Hi,
I finally came around to build mine, not without problems and i could use some help ...
The problem i still face is the fact that in 30% of the time i turn the power on the sound is distorted. This is with both channels.
The power supply measures OK in both cases: +/-12,8V before rectification, +16,3V&-15,8V after rectfication, +/-12.0V after the Hypexregs and all ic's see 23,8V between the pins 4 and 8. There is no DC at the outputs (<1mV) in both cases.
Some initial problems was with the volcb in place the positive rail was almost zero volts, despite the rsgs turning on. Replacing the volcb with some 4k7 resistors and measuring for shorts in the caps i didnt find a problem in the bpbp nor the volcb. In volcb there isnt voltage present on the pins P1 to P10and the resistance is should. I did check for loose metal parts on both pcbs without any clue.
Any suggestions? Damaged positive regs? Something in the outputrelay circuit?
Any help is appreciated!
I finally came around to build mine, not without problems and i could use some help ...
The problem i still face is the fact that in 30% of the time i turn the power on the sound is distorted. This is with both channels.
The power supply measures OK in both cases: +/-12,8V before rectification, +16,3V&-15,8V after rectfication, +/-12.0V after the Hypexregs and all ic's see 23,8V between the pins 4 and 8. There is no DC at the outputs (<1mV) in both cases.
Some initial problems was with the volcb in place the positive rail was almost zero volts, despite the rsgs turning on. Replacing the volcb with some 4k7 resistors and measuring for shorts in the caps i didnt find a problem in the bpbp nor the volcb. In volcb there isnt voltage present on the pins P1 to P10and the resistance is should. I did check for loose metal parts on both pcbs without any clue.
Any suggestions? Damaged positive regs? Something in the outputrelay circuit?
Any help is appreciated!
Hi,
I placed 2x4k7 to simulate the pot and reinstalled the volcb, the preamp is working. The issue that there is occasionally a distorted sound when switching on the powersupply is an issue since i wish to switch the primary with the relays of the maya controller.
However, i have been listening to it for some hours yesterday and today and the problem is gone.... strange. Also the sound changed in this short time from bright, on verge of the aggresive, to a much more detailed and coherent sound. I have no idea what caused the problem but i leave it for now, thanks!
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I placed 2x4k7 to simulate the pot and reinstalled the volcb, the preamp is working. The issue that there is occasionally a distorted sound when switching on the powersupply is an issue since i wish to switch the primary with the relays of the maya controller.
However, i have been listening to it for some hours yesterday and today and the problem is gone.... strange. Also the sound changed in this short time from bright, on verge of the aggresive, to a much more detailed and coherent sound. I have no idea what caused the problem but i leave it for now, thanks!
Hi Gerben,
Sorry to hear that you have some issues.
I have a few questions:
1) 30% of the time you have distortion after turn on. Does this mean that in 70% of all cases everything is working fine, including all steps the VolCB offers for both channels ?
That would imply that you have assembled the VolCB correctly. Since there are only resistors an relays in the circuit path, there is nothing that can cause distortion that I can imagine.
2)You mention an initial problem with the VolCB, making the positive rail almost zero. Do you mean with this that the +12V power supply was almost zero?
What was the cause and how did you solve this problem.
3) You mention having <1mV out in both cases. Is this with vol in the max setting ? If so, that seems O.K. It should become less when stepping down the volume.
4)You mention no voltage on P1 and Pin 10. You probably mean Pin 1 and Pin 8, do you? May I assume that you have connected both pins to the proper GND point on the BPBP board ?
So far I can only imagine 2 possible reasons and assuming you are using the Maya remote controller:
1) the output relay K3 is not switching properly
2) the Channel select relay Re7 on the VolCB is not properly connected or relays K1 and K2 on the BPBP are not switching properly.
Hans
Thanks for your reply!
1)Correct. I also measured every resistor in situ after i soldered it in place, before placing the relays since this was the first time soldering SMD
2)Cause unknown, removed the volcb, placed some resistors and replaced the board and everything is working.
3)Correct and with input shorted. Didnt check with less than 0db
4) My bad, i meant the pins on the volcb. I did place the pins going to ground (4 and8) at the groundplane on the otherside of the board, very close to the net-ties.
I use the extra input board, so no relay7, the relay on this board is switching input relays on the bpbp correctly and i measured every relay for continuity in their energized state.
My wild guess was that the positive regulator got a slightly damaged with the initial issue and sometimes comes "on" slower than the negative supply. I read that the LM4562 IC are prone to a latch when using a single supply and that this might be the cause (?)
Anyway the maya with the volcb and extra input board is working OK!
Mute - does it not 'burn' LM4562 ?
hi all, i was thinking about adding 'Mute' via PIC/Relay - but wouldn't in that case while e.g. music is playing LM4562 see output impedance of 2x22 Ohm ... which would when playing 5-6V RMS (max volume) suddenly cause over 100mA (0.1A) output current ?
An externally hosted image should be here but it was not working when we last tested it.
hi all, i was thinking about adding 'Mute' via PIC/Relay - but wouldn't in that case while e.g. music is playing LM4562 see output impedance of 2x22 Ohm ... which would when playing 5-6V RMS (max volume) suddenly cause over 100mA (0.1A) output current ?
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Using relay K3 works very well for implementing a mute function.
5-6V RMS sounds rather bizar but nevertheless, the LM4562 is short circuit proof and output current will never be more that 50 mA.
