Need help to choose a Pass amp

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Hello Passlab diyer's .
I'm new to diy ,but have friends that can help .
I'm tri-amping an new speaker and I'm using 300B SET's for the
Tweeter & mids .I need something for the bass driver which is a
PHL 12" 4530 ,94db ,min6.2ohm@ 250hz .Xover point is 350hz.
Is the A40 to old a design and how would the F4 go I think my pre has a gain of 20 .I sit about 3 to 4 metres away from the speakers .
Any help much appreciated ,

With a fairly efficient woofer you're not going to need all that much power. The A-40 can be built, but the output devices were rare even when the design was new--impossible to find now. I believe Nelson posted some suggestions as to what devices might make good substitutes, but I have no idea how to tell you where to find that post.
More buildable designs would include the A-75 and the smaller Alephs. Note that the output stage of the A-75 can be scaled up or down if you want more or less power. However, my experience (I'm quad-amped and my main midrange amp is tubed) is that the Alephs are pretty decent matches for tubes, as they have a somewhat warmer sound. Your candidates there would be either of the Volksamp versions--a 30W and a 60W--or the 'normal' Aleph 3 at 30W. There was a 60W Aleph, but I can't remember the model number at the moment. It was either the 4 or the 5.

The one and only
Joined 2001
Paid Member
Depending on what kind of hurry you're in, I do have a new
DIY amp coming up that would take the place of an A40. It's
going to be a very simple design.

The PHL 4530 is particularly easy to drive, so almost anything
will do the job.

What are you going to use for the mid and top drivers?
Hello Nelson, I,m in no hurry will be building the mid & tweeter amps first .

For the treble I,m using the Raven R1 ,1.1,94db @ 2.6 ohms above 1000hz ,so the output trannies will be wound to match impedance.

The midrange driver is a 6.5" PHL 1120 ,96db 8 ohms.

Thanks for the replies

Official Court Jester
Joined 2003
Paid Member
jupiterjune said:

WooHoo! can't wait to see it!!!!!!!

I think this thread must have escaped everyone's attention, or there would be alot more excitement about this!


you think?

seems to me that - in last few yrs - greedy boyz are at least two amps after Papa ........... mebbe they are just scarred


besides that - I'll be glad to see it ...... new spark ;)
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