Search found 28 matches

by AnalogJoe
Wed Jun 03, 2020 5:55 pm
Forum: Pro Audio Design
Topic: Low Noise Transistors: Comparing the ZTX1053A and ZDT1053 (Dual) vs. the ZTX689B and ZTX851
Replies: 24
Views: 53437

Re: Low Noise Transistors: Comparing the ZTX1053A and ZDT1053 (Dual) vs. the ZTX689B and ZTX851

One of my objectives is to find higher-gain low noise transistors in the Zetex series that would serve well in mic preamp applications where the absolute lowest rbb' isn't necessarily required due to the higher source impedance. Fortunately there are quite a few. We're lucky we can use these power ...
by AnalogJoe
Wed Jun 03, 2020 5:50 pm
Forum: Test, Measurement and Repair
Topic: Classic Bead Tantalum Capacitor Failure
Replies: 17
Views: 47468

Re: Classic Bead Tantalum Capacitor Failure

Turns out I had already posted the correspondence with Bob Pease. You'll find the Tantalum measurements along with Bob's scrawled comments here: https://www.ka-electronics.com/images/pdf/Pease_Correspondence_2.pdf Wayne, those are real gems right there! I enjoyed reading that, thanks! I have an AP-...
by AnalogJoe
Tue Jun 02, 2020 11:40 am
Forum: Test, Measurement and Repair
Topic: Classic Bead Tantalum Capacitor Failure
Replies: 17
Views: 47468

Re: Classic Bead Tantalum Capacitor Failure

mediatechnology wrote:
Tue Jun 02, 2020 7:39 am

I have a THD plot of tantalum capacitors I did for the late Bob Pease that I should find and post.

That would be great !
by AnalogJoe
Tue Jun 02, 2020 7:17 am
Forum: Pro Audio Design
Topic: Low Noise Transistors: Comparing the ZTX1053A and ZDT1053 (Dual) vs. the ZTX689B and ZTX851
Replies: 24
Views: 53437

Re: Low Noise Transistors: Comparing the ZTX1053A and ZDT1053 (Dual) vs. the ZTX689B and ZTX851

You might want to check out this webpage http://www.dicks-website.eu/low_noise_amp_part3/part3.html they compare several transistors, apparently the ones with the lowest noise are the ZTX853 with a merely 1.62 Ohm of base spreading resistance, or 0.22 nV/rootHz. Your test setup seems to be better th...
by AnalogJoe
Mon Jun 01, 2020 1:54 pm
Forum: Test, Measurement and Repair
Topic: Classic Bead Tantalum Capacitor Failure
Replies: 17
Views: 47468

Re: Classic Bead Tantalum Capacitor Failure

I find todays electrolytics to be very impressive, for example, take a look at Panasonic FR series of capacitors, they are very low impedance and are rated 5000 to 10000 hrs at 105 °C, those caps will last a long time. Some electrolytics are crap thou, my LG Plasma TV refuses to turn on the first 2 ...
by AnalogJoe
Fri May 29, 2020 11:51 am
Forum: Test, Measurement and Repair
Topic: Classic Bead Tantalum Capacitor Failure
Replies: 17
Views: 47468

Re: Classic Bead Tantalum Capacitor Failure

Old thread, but I also had the same problem with a Tektronix pulse generator, the tantalum bypass caps kept blowing up, I replaced them with Panasonic aluminum electrolytics and problem solved. I dont know why would anyone use Tantalum in audio equipment, I cringed when I saw a pair of 47uF Tantalum...
by AnalogJoe
Fri May 29, 2020 10:43 am
Forum: Document
Topic: All-Pass Circuits
Replies: 4
Views: 21567

Re: All-Pass Circuits

JR. wrote:
Fri May 29, 2020 9:10 am
Back last century, all pass filters were used inside premium analog loudspeaker crossovers to generate time alignment delay.

JR
They are still used today!, Douglas Self talks about their application in his Active Crossover Design book. Although most are replaced by DSP these days.
by AnalogJoe
Thu May 28, 2020 10:22 pm
Forum: Document
Topic: All-Pass Circuits
Replies: 4
Views: 21567

Re: All-Pass Circuits

There is a great treatment by Kugelstadt in TI's "Opamps for Everyone" chapter on All-Pass filters, including higher order All-pass. I had to design and build high order all-pass filters to implement analog delays for my PhD project, I wrote an optimization routine in MATLAB to find the optimum time...