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Old 25th February 2005, 11:43 PM   #1
ashawn is offline ashawn  Taiwan
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Question 300BSE power amplifier circuit

I want to DIY a 300BSE power amplifier recently, could somebody recomend or provide me a wonderful and robust schematic??? I will use Lowther PM6 speaker to match it.

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Old 26th February 2005, 12:25 AM   #2
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They're not my cup of tea, but how about this?
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Old 26th February 2005, 06:47 AM   #3
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I agree with Brett.Go with Kuei's (Thorsten's) design.And I'm sure if you will start it, he will help you in DiyAudio's forums.
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Old 26th February 2005, 08:35 AM   #4
Previously: Kuei Yang Wang
Join Date: Nov 2002
Default Re: 300BSE power amplifier circuit


Originally posted by ashawn
I want to DIY a 300BSE power amplifier recently, could somebody recomend or provide me a wonderful and robust schematic??? I will use Lowther PM6 speaker to match it.
There are many ways of creating such an amplifier. I have build more than a few myself, my latest (the Lady Day Plus 91) was already linked.

Oh no - YAWE91B300BA (Yet Another WE 91B 300B Amplifier)

An article that covers the fundamentals I wrote a while back is here:

Some thoughts about singleended Valve Amplifiers

I have since been able to research more a variety of small design tricks from the days when Valves where new (things like Gridchokes, the WE Cathode connection and other Hum/PSU Noise noise cancellation schemes) and this does impact somewhat on some of the recommendations, which as a result become somewhat more relative.

Here some details on some the variety of Amp's I build:

Another Lady Day Chassis (Schematic & pictures only):




A tour de fource in modern SE Amp design - this one was used for a long time with Beauhorn Virtuoso and other Lowther besed Speakers plus Goodmans Axiom 80:


A PSE Amp that does quite well with lower sensitivity Speakers:


I have also experimented with DRD and split supply direct coupled amplifiers, they are very good too but can be tempramental, rely on proper switch on sequencing and so on, withoput offering a quantum leap in preformance, so I abandoned them as not too well suited in the real world.

Other designs of Poweramp's I quite like are linked below:

Simon Shiltons amp design journey:


I especially recommend Figure 2 which is easily modified for 300B Output Stages and is in effect the SJS Arcadia Amplifier plus Figure 4 or Figure 5, Figure 5 is practically the same (more or less) as the current "low gain" version of the Border Patrol 300B SE Amplifer.

A similar design but with switch mode supplies is here:


My second Lady Day chassis build with WE437A shows the"economy" implementation of such circuits using self bias, WE PSU noise cancellation (this is as good as a regulated supply - try it) and parallel feed IT coupling (okay, we call it gridchoke coupling - same thing really).

Jack Elliano has placed some of his designs on-line, the 300B DRD is a very good amp in it's own right, if you check quite a few DRD style Amp's have been build by Posters here at DIYA.


Personally, I like the Legacy with C3m and the LD+91 a little better than the WE437A driven Amp but the 437A driven amp has more grunt but less delicacy. Sort of feather weight vs Belter Weight Boxers....

There is not all that much between the three.

A well implemented DRD or the F4/5 SJS Amp's) falls into the same sort of general sound as the WE 437A driven LD.

I hope this gives some ideas.

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Old 26th February 2005, 05:51 PM   #5
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here is a beautifully simple circuit from jc morrison:


the quality of your parts choices will be quite audible.

a classic imho.
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Old 26th February 2005, 07:18 PM   #6
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Check out Dick Olsher's T Rex amp on EnjoyTheMusic.com It has several interesting refinements. The DRD amps are very good sounding. I've built several pairs and people are amazed at how good the bass is.

Andy Bartha
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