What's the take on the MA 50 and the MA 100 power amps?
I bet they sound great! Just to be clear, the mono switch on these does NOT put them in bridge mode. They have no bridge mode. It connects the two channels inputs together so it works in mono. IIRC you have to add shorting links between the two red output terminals and between the two black but that's just IIRC, I'll have to check. It then works with the channels in parallel to give twice the current and twice the damping factor.
Thanks Ark, yes they do sound pretty good, maybe just a little flabby in the bass. I understand how the mono button works and I used this when vertical biamping with these when they were mine. I did have a wiring diagram somewhere when running as monos but I’m buggered if I can find it. I would be interesting to get these out of hibernation and connected up
to my TLS80s. Running them as monos might just cure that touch of bass flab but I must say they never sounded harsh or strident ever.
It does! I mentioned this earlier up thread
Indeed and thank you.
When I overhauled them I made a temporary heatsink out a large L shaped piece of aluminium so I could take my time setting the bias. With the lid off these things get hot bloody quick. Tbh I think the lid/heatsink is a bit marginal. I’ve had five P140s and two had split lids and the other three had one piece lids. I do prefer the single lids.
If anyone wants to build a P170 type amplifier then I have a design/layout using discrete transistors, if anyone wants it modified to use an op amp then I can do it if you ask nicely, promise to actually build it and give a donation you can afford to charity. The design uses to3 transistors and is quite listenable, I use it upstairs where it replaced a 303, there is a plastic transistor version that I haven’t built but will almost certainly work.
Sorry, didn’t make it clear plastic packaged MOSFETS, easier for the diyer.
So - can one of tell me what the X-A1 that I had some years ago was? Is it an A1 in a different case? or something else.
It blew up the power supply unit and the repair guy I used could not find out what transformer was required, so it got left unrepaired. Shame, I rather liked it.
Don't get the X-A1 and the A1-X mixed up.
The latter is a close relation to the A1 in the same griddle casework.
The former is from the later, wider extruded sleeve and ally front panel family, with external PSU. This ran cool with just an aluminium billet sinking out to the half width casework and ran cool.
How’s sound quality of P180 compares to A270/A370? If can manage to get rid of those heat issues..
I use to own the A200. Loved the sound but got a bit fed up with the sound cutting out every 30 mins, although it was never pushed hard! just let it cool down for a few minutes and the sound was restored. Never heard a CD play all the way through whilst I was using it! ' probably a blessing in disguise'.
Ray
Cheers Jez.Sounds like it had far too much class A bias and was heating up until the bimetallic strip thermal cut-out was operating! Terrible QC! The quiescent current in this range (A1 etc) was set by a pair of high value fixed resistors and it was just assumed that all would be correct whereas in practice it would vary quite a bit depending on the transistors used ie the batch they were from etc...