Matchless 15 watt with 5e3 OT

[halfmassive]

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 fit the slightly larger 18 watt style transformers that it seems many use on matchless builds. Those are rated at about 8k primary at 8ohms. I don't care about spending the extra dough on a new OT but I'm afraid it won't fit on the chassis. I hope the current one works so I don't have to find a whole new chassis (and then probably a new cabinet) for this build.

Please excuse my ignorance. I did a lot of searching but I don't know too much about different transformers, since I've mostly worked on kits until now.
Thanks!

[M Fowler]

https://tubeamparchive.com/viewtopic.ph ... t=spitfire

I did this type of build and it didn't sound that good so I put it back to 5E3.

Mark

[M Fowler]

The 18w OT isn't larger then the Deluxe 6k6 but mounting holes might not be the same, no big deal mark for holes and drill.

But yes you can run the EL84's on the 6k6 OT.

[halfmassive]

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!

[M Fowler]

Your PT is a laydown type so I see no problem with an angle on the OT mounting.

[M Fowler]

The 5e3 chassis is slightly wider than 4" and triodestore MC 5e3 OT is 3 1/8".

The MC 18w OT is 3 9/16" so I don't think the 18w OT will be wider then the chassis.

Mark

[halfmassive]

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 searching i couldnt find anything too clear on the importance of choke placement. Again, thanks very much for the help.

[M Fowler]

I've never had a problem with noise from a choke but people say it happens.

I would just mount the choke 90 degree angle from the OT and all should be well.

[menger66]

The spitfire uses a 4k primary OT with 4 and 8 ohm taps, this gives it
its unique tone, Trinity sells a 5k OT that will get you close, or you could use a 8k 18watt ot and run the 16 ohm tap in to a 8ohm speaker to half it for 4k there is a member in the forsale section selling 18watt iron and his ots have duel primary with 4 and 8k pri, 6.6k will work as will 8k i've used both but to get that matchless spitfire cool reverb like clean tone you need to use 4k otherwise the amp winds up just a el84 screamer, If you go with a 18watt output transformer you could try both 4 and 8k primaries and decide for your self which one you like mark

[rp]

The spitfire uses a 4k primary OT with 4 and 8 ohm taps, this gives it
its unique tone, Trinity sells a 5k OT that will get you close, or you could use a 8k 18watt ot and run the 16 ohm tap in to a 8ohm speaker to half it for 4k there is a member in the forsale section selling 18watt iron and his ots have duel primary with 4 and 8k pri, 6.6k will work as will 8k i've used both but to get that matchless spitfire cool reverb like clean tone you need to use 4k otherwise the amp winds up just a el84 screamer, If you go with a 18watt output transformer you could try both 4 and 8k primaries and decide for your self which one you like mark

+1, also, are you all talking 5E3 OT or BF OT? IMO the 5E3 will be too dinky for a Matchless. The real Matchless 2XEL84 OTs where pretty husky unlike most other classic 18 watters. More like the old AC15 OTs. The beefer BF Deluxe @ 6.6K might get you close enough, but as menger66 said, do you want a Matchless or just an 18W screamer?

[halfmassive]

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 and it worked well for a small gig I had as well. More headroom than the 5e3 and I actually like the overdrive on this amp more, but it probably too loud for most of my situations to get full blown pure amp distortion. I'm happy I made the change.

Thanks very much for all of the help!

[Darkbluemurder]

Congrats!

I once had my Sundown A-50 converted to a Spitfire build with a dual 6V6 power amp. Sounded pretty good cranked but was very loud.

Have fun with that amp,
Stephan