Switching of the phono inputs

the road not taken.
Post Reply
jarek
Posts: 62
Joined: Wed Feb 02, 2005 10:02 am

Switching of the phono inputs

Post by jarek »

Hi all!

I don't know if the topic has already been discussed (if so apologies for not searching hard enough :):

how to switch phono inputs?

For some time I've been chewing on the idea of using Hg-wetted thermocouple reed relays. They are supposed to be designed for switching microvolt signals, generate ultra low noise and Hg makes the contact very low impedance (I attach a pdf datasheet of Rhopoint family).

I'd like to possibly have several different SUT's for different cartridges with optimised loading schemes for each cart and I'd place the relays in the secondaries, where the voltage level is higher--I attach the drawing. The rails would be controlled by switching 5V (or 12V) to their coils, thus closing the contacts. By such a scheme, the input switch can be anything. If it all works, I'd love to try a volume control switch build like that. It'd be expensive and big, but maybe worth it...

Has anybody tried anything like that? Any thoughts?

Cheers,
jarek
Attachments
3500.pdf
Rhopoint thermocouple reed relays
(366.58 KiB) Downloaded 342 times
switching.pdf
jarek's phono switching idea
(66.58 KiB) Downloaded 342 times
dave slagle
Posts: 2085
Joined: Sat Jan 22, 2005 3:54 am
Location: NYC
Contact:

Post by dave slagle »

hey Jarek,

I like the idea of the mercury relays... they should be the least painful in this situation.

image of Jarek's PDF is below.

dave
Attachments
Screen shot 2012-08-26 at 10.20.16 AM.png
Screen shot 2012-08-26 at 10.20.16 AM.png (83.31 KiB) Viewed 14969 times
Get Your Fix
www.hifiheroin.com
jarek
Posts: 62
Joined: Wed Feb 02, 2005 10:02 am

Post by jarek »

Thanks Dave! I've never seen anything more advanced than a mechanical switch at the phono input. If anyone has any experience with thermocouple
relays, I'd be interested to learn. I've contacted Rhopoint, since Hg-wet are not standard. Let's see what they quote...

BTW, how do you guys deal with multiple arm/cart switching?
jarek
Posts: 62
Joined: Wed Feb 02, 2005 10:02 am

Post by jarek »

There is also this military toy:

50GB5N-1-A700

which I've found through diyaudio: http://www.jogis-roehrenbude.de/Verstae ... 33C-VV.htm

Hard to get any reasonable datasheet, not written in the military language. There is a whle family 5GB5N. It seems to be hermetical, Hg-wetted and not a reed: the signal will not pass through the coil like in the Coto/Rhopoint 3500 series...and it seems to be used by Gulfstream Aerospace, whew!!

I was also wondering, given the coil rating choice, like with Coto/Rhopoint, what would be the optimum one and I came to a conclusion that higher voltage/lower current coil should impact less (less stary field produced by lower current).
IslandPink
Posts: 56
Joined: Thu May 12, 2005 8:01 am
Location: Denbigh, North Wales

Post by IslandPink »

I may be seen as a party-pooper here, but I seem to remember Thorsten Loesch reporting bad results from using mercury relay switches in a pre-amp or phono amp .
Unfortunately I wasn't able to find the comments with a quick search, as his site & pages have recently disappeared ( the 'Fortunecity' ones ) . There are extracts of the pages now on other sites, eg. VT52 .
Maybe someone can locate the comments, which I think were on the pages relating to the Toccata phono or Claret pre-amp .

Anyway, may be best to test this option first using an existing phono, before committing too much design/hardware to the idea .
jarek
Posts: 62
Joined: Wed Feb 02, 2005 10:02 am

Post by jarek »

Thank you Island! This is just an idea, which may as well be a no-go. Everything depends on how much I get quoted for those toys to be able to experiment. I got a quote for 50GB5N...630$/pcs (!!!!)...maybe ok for a Gulfstream Jet, but I recon too much even for an Allnic H3000...speaking of the later they do somehow switch the phono inputs there.

