Asteroid hissing in first stage?

[bnwitt]

Thanks rhubarb999,
By the way, there isn't any swirling, I think my use of the word swoosh was misleading. It is only hiss that, as you say, is minimal on slow but much stronger on fast. That just means it's there at a constant level in stage 1 and when you attenuate the signal from V1b through the 82k resistor before it goes on to V2b you can't hear it as well because of the reduced level.

I think we may have the same thing. I am beginning to believe it is the nature of this first stage to have the tube hiss. I'm an old Fender guy and haven't built that many Marshalls, but it seems that this .68uf/2k7 cathode combo with the 100k plate resistor has a high enough gain that it makes normal tube hiss audible. Today, I'm going to change it to a 22uf/1k5 Fender style R/C and see what happens to the hiss and gain. I've been doing some surfing on high gain Marshall, Slodano, Mesa amp sites and it seems hiss is an accepted side effect of those high gain amps. I'm just used to dead quiet Fender amps and I find extemporaneous noise irritating. I do love the gain and crunch of this amp however.

I would appreciate anyone out there who has one of these amps to check their's again for this hiss since I might just be chasing my tail here.

[mlp-mx6]

Though not *exactly* the same thing, I built a Wreck-style circuit into a Fender Blues Jr. for a friend. I have to admit, that circuit is so much FUN to play! Now I MUST build one for myself. And the 15W or so of 2 EL84s is just about right. Much louder and it would be much harder to find appropriate venues where I could actually use it. (FYI, the power supply in the Blues Jr. is not sufficient. I think the power xfmr needs to be able to deliver just a bit more current...)

I also LOVE the clean tone when I turn the guitar down. Just gorgeous!

Anyway, I have the same dislike for the hiss that is SO apparent. Just can't get used to it, and the guy who I built it for plans to use it (some) for recording, so I don't think he will like the hiss either!

I'm wanting to try some of the Dale RN65 plate resistors, hoping that they'll be a little quieter than the 1W carbon films that I have in there now. Have you tried different types of resistors? My understanding is that most hiss is some kind of thermal noise, and mostly from the plate resistors. I have to think that the cathode resistors are passing the same current, so they add some hiss as well, but not as much as the (generally) 67x larger plate resistors. Like you, I am much more accustomed to less hiss - but this includes the Dumble circuit amps I have built, which have less hiss in OD mode (with 4 gain stages, and a LOT more series resistors) than this little mini-Wreck. I'm hoping that those resistors will be quieter, but still have the tone and response that makes me reluctant to return the amp.

[bnwitt]

Ok, I have come to the conclusion that I'm being retentive with the hiss. It is present, but only when cranked and even then it is minimal and can't be heard when playing. I finished the cabinet today and popped the chassis in there, set her on the 4X12 Vintage 30 cabinet and played it for about 30 minutes. I really love the harmonics of this amp, the controlled feedback you can get by setting guitar and amp tone controls. This amp is quite amazing. I wish I was a better player Anyway, here is a picture of the finished head.

[Allynmey]

Looks nice Barry, Congrats!

[bnwitt]

Looks nice Barry, Congrats!

All thanks to your guidance my friend. This is a very sweet machine.