RuneAudio Forum

Just Sharing My Current Setup

Raspberry Pi3 Hifiberry Dac+ Pro

2 Heavily Modified Quad 405's 200W Per Channel at 4Ohms (40 Years Old)

Horizontally Bi amped

Martin Logan Aerius i Electrostatics (20 Years Old)

Nice. How did you modify the 405's? I vaguely remember there were some upgrade kits sold 10~15 years ago, but all I can see in the pic is the filter caps.

PeteB wrote:Nice. How did you modify the 405's? I vaguely remember there were some upgrade kits sold 10~15 years ago, but all I can see in the pic is the filter caps.

Input Rearranged 604 opamps current limiters modified and output transistors upgraded to 30A devices

Which output transistors, if I can ask? Thanks.

PeteB wrote:Which output transistors, if I can ask? Thanks.

Each amp drives one Electrostatic Hybrid

Left Channel Drives the Stat Panel
Darlington Pair MJ11015 and MJ11016

Right Channel Drives the Woofer
Pair of MJ15003

Thanks again!

PeteB wrote:Thanks again!

Any time its a solid setup in my opinion.

For 8ohm or 6ohm speakers the work other than psu, input and opamp work was totally unnecessary.

Those Electrostatics can dip to 0.7Ohm about 20k!!! so needed to be done.

The price of second hand quads these days its a brilliant match for headless audio.

Of cause no one likes them because they are absent of unnecessary controls, colour lcd's and blue leds

m0oml wrote:The price of second hand quads these days its a brilliant match for headless audio.

I asked b/c a friend of mine has one in the basement (not working). I will send him a link to this thread as encouragement. There were two of them, bought at a swap meet for less than $100, but his son managed to fix one by guessing and randomly replacing parts

m0oml wrote:Of cause no one likes them because they are absent of unnecessary controls, colour lcd's and blue leds

How else would you know it's working...

[/quote]
I asked b/c a friend of mine has one in the basement (not working). I will send him a link to this thread as encouragement. There were two of them, bought at a swap meet for less than $100, but his son managed to fix one by guessing and randomly replacing parts [/quote]

I Would Gladly help with the diagnosis describe not working, no power no audio or bad audio on one channel or both ??

I will try, from memory, but it may be better to wait if he decides to pick up the thread.

As I remember, there was one working channel between the two units. There was a leaking electrolytic cap in that unit. His son removed/replaced those, and a couple other caps which did not measure well with a small capacitance meter.

The amp does not have a typical output stage, but there was a signal on both channels, but output on only one. The bad channel showed a clipped signal at a low voltage when tested with a sine wave. neither channel reached anything like close to the rails. I don't think there was any diagnosis after that, not that I was a part of.

I believe his son either guessed, or read some posts on the web, and started replacing parts a couple at a time. When the formerly bad channel started to work, I believe he simply replaced the same parts in the right channel.

The other unit is not completely "dead", in terms of power supply, but no output on either channel, and no attempt at repair. That is all I can remember.

Another observation, to me personally, the output on the one working channel did not look like a perfect sine wave as the test signal was increased in amplitude, and a square wave was hardly crisp. In use this would have given it a very warm sound, like a soft clip circuit.

Regards,

Pete