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Solid state switching
Solid state switching
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Old 27th March 2020, 10:45 AM   #11
R1234 is offline R1234  Australia
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Thanks mlloyd1. This looks promising.

However, I tried to get the 915 cct., - but from 3 sites it appears to be from the same source as the pages are not quite complete although it does show the switching, and there are only 3 inputs.

I've no experience with these, can you double up the 4051 for 6 inputs ?
also, the 2SK163's appear to be obsolete.
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Old 27th March 2020, 10:51 AM   #12
edbarx is online now edbarx  Malta
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Quote:
Originally Posted by jaddie View Post
Relays? Yuk. Some things get simpler, some more complex. They aren't a free ride either.

SMD's are not impossible, just a task. Need a tiny iron and a good magnifier.
... AND above all, a steady hand! That is why, at my age, I must content myself with the old way of building electronic circuits. The older the technology, the better!
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Old 27th March 2020, 03:27 PM   #13
mchambin is offline mchambin  France
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If I had a need for this I would firstly look in purely mechanical switching.
There are plenty of rotary selectors.
Alternatively, the old push button was widely used, push one, it latches, while the others pop up thanks to a common bar.
If going CMOS analog switching I would mostly care about low R_on and flat R_on over the voltage of the audio signal. Then whatever the details, a 22V10 would do to glue things together.
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Last edited by mchambin; 27th March 2020 at 03:30 PM.
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Old 27th March 2020, 05:36 PM   #14
indianajo is offline indianajo  United States
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Quote:
Originally Posted by R1234 View Post
I've no experience with these, can you double up the 4051 for 6 inputs ?
also, the 2SK163's appear to be obsolete.
You need an inverter to drive one IC strobe so one 4051 is enabled for 0,1,2,3 and the other 4051 is enabled for 4,5
I tend to use cd4025 for inverters, as they are useful for other things too.
2sj 2sk anything are mostly unavailable in US, except a few fairchild numbers and ubiquitous counterfeits. I find the obsession of diyaudio with toshiba/sanyo/sanken semiconductors to be frustrating. And not even farnell can get a package through customs unpilfered. It took 3 1/2 weeks to get some CD4093 from UK to US SC warehouse.
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Old 27th March 2020, 08:16 PM   #15
johnhenryharris is offline johnhenryharris  United States
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How many inputs are you looking for? With just a few digital chips you can do 15 inputs controlled by small signal relays. Some people do not like relays but good relays are reliable and do not distort the signal.
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Old 27th March 2020, 10:02 PM   #16
mlloyd1 is offline mlloyd1  United States
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Solid state switching
hafler 915 has 4 audio inputs into the CMOS 4051: TUNER, VIDEO, CD, & AUX. See attached Hafler 915 snap below.

You can use other JFETs besides 2SK163; it's just a buffer. Take a look in the Pass B1 Buffer thread for comments about lots of parts that others have tried.

You can use a quad CMOS switch other than the CD4051 (such as the DG413), for lower and flatter Ron (leading to less distortion) if you want. You can also then chose a part that has higher rails for higher signal handling capability (and maybe lower distortion) if needed, but the 915 design already has the diodes to facilitate easy switching for input selection. CD4xxx logic DOES NOT handle +/-15V rails!!!

Maxim-IC makes an improved 4051 device with lower and flatter Ron, but you still are limited with the power supply. Years ago, I threw together a cheap quickie version just to use whenever I was working on my main preamps. Worked quite well.

I'm sure you can add more switches to get more inputs, just check the logic for selecting them.

have fun,
mlloyd1

Quote:
Originally Posted by R1234 View Post
Thanks mlloyd1. This looks promising.

However, I tried to get the 915 cct., - but from 3 sites it appears to be from the same source as the pages are not quite complete although it does show the switching, and there are only 3 inputs.

I've no experience with these, can you double up the 4051 for 6 inputs ?
also, the 2SK163's appear to be obsolete.
Attached Images
File Type: png hafler_915_inputs_snap.png (36.4 KB, 137 views)
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Old 27th March 2020, 10:09 PM   #17
MarcelvdG is offline MarcelvdG  Netherlands
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A 4051 is an eight-to-one multiplexer, so why would you need to do anything special for six inputs?

http://www.ti.com/lit/ds/symlink/cd4051b.pdf
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Old 28th March 2020, 03:04 AM   #18
R1234 is offline R1234  Australia
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Thanks everyone for your excellent replies.
Firstly, yes, mlloyd1 you are correct, I missed the aux 2 in my quick count !

edbarx, yes, - hear, hear, for the same reason and I suffer from "Essential Tremor" which my mother had and she only lived to 105 ! - I now really enjoy improving old technology.

Yes, edchambin, I really prefer mechanical switching & have used it for over 50 years, but, now I find I have lots of good old panels for 20mm spaced 6 gang, interlocking push-button switches, lots of other hardware, but no switches ! - I want to retain the existing metalwork to match with existing amps & tuners and I tried going on-line but I guess times have changed & no one makes these switches now or only at prohibitive prices. Hence now, my interest in alternatives. - Obviously, I need to select 6 stereo inputs. - I don't mind relays generally but they do add considerable space & complexity. (Now I see that S-S switching can do too !)

However, it is now looking like the input switching is becoming bigger than the whole pre-amp project & I may need to modify my metalwork.
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Old 28th March 2020, 12:23 PM   #19
OlegSh is offline OlegSh
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Solid state switching
Some time ago I designed this 6 way input selector PCB. The PCB size is 3x8cm and uses standard 2.5mm pin spacing connectors. The selector can be controlled by a simple rotary switch or interlocking push-buttons. The only drawback for you is that relays are SMD. I should have probably added a through hole footprints too but I did not think of it back then. Anyway, the pin spacing of these relays is not too tight (2.5 mm) so they should be doable.

Regards,
Oleg
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Old 28th March 2020, 01:21 PM   #20
synonymous is offline synonymous  United States
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On the SMD topic....

But 2 years ago I was not an SMD fan, then came in low temp solder paste to the rescue...
Put a small line of low temp paste (find it online) across all the pins and use your wifes hairdryer to heat the PCB. Within a minute or two, it will wick into a perfect soldering job all by itself. If you get too much paste on it and show a bridge here or there, just use your solder wick and iron to clean em up. Usually it's pretty rare to get too much on there, and you don't need as much as you think either. All the old parts that I used to use through-hole are junk compared to the SMD equivalent. The consistency and quality is muuuch better.
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