On the original quad 405 the rca input ground is connected to the chassis, is this necessary for these LJM boards
It is easy to get ground loops if you connect both inputs to chassis. Usually, the RCA's would be isolated from chassis and there would be a single connection from the PSU ground to the chassis. Any mains protective earth needs to be securely fixed to chassis.
Each case is different though depending on the fine details.
Each case is different though depending on the fine details.
No it isn't. The original Quad 405 didn't have RCA inputs. It had a 4-pin DIN socket, whose ground was connected to chassis ground via R2, a ground lift resistor.
A lot of users subjectively saying that FET input amplifiers (opamps included) are having a more laid back and smooth sound compared to their bipolar counterparts.
I bought this bare version of the board as in post #300, I am pretty sure I have populated it correctly but when I connect it to my 405 power supply -53v +53v what I think is r23 1k2 becomes really hot and smokes a little, can anyone tell me what the issue may be?
Attachments
A few 405-2 clones making their appearance, supposed to be a modern updated version based on the quad 405-2 design:
https://www.ebay.co.uk/itm/393440055285?hash=item5b9adacff5:g:Z5AAAOSwzZtg7TCE&amdata=enc:AQAHAAAA4FOp7UeA2k8fZgU9vo2DwvfdrX9C5Mgi9ZdYjsxu8KyaTSsS9/K99r7rFr9oF1S7iHmxjsfeR/1eVLiuAs/jnkfO6IAMyJ2WDHCv1ATlMoZoe/OdCGMhac60mStdJyDlyz+hMgYQFMbLH8YnOs4f2+fKvVwKlPBEZ8TNi+HR+6NnyQaq5sth14jqJLTTxpFd/8D7FTUFvdLNFh5zVzREPxdDCZ2vjB9wgnlI5TWKICkxH8XM3NLelA6zeBG8Ief7zXPGWdSvQFn7UyPsvOMUpUoBjsWD62IUrSAPUnbVeoe1|tkp:Bk9SR-rk5u6RYQ
https://www.ebay.co.uk/itm/284028055621?hash=item4221643045:g:8W8AAOSwDyxhOFeW&amdata=enc:AQAHAAAA4O93bx9xbl96MqKIycK2O5plz0rZhYl25fLQkijv3Eyw05VM4dF4tgw62Bxbo1fWjmU5F/IJUnrpsjUUP8vJlVlV81LhLDmSPhjrf3fQxrVYrFtuXSrgQZYXxSzlcPA0IOsW53k9mlxwFly1t6JpjXxeZoIK+WuFWFtAp2LEyFikxHyk0mF01MAyjMzArzH4c4tjXoyuATMXx0u4id9RQi2V0WGUX0TkXbtlzCpSpF69clJ1NELPQc+46NjV/6EDvq9dX2K+/eH6vZYXTl5KFgH58bpYsPipccAXWzz3l6lH|tkp:Bk9SR-Tk5u6RYQ
https://www.ebay.co.uk/itm/273239232783?hash=item3f9e53d10f:g😱DIAAOSw945bCjE9&amdata=enc:AQAHAAAA4IrW+xu7hA5rBjGOgQ9AisPsUIn3qdKN/XUtxJ1sKOD/KpHTSxLWtczEiSAtW/xUUr8U2p1qlr0xRH04w9r4ZS5VL4NIY7DzPmNx0/HR98GKhKKE+bQObjMyHERTlfWTr0V64jHfbbRfwcg8Rn0ZsylnuqlDRbCexPlyXcjZJAV4S+ZbTMDMgrbT0RGo/zA8lyd1zFbaxxY7G2sJUvla7zZmFuHd34RVFet+oVgTibjemJN1ev4zKRYukCDY+3NcqvmeCNYNsBh4P193m+2bR+Ozo1qrWLexJwIDYWj5hUY/|tkp:Bk9SR-Tk5u6RYQ
