LCR Inductor Q

FoMoCo

Member
2012-12-04 10:04 pm
Forgive me if this question has been answered elsewhere or if is common knowledge, but what should the Q value be for an inductor meant for an LCR network. I'm thinking it should be as high as possible?
Thanks in advance.
Unless the designer intended a certain Q (and they shouldn't have) higher is better.

However, you should analyze the part of the circuit the inductor is in. A lot of circuits do not need a hi Q and you'd be wasting your money to seek out the highest Q possible.

Without seeing the circuit there is no definitive answer.
 
The network designer would allow for Q in his design (at least, he ought to). You just have to use the same Q as he designed for. If he doesn't specify Q, then maybe he hasn't thought about it.

This sort of problem does not arise with RC networks, as real capacitors are much closer to an ideal capacitor than any real inductor is to an ideal inductor. The claim in the link about RIAA accuracy only being achieved with LCR is nonsense and can be completely ignored.
 

morinix

Member
2006-06-25 2:40 am
I'm not sure if you are replying to me. But, most of the shortcomings in any inductor you have can usually be compensated for by tweaking the network around the inductor(s) and/or signal conditioning at the input gain stage and/or the makeup gain stage. Winding a perfect 1.8 henry unit is no small feat unless you already have coil winders and experience. I played with the Silk unit and it was good but even that unit's DCR was designed so that right at 20 hz the gain stopped. And man-o-man everyone, except me, charges up-the-wazoo for LCR networks.
 
Yes Robert, I was replying to you concerning your LCR phono preamp. The posts got mixed due to poor timing.
I have been buying some old UTC inductors to make an LCR RIAA EQ. I have the proper values of VIC variable inductors and a few HVC, MQx, ML, that MIGHT work but it would be nice to know if I have the right ones before attempting a build. My inductance meter is pretty good, accurate to 1% and able to read inductance and Q at 100Hz, 1Khz, 10Khz, and 100Khz. I also have a bridge if needed, to measure at the exact freqs, 50Hz, 500Hz... etc. I'm just trying to figure out the details. Don't know if their shunt capacitance is ok. Do you sell your EQ networks seperately from the preamp? Some of us diehards prefer tubes over IC's. I've got a nice Melos GK-1 that I might modify with some LCR's, or better - build from scratch.
 

morinix

Member
2006-06-25 2:40 am
Hi Dshortt9,
Once I found a part that measured close enough on a basic inductance meter I just went online to a LR calculator and found a resistor value that was easy to use to do a frecuency sweep with. Then I built a LR HPF. Then I could get an idea of how flat it was.

Since I was using op-amps it was easy to make filters to correct the anomalies. If all you need is attenuation then it's easy with tubes but if you need boosting also, then it gets harder. Also assuming you are staying with the conventional 600ohm network then driving that with tubes gets a little tricky unless an impedance matching transformer is used (more expense!).

I don't sell the network I used on the Lounge LCR separately because of the correction it needs to work right.