Fetzilla Build Documentation

[AKSA]

MM,

Nice work! Now, do you have it up and running yet?

How is the sound quality?

Hugh

[meanman1964]

The amp is ready for use and I'm happy with the sound.I'll try to explane how it sounds not easy cause english isn't my native lanquage.First you need to know,for me everthing must be in balance.I don't like the hights are too present but when I disconnect the tweeter I need to say Hé the hights are gone.That's why I love my Blame ST from Carlos so much good bass and for me nice hights and relaxed sound.The test is done with vintage speakers the DM14 of B&W a closed cabinet with two 6,5 inch woofers and a 28mm dome tweeter.And now my Fetzilla compaired with the Blame ST even stronger dry bass regarding to that my opinion is the Fetzilla wants bigger speakers.It produces realy puchy bass.The hights are more present but very clear and crispy but cause the puchy and strong deep bass all in balance.The Fetzilla deserves good flourstanding speakers which can cope the bass of the Fetzilla.Now it's time for a high power Fetzilla,I realy like this amp too and I'm happy building it.
Hope this explaines a bit what I think about this amp.

[AKSA]

For someone says he's not comfortable with English you have done bloody well......

Thanks man!!

If the bass is a bit dry and punchy, try this.

Put a 0.22R resistor between the crossover and the BASS driver on both your speakers.

This will loosen up the bass, make it sound huge, but take away some of the dryness.

Then you should have the perfect amplifier with matching speakers!!

Cheers,

Hugh

[meanman1964]

Hugh,I like the bass the way it is.You just can't believe the bass these DM14 produce with the Fetzilla amp.Maybe I don't use the right words but the bass is realy tight also some of the advantage of a closed speaker.Also planning to build a large speaker system,wondering how the Fetzilla behaves then.The Fetzilla is here to stay.Hugh,thanks for this amp!!

[chlorofille]

MM,

Thanks, great review. Looks like you have a winner there.

[meanman1964]

Certainly it's a winner, I realy hope someone designs a 150Watt/8 Ohm Fetzilla.The only thing that bothers me is the power up dump.Planning to make a speaker delay.

[AKSA]

MM,

I seem to remember power up dump is infrasonic and around 3V. This is trivial and won't cause any issues for any driver I know about. It's a good indication that the amp is on and ready!!

A speaker delay will involve a relay. Choose very carefully - the one to use is the Amplimo, made in Nederlands, but it's expensive. This relay has two parallel contacts; one tungsten alloy, the other gold faced. The hope is this will prevent degradation of the music signal.

A 150W FetZilla would not be too difficult, requiring only three pairs to the output stage. The existing VAS stage would need revision, however, more current, and possibly a bipolar VAS transistor.

Thanks for your enthusiastic review. I would say you are about the seventh or eighth builder to report his thoughts on the sound - lots sold, but not many built, I gather.

Cheers,

Hugh

[meanman1964]

Hugh,
I've 5 of those Amplimo relais,for me it isn't a big deal the power up dump but in November there is a DIYaudio meeting Holland and I know people will ask about the power up tumb.That's the reason for my concern in post 76.

[meanman1964]

I'm planning to test a tube PreAmp Driver with the Fetzilla OK or not?As I recall it has a voltage swing of 30 Volts

[ncc]

It's been a while and I've not finished my Fetzila due to lack of time and it did take sometimes for me to collect all needed parts.

A few day ago, I started building the amp. Yesterday, after I finished soldering everything on the PCBs. I switched on the power, I use a variac and set the (main) input voltage at half (110V)(the transformer secondary voltage is only 12V AC) to see if something go wrong and actualy something did go wrong (I shoud have used a bulb in serie with the amp as someone advised on this topic). After I turned the power on, the toroid hummed loudly and it seemed that I got a short somewhere since I saw smoke come out below the PCB, from the position I came out, It seemed to come from the metal oxide resistors which are mounted underboard, it happended to both channels.
I turned off the power immediately to prevent further damage. I guess that I did something wrong. After that I tested the fuses on PCB and they all intact.

Attached here are the pics of my PCB. Coud you please take a look at them to see if I put everything in correct order.
As you could see, in the power supply section picture. I did not mount the diodes optimally as I soldered them with the metal tab facing in instead of facing out but I only realised it after soldering them in positions. Actually, I tried to separate them and not to let their metal tab to touch each other.

Thank you in advance.
ncc