audio-talk

Good grief! I've been out enjoying myself and drinking lots of beer and you lot have been on here typing up bloody equations! Either way you divide the flippin voltages its still 3db aaannnnddddd as we are loooookin' for a drop from 8 to 5.5v its -3 flippin db....!

LT1084 and 1086

Dave, highly recommended is Audio Measurements by Norman Crowhurst....reprinted book from the 50's very informative and goes into this stuff in great detail. Your other wave forms indicate Even and Odd harmonics are present. To test the response, set the amp output at 1W@1Khz (2.83v into 8R) then sw...

Well spotted that man!

Yep, those are the little blighters. I've asked the guy if its OK for me to pull the duff one apart and check for breaks...

Mike H wrote:17k suggests thin wire yes. Maybe what happened to the naff one, too thin and broke just from being dropped or something. Are they wire ended? Flying leads?

Yes, flying leads. The rating is 5mA not 20 as I said before.

Nah, not an auto-ranging DVM I'm afraid. One is defo OC the other reads 17K7.....also I think these are 5mA not 20 as I first posted...TBH...I'm pretty pissed with this guy, he was slow to respond, slow to communicate and slow to ship and the product is pooh...

Hmmmmmmm, 20mA Nick, they where cheap! Think I'll take a look at the Lundhal's and write a snotty email to mr eBay seller......

Ah! OK.....

Just got a pair of anode chokes from an eBay seller recommended by Dave ( should have known better!). One appears to measure 17.7Kohm and the other open cct! These are small 20ma chokes 500H, does the 17k sound about right?

Is this a good time to mention make-before-break switches or are you not intending to switch it 'live' Phil.......

Right, found me notes about biasing, memory not so dull as I first thought :) Cathode bias suffers from bias modulation under high input signal especially when near cutoff as the cathode voltage rises and the valve is driven out of class A. I also made a note that the bypass caps form a resonant cct...

It's also detailed in Morgans Jones Dave ifnyou have the book.....

Oooh 'tis interesting this, I was just thinking about cathode vs fixed BIAS (as you do naturally!) trying to recall the ups and downs of both as I'm looking at ways of improving me 2A3 PP (gotta keep ahead of Mr I). From a very dull memory, fixed will give more power from a lower HT but requires a m...

Are you feelin alright Phil, that looks almost professional