How about 18 VDC versus 17.3 VDC (.7 VDC forward bias across D1)? That does not sound right (so to speak). Check the polarity of D1 or temporarily remove it from the circuit. Verify that the voltage at C2 is the same as at R103/203. If the gates of the signal FETS are at 17 VDC then the B1 is apt to clip. Further the sources of the signal FETS must be near 17 VDC also? They should be near 9 VDC. Take a look at D1.
Hi,
sorry for the delay answering. You are correct I did connect the corner of the PCB straight to the ground of the 3 prong wall plug via the metal case. I have no noise issue at all.
Regards,
Eric
Thanks! This was exactly the problem, I just cut out the diode and I'm getting reasonable readings.
Floated shield ground point
I just read the Audio Component Grounding article on this site as well as a few other related articles. I could not find an explicit statement regarding "pseudo-balanced" cabling that is internal to the chassis.
I am building the B1 (and variants) in a metal chassis having an on-board regulated power supply. The chassis is earth grounded. The signal connections to the chassis mounted RCA jacks are by way of two conductor shielded wire. The RCA jacks are isolated from the chassis. The shield is not part of the signal return path and is floated at one end. The RCA jack casings will be connected to signal ground. In this case, is it proper to directly connect the cable shield to earth (chassis) ground and not to signal reference ground? Thank you for commenting.
I just read the Audio Component Grounding article on this site as well as a few other related articles. I could not find an explicit statement regarding "pseudo-balanced" cabling that is internal to the chassis.
I am building the B1 (and variants) in a metal chassis having an on-board regulated power supply. The chassis is earth grounded. The signal connections to the chassis mounted RCA jacks are by way of two conductor shielded wire. The RCA jacks are isolated from the chassis. The shield is not part of the signal return path and is floated at one end. The RCA jack casings will be connected to signal ground. In this case, is it proper to directly connect the cable shield to earth (chassis) ground and not to signal reference ground? Thank you for commenting.
My B1 boards and jfets dropped through the letter box yesterday. I assembled it today and have the following voltages:- across C1 19.1v; C2 9.2v at the output caps 9.2v and 1.3 and 0.7mv on the output rca's. Am I safe to plug it into my system? If I've missed these details in earlier posts I apologise.
It works!! Why am I always surprised when something works first time. I'm just listening to Joan Armatrading "Into the blues" WOW. Its brilliant such detail and dynamics; the bass is deeper and better defined than my TVC pre and so natural sounding. The only problem? is that it goes from nothing to loud in less than a quarter of a turn[25k linear pots]
try adding a 2k to 3k resistor across the pot output, i.e. wiper to ground.
This type of linear volume control was why they invented log law pots. the resistor attempts to change the linear law into an S shaped law and, might suit you better.
I am now looking into placing my plywood wonder into a case (ref post 2334).But first, I have two questions.
1) I would like to make a balanced version (that I know how) with RCA inputs and outputs. I guess you can say I like my cake and eat it to...! So how do I connect the RCA's on a balanced B-1 (using 2 PCB's)
2) I found a switch I like, with 24volts lighting. If I increase the input voltage from 18 to 24 volts to provide me with the necessary voltage, what will be the effect on the sound of my B-1? Did anyone tried?
1) I would like to make a balanced version (that I know how) with RCA inputs and outputs. I guess you can say I like my cake and eat it to...! So how do I connect the RCA's on a balanced B-1 (using 2 PCB's)
2) I found a switch I like, with 24volts lighting. If I increase the input voltage from 18 to 24 volts to provide me with the necessary voltage, what will be the effect on the sound of my B-1? Did anyone tried?
As for #2, Mr. Pass has already said that the unit can handle considerably higher voltages. 24 VDC should be fine.
Personally I would keep it under 30VDC.
I am running mine with 22VDC and its perfectly fine. I also tried 24VDC and didn't notice any difference.
I would also like to build a balanced version with XLR connectors. Can someone share some information?
I would also like to build a balanced version with XLR connectors. Can someone share some information?
do not confuse yourself or other users by taking balanced inputs/outputs through RCA sockets/plugs.
Use a balanced connector like the 3pole XLR.
You can combine an unbalanced output though a parallel RCA connection, but you MUST use one or the other NOT both at the same time. Unless you build 3 outputs stages, two for balanced and one for unbalanced.
I tried a 2k74 resistor between wiper and ground on my 25k linear pot; it made a small difference in the range of movement but not a lot. Could I use a 100k log pot or is this too high;seem to think this has been mentioned before but can't find it. This might be a stupid question but would placing a 100k resistor across the the outer pins turn it into a 50k pot?
Thank you very much Andrew for the explanation, sounds clear to me. There will be 2 boards, two board channels per XLR plugs with paralleling RCA. Only to use XLR or RCA. I might post a little drawing to confirm I do not do anything ''stupid''.
Eric
Thank you very much Andrew for the explanation, sounds clear to me. There will be 2 boards, two board channels per XLR plugs with paralleling RCA. Only to use XLR or RCA. I might post a little drawing to confirm I do not do anything ''stupid''.
Eric
As Andrew thought might happen, I am thoroughly confused with your plan for RCA balanced circuitry. To get a handle on what your are up against you might benefit from reading NPs articles on DIY Op Amps and the line stage amp for the Zen. I am currently working on a way to use depletion devices in a modified long tailed pair that allows for DC coupling and source follower outputs. I doubt that I will succeed considering that I can't find where anyone has done this and there have been nearly a 100 years for someone to try.
Fair enough, I will try to draw a plan and post it. By reading previous posts, I though it was ''relatively'' simple...not shore anymore
