It was at 1khz, but I didn't have time for some investigation.. also in listening test was some hum in source signal.. I hope, that is my mistake. Today I will make next measuring, also I´ll try to mount capacitors for difficult load, if it help...
Yes, a mistake; it should be almost battlement square at 1KHz, Marcell..........
Good luck, check your transformer and power and signal wiring.
Cheers,
Hugh
Good luck, check your transformer and power and signal wiring.
Cheers,
Hugh
Today I had chance to look on my amp. So, I found, that both gate resistors was interrupted..It was my mistake I used 0,25w resistors, and thought, that there is no much current going to gates 🙂 I really don't understand, how could amp played without them 🙂
So, now is all right, and square is still fine at 20 Khz..(first pisture is at 10khz and second is at 20khz) I did some short listening test , and sound great... I am not able to assess, which is better 🙂 I think, that all amp which I already assembled, are great sounding ...
So, now is all right, and square is still fine at 20 Khz..(first pisture is at 10khz and second is at 20khz) I did some short listening test , and sound great... I am not able to assess, which is better 🙂 I think, that all amp which I already assembled, are great sounding ...
Attachments
I know, that movie from youtube by my phone have not no predictive value.. but, if someone interested...
Fetzilla - YouTube
Fetzilla - YouTube
Hi,
Can you measure the temperature of the chip and the heat sink? Mine gets quite hot.
I have no proper heatsink yet... but I can say, that this amp due bigger bias is relatively warm without source...
Thanks Hugh, I'm glad I chose to build tanto amplifier .. I like the idea that the PSU is directly part of the PCB amplifier ..
So, after a quick foray into SMPS powering my Fetzy, i've decided to give the linear supply a chance. The transformers are a pair of 160VA, 2x25V toroids from Toroidy.pl, however i have a question. One transformer feeding each board, as per the instructions. Does the phase matter though? I'm thinking no, but some have reported slight hum in their builds, maybe this is the source?
After being told that the transformer phasing and PSU phasing could be the cause of my reported hum, I tried a variety of rewiring options.
None sorted the hum in this amplifier.
It is still the noisiest power amplifier I have ever built. I cannot get the output noise below 0.3mVac, whereas all my other builds range from 0.1mVac to 0.0mVac using a DMM set to 199.9mVac and with the input shorted at the PCB.
i.e. the FetZilla is roughly between 10dB and 20dB noisier, than normal power amps including 3886 chipamps.
None sorted the hum in this amplifier.
It is still the noisiest power amplifier I have ever built. I cannot get the output noise below 0.3mVac, whereas all my other builds range from 0.1mVac to 0.0mVac using a DMM set to 199.9mVac and with the input shorted at the PCB.
i.e. the FetZilla is roughly between 10dB and 20dB noisier, than normal power amps including 3886 chipamps.
Andrew,
What sort of transformer are you using? And do you have good quality, clean AC at your mains?
I refute my experiences after the noise of the FetZilla. There is something wrong. My
FetZilla (which I subsequently sold three years ago before I became ill) was utterly quiet. I have had experienced saturated cores on toroidal transformers from China some time back and found that a better transformer completely fixed the hum issues. This is critical for the FetZilla supply since the quiescent current is heavy, 380mA, which brings out the transformer saturation issues, particularly if the mains voltage is a little high.
Kris,
I recently tried a smps on my commercial NAKSA 80. It really had a huge effect on the sound quality - and all bad. I very quickly returned to the linear supply, which I thought was expensive compared to a Chinese smps. However, I found that if I added chokes, both CMC and single ended, I found that the smps to compare with the linear supply I had to spend at least 30% MORE on the smps. Better to use an economical linear supply, with a good quality toroidal and quality caps.
Cheers,
Hugh
What sort of transformer are you using? And do you have good quality, clean AC at your mains?
I refute my experiences after the noise of the FetZilla. There is something wrong. My
FetZilla (which I subsequently sold three years ago before I became ill) was utterly quiet. I have had experienced saturated cores on toroidal transformers from China some time back and found that a better transformer completely fixed the hum issues. This is critical for the FetZilla supply since the quiescent current is heavy, 380mA, which brings out the transformer saturation issues, particularly if the mains voltage is a little high.
Kris,
I recently tried a smps on my commercial NAKSA 80. It really had a huge effect on the sound quality - and all bad. I very quickly returned to the linear supply, which I thought was expensive compared to a Chinese smps. However, I found that if I added chokes, both CMC and single ended, I found that the smps to compare with the linear supply I had to spend at least 30% MORE on the smps. Better to use an economical linear supply, with a good quality toroidal and quality caps.
Cheers,
Hugh
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I used a dual secondary Toroidy with the standard inter winding screen and a Guass band around the periphery.
OK, that should be fine if the core is good.
Does the amp produce hum if you reduce the quiescent to 100mA?
Ciao,
Hugh
Does the amp produce hum if you reduce the quiescent to 100mA?
Ciao,
Hugh
My findings as well, although i didn't go as far. I went back and reworked my PCBs today, there were quite a few changes. And i hit the singular snag with my boards, that the middle rectifier holes being just a tad too tight. After some sweating i just gave up and mounted that rectifier slightly high, should be fine.
The old .47uF Jensen copper PIO caps are on, and i came up with a neat way to keep them on the board, using some stuff i had around the house, will post a pic of that later. Also got around to swapping my 2SK170s of unknown Idss for parts with 7ma Idss, and fitted a regular diode instead of a LED for D3. Fingers crossed one or both of these things will alleviate my turn-on thump.
My wooden enclosure has gotten its first costing of shellac, so soon it will be "done"! Then it's single-malt time for sure...
after long time i had chance to continue with work on this amp... I started with my own made chassis 🙂
short movie
https://youtu.be/BVDWiV1qgVM
short movie
https://youtu.be/BVDWiV1qgVM
Attachments
Marcel,
Beautiful craftsman, very neat work and unique heatsinks........ it will NEVER get hot!
How does it sound? Do you make any observations compared to other amps you have heard?
Hugh
Beautiful craftsman, very neat work and unique heatsinks........ it will NEVER get hot!
How does it sound? Do you make any observations compared to other amps you have heard?
Hugh
This heat sinks are made by czech firm ČKD, usually for big rectifier 100 amp and more, for example for welding machine 🙂 Due bigger bias I decided to use this heatsink, second reason is that you can buy this for good price in our country 🙂
So, how does it sound....I think, we have very small nuances between well-designed amps... This amp have very clear sound, with good soundstage, and isn´t so aggressive like fet amp usually are ..I compared this amp with just finished Apex A14, which have little bit more bas, but isn´t so detailed ... but again, there are maybe some subjective feelings... maybe, when I already finished all my projects, I will do some big comparison.... 🙂
So, how does it sound....I think, we have very small nuances between well-designed amps... This amp have very clear sound, with good soundstage, and isn´t so aggressive like fet amp usually are ..I compared this amp with just finished Apex A14, which have little bit more bas, but isn´t so detailed ... but again, there are maybe some subjective feelings... maybe, when I already finished all my projects, I will do some big comparison.... 🙂
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