Simple Chip Amp for P to P wiring

[danielwritesbac]

Originally Posted by ratza

I don't use simulators, just build, test, measure and listen. I still don't get it: why carbon is better than metal? If you really want to get rid of HF noise, you put a capacitor between inverting and non-inverting inputs of the chip and/or a low pas fillter at the input. Those resistors have nothing to do with efficiency.

The all band performance of metal film resistors is better for loads, and its more efficient at this task.

Remember that the project is also about symmetry of a chipamp on bass with a vacuum tube amp on mids and treble.

Yes, thank you for mentioning the cap. The physical model has a 100pF ceramic cap as a load across the pins of the RCA jack. The capacitive load is pin-to-pin with the input cap at the RCA jack (divides by zero). Anyway, there is a load on both sides of the input filter cap. Its 100pF on the jack side and 10k metal film on the subwoofer amplifier and the input filter cap is in-between these two loads.
Inductance took a hike.

Yes. That 100pF value is a bit weak/conservative; however, the exact nature of the source device is known to only one person.

Even more interesting than these technologies is the vacuum tube based active system that the thread owner is creating to blend these little subwoofer amplifiers with his vacuum tube amplifier.
Once the vacuum tube amplifier is set free from bass duty, it may be capable of cleaner and more powerful output. I'd love to hear about this.

[ratza]

daniel, for me it's very obvious that you don't have a clue on what a low pass filter is and how it works, why do I wonder that you have no idea on how the whole circuitry works?

[coldcathode]

Daniel / Ratza

Let's not get into a "my chip is bigger than yours" debate over this. These types of discussions also go on "ad infinitum" in the tube/valve forums also.

I DO NOT use ANY modeling beyond a few programs that automate F3 points and plot some more complex load lines for my valve designs.

I instead rely upon the basic math models and mfr. data for anything I build.

There is however some subtle differences in resistor and capacitor properties which are "accepted" norms in the tube world. These I am sure have actual hard scientific data to back up in the SS world.

We (bottleheads) like to use carbon comp in applications where they are directly in the path of signal. Metal Film is used alot where accuracy is important with relatively small amounts of current.

We also like to over-rate the wattage since it imparts less noise (subjective but true).

I am running out right now but perhaps a little longer winded more detailed post of the intent for these chip amps along with some "source" info on the crossover/preamp etc would help.

[danielwritesbac]

Originally Posted by coldcathode

. . .
We (bottleheads) like to use carbon comp in applications where they are directly in the path of signal. Metal Film is used alot where accuracy is important with relatively small amounts of current. . . .

Accuracy is important also for power output, and that's why I used Metal Film for the feedback resistor on a subwoofer amplifier. Metal film is also good for input load.

Other resistors being big carbon will simply help the chipamp blend in system symmetry with the tube amplifier and it will do exactly the same thing for the chipamp that it does for the tube amplifier.

[danielwritesbac]

Originally Posted by ratza

daniel, for me it's very obvious that you don't have a clue on what a low pass filter is and how it works, why do I wonder that you have no idea on how the whole circuitry works?

Well, then, are these decent examples?:

Page 9 http://www.st.com/stonline/products/...60/tda2040.pdf

Page 10 http://www.st.com/stonline/products/...85/tda2052.pdf

Page 10 http://www.st.com/stonline/products/...9/tda2030a.pdf

[AndrewT]

which parts of pages 9 & 10 show that you understand how it works?

[ratza]

Actually I have a better question: is that a passive or an active filter?

[coldcathode]

Ok, Ok,

It looks like the peeing contest is on!

To "throw a wrench in the works" I have the following to add.

In looking over all this stuff it appears to me that no matter what using solid state components is going to look like I used "solid state" components. Since I feel that I can still work this "aesthetic" into the system I want to put together and since my electronics knowledge is focused primarily around vacuum tubes I think I will just do my own "interpretation" of an existing design.

I have an extensive "junk box" and supplies of oddball stuff so while I am thinking to build something like this:
click here

I can purchase the board for about $50 delivered and source the other components as needed.

The suggested PS for a stereo amp into 8 ohms is a 25V 300VA tranny.

I am thinking that four 50-60VA trannies with sufficient capacitance would work? One tranny for each Pos. & Neg. supply per channel?

A quick PS schematic is attached.

I am looking over the amp schematic next.

[Greg Erskine]

ooh,

The PSU schematic doesn't look right.

[coldcathode]

Originally Posted by Greg Erskine

ooh,

The PSU schematic doesn't look right.

Should the CT's be left out altogether? This is what I was thinking originally.