Matchless Lightning build

[M Fowler]

I have to look at my Spitfire but I am positive that amp only has 8ohm and 16ohm and I have been running 16ohm cab.

You have me curious I will look tonight.

[Andy Le Blanc]

I remember statements to the effect that its perfectly fine practice with very
little detriment to distortion figures as long as the amp is operating within its
dissipation limits relative to the load. Now, the real issue becomes one of
the push-pull circuit and its loading sensitivity relative to operating class.

[Structo]

That's easy for you to say Andy!

[M Fowler]

Andy,

I feel some relative humidity coming on from that loading sensivitiy.

[Andy Le Blanc]

It's the reason I've see a lot of cathode bias amps from the forty's and fifties
working fine on original tubes and in playable shape ....
and why there's such an aftermarket for OPT for any thing fender based.

push a push-pull circuit to far the other side of AB1 with the wrong load or bias condition....... any ways....

Good looking build

[Rick]

I got a set of OEM style lightning trannys from TDS who was an early supplier and designed them for Matchless (they still hand wind them at transformer design and supply and on ebay). He told me the OT primary was 4K and the outputs were to 4 and 8 ohm if I recall correctly. The lightning I put them in was OK but a bit barky and coarser sounding, but I later built several more using a 6.6K for the Fender Deluxe OT and a weber 025130 PT and those amps sounded far superior in my opinion, much smoother and more musical and much, much cheaper trannys, but sounded great and very satisfied customers. Go figure...

[krash]

not Matchless related but EL84s push pull anyway, I find that a 4K primary on a pair of EL84s sounds like crud. It's ok at low volumes and with cleanish tones but if you push the power tubes very far then the distortion becomes harsh and shrill.

On the other hand, I build my 72s just the opposite, quad of EL84s into an 8K OT primary. Sounds great. Way smoother.

In fact, I think the taming of the harsh or brittle distortion in some TW-inspired builds may very well lie within using overmatched transformer primaries, that is 6.6K for a pair of EL34s or 8K for 6V6s etc. Just a hunch. I certainly can tell you that going the other way, EL84x2 into 4K greatly exacerbates the harshness or brittle tone you can get into with a TW-inspired circuit. And while we are taming harshness, 10K grid resistors on EL84s can be a very good thing.

[M Fowler]

I have been using 8k on all my two EL84 and 6V6 builds which I like.

I have been using 6k6 for my recent Express builds and I prefer the 6k6. No problem using the bright switch with this OT.

[M Fowler]

I have to look at my Spitfire but I am positive that amp only has 8ohm and 16ohm and I have been running 16ohm cab.

You have me curious I will look tonight.

My Spitfire is running 8 and 16 ohm taps only.

[Darkbluemurder]

Here is a Matchless Lightning I built this week. Will make faceplate and cabinet soon.

Master volume works well at mid to high volume but fizzy at low volume.
The Master volume pot cuts out at 75% so that will be replaced.

Mark

Hi Mark,

If you are going to replace the pot anyway why not change that cross line master to a LarMar PPIMV? To my ears this sounds a lot more consistent through the entire travel of the pot, and if dimed it's out of the circuit.

The LarMar PPIMV replaces the two 220k load resistors with a dual 250kA pot. Between the wiper and ground of each pot section there is a 2.2M resistor for safety purposes.

Cheers Stephan

[M Fowler]

Stephan,

Thanks that would be a good idea since I am replacing all the pots with PEC 2w I'll check and see if I have an Alpha 250KA dual pot in my stock.
Not sure why my Bourns pots (two of them) are bad first time that has happened to me.

Mark

[C Moore]

Hoffman has sold, and used IC filter caps for many years with no troubles. And I do not mean just Doug Hoffman himself, his customers have a long history with IC filter caps as well. Are they the equal of F&T? I do not know. Seems like caps are a going to war issue, too often.
Nice Job Mr. Fowler!!!!!!

[M Fowler]

Hired hand,

Thanks for the comment.

I use many different caps it all just depends on the amp I am building. I have no problems with the IC caps and just because a few don't like them will not stop me from using them or my favorites the JJ cap cans.

Mark

[Structo]

I think a lot of the bad opinions about IC caps originates with Gerald Weber.
He has said on many occasions that they are junk.
So people read that and accept it as gospel.

Maybe he had a bad experience.

A few years back there was a run of bad E caps. Particularly the radial caps used on PC motherboards.
It seems a certain industrial spy had copied a recipe for the electrolyte paste used in them.
Problem was he didn't copy it right.
The factory he was from (can't remember the name) manufactured thousands of caps with that paste.

Afterward a cottage industry sprang up to replace the caps on the motherboards.
The caps would either leak or fail all together from the bad paste.

[C Moore]

Apparently the "bad elytic paste recipe" is a proven fact at this point. I know BillM replaced a lot of IC caps on all those Blues Jr's that he works on. If I am not mistaken, they were always the same value of radial that went over the edge. I want to say 22/450, but always the same whatever the value was.
That is the extent of my "knowledge".