blowing fuses

[UNCLEDUB]

Sounds good. Now we just have to decide on what speakers to go with.

Thanks again for all of the help.

[passfan]

Don't forget to try 12AT7's, 12AY7's, and 12AU7's as well. You can tone it down a bit with these other ones in any spot.

[UNCLEDUB]

I'll keep that in mind. He is coming over today to check it out and we will talk about what options we have. it sounds good and really loud, like really LOUD. I'm sure some better tubes and a nice cab will help a lot with some of the loose feel to it... or it could just be my shotty playing. I'll find out today when my buddy gets here.

The only two issues I have are the louder than normal hiss and the presence pot is pretty noisy. I'm about to hit the forum and see what I can find out to tame the beast.

Thanks again for the hospitality and when I get the studio back up and running I'll try to post some pics and sound clips of the finnished product.

[UNCLEDUB]

Hey guys, so I have been busy working on the speaker cab over the past couple of weeks and clearing my brain of the TW. It's time to get back at it now that I have the cab built and the speakers in. I haven't been able to stop the hiss at all... if anything I may have made it worse.

Hear is what I can tell you:

There is a hiss and a hum. The hum stops when you touch the bright switch (grounding issue?). The hiss gets louder as the gain turns up and when the treble is dimed out. Mid and Bass don't change the hiss. Presence pot is scratchy and makes the hiss worse once it gets about 3/4 of the way up. Do you guys know of any alternative grounding schems that may help with?

Other than that the amp sounds amazing. We went with two tone tubby 10s in a semi open back cab. The cab sounds amazing compared to the ones we tried at the local music store, which included a Marshall 1960a, an Emenince 112 cab, and one other that I can't remember. The Marshall sounded the best out of the three but the two tone tubbys were a shock when I heard them.

Thanks again for all of the help

[UNCLEDUB]

Hey guys, it's been a while sence I posted. Progress on the amp has been slow. I have a loud hiss that I can't get rid of. I was checking voltages and when I touched pin 2 or pin 7 of V3 the hiss almost dead quite. I have changed my grounding to the astroid schem. I was also able to hook it up to a scope for a short while and we found some ripple across the first two 40uF caps. I don't have a scope and I didn't have the time to really poke around with it. I really think my problem could be around the PI seeing as how it stopped when messing around there with the DMM. Any help would be awesome. Thanks again.

CW

[Structo]

Hiss is fairly common with these amps due to the high gain.
You can use a lower gain tube in V1 or the PI.

Also, if you have a bunch of 12ax7's try them all in V1, sometimes you can find one that has much lower hiss.

As for the ripple, usually in a push/ pull amp that will balance out any hum on the plates.
But if you have hum in the preamp, it will amplify it.

Could be bad caps or grounding there.

The presence pot will be scratchy as it has some DC voltage on it.
It is a common complaint with that design.

[UNCLEDUB]

Thanks Structo.

That is what I suspected for the ripple across the caps. I have checked and rechecked the grounding so I'm going to replace the caps and see if that helps.

I know that there is a lot of hiss but you can hear the hiss over the guitar so i'm thinking that is a bit more than normal. I don't expect the amp to be dead silent but this is enough hiss to make me suspect that something isn't right.

I am also going to order some new tubes b/c all I have now are JJs. So if you guys have any suggestions on what and where to get them that would be great. I am thinking of going with a low gain tube in V1 but I would love to fix some of the hiss with out changing tubes.

Thanks again

[Big Jim]

+1 on what Tom said about preamp tubes. My Express had a lot of the same issues early on. Once my amp proved stable, I dropped in some Siemens power tubes and experimented with an assortment of preamp tubes. I wound up with all NOS Sylvanias. yellow label 12AX7 in V2&3. I found that a JAN 5751 green label in V1 really helped my amp settle down and clean up.
Jim

[Cliff Schecht]

I may try a 5751 in V1 soon, I just found a few in one of my stashes. The Amperex 7025 I have in there now is the only tube I have that works in that position and I'm hoping to not wear it out too quickly. I think the amount of material I cover would benefit from a slightly cleaner clean too .

[Big Jim]

I may try a 5751 in V1 soon, I just found a few in one of my stashes. The Amperex 7025 I have in there now is the only tube I have that works in that position and I'm hoping to not wear it out too quickly. I think the amount of material I cover would benefit from a slightly cleaner clean too .

I really like the 5751. I believe it's about 70% as much gain as a 12AX7. I noticed a decrease in hiss (could have just been a low noise tube), and my Express just kind of balanced out and seemed smoother. I'm sure everyones wreck is different. I did read a thread where Glen was using 12AU7 in V1 to do some country session work. The beauty of a circuit that responds to tube changes
Jim

[UNCLEDUB]

Thanks for the help guys. I'll keep the tube sugestions in mind. I don't have a huge stash of tubes so hopefully i'll get one that will work with out having to order a bunch. Guess it's time to start collecting tubes...