In this photo I had not yet connected the power transformer shield wire (green/yellow on the Triad VPM24-1040) to the ground lug.
But, aside from the PT shield wire there is only the one short green wire from the IEC inlet Earth Ground tab to the chassis bolt.
Attachments
I sorted out the psu cables and have now tried a two case version and the hum is down to negligable. Too much volume equals hum, but that is way too much volume 
When I first turned it on, there was as much hum as before but it was reduced significantly when I also connected the turntable. I never thought that would make a difference. Then I switched back to a single case again with a jumper between psu coms. Everything connected and switched on... satisfaction. The same amount of hum as with an umbilical, which is almost none except for when going loud.
Conclusion: build is done and I will order a single case for both psu and phono. Will post pictures when complete.
Thank you all!
When I first turned it on, there was as much hum as before but it was reduced significantly when I also connected the turntable. I never thought that would make a difference. Then I switched back to a single case again with a jumper between psu coms. Everything connected and switched on... satisfaction. The same amount of hum as with an umbilical, which is almost none except for when going loud.
Conclusion: build is done and I will order a single case for both psu and phono. Will post pictures when complete.
Thank you all!
Just a friendly reminder that the Emerald, like all voltage mode preamplifiers, will be noisier when the input jacks are left disconnected from the cartridge. You want to put a dummy load on the input, or short them out entirely, when testing.
With shorted inputs, there should not be any hum present on the output signal.
With shorted inputs, there should not be any hum present on the output signal.
Hi Richard...
Thinking out loud here but welcome your comments please...
I mostly use my Emerald to rip LPs and have it connected directly to an M Audio Audiophile 24/96 card on a dedicated PC.
The M Audio card has switching for Consumer (-10dB) and Pro (+4dB) so with a slight tweak to Phono Stage gain the Emerald outputs just enough signal not to require any further amplification.
Now I have upgraded the sound-card to an M Audio Audiophile 192 which has no 'Consumer' switch and uses only Pro (+4dB) input settings.
M Audio cards have no input mixer controls and rely on being fed a correct level. (Further they clip if fed more than 1.4v so using the Emerald into and outputting the line level from my audio systems Amplifier is not suitable either.)
Consequently the signal level is now far too low and requires the Phono Stage Gain to be set at 47dB to achieve a useful output to the sound-card. As my cartridge is a Grado with a healthy 5mv output this possible overdrives the op-amp ? as the sound is substandard. (Recording at the lower gain and amplifying within Audacity is substantially better)
I see from the Emerald BOM and worksheets that the calculations for gain is predicated on the -10dB consumer standard with Nominal output of 316 mV and if I change that on the worksheet to 0dB (Nominal output of 1000 mV) I get a recommended 46dB gain for 5mv in.
This is what I arrived at by trial and error....note to self... Read the documentation first !
I am assuming that there is not a way to increase the output of the second stage of the Emerald whilst leaving the first stage Phono Gain at 37dB ?? and my option is to use some additional amplification between the Emerald and the M Audio sound-card ??
Bob.
Thinking out loud here but welcome your comments please...
I mostly use my Emerald to rip LPs and have it connected directly to an M Audio Audiophile 24/96 card on a dedicated PC.
The M Audio card has switching for Consumer (-10dB) and Pro (+4dB) so with a slight tweak to Phono Stage gain the Emerald outputs just enough signal not to require any further amplification.
Now I have upgraded the sound-card to an M Audio Audiophile 192 which has no 'Consumer' switch and uses only Pro (+4dB) input settings.
M Audio cards have no input mixer controls and rely on being fed a correct level. (Further they clip if fed more than 1.4v so using the Emerald into and outputting the line level from my audio systems Amplifier is not suitable either.)
Consequently the signal level is now far too low and requires the Phono Stage Gain to be set at 47dB to achieve a useful output to the sound-card. As my cartridge is a Grado with a healthy 5mv output this possible overdrives the op-amp ? as the sound is substandard. (Recording at the lower gain and amplifying within Audacity is substantially better)
I see from the Emerald BOM and worksheets that the calculations for gain is predicated on the -10dB consumer standard with Nominal output of 316 mV and if I change that on the worksheet to 0dB (Nominal output of 1000 mV) I get a recommended 46dB gain for 5mv in.
This is what I arrived at by trial and error....note to self... Read the documentation first !
I am assuming that there is not a way to increase the output of the second stage of the Emerald whilst leaving the first stage Phono Gain at 37dB ?? and my option is to use some additional amplification between the Emerald and the M Audio sound-card ??
Bob.
I will have to do some study as I'm not quite sure what changes I need to make to the Sapphire.....
I will open it and look but I'm fairly certain I built the closed loop version using the standard BOM and perhaps no switchable gain...it was a while ago (but not the old version)
Presume I could add a switch externally and have the Sapphire usable for either line or headphones ?? It will do double duty ?
That would be ideal.
I will open it and look but I'm fairly certain I built the closed loop version using the standard BOM and perhaps no switchable gain...it was a while ago
(but not the old version)Presume I could add a switch externally and have the Sapphire usable for either line or headphones ?? It will do double duty ?
That would be ideal.
Great ! last question...can I run both the Sapphire and the Emerald from the same transformer/s ?
I have a pair in a separate housing which I attach to Sapphire or the Emerald depending on which I'm using.
Can I use both from the same supply with the Emerald connected to the Sapphire as a line stage ?
Bob.
I have a pair in a separate housing which I attach to Sapphire or the Emerald depending on which I'm using.
Can I use both from the same supply with the Emerald connected to the Sapphire as a line stage ?
Bob.
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That's a definite ... maybe.
Yes, sharing a single power supply between the four boards should work. Sometimes, however, it can induce hum due to ground loops. You'll have to try and see.
If you have two transformers, say for dual mono setup, you can use one for the Sapphire and one for the Emerald. That I know will work.
Yes, sharing a single power supply between the four boards should work. Sometimes, however, it can induce hum due to ground loops. You'll have to try and see.
If you have two transformers, say for dual mono setup, you can use one for the Sapphire and one for the Emerald. That I know will work.
Yes, though when I upgraded from one transformer to dual mono for the Emerald I was so impressed I swore never to go back !!
Besides.. I have been using large EI transformers to date and getting a pair of low profile toroids will allow me to finish the build for the Emerald. Pix to follow..eventually.
Besides.. I have been using large EI transformers to date and getting a pair of low profile toroids will allow me to finish the build for the Emerald. Pix to follow..eventually.
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New power supply for Emerald (Tested )so that I have two...one for the Emerald and one for the Sapphire.
Next to try Turntable>Emerald>Sapphire (as line stage)>M-Audio Audiophile 192 and recording !
Yes the box is a little odd but there were two of them for $5.00 the pair....at the recyclers and they looked ideal for an Emerald and its supply
)so that I have two...one for the Emerald and one for the Sapphire.Next to try Turntable>Emerald>Sapphire (as line stage)>M-Audio Audiophile 192 and recording !
Yes the box is a little odd but there were two of them for $5.00 the pair....at the recyclers and they looked ideal for an Emerald and its supply
Attachments
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Hi all, my build is hopefully nearing completion, but I'm going round in circles trying to work out how to wire up the additional input selector and stepped attenuator. Images below.
I've cobbled together this 'schematic' to show what I'm currently thinking. The bit I'm unsure about is the lack of ground connection between the attenuator (bottom right) and the input selector (bottom left), and whether I actually need to wire the ground from each phono socket to the input selector? As per the schematic, and based on what I've noticed from other input selectors, it seems fairly typical to tie the grounds together at the sockets, so could I do away with the ground connections between sockets and input selector?
Any other comments/corrections, very much appreciated.
I've cobbled together this 'schematic' to show what I'm currently thinking. The bit I'm unsure about is the lack of ground connection between the attenuator (bottom right) and the input selector (bottom left), and whether I actually need to wire the ground from each phono socket to the input selector? As per the schematic, and based on what I've noticed from other input selectors, it seems fairly typical to tie the grounds together at the sockets, so could I do away with the ground connections between sockets and input selector?
Any other comments/corrections, very much appreciated.
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