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Balanced Zen Line Stage Preamp
Balanced Zen Line Stage Preamp
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Old 8th February 2019, 01:48 AM   #11
elwood625 is offline elwood625  United States
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The part I had trouble with is where the thermistor connects to 110v ground. One corner of the power supply PC board is the other connection to the thermistor, that corner needs to go to 110v ground. I ended up using a ringlet terminal in between the PC board and the board standoff, the wire was then connected to the chassis and the 110v ground terminal on the IEC.
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Old 8th February 2019, 02:50 AM   #12
jfuquay is offline jfuquay  United States
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Balanced Zen Line Stage Preamp
I’m thinking a similar idea. I’m using a perforated base with standoffs. My 120v safety ground from the IEC is screwed to it and any other chassis grounds needed will be as well. It’s screwed into the sides of the chassis, so that should take care of grounding.
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Old 11th February 2019, 12:16 AM   #13
jfuquay is offline jfuquay  United States
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Balanced Zen Line Stage Preamp
I tested my power supply today. Most of the readings were right, but I got readings of 60 volts on all four the V+ and V- points. According to the guide, it should be 80 volts and 60 volts -- although I don't understand the unregulated rails reference. Do I follow the schematic and try to take a reading at some capacitor or resistor along the way? I was happy that all the readings at the transistor source/drain/gate, both on the PS and also on the main board, were correct.
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Old 11th February 2019, 01:50 AM   #14
elwood625 is offline elwood625  United States
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I have 58.9v at all four of my PS rails. I have two separate power supplies, they all read exactly the same voltage. The 80v is unregulated, since I have the 60v regulated, I'm happy.
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Old 11th February 2019, 02:04 AM   #15
elwood625 is offline elwood625  United States
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I've been reading threads about volume controls. P3 & 4 still bothers me, the four gang stepped pot I have is log not linear. I'm thinking that the pot on the output should be linear to allow a greater degree of adjustment. I don't know enough about this to make a comfortable decision, besides the fact that I already have what I have.
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Old 11th February 2019, 05:10 AM   #16
jfuquay is offline jfuquay  United States
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Balanced Zen Line Stage Preamp
I’m still undecided on P3 & 4. I drilled my back plate this weekend and didn’t make holes for the shafts. I had planned to have them sticking out the back for fine tuning, but am leaning toward either going with resistors in the 430 range. And I still haven’t decided about extension shafts on the selector and I put pots. I supposed it will be easy enough to make them out of aluminum rod and some plastic bushings. There is certainly a lot of back and forth wiring if you bring the signal wires up front.
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Old 12th February 2019, 06:03 PM   #17
jfuquay is offline jfuquay  United States
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Balanced Zen Line Stage Preamp
I'm to the point of wiring the signal inputs and outputs. As I read various articles on balanced circuits (the clearest of these, to me, is at Sound System Interconnection), they say the XLR shield (pin 1) goes to CHASSIS ground. If I do that, what do I do when I wire my selector switch and then the pots? There's no ground lug on my selector switch. Then I'm supposed to connect the grounds out of my P1 and P2 to GND on the IN side of my main PCB. Finally, as I leave P3 and P4, do I ignore the GND lug, since I'm supposed to ground pin 1 of the output XLR to chassis?
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Old 12th February 2019, 07:06 PM   #18
elwood625 is offline elwood625  United States
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Here is what Nelson says:
Speaking of input and output connections, I have not specified connector types for this project. Usually for this sort of project I use both XLR and RCA connectors on both the inputs and outputs. The inputs are female XLR with pin 2 = plus, 3 = minus, and 1 = ground. At the output it is a male XLR connector. In parallel with the XLR connectors are 2 RCA connectors, one for each polarity, with XLR pin 2 connected to the "live" of the positive RCA and pin and XLR pin 3 connected to the "live" of the negative RCA. XLR pin 1 is attached to the grounds of both RCA connectors. These grounds are isolated from chassis ground. The case of the XLR connector, if metal, and shield are attached to chassis ground.




I have no intention of deviating from his recommendations.

As far as grounds go, my selector does not have provisions for ground either. I plan on using a "star" ground. This is a single point where all grounds come together, I have this point just behind the selector switch so the grounds area as close to the connections on the selector switch.. The PC board grounds will also go to the "star" ground point., along with the shielded grounds on my 10K and 5K pots.

There are great articles at PASSDIY regarding grounds and proper wiring. I recommend you read them BEFORE you start wiring.
Now your father ahead of me, still waiting to get my front and rear panels back. I spent the last couple of days rereading the article on BZLS, I've read it again at least a dozen times and I'm comfortable with P 3 & 4 operation. Considering it changes gain AND noise/distortion, adjusting will be by what sounds best. I plan on selecting several different pieces of music and write down the position of P 3 & 4 which gives best sound results. I'm hoping for a happy medium for all the different music types so I don't have to keep adjusting. Otherwise, I'll mark the rear panel for the different knob positions for each music where it sounds best. I may regret having it mounted on the rear panel, however for logistics, it is the best place for it.
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Old 12th February 2019, 07:10 PM   #19
elwood625 is offline elwood625  United States
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The case of the XLR's will go to chassis ground via a star washer on the mounting hardware, anodized alloy is a poor electrical connection and needs to be pierced to the aluminum base metal. The "star" ground will not go to chassis ground.
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Old 12th February 2019, 07:13 PM   #20
elwood625 is offline elwood625  United States
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At PASSDIY there is a tab for gallery, select the tab and then click on preamplifiers. Select BZLS and there are photos and comments from others who have built this in the past. Wiring is shown on most of them, just a thought.
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