Fear as noise. Well, if you think what kind of confusion and disaster it may bring...Kinda of a bad transmission of critical war news.
I am not very experienced with relays. Usually i try to avoid them.
I will get a Tent Labs volume control that uses relays and Dale resistors because i build a preamp for a friend that wants remote control. I will compare it to my PSG preamp that is currently in the system of my friend. He is very happy with the result and will report if he hears any degration when he gets the relay controled preamp. He has an excellent system and a very good room. He has over 20 years experience with high end and i can trust him.
On another issue i build the Low Z Fet MPP. It worked right away. Bias at the input can be adjusted to a very low level and it is very stable. It should be because Fets are constant current sources. I had some trouble to adjust Bias to zerro at the input and also at the output the same time so i used a coupling cap to test it.
I think i have a solution for that and will try that out tomorrow.
I will get a Tent Labs volume control that uses relays and Dale resistors because i build a preamp for a friend that wants remote control. I will compare it to my PSG preamp that is currently in the system of my friend. He is very happy with the result and will report if he hears any degration when he gets the relay controled preamp. He has an excellent system and a very good room. He has over 20 years experience with high end and i can trust him.
On another issue i build the Low Z Fet MPP. It worked right away. Bias at the input can be adjusted to a very low level and it is very stable. It should be because Fets are constant current sources. I had some trouble to adjust Bias to zerro at the input and also at the output the same time so i used a coupling cap to test it.
I think i have a solution for that and will try that out tomorrow.
we're always awake in the early (night) hours 
Joachim, I understand that you don't like relays, however, I have specific need for a relay. as the project that I am working on demands some sort of relay. However, IF I put my opinion on mercury wetted relays on another thread, it probably would not have appeared. Thanks for letting me put it here. Now, back to more interesting things.
i like the convenience of Relays very much but so far i did not find the time to test different types. I have an engineer friend in Vienna that has a lot of experience with relays. Maybe i find the time to ask him, I remember he told me that there are relays that are optimised for the uA range so they should have good resolution with tiny signals.
i build a new High Z MPP and have it currently plaing with the Inductive RIAA.
I made some improvments that lowered distortion and offset much.
I will constantly use it so i used good parts.
The reason for this is, that i wanted to try different load resistors.
i began to compare 47kOhm Tantal to 1Kohm Tantal.
In my system 47kOhm does not work.
For example on Hellen Merill in Tokio, her voice was too spitty for my taste. Silbiants where clearly more standing out then a natural voice has.
The 1kOhm did much better. I then substituted the Tantal with a Texas Components naked Z Foil and the sound got more detailed but it just was not right still.
Then i tried to load down. Brianco had send me 300 Ohm Dale noninductive military wirewounds and they fittet absolutely well. The sound got much more robust and dynamic and i could listen very loud without fatique. So at least in the context of my system the expensive Z Foil was not as good performing then the old Dale.
The Dale even had magnetic endcaps, so i concluded that resistor value is more important then type. I now will try to get some 300 Ohm Z Foil to try if that is an improvement.
I also will try 138 Ohm, the value that Davis Wilson is using with the Lyra Olympos.
I have an Olympos too, so when i find the time i can try that too. Usually i do not like to swap cartridge too often because you never know if you hit the sweetspot. The Titan i that i am using performes admirably so i am a bit reluctant to try the Olympos.
Maybe i wait until Martina Schöner is showing up the next time.
She really enjoys cartridge setup so i could leave it to her.
Tomorrow i will try 100 Ohm. I have a pair of YAM2 ready for that.
I made some improvments that lowered distortion and offset much.
I will constantly use it so i used good parts.
The reason for this is, that i wanted to try different load resistors.
i began to compare 47kOhm Tantal to 1Kohm Tantal.
In my system 47kOhm does not work.
For example on Hellen Merill in Tokio, her voice was too spitty for my taste. Silbiants where clearly more standing out then a natural voice has.
The 1kOhm did much better. I then substituted the Tantal with a Texas Components naked Z Foil and the sound got more detailed but it just was not right still.
Then i tried to load down. Brianco had send me 300 Ohm Dale noninductive military wirewounds and they fittet absolutely well. The sound got much more robust and dynamic and i could listen very loud without fatique. So at least in the context of my system the expensive Z Foil was not as good performing then the old Dale.
The Dale even had magnetic endcaps, so i concluded that resistor value is more important then type. I now will try to get some 300 Ohm Z Foil to try if that is an improvement.
I also will try 138 Ohm, the value that Davis Wilson is using with the Lyra Olympos.
I have an Olympos too, so when i find the time i can try that too. Usually i do not like to swap cartridge too often because you never know if you hit the sweetspot. The Titan i that i am using performes admirably so i am a bit reluctant to try the Olympos.
Maybe i wait until Martina Schöner is showing up the next time.
She really enjoys cartridge setup so i could leave it to her.
Tomorrow i will try 100 Ohm. I have a pair of YAM2 ready for that.
Yes, I noticed that many relays have a spec on *minimum* current through the contacts. Has to do something whith what they cal punch-through IIRC, for the signal to get through the surface (oxide?) layer on the contacts.
Then there are small-signal relays that are specifically designed for very low signal currents. As I understand, there is still the need for a minimum current but it is extremely small. Anybody has more info on this?
jd
Here is the circuit i curently use. On first look it is not much different but it is optimised in many ways. First i raised the gain in the input stage and lowered the gain in the output stage. I raised the base resistors in the cascodes to 470 Ohm. I trimmed the input stage with the 20 Ohm trimmer. To make the low Z Fet version work i needed that trimmer to make the input offset low. I whould not recomment that version for DIY because a lot of nasty things can happen when the powersupply voltages are not stable or when only one voltage is working. That can happen on switch on or when you use batteries that can have different fill.
After having adjusted the 20 Ohm pot for lowest DC offset at the input i wired back into High Z and could not beleave my ears. That circuit now sounds as good as the Discreet INA, so low is the distortion. I was really stupid using 10 Ohm fixed resisrtors here all the time.
I connected the "new" High Z Fet MPP to the inductive RIAA. I am now using the coil that Sowter made for me. Hum is not existing with this coil, even with the coil in open air without earth connection. This MU meatal case is very effective. It should be because 100´s of transformers and inductors are used in professional mixing boards without hum problems.
I could bring the offset from the High Z MPP down to + - 5mV. This is still too high for the inductive RIAA because i have to use a 100kOhm resistor after the servo. A lower value whould have an effect on the frequency response of that stage. So i am using an output cap.
I have an idea to stabilise the offset even further and will post it later.
After having adjusted the 20 Ohm pot for lowest DC offset at the input i wired back into High Z and could not beleave my ears. That circuit now sounds as good as the Discreet INA, so low is the distortion. I was really stupid using 10 Ohm fixed resisrtors here all the time.
I connected the "new" High Z Fet MPP to the inductive RIAA. I am now using the coil that Sowter made for me. Hum is not existing with this coil, even with the coil in open air without earth connection. This MU meatal case is very effective. It should be because 100´s of transformers and inductors are used in professional mixing boards without hum problems.
I could bring the offset from the High Z MPP down to + - 5mV. This is still too high for the inductive RIAA because i have to use a 100kOhm resistor after the servo. A lower value whould have an effect on the frequency response of that stage. So i am using an output cap.
I have an idea to stabilise the offset even further and will post it later.