Hi,
Quick question regarding the DBRB diode values.
I have a spare DBRB board that I'd like to get in use. Unfortunately I don't have the correct value diodes mentioned in the BOM that is 2A-100V 25ns ultra fast diode (BYV27-100-TAP).
Closest I can locally find is 2A-200V 25ns (BYV27-200). Would this work even if the Voltage value is 100V higher?
Cheers!
M
Quick question regarding the DBRB diode values.
I have a spare DBRB board that I'd like to get in use. Unfortunately I don't have the correct value diodes mentioned in the BOM that is 2A-100V 25ns ultra fast diode (BYV27-100-TAP).
Closest I can locally find is 2A-200V 25ns (BYV27-200). Would this work even if the Voltage value is 100V higher?
Cheers!
M
Thanks!
I had a feeling that the value is not so critical. But better to be safe than sorry!
Best, m
I had a feeling that the value is not so critical. But better to be safe than sorry!
Best, m
I thought I'd show off my Emerald build and get advice on some noise I'm experiencing.
Overall the sound is very clear with the exception of some humming which is loud enough to be pretty irritating. There is also a smattering of AM/FM radio interference mixed in with the hum, I can hear voices and music. I'm pretty sure it's wired correctly but I've been wrong before 🙂
Overall the sound is very clear with the exception of some humming which is loud enough to be pretty irritating. There is also a smattering of AM/FM radio interference mixed in with the hum, I can hear voices and music. I'm pretty sure it's wired correctly but I've been wrong before 🙂
- The hum occurs across 3 different amps and 2 different turntables
- I've tried shielded cables and shorter cables
- I've tried temporarily lifting the earth on the preamp
- The preamp chassis is unearthed, It only connects to the RCA and Com grounds
- The hum does not occur when the input RCAs are disconnected. This is the only time it doesn't make noise while powered on.
Regarding the hum, if you have the two boxes stacked you may be getting radiated noise from the transformers.
Ty
Ty
Those wooden fronts....so beautiful 🙂
Looks like you are running MM's ?
Some have one pin grounded, that could make a ground loop.
Your dual-mono design seems to have 3 different star-gnd's, one on each PCB and one chassis.
Not sure if this is a problem since it's quiet when unconnected.
Do you still get hum when shorting the inputs ?
Looks like you are running MM's ?
Some have one pin grounded, that could make a ground loop.
Your dual-mono design seems to have 3 different star-gnd's, one on each PCB and one chassis.
Not sure if this is a problem since it's quiet when unconnected.
Do you still get hum when shorting the inputs ?
@ToyBoxx One other thing that strikes me (and 'might' be a root-cause) is that you run your inner rectified PSU cables (albeit 'shielded') right under the phono input/output pads -- no offense, but this layout seems disadvantageous -- I would stack both Emerald PCBs [if case height allows] with the (rectified) AC inputs [back-end] directly facing the two power inputs (making them very short) and then use shielded runs to the input and output signal RCA’s. I am up to six pairs of these phono line-stages (built for friends and family members), and only one board had any noise, which was fixed by redoing the PSU connections more carefully.
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Thanks! I haven't tried shorting the inputs, I'll give that a go. How should the boards and chassis be grounded? As far as I can tell the external phono ground, rca grounds, and pcb grounds are all interconnected in the circuit. I'm not sure how else I would go about wiring that up.
You could make the chassis stud the star ground I guess, but I doubt that is the issue.
For a quick test I would route the power cables as far from the signaltraces as possible, maybe route them close to inside lid and drop them vertically down to enter top of PCB.
...and then route the signal cables below pcb, keep them twisted as far as possible - a one inch loop is a good wifi antenna 😉
cport is right, shielded is optimal - just remember shield only grounds at one end...
For a quick test I would route the power cables as far from the signaltraces as possible, maybe route them close to inside lid and drop them vertically down to enter top of PCB.
...and then route the signal cables below pcb, keep them twisted as far as possible - a one inch loop is a good wifi antenna 😉
cport is right, shielded is optimal - just remember shield only grounds at one end...
OK, I've done some of your recommended tests.
- @TKO956 I ran the preamp side by side with no change
- @kenta16807 shorting the inputs produced the same sound as when the turntable is plugged in
- @cport rearranging the power inputs did nothing. Given they're only an inch or two away from the I/O pads, how much distance do I need to give the power supply wires? There's ~8" of cable inside the enclosure, can the excess pick up RF interference and cause this?
@ToyBoxx Given the PCB placement your pictures show, try going up and over [forming an inverrted (horizontal?) "L" and as directly as possible, as in keeping PSU cables short as possible ] , and leave the signal cables underneath (as shown) -- also try adding a resistor to the star chassis ground (long-shot) [ergo] read through this thread https://www.diyaudio.com/community/...d-paths-to-reduce-hum-etc.211609/post-3002266
Hello hello, sorry I'm late! 😀
Looks great. Maybe rearrange the routing of the power wires to avoid the input section of the PCBs, as others suggested, but it's clear from your description that the root cause is RFI pickup on the input cables. (though I note your later observation, "shorting the inputs produced the same sound as when the turntable is plugged in," is inconsistent with this.)
