I pulled the two output transistors off from the 1st amp that is not working and installed it on the second amp. This one is built as designed - no LED's and all resistor values are as shown on silkscreen including 47R for the VAS transistors. Fired it up and adjusted bias to 100mA. It is playing now but I would say it does not sound clean. Like very audible distortion. So I took a frequency response measurement with my speaker using same setup used in this thread and there is a sharp 1.54% H2 distortion peak at 104Hz when everything else is typically 0.2% to 0.4%.
But at least that terrible scratchy popping is gone. So I just need to go through and replace all the actives on the first amp and go back to stock resistor values.
Here is measured distortion from speaker:
In comparison to other amps:
DC offset is good at -3mV.
Edit: maybe there is something to burn-in or breaking in, after playing for good 30 minutes, the 104Hz H2 peak is gone now...
But at least that terrible scratchy popping is gone. So I just need to go through and replace all the actives on the first amp and go back to stock resistor values.
Here is measured distortion from speaker:
In comparison to other amps:
DC offset is good at -3mV.
Edit: maybe there is something to burn-in or breaking in, after playing for good 30 minutes, the 104Hz H2 peak is gone now...
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Terry,
Well one amp works and the other one seems to have unending problems. Both are using same parts. Are you doing the Bimo mod AX11? That one is different from regular AX11. The output transistors (real 2sc5200 and 2sa1943's) are shared on both boards (removed from one and installed on second), so all that remains are the 2n5551, 2n5401, and BC550's. Those have worked on other projects and come from same bag as well. The BD139/140's also came from same bag. It's just time to go in a change out all actives and see if that helps.
Well one amp works and the other one seems to have unending problems. Both are using same parts. Are you doing the Bimo mod AX11? That one is different from regular AX11. The output transistors (real 2sc5200 and 2sa1943's) are shared on both boards (removed from one and installed on second), so all that remains are the 2n5551, 2n5401, and BC550's. Those have worked on other projects and come from same bag as well. The BD139/140's also came from same bag. It's just time to go in a change out all actives and see if that helps.
Hi all, I have just come across this forum and was wondering the thread title is 100w ultimate fidelity amplifer. Are the thread posts about developing one particular amplifer? As I see quite a few circuits shown. Are the posts from many uses on what they believe is the ultimate fidelity amplifer? Are there any performance numbers (THD-1 and THD-20) both from the spice simulations and real life?
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This Thread became such a mess of mixed up amplifiers that they finally had to admit it needed an index in a separate Thread.
http://www.diyaudio.com/forums/soli...pex-audio-amplifiers.html?highlight=apex+100W
http://www.diyaudio.com/forums/soli...pex-audio-amplifiers.html?highlight=apex+100W
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Welcome aboard Stuart. Spend some time reading and you will see that almost all designs proposed by Apex Audio gets built and tested. Some are more popular than others. They all have a common thread or philosophy: simple and good sounding with easy to find and low cost parts. If you want an easy to make and super sounding amp let me recommend the FX8 and the FH9. Gerbers are available and they've been well tested. Apex comes up with a new amp maybe once a week. If a design looks cool enough someone will make a layout. Then someone will etch boards and build. It's sort of like the never ending story because the "Ultimate Amp" is the mythical destination, and the 45 or so plus amp designs here are the road to that goal. Along the way there are many fine sounding designs. If you enjoy soldering and trying a new design every few weeks - this is the place. This is a real thread where work gets done though - it's not one of the other high view-count threads where a couple of characters ramble on about anything and everything but no real projects result. There are probably literally thousands of amps that get built from this thread by folks all over the world. It's probably the most active "real building" thread in diya.
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its what I heard from others, small signal transistors cost a lot less in US from mouser if you buy in quantity+ have free shipping , why go for aliexpress ? You had said previously that digikey parts that you have also originated in china. Reputed ones like digikey, element14, RS components will buy from manufacturers directly with manufacturer's quality control practices in place for a plant in china. Having a manufacturing plant in China is very different to having a supplier from china sell you. My friend has worked for european MNC in a plant in china, they have very strict manufacturing practices+QC, just like parent company.
One has to understand that there are talented stamping/ cloning artists there + sellers might be re-selling reject parts (yes, people with right connections have access to reject parts, I know a live example in India, in case of engine oils. I saw a photo from Ostripper somewhere, where it was saying ELNA or Rubycon 10000 uF on top shell, but had tiny 220uF or a 470uF inside. its simply unbelievable, the extent of cloning/cheating!. in this thread, someone had posted a pic of 2SK1058 with Toshiba stamped on top (I am sure the cloner must have lost his job
after the first batch was produced).Just thought to share my
for others who want to avoid pain and frustration. not everything is bad on that site, but one should not be unlucky to have bad parts, either one amp works=layout is ok, you should sort out problems with active and or passive devices, if any.
reg
Prasi
Point taken, Prasi and Terry...
I am just a sucker for good deals like qnty 100 x 2N5551 for $1 shipping included. I honestly believe those small signal transistors are fine and a lot of this initial problems I am having is resulting from swapping out one of the 1N4148's for an LED which then required changing the several resistors to change current supplies to the IPS and concomitant change in Vbe resistor and so on... I will live without an LED is probably the best solution.
