Recent Posts

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Tube Amp Building - Tweaks - Repairs / Re: 20W single ended 1x12 combo with trem and reverb

« Last post by mistersnitz on April 17, 2026, 10:02:56 am »

Finally got this thing built and tested properly. Some tweaks needed here and there and a reverb driver tube to replace but overall really happy with the outcome. I was surprised by the absence of hum with the chassis just sitting on the speaker cab in our rehearsal space with no shielding (unless you crank everything almost wide open)

Next steps are balance tweaks between the selectable tone stacks, replacing the 12AT7 that died due to a cold solder on one cathode pin of the reverb driver and resolve some thumping of the trem circuit

Oh and getting started on the combo cabinet!

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Other Topics / Re: Meme of the day

« Last post by shooter on April 17, 2026, 08:38:29 am »

...

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Tube Amp Building - Tweaks - Repairs / Re: Princeton Reverb circuit refinements

« Last post by tristanc on April 16, 2026, 04:32:14 pm »

After spending many many hours troubleshooting hum on my build, I replaced the reverb recovery cathode bypass cap with a 220u. C9 on your schematic. Dead silent! (Thanks Stratomaster). Now I do that mod in all reverb circuits. The part is dirt cheap. Just add it to your order "in case"    ;-)

I’ve a 100u in my stash of random parts ready and waiting!

I think there will be a few components tacked in for the 1st power on, to get a rough picture of the voltages. I was targeting the values on the original Fender schematic, but I’m also conscious the reissue (which people seem to like) varies a bit from those. As I have it drawn, I end up with a 1st stage B+ of 275 (E). The PI and 3rd stage + reverb recover at 290 (D) and the reverb driver at 340.

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Tube Amp Building - Tweaks - Repairs / Re: Princeton Reverb circuit refinements

« Last post by tristanc on April 16, 2026, 11:03:16 am »

Thanks - funnily enough I’ve been going through ratings just now. Most power rail ones are 3W, and the kit I’ve used uses mostly 1W elsewhere.

But worth doing a check and I’ll also update the schematic with ratings.

And yes, I’m making use of the cap can as a ‘mega cap’ as the returns of A, B and A’ (power valve, screens and LFO) all return to its shared cathode anyway. Rather than replace it.

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Tube Amp Building - Tweaks - Repairs / Re: Tips for building a super small, compact, gigable, lite, combo?

« Last post by johnnyreece on April 16, 2026, 10:28:32 am »

Weber has really decent stainless steel chassis in the close out area every now and then. There’s a Marshall JTM chassis there for $45 currently.

https://www.tedweber.com/6m50ch/

Just sayin’

Small nitpick - I believe that chassis is for an 18w with triple the power section (6 x EL84).  I'm currently trying to squeeze a SLO-style circuit in one, so that's why this stuck out to me.  The 6M45 chassis is the JTM.  The Marshall-type chassis are also aluminum.  The Fender style are stainless and have screenprinting.  I miss the days when you could get the 6MX chassis for like $30...should have stocked up at the time.  Speaking of which, when the 6M50 first hit the clearance section, it was only $20.  Why did I only get one?!?   

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Tube Amp Building - Tweaks - Repairs / Re: Help with Vibrolux Reverb

« Last post by Willabe on April 16, 2026, 08:58:38 am »

Great way to check your build for wiring problems;

http://el34world.com/Forum/index.php?topic=17701.0

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Tube Amp Building - Tweaks - Repairs / Re: Princeton Reverb circuit refinements

« Last post by stratomaster on April 16, 2026, 08:47:02 am »

You left off the screen node filter cap in your schematic. You'll need that.

Edit:
On closer inspection I see you're adding several board mounted filter caps and splitting the load with a can cap.  You do have screen and reservoir filtering, just in an unusual way.

You'll want to run the numbers again on the power rating (and voltage rating for that matter) on your bleeder.  It's dissipating nearly 2 watts. Replace it with either a 3W or a 330k 1W.  Check the voltage rating of any resistor you plan to use on HT. You'd be surprised how many commonly used ones aren't actually up to the task.

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Other Topics / Re: Meme of the day

« Last post by shooter on April 16, 2026, 07:31:34 am »

....

69

Tube Amp Building - Tweaks - Repairs / Re: Tips for building a super small, compact, gigable, lite, combo?

« Last post by AX84CH on April 16, 2026, 07:17:33 am »

Where can I find a blank chassis like the one used in the dual lite?  I can find a bigger one for like a plexi, but a shorter one would be great..

I'm not sure where you are but here is an option for folks in the USA.

Somebody recently turned me on to "SendCutSend" which can make all kinds of stuff.  In their parts builder, there is an AI designer where you can basically say "I want an 18x6x2.25 chassis with an IEC inlet on the rear left."  With a couple of iterations, I was able to add a row of 1/16" pilot holes on the front and back, folded lips and 4 caged nut holes.   Just as an example.

The size and type of material as well as the number of bends and finishing options all impact the price but I got two 18x7x2.5 chassis for something like 110 bucks shipped in one week.   

One can always find things they were were better or different but I was quite happy with the results.

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Tube Amp Building - Tweaks - Repairs / Re: A small friedman-inspired amp using an inexpensive power supply

« Last post by AX84CH on April 16, 2026, 07:11:04 am »

This is the one I'd zero in on... 30bux. 300V @ 300mA; enough for 20-25W amp without working it too hard.

Still, I prefer linear PS for tube amps. JMO.

https://www.amazon.com/Vacuum-Preamplifier-Switching-Transformer-100-265V/dp/B0DZGR1HPR/ref=pd_sbs_d_sccl_2_1/141-4689532-8312021?pd_rd_w=SY8Ej&content-id=amzn1.sym.aa738fbd-ad05-4d11-aae2-04b598db6305&pf_rd_p=aa738fbd-ad05-4d11-aae2-04b598db6305&pf_rd_r=PXC57AFWBQH84PVYSA2Y&pd_rd_wg=cdqpX&pd_rd_r=cf9d8605-54ab-40e5-9375-719858e5fb22&pd_rd_i=B0DZGR1HPR&psc=1

--Pete

I have ordered one of these to try and should have it shortly.   I'm not sure it will be radically different though an extra 20v is welcome. 

I would probably prefer a linear supply as well, all else being equal.   If these end up being workable for a segment of projects, they are considerably less expensive and lighter than a linear supply.  Of course, everything is a tradeoff.  I'm pretty happy with the amp I built so I would say it has been a general success.