The totals (Vtot = |V+| + |V-|) seem right, both are about 27 V. You probably need to adjust the trimmer potentiometer R22 to center the voltage output. Turn the trimmer until the magnitude of V+ and V- are equal (the value will be about 13 V).
Richard
Richard
I managed to adjust all the voltages. I hope that II won't make any more mistakes🙂 I really appreciate your help.
Glad it worked out. The trimmer provides wide latitude for adjustment, more-or-less indefinite actually.
I've connected the Emerald to my system today. The sound is great!
I think the value of the coupling capacitors is high (6.8uF) and therefore maybe a little bit deep, but I will order capacitors of the right value soon. Richard, congratulations on the design, the sound quality is very good. I show the experimental setup.
I think the value of the coupling capacitors is high (6.8uF) and therefore maybe a little bit deep, but I will order capacitors of the right value soon. Richard, congratulations on the design, the sound quality is very good. I show the experimental setup.
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@atreides
Great that you got it up and running. And... purple. I wasn't expecting purple. 😵
A couple things,
1. You'll want to case those up properly as soon as possible.
2. I agree that 6.8 uF will likely sound ponderous, and recommend a lower value.
3. Please don't use four rectifier bridges with only two secondaries. Use two rectifiers (or just one, even), and connect both boards to the same V++ and V-- output.
Richard
Great that you got it up and running. And... purple. I wasn't expecting purple. 😵
A couple things,
1. You'll want to case those up properly as soon as possible.
2. I agree that 6.8 uF will likely sound ponderous, and recommend a lower value.
3. Please don't use four rectifier bridges with only two secondaries. Use two rectifiers (or just one, even), and connect both boards to the same V++ and V-- output.
Richard
Thank you very much for the advice, I will change the wiring. I was also amazed at the purple colored PCB that I bought from a local DIYer. I will order 2.2uF coupling capacitors, I'm sure it will sound better.
I recently built an Emerald Phono Stage into a preamp I was putting together, an Iron Pre. It works fantastically well, considering the Emerald boards get their power from the Iron Pre, downstream of the Iron Pre's rectification and shunt regulators, and share circuit ground with the Iron Pre. The Emerald itself is not connected to earth ground separate from circuit ground, the earth ground connections are left floating. For output coupling caps, I chose to use a pair of 3.3uF TDK MKC capacitors, as I really liked their sound when used as output coupling caps in a B1 buffer I built.
I've listened to a lot of vinyl since building this and I have nothing but appreciation for the sound. If I crank the volume knob to 11, with no records playing and the phono stage selected as source, I can hear what sounds like static or "shot noise" if I hold my ear right up to the speaker. As the surface noise of a typical record can be heard from a sitting position some distance from the speakers, and at a fraction of this volume setting, this shot noise doesn't concern me. It is an interesting curiosity though.
I've listened to a lot of vinyl since building this and I have nothing but appreciation for the sound. If I crank the volume knob to 11, with no records playing and the phono stage selected as source, I can hear what sounds like static or "shot noise" if I hold my ear right up to the speaker. As the surface noise of a typical record can be heard from a sitting position some distance from the speakers, and at a fraction of this volume setting, this shot noise doesn't concern me. It is an interesting curiosity though.
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"this shot noise doesn't concern me. It is an interesting curiosity though."
The op amps generate voltage noise, as all amplifiers do. For the OPA27 it's something like 4.5 nV/sqrt(Hz). That random noise, filtered through the RIAA filter, is what you hear as the baseline noise of the Emerald - and it's typically the level you describe: audible with the volume turned up and your ear near the speaker. To be clear, it's a function of the op amp and the circuit gain and a matter of physics rather than carelessness.
The op amps generate voltage noise, as all amplifiers do. For the OPA27 it's something like 4.5 nV/sqrt(Hz). That random noise, filtered through the RIAA filter, is what you hear as the baseline noise of the Emerald - and it's typically the level you describe: audible with the volume turned up and your ear near the speaker. To be clear, it's a function of the op amp and the circuit gain and a matter of physics rather than carelessness.
@DRONE7 they're a polypropylene film, MKP cap, designed for EMI suppression and rated for "across the line" use in AC mains filtering. They're made by EPCOS-TDK and cost about $3 on Digi-Key. I found four of them in surplus, 3.3uF, and first used a pair in my B1 buffer as output coupling caps. I loved the sound relative to the 10uF WIMA MKS caps I'd had in there and so I decided to put the other pair in my Emeralds as C3. They are made in 2.2uF values so if I had to do it over again (and spend money), I'd probably buy them in that value.
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Am currently planning to build this and put together a parts list, based on 2 chassis (separate PSU)... but have a quick question...
Is there any advantage (or disadvantage) of also having a a couple of 1000uf caps in the PSU chassis to smooth the DC before it goes into the umbilical and reaches the 1000uf C4 & C5 caps on the boards?
Many thanks!
Is there any advantage (or disadvantage) of also having a a couple of 1000uf caps in the PSU chassis to smooth the DC before it goes into the umbilical and reaches the 1000uf C4 & C5 caps on the boards?
Many thanks!