Search found 1100 matches

by iknowjohnny
Mon Apr 14, 2014 7:14 pm
Forum: Technical Discussion
Topic: JCM 800 2204 Self oscillation problem
Replies: 18
Views: 4971

Re: JCM 800 2204 Self oscillation problem

Why not use a pot for NFB instead of a rotary? Simpler, cheaper, infinite control. I use a 220k with a 100k resistor in series with the pot off the 8 ohm tap. I also modded the pot so it's no load and at the end of it's travel where it's at minimum NFB it then goes to zero NFB.
by iknowjohnny
Tue Apr 08, 2014 5:35 pm
Forum: Technical Discussion
Topic: Do you have a voltage preference for cascaded preamps?
Replies: 0
Views: 1260

Do you have a voltage preference for cascaded preamps?

I know it's a very general question, but for those who build marshall style amps with a master and cascaded preamps to get most of thier OD in the pre, do you have a amount of voltage you tend to shoot for for the first couple stages? Just curious to see what others like and compare top my own prefe...
by iknowjohnny
Fri Apr 04, 2014 11:17 pm
Forum: Trainwreck Discussion
Topic: How much of a EL34 TW's tone...
Replies: 7
Views: 1634

Re: How much of a EL34 TW's tone...

I've done this and it became tighter overall, brighter, and I ended up biasing it much cooler, 28 mas, and it was a good sounding Express using JJ KT77s. Are you saying that biasing cooler makes a PA section with higher voltages on the plate sound more like one biased normally with lower voltage pl...
by iknowjohnny
Fri Apr 04, 2014 2:04 pm
Forum: Trainwreck Discussion
Topic: How much of a EL34 TW's tone...
Replies: 7
Views: 1634

How much of a EL34 TW's tone...

If at all would you say is due to having low plate voltages? from what I've seen they are probably 100 volts lower than the typical el34 marshall, no? (granted, I haven't spent much time looking at them but don't they hover in the mid to high 300V range?
by iknowjohnny
Sun Mar 30, 2014 7:11 pm
Forum: Technical Discussion
Topic: 1/4 watt plate R
Replies: 6
Views: 787

Re: 1/4 watt plate R

Ok, thanks. Guess i'll just do the old back and fourth swap.
by iknowjohnny
Sun Mar 30, 2014 2:41 pm
Forum: Technical Discussion
Topic: 1/4 watt plate R
Replies: 6
Views: 787

1/4 watt plate R

I want to temporarily put a 100k pot in place of the plate resistor on a gain stage with the wiper to the coupling cap to decide what resistor values i need to get the amount of gain i want for a split load setup. But i see the pots i have and most all common pots are listed as 1/4 watt. Is this doa...
by iknowjohnny
Sun Mar 23, 2014 3:42 pm
Forum: Technical Discussion
Topic: Question about touch responsive amplifier design
Replies: 46
Views: 9524

Re: Question about touch responsive amplifier design

I find that too. (dynamics make an acoustic) I had a larrivee that lists for $3k and i now own a $350 recording kind i much prefer ! The reason: dynamics. There are lots of great sounding cheap acoustics today, but what people don't get is they can sound fantastic, even as good or close to some high...
by iknowjohnny
Sat Mar 22, 2014 1:43 pm
Forum: Technical Discussion
Topic: Question about touch responsive amplifier design
Replies: 46
Views: 9524

Re: Question about touch responsive amplifier design

Also so many players that have been using amps that are rather flat dynamic wise they don't seem to recognize or respond to what the amp is (instrument) is doing.. I've lent amps to amateur friends here, or tried to lend them, most are used to SS or some sort of Valvestate stuff. My amps, all tweed...
by iknowjohnny
Thu Mar 20, 2014 7:01 pm
Forum: Technical Discussion
Topic: 1/2 watt ok?
Replies: 4
Views: 1199

Re: 1/2 watt ok?

Thanks. I normally use 1w because the leads are much thicker, but i needed a value i didn't have in a 1w. I will replace it next time i order resistors, thanks.
by iknowjohnny
Thu Mar 20, 2014 3:04 pm
Forum: Technical Discussion
Topic: 1/2 watt ok?
Replies: 4
Views: 1199

1/2 watt ok?

For 12AX7 plate resistors on a 300V PI?
by iknowjohnny
Thu Mar 20, 2014 2:27 am
Forum: Technical Discussion
Topic: RCH us made tubes?
Replies: 52
Views: 11653

Re: RCH us made tubes?

I'd only support the idea if the warranty were exceptional. $200 is far too much for a tube that shorts or goes microphonic etc after even a couple years least alone a few months as tubes often do. On the other hand i can't imagine how they could support such a warranty unless they know something ab...
by iknowjohnny
Mon Mar 17, 2014 3:49 pm
Forum: Technical Discussion
Topic: What basic specs for a BIAS pot
Replies: 16
Views: 2182

Re: What basic specs for a BIAS pot

IKJ, You answered your own question. It also affects the tone. Well, what i meant to ask is why they do this on areas where it's NOT a reliability issue as with a bias pot. You say tone? Like with the bass pot in a marshall? Can you clarify how that affects the tone? I could see how it might affect...
by iknowjohnny
Mon Mar 17, 2014 1:37 pm
Forum: Technical Discussion
Topic: What basic specs for a BIAS pot
Replies: 16
Views: 2182

Re: What basic specs for a BIAS pot

On a side note, why jumper the wiper and one outer lug? I see that done all the time, but why? I just use the wiper and whichever lug i want depending on direction. Other than that i don't understand why some pots uses as a VR use that other outer lug with the wiper. I understand that with a bias po...
by iknowjohnny
Sat Mar 15, 2014 7:06 pm
Forum: Technical Discussion
Topic: power tube grid stoppers
Replies: 6
Views: 1443

Re: power tube grid stoppers

Just tried 15k and i didn't hear any difference ! I was actually hoping for a darker tone but i didn't get anything. Odd !
by iknowjohnny
Sat Mar 15, 2014 3:19 pm
Forum: Technical Discussion
Topic: power tube grid stoppers
Replies: 6
Views: 1443

Re: power tube grid stoppers

Thanks. I never noticed buzziness in the pre with big GS's, but I guess it depends on other factors.