henry4841

First time for me to hear that output devices are used as switches and not linear devices. I have read articles on the principles of class D but have never heard it broke down in layman terms like Captain just did. I understand how class D works a little bit more now. I first read about class D decades ago with speculation back then of them taking over the audio amplification world. Never materialized until now and I can see and understand how it will eventually be the amplification for the masses. Class A will still be sought by discrimination audiophiles but expect other classes will fade out of favor. I have not keep up with what is new in the class D world and am not familiar with Zetex. I look forward to hearing more.

A better way to describe what is happening is to use water. Often used describing electronics. You have water coming to your house with a lot of pressure and volume but the faucet (valve) limits the amount of each you will get when you turn on the faucet. The electronic parts control the amount of power you will get at your speakers. You put one component in you may get more of this available power out or possible just the opposite depending on the circuit. This may make what is happening better understandable.

Yes, but with reservations. The amplifier is the driving force but the parts in it's path determines the amount of power the speaker will see. The shunt enables more of the power of the amplifier to go to the speakers. Without the shunt the power is limited by the part. Hope this makes sense. Informative link speaker builders would enjoy. The one thing that is not mentioned in the video is the phase shift caused by the extra parts in higher order crossovers. Any time you add a part it achieves what the designer is aiming for but it also brings some negative into the equation as well. There are always interactions when another part is added. Thanks for posting the link. I enjoyed watching it.

Be sure all your equipment is plugged into the same wall outlet. I would not think the MC 13 requires a preamp. Try using without pre. I personally do not use both pre and amp being tubes. Both can be sensitive to hum and together possible too much. Remove and replace the tubes a few times. Possible a bad connection between tube and socket will also cause hum. Same for any connections other than tube and socket, input connectors, etc.

A quote from Nelson Pass' Firstwatt web page. With our horns the first watt is the most important not how many watts an amplifier has that will never be used. "Dick Olsher famously remarked that “The first watt is the most important watt.” This sentiment has also been expressed by others as “Who cares what an amplifier sounds like at 500 watts if it sounds like crap at one watt?” With this in mind, I created First Watt in 1998 as a "kitchen-table" effort, exploring unusual low power amplifiers with an emphasis on sound quality.

I like those can type motor run capacitors for woofer to mid crossover, the kind PWK used. For mid tweet crossover I am using those NOS Russian PIO sealed caps. One can do better I am sure but you can also do much worse as well. The cost is not that great using the ones mentioned. Not sure about finding those sealed Russian PIO ones at this turbulent time though.

The only difference between the two crossovers is in the tweet, mid crossover. The A being 1st order and the AA 3rd order protecting the delicate tweeter. That point of crossover is, if memory serves me, 6,000hz. I made that statement just looking at paper and have not done a direct comparison audible. Sonically it should not be much difference but if you hear a difference I surely am not one to question what you are hearing. Technically, from what little I know, a 1st order has big sound at low volumes whereas steeper networks require cranking them up more to fill a room. Oh, the AA does have those zeners in the tweet circuit for protection that can degrade the sound somewhat but should not contribute to the sound that much. At least at normal volume levels. Sound is so subjective. Many can hear so much better then the average person. My grandson cringes when he hears a dog whistle where I, like most, hear nothing. As far as breaking in those few components in a crossover network, doubtful in my opinion. One probably just gets use to the sound after some time. Tubes require some break in time by the very nature on how they work. SS electronics should be broken in after a few minutes or hours at most. The only time I really noticed some breaking in of a SS electronic piece of gear was with one of my TPA3255 amplifier builds. Very weak bass on fire up but after a few minutes some of the best bass from an amplifier I have ever heard. Big change but only taking a few minutes. Tubes have gases and other particles floating around that the getter absorbs being the reason for sounding better after 100 hours or so.

Perfect little kit for those wanting to build with the reward of sound that should cost much more. The bigger Nelson Pass projects do sound better but one cannot fault the sound of the little ACA. Standing it's own with McIntosh and Parasound says a lot.

Not surprised by that statement. If someone is happy with the sound they have why fix it. Nothing wrong though with those willing to spend the money just to satisfy some curiosity. That is exactly what I have done building over 30 amplifiers.

Doubt it has to do with network and more to do with new caps. Not a significant difference between the two.

And the price is supposed to be cheaper than the ACA being that it does not require a case. I believe the ACA is $299 so less then that. My comments are not the actual kit build. I just ordered the board and sourced the parts myself. Also I have a special case with a linear PS section I use to test amplifiers with. The neat thing is most all of the NP Firstwatt offerings use the same voltage rails enabling swapping out just the amplifier boards.

I've built most all the Firstwatt clones including the Nelson Pass' projects for diy'ers. This little ACA sounds remarkable good considering you are getting the SE class A sound for little money. Class A amplifiers are not cheap to build or buy. The sound of the ACA is much like the sound of my SE BA-1 project I built many years ago. Not a power house but for many plenty enough. The BA-1 and BA-2 projects are not cheap to build requiring matching of the multiple output devices for best sound. Big powerful power supply section and expensive case with large heatsinks to cool those mosfets running in class A. The ACA is a very nice cheap project rewarding the builder with an excellent sounding little amplifier. Great project for those wanting to get into diy.

