Hi everyone !
I apologize in advance to you Steph, for opening a new topic on EAR 834+hum !
I assembled an EAR 834 several months ago now. It works very very well. I followed Steph's BOM, his layout is partially respected because:
I use a passive volume attenuator (shunt dale resistor)
the RCAs are all on the top of the chassis
I installed an EMI filter (to try to reduce the hum)
We are talking about a light hum, imperceptible at normal listening volume, but very present. Two hypotheses: either I had not noticed it before, or it appeared gradually. I'm not sure, because hum is different with both turtables :
I have a Technics SL1200 MK2 and a recent MK7. The hum is much more attenuated with the MK7. After several tests I am 95% sure that the hum comes from the EAR 834, because in my tests there is more or less hum each time the EAR 834 is present. Everything is connected to a power strip equipped with an EMI filter. I think the hum attenuation with MK7 is due to its ground connection (3-pin power cable like a computer power supply).
No hum with MK2 in the integrated preamp of my REGA amplifier, same with MK7, same with Phono Preamp Aiyima Tube T3, no hum. If I plug the EAR 834 into the AUX or CD line level input of my Rega amplifier, the hum is a little more acceptable and attenuated, but still present. The hum is at its strongest with MK2 ---> EAR 834 ---> Line Level Amp. I connected the phono gnd and the EAR 834 gnd together, first in front, then I tried on the side as in the photo, the hum does not change.
I had hum with a standard ALPS potentiometer and I also have some with the shunt attenuator. Output gnd was on the chasis with this ALPS. Now I think is going in the chassis thought shunt steel shaft. This shunt provide (L+)-(L-)/(R+)-(R-) input / (L+)-(L-)/(R+)-(R-) output , negatives are chassis grounded i see with my multimeter. So there is hum with ALPS and with Shunt.
Input and Output I use are gold-plated banana connectors, to facilitate maintenance. the input and output wires are silver plated, dedicated to speakers normally, they may have too much resistance? They are about 2mm in diameter, teflon insulated I think, bought in a store specializing in loudspeakers, thicker than traditional copper shielded wires.
I have a hypothesis to submit to you:
I use DALE 1/2w resistors for the two 2M resistors that are in the RIAA area of the circuit. Is it possible that this power is not sufficient there?
I'm using this 50k shunt attenuator without the 68k output resistor provided for the 50K ALPS Pot on the board. I'm using the Steph jumpers. Should I use the 68k resistors necesarly ?
I use x3 ECC83s, equivalent to 12AX7 I think. I read on the EAR 834 internet culture... that 12AX7 on V1+V2+V3 should induce a change of 68K 3W 1% by 120K 3W 1%.
Input and Output are gold-plated banana connectors, to facilitate maintenance. the input and output wires are silver plated, dedicated to speakers normally, they may have too much resistance? They are about 2mm in diameter, teflon insulated I think, bought in a store specializing in loudspeakers, thicker than traditional copper shielded wires.
Thanks you for watching !
