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Fetzilla Build Documentation

Yes, what are the attractions: cost/ size/ sound quality?

And Patrick your current thoughts re a further group buy?

Cheers

Look at the groupsbuy thread.Groupsbuy 5 is started.
My conclusion for now mids and treble are better more open and the bass section is changed different sound.Planning to order a second SMPS to see if there are any changes between the use of one SMPS fort two channels or 2 SMPS for each channel.
 
On the board there is a white line you can cut the board there or leave the psu caps out and the retifier diodes.This way you can solder a faston in place.
It all will be clear when you see the boards
 

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When you use the whole boards it is 23cm long.That's the minimum lenght you can take,when you gut the board both side it's about 15cm.My previous FetZilla board uses sinks of 30cm x 9cm and the heat was between 38 and 40 degrees celcius.Will also do a test with a 3mm thick alu. cover and bottom without any other sink.
 
Use the voltage drop to find the current.
That current should match suggestions for the in line device.

Multiply the current times the voltage drop and you have the dissipation.
Now multiply by a factor to ensure cool running. Anywhere from 2times to 20times.

Haven't you built one of these? Can you measure the voltage drop and tell us if 1/2W resistors are necessary?

thanks
 
Terry,
This is a big job. A lot of work to figure it out, particularly with a strong signal passing through it.
Have you built a FetZilla? Maybe....... how about you set it idling, then measure all voltages across each resistor, then, square each voltage and divide by the ohms of each resistor. This gives you the dissipation at idle, and it's very close to the highest value - with the except of the output source resistors, which should each be rated to 3 watts each.
Alternatively, built the thing, use 1/2W resistors suggested, and be done with it.....

Cheers,

Hugh
 
Haven't you built one of these? Can you measure the voltage drop and tell us if 1/2W resistors are necessary?

thanks
I have built and listened to two of these and listened to my NFetZilla.

The NFetZilla does not have the noise problem that the Group Buy PCB has.

NFetZilla is the inverted version with all N and P swapped. I posted a sch a long time ago.
 
Terry,
This is a big job. A lot of work to figure it out, particularly with a strong signal passing through it.
Have you built a FetZilla? Maybe....... how about you set it idling, then measure all voltages across each resistor, then, square each voltage and divide by the ohms of each resistor. This gives you the dissipation at idle, and it's very close to the highest value - with the except of the output source resistors, which should each be rated to 3 watts each.
Alternatively, built the thing, use 1/2W resistors suggested, and be done with it.....

Cheers,

Hugh

Hi Hugh,
No, I haven't built a FetZilla, I am on this list for the latest Group buy. Please don't think I am trying to cause trouble. I am just trying to learn. I have no background in electronics aside from what I have learned here. I have built about 12 DIY amps so far and I learn a little more with each one. This is the first time that I have seen an amp that calls out all 1/2W resistors so in an effort to learn I have asked. It's not a big deal to buy 1/2W resistors, they are the cheapest components in the amp. I was just curios why this amp required them when all of the other amps I have built did not.

Hi ajst2duk,

Thanks for the insite. ;)

I have built and listened to two of these and listened to my NFetZilla.

The NFetZilla does not have the noise problem that the Group Buy PCB has.

NFetZilla is the inverted version with all N and P swapped. I posted a sch a long time ago.

Hi Andrew,

This is the first I heard of this amp being noisy. Maybe this is a bad idea for me.

Thanks, Terry
 
Terry,

In the DIY world, people search the internet to find the best design they can find. The problem is that other people's assessments of the sound quality are variable, and erratic; we really can't know if other's opinions are legit or complete. Furthermore, if you don't have the complete technical suite you don't really know precisely what you are looking for in the schematic, and you can't be sure if negative comments are technical, or sonically, or based entirely subjective. Finally, there are lots of people who comment on everything they say, and publish their opinion gratuitously, and sometimes they have strong prejudices that often discourage people from building.

My suggestion is to look for strong, consistent and thorough documentation. Very few schematics on the net carry full documentation - BOMs, building instruments, pcb designs, gerbers, and subjective comments from builders. All of this is done for the FetZilla - I know because I wrote most of it. This is try of the VSSA, the Honey Badger, and most of the DIYaudio projects as well. I spent many years in technical writing, and my instructions on the FetZilla thread are detailed and carefully assembled. Because of careful proofing, all my documentation is now debugged.

Nothing is ever perfect. There are holes in everything, and if the designer is not liked, or regarded as an idiot, there will be trenchant criticism. People are always criticised if they produce anything; it is the human condition. Fortunately there are five minds in the FetZilla design project; Lineout, Greg, Mike, Paul and me. No one individual can be singled out as the designer; it is a 'committee' design. Many people say it is a high end amplifier, and certainly it's very simple, and integrated on a single pcb. Perhaps it is a camel? You could do well building the FetZilla, it will not disappoint.

I didn't notice any 'noise' during my testing. It's certainly better than 100dB below at idle. If you decide to amend it to the NFetZilla, be sure that the documentation is thorough and you know exactly what you are doing during the assembly.

All the five people in the design process of the FetZilla gave their time gratis. It is completely free of design cost, like most of Nelson Pass' designs. This is a very stable, solid product and I commend it to you. It is very musical. But you have to listen to it for at least a couple of weeks to come to a considered opinion.

Fortunately it's not expensive to build!

Cheers,

Hugh
 
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Hi Hugh,

Thanks for caring enough to listen to my concerns and reply. I do plan to build the FetZilla. I have been pouring through the various threads about it to try and get a handle on it but you know how that goes. With a project like this with so many guys giving technical input throughout, it becomes hard to remember which was idea casting and which was actually incorporated into the design. I will keep reading and hopefully by the time I have the boards in hand, I won't have so many questions.

Thanks again, Terry
 
My pleasure, Terry. You are a good guy, and like me, you have come through a health issue. Time is an issue at our age. I look back to my time with the FetZilla, and I'm proud of what we did.

Meanman is a wonderful fellow, and very, very honest and direct. You need to know people over at least a year on the net to assess people; Patrick is a lovely guy and his recent work with SMPS for the FetZilla is very useful and helpful, simplifying assembly.

The problem with all these circuits is that THD, FR, slew rate, etc do not indicate how they sound. You have to build it and listen to it yourself. This is the LAST thing you do over a long project. This is frustrating, because conception on a napkin in a café to a final assessment over a long listening session can take a long, long time. My NAKSA series consumed almost two years. This is a very long gestation.

Good luck with your project!

Ciao,

Hugh