Search found 208 matches

by Ian444
Wed Oct 17, 2012 10:38 am
Forum: Trainwreck Discussion
Topic: new 2XEL84 Rocket
Replies: 23
Views: 7938

Re: new 2XEL84 Rocket

I have a couple of old guitar amps from the late 60's, which I like a lot, and have also heard "old iron" in hifi amps. I've heard Chinese vs Magnetic Components in one guitar amp I built, I have Korean iron in a 4 x EL34 Bronx amp and I've heard some Edcors in a hifi amp. If I lived in USA, I would...
by Ian444
Fri Aug 17, 2012 10:33 pm
Forum: Technical Discussion
Topic: Screen grid regulator
Replies: 15
Views: 6549

Re: Screen grid regulator

He has put a couple of 1uF caps on each heater line F1 and F2, in the amp schematic. Some guys at diyaudio have been getting a lot of power out of that amp with higher B+ and different output tubes, 50W to 80W per channel has been achieved, even more IIRC, but the tubes are not current production.
by Ian444
Thu Aug 16, 2012 11:32 am
Forum: Technical Discussion
Topic: Screen grid regulator
Replies: 15
Views: 6549

Re: Screen grid regulator

Yes, the original DCPP ripple filter has a 47K/1M voltage divider feeding the gate of the mosfet, but this variation has a 180K/540K voltage divider which results in 3/4 of the B+ voltage to be filtered and fed to the screens and preamp stage. The experiment was simply to lower the screen voltage in...
by Ian444
Thu Aug 16, 2012 8:02 am
Forum: Technical Discussion
Topic: Screen grid regulator
Replies: 15
Views: 6549

Re: Screen grid regulator

Yes, very nice drawing, there looks to be a few minor errors but the gist is there I think. I do like hand-drawn schematics. Can't quite decipher the tone controls. I have never heard of that model, looks like a barrel of fun! Just as a quick update to the original post, that screen regulator seems ...
by Ian444
Fri Dec 30, 2011 12:14 am
Forum: Technical Discussion
Topic: Screen grid regulator
Replies: 15
Views: 6549

Re: Screen grid regulator

Yeah, I guess I need to HTFU. But it does sound good with the lowered screen voltage... Just worries me having an old amp running near the limits, it will get cranked up to near max at a gig and I don't want it to drop its bundle :) I guess the confidence comes with experience.
by Ian444
Mon Dec 26, 2011 11:14 pm
Forum: Technical Discussion
Topic: Screen grid regulator
Replies: 15
Views: 6549

Screen grid regulator

I recently bought an old guitar amp (Vadis LB60 Extended Range) cheap, gave it a good looking over and fired it up. Here's an example pic and schem. I brought it up on a variac and noticed a fairly high B+ over 470V and 460V on the screens. The outputs are 2 x 6CA7, I was thinking the screen grid vo...
by Ian444
Fri Nov 11, 2011 8:24 am
Forum: Garage Talk
Topic: Prettty girl.....Pretty guitar
Replies: 61
Views: 19315

Re: Wanna get whacked?

Very nice Zippy, that girl has been trained by a master. Good to see young ones with a solid foundation in the basics of their trade.
by Ian444
Thu Oct 20, 2011 10:17 am
Forum: Technical Discussion
Topic: G2 power testing and conduction angle
Replies: 54
Views: 12985

Re: G2 power testing and conduction angle

Azat, I'm in Briso, would be nice to catch up with you one day. I thought you were in WA? pdf64, I'm using a Fluke 123 scopemeter, next time I run an amp up, I'll compare that with a Fluke 73 and a rms-reading $40 cheapie DMM. I simply measure the AC voltage drop across the screen grid resistor, and...
by Ian444
Wed Oct 19, 2011 10:27 am
Forum: Technical Discussion
Topic: G2 power testing and conduction angle
Replies: 54
Views: 12985

Re: G2 power testing and conduction angle

Azat, for what its worth, I've only been working with valve amps for a few years, my 2 cents, the screen grid is rated for max wattage, e.g. the screen on a JJ EL34 is rated max 8W. If you can measure the RMS voltage across the screen grid resistor, you can then calculate the power the screen grid i...
by Ian444
Thu Oct 06, 2011 8:22 am
Forum: Technical Discussion
Topic: Bulletproofing an amp?
Replies: 40
Views: 9233

Re: Bulletproofing an amp?

A simple flashing red LED on the front of the amp to indicate an out of tolerance difference in cathode currents between 2 tubes of a 2-tube PP amp would be nice. Anyone got a simple schem? Just an LED warning to say all is not quite right, take me to the tech.
by Ian444
Fri Sep 16, 2011 5:40 am
Forum: Garage Talk
Topic: Gibson Guitar Factory Raided by Goon-squad
Replies: 45
Views: 9031

Re: Gibson Guitar Factory Raided by Goon-squad

I listened to the soundcheck radio article. I think the underlying bad vibe here is the total stupidity of the human race. This underlying stupidity demonstrates a total lack of seeing the "big picture" and is obvious in my country Australia also. Putting the onus on the owner of a guitar to prove i...
by Ian444
Mon Aug 22, 2011 12:26 am
Forum: Garage Talk
Topic: Prettty girl.....Pretty guitar
Replies: 61
Views: 19315

Re: Prettty girl.....Pretty guitar

Stumbled across this, reminded me of this thread.

http://www.youtube.com/watch?v=XuX2VFSBOHM&NR=1

She really rips it up.
by Ian444
Wed Aug 10, 2011 9:28 am
Forum: Technical Discussion
Topic: Cathodyne inverter as a balanced output?
Replies: 15
Views: 4815

Re: Cathodyne inverter as a balanced output?

FUCHSAUDIO wrote:How bout a single ended small output with 4-8-16 ohm connections. Ground the 8 ohm tap and take the output push pull off 16 and 0....now thats a cool little lo-Z drive... :)
That is a really brilliant idea, very good! I like that a lot.
by Ian444
Tue Aug 09, 2011 7:34 am
Forum: Technical Discussion
Topic: Cathodyne inverter as a balanced output?
Replies: 15
Views: 4815

Re: Cathodyne inverter as a balanced output?

600 ohms is a tough load, I forgot about that. Hmmm, give it a try without some sort of buffer/s, thats how we learn stuff. Or use a mosfet instead of the tube as a cathodyne, I've done that before.
by Ian444
Sun Aug 07, 2011 10:22 am
Forum: Technical Discussion
Topic: Cathodyne inverter as a balanced output?
Replies: 15
Views: 4815

Re: Cathodyne inverter as a balanced output?

The cathodyne needs equal loading top and bottom to stay balanced, so you could only do balanced out or unbalanced out, but not both at the same time, unless the unbalanced input you are driving has a really high input impedance. A mosfet source follower on each output from the cathodyne might be a ...