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Swordfishy/ASPEN FETZILLA power amp

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#705
Alfia,

If I may offer some advice.....

Don't be too fastidious, trying constantly for perfection. This is the road to paralysis by analysis. Greater designers than you and me are behind this amp; it has literally hundreds of good brains in it when considered from the POV of audio evolution.

Just build it as is, then once you have it going you can make the changes. It is fairly uncritical of passive components; it relies mostly on the topology and the choice of semiconductors for its performance.

Yes, it is very good sounding as it is, no question, and the parts specs are reasonably prescriptive so don't be too fussy!

Good building,

Hugh
 
#707
Hi Do,

Quick answers:

P1 (BIAS current) is 200 ohms (200R)
P2 is 500 ohms (Bootstrap voltage adjust, although marked at 200R in error)
P3 is 2K (Offset control)

C3 is offset voltage reference smoothing, NOT critical (electro)
C9 is bias generator smoothing, again not critical (electro)

General purpose in Panasonic electro range (all quality caps) are just fine here for both.

Cheers,

Hugh
 
#708
syklab said:
Hi Mike and Hugh,
Thanks for your advise. I am tyring to gether which parts are more critical and can be benefit from further enhancement on components selection. Still learning and have a long way to go.
Click to expand...

One point that may be useful to state.

Hugh & I have developed different versions from the basic idea of this amp based on our personal preferences. Each of our designs are more or less complete & tested now and I think each of them work well in their own way ( Although neither of us has heard the others design yet ! )

You have asked above about a mod I proposed from my version that I'm assuming that you are planning to use in Hugh's version and Hugh has kindly asked me to comment on this in his thread. In this case I think the mod will transfer across without any engineering or subjective issues - just a matter of preference.

However, I would advice some caution about "mixing & matching" different design elements between the two designs unless you think the whole thing through very carefully and are prepared for thing to go wrong.

For instance. Hugh's design benefits sonically from a bias spreader bypass cap. In my design I heard no audible benefit from this and if one is applied the amp will almost certainly oscillate.

I don't want to discourage you from experimenting - just wanted highlight the reality of working outside the security of a finished design.

Hugh - I hope you agree with these sentiments

cheers

mike
 
#710
Fuse holder

Can anyone point me to a part number at mouser for the fuse holder...?

I've already been searching long enough and would appreciate a little pointer here!

Hugh, for the four 0R15 2W resistors to be mounted on the underside of the board, I was looking into SMD parts but all I could find was current sense or wirewound type... No metal film type.

I was thinking of Mills MRA-5 instead but the height might be to much and obstruct the mosfets...

Here's the SMD parts. I woudn't want to neglect sound quality at all. Do you see anything in the 8 pieces listed or should I use through hole type?
Mouser Electronics - Electronic Component Distributor resistor

One last question... Which of the resistors are critical ones. I would like to get higher quality parts for those.

Thanks
Do
 
#711
Do,

I buy standard M205 fuse pcb mount clips at my local wholesaler, Rockby Electronics at Rockby Electronic Components. They will send by mail order to Canada no problem. Almost 37,000 are available here in sunny Oz!! Here are the details:

Stock No: 14926
Description: PCB Fuse Clip To Suit M205
Qty on Hand: 36746
Pricing:
10 up: $0.140
100 up: $0.061

The flat smd resistors are thick film, in fact, and made by Vishay-Dale. They are WSR2 4527 and WSR3 4527 series. I try to get the WSR3, but the WSR2 will do in a pinch.

However, either carbon or wirewound is OK in this application. They are around 3mm thick.

I use good quality metal film resistors, mostly Philips and Beyschlag, throughout the amp. They sound just fine!

Hope this helps,

Hugh
 
#714
AKSA said:
Do,

I buy standard M205 fuse pcb mount clips at my local wholesaler, Rockby Electronics at Rockby Electronic Components. They will send by mail order to Canada no problem. Almost 37,000 are available here in sunny Oz!! Here are the details:

Stock No: 14926
Description: PCB Fuse Clip To Suit M205
Qty on Hand: 36746
Pricing:
10 up: $0.140
100 up: $0.061

The flat smd resistors are thick film, in fact, and made by Vishay-Dale. They are WSR2 4527 and WSR3 4527 series. I try to get the WSR3, but the WSR2 will do in a pinch.

However, either carbon or wirewound is OK in this application. They are around 3mm thick.

I use good quality metal film resistors, mostly Philips and Beyschlag, throughout the amp. They sound just fine!

Hope this helps,

Hugh
Click to expand...

Their minimum order is 50$ Australian. I don't have that many FetZilla amps to build 😉

I will continue my researches

If anyone have a part number at Mouser it would be great 😀

Thanks
Do
 
#717
Hi Syklab,

That's $HK8.13 to the AUD, so these are around a buck each in my money - expensive, but very good quality resistors.

Woody,

These fuse clips are a standard item to hold ANY round fuse, so they should be available just about anywhere. I can't see that if they are available in Australia, no doubt, like most electronic components, imported from China or Taiwan, then they should be readily available elsewhere. Minor dimensions may be different - legs thicker, distance apart etc - but they are made of soft metal and easily filed/bent. If things are difficult, you can remove one leg, solder in only one, but make sure that the base of the clip is firmly soldered to the pcb. That should do it!!

Cheers,

Hugh
 
#718
C5* 47pF 300V silver mica C6* 22pF 300V silver mica

Thanks all for the help!

If I'm not going to drive heavy load speakers like ES or others, the following parts should be omitted:

C5* 47pF 300V silver mica
C6* 22pF 300V silver mica

Are those to be bypassed or simply not populated? And would it simply be ok to include them anyway for regular load or not recommended?

Thanks
Do
 
#720
Yes, Do, Andrew is 100% right.

Delete them altogether, they are only required where phase shift, like Electrostatic Speakers, is a serious issue. With normal dynamic cone speakers, no problem at all providing the crossover is well designed.

Putting them in will slightly slow down the presentation, less than optimal.

Cheers,

Hugh
 
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