https://www.ebay.co.uk/itm/393440055285?hash=item5b9adacff5:g:Z5AAAOSwzZtg7TCE&amdata=enc:AQAHAAAA4FOp7UeA2k8fZgU9vo2DwvfdrX9C5Mgi9ZdYjsxu8KyaTSsS9/K99r7rFr9oF1S7iHmxjsfeR/1eVLiuAs/jnkfO6IAMyJ2WDHCv1ATlMoZoe/OdCGMhac60mStdJyDlyz+hMgYQFMbLH8YnOs4f2+fKvVwKlPBEZ8TNi+HR+6NnyQaq5sth14jqJLTTxpFd/8D7FTUFvdLNFh5zVzREPxdDCZ2vjB9wgnlI5TWKICkxH8XM3NLelA6zeBG8Ief7zXPGWdSvQFn7UyPsvOMUpUoBjsWD62IUrSAPUnbVeoe1|tkp:Bk9SR-rk5u6RYQ
https://www.ebay.co.uk/itm/284028055621?hash=item4221643045:g:8W8AAOSwDyxhOFeW&amdata=enc:AQAHAAAA4O93bx9xbl96MqKIycK2O5plz0rZhYl25fLQkijv3Eyw05VM4dF4tgw62Bxbo1fWjmU5F/IJUnrpsjUUP8vJlVlV81LhLDmSPhjrf3fQxrVYrFtuXSrgQZYXxSzlcPA0IOsW53k9mlxwFly1t6JpjXxeZoIK+WuFWFtAp2LEyFikxHyk0mF01MAyjMzArzH4c4tjXoyuATMXx0u4id9RQi2V0WGUX0TkXbtlzCpSpF69clJ1NELPQc+46NjV/6EDvq9dX2K+/eH6vZYXTl5KFgH58bpYsPipccAXWzz3l6lH|tkp:Bk9SR-Tk5u6RYQ
https://www.ebay.co.uk/itm/273239232783?hash=item3f9e53d10f:g😱DIAAOSw945bCjE9&amdata=enc:AQAHAAAA4IrW+xu7hA5rBjGOgQ9AisPsUIn3qdKN/XUtxJ1sKOD/KpHTSxLWtczEiSAtW/xUUr8U2p1qlr0xRH04w9r4ZS5VL4NIY7DzPmNx0/HR98GKhKKE+bQObjMyHERTlfWTr0V64jHfbbRfwcg8Rn0ZsylnuqlDRbCexPlyXcjZJAV4S+ZbTMDMgrbT0RGo/zA8lyd1zFbaxxY7G2sJUvla7zZmFuHd34RVFet+oVgTibjemJN1ev4zKRYukCDY+3NcqvmeCNYNsBh4P193m+2bR+Ozo1qrWLexJwIDYWj5hUY/|tkp:Bk9SR-Tk5u6RYQ
I wanted to say the same, Quad 405 it is not a class A amplifier and when it works as planned should not get too warm.
This is the part that I like the most, for my casual listening it is becoming barely warm and I have small heatsinks.
This is the part that I like the most, for my casual listening it is becoming barely warm and I have small heatsinks.
Any thoughts on the quad 405-2 that i put up? I owned a pair of 405-2 boards a few years ago and these updated ones look different. The LJM boards that this thread is about sound excellent, wondering what the chinese have done to the 405-2
Thanks !
Thanks !
I would love to see someone put the effort in and get rid of that dirty input opamp, they quickly got rid of it in quad 606 and 909 upgrades, very unpopular.
If these boards are class-A, 2 x 100 watts, that's a lot of heat to get rid of.
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I don't think the opamp is to shame if you use a modern equivalent and redesign the circuitry like Keith Snook. For sure, the output stage in not class-A!
hi all
pls help share quad405 clone bom part
im confused about resistor velue watt 1/4 or 1/2?
best regard
RG
pls help share quad405 clone bom part
im confused about resistor velue watt 1/4 or 1/2?
best regard
RG
Don't think it makes any difference, you can use as high a wattage as you want. I used cpf2 resistors which are 2 watt resistors, small footprint, the same size as most half watt resistors