Tube Amp Archive

Lynxtrap wrote: ↑Tue Jun 27, 2023 2:45 pm Looks like a DC coupled LTP. http://www.valvewizard.co.uk/dcltp.html

OK - thanks! That's it - exactly...

Cheers, Tom

Hi all, I came accross a rarely used PI variant I'd naively call "self-split", just like those archaic self-split power stages but with triodes set up as a phase inverter followed by a pair of power pentodes (EL84). Basically an LTPI without the long tail. Marshall used this design in the 2022 from ...

You should write a book! Yeah - leaving the book writing to the truly enlightened. Actually I'm waiting for one of the real gurus on this forum to tell me I'm completely wrong. :D I noticed that if a line was drawn between the Q point and the calculated point at the 0V knee, The line briefly passes...

To fill in a few blanks, I am using a CLC filter but the unloaded B+ is huge, like 496V. I haven't constructed the voltage drop circuits for the other sections yet (Plate, screen, reverb, inverter, preamp), so I guess I can't answer what those voltages would be but this gives me a something solid t...

OK, I'll bite. This is how I use the load-line calculator for pentodes. This is a step-by-step sequence: 1.) Select the tube type, select P/P or SE. P/P in this case... 2.) Set the HT. 360V seems to be the value for your design 3.) Set the screen voltage. To do this I need to estimate the voltage dr...

Despite a good reviews, Laney's Lionheart SE amp line doesn't seem to have got much market traction, the higher power models at least having been discontinued https://www.gak.co.uk/en/laney-lionheart-l50h/57234 That's a P/P amp, at least according to the schematic I've dug up... Laney L50 Schematic...

Also note that a output transformer for a build such as this new will run you well over 175 bucks. I've always suspected we're a bit too quick to dismiss hefty or even huge single ended guitar amp designs as inefficient dinosaurs that we as a civilized builder society have long left behind us. This...

Hi! I have built two kits from Tube Town in the past (AC30-ish EF86+ECC99 "Molly" and a Pink Taco clone). Both were dead easy to assemble. One used a tag strip, so was a bit "point-to-point", the other used a turret board. The full documentation is what's online in the PDF - there's no additional co...

Yes, and that's where things got confusing. The data sheet I have list to 360 volt plate voltage columns, and a 450 volt column. The 360 volt column, with very little differences in the rest of the data, shows two different anode to anode resistances. Somebody needs to do a really good video on how...

...all of the above plus one important variable: Screen grid voltage . With fixed HT the screen grid voltage determines the height of the Ug1=0V curve; determines the height of the knee; determines the inclination of the load line(s), which is the OT impedance across both valves. The steeper it is, ...

The reading I've done suggests getting an output transformer about1.5 times larger than the expected output. So, should I select a TX that can handle around 50W? Can't go wrong with that strategy. More iron, more boompf - i.e. low end. Although I've heard that some builders like the sound of OTs so...

I didn't see an expected power output in that chart. Is more info needed to get that or do the results provide values that can be used to estimate power?

Look again! Right hand column, Output Power at g1=0. Theoretical value is 30W for the parameters I set...

As a starting point I entered the little information available (tube type + HT) into G.Amato's Loadline Calculator , derived screen voltage from HT and grid bias and aimed for the knee zone of the 0V line with these parameters: 360V HT, 320V Screen. OT impedances around 5k look about right. This is ...

You at least would have to specify the HT for your project. What's the power transformer's spec? Solid state or tube rectifier? If tube rectifier - which tube?

In Class A the grid curves and therefore the plate current vs. grid voltage expands on the positive swing and compresses on the negative swing... Asymmetric compression. The same effect as a "cold clipper" - on a smaller scale. Yes, I see that now - I hadn't thought of that effect before! Another r...