For a 22 Ohm resistor that would mean only 55 mWatt !
Hans
P.S. I cannot open the image that you had placed.
Thank you Hans - i didn't know how to 'upload' a pic - if you right click in browser - 'Open Image in another Tab/Window' it does seem to load - but it's only portion of BPBP output stage with mute relay and 2x22Ohm resistors
thank you - all clear - you described earlier in the thread what needs to be done (connecting base of T3 to -VOP would 'close' the relay and shortcircuit those resistors). THanks !!!One last question - and - my BPBP (and VolCB/Maya) are not in metal case - obviously all XLR connections are connected to the same 'ground' plane on BPBP ... but my case ground connection is 'isolated' from BPBP. Should i find a way to connect ground from BPBP to 'Ground' of IEC power input ?
Thank you !
Somewhere there should always be a connection to mains earth, but not every individual box has to be connected with a direct line to mains earth.Thank you Hans - i didn't know how to 'upload' a pic - if you right click in browser - 'Open Image in another Tab/Window' it does seem to load - but it's only portion of BPBP output stage with mute relay and 2x22Ohm resistors
One last question - and - my BPBP (and VolCB/Maya) are not in metal case - obviously all XLR connections are connected to the same 'ground' plane on BPBP ... but my case ground connection is 'isolated' from BPBP. Should i find a way to connect ground from BPBP to 'Ground' of IEC power input ?
Thank you !
And in case of having a plastic case, this is not even an option.
but be sure that cable shields carry the mains earth forward to all members in the chain.
Hans
On another topic... I've just realised what the perfect ready-made case is for the BPBBP with Maya ! And I have one already ! Such a "PING !" moment...
Knob with no position indicator (best for a data wheel), perfect display window, buttons ready to be used - great clean design (in my opinion). Space on the rear for 6 inputs and an output (if you pick the right sockets - my switchcraft ones will have be placed at 90 degrees to normal to fit them, L and R stacked on top each other).
Broken ones are normally around the £50 mark on ebay..
Knob with no position indicator (best for a data wheel), perfect display window, buttons ready to be used - great clean design (in my opinion). Space on the rear for 6 inputs and an output (if you pick the right sockets - my switchcraft ones will have be placed at 90 degrees to normal to fit them, L and R stacked on top each other).
Broken ones are normally around the £50 mark on ebay..
But it wasn’t about valuating tuners, it was just an idea where to find a cheap good looking housing that coould fit the bill for encapsulating the BPBP with Maya ?
Oh, sorry I misunderstood what you were saying and I think you may have misunderstood me too. I was only saying that if we all use up the Quad FM4s, then it's ok because there are other tuners out there too, some better than the FM4 as tuners... to which you replied and I thought you were asking about tuners
On your thought, there are the other, later Quad tuners that have a similar size casing, just likely not as cheap to find, although I dont think they use a knob for tuning.
Someone else showed their BPPBP build using a Cyrus case - think it was on the Maya for BPPBP thread.
With a cheaper build quality, some 80s/early 90s mini-system tuners come to mind too e.g. some Akai's I can think of. Needs to be of an older style that used a knob for tuning whilst also having a numerical display. This kind of thing for example:
Much about design/build quality and cost.. the Quad FM4 ticks those boxes quite easily.
On your thought, there are the other, later Quad tuners that have a similar size casing, just likely not as cheap to find, although I dont think they use a knob for tuning.
Someone else showed their BPPBP build using a Cyrus case - think it was on the Maya for BPPBP thread.
With a cheaper build quality, some 80s/early 90s mini-system tuners come to mind too e.g. some Akai's I can think of. Needs to be of an older style that used a knob for tuning whilst also having a numerical display. This kind of thing for example:
An externally hosted image should be here but it was not working when we last tested it.
Much about design/build quality and cost.. the Quad FM4 ticks those boxes quite easily.
This is the post I was thinking of with the Cyrus case:
Bruno Putzeys Balanced Preamp - Group Buy Part 3
Bruno Putzeys Balanced Preamp - Group Buy Part 3
Yup - an I am the lucky winner who bought it from Nikola.
I must say the more i have been opening it, the more i like how it was constructed !!!
Display looks probably better fit then the original one being OLED ...
... and insides with nice 30VA trafo feeding optimized Sulzer based +/-15V supply that feeds BPBP that has even Bruno's Hypex voltage regulators means - perfect close to power supply.
On top of that simple 7809 fed from same trafo but separate windings gives 9V that Maya needs and Maya feeds VolCB and Output (Standby, Speakers onoff should one have that etc) with 5V.
Last but not least - i think this is the only implementation of VolCB + BPBP that does not use VolCB as regular attenuator but as part of negative feedback loop - only 3 wires from VolCB to BPBP - like a real pot on bruno's schematic. It did need 2 extra resistors on BPBP ... upside - it should work as well if not better then attenuator connected to ground approach , downside (to me not critical) - volume range is not as smooth (starts with +14, then 12.5, 10.3, 8.5, 5.5, 3.8, 1.9, 0.3, -3, -4.4, -5.8, -7.1, -8.5, -9.8, -11, -12.3, -15.3, -16.4 etc by roughly 1db all the way down to -64.6dB) ... you can see 2 bumps that are close to 3dB but for practical listening where you need more loud or less loud - and few 3db steps are easy to hear but rarely i really miss step in between and where they are things are already very loud
Great stuff indeed !