on Jon, just a matter of unbolting the boards and out they pop!
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Post by PinkFloyd on Aug 23, 2013 21:23:22 GMT
Hi Chris..... no point putting 2134 in a quad.... it won't work single channel chips in the quads.... a properly optimised OPA134 absolutely SHITS all over a TL071, any day of the week... absolutely ZERO doubt about that. Mike What are the TO3 output devices in the Quad? Alex What do you reckon Alex..... room for improvement? Personally, I'd keep them, more is sometimes "less" when you want to keep the house sound of a particular brand..... it's a fine line between evolution and a reinventing of the wheel. Mike.
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Post by PinkFloyd on Aug 23, 2013 21:45:13 GMT
Sam is experiencing "grainy" mids..... maybe a retrofit of the TL071 opamps or a simple case of burn in..... I would tend to allow her a GOOD 200 hours to blossom.
Those 22000uf Caps are Mama Honkers and will take some time to "form"........ comments appreciated.....
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Post by Deleted on Aug 23, 2013 23:36:20 GMT
Mike What are the TO3 output devices in the Quad? Alex What do you reckon Alex..... room for improvement? Personally, I'd keep them, more is sometimes "less" when you want to keep the house sound of a particular brand..... it's a fine line between evolution and a reinventing of the wheel. Mike. Hi Mike I was curious about whether they could be further improved, but a search on those devices came up empty. Perhaps they were specially made for, or just specially labelled for Quad ? Some from that era had a very low Ft. The grain isn't going to be coming from the OPA134. It's a nice device.I wonder if there is some crossover distortion that a slightly higher bias may help with ? Kind Regards Alex P.S. Those mama honker electros could take a week or more to settle down.
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FritzS
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Post by FritzS on Aug 26, 2013 18:19:06 GMT
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Post by PinkFloyd on Aug 28, 2013 8:52:15 GMT
Thanks Friedrich, I've had a good read of most of those articles but they seem to take the mods very far..... I'm basically doing a recap and swapping out the opamp for an OPA134. I think I may have possible found out what was causing the graininess in the mids..... I have fitted one of the electro's (on both boards) the wrong way round..... thankfully NOT one of the big Mama honkers! Further to the above I have also fitted class Y2 caps from L/N to ground (as well as the class X2 between L/N) and I have bypassed the mama honker power caps with a polypropylene and a russian paper in oil cap. Next up I will be replacing D1 & D2 with 1N4744A 15V / 1.3W Zener diodes and will decouple D1 with a 220uF / 35V electrolytic. Will also be adding an MPSA42 wich apparantly stops the thumps at "power off" by regulating the +ve supply. These really are super amps and the possibilities are endless but all Sam wanted was a recap so I better not go too far with it He actually likes the way it sounds now which is great, it's nice to see a man who is happy with what he has got and has been happy with it for decades too Not like us lot who would probably replace every single part of it I've enjoyed working on it so much I may even get one for myself, they are classics for sure and pretty much bullet proof.... a very well designed, and made, English amp that will go on forever, I can see why they have such a staunch brigade of followers. The stock opamp in this one was NOT the TL071..... it is the UA301ATC..... quite odd though as one channel had the UA301ATC fitted and the other channel had an LM301AN fitted. I assume the UA301ATC and LM301AN are the same thing but you would assume they would have fitted the same chip / from the same manufacturer in each channel wouldn't you? Typical British design though, they fitted whatever they had on the shelf back on the day
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Post by Deleted on Aug 28, 2013 19:39:14 GMT
Hi Mike, guess what was in my old Quad 405................now replaced with OPA134
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Post by PinkFloyd on Aug 28, 2013 19:52:51 GMT
Done a little bit more to it today and then listened to it, this is a damned decent sounding amp! After refitting new electros, the correct way round this time, the sound was a lot cleaner in the mids so this must have been what was causing the graininess that Sam was describing..... I also removed the 100nF ceramic bypass caps from the OPA134 and replaced them with EVOX 100nF polyprops. There are SO many conflicting mods and variations of this amp (board revisions etc.) that I have decided to do the mods to my own "ears" and disregard all the info on the net because if you implemented ALL of the individual tweaks you come across the fekkin' amp would EXPLODE..... one guy says 1uF another says 220uF, one says short out R9 another says do "NOT" short out R9...... half of the the things they are doing are basically trying to design a new amp..... Sam wants the sonic character to remain the same so I'm trying to do that, in small steps, BUT give him a bit more clarity at the same time. His biggest gripe was the hum that the 405 had, I have got rid of that totally, it seems a common problem with them and I will publish my "fix" as soon as the entire job has been completed, I have always been a great believer that