Search found 914 matches
- Tue Apr 23, 2019 1:25 pm
- Forum: Technical Discussion
- Topic: First Stage Hiss
- Replies: 15
- Views: 2266
Re: First Stage Hiss
It's been awhile. Been busy. Anyway, Martin - no DC on that pot. I replaced it to no effect. RG - I'm pretty sure I did replace the coupling cap, but I'll make sure. This is so frustrating because the first one I built is dead silent with nothing plugged in to it, even with all the knobs dimed. Can'...
- Mon Feb 25, 2019 10:46 am
- Forum: Technical Discussion
- Topic: First Stage Hiss
- Replies: 15
- Views: 2266
Re: First Stage Hiss
R.G. - I routed the Csnub to ground and added a 0.1uF across the 1m input ground. There's still some hiss but Way less. It's not as quiet as #1 but I think I just lucked out somehow with that one. I'm going to see if I can borrow it back for some more in depth study; try to figure out what my secret...
- Sun Feb 24, 2019 6:24 am
- Forum: Technical Discussion
- Topic: First Stage Hiss
- Replies: 15
- Views: 2266
Re: First Stage Hiss
Here are a couple of pics of #1. One pic is earlier on in the build, the other is the final as noted in the pics.
- Sun Feb 24, 2019 5:55 am
- Forum: Technical Discussion
- Topic: First Stage Hiss
- Replies: 15
- Views: 2266
Re: First Stage Hiss
xtian - The 100k anode resistors are indeed metal film, Vishay Dale to be specific. I'm waiting for a 10k to try on the input grid. I did try another, I think it's metal oxide. If there's any difference it's only that the hiss is smoother but I can't guarantee that - maybe just hoping. Malcolm - Yes...
- Sat Feb 23, 2019 5:27 am
- Forum: Technical Discussion
- Topic: First Stage Hiss
- Replies: 15
- Views: 2266
Re: First Stage Hiss
I use 1w throughout, but no metal film. I give it a try.
Thanks!
Thanks!
- Fri Feb 22, 2019 7:19 am
- Forum: Technical Discussion
- Topic: First Stage Hiss
- Replies: 15
- Views: 2266
First Stage Hiss
I built another 50 watt amp, sort of a Marshall 2204 with a Bunch of mods. The first one I built is amazing - guess I lucked out. It sounds really nice but what's really special to me is that with no guitar plugged in you can dime everything and it makes NO noise. Ok, a tiny bit of air sound, like s...
- Mon Jan 28, 2019 4:07 am
- Forum: Technical Discussion
- Topic: Bias Blues
- Replies: 32
- Views: 2976
Re: Bias Blues
Thank you Soo much, Martin! I got it biased a little on the cool side and after a bit of tweaking on the 1st two stages it sound Great! And thanks to everyone. Once again with all the help from you guys what looked like a disaster turned into a success! Plus, I have some really interesting stuff to ...
- Sun Jan 27, 2019 4:57 pm
- Forum: Technical Discussion
- Topic: Bias Blues
- Replies: 32
- Views: 2976
Re: Bias Blues
The Classictone 40-18015 has no CT. So, although I see and understand using voltage control inline with the main HT, could a Zener be used between the "back" of the rectifier bridge and the ground?
- Sun Jan 27, 2019 2:21 am
- Forum: Technical Discussion
- Topic: Bias Blues
- Replies: 32
- Views: 2976
Re: Bias Blues
Sorry, didn't get to finish that last post. I get a fairly steady 120v from the wall sockets. The 470v main I quoted was with so EL34s in it because before I fixed the Bias resistor I saw the 5881s (Tung Sol, incidentally) get a Tiny bit of red plating going on and turned it off IMMEDIATELY, of cour...
- Sat Jan 26, 2019 4:57 am
- Forum: Technical Discussion
- Topic: Bias Blues
- Replies: 32
- Views: 2976
- Fri Jan 25, 2019 2:32 am
- Forum: Technical Discussion
- Topic: Bias Blues
- Replies: 32
- Views: 2976
Re: Bias Blues
Okay I FINALLY got logged in. The system rejected me since my first post. That's why I haven't replied. Thank all you guys for your answers. First, I replaced the mistaken 220K resistor with a 1.5K. MUCH better! So yes to 9000 +ones. However, this amp has some other issues that I am working out now ...
- Sun Jan 20, 2019 8:40 pm
- Forum: Technical Discussion
- Topic: Bias Blues
- Replies: 32
- Views: 2976
Bias Blues
This amp was meant to use 5881 power tubes. The PT is a Classictone 40-18015. The mains are 300v @ 200ma, 6.3 @ 3.75a and 39v @ 3.5ma for bias. I wired it up exactly as I have several others with minor tweaks for the power tubes, etc. The bias circuit looks like this. But there are 0 volts coming fr...
- Sun Dec 30, 2018 5:47 pm
- Forum: Technical Discussion
- Topic: Synthesizing a PT center tap
- Replies: 1
- Views: 411
Re: Synthesizing a PT center tap
Okay, I just saw that the 40-18015 has a 39v bias winding. (duh)
Problem solved.
Problem solved.
- Sun Dec 30, 2018 5:23 pm
- Forum: Technical Discussion
- Topic: Synthesizing a PT center tap
- Replies: 1
- Views: 411
Synthesizing a PT center tap
I have a transformer with no center tap. It's a Classictone 40-18015 - 300v, 200ma. So I'm trying to set up bias voltage. Unfortunately, using a rectifier bridge yields too much voltage; my power tubes are 5881 and even if I used other tubes the OT is only 40w. A couple of diodes would work fine for...
- Thu Jun 07, 2018 6:13 pm
- Forum: Technical Discussion
- Topic: Is a PT secondary center tap a must?
- Replies: 10
- Views: 3071
Re: Is a PT secondary center tap a must?
Hey, keeps us coming back, eh? Frequent checks of this place could never be a bad thing.