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bikerhifinut · 5th Aug 2020, 11:35 pm

So the VSPS is built on perf board using a pair of NE5534 rather than a single NE5532.
Took a bit of fault finding at first, until I twigged. apart from an initial cock up with the feedback connections, I discovered I hadn't actually connected pin6 of either chip which is the output. That explained the total silence then.
Running it off a 15 0 15 supply using a couple of 10 x AA holders, I pinched the extra one out of my battery powered sig gen.
First impressions are that its very quiet on the hiss, bearing in mind I configured it for 50dB gain. using 220R for R2. Sound quality on initial listening and without any loading capacitor on the input seems Very good and not too lively so maybe I'll omit the 100pF loading cap with my standard Ortofon 2M.
There is however a bit of what I think is instability when the wicks turned right up, I hear a "scratting sound" it's regular and therefore its not an intermittent or dry joint I think.
I wont be able to get the Scope on it for a week or two due to being dragged away for a while.
I haven't put a small value ceramic capacitor directly across the power in pins of the chips, so that would be a first resort. After that I wouldn't know where to look for this.
I did do something that probably I didn't need to do and that was to put 47uF in series with R2 to ground, and maybe that's the cause but I doubt it. its an easy fix to simply short out the capacitor rather than rive it out of an already crammed board.
I also used a 0.47 uF at the input as a DC blocker, and a pair of 470uF across each power rail to ground which I felt was sensible. Even though its battery powered.
I wondered if knocking the gain back to 40dB would calm things down a bit, but in my set up 50dB gain is pretty much where I want it.
I started out quite neat but by the end it got a bit scrappy underneath the perf board but I don't think I have any strange wire routing. I will say that I absolutely detest soldering onto the tiny close spaced pins of a DIL 8pin IC holder, and the perf board has a habit of peeling off the copper circle round each perf hole which don't help matters.
If I was to look at this as a keeper of a circuit I think I'd get a PCB done for it. Its early days yet for it.
A.

5th Aug 2020, 11:35 pm	#28
bikerhifinut Octode Join Date: Nov 2013 Location: Penrith, Cumbria, UK Posts: 1,993	Re: Simple Op Amp RIAA preamp 1st lash up So the VSPS is built on perf board using a pair of NE5534 rather than a single NE5532. Took a bit of fault finding at first, until I twigged. apart from an initial cock up with the feedback connections, I discovered I hadn't actually connected pin6 of either chip which is the output. That explained the total silence then. Running it off a 15 0 15 supply using a couple of 10 x AA holders, I pinched the extra one out of my battery powered sig gen. First impressions are that its very quiet on the hiss, bearing in mind I configured it for 50dB gain. using 220R for R2. Sound quality on initial listening and without any loading capacitor on the input seems Very good and not too lively so maybe I'll omit the 100pF loading cap with my standard Ortofon 2M. There is however a bit of what I think is instability when the wicks turned right up, I hear a "scratting sound" it's regular and therefore its not an intermittent or dry joint I think. I wont be able to get the Scope on it for a week or two due to being dragged away for a while. I haven't put a small value ceramic capacitor directly across the power in pins of the chips, so that would be a first resort. After that I wouldn't know where to look for this. I did do something that probably I didn't need to do and that was to put 47uF in series with R2 to ground, and maybe that's the cause but I doubt it. its an easy fix to simply short out the capacitor rather than rive it out of an already crammed board. I also used a 0.47 uF at the input as a DC blocker, and a pair of 470uF across each power rail to ground which I felt was sensible. Even though its battery powered. I wondered if knocking the gain back to 40dB would calm things down a bit, but in my set up 50dB gain is pretty much where I want it. I started out quite neat but by the end it got a bit scrappy underneath the perf board but I don't think I have any strange wire routing. I will say that I absolutely detest soldering onto the tiny close spaced pins of a DIL 8pin IC holder, and the perf board has a habit of peeling off the copper circle round each perf hole which don't help matters. If I was to look at this as a keeper of a circuit I think I'd get a PCB done for it. Its early days yet for it. A.