100W Ultimate Fidelity Amplifier

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apexaudio

apexaudio

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Joined 2010
FX7

FX8 without CCS
 

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xrk971

xrk971

Founder of XSA-Labs
Joined 2012
etsy.com/shop/XRKAudio
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AndrewT said:
I would like to suggest a few changes.
Omit C6 initially and test what it does after first build.
Replace C9 with a pair of inverse parallel 1n4148
Replace D4+D5 with a red LED to indicate ON. Select R9 to suit.

For C8=3u3F, then C5>175uF

Maximum reliable power is approximately: Sum of all output transistors Pmax @ 25°C divided by 4
i.e. one pair of irf240/9240 gives ~ 150*2 / 4 = 75W per channel.
Choose you supply rail voltage (and mains transformer) to roughly equate to that maximum power.
Click to expand...