Blue Voodoo BV120h noise issues

[axpro]

Hey guys,

I just got a BV120H, I am mostly out of the amp building.modding game... after years of having a collection of "never done" amps, I decided to just play what i have.

Anyways, I got a BV120H, it's not too bad, just a little hissy in the gain channel. it's got 5 gain stages in that channel, so noise is to be expected. Just wondering if anyone has gotten the hiss tamed a bit on thsi channel. Losing some of the gain is fine, it's got more than i need. was considering using spiral filament tubes, or trying a 12at7 to cut down the gain a bit, and hopefully the noise.

trying to find an accurate schematic, I figure the BV60 is close.

[mooreamps]

you would have to convert the first gain stage from self bias to fixed bias to dump the hiss..

-g

[axpro]

I've never used a fixed bias stage in a preamp, most of my amp building/modding years were simple stuff, vintage recreations and the like. Never got in much with boutique building styles. Somehow i think it's a more complicated mod than I am wanting for this amp.

Just to clear things up, I am not looking to do a rewire or anything too detailed. Switching out a few cathode resistors/ adding a little more filtering, switching in some better parts is cool, but I don't want to get too crazy with a PCB amp as far as heavy changes go.

[mooreamps]

It's not complicated... On the first gain stage, pull the cathode resistor. Replace it with a yellow led. Then, pull the plate coupling cap, and replace it with 4.7 nF cap. . .

-g

[axpro]

To be honest I have NEVER heard of doing that lol.... Guess I'll keep researching...

[mooreamps]

To be honest I have NEVER heard of doing that lol.... Guess I'll keep researching...

then you will never dump your hiss problem. . .:|

-g

[axpro]

I'll never dump my hissing problem because i need to research fixed bias preamp design?

Been hanging out here since the original ampage forum was "new" and have never had anyone say that there is only 1 way to mod something, and have never been told the not having the research done yet meant never having a chance of fixing something.

When i did a search for "mooreamps" i see a lot of negative angry vitriol... guess I'll work on it myself.

[Jazz P Bass]

Crate BV120H Schematic

I would think the 12AT7 less gain mod is worth a try.
Here are the schematics.

[axpro]

lol, good idea Jazz!

I had just found the schematic and was thinking the same sort of thing. I tried an at7 in V2, since it is what handles the gain channel, I ended up turning the gain up slightly, like a quarter turn, but it did tame some of that channel for me. I might try altering the slope resistor for the gain channel and maybe reducing the gain of the first V2 stage, perhaps changing the value of the cathode bypass to something a little higher, or even pulling it alltogether

I have had luck using spiral filament tubes in the past to get rid of a little noise. I think I have a 5751 at work i could sub into the first stage that wouldn't affect the clean channel too too much, but would kick the gain channel back a little notch too.

[axpro]

I might add that it currently seems mostly loaded with GT12ax7C's My memory being a little iffy, I remember these being higher on the ole gain index as well.

[axpro]

Tried the 12at7 in the first position, the clean tone was a little less harsh, but the tube itself is NOT happy there, lots of pinging. DIdn't seem to notice any microphonic issues in V2, but in V1, it's bad, sadly most of my amp building/modding supplies are at work, so I'll have to wait until tomorrow to get into any other tube swaps or component changes. I think i have some Sozo caps in my parts bin, maybe i'll change some of the filter caps. I don't want to get too deep into it though. It's pretty usable with the at7 in V2, I'll see what i have hanging around for lower gain tubes in the shop. maybe a pair of 5751's for V1/V2 will make the clean channel a little softer AND reduce the gain a bit on the gain channel, without having to get my soldering iron hot at all!

[axpro]

So, a quick update.

Switched out the first preamp tube (stage 1 universal, stage 2 clean) with a Groove tubes ECC83s shortplate, and the cleans are a little less sterile. I really think a 5751 would work nicely here.

Put an old stock Westinghouse 12au7 in the position 2 tube (stage 2-3 of the gain channel) which REALLY hamstrings the gain level in this thing. but in a good way. With a 12ax7 it had WAY too much gain still, and when i tried a 12at7 it STILL had too much gain and hiss. the 12au7 has really backed off those 2 stages. This thing DOES have 5 gain stages for the dirty channel, so I am really messing with the designed gain structure, but truth be told, with the gain at max now, it has a touch more grit than it did with the gain at 5 before, but without the fizzyness. It works PERFECTLY for me. Even with an EMG equipped guitar, the gain channel was WAY WAY too noisy before. now it has a faint hiss, but the gain level maxes out just above JCM800 level. I find it easier to dail in different levels of gain, since now I can dial in from 1-10 and before i could go from 1-4 or 4 1/2


My only question now is the validity of using a 12au7 in a marshall/soldano styled preamp. I wouldn't think it could hurt anything, BUT, famous last words.......

[R.G.]

I'll never dump my hissing problem because i need to research fixed bias preamp design?
...
guess I'll work on it myself.

You are indeed wise beyond your years - however many years that is.