capacitors have a "house sound" and also KNOW that you can tune that house sound by using certain methods. The power caps (although not yet fully formed) were sounding a bit dry to my ears (maybe this is what Sam was hearing as "grain") so I experimented with a few bypass caps and ended up with the 22000uF / 63V VISHAY electrolytics bypassed with a polypropylene, a polystyrene and a Russian paper in oil..... the sound is a lot more fluid now.... again, I will publish the "values" of bypass caps used when I do my final write up, once the mods are completed. Here are the bypassed "multicap" Vishay 22000uF's in situ: This was done with a very hot iron so those electrolytic cap bolts are effectively unable to "ever" come loose..... consider the multicap 22,000uF caps as "all in one" tuned units Most guys have gone from the stock 10,000uF up to 15,000uF but the rectifiers can handle 22,000uF no problems (I wouldn't go any higher though!).... there are only 5 millimetres of clearance between the top of the 22,000uF Vishay caps and the lid so I reckon this is the max you will get on board...... I have, of course, bonded non conductive discs onto the enclosure lid to ensure there will never be an electrical contact, even with an elephant standing in the lid I have added to my class X2 "across the line" suppression cap..... there is now a 275VAC varistor AND I have added a class Y2 module which goes from live to earth and neutral to earth...... all bonded onto the side of the transformer..... you can see it here: Another small, yet worthwhile, addition IMO...... the noise floor is greatly reduced.... a relatively cheap tweak and well worth doing IMO. Just awaiting some zeners and that will be the job complete..... I'll let Sam do the write up on the SQ as he's the one with the Quad preamp..... I've been using my old NAD C326BEE as a preamp, far from ideal, but good enough to pick up on improvements. One final thing...... hum can be a problem with these AND there is a fix (which I will divulge as soon as all is complete) but the worst thing you can do is sit your preamp directly on top of your power amp! get that puppy a good foot away (at least)..... the two transformers don't like to sit on top of each other That's not my "hum gone" 405 fix (where both CAN sit on top of one another in total silence) but it's a free tip until I put my "hum gone" module onto the market
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Post by PinkFloyd on Aug 28, 2013 20:32:27 GMT
Before you ask....... No, I will not be offering a kit..... this is a "one off" for a friend..... a lot of research and cross referencing schematics has taken place here..... this is a truly tuned unit and cannot be replicated with a kit of parts. This is being done for a friend and is a total "one off". Mike. I'll publish my "hum gone" tweak though
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Post by PinkFloyd on Aug 28, 2013 20:35:58 GMT
Hi Mike, guess what was in my old Quad 405................now replaced with OPA134 I trust you bypassed the relevant pins on OPA134 with 100nf CAPS Alan? Those two random opamps are typical British "off the shelf" style..... no such thing as matching parts, whatever they had to hand would do...... I measured the two out of Sam's amp and they weren't even "closely" a pair Pretty bad really but maybe that's what made the "quad" sound.... mismatched channels
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Post by PinkFloyd on Aug 28, 2013 20:49:30 GMT
I'll take a photo of the two that came out of Sam's amp in daylight...... chalk and cheese
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Post by PinkFloyd on Aug 29, 2013 22:30:45 GMT
D1 @ D2 diodes arrived today. Will be bypassing them with 1uF film caps..... will show the boards when completed.The two 4amp slow blow fuses are best removed and replaced with "modern" 4amp (T) slow blow types.... it's also a good idea to suck off all the old solder from the board and reflow with fresh solder..... I'll be using 60 / 38 /2..... there's a lot of oxidisation going down with these old amps ;0
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Post by PinkFloyd on Aug 30, 2013 18:55:34 GMT
Finished off what I call my super power multicap today It comprises of a mama honker 63V /22,000uF Vishay electrolytic and is multicapped on the top terminals with 1 x polypropylene. 1 x polystyrene, 1 x paper in oil (Russian) and one silvered Mica..... this is the power house for the amp and a lot meatier than the paltry little 10,000uF that QUAD fitted..... the multicaps on top totally transform the sound, giving more fizz and energy than the stock 22,000uF alone. Here are a couple of photos of the completed super power multicaps: WARNING! Sam, don't try the screwdriver across the terminals trick anymore as you will likely end up welding your screwdriver onto the terminals and witness a nice big spark! The caps are starting to form now and I'll put another 48 hours into them before I hand you the amp back. The diodes have been changed for 15V zeners..... I have decoupled D1 with a 150uF / 35V electrolytic and have connected the positive side of the cap to the cathode of the diode, this will get rid of the switch off noise that is inherent with the 405. I have decoupled D2 with a 100nF film cap. It's almost ready to go, just have to change C2 over to a non polar type and am awaiting the 2K7 2 watt resistors..... it looks untidy on the bottom of the board but there's not a lot you can do to make a tidy job with those old style PCB's.
