Search found 40 matches

by cv
Fri May 22, 2020 11:16 am
Forum: Speakers
Topic: Something stirs in the Undergrowth
Replies: 2802
Views: 1148909

Re: Something stirs in the Undergrowth

Here's my very rough interpretation of this business. Not because I'm convinced it's correct but if it is, I've found it helpful for my own intuition. First aspect: We know from electronics that if you are driving a purely reactive load with a voltage, the current is 90 degrees out of phase and as a...
by cv
Thu May 21, 2020 7:03 pm
Forum: Speakers
Topic: Something stirs in the Undergrowth
Replies: 2802
Views: 1148909

Re: Something stirs in the Undergrowth

Thanks for reposting that Mark. Probably the single most important post in the history of the joelist!
by cv
Sat May 16, 2020 8:56 pm
Forum: Everyones Projects
Topic: 801a maximised class A2 excursion.
Replies: 138
Views: 38206

Re: 801a maximised class A2 excursion.

What a blast from the past! Just to point out "pad" is superfluous.

Ps JamesD - great to see you back!
by cv
Fri Mar 20, 2015 9:53 am
Forum: Speakers
Topic: Something stirs in the Undergrowth
Replies: 2802
Views: 1148909

Another thought...

MJ, Just occurred to me, why not try: 288H on a 200Hz horn from 500-2kHz Radian on an 800Hz horn 2kHz+ You could retain the Fostex but cross it lower, or try running the Supravox up to 500Hz (though the floor location is probably not ideal) or replace the Fostex with a high efficiency driver to cove...
by cv
Tue Mar 11, 2014 12:00 pm
Forum: Speakers
Topic: Something stirs in the Undergrowth
Replies: 2802
Views: 1148909

tickle

Nice work Mark, so it would appear that the problem is the horn. But how/why? I'd be very tempted by these meself (had I the cash): http://www.horns-diy.pl/tractrix110.html Lynn - I agree with Mark re 10Hz through the amp if the PSU and internal time constants are up to it. Voltage handling on the O...
by cv
Sat Mar 08, 2014 9:52 pm
Forum: Speakers
Topic: Something stirs in the Undergrowth
Replies: 2802
Views: 1148909

Interesting note regarding series drivers. In theory, if the drivers are identical and see the same acoustic loading, there should be absolutely no difference in series vs parallel connection. This is easy to see - given the above criteria, in series, they will each have exactly the same voltage acr...
by cv
Sat Mar 08, 2014 9:44 pm
Forum: Everyones Projects
Topic: Gary Pimm's CCS
Replies: 4
Views: 5325

Hey Gary, I had a good read of your stuff online - some wonderful info there. Between the various design insights, datasheets and LTSpice, I should be good. Had much the same thoughts as you regarding the trade-off between high Vds/low capacitance and power dissipation. Fortunately, I think I can af...
by cv
Sun Mar 02, 2014 1:54 pm
Forum: Speakers
Topic: Something stirs in the Undergrowth
Replies: 2802
Views: 1148909

Cap couple sig gen to amp input with a high value series resistor, say 22k to 100k so music signal isnt shorted by the sig gens low output impedance. As for low or high freq, I reckon low so as to get cone moving without draining the amps power! But do try both. Sorry for terseness am on phone... Ps...
by cv
Sun Mar 02, 2014 10:27 am
Forum: Speakers
Topic: Something stirs in the Undergrowth
Replies: 2802
Views: 1148909

Quick one... agree that spider hysteresis could be an issue (thats the appeal of compression drivers for me) so Mark, rather than a phase plug try a tickler signal...
I suspect this is why some people prefer noisier amps...
by cv
Fri Feb 28, 2014 12:26 pm
Forum: Speakers
Topic: Something stirs in the Undergrowth
Replies: 2802
Views: 1148909

With an SE amp, cathode feedback will increase Zout (eg unbypassed cathode resistor). Disadvantages: 1) Output stage has less gain so you need a very capable driver that can swing loads of volts. 2) Output transformer distortion increases with increased driving impedance. But as you want 120Hz and h...
by cv
Fri Feb 28, 2014 11:29 am
Forum: Speakers
Topic: Something stirs in the Undergrowth
Replies: 2802
Views: 1148909

Hey Mark, Actually if I'm going to trial a back-horn, might as well use the 8PE21 , it's got low Qts and sounds good ( probably smoother than Lowthers and many Fostex ) . Just need someone to loan me one of those Planet10 cabinets they have cluttering up the garage .... maybe ! Having looked at some...
by cv
Fri Feb 28, 2014 10:13 am
Forum: Everyones Projects
Topic: Gary Pimm's CCS
Replies: 4
Views: 5325

Hey Gary, Don't worry - it was more if you had some recommendations already. Salas at diyaudio has some interesting schemes and I've seen the IRFBC20 recommended elsewhere. I will (when I get time) try and model some up accurately and compare to your designs in LTSpice, that should give a decent ind...
by cv
Wed Feb 26, 2014 7:28 pm
Forum: Speakers
Topic: Something stirs in the Undergrowth
Replies: 2802
Views: 1148909

Totally what Jan said! With a SET amp, you can just have cathode feedback, though a disadvanatge is you would need more OPT inductance to keep distortion low. Anyway we can discuss potential schemes later... see if you like the sound first. If you get a loudspeaker box design program or spreadsheet ...
by cv
Wed Feb 26, 2014 1:35 pm
Forum: Everyones Projects
Topic: GK-71 - economical build.
Replies: 497
Views: 173739

Quite right... done!
by cv
Wed Feb 26, 2014 1:35 pm
Forum: Everyones Projects
Topic: Gary Pimm's CCS
Replies: 4
Views: 5325

Gary Pimm's CCS

New thread where this belongs... While you're here Gary, I'm considering using a CCS to load a single ended VFET; I'm thinking around 1A current and a max swing of 8V (if that) across the load. Any recommendations for devices / particular choice of topology from your own variations? *Most* appreciat...