Hoffman Amplifiers Tube Amplifier Forum

Other Stuff => Solid State => Topic started by: john121 on April 28, 2021, 11:06:30 am

Title: Amp distorting problem
Post by: john121 on April 28, 2021, 11:06:30 am

Hi and thanks for reading.
I have built the amp seen in the attached circuit diagram. The midrange and treble are reproduced fine but the amp distorts the bass.
Do you know how this problem may be addressed, what changes need to be made or components added / removed.
Q3 seems to be driven wrong. The lower output transistor appears to have no bias. The top transistor may not receiving enough voltage (possibly needs a bootstrap) .
Can you please advise how these problems or any other problems you have noticed may be addressed. This is a cheap and cheerful build, so am not intrested in a high performance amp, just want to get this one to work.
Thanks.

Title: Re: Amp distorting problem
Post by: shooter on April 28, 2021, 11:59:30 am

Quote

midrange and treble are reproduced fine but the amp distorts the bass.

at all volumes?
it take more ump to drive bass, also speakers, some are to cheap to give good bass response.
got a scope?

Title: Re: Amp distorting problem
Post by: PRR on April 28, 2021, 03:29:54 pm

There are better plans than this.

You have posted this on at least one other forum.

Title: Re: Amp distorting problem
Post by: john121 on April 29, 2021, 12:04:27 am

(http://)Thanks for the replies, much appreciated.

Sorry I do not have a scope, was hoping for advice from examining the attachment.

I have included an attachment with a recent mod just applied

Thanks