Oh, and the voltage is often around 13 V ... that's no problem.
For RFI it's the usual tricks: try ferrite beads on the input, a small capacitor across the input, or possibly a ground lift.
One other thing ... just a hunch ... is to disable half the power supply and run both boards from a single diode/transformer section.
Richard
Looks great. Maybe rearrange the routing of the power wires to avoid the input section of the PCBs, as others suggested, but it's clear from your description that the root cause is RFI pickup on the input cables. (though I note your later observation, "shorting the inputs produced the same sound as when the turntable is plugged in," is inconsistent with this.)
Oh, and the voltage is often around 13 V ... that's no problem.
For RFI it's the usual tricks: try ferrite beads on the input, a small capacitor across the input, or possibly a ground lift.
One other thing ... just a hunch ... is to disable half the power supply and run both boards from a single diode/transformer section.
Richard
If i take a look to your picture, i can see that the wiring of the power cables are directly under the output of the pcb. Perhaps you can turn the PCB's in your housing (shorter way), or use larger spacers. Make sure to have more space between the signal and the power.
Solder signal input and output on the top of the pcb.
As said, try with only one transformer, perhaps you have a groundloop belonging to different 0volt/gounding.
Have you isolated the ground connetion to the housing ? I cant see if your housing is metal or other material. If metal you need an isolation...
I use a 10 ohm goundlift resistor, but i have different, own pcb's and use a other supply. The groundlift resistor was very helpful...
Ferrit had changed nothing...
Greets
Peter
Solder signal input and output on the top of the pcb.
As said, try with only one transformer, perhaps you have a groundloop belonging to different 0volt/gounding.
Have you isolated the ground connetion to the housing ? I cant see if your housing is metal or other material. If metal you need an isolation...
I use a 10 ohm goundlift resistor, but i have different, own pcb's and use a other supply. The groundlift resistor was very helpful...
Ferrit had changed nothing...
Greets
Peter
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Toyboxx, disconnect one of the GND wires (emerald board) from ground connection on the Ground (leave right channel connected).
If you have connection from board to the chassis with metal stand off, you already have connected grounds of your system via chassis. So that is your ground loop. If that is not the case (you don't have connection to the chassis) than wiring should be better arranged as Kleinhorn suggested.
If you have connection from board to the chassis with metal stand off, you already have connected grounds of your system via chassis. So that is your ground loop. If that is not the case (you don't have connection to the chassis) than wiring should be better arranged as Kleinhorn suggested.
Hi,
i build a new other MC Preamp, dont tell about...but i have to learn.
The preamp case and the supply case now have a distance for about 1 meter. If i try to put the preamp case on top of the supply case i had hum.
The second part is the turntable supply, it is generating hum into my speakers. If i take the supply connector out, all hum is gone.
TEAC is using a switching power supply for the turntable. I will try a SMPS filter.
One try may be to give your housings distance.
i build a new other MC Preamp, dont tell about...but i have to learn.
The preamp case and the supply case now have a distance for about 1 meter. If i try to put the preamp case on top of the supply case i had hum.
The second part is the turntable supply, it is generating hum into my speakers. If i take the supply connector out, all hum is gone.
TEAC is using a switching power supply for the turntable. I will try a SMPS filter.
One try may be to give your housings distance.
Hi there,
A few new pictures of my build.
What's new is tone control (bass & treble) which is quite useful for some old pressings (some of them lack of bass etc.). My main preamp dosn't have it so I decided to add it to the phono preamp.
I used similar shunt power supply as for Emerald Phono Stage, also OPA27 opamps, all caps and resistors precisely paired. Long axles to shorten potentiometers' wires. Bistable switch controller to use the tone control or to bypass it (so called "direct" mode, default).
All PCBs fit the room tightly like it was planned but it was a pure coincidence 🙂
I know the knobs are quite big and they don't look good but bigger ones let me set the tones more precisely.
What's next - currently I'm running MC cart Phasemation PP-200 so I'll try OPA1611 in phono section (at least in the first stage), let's experiment a bit. Btw, for the new cart 83ohm input impedance appeared to be the best.
A few new pictures of my build.
What's new is tone control (bass & treble) which is quite useful for some old pressings (some of them lack of bass etc.). My main preamp dosn't have it so I decided to add it to the phono preamp.
I used similar shunt power supply as for Emerald Phono Stage, also OPA27 opamps, all caps and resistors precisely paired. Long axles to shorten potentiometers' wires. Bistable switch controller to use the tone control or to bypass it (so called "direct" mode, default).
All PCBs fit the room tightly like it was planned but it was a pure coincidence 🙂
I know the knobs are quite big and they don't look good but bigger ones let me set the tones more precisely.
What's next - currently I'm running MC cart Phasemation PP-200 so I'll try OPA1611 in phono section (at least in the first stage), let's experiment a bit. Btw, for the new cart 83ohm input impedance appeared to be the best.
Attachments
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