18w Stand alone power amp

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Mancunion
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18w Stand alone power amp

Post by Mancunion »

Hello there.

I recently built a Soldano X88r preamp clone - quite a challenging undertaking but i managed to wrap it up...
Now i need to build a matching power amp.

I have a set of 18w transformers which I salvaged from my very first build (i reused the chassis and ither bits for other orojects along the years).

I figured i could blatantly copy the power section of the Marshall 18w, using only 1/2 of the first preamp stage and adding a negative fb loop.

Now the one thing i couldnt figure out is how to keep the response as linear as possible? I’m open to suggestions!

Thanks
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KagliostroAmpwww
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Re: 18w Stand alone power amp

Post by KagliostroAmpwww »

I'll try to add a an NFB with a pot + resistor instead of a simple resistor to be able to vary the NFB level at taste

K
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Mancunion
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Re: 18w Stand alone power amp

Post by Mancunion »

KagliostroAmpwww wrote:
Sat 03/25/23 10:17 am
I'll try to add a an NFB with a pot + resistor instead of a simple resistor to be able to vary the NFB level at taste

K
As in a “resonance” control? My SLO builds have exactly this arrangement but I wanted to keep it simple.
Thanks tho!
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KagliostroAmpwww
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Re: 18w Stand alone power amp

Post by KagliostroAmpwww »

No, simply a variabile resistor

The fixed resistor is to fix a max value for the NFB signal & the (in series) potentiometer is to be connected as rehostat to perform the reduction of the NFB signal of a desired level (use your ears as feedback instrument)

Nothing of complicated

K
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TriodeLuvr
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Re: 18w Stand alone power amp

Post by TriodeLuvr »

I wouldn't use NFB in an amplifier with a Marshall-type LTP inverter. It will negate the desirable tone of the inverter and cause a coarser breakup at high volumes.

Jack
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Unit_1
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Re: 18w Stand alone power amp

Post by Unit_1 »

Although using NFB with LTP pi isn't unheard of
https://robrobinette.com/images/Guitar/ ... _small.png
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Bieworm
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Re: 18w Stand alone power amp

Post by Bieworm »

Unit_1 wrote:
Wed 03/29/23 11:51 pm
Although using NFB with LTP pi isn't unheard of
https://robrobinette.com/images/Guitar/ ... _small.png
auwch! You're referring to Fullerton type amps...not the sweet Marshall LTP PI overdrive you're eliminating with a NFB loop.
FWIW the bassman without NFB loop sounds sweeter too IMHO
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