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Usually 9V battery is used. How big res should I use with 22v?
I used a 9v battery and a 1K resistor. Here's a link to a very good build guide by washuliu, if you scroll down you will find the section on LED measurement.
DC-Coupled B1 Buffer Build
DC-Coupled B1 Buffer Build
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Usually 9V battery is used. How big res should I use with 22v?
You could do the math, failing that try 8-10K and see what happens
In post 2004 Salas advised to use 10-50 Ohm.
But it is for the 2x2 at the B1 section.
For the leds I guess I have to use bigger resistor as the leds equal roughly 600-800 Ohm. Or 1k. Not sure. Can't remember the simulation.
Or I don't even have to match the leds jfets, but I can change their voltage if needed via the jfet changing.
But it is for the 2x2 at the B1 section.
For the leds I guess I have to use bigger resistor as the leds equal roughly 600-800 Ohm. Or 1k. Not sure. Can't remember the simulation.
Or I don't even have to match the leds jfets, but I can change their voltage if needed via the jfet changing.
Not sure what to say to that post, except maybe
My advice is buy a board and 4 matched JFETS from tea-bag. You can also get matched JFETS from Chinese ebay sellers but I cant vouch for quality or how close a match they will be.
Get LED's from mouser, they are pretty well matched. Check with a 9v battery and 1K resistor.
My advice is buy a board and 4 matched JFETS from tea-bag. You can also get matched JFETS from Chinese ebay sellers but I cant vouch for quality or how close a match they will be.
Get LED's from mouser, they are pretty well matched. Check with a 9v battery and 1K resistor.
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The minus mVdc offset (with reference to Signal Ground) tells you that both channels have the follower jFET biased to less than Idss.
The very low mVdc offset tells you that the bias is only very slightly less than Idss.
Both of these are good.
With your mains power Chassis connected, you have complied with the Safety requirement.
You do not need a Chassis to Audio connection unless you have exposed conductive parts.
In most preamps and buffers the only exposed metal is generally the phono ground barrels. These are covered when the pre is connected with cables to the Source and Receiver.
As long as the Source and Receiver are Safely built then you and other users are safe.
This has a bearing on the Power Amplifier input.
Here you often see and I happen to recommend a resistor between Signal Ground and Power Pround. This resistor MUST have a bypass of two inverse parallel power diodes to conduct a Fault Current from Source through to the Power Amp PE protection. This is VERY important.
BUT !!!!!
things change when the cables are disconnected.
A child sucking on the end of a disconnected interconnect is potentially exposed to danger !!!!!!!
Do you design for that extreme condition?
The Signal Ground is part of a separate circuit from the Power supply circuit and from the speaker output circuit.
All these circuits must reference each other. But they should NEVER share a common trace/wire. That means a POINT connection at the Main Audio Ground (MAG).
Another BUT !!
In a multichannel amplifier the different channels connect to the Main Audio Ground. If you have two Speaker circuits and/or two Signal circuits and/or two Power circuits connected to the same MAG, then you must have loops. Those loops create aerials, that are effective transmitters and receivers of interference.
Separate the Signal Ground from the Power Ground to REDUCE the interference current in the Signal circuit.
Yet another but !!
That resistor blocks Fault Current, if there is a catastrophic failure in the mains power to earlier equipment.
The only way I know to short that Fault Current to PE is to provide a high current bypass around the interference reducing resistor.
Does that answer your question?
All these circuits must reference each other. But they should NEVER share a common trace/wire. That means a POINT connection at the Main Audio Ground (MAG).
Another BUT !!
In a multichannel amplifier the different channels connect to the Main Audio Ground. If you have two Speaker circuits and/or two Signal circuits and/or two Power circuits connected to the same MAG, then you must have loops. Those loops create aerials, that are effective transmitters and receivers of interference.
Separate the Signal Ground from the Power Ground to REDUCE the interference current in the Signal circuit.
Yet another but !!
That resistor blocks Fault Current, if there is a catastrophic failure in the mains power to earlier equipment.
The only way I know to short that Fault Current to PE is to provide a high current bypass around the interference reducing resistor.
Does that answer your question?
Maybe. Since this is an often occuring problem for me I have been thinking of the reasons and solutions some times.
As far as I understand it, one way to break a loop is to slightly elevate one plane to the other, usually safety/chassi ground to signal ground. This can be done with power diodes/bridges.
