Have gottten a specific wish from a friend.
How can one possibly and most simple make an input-select of 3 sources hum-free on the Pearl-3 ?
Suggestions appreciated.
How can one possibly and most simple make an input-select of 3 sources hum-free on the Pearl-3 ?
Suggestions appreciated.
Hello!
Do you mean having 3 turntables to be connected to a single phono RIAA pre-amp?
One solution is to use 3 x 2-pole relays and create a logic to turn each relay on at a time.
This way you don't have to run phono cables to switch in the front panel.
You will use a switch in the front panel and it will only send a DC voltage to the relays located as close as possible to the rear connectors and pre-amp input.
If you want to sofisticate a bit more, in order to eliminate any spikes during switching, you may add a fourth relay to ground pre-amp input while the switching is being performed. You'll need to create a logic for that.
Do you mean having 3 turntables to be connected to a single phono RIAA pre-amp?
One solution is to use 3 x 2-pole relays and create a logic to turn each relay on at a time.
This way you don't have to run phono cables to switch in the front panel.
You will use a switch in the front panel and it will only send a DC voltage to the relays located as close as possible to the rear connectors and pre-amp input.
If you want to sofisticate a bit more, in order to eliminate any spikes during switching, you may add a fourth relay to ground pre-amp input while the switching is being performed. You'll need to create a logic for that.
Reed relays are probably not the best choice here. But you can try them.
Normally what you really want to use are higher quality telecom relays, dual contact in a sealed enclosure. You can get them fairly cheaply, and of course they make better ones. Given the quality of this preamp you might want to aim a little higher.
Normally what you really want to use are higher quality telecom relays, dual contact in a sealed enclosure. You can get them fairly cheaply, and of course they make better ones. Given the quality of this preamp you might want to aim a little higher.
OK...... I read the spec´s on these.... supposed to have lower than 50mOhm on resistance, but maybe
I was looking at the wrong parameters. I have a bunch of now obsolete Panasonic signal relays with palladium contacts,
but these are reserved for the Super X-Ono clone as seen here
https://www.analog-forum.de/wbboard/index.php?thread/110893-sxono/&pageNo=1
I was looking at the wrong parameters. I have a bunch of now obsolete Panasonic signal relays with palladium contacts,
but these are reserved for the Super X-Ono clone as seen here
https://www.analog-forum.de/wbboard/index.php?thread/110893-sxono/&pageNo=1
Hi Boydk,
As you know, reviews don't say much, a schematic points to a possible great design. Board layout and chassis / wiring / power supply determine the rest - assuming decent parts of course. But we are only concerned with the preamp in this thread to be honest. The Pearl three.
Contact resistance alone isn't the only factor unless you are just switching DC control signals. There is pick up of impulse from the coil, and the fact that the contacts are magnetic material (or they wouldn't work). That can induce distortion. Reed relays were used when you wanted a quiet contact closure, or very low mass (aircraft / missile electronics for example). I have a ton of them I can't use for audio. They were expensive, but unsuited for the task, I learned afterwards. The related device is a reed switch seen in alarm contacts with a magnet on a door, tape motion sensors and similar applications.
You are dealing with extremely low amplitude signals. Don't think of the maximum output of the phono cartridge, look at the tiny signals. You know, where the detail is.
The purest would use three phono preamps since each cartridge has a capacitive loading preference, or resistive load and switch between their outputs. The connecting phono cables may have varying capacitance, and you want to compensate for that too. Most tonearm wiring used fall within a close range unless someone decided to get fancy. You could compensate each input individually for each cartridge load requirements. Nothing wrong with doing it that way.
The real message is to use a good quality relay designed for switching audio frequencies (as opposed to RF).
As you know, reviews don't say much, a schematic points to a possible great design. Board layout and chassis / wiring / power supply determine the rest - assuming decent parts of course. But we are only concerned with the preamp in this thread to be honest. The Pearl three.
Contact resistance alone isn't the only factor unless you are just switching DC control signals. There is pick up of impulse from the coil, and the fact that the contacts are magnetic material (or they wouldn't work). That can induce distortion. Reed relays were used when you wanted a quiet contact closure, or very low mass (aircraft / missile electronics for example). I have a ton of them I can't use for audio. They were expensive, but unsuited for the task, I learned afterwards. The related device is a reed switch seen in alarm contacts with a magnet on a door, tape motion sensors and similar applications.
You are dealing with extremely low amplitude signals. Don't think of the maximum output of the phono cartridge, look at the tiny signals. You know, where the detail is.
The purest would use three phono preamps since each cartridge has a capacitive loading preference, or resistive load and switch between their outputs. The connecting phono cables may have varying capacitance, and you want to compensate for that too. Most tonearm wiring used fall within a close range unless someone decided to get fancy. You could compensate each input individually for each cartridge load requirements. Nothing wrong with doing it that way.
The real message is to use a good quality relay designed for switching audio frequencies (as opposed to RF).
Hi,
There are some, but normally they are designed more for line selector, which is not much susceptible to noise as phono is.
If you search for "audio selector", "3 channel audio selector relay" etc, you'll find some options. You may try.
Main issue is size, position of connectors etc. For your selector, dimension of pcb tracks, position of conectors and relays will make all the difference in achieving your goal, which is not so straightforward due to the phono small signal. Everything should be as small and close as possible.
In addition, DC signal must be totally free from any ripple.
Also DC signal should not switch too fast in order to minimize interference (you can control with RC filter). Since this is not a power switching, it doesn't matter if the contacts move slower to open or close. You should also use RC and diode in parallel with the relay coils to minimize spikes.
Once upon a time I build a phono selector board. Controlled by arduino.
It has three inputs and impedance adjust.
https://www.diyaudio.com/community/threads/sound-comfort-mc-mm-phono-preamp.297718/
It has three inputs and impedance adjust.
https://www.diyaudio.com/community/threads/sound-comfort-mc-mm-phono-preamp.297718/
Hi Boydk,
With so many products NLA, I never bothered to pick "the one relay". Basically, just use something specified for telecom, sealed. It will probably be a DIP in DPDT configuration. Reputable manufacturer, not "economy". You'll be fine.
You don't have to worry about high frequencies, leakage currents or many other aspects that would force you to a special relay. I generally go for the more sensitive ones (within reason), just to cut down on switched current. This is more about common sense than chasing imagined perfection. The application is low signal level, so you need a good part. It doesn't need to be a military qualified part. You also aren't worried about RF matching and isolation.
Those shown above are more expensive shielded models. You don't need that, it wouldn't do any damage but it doesn't buy you anything in your application unless you have electrical noise nearby. Then I would suggest you solve those things at the source.
With so many products NLA, I never bothered to pick "the one relay". Basically, just use something specified for telecom, sealed. It will probably be a DIP in DPDT configuration. Reputable manufacturer, not "economy". You'll be fine.
You don't have to worry about high frequencies, leakage currents or many other aspects that would force you to a special relay. I generally go for the more sensitive ones (within reason), just to cut down on switched current. This is more about common sense than chasing imagined perfection. The application is low signal level, so you need a good part. It doesn't need to be a military qualified part. You also aren't worried about RF matching and isolation.
Those shown above are more expensive shielded models. You don't need that, it wouldn't do any damage but it doesn't buy you anything in your application unless you have electrical noise nearby. Then I would suggest you solve those things at the source.
Fwiw years ago i went through a few sessions comparing relays. The mercury Clare had a rather peculiar, easily distinguished sound.
Hi analog_sa,
Not surprisingly since you have a film of mercury. I have some as well, but I don't think they are intended for low level signal. Super reliable contacts, expensive as sin.
Hi Monstercore,
Those seem unusually cheap, unless they were surplus.
Not surprisingly since you have a film of mercury. I have some as well, but I don't think they are intended for low level signal. Super reliable contacts, expensive as sin.
Hi Monstercore,
Those seem unusually cheap, unless they were surplus.
Thanks for all your suggestions. I´ll have a look around.... for either some kind of "telecom"-relays or Panasonic small signal relays...
sealed off course.
About 10 years ago they were sold in batches of 50 or 100 pieces. And they sound like nothing as it should be.
Build a lot of input selectors and stepped volume controls with it. No problems and low current( 1mA).
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Hi Monstercore,
These seem unusually cheap, even in those lot quantities. They might be great, but sound as if they were surplus. Nothing wrong with surplus, except you normally can't buy more.
These seem unusually cheap, even in those lot quantities. They might be great, but sound as if they were surplus. Nothing wrong with surplus, except you normally can't buy more.
Yes, they were surplus. Now only two sellers left. For 3 euro a piece.
https://shop.tvsat.com.pl/en_GB/p/2pcs-DIL5K002-BV338-Reed-Relay-5VDC-1A-THT-MEDER/28810
https://www.ebay.com/itm/393601715411
https://www.ebay.de/itm/2-Stuck-MED...romechanische_Bauelemente&hash=item415caaa726
https://shop.tvsat.com.pl/en_GB/p/2pcs-DIL5K002-BV338-Reed-Relay-5VDC-1A-THT-MEDER/28810
https://www.ebay.com/itm/393601715411
https://www.ebay.de/itm/2-Stuck-MED...romechanische_Bauelemente&hash=item415caaa726
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