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Post by PinkFloyd on Aug 31, 2013 20:35:53 GMT
What do you reckon Alex..... room for improvement? Personally, I'd keep them, more is sometimes "less" when you want to keep the house sound of a particular brand..... it's a fine line between evolution and a reinventing of the wheel. Mike. Hi Mike I was curious about whether they could be further improved, but a search on those devices came up empty. Perhaps they were specially made for, or just specially labelled for Quad ? Some from that era had a very low Ft. The grain isn't going to be coming from the OPA134. It's a nice device.I wonder if there is some crossover distortion that a slightly higher bias may help with ? Kind Regards Alex P.S. Those mama honker electros could take a week or more to settle down. Alex, Let's seriously put this into perspective based on our database of combined knowledge..... how many hours of "signal" should Sam's freshly recapped 405 go through before it's in a fully "formed" state to compare his 405 MKll with? I have suggested a minimum of 100 hours...... it's had about 2 hours on it and he is already evaluating it against the MKll MY advice is to let it fully form (there were a LOT of cap changes) and start comparing the two after a momth or so..... we all know how it all starts to kick in after a while at the moment, all is fine BUT the bass is a bit lacking compared with the MKll...... erm, just wait until those Mama Honkers fill up with juice Your comments appreciated. My personal recommendation has always been to allow a minimum of 100 hours with a signal flowing through the circuit (whether it be radio 2 or lady gaga) this will give the caps a chance to cycle / form / juice up. I'm quite annoyed with Sam, he has already compared his newly capped 405 to his "juiced up" 405 / 2....... Some people say 500 hours but I reckon 100 hours is more than enough for a cap to juice up and establish an electron pathway. What do you guys think?
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Post by Deleted on Sept 1, 2013 1:13:37 GMT
Mike Personally, I would have waited for at least 100 hours of use before adding all the additional bypassing across them. The low end may very well be there already , but additional HF detail MAY alter the perceived overall balance. However, when you are doing mods for somebody else, you rarely have the luxury of retaining the item long enough to hear the final result with large electros fully stabilised. I have been told that the big green Elna for Audio electros can take months to fully settle down.. Regards Alex
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Post by PinkFloyd on Sept 1, 2013 10:46:42 GMT
Mike Personally, I would have waited for at least 100 hours of use before adding all the additional bypassing across them. The low end may very well be there already , but additional HF detail MAY alter the perceived overall balance. However, when you are doing mods for somebody else, you rarely have the luxury of retaining the item long enough to hear the final result with large electros fully stabilised. I have been told that the big green Elna for Audio electros can take months to fully settle down.. Regards Alex That's the problem Alex.... with a head amp you can generally listen to the same headphones the customer has at home but with a loudspeaker based system it's totally different.... the customer doesn't generally turn up with his entire system and you don't want his entire system in your home ..... you just have the the amp to work with and have to kind of guess what it's going to sound like in the customer's system..... anyhoo, I'm sure the bass will appear as soon as everything starts to form
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