PS I'm looking for the said comments and seem to find something seemingly on the contrary, albeit not direct...hmm...

http://www.audioasylum.com/forums/bottl ... 13375.html
http://www.raylectronics.nl/pdfs/Thermi ... stages.pdf

and here are some comments on the relays used:

http://www.arduman.com/aa/sayfalar/thor ... orsten.htm
--gold contact, innert gass filled hermetical tube, probably a latching type, so that the coil is activated only for a short period
this is in fact my 2nd direction of investigation

and his commercial use:

http://www.6moons.com/audioreviews/abbi ... ngdon.html
IslandPink
Posts: 56
Joined: Thu May 12, 2005 8:01 am
Location: Denbigh, North Wales

Post by IslandPink »

Good ! - thanks for the links .
Could be, after further thinking, it may have been one of my friends who tried what Thorsten had done with the relays, but didn't like the sound himself .. but then he is notoriously fickle !

Is it not possible to find a few examples of these relays NOS or loan from others, to test, instead of spending big bucks ?
jarek
Posts: 62
Joined: Wed Feb 02, 2005 10:02 am

Post by jarek »

IslandPink wrote: Is it not possible to find a few examples of these relays NOS or loan from others, to test, instead of spending big bucks ?
I'm trying, with little success so far--neither Rhopoint nor few other replied.
I understand that Hg-wtted would be hard to get in EU due to some idiotic fantasies of EU bureaucrates...
jarek
Posts: 62
Joined: Wed Feb 02, 2005 10:02 am

Post by jarek »

Here is one more specimen:

http://www.torontosurplus.com/midland-r ... 00014.html

Interesting that it's supposedly latching...but getting any datasheet seems impossible
jarek
Posts: 62
Joined: Wed Feb 02, 2005 10:02 am

Post by jarek »

I've found a detailed pic of the EMT JPA-66 innards

http://audio16.wordpress.com/tag/emt-jpa-66/

It seems there are using Takamisawa A12W-K relays for switching
(also I guess the signal: the relays below SUT's seem the same)

Golden contacts--ok, 50mR but at 1A, ...ok but not imressive. No ida if they use a latching or non-latching version.
jarek
Posts: 62
Joined: Wed Feb 02, 2005 10:02 am

Post by jarek »

Continuing my search, I came across TKD 2R6A switch:

http://www.tkd-corp.com/pdf/p05_2r6a.pdf

Solid silver, less than 5mOhm resistance (for comparison Hg-wetted relays are about 50mOhm), fully enclosed...not bad!
...and whooping 200Eu + shipping/pcs :O
Which actually given the price of Hg-wetted relays
(the cheapest I've found surplus is $25/pc, the switch has 6 positions, 6x25=...)
and the pain to implement them (separate supply, complicated sequencing for
latching types, upright position, etc..) is not bad to say least.

The main question is if this switch is any good? Anyone any experience?
I'm wondering at what current is the specified resistance. If at 1A it's of no use.
Obviously the mere resistance does not tell the whole story, but may be an indication
of the contact quality. I came across TKD spying on OmniGone rocket radar amp,
imitating a phono pre :

http://www.whatsbestforum.com/showthrea ... Phonostage

But I don't know those Bavarians. Actually one of them seems to use a not-so-impressive NSF switch for switching his multi-$$$$ sources:

http://audio16.wordpress.com/category/vinyl/

(scroll down to the middle of the page)
jarek
Posts: 62
Joined: Wed Feb 02, 2005 10:02 am

Post by jarek »

Finally, after some crawling through the hughe Blowtoch thread on diyaudio.com:

http://www.diyaudio.com/forums/solid-st ... -1570.html

I'll experiment with a big shallco switch from nebraska surplus:

http://www.surplussales.com/Switches/SWRotaryAll-1.html
Post Reply