A resistor, as far as I grasp it, REDUCES the chassies ability to be an antenna to the signal ground.
But in a combination with the two, adding a resistor to dual diodes that has already broken the loop is addning eventual antenna noice to the signal ground more then reducing it. Here is where I might be wrong in my reasoning. I am not clear about this so further enlightenment is welcome.
Another thing. When doing the same thing to the two devises, lifting pre and poweramp audio ground planes with diodes for example. Then one will have both devises at same audioground again, with a possibility to loop problems between channels. No?
Hi Andrew, I did not design for the eventuality of a child sucking on the end of an interconnect. Our child is a 27 year currently serving overseas and rarely at home so it's not very lightly to happen, but I see your point.
The resistor and diode bypass is a good idea. Currently my chip amp boards are grounded to the chassis star earth but the phono sockets only connect through the boards return in the usual way.
What values of resistor and diode would be sufficient to safely ground the phono socket barrels to chassis earth? I am about to build mono block versions of the My Ref FE and would like to include this feature in the build.
The resistor and diode bypass is a good idea. Currently my chip amp boards are grounded to the chassis star earth but the phono sockets only connect through the boards return in the usual way.
What values of resistor and diode would be sufficient to safely ground the phono socket barrels to chassis earth? I am about to build mono block versions of the My Ref FE and would like to include this feature in the build.
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I do not think that using the term "ground lift" helps with understanding what is happening.
I think in routes that the current must flow.
If there is a circular route that includes a loop area, then that loop is susceptible to an interference current flowing around the loop.
more particularly your
is quite misleading.
The loop area is always an aerial. Adding a resistor does not change that.
The added resistor changes the current flowing around the loop. That reduced current results in reduced voltage drops on all the other resistances in the loop. One or more of those traces will be an "input" to a circuit. Reducing the current and thus the voltage reduces the level of interference being applied to the "input" that is affected by current passing through that part of the loop.
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I have just replaced my custom switch + dale resistors attenuator with two precision 10 turn wirewound pots from vishay/spectrol.
First impressions are very positive. I will leave it to break in for a few days and report back.
And to prevent the usual linear vs log discussion, it is not an issue because of the 10 turns. The useful levels for me are included in the first two turns with quite a huge margin for precision adjustment.
I just have to find a way and bind the two together because it is a bit tricky to get nice a nice center manually. For now I use my mono record Sax Colossus with nice results, but I intent on using some gears and make the pots rotate together. Linearity is pretty nice at 0,25% so them moving together is guaranteed pretty much.
First impressions are very positive. I will leave it to break in for a few days and report back.
And to prevent the usual linear vs log discussion, it is not an issue because of the 10 turns. The useful levels for me are included in the first two turns with quite a huge margin for precision adjustment.
I just have to find a way and bind the two together because it is a bit tricky to get nice a nice center manually. For now I use my mono record Sax Colossus with nice results, but I intent on using some gears and make the pots rotate together. Linearity is pretty nice at 0,25% so them moving together is guaranteed pretty much.
I am dubious about a lot of the claims people make about hifi, but after a week of using the DCB1 every day, it has definitely improved a bit. I wondered about the claims of 'amazing bass' at first. On the first day, I could not see any real improvement in that area but it did sound good elsewhere. A week on and yup the bass is now very good indeed. There must be something in the theory of 'burn in' this is more than just my brain adjusting to it. I don't think it will improve much more now but it is a very impressive bit of kit IMO.
Hi all, just completed my dcb1 and everything seemed fine until I hooked up the output connector. Voltage readings are very good 10.36 and -10.42 and offset readings are 2.4/1.5mV. All leds light normally. Hooked up I/O connectors and fuse blew. I notice that there is continuity between left, right, and ground terminals on output. Has anyone experienced this? The relay clicks normally but I wonder if it is damaged. There doesn't seem to be excessive heat anywhere.
Components seem to be installed correctly and there appear to be no solder bridges. My rca connectors are isolated from chassis and installed correctly. I will try to post photos shortly. I would appreciate your advice. Thanks so much.
Components seem to be installed correctly and there appear to be no solder bridges. My rca connectors are isolated from chassis and installed correctly. I will try to post photos shortly. I would appreciate your advice. Thanks so much.