From: Bob Blick <bobblick@outlook.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Tue, 28 Apr 2020 13:31:29 -0700
Subject: Re: [EE] Seeking audio relay advice
Thread-Topic: [EE] Seeking audio relay advice
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Hi Manu,
Analog switches are definitely the right way to do it, but I don't want to =
change the sonic character of the preamp. And it would make it harder to se=
ll if I decide to get rid of it. Although it's not a particularly desirable=
 model to begin with, and its performance is only so-so. It even has some 4=
739 opamps, which I quickly grew to hate back when I was doing studio tech =
work way back in time.

The matching power amplifier I have, a Phase Linear 400 S2, also has some h=
orrible design "innovations". The input stage is an LF356 opamp, followed b=
y a common-emitter voltage amp stage and quasi-complementary output stage. =
These amps were known to be fussy about long speaker wires and certain loud=
speaker loads. But it has pretty LED meters :)

Friendly regards, Bob

________________________________________
From: piclist-bounces@mit.edu <piclist-bounces@mit.edu> on behalf of Manu A=
braham=20
Sent: Tuesday, April 28, 2020 12:49 PM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Seeking audio relay advice

Hi Bob,

More food for thought ..

While it might not be as good as gold plated contacts, or a relay:

Having a TS5A3159 on a small breakout board that fits the size of the
physical relay on the PCB, might be a possible solution.
https://www.ti.com/product/TS5A3159

Mentioned the TS5A3159 as a reference point to start with, you could
use other analog switches as well.
Just to provoke your thoughts. :-)

Cheers,
Manu



On Tue, Apr 28, 2020 at 11:56 PM Bob Blick  wrote:
>
> Thanks everyone who replied and for the suggestions. I decided to take th=
e chance and for $26 I have 20 HB2E-DC24V relays coming from an Aliexpress =
vendor. Although I'm sure what will show up will be relays, whether they ar=
e counterfeit or used is unknown at this time. The picture and description =
seem correct.
>
> As to the question about the failure mode, it's a contact issue, and the =
symptoms are distortion, noise, and signal dropping out. Cycling the tape m=
onitor and input selectors clears it up for an annoyingly short time. When =
I originally got the unit I popped the tops off the relays(this unit has th=
e original Omron unsealed relays) and squirted Cramolin, that worked for a =
month or so.
>
> This is a preamplifier, so the signals are all low level audio under 2 vo=
lts AC, and very low current. So it's the textbook low current dry contact =
problem.
>
> I love the idea of hacking the relays apart and putting reed switches int=
o the the original magnetic structure. Maybe I'd try it if I didn't have to=
 do it for 13 relays, each requiring two SPDT reed switches!
>
> In 2 months when the relays finally arrive from China I'll post a reply w=
ith what showed up and if they work.
>
> Cheerful regards, Bob

--=20
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