I need a lesson in selecting Output transformers.

[dragonbat13]

I want to select the proper OT for a build I am doing. I think I have annoyed the members on here enough with my uninformed posts. I need to do my homework!

So I have been looking for some info on the WWW on proper selection of output transformers. I am looking for info on proper specification selection, a way to figure out what transformer specs should be used for such and such tube, ect. Unfortunatly the only things I have been finding is BS about how paper from a specific 1953 print of mad magazine sounds much better than recycled cardboard from a fender shipping box of the same era when used as an insulator

I think what I am looking for is how to figure out load lines.

Does anybody know where to look for this information?

I plan on buying some books. Some good recommendations on that would be helpful also, but I would like to find some stuff on the web while I wait on the books in the mail.

[M Fowler]

Here is a sticky from the technical section of this forum which contains a lot of reading material for you. https://tubeamparchive.com/viewtopic.php?t=9023

However, having said that the best place to learn is from amps already designed such as the Champ, Princeton, Deluxe, Bassman and Twin Reverb.

Notice I went from single ended to 100w amp. Check the specs of those replacement transformers and you will notice how the HT mA increases with wattage. For the OT you can see that the primary impedance is higher for a lower powered amp 8-10k compared to 1k2 or 2k1 for 100w amp.

Mark

[Structo]

A good thing to learn is how to read tube data sheets.

Take the 6L6 tube, there are a few different designations starting with the first 6L6 made.

The modern 6L6GC is a 30 watt tube (supposedly).

Look at the heater current, .9 Amps or round it up to 1 Amp.

Two tubes will draw 2 Amps, four tubes 4 Amps.

Then check the plate voltage maximum rating- 500vdc

Next screen voltage- it says 450vdc but with a note. It says in a push pull circuit it can be 500vdc.
Generally you want the screens a few volts below the plates for long life and good tone.

Plate dissipation - power output at max 30 watts each tube.

Screen dissipation - 5 watts

Look at the load resistance, plate to plate. This is what the primary of the output transformer should be close to.

Then it will list what the grid resistors can be.

Then look at the Characteristics and Typical Operations.

This is the Classes of amps designations.

Most push/ pull guitar amps are AB1 Push-Pull and typically have the higher plate voltages for higher output since we are not that concerned with how high fidelity they are.

Then you have the load lines. These can take a while to learn how to work and read.

Data sheets are your friends and you can find just about any tube on the web.

Here is a handy tool for looking up tubes.

http://www.duncanamps.com/tdslpe/

[dragonbat13]

as far as the tube data sheets, I bought a RCA tube manual (1966). I have been needing that and plan on reading it ASAP.

[Phil_S]

Check Merlin's site: http://www.freewebs.com/valvewizard/index.html
I think a search will turn up something on load lines and a load line plotter under the links section.

[gingertube]

Patrick Turner's site has quite a bit of useful tech stuff. Aimed at HiFi BUT surprise, surprise, what works for HiFi works just as well for guitar amps.
Load Matching Beam Power Tetrodes
http://www.turneraudio.com.au/loadmatch ... trodes.htm

If the maths is beyond you, then use the tube datasheet values, they will always give good results.

Cheers,
Ian

[seedlings]

Here's the easy easy version

CHAD