Tube Amp Archive

I just added a filter cap to the spitfire stage which brought the voltage up to the preamp which brought the amp back to life. Its still not as tough sounding as my other spitfire but its much closer. Although I did use a 16 uf instead of a 22 uf since it was all I had on hand at the moment. I plan ...

Thank very much Matt. I appreciate your extensive help. I'm going to try some of these out and report back with my findings.
Thanks again

Thanks very much. What you describe sounds about right from what I am hearing. Sorry for my ignorance, but if I were to go the route of reducing the dropping resistor, you are referring to the 22k resistor on the preamp filter cap correct? How low would I want to go here? I guess I would start with ...

Here is the layout I used. I basically cobbled it together from the spitfire layout and added the ef86 channel from the dc30. I believe I am using the opposing pi inputs for each channel but I'm not really sure this the first time I've not used a "stock" layout. I am aware of the ef86 gain differenc...

I just built an amp that is basically a 2 channel matchless spitfire with the standard spitfire power amp section and 12ax7 preamp on channel 1 with an ef86 preamp in channel 2. The 2nd channel (ef86) sounds awesome but the first channel (the 12ax7 spitfire) is lacking in volume. It still gets loud ...

I finished the build conversion a few weeks ago and everything went perfectly. The first time I fired it up everything was just what I hoped for. I used the weber 5e3 trannies and they sound great. Not sure it has the true matchless sound but the amp is much more versatile. Perfect rehearsal amp now...

Anything I need to look out for as far as choke placement is concerned. The ot and pt on the 5e3 chassis are too close to one another to fit the choke in between (which is how it is on my jtm45). I was think of putting it next to the ot near the preamp section. Is the placement too critical? When se...

Thanks for the info this helps. For a new ot the actual chassis on the 5e3 might be too short for a 18watt ot just by a hair. Can I angle an ot slightly to get it to fit? I have read that the ot and pt need to be angled 90 degrees from one another. Again sorry if this is a stupid question.
Thanks!

I want to convert my weber 5e3 over to a matchless spitfire. I have figured out everything for my conversion except for the output transformer. Can I get away with using the weber 5e3 OT that I have currently (6.6K primary at 8ohms speaker load) with the 2 el84s of the spitfire? The chassis may not ...

I measured the voltage in mA instead of volts. Now I've got the correct reading.

Thanks for all of your help!

I'm not sure about the ohms law math. Should I simply be adding the volt readings for the primary and the screen grid or do I need to do some division to get the right reading to get the 34.7 I just added the mA readings on the primary and grid. for the I=e/r do I need to for example do 29.6mA/60.8 ...

So now I measured every thing and got: resistance 60.8 ohms from center tap to pin 3 of power tube 1 61.9 ohms from center tap to pin 3 of power tube 2 468 ohms across both screen grids Volts 29.6 mA from center tap to pin 3 of power tube 1 29.4 mA from center tap to pin 3 of power tube 1 5.3mA (Scr...

I figured out the first part. With no power and no tubes I read 60.8 ohms from center tap to pin 3 of power tube 1 61.9 ohms from center tap to pin 3 of power tube 2 468 ohms across both screen grids I'm slightly confused about step 2. Do I turn the amp on but not standby and then read from center t...

here is the link for the weber kit I'm using. https://taweber.powweb.com/store/6m45_layout.jpg From my OT I have red blue and brown. The red is connected to the standby switch which I believe has a wire running to the filter caps from that. Is this my center tap? And do I measure these pins with the...

Which is the center tap? I've learned a lot recently but am still pretty new to some of this. I'm using a weber 6m45 kits if that helps at all.