Search found 821 matches

by jontheid
Sun Apr 18, 2010 8:49 pm
Forum: Technical
Topic: OR120 headroom.. thoughts.
Replies: 35
Views: 10081

Re: OR120 headroom.. thoughts.

Further to the above, plate voltage at idle is not greatly affected by varying the plate current at idle (i.e. adjusting the bias point). This is because the output transformers' primary winding (of which on side is connected to the output plates and the other to the b+ supply) has a low d.c. resist...
by jontheid
Sun Apr 18, 2010 12:52 pm
Forum: Technical
Topic: OR120 headroom.. thoughts.
Replies: 35
Views: 10081

Re: OR120 headroom.. thoughts.

Hotter bias equates to more power dissipated by the tube at idle (i.e. nothing being played on the instrument / no signal input) Colder bias equates to less power dissipated by the tube at idle. Things can get confusing using terms like 'increasing' and 'decreasing' the bias, as some people consider...
by jontheid
Sat Apr 17, 2010 9:44 am
Forum: Technical
Topic: OR120 headroom.. thoughts.
Replies: 35
Views: 10081

Re: OR120 headroom.. thoughts.

Bias the amp hot to get more clean headroom - the hotter the bias, the less crossover distortion at higher volumes. You quote 35ma as your bias current, but this means nothing if you don't tell us your plate voltage. What brand KT77s are you using? I use my head for bass (it is an Orange Super Bass)...
by jontheid
Sat Mar 13, 2010 2:59 pm
Forum: Technical
Topic: Feedback tap?
Replies: 6
Views: 1797

Re: Feedback tap?

It forms a negative feedback loop between the output of the amplifier and a point earlier on in the signal path. On Orange amps that use a cathodyne (split-load) phase inverter this point is at the top of the cathode resistor of the tube before the phase inverter. All the vintage Orange amps use thi...
by jontheid
Fri Mar 12, 2010 6:57 pm
Forum: Community Discussion
Topic: Faceless Rock
Replies: 20
Views: 2083

Re: Faceless Rock

I think we're entering a period again where some "next new thing" is needed to wipe out the crap that is presently being passed off as music. American Idol has all the commercial pop/rock sounding like the same guy band or girl singer....and hip hop/rap has played itself out and become a parody of ...
by jontheid
Fri Mar 12, 2010 6:17 pm
Forum: Community Discussion
Topic: Bass Terror 500w Head
Replies: 19
Views: 1934

Re: Bass Terror 500w Head

I was really interested in getting one of these - I was walking down Denmark St one day and saw one of the shops had these in stock so I gave it a long demo. It was alright, but I didn't fall in love with it. Kind of hard to explain really, but the cleans didn't seem too magical and the amp seemed t...
by jontheid
Fri Mar 12, 2010 7:56 am
Forum: Community Discussion
Topic: Your Favorite Big, thick, powerful EL34, if you please.
Replies: 59
Views: 5620

Re: Your Favorite Big, thick, powerful EL34, if you please.

It's easy to think that EL34 and 6CA7 are the same valve because so many on ebay and the like will state 'EL34/6CA7' when describing valves. I thought they were the same thing for ages, too. To further confuse matters, Sylvania made 6CA7s that were actually labelled '6CA7 EL34'. To make things even ...
by jontheid
Thu Mar 11, 2010 7:25 pm
Forum: Community Discussion
Topic: Your Favorite Big, thick, powerful EL34, if you please.
Replies: 59
Views: 5620

Re: Your Favorite Big, thick, powerful EL34, if you please.

EL34 and 6CA7 are not the same. EL34 is a pentode valve, 6CA7 is a beam-tetrode valve. Electro-harmonix are, I believe, the only current manufacturers of 6CA7s. Here's a link http://www.ehx.com/products/6ca7 They are supposed to be interchangeable with EL34s. I have not found this to be the case in ...
by jontheid
Thu Mar 11, 2010 6:58 pm
Forum: Community Discussion
Topic: kt77 or el34 in an or120?
Replies: 15
Views: 1002

Re: kt77 or el34 in an or120?

Further to my post above: I am using reissue Genalex KT77s, just in case there was any doubt. A question for AIRBURST . What country are you in, and what is the voltage selector on the back plate of the amp set to? I know this might sound like a ridiculous question, but if the voltage selector is se...
by jontheid
Thu Mar 11, 2010 6:52 pm
Forum: Community Discussion
Topic: kt77 or el34 in an or120?
Replies: 15
Views: 1002

Re: kt77 or el34 in an or120?

Hi all, I've tried Genalex KT77s in my 1979 Orange Super Bass (very similar design to OR120 with a few bass-specific bells and whistles) and I didn't get very good results at all. The sound was ok but lacked volume overall. I scoped the output with a dummy load and found I was only getting 100W outp...
by jontheid
Sat Nov 08, 2008 4:32 pm
Forum: Technical
Topic: SuperBass:the missing link or a Frankenstein?
Replies: 5
Views: 1959

Hi there . . . I have a 1979 Super Bass head with working contour switch, I'll try to get the values off it for you. The rest of the schematic is pretty much like earlier graphics - 74 I suppose. The one thing that seemed to be different on mine is the phase inverter plate resistor was way high and ...