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Hi all,

Just joined up & just completed my first sIII build. Fired up OK on the first try (amazingly...). I do have a few questions though...

When I try to jump the channels, I get hum from the normal channel. It's perfect if I use that channel alone or the TMB channel alone.

The amp is very quiet while playing, even with the volumes dimed on the TMB channel, and it isn't bad even with the boost engaged. But, when I roll off the volume on the guitar to zero I get a lot more hiss. Any idea why?

And, my third and final (I hope!) question. I'm getting a strange effect when I push the output stage hard on either of the two channels (but it's worse on the TMB channel, probably due to the much higher gain). It's a high buzzy/sproingy sort of noise. Hard to describe really. It's most noticable on the lower notes (E & A strings mainly), especially bad on partially muted notes...they don't decay "cleanly". It almost sounds like something is overloading somewhere. Could it be a bad tube perhaps?

(edit: just swapped the EL84's and this problem is still there)

Overall, the amp sounds awesome, if a little bright when wound out but that may just be due to my cab (V30 loaded Avatar 2x12).

Thanks all.

Darrin

Congratulations on your build.



Havent sen this before but try the opposite jacks i.e. Hi Normal to Lo TMB channel and just check the grounds arent reversed in the jacks/jumper cable. Should work.


If the amp is dimed and you roll off the volume, you still have the amp on max. The carbon comp resistors do have inherrent hiss which can be reduced. there are resistors to change in the signal path to do this if you want but I think this sounds 'normal'.



This similar sort of thing sounds like it has happend to me and more than once. It was always a loose ground connection. We always assume that when an amp works, we did it right, but when I hear that sort of sound, I start looking for an unsoldered ground wire.
Do me a favor and check that every ground connection is soldered.

If it's in a combo, there is a whole raft of vibrations to track down.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Thanks man. Everything went smoothly with the build (you've seen the pics). The head cabinet you folks built for me should be here tomorrow.

I will re-check all the grounds. I have a feeling all these issues may be ground related. I probably won't get a chance to do that until late in the week though...unless we get another storm and my hockey is cancelled on Monday & Tuesday!

I'll let you know what I find.

Thanks,
Darrin

Storm, oh right, you're on the Rock. I know someone taking a March break holiday there right now. I guess she'll experience the real weather now! Talk about March Madness - Go to the Rock in March!

Yeah, check those grounds out.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Yeah - we got pounded this week. The storm on Monday was the worst in 6 years I hear. Nasty. Shut the whole freakin town down. That doesn't happen very often (believe it or not!). Mid-late Feb & early March are the worst of winter here.

I had a few minutes to give the amp a quick once over tonight. I did find one bad ground - the one going from the ground bar to the chassis. It was soldered, but I could slide it along the bar. I re-soldered it and now it's solid, and it did improve the tone of the amp a bit.

However, it didn't fix the problem with the odd buzzy noise when pushing the output stage. I've tried it with 4 guitars now (my SG, Strat & Godin LG sig and my friend's LP standard) with the same results. Tubes seem to make little or no difference. The only tube I haven't swapped is the recto, but I don't have an extra. I did find a couple of microphonic 12AX7's in my pile of spares though. Freakin garbage GT's...

When I get some more time I'll take a closer look at things. Maybe I'll even try to record a clip of the sound I'm hearing with the line out on my HotPlate & post it for you. I hope I can work this bug out because this amp is just kicking my butt. My SG through the TMB channel is crunch heaven...

Darrin

Well, you found one loose ground at least and you checked them all. Ii wont be the recto but could be another lose wire. If it really happens on both channels, check the wiring is solid to the Phase inverter, V3?

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Some more thoughts:
Noisey pre-amp tubes;
I know you used shielded cables;
Try a metal chassis cover over to shield the open bottom;
Try it in a different location - my shop is notoriously bad for this kind of stuff.
Try [carefully so as not to get electrocuted] physically touching wires with a chopstick while the amp is on to see just where the sensitive area is.
Sometimes carbon comps can go crazy. What type of ressitor did you use across V2 pins 1-6 . I'm using metal ones now as a precaution; not tha there have been problems.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I'll have a look at the connections on the PI tonight if I have time, and I'll re-check everything & re-flow the solder joins also when I get a chance.

And now that you mention location, I have moved it to my living room and for some reason the outlet I'm using there is very noisy - same with my Laney. I originally had the amp in the kitchen/dining room (where I built it) and I don't recall that problem when I first fired it up. I'll try it in another room. I really need a power conditioner...

Darrin