Fs - quad 405-2 fully net audio modded!!!

[Wakefield Turntables]

This is my Quad 405-2 which is fully modded to latest NET Audio mk 3 boards and PSU.

I had Nick Gorham mod this amp with on/off switch and a new set of RCA inputs. There is a slight hum at very high levels to the left channel but nothing that can be heard a normal listening levels. Unit is very well sorted and scratch free.

Price £375 OVNO + POSTAGE, Personal collection welcome.

NO LOW BALL OFFERS

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Thanks

A

[Wakefield Turntables]

BUMP! Open to offers.

[Wakefield Turntables]

Bump! £350 now.

[Wakefield Turntables]

BUMP £295 now want to get rid. Please buy this!

[Lawrence001]

Are you sure the hum is coming from this, in my experience any hum which varies with volume is coming from the pre amp, or a mismatch between the two units?

[Wakefield Turntables]

It's a very small amount of transformer hum.

[spendorman]

It's a very small amount of transformer hum.

Do you mean mechanical noise from the transformer? If so this does not stack up because, you also state - "There is a slight hum at very high levels to the left channel but nothing that can be heard a normal listening levels."

Some 405 transformers did suffer from mechanical noise, adjusting the tightness of the securing screws can sometimes help. I bought my 405 new in 1976, and transformer buzzed a little, did the adjusting screw thing and it's been pretty well silent since.

It's been upgraded three times, just changing the opp amps to TL071's, then to 405-2, then Burr Brown opp amps. Biggest improvement was changing the opp amps to Tl071's, cost all of a few pence!

I have also fitted phono sockets and a power switch similar to yours.

It would be great to sort the problem with yours. Have you tried the amp without any input connected, if it's quiet then, amp is probably fault free.

Nice looking amp by the way, similar condition to mine, and mine has been well cared for.

[Primalsea]

I suspect that the hum on the left channel is a non issue and nothing to worry about. The left channels circuit board is much closer to the transformer. The hum that you hear only at high levels is probably just the left preamp circuit picking up stray noise from the transformer. The transformer looks like it is wrapped in a shield and possibly just the ground connection between the shield and the chassis needs to be checked. If this doesn’t solve the issue it’s probably just noise that is inherent from having the transformer so close to the PCB and not something to worry about when listening at normal household levels.

[Wakefield Turntables]

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