I have confused myself again.
The case I am using for my B1 buffer is metal. The RCA jacks I will be using have insulating collars so the ground on the jack is not in electrical contact with the case and cause a possible ground loop. So far so good.
Should the stand offs holding the PCB be plastic or metal? My confusion is that the screw holes on each corner not electrically isolated from the ground on the PCB. This seems deliberate. However, if I use metal stand offs, wouldn't this create 4 different length paths to ground and create a possibility for a ground loop. Or are the differences too small and I am simply over-thinking this one?
The case I am using for my B1 buffer is metal. The RCA jacks I will be using have insulating collars so the ground on the jack is not in electrical contact with the case and cause a possible ground loop. So far so good.
Should the stand offs holding the PCB be plastic or metal? My confusion is that the screw holes on each corner not electrically isolated from the ground on the PCB. This seems deliberate. However, if I use metal stand offs, wouldn't this create 4 different length paths to ground and create a possibility for a ground loop. Or are the differences too small and I am simply over-thinking this one?
The PCB mount holes are connected to ground? (Looks at photos of PCB...)
Huh. Yes, they are.
Use nylon screws and nuts except in one corner.
Huh. Yes, they are.
Use nylon screws and nuts except in one corner.
The barrel of the RCA/Phono socket is not ground. The RCA/Phono is a signal connector and carries the Flow/Hot signal as well as the Return/Cold signal. Both the wires coming into the connector are signal wires. Both the wires leaving the connector are signal wires.
I would keep the audio ground separate from the chassis. The chassis is not required for good and correct audio performance.
The chassis has three purposes:
a.) it carries the circuits and protects them from damage.
b.) it encloses the circuits and if made of metal can screen it from interference.
c.) if mains powered it can be connected to Protective Earth for the Safety of users.
I was using standard lingo and I do appreciate the difference between "ground" and "return". Specifically, are you suggesting that I
1) use plastic stand-offs when mounting the PCBs in a metal chassis
2) keep the insulated RCA input jacks
3) Only connect the "ground" from the wall wart to the PCB "ground" but necessarily to the chassis?
I know that usually things are stricter on a chassis ground when one is using an "honest to goodness" power supply rather than a wall wart.
Any negatives if I were to use 12uf capacitors for C101 and C201? I happen to have good quality ones in this value.
Cheers,
David
Cheers,
David
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using one PCB ground plane to chassis connection is normal. But where the PCB has some interference being conducted to the PCB ground plane then a lowering of the ground plane to chassis impedance allows the interference to pass to the chassis more easily. this would be facilitated by using multiple ground plane to chassis metal mountings.
keep the RCA barrels insulated from the Chassis. the two input wires must pass through the panel as a signal pair and not connect to chassis
Is the wall wart double insulated and carrying the double concentric square symbol? If so then the equipment fed with power can be considered as safe and isolated from the mains.
If it is not double insulated then the equipment needs a Protective Earth
Will PF5102's work?
Hope there is still help here. I am determined to build a B1 (planning for a point-to-point), but still have issues with finding Jfets here in dark Africa. I managed to get a few 2SK170’s, but from a suspect supplier. I have no idea if they are fake or real, and there does not seem to be an easy test for this. Measuring their Idss’s – they range from 13,50 to 17,06. I don’t want to risk using fakes – unless they sound the same as the originals – but then, how would I know?
The only Jfets I can get from a reputable supplier are BF862 or PF5102 from our local RS Components outlet (I get everything from them). The BF862’s seems to be a bit of a challenge to use – especially for a novice like me. So, I still have to see conclusive evidence that PF5102’s will work for the B1. Can anybody confirm this? And will it sound the same as 2SK170’s? Are there other alternatives I am missing?
Thanks,
Jerry
Hope there is still help here. I am determined to build a B1 (planning for a point-to-point), but still have issues with finding Jfets here in dark Africa. I managed to get a few 2SK170’s, but from a suspect supplier. I have no idea if they are fake or real, and there does not seem to be an easy test for this. Measuring their Idss’s – they range from 13,50 to 17,06. I don’t want to risk using fakes – unless they sound the same as the originals – but then, how would I know?
The only Jfets I can get from a reputable supplier are BF862 or PF5102 from our local RS Components outlet (I get everything from them). The BF862’s seems to be a bit of a challenge to use – especially for a novice like me. So, I still have to see conclusive evidence that PF5102’s will work for the B1. Can anybody confirm this? And will it sound the same as 2SK170’s? Are there other alternatives I am missing?
Thanks,
Jerry
2sk170BL have a maximum Idss of 12mA
Look up Borbely's 2part article on jFETs. It's posted in this Forum.
It shows how to test your jFETs for Idss and Vgsoff=Vpinchoff
That allows you to calculate the gm.
BF862 should be a safe bet. I have not seen any posts suggesting it has been faked yet.
LSK170b are suitable.
You can buy them from the Forum.
Look up Borbely's 2part article on jFETs. It's posted in this Forum.
It shows how to test your jFETs for Idss and Vgsoff=Vpinchoff
That allows you to calculate the gm.
BF862 should be a safe bet. I have not seen any posts suggesting it has been faked yet.
LSK170b are suitable.
You can buy them from the Forum.
Linear Systems LSK170 Ultra Low Noise Single N-Channel JFET (8 Pieces) – diyAudio Store
You want the B grade $33.
Hi Jerry,
As Andrew already mentioned, if your parts are marked as 2sk170BL and you
get 13+mA Idss then they are fake.
Should you decide to go with a PCB instead of p2p, you can get the PCB with
jfets for $40 + shipping from the Passdiy site:
https://www.passdiy.com/store
Cheers,
Dennis
As Andrew already mentioned, if your parts are marked as 2sk170BL and you
get 13+mA Idss then they are fake.
Should you decide to go with a PCB instead of p2p, you can get the PCB with
jfets for $40 + shipping from the Passdiy site:
https://www.passdiy.com/store
Cheers,
Dennis
Wow – much help indeed! Thank you Andrew, wdecho, ElFishi and Dennis for such prompt replies and pointing to good options/alternatives. It is certainly very encouraging for a newbie like me to know this thread is still so active and help is at hand.
I conclude therefore that PF5102’s are not an option. BF862’s are a good option if I stick with my local supplier. The best would be to get Jfets (and even PCB’s) from the Forum or Passdiy stores. This will cost me ($ and time) as our exchange rate makes it expensive to import from the states.
I hope to post my B1 build soon. The next project might be Amp Camp Amp, then Frugal Horns, then a Sub woofer, then …. Life is too short.
Until then.
I conclude therefore that PF5102’s are not an option. BF862’s are a good option if I stick with my local supplier. The best would be to get Jfets (and even PCB’s) from the Forum or Passdiy stores. This will cost me ($ and time) as our exchange rate makes it expensive to import from the states.
I hope to post my B1 build soon. The next project might be Amp Camp Amp, then Frugal Horns, then a Sub woofer, then …. Life is too short.
Until then.