Starting Bass Amp Build (tube Pre SS Power)

[hesamadman]

Finally drew up my schematic for the bass amp. I will have to tweak the values in the tone stack since it was cut from an Engl guitar preamp. I am trying to implement a cathode follower so it can drive the solid state power amp even though the spec sheet of the SS amp does not even list a recommended impedance. This is just a very generic CF. I will mess with it on my breadboard before I build it into a rack space. I will also have to work on a power supply. Any suggestions on a PT would be much appreciated. I would like to install it inside the rack space rather than on top of a chassis. 


This is the SS power amp I am using
https://www.parts-express.com/sure-electronics-aa-ab31282-1x200w-class-d-audio-amplifier-board-t-amp--320-3360

[labb]

Take a look at the Antek transformers....You might want to take a read through this thread...http://www.ax84.com/bbs/index.php?area=23

[hesamadman]

The link I had posted above didn't work. I fixed it. I found this transformer that would work fine for the solid state amp.


http://www.mouser.com/Search/m_ProductDetail.aspx?Hammond-Manufacturing%2F182Q9%2F&qs=savM97goi5i9GBJGkpYUzg%3D%3D


I'm guessing i won't find a PT that's all in one. I'm going to need a separate PT for my plate voltage and filaments. But could use a very small one for only two 12ax7's.

[DummyLoad]

I found this transformer that would work fine for the solid state amp.
http://www.mouser.com/Search/m_ProductDetail.aspx?Hammond-Manufacturing%2F182Q9%2F&qs=savM97goi5i9GBJGkpYUzg%3D%3D

not if you want 200W output. you're going to need at LEAST a 200VA PT if your class D truly is 100% efficient. not likely. plus datasheet states REGULATED.

you need a 36V 250-300W regulated switching PS for full 200W output into 3? ohms. see note number 8 on datasheet.

bah! 3 ohm load - they publish bigger numbers with that. never heard of a 3ohm speaker.  probably makes less than 60W into 8 ohms. you can do much better than that module.

if you must, then this one should work... 35bux + ship

--pete

[drgonzonm]

Three 8 ohm speakers in parallel is slightly less than 3 ohm.  will handle 4 speakers in parallel. 

regarding input impedance,  spec sheet states typical 10k with a max of 11k ohm. 

Post some sounds when finished. 
 

[hesamadman]

There's a few things I missed on the spec sheet. I don't know how I didn't see the input impedance is at 10k.


I'll most likely be using a 4 ohm cabinet with this one. I might try a higher power module later but I already have this one.


Would it make sense to just buy a power supply like  suggested and mount it inside chassis rather than building one?

[PRR]

You sure do not need 3 stages of gain!!

You sure don't want to build a cathode follower and then add 220K of added resistance.

The attached is closer to what you want.

> never heard of a 3ohm speaker.

For a constant voltage (low resistance) source, lower Z is higher power, obviously. In TV-sound and some car audio we are seeing "3 Ohm" speakers to cheat the ratings on 4-Ohm chips, and now chips rated for 3 Ohms. Obviously if he does not want to cheat some more with three 8r (2.66r) then he will apply 4 Ohms and take the 4 Ohm rating.

[drgonzonm]

From what I saw on the website, you might want to include a master volume, also a plugin. 

I would purchase a power supply and mount in the the cabinet.  Now how are you going to power the pre-amp? 

[hesamadman]

PRR that seems exactly like what I should be doing. Thanks for that edit. I will go that rout.


I think I am going to find a more suiting class D module for this build.