Relay in audio circuit - solid state or mechanical?

I'm going to build a Calreq and I'm planning to use relays instead of switches. Should I look at the mechanical ones or do solid state suite? Any ideas?

Relays will probably be the easiest and cleanest.

Fet switching takes a lot of thought to get right.

Jakob E.

Thanks, Gyraf! Another question though... What should I look for to choose the right relay for audio?

The important parameter is minimum switching voltage and current - that is, how small signals it can switch in a predictable way.

Omron G5V-2 is an example of a nice relay for signal switching:

http://www.components.omron.com/Products-Relays.shtm

Jakob E.

if you do go SS, then use the analog devices parts, ssm2402, all the FET work is done for you for 6$ a pair of channels, that's 3$ a channel, which is less than retail for a relay.

But I see you are in Russia so I do not know which will be easier for you to get..

Thanks svart. I'll examine this ssm thing - looks interesting...

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=85466&Row=661075&Site=US

VS:

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=85922&Row=708397&Site=US


actually if you buy from Digikey here in the US, they come out to be roughly the same price.

:thumb:

[quote author="gyraf"]Fet switching takes a lot of thought to get right.
Jakob E.[/quote]

There were a couple of interesting articles in EW+WW years ago, where a certain D. Self gave an excellent overview. He also presented a few circuits using off the shelf parts that had little or no problems remaining.
IIRIC he used J20X JFETs and a few additional components to get things right.
These were still elegant designs, but while those mentioned SSM-ICs might qualify less as 'DIY', they're indeed more convenient.


The Groove Tubes / SWR school seems to be fond of opto-switching for signal routing. I'm not sure what they're actually used in older products, but it could now be done easily with those photo fet optocouplers like H11F1 etc (perhaps even simpler than those SSM-ICs).

Regards,

Peter

Some more w.r.t. FET-switching (now CMOS i.s.o. JFET):

The TC-EQ-schematic presented by Jakob a while ago had some nifty use of the CD/HEF4007. Still more elaborate than SSM, but interesting to have a look at.
As people will know the 4007 IC has six MOS-devices, 3 N-, 3 P-type and is often used in FX-pedals to realize the footswitch-interface and signal switching with one cheap 14-pin IC. The TC-circuit takes this idea further.

Regards,

Peter

Also look at the DG4xx series cmos switches.

A bit better than the older stuff. Also keep voltage across the switch to a minimum for best performance.

Cheap enough, at about $1.50 for the intersil parts.

I am actually sitting here with 8 Omron G6A 234P 12vDC relays on a PCB board - that the company downstairs are going to throw away
I rescued it for desoldering - they also have approx 60-100 they may have to bin (lead in them) - so I gave them my number and said - no! call me first

ahhh - lovely
BTW - none of this stuff is SMD
Loads of chips on there - (they make control boards for train systems)

Those SSM chips look very convenient. And easy to implement - that's very important since I'm still not very good at electronic design, so I need something very simple, yet effective.

The SSM chips are convenient to use - as they include the soft switching to ensure clickless switching - which can be very important and sometimes difficult to implement using DG series and discrete FET's.

If using relays - and they are still very useful for signal switching - go for Telecom approved types - they are inexpensive as they are made in huge volumes, normally have gold contacts - and are reliable....

I like the BT 47 type, which is available from Omron, NEC, Fujitsu, Siemens and many other manufacturers - standard PCB pin outs and coil voltages.

Sometimes a pair of genuine change over contacts is useful - if using both sets, a very high isolation audio switch can be made. Off really is off....!

JG

[quote author="Svart"]if you do go SS, then use the analog devices parts, ssm2402, all the FET work is done for you...[/quote]

Svart! Could you please correct me if I'm wrong. Is it sufficient to connect a switch and a voltage divider to obtain something about +5V at the control input of the SSM chip? And no additional circutry? And I guess I don't need a separate power rails for SSMs, right?