Heat is the enemy of capacitors. Recently restored a receiver with new caps and most all if not all the capacitors were in tolerance but were replaced anyways being 45 years except for one board, tone control that was mounted upside down. All the caps on that upside down board were bad. Being upside down it held held heat generated by the receiver destroying them. Just showing how heat destroys electrolytic capacitors.

What you say!

😀 SET sound using SS devices. Shame those power J-fets are no longer available for diy'ers. Discrete audio transistors are not profitable to design anymore. The old ones are slowly being phased out.

If you are listening over 95db, 100db you can be sure you are going to have hearing problems as you age. Horns are so clean you do have a tendency to increase the volume. If you cannot carry on a conversation while listening you can be sure you are listening too loud.

A quote from Nelson Pass on the other forum regarding power this week. This is with a full range speaker that I assume is pretty efficient but probably not as much as our speakers. " I haven't seen any mention of the loudspeaker's sensitivity. I have some full rangers that can break your lease with an ACA Mini." The ACA Mini is a few watt diy project. The myth of needing gobs of power with horn speakers is just that, a myth propagated by manufacturers promoting their products. Old timers like myself can remember the power wars in the 70's and from all accounts it worked selling many monster amplifiers. More has to be better, right.

Did not do the test knowing already 5 watts is the sweet spot for me with tubes. Done similar test many year ago.This is not to say I would not be happy with the couple of flea watt amplifiers I own averaging 2 watts or less. There is some sacrifice of bass with the flea watt ones but if I had to I could be satisfied with them.

It always happens so I would not fret over it too much. This thread would have died out long time ago with just a few post if it had not deviated from original poster to some degree. The point is the OP probably got an answer to his question early on in this thread. Maybe someone learned something else from this thread which I would not say is a bad thing.

It's what we do with every long thread.

I think it does limit movement but Islander has his opinion which may be right. The term compression means restriction and if PWK did make a "compression" driver out of the 15" woofer I believe there is restriction on the movement of the cone. If the baffle with the small slit does not restrict movement I can see no real benefit of having it in the first place. I also believe the small chamber the speaker is enclosed in does much the same, compresses the air on the rear movement. I am no where near an acoustic engineer and it is just my opinion PWK made a compression driver out of a 15" speaker just like the compression driver in the mid horn . If one took the doghouse out of the horn part of a LaScala and tried listening with it I doubt there would be much bass to hear. Just as a compression driver without the horn does not produce much sound without the horn. I am sure I read in one of PWK's many papers that the bass speaker moves very little reducing distortion. I believe that is what he was trying to achieve with the bass horn in the Klipschorn and LaScala. I am just a layman and and this is just my humble opinion.

Drivers are most often called a compression driver. How do you make a big 15" woofer into a compression driver? Stick in a small box that restricts it's rear movement and install a baffle with a slot in front of the woofer to restrict the forward motion of the speaker. You have now made a low signal compression driver. If not put in a horn this setup would not make much bass. Drivers move very little compared to conventional speakers. The horn part amplifies the small signal. One good reason for compression drivers over conventional speakers is the small movement of the driver reducing distortion and increasing transients. In a normal conventional large speaker there is flexing all over the surface of the cone when trying to produce music that contributes to distortion. A good reason we prefer horns over conventional speaker systems.

He may have meant using a full range speaker and just using the bass bin for the lows. I have done this but it does require designing and building a crossover network yourself. Mine worked real well but I lost some quickness and detail vs the original drivers. Very pleasant sounding though. Again sound is subjective being that my best friend preferred this setup, full range speaker setup, over my stock speakers in my room. I used Fostex FE166EN's which have been discontinued. Open baffle setup sitting on top of my LaScala's using just the bass bin for the lows. Still have the setup but has not been used in years.

The bass a LaScala makes is outstanding but is limited in how low it will go. If one is playing The Cincinnati Symphony Orchestra's Tchaikowsky 1812 too loud with it's real cannon shots you will jump out of your chair when they go off. Right in the LaScala's wheelhouse. Listened with my LaScala's without a sub for decades and did not know what I was missing until I installed a good sub. Mine is one I built myself using a Dayton Audio RSS390HF-4 15" Reference Series HF Subwoofer in a 6cu ft sealed box. Too big for many with a low WAF but is supposed to go really low in such a big box.

The way I see it is, PWK takes a 15" speaker and makes it a driver much like your mid and high driver. Look at the space the 15" speaker is placed in. Much smaller then the space for the speaker in a Cornwall. That and the LaScala speaker has a plate with a slot in it limiting the travel of the speaker turning it into a driver. The small enclosed chamber with the small front slot makes it a driver instead of a just a speaker. The horn part of the speaker is what creates the amplification of the low notes. The Klipshorn is similar except the horn part is folded 3 times instead of two in a LaScala limiting the low frequency it will produce. Drivers travel much less then a speaker which limits the distortion a speaker has all over the cone with it's longer travel. This is what makes horn speakers much more cleaner and faster then conventional speakers, all drivers. Naturally with only 2 folds of the horn the LaScala is not going to produce the very low notes like a big boxed Cornwall type speaker with the same speaker. I hope this makes sense and if I am wrong I am sure others will chime in.