You did not show us the silent room with the system yet.🙂
P.S. Back from interesting system general to the phono, does it appear steady after some hours by now?
Tomorow, can't post pictures now. FYI along with this room I was doing a complete renovation of my house. It is not acousticaly perfect yet. It is a work in progress which has just started.
Will make some mesurements in the morning.
Will make some mesurements in the morning.
vgeorge,
Very nice build. You are a lucky man. You will have a Simplistic RIAA and a listening room. When I was renovating our house, the idea of a listening room went poof with my wife's comment "I have an idea!"
I am happy though
Very nice build. You are a lucky man. You will have a Simplistic RIAA and a listening room. When I was renovating our house, the idea of a listening room went poof with my wife's comment "I have an idea!"
I am happy though
Hi Andrew
This might be a simple way to measure a system noise.
I would like to do the same measurements but am not sure about the proceedings.
What do you mean by "gain set to zero" ?
I have an old Meridian 101 setup that is totally silent at full volume but I measure circa 140mV Dc in the output (loaded with the speakers).... can I set the DMM to AcV and rely on the measurements ?
Ricardo
Ok Salas, here are some pictures of the room.
I was planing this for some years, but had not the funds to do it.
Also, right before the entrance is my small electronic workshop!
SGregory, I didn't discuss this much with my wife! When she understood what I was doing, she was jealous and coming up with ideas too, but it was very late then! Now she is just complaining that I spend a lot of time there...
I was planing this for some years, but had not the funds to do it.
Also, right before the entrance is my small electronic workshop!
SGregory, I didn't discuss this much with my wife! When she understood what I was doing, she was jealous and coming up with ideas too, but it was very late then! Now she is just complaining that I spend a lot of time there...
Attachments
gain set to zero = volume control at zero output, equivalent to infinite attenuation.
I don't measure output offset with speakers connected.
What is output offset with open output and shorted input?
What is output offset with open output and source connected with gain set to zero?
Does the output offset change with temperature and/or with volume setting?
Connect the speaker. Does the output offset change from any of the previous measurements?
I use an ordinary handheld DMM set to 200.0mVdc and set to 200.0mVac to check the output of the system.
I can often get <0.1mVac and <1mVdc at the output. That is low noise and low offset.
However, the bandwidth of the DVM is not known and it does not have a deliberate noise shaping filter. So I know my measurements are very approximate. They do allow comparisons to be made.
When I connect the source with zero gain setting I expect nothing to change.
When I turn up the gain, I expect a source to send some noise through the system.
With a low gain system and a quiet source I would not expect much deterioration in the noise measurement. I would not expect any audible noise at the 88dB/W @ 1m speakers. I might get a bit of hiss with 93dB/W @ 1m speakers. I don't know what to expect with 105dB/W @ 1m speakers.
I do know that with that high sensitivity that I would set my self gain and noise standards that are way above what is acceptable for 88dB speakers.
I do have a Bench DMM that is rms calibrated up to a quite high bandwidth, but I don't yet have a set of suitable filters for audio noise measurement. I have been following the LNA threads with the intention of getting this part finalised.
I don't measure output offset with speakers connected.
What is output offset with open output and shorted input?
What is output offset with open output and source connected with gain set to zero?
Does the output offset change with temperature and/or with volume setting?
Connect the speaker. Does the output offset change from any of the previous measurements?
I use an ordinary handheld DMM set to 200.0mVdc and set to 200.0mVac to check the output of the system.
I can often get <0.1mVac and <1mVdc at the output. That is low noise and low offset.
However, the bandwidth of the DVM is not known and it does not have a deliberate noise shaping filter. So I know my measurements are very approximate. They do allow comparisons to be made.
When I connect the source with zero gain setting I expect nothing to change.
When I turn up the gain, I expect a source to send some noise through the system.
With a low gain system and a quiet source I would not expect much deterioration in the noise measurement. I would not expect any audible noise at the 88dB/W @ 1m speakers. I might get a bit of hiss with 93dB/W @ 1m speakers. I don't know what to expect with 105dB/W @ 1m speakers.
I do know that with that high sensitivity that I would set my self gain and noise standards that are way above what is acceptable for 88dB speakers.
I do have a Bench DMM that is rms calibrated up to a quite high bandwidth, but I don't yet have a set of suitable filters for audio noise measurement. I have been following the LNA threads with the intention of getting this part finalised.
Last edited:
thanks guys, yes I was after a photo to get a basic layout, I understand you have to be careful with signal path lengths on certain areas in a phono stage
Andrew, just finished my #26 pre and even if there is a little bit more hiss, with my DMM I get 2mV AC at low level the pot and 6mV AC at full.
Something is stange.
Something is stange.
Try to find the culprit in stages.
Test the Power amp alone.
Input shorted and/or loaded with the same resistance that the DCB1 presents.
Then add DCB1, test with input shorted and/or loaded with source resistance. Is the source in the DCB1 case the volume pot?
Test the Power amp alone.
Input shorted and/or loaded with the same resistance that the DCB1 presents.
Then add DCB1, test with input shorted and/or loaded with source resistance. Is the source in the DCB1 case the volume pot?
Thanks for the advise Andrew. I will the next few days, as I suspect the grounding on the DCB1.
But is strange to have a lower reading with a tube DHT pre and have audibly more hiss.
But is strange to have a lower reading with a tube DHT pre and have audibly more hiss.
Nice for listening. Spacious enough too. You will find ways to optimise its reverberation sooner or later, the main thing is you started it.
Its my hunch you mainly measure hum than wide band noise with the DVM. Most have a small low frequency bandwidth. To really see, it takes FFT. But its good to minimize what you can now see anyway.
For sure I will minimise it. I think I know wht' s wrong. After the holidays.
But now a little bit tired and want to listen some music. Building too much the last few days! I think I' m done for this year!
Also RIAA is stable, voltages remained the same for more than 24h always on.
For the room I need to do something to the back and to the sides. We 'll see.
But now a little bit tired and want to listen some music. Building too much the last few days! I think I' m done for this year!
Also RIAA is stable, voltages remained the same for more than 24h always on.
For the room I need to do something to the back and to the sides. We 'll see.
Thank you so much Andrew
I will do the measurements as you suggest and report back.
Ricardo
Nick ,Iko,Ricardo,Merlin,Andrew and all Merry Cristmas and happy new year
All the best to you also....