1x3 homebrew question

[bettyeboop]

I just built a amp that the schematic called for a 1446 for the first stage. I had several 2879's so I used one and ended up with one 2279 driving two 2879,,,



the first thing i noticed was not enough power coming from amp 175 watts. I have a bird 43 but only have a 100 watt slug...my cheap radio shack meter is calabrated the same as 100 watts on the bird....dont know how accurate the r.s. meter is at 200 but is good at 100watts.

I took off one resistor off then the other one between stages....i also bypassed trim cap. between stages.

I took the resistor off the var switch on the high side.


It is now doing over 220 real watts if my meter is right with 8 watts input and 17 volts after keying from power supply.

should I expect more? seems like I have seen this combo doing more. The pills are just warm after long trans at full power. It seems like the 2879 should drive the secondary more than the 1446. I used the same ferite transformers and windings for the 1446.

any suggestions please

I also want the simple bias with thermal control.....diode on top of pill or something....once there was a post on this.

god bless

davis

 

[bob85]

if you intend to bias that amp i would not use any driver stage, just make it a 2pill, if you want higher meter watts and no bias i would use a 1446 or 2290 driver,

ps i would never build a 1x2 or a 2x4 myself, a single 1446 has more than enough drive capability to overdrive the 2879's in a 2 or 4pill especially if its biased.

 

[AMPOWER]

Put back the 4.7 ohm 2W resistor between the 1-pill stage and the 2-pill stage...
Trimmer caps?? Those things cause problems...
post up a pic of the inside of the amp...
lets see what i can try to help you with ...
u need to tune the amp for LOWEST input watts and MAX output watts..
17V ?? id say put it on 14V and it will last forever...
you want more power ?? buy a bigger amp...
All you are doing now is jacking up the tuning in the amp ...
NOT GOOD you WILL blow it up ...

AMPOWER

 

[Crusher]

I am not sure, but I am guessing you are using design from PSF Tech or powerplate. Put that trimmer cap back inline. that cap is what couples the 2 stages together. I built 1 like it before, when I pulled out part and measured I think it was something like a 290pF cap value. The resistor is there to pad the input of the final section a bit. I like using a 47ohm resistor on both sides of the pot. for the input. It gives me a very low DK and alot of swing. A 2879 is rated for 100 watts. If you are getting slightly over 200 DK you are pushing that box especially if you pulled out some parts. it won't be long before the driver blows (this is from my expensive personal experience). but hey it's your money your blowing. Yeah a 3 pill will DK more, but at a certain point you start to sound like crap. At shootouts, Isee em DK 500-1000 watts. But then it is an expensive 10 second keydown. Because that is how long the pills will last.