QuoteI'm planning another battery based kit, probably power amp only.  This one would be based on the PAM8302 which gives 2.5w and runs on a really low voltage of 5v nominal.

Looking forward to this one.  2.5w is about all I'd need with a speaker.  Consider a basic preamp board to go with it.  Thanks again!

I just built mine over the weekend, and I want to start by saying "thanks" for adding a project to all the conversations and information on the forum.  This is a good way to bring it all together and stimulate more discussion.

Next, stuff I like: Excellent board, quality components...real pro stuff and I appreciate that. The distortion sound is smoother than I expected, especially on the higher-gain end of the tone range. The tone control mellows out any fizziness which could be a problem depending on your guitar/headphones/speaker.

And, my criticisms: Too much distortion, and not enough volume with the gain turned down to the edge of breakup.  I'll modify it to the clean buffer preamp option one of these days. No power switch, but I can understand the omission, since this is supposed to be highly customizable. I have to pop the battery connectors to power down, but my enclosure choice makes that easy enough. Finally, what can you say about the lack of volume from a LM386 that hasn't been said before?  I'm running two 9v in series for +18-ish volts, and this is sufficient for headphones, but just.  I haven't tried a speaker yet.

That's my experience, and I look forward to more SSGuitar projects and discussions!

I like having the headphone out, but I'd like to see some provision for variation of supply voltage.  Maybe two 9v batts for an 18v circuit and more headroom, or two 9v in parallel for more current or longer battery life.  I vote "other".

I never worried about it either, until I was testing a 2X12 cabinet the other day with two speakers that had some serious bass response (Fane A60s).  That pop was loud, and I feared for the drivers.  Maybe just an annoyance, but better equipment is quieter, no?  I'll try the power lead trick and see where that leads me.

My Fender Champion 110 pops when I shut off the power switch.  I find the same problem, but louder, in the Frontman 15R we use as a bench amp in the guitar shop I work at.  I think the amps are pretty similar, so I think the same fix should work on both.  SO...what's the fix?  We used to cut switching noise by adding a cap across the contacts but I don't remember the value of the cap and I'm not sure the problem is the same (this was a remote switch for a broadcast turntable which was generating a spike that the preamp picked up).

Seems like this symptom is common with solid state amps.

Thanks for the ideas.

Great history lesson.  I always get suspicious when someone says their device sounds more "musical".  What electrical parameter defines musicality, exactly?  I'll give this thing it's cool factor, however.  It would look pretty good on my Elliot P27 board, but Rod would have me shot for using it.

 
My impression of Orange was that they didn't much care about their solid state offerings, anyway, compared to their tube amps.  I seem to remember a previous post about their under-designed heat sinking, etc.  A module like this takes some r&d.  Must be some money to be made somewhere.

OK, who wants to start the discussion on this baby?

https://orangeamps.com/shop/components/op-amp/

I guess there are other similar modules out there.  This one sure is expensive, compared to the chips it replaces.  Besides bragging rights, what do we get for our money?

Yes, soldering is no problem, but the desoldering was another story...the pads & traces came up like cheap paint on waxed paper.  A new board is in the works.

Thanks for the review of grid leak bias; the DC present at the tube input probably accounts for the scratchy pots I noticed.  Converting old PA amps for guitar of harp duty is kind of a "thing" around here.  A local guy (Skip Simmons) has made a name for himself doing that, in addition to the hot-rod mods he does on old Fender stuff.  He declined to work on this amp due to its pcb construction, and when you try to desolder components from that 60-year-old board, you'll get his point!  Here's a schematic:

Thanks for your interest.  I always feel like one of the big kids when Sr. Fahey replies to my posts.

This amp has nothing so fancy as a "real" phono input...it just provides an RCA jack feeding the second amplifier stage, no eq network, just a 500k pot and a 470k isolation resistor.  "Phono" probably refers to a ceramic phonograph cartridge with a big output level.  In broadcast use, I might have connected a radio tuner to provide audio at a remote location, mixed with the local mic.  Should be pretty forgiving of level and impedance.  I could post a schematic if there's interest, but this thing is pretty primitive.

Curiouser and curiouser!  I've not heard of this issue from the other PA-head aficionados, but there you are.  If this rig were used as intended, with a (hi-z) microphone as the input, there would be no problem, since those devices don't have pots.  This shouldn't be a problem if I use an external preamp through the phono (line) input or just a pedal ahead of one of the mic inputs.  Thanks for the analysis.

Blocking cap is a good idea.  The amp is down & out now, so no testing is possible, but I'll measure for DC when the new board gets fabricated.  My main thrust is, can an input impedance be too high?  I thought higher is better, to be blunt.  4.7meg isn't very high, compared to acoustic (piezo pickup) input stages that run 10meg or so.  As you might expect, when I run through a pedal the scratchy pots are just fine.

I've been working on an old Stromberg-Carlson PA amp hoping to get some tube mojo to drive with my (also in-progress) Elliot preamp.  When I get the PCB done, I think it'll be fine, but I've noticed that my guitar's volume controls are awfully noisy when I plug directly into the mic inputs. According to the schematic, the input preamp is a 12AX7, running grounded grid (nothin' fancy here) with a 4.7megohm grid resistor.  Somewhere in the back of my mind I remember seeing where too HIGH of an input impedance can give you that "scratchy pot" problem.  The problem is worse with my humbucker pickup guitar, better with my Tele-clone.  Am I mis-remembering something, or is there a problem with the amp I'm missing?  And, why would the input z make a difference?  I thought input impedance had more to do with frequency response by loading of the pickup.

I wondered if the amp might be a little low-powered.  So the idea is to bridge the outputs of two LM3886?  What speaker did you get with yours?