Search found 72 matches

by Hans
Mon Jul 11, 2016 7:23 am
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 173784

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

Hi Wayne, Getting back to the subject of your design, I made a simulation model, with and without A-Weighting, showing the generated noise referred to the input. I used 2 noiseless transistors and inserted in both a 2 Ohm resistor to simulate the Rbb of the ZTX851 1. Total input noise is as shown is...
by Hans
Sun Jul 10, 2016 2:48 pm
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 173784

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

AD797 is a rotten OPA for either MM or MC though it has applications elsewhere as Guru Scott Wurcer's masterpiece. OPA1612 is similar. Both have EVIL Ib cancelling. I rather think you are just looking at distortion to choose your OPA Ha, ha, what a cheap and predictable reaction. :!: I agree, opa's...
by Hans
Sun Jul 10, 2016 10:12 am
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 173784

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

-70dBm is the number I have seen in the literature most as the theoretical noise floor. All of it is a bit of a moving target. Pops and clicks wouldn't count I guess but crackle would. I think A weighted from 20Hz - 20K Hz is a good way to measure. That is probably the most often used way. The meas...
by Hans
Sat Jul 09, 2016 6:06 am
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 173784

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

Here's more from DBLT101 . For something like the effect of a codec on your vinyl playback chain, you do ABC tests. 2 of these 'presentations' are the same but you NEVER tell your panel this or say they are to find the odd man out. You just ask them to rank the 3 presentations and give them a score...
by Hans
Fri Jul 08, 2016 2:32 pm
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 173784

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

I base my opinion on cutting lacquer masters and checking test pressings for over 15 years. I know when I cut an acetate reference or lacquer it will approach the theoretical noise floor of around -70dBm. As long as my cutting stylus is in good shape and I have the stylus heat set correctly. I actu...
by Hans
Fri Jul 08, 2016 11:48 am
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 173784

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

Ricardo, When you were conducting these listening tests did you measure or characterize overall system noise? I know I keep harping on this but RF/EMI is always the dominant noise source when I setup a phono system. I know you can hear well into the noise floor. I guess I'm wondering how far into t...
by Hans
Fri Jul 08, 2016 8:04 am
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 173784

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

Does ultra low noise on vinyl playback matter? I think so. From analysing my listening test results and ignoring any obvious Golden Pinnae raving, there is a sense of less grittiness and also the system seems to disassociate clicks, pops & record noise from the music. Maybe a noise modulation effec...
by Hans
Thu Jul 07, 2016 11:08 am
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 173784

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

I am not arguing for using electrolytic caps in the MC preamp input. I advocate designing such caps out of audio paths when possible (see Wayne's floating mic preamp to eliminate input caps), but it is worth trying to understand the application before making such a broad sweeping condemnation. Bate...
by Hans
Thu Jul 07, 2016 5:00 am
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 173784

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

Many of us here are circuit designers and viewing a schematic is required before we can intelligently discuss the finer points of a design (details matter). If you are unwilling to share I am perfectly content with not seeing it. 8-) The design will be published in full detail in the next issue Vol...
by Hans
Thu Jul 07, 2016 4:44 am
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 173784

Re: A Low Noise Balanced In Moving Coil Preamp Using the ZTX

The single reason for posting the noise graph was to show that there is a limit to were it still makes sense lower the SNR of the Phone-Preamp, because of LP's surface noise. The used preamp for making the graph has a SNR-A of 75dB ref 0.5mV@1kHz which seems to be more than adequate when driven by a...