feedback...

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JeffreyJ
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Joined: Fri Jan 28, 2005 2:53 am
Location: stuck in the USA for now...
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feedback...

Post by JeffreyJ »

brother steve of the vacuum... I have a question for you... I have this amplifier that is pretty normal push pull triodes... well, normal for a single ended guy... and I was wanting to experiment with feedback to lower the output impedance...

now, I am a *total* rookie at feedback.. well, unless you count all the times I have removed it over the years... :lol:

but I took this amplifier... which I like the sound of... to someone's house and it just wouldn't do the overdamped bass thing like they like... to be honest, it sounded broken compared to his 300 watt digital amp.. and the speakers were supposed to be 97dB.. nothing a pair of gm70's running wide open shouldn't handle... so I began to think that it was mostly a function of output impedance and the resultant change in speaker damping (Qes)...

I have flipped through a few texts... basically they all say avoid triodes and use pentodes.. not a lot of help..

any thoughts? I know a transformer winder who is on-board should we need anything wound... :wink:

*much* appreciated...

Peace,
Me
sbench
Posts: 296
Joined: Fri Jan 28, 2005 3:45 pm

Post by sbench »

Triodes work with feedback just like pentodes as such. Where the difference is local feedback, like from the output stage plate to driver stage plate. If the DRIVER is a triode, the feedback is working into the nonlinear triode plate resistance load and the sound gets kind of funky.

Do you have a specific schematic in mind?

Steve
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