I am just a sucker for good deals like qnty 100 x 2N5551 for $1 shipping included.
I honestly believe those small signal transistors are fine and a lot of this initial problems I am having is resulting from swapping out one of the 1N4148's for an LED which then required changing the several resistors to change current supplies to the IPS and concomitant change in Vbe resistor and so on... I will live without an LED is probably the best solution.
Don't make an adjustable PSU - too complex and not needed IMO for these projects. A 35v rail one will let you run 95% of the amps on this thread. So you need a circa 250VA to 300VA 25vac toroidal transformer. Then qnty 4 to 6 4700uF caps and 4 diodes for a rectifier. You can make nicer CRC supplies or CRCLC supplies later but just 4 diodes and 4 to 6 big 4700uF 50v caps will get started. From the PSU provide the usual Faston quick connects for the power supply and ground lines as all the amps use these connectors and will let you swap out amps in about 45 seconds. Very convenient and very secure and reliable connections.
Apex Audio (aka Mr. Mile) only posts schematics and sometimes a photo or two of his own builds. It's the user community on the thread who then collectively develop layouts, simulations Spice files, Gerber files, etc. So if you want to see an amp sing, you can either show why that amp is interesting to entice one of the expert members who do fine-fine looking layouts to make one (seriously, these guys are super talented and it is literally a work of art that is produced). Then you can make the PCB by sending the Gerber that the layout artists produce to an online fab shop (PCBway, Seeedstudio, etc.) or be handy with caustic muriatic acid and peroxide and etch and drill your own PCB's. Then solder it up and test it.
no need to worry about THD if its your first amp. Chances are you wont hear a difference between any of the amps posted here.
my advice would be, build the FX-8, that has many admirers here recently and is very small, simple and rugged amp. someone like xrk might have spare PCB's remaining from his build too, so your work is half done.
For PSU, see some builds/ schematics here on this site. Then just get some big caps, a rectifier, some connectors , and wire accordingly and you are done.
like x says, 250 to 300VA 24 or 25VAC center tapped transformer would be more than enough for a stereo set of amps that gives 100W/4ohm/channel.
If you need any advice, someone / Mr. Mile will chip-in.
All the best!
reg
Prasi
Point taken, Prasi and Terry...
I am just a sucker for good deals like qnty 100 x 2N5551 for $1 shipping included.
me too!!
send me the link!!.. just kidding!
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Stuart,
If you want to get an impression of what some of these amps sound like, check out this thread:
http://www.diyaudio.com/forums/solid-state/295286-virtual-audition-very-simple-quasi-mosfet-amp.html
The FX8 Bimo mod, and the FH9 xrk mod are tested and sound clips recorded under controlled conditions. You can compare with several other highly regarded amps on this forum.
Prasi's recommendation to go with FX8 is excellent and indeed it is an easy to make and robust amp. It will basically run the first time you fire it up - but it uses rather hard to find (genuine) lateral MOSFETs (the ubiquitous Hitachi or Renesas 2SK1058 and 2SJ162). The FH9, on the other hand, is based on same topology as FX8 but uses less expensive and easier to find hexFETs (IRFP240 and IRFP9240 - Vishay are my favorites). They are almost indestructible provided you don't zap them with static electricity.
Thanks for all that great advice I'll do just that then. Do you know if someone has made a PCB for one on the forum with gerber file and scamatic and photos of the finished product so I can follow something as this is my first build.
Once again thanks for all that advice. Really appreciate it.
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Links to Gerber files for FX8 and FH9 in Directory thread. The FX8 50mm will allow you to get 50mm boards made which cost $10 for 10. Although nowadays PCBWay will do 100mm boards for $10. The FX8 Bimo mod is the best FX8 for sound quality. The FH9 is also there in the directory and is the less expensive amp to make as the output devices are less expensive. Again, all in the directory thread index.
FH9 Gerber:
http://www.diyaudio.com/forums/soli...imate-fidelity-amplifier-746.html#post4718422
Upload the above Gerber to PCBWay and $10 for 10 boards plus $14 shipping via HK post.
BOM:
http://www.diyaudio.com/forums/soli...imate-fidelity-amplifier-799.html#post4774271
Fully tested and definitely works as laid out above:
And if you crave more power, swap out the power rail caps for 63v rated ones and swap out the BD139 and BD140 for KSC3503 and KSA1381 and you can use a 53v rail supply for a 120w amp. Aka FH9HV:
And here is what it sounds like:
http://www.diyaudio.com/forums/soli...very-simple-quasi-mosfet-amp.html#post4797063
FH9 Gerber:
http://www.diyaudio.com/forums/soli...imate-fidelity-amplifier-746.html#post4718422
Upload the above Gerber to PCBWay and $10 for 10 boards plus $14 shipping via HK post.
BOM:
http://www.diyaudio.com/forums/soli...imate-fidelity-amplifier-799.html#post4774271
Fully tested and definitely works as laid out above:
And if you crave more power, swap out the power rail caps for 63v rated ones and swap out the BD139 and BD140 for KSC3503 and KSA1381 and you can use a 53v rail supply for a 120w amp. Aka FH9HV:
And here is what it sounds like:
http://www.diyaudio.com/forums/soli...very-simple-quasi-mosfet-amp.html#post4797063
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