@Vincent77 - Thanks for the tip about relays, In the linked thread you mention the "The latching Ag-Pd contact relays", I'm trying to source these parts & read up on how to use them. Can you tell exactly which ones you used, and any tips of how/why to use these relays.
I use a 48 stepped shunt attenuator, and currently like using a manual clicky rotary switch for the volume control.
I do like your idea of using 'audio latching relays' instead of the 'standard' Seiden 2pole 4port manual switch typically used for source 7 output selection. It opens up a lot of useful opportunities to improve the functions of the 'standard' control amp designs.
I am trying to control output selection to different tube amplifiers, but would LOVE to be able to use 'audio latching relays' to switch output to amplifiers & speakers to the selected amp, but also leave the 'un-selected' tube amplifiers protected from 'not being connected to a load'.
Any advice you could offer me, to get me started, please?
Are you sure? Relays are used most 'high-end' audio preamps and in other equipment that requires much more accuracy than audio.
That's called a latching relay. I have used these in input selectors and relay attenuators.
Hi, any opinions on devices like the 74HC4052 and the like? I came across that option through reading a review of mid-class audio equipment (cant remember what it was, but possibly in the low 4-digit $ range).
Due to lack of equipment I don't have any THD or other measurements.
Thanks & cheers, Kai
Due to lack of equipment I don't have any THD or other measurements.
Thanks & cheers, Kai
Pretty much like any multiplexer but this one has worse specs than say the ADG1414. Look at On resistance and isolation.
Yes, those figures raised my eyebrows a bit as well. Maybe need a buffer in front of them, but I might also have a look at the ADG....74HCs are a charm to source, though
- thanks!
Anyone have any real experience using ADGxxx? I'm curious, if you look at the ADG1414 datasheet there is a graph for off isolation. I've attached a pic. It shows an off isolation of around -90dB for some frequencies between 1-10k Hz. Does that mean you might hear signal from a source when it's not selected? Even if quietly?
Attachments
Yes, youre right. I built a simple breadboard 2 device switch with the adg1414. If i deselect all inputs (all registers 0), i can still hear a signal if i ramp up the amp. Its very very low volume, but its there.
Any advice how to get rid of that signal ? This will make the adg obsolete for my purposes.
Yes, the distortion in the lower freq was massive. Perhaps i will be more lucky with the latching relays. My relays, that i used for the experiments were rather cheap, normal relays. Perhaps the magnetic field made the signal get distorted.
Will try the latching relays.
There are also rather cheap relays, called signal relays on farnell. Did simeone try them ?
Hmmm, IMO that's not really a usable solution then!
Strange. I think you either had a poor implementation, low quality relays or some other issue. Even if using non-latching relays there should be no distortion. Some ones I have tried that have worked great:
Omron G6K
AXICOM IM
Panasonic GQ
In each range there are many different types (latching or not), voltages etc.
Mooly has this FET based input selector, I was unable to find the required FET though. But he mentioned that it did its job very well. Maybe he could give some advice here. The selector uses 2 FETs to output the signal, basically one pulling the channel to ground, another one to pass it through.
I had problems to source the relays you mentioned. Simply because i wanted to try relays as fast as possible. So i bought some panasonic ds2e-s. After sime quick and dirty breadboarding i know, that you were right. My former relays were just too low quality. The ds2e relays sound pretty nice. I cant measure any real distrortions and they are really quiet if i turn them off. I could only buy the nonlatching type at my local store, but they are so nice, that i think i will stay with them.
The next days its party in germany, so i wont be able to make any progress, i think i will continue on we next week.
Will make some photos then and some measurements.
I would like to hear your oppinions on switching gnd or not. What do you think ?
Thanks for the help of all contributors, youre the best. I am a computer science guy and audio is only a hobby, so with every sentence i learn more and more, i hope i can give something back ( microcontrollers, fpgas and programing are my theritories).
Yes, i am also gonna try the FET kund of switching. First i came back to relays, because i already came from this direction and wanted to know, what i did wrong
.I did not try them, but i thought they would behave comparable to the 4016 series, which i tried and was dissappointed. The 4097 also has a max ron of 1050ohm, so i skipped it. I will try, if i get one into my hands. They would be a lowcost version of the switch, lets see how they measure.
LDRs? Perhaps wrong thread or are you suggesting that we use them for an input selector?
I don't bother and haven't had any problems. Others might have a different opinion though I guess.
The 74HC4052 is a bit old and maybe there is better out there, but that said, the 74HC4052 is used in the Ayre K-5xeMP line preamplifier for both input selection and volume control. So clearly solid state switches can be used for very high end audio applications, but as with all parts some design considerations have to be taken into account:
1) The signal voltage has to stay within the limits of the ic, which is usually the rails of the ic. Don't try to pass signals that swing past the rails there are protection diodes in the package.
2) The current through the switching element has to be very small, like driving the gate of a jfet. The resistance is nonlinear so will cause distortion if you try to drive something like a 10k load.
3) The off isolation is not that good (like -50dB) so if you want more isolation you will need to use a "T" switch configuration.
4) The solid state switch needs clean rails just like any other audio circuit, else the noise from the rail may get imposed on the signal.
Leve
Yes, I thought that I saw the 74HC4052 in a HiFi review mentioned, maybe it was even the Ayre, if not then something similar - that gave me the idea to use the 4052 in the first place. I cant remember the exact reason anymore, but I also read somewhere the advice to use the HC, not the HCT.
Anyway, thanks & I agree on your points, esp for 2) I have an OPA2134-based buffer planned behind the selector...or maybe a B1.
Thanks, Kai
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