Quad 405 amplifier

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ben62670
ben62670 Posts: 15,969
edited March 2008 in Electronics
Anyone ever get their ears on one of these? They are a pretty simple design. Currant dumping. The price for 2 boards was about $20 bare. My old JVC receiver has a transformer that puts out near ideal voltage for it. So I decided to build a fun little cheap project. A few guys have modded these to remove the currant limiting, and use better TO-3 trannies (which I already had). Its going to take some time due to lack of funds, and it is so hard to find suppliers that have all the pieces in one store to purchase. This kills the super cheap build price BTW.
Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
Thanks
Ben
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  • Systems
    Systems Posts: 14,872
    edited March 2008
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    Haven't heard em but they are a classic design.I bet Selfs audio pages will have detailed info on the current dumping circuit used.
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  • dorokusai
    dorokusai Posts: 25,640
    edited March 2008
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    I'm hot rodding one right now.
    CTC BBQ Amplifier, Sonic Frontiers Line3 Pre-Amplifier and Wadia 581 SACD player. Speakers? Always changing but for now, Mission Argonauts I picked up for $50 bucks, mint.
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  • ben62670
    ben62670 Posts: 15,969
    edited March 2008
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    dorokusai wrote: »
    I'm hot rodding one right now.

    Here is a linky for you.
    http://www.diyaudio.com/forums/showthread.php?s=&threadid=109771

    Did you get to hear it before, or was it broken?
    Thanks
    Ben
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
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  • dorokusai
    dorokusai Posts: 25,640
    edited March 2008
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    I have all the schematics and mod information. I didn't bother since the caps were bulging a little. It's just for fun.
    CTC BBQ Amplifier, Sonic Frontiers Line3 Pre-Amplifier and Wadia 581 SACD player. Speakers? Always changing but for now, Mission Argonauts I picked up for $50 bucks, mint.
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  • Systems
    Systems Posts: 14,872
    edited March 2008
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    May I ask where you scored the blank PCB's from,was it a group buy?Also I dont have win zip so cant see the schem that was posted.It certainly looks like it is low parts count for an amp.If I could get the PCB's I d like to built a pair of channels.
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  • ben62670
    ben62670 Posts: 15,969
    edited March 2008
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    http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=350029485751&ssPageName=MERC_VI_ReBay_Pr4_PcY_BIN_Stores_IT&refitem=350039899477&itemcount=4&refwidgetloc=active_view_item&usedrule1=CategoryProximity&refwidgettype=cross_promot_widget&_trksid=p284.m184&_trkparms=its%3DS%252BI%252BSS

    This is where I am starting from. The inductors are the hardest things to find.
    They are getting silly money for a 70's vintage amp on ebay.
    A search for quad 405 brings some up. One is going for almost $1500 NIB. It seems like $400 is the going price. Well I figured a cheap n easy project to play with.
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
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  • Systems
    Systems Posts: 14,872
    edited March 2008
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    So they came from China.How long did they take to arrive?I have some 2mh coils that might be fine for use in that output filter.I cant see the schem,what value is stated for the coil?
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  • ben62670
    ben62670 Posts: 15,969
    edited March 2008
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    GV#27 wrote: »
    So they came from China.How long did they take to arrive?I have some 2mh coils that might be fine for use in that output filter.

    About 30 days. I emailed the guy, and a few days later they showed up. I don't know if I was lost in the shuffle, or what. If you do decide to build it I have some beta matched outputs I can send your way.
    I do however recomend this
    http://cgi.ebay.com/STEREO-AUDIO-POWER-AMPLIFIER-KIT-BASED-ON-QUAD-405_W0QQitemZ350039899477QQihZ022QQcategoryZ39783QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
    then doing the mods.
    This guy has great prices on power caps, transformers, and jacks.
    http://www.apexjr.com/capacitorsR.html#Computer
    I just check there every once in a while to see whats new.
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
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  • Systems
    Systems Posts: 14,872
    edited March 2008
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    ben62670 wrote: »
    If you do decide to build it I have some beta matched outputs I can send your way.
    Thanks Ive got you covered for filter caps (15000,63 volt) if you need em.I see in the pic each board has three coils,what are the values? And what are the DC rail voltages?Sorry for all the questions.:)
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  • ben62670
    ben62670 Posts: 15,969
    edited March 2008
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    You might need those caps for your self. The rails are 50vdc L1 is 6.8u L2 is 3u, and L3 is 6.8u.
    Ask away. I am getting some cables finished so my responses may be a little slow.
    I can email you the PDF with the modded components. It is actually less components with the mod than without. The Original TO-3's probably couldn't dissipate the heat the newer ones can so you can drop the currant limiting right out, and the signal transistors have higher gains so they recommend omitting one set of trannies. The design is 100wpc 8ohms class A upto the output stage.
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
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  • Systems
    Systems Posts: 14,872
    edited March 2008
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    ben62670 wrote: »
    I can email you the PDF with the modded components.
    Sure Id appreciate that.As for the coils I'll check my Digi key catalog and see if they have them.
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  • Systems
    Systems Posts: 14,872
    edited March 2008
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    Thanks Ben for the pdf.It looks like a nice and simple design made so mainly by the use of the IC op amp for the input stage and only two output transistors.However I may opt to build an Aleph 3 (or 5) instead as it also has a fairly low parts count.It will depend on how hard it is to source some the parts.
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