early Soldano Hot rod 50 heaters

[phsyconoodler]

I have an early Soldano Hot Rod 50 amp on the bench and the complaint is it 'hisses' loudly when using lots of gain and the master up.
  It indeed has a lot of gain on tap and doesn't use DC heaters for the preamp.
I think I'll install another transformer and convert the preamp to DC heaters,but I was wondering if anyone has experienced this amp and was it a common complaint with the early Soldano's?
  It has a HUGE amount of gain on tap.

[LooseChange]

>> It has a HUGE amount of gain on tap.

That's why it hisses.  I don't think the DC heaters will do a thing.
Switch some tubes around. If you can find a slightly lower gain12AX7, like the Sovtek branded ones, you may cut the hiss back a bit with really no noticeable change in gain.

[OldHouseScott]

You could try the back-to-back diode trick, like Peavey has in their Valveking. Check out D101 and D102 in this schematic. They will generate some crossover distortion, so you might want to have them only affect the dirty channel. In that case, inserting them immediately after the LDR coming off the plate of V2B would be a good location. You could try this trick without committing to it by creating an FX patch cable with the diodes in it.

Another trick to try (and simpler) is to put a cap from plate to cathode on V1A a la Marshall.

[phsyconoodler]

Hmmm...the cap trick is easiest.I'll try that first.Good call on the gain thing.The heaters are really not the issue,it's the gain.I should have clued in on that.
  Thanks guys!

[PRR]

Anyway: Heaters hum. Not hiss.

Change the first tube. Trim some treble. But basically: full-up is gonna hiss.

[dynaman1]

I've made about a half dozen Soldano-ish clones and every one of them hissed, in spite of using metal film resistors.

Heaters? Bah, tried DC too and it didn't make a lick of difference in hum. I don't even bother twisting anymore. Just finished this Soldano clone. No twist, no hum.

[LooseChange]

Don't mean to hijack but...

Damn Dynaman1, That's a nice piece of work!  Where'd you get the plans for that?

[dynaman1]

Don't mean to hijack but...

Damn Dynaman1, That's a nice piece of work!  Where'd you get the plans for that?

My feeble brain!

[phsyconoodler]

I like your feeble brain buddy!

  so care to share why yours doesn't hiss?
Damn!I get the terms mixed up.Humm.Hiss.Definitely different.
 
 I won't throw a hissy fit.Promise.

[dynaman1]

I like your feeble brain buddy!

  so care to share why yours doesn't hiss?
Damn!I get the terms mixed up.Humm.Hiss.Definitely different.
 
 I won't throw a hissy fit.Promise.

Beats me. Trial and error with the grounding has helped me keep hum down. I believe most Soldanos only have one ground point with the board serving as a ground plane for most of the components. Forgive me if my terminology is incorrect - my assembly skills are much better than my knowledge/theory.

I do mine differently. Safety is near cord inlet or PT. Input jacks, tone controls and all other pre-PI grounds contact the chassis near the input jack. All other grounds (I mean everything - PI, centertaps, output cathodes, OT common, bias supply) share a single point somewhere between input ground and safety. Seems to work for me. Three cascaded gain stages usually results in no hum with controls pegged and no guitar plugged in. Four gain stages might yield a bit of hum but the hiss is way more noticeable.

I've gotten into the habit of somewhat isolating the preamp grounds. Each pre filter cap shares a bit of buss wire with it's associated cathodes and grid ground references and has its own wire that snakes its way to the main pre ground point. When possible, a voltage divider between gain stages has its resistor grounded with the following stage. Probably unnecessary, but it's worked so far.

FWIW, I also elevate the heaters and use lots of shielded wire. Insurance, I guess.

I think layout probably has a lot to do with things. Seems that most high gain amps keep wiring as short as possible, so I locate my preamp tubes between the board and pots. I'm not sure why most folks still have long runs of wire feeding grids. In fact, I usually start my chassis layout by locating the first gain stage close enough to the input jack to negate the need for wire. Just a resistor from jack to tube socket. I don't mind using long wires for high voltage stuff like plates. I never run anything that's sensitive parallel with heavy current AC or high voltage stuff.

As far as twisting filament wires goes, well...I'm just too lazy for that stuff.

In spite of all my efforts, we've all heard quiet amps that had random grounds everywhere!!

[HotBluePlates]

That, Ladies and Gentlemen, is truly a work of art!!

Outstanding job, Dynaman. I mean really, really great job! I get the impression you took everything everyone ever said, sifted for the important stuff and went to work. Looks to me like a model of how to assemble a circuit.

[dynaman1]

That, Ladies and Gentlemen, is truly a work of art!!

Outstanding job, Dynaman. I mean really, really great job! I get the impression you took everything everyone ever said, sifted for the important stuff and went to work. Looks to me like a model of how to assemble a circuit.

Heh, thanks man. Must be an idiot savant thing, 'cause my bills, checkbook and life in general aren't nearly as well organized as my amps. In reality, the only things I've "sifted" through are countless mistakes and the only tips in this hobby I can offer are the results of painful lessons learned by wasted hours unsoldering stuff!

[TubeGeek]

I have to say that I agree!  What a great job! Thanks for sharing.

[simonallaway]

This forum is just like Playboy magazine. We all pretend we read it for the articles, but a glamorous picture like that can bring us all to our knees. 

[dynaman1]

You fellas are too kind and seem to have forgotten that I'm the guy that will post newbie questions like "Hey, what's neutral - white or black?" I'm just coloring by numbers......wasn't there a question about hiss somewhere in this thread?

[navdave]

Killer layout is that a Hammond box?

[The_Gaz]

Tis beautiful, Dynaman! ...but typical fixes for hiss are increased power rating on plate and grid load resistors (i.e. 1/2W -> 1W or higher), and as mentioned, reducing very high frequencies with plate bypass caps. It might be beneficial to try some "low noise" 12ax7s. I think JJ has some types that are advertised as such. But anyway, did you guys see that picture D-man posted!! 

[Shrapnel]

But anyway, did you guys see that picture D-man posted!! 

Yup, nice and clean. Obviously no fancy-schmaltzy multiple-channel rig layed out so that requires wires routed in all sorts of ways. Good layout 

[John]

I saved that picture to my hard drive. I hope the wife doesn't see it.

[dynaman1]

Killer layout is that a Hammond box?

Yep. 17"X10"X3".

Tis beautiful, Dynaman! ...but typical fixes for hiss are increased power rating on plate and grid load resistors (i.e. 1/2W -> 1W or higher), and as mentioned, reducing very high frequencies with plate bypass caps. It might be beneficial to try some "low noise" 12ax7s. I think JJ has some types that are advertised as such. But anyway, did you guys see that picture D-man posted!! 

Ahhh...maybe I'll step up to 1W resistors for the next build. Thanks for the tip. This amp does have the regular JJs. I've found that running four gain stages in a row rules out a lot of tube rolling. A questionable tube in the first stage will make the amp nearly unusable. In fact, I used an amp like this to weed out all the crappy vintage tubes I had. The names "Telefunken" or "Mullard" don't mean squat to me when they squeal or act microphonic. Lately, I've been using JJECC83s or Sovtek12AX7WAs. They've short plates and seem to be the most consistent. And they're cheap. I'd dare say the subtle tone differences among tube brands are noticed much when the sound coming out of the speakers is heavily clipped and distorted.

Hmm, maybe I should just put a piece of clear acrylic on the bottom, cuz the outside is pretty drab...I'm too cheap and lazy to even bother with lettering.

[eleventeen]

WOW, that's layout pr0n!

[phsyconoodler]

Hey! Where did you find those clear ckicken head knobs!!!!  Those are too cool!!
 

[John]

The more I read here, the more inferior I feel. Really cool!

[dynaman1]

Hey! Where did you find those clear ckicken head knobs!!!!  Those are too cool!!
 

Antique Electronics

[Rev D]

 Nice layout and thanks for the info on the chicken heads I was gonna ask as well, really like those. I dare say the amps are as nicely laid out as the old Hi-Watts and thats a high compliment but one I feel you deserve. Thanks for sharing.

Regards,

D.