I must've bought 20 cases of various sizes over past 3 years from Andrea at:
modu
or
Hi-Fi 2000 contenitori per l'elettronica, case modding HTPC, Galaxy, rack, DIYaudio, computer cases, front panel express, knobs,milled Handles, milled fronts, hi-end,
He can CNC holes in the back & front panels - you just send him a '.dxf' file which can be output from Visio.
I recommend his service.
Andy
Yes... Definitely need a nice alu box...
As for TT... I searched for so long to get the rare vintage like that..
I like L75S because the arm is heavy (easy setup for MC)... Unlike its brother (L75/L78), the arm is rather nice looking...
Heavy arm is good for hard suspension cartridge. As for box, you better use a second smaller one too for trafo & raw PSU so to can keep the hum field away.
R-core can be horribly noisy, in my experience. Maybe I was unlucky.
I have found toroids to be the most reliable, quietest and all round best option, but this is only my subjective experience.
I like the idea of R-core and the lowered/ balanced EMI, but my experience is that they buzz!? Maybe I just bought shite ones. I've had laminated Txs buzz too, but never a toroid.
I have found toroids to be the most reliable, quietest and all round best option, but this is only my subjective experience.
I like the idea of R-core and the lowered/ balanced EMI, but my experience is that they buzz!? Maybe I just bought shite ones. I've had laminated Txs buzz too, but never a toroid.
Good question and I don't know the answer. My raw supply for my folded is in a small steel box (rather thin steel), and the transformer noise seemed much worse when they were mounted in the box. I have often wondered whether they would be so loud in an aluminum chassis.
I was afraid that my wife would turn off the phono preamp because of power consumption, but she turns it off because of the noise!
I don't think there is a difference in intrinsic transformer buzzing between a mild steel case & an aluminium case.
However, I have heard that the case material makes a difference to the SQ of the device:
* best is wood (but how do you shield the internals?)
* next is aluminium
* then is steel.
Irrespective of what metal the case is made of, can I suggest you mount the transformer (whatever type it is) on a 6mm pad of Sorbothane. This prevents any buzz in the transformer laminations from travelling to the case itself.
Regards,
Andy
Yes, I've done that too. It's a good idea. Ideally though, they simply shouldn't buzz at all.
What makes a transformer buzz anyway? Some are silent - others buzz - why!?
There's mechanical transformer noise ... and 'noise' (hum) coming from the speakers, due to the transformer magnetic field "invading" the nearby PCBs, inside the case.
I understand toroids have a more controlled magnetic field than EIs and R-cores? So they should produce less hum through the speakers.
And AIUI, whether an individual transformer buzzes or not is because the laminations are not tight ... this can happen with any sort of transformer, I would think. Toroids are typically potted - I'm not sure whether you can do this with EI & R-core?
Regards,
Andy
AIUI, there are 2 reasons:
1. Bad manufacture - the laminations should be tight and locked into place (like potting a toroid) ... and they aren't.
2. DC on the mains. This can be generated by a number of things:
- your wife's hairdryer
- SMPSUs (like on your PC, modem, D-class amp ...)
- DC-to-AC converters, for those who have solar power.
Regards,
Andy
I have an amp on the bench now.
Today I will couple the toroid supply instead of the lab supply.
I will measure Hum + Noise with the toroid various distances away from the amp PCB.
I will try the PCB on and beside the toroid. I have expectations, but I will reveal answers soon.
if an Rcore is built with balanced windings, i.e. half the primary on one limb and overlain with half the secondary on that same limb, then the two other halves on the spare limb, you should get good cancellation of emitted fields from the windings.
But one still has the exposed core around the bends. I think that exposed core can emit some EMI.
BUT!!!!!
that is not the way most Rcore are built.
Most have the primary on one limb and the secondary on the other limb.
This style of Rcore must emit more radiation than any of the EI, toroid and balanced Rcore.
A C core cam similarly be built up either balanced or unbalanced.
did some H+N measurements for you.
The amp is a Symasym with 5 long legged cap attachments (standing 30mm to 50mm above the PCB) to find a non ringing implementation.
The RF filter is set to 68ns, instead of my proposed final of 660ns
These may make it more susceptible to picking up interference.
With the 300VA toroid transformer @ ~400mm from the PCB the H+N is flickering between 0.0mVac and 0.2mVac
with the transformer close, less than 20mm, to the PCB it measures the same.
TX above the PCB, same
TX below PCB, same
TX standing on edge, same
TX still in edge but rotated through +90° and -90°, same
TX flat and touching the PCB, same.
It makes no difference at the measurement limits of my DMM, nor scope set to 2mV/div, what position, or orientation, or closeness to the Hum+Noise.
Tried, for completeness, moving the live mains cable around the PCB, same.
A RIAA stage with 40dB to 60dB midband gain will be different, especially since the 50Hz gain is roughly 15dB higher
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