Bill,
Switching has to be done with great care to prevent loud clicks in your speakers or even potentially damaging Carts or Preamps.
Preamp inputs have to be short circuited before switching the input lines.
However when using an Aurak type of configuration, when inputs are short circuited, gain and thus noise will massively increase.
That is why you should also circuit the outputs of your preamps before switching.
Leave enough time for settling the relay contacts.
Procedure should be like:
1) Short circuit the outputs,
2) after 5 msec short circuit the inputs,
3) after 10 msec switch the input lines,
4) after 15 msec release the input short circuit,
5) after 20 msec release the output short circuit.
Most miniature DPDT relays with gold plated contacts will do the job like the IM relay series from TE Connectivity.
Hans
Switching has to be done with great care to prevent loud clicks in your speakers or even potentially damaging Carts or Preamps.
Preamp inputs have to be short circuited before switching the input lines.
However when using an Aurak type of configuration, when inputs are short circuited, gain and thus noise will massively increase.
That is why you should also circuit the outputs of your preamps before switching.
Leave enough time for settling the relay contacts.
Procedure should be like:
1) Short circuit the outputs,
2) after 5 msec short circuit the inputs,
3) after 10 msec switch the input lines,
4) after 15 msec release the input short circuit,
5) after 20 msec release the output short circuit.
Most miniature DPDT relays with gold plated contacts will do the job like the IM relay series from TE Connectivity.
Hans
When i try " dil 5k002 bv338" there are a lot of hits here in europe on google and ebay.
And Hans your right about swiching sounds in low signal circuits. Look at my schematic(post 14), that is why i have also a relais switch at the output of the phonopreamp.
Last edited:
Strange because I too am getting plenty of hits and Meder is mentioned in several of them:
2 Stuck MEDER DIL-5K002-BV338, 5V Metall-Relais (M3881) | eBay
2 Stuck MEDER DIL-5K002-BV338, 5V Metall-Relais (M3881)
Non English listings of course. I would probably go for eBay, but I wonder if there are enough to meet your needs.
I know, odd. Google is usually so desperate to return something!
Hans: Good advice. I have done a first pass on looking at the issues around switching inputs and what is needed. I have 3 points where I can and probably do need to mute and the added possibility of powering off whichever phono stage is not in use.
For safety I should consider having a 2 second auto mute on input change, but I view that as phase 2.
Hans: Good advice. I have done a first pass on looking at the issues around switching inputs and what is needed. I have 3 points where I can and probably do need to mute and the added possibility of powering off whichever phono stage is not in use.
For safety I should consider having a 2 second auto mute on input change, but I view that as phase 2.
Attachments
Mmm, "something" being the operative word. Apparently Google isn't very helpful and maybe why some people end up here with their Yet another basic question
PS, I got exactly the same result as you
Last edited:
Is live signal switching a requirement? If so then you need the elaborate switch scheme, logic control
Another option is to have a separate phono preamp for each TT and do the switching at a higher level. They are not very expensive to build
( The lsk489/LM4562 app is a good one) Go smt to save space.most phono pre amps have a MC flat gain stage before the MM gain stage with the RIAA and rumble filter if used. Jumpers/switches are used to select MM/MC cart.
Last edited:
The problem is not one preamp per TT its one preamp per cartridge type and the fact that I now have the possibility to swap arm wands on one of my turntables. Whilst it's unlikely I will be running MM/MC in the same session, if I am testing things I might well do. I could just stick a patch box in between the turntables but being able to just select TT then flick a switch for MM or MC would be a preferable user experience.
And yes the fact that I refuse to follow the norm of an MM stage with headamp before it for MC makes it difficult, but that's the way I want it to be
And yes the fact that I refuse to follow the norm of an MM stage with headamp before it for MC makes it difficult, but that's the way I want it to be
So you have a special pre-amp input for each cartridge/arm type then. switch these pre-amps at a higher signal level, you are the engineer of your system.
If you doubt the performance of your reed relay in your application, test it your self(proto-type) vs hearsay. I have some old Dunco reeds I can test to compare against your readings.
But if I do that then how do a change from MM to MC on a turntable without replugging the cable? I don't want to do that.
I may well do that. How many in series would you recommend before it reaches any sane definition of audible? Has to be at least half a veil or I might miss it
@Stocktrader: MM load is unlikely to be ever changed if my calculations are correct. I'm not a huge believer in MC loading once you have tamed any ultrasonics, which almost any resistor will do. But I do have a spread of coil impedances so will need something, but that's not a primary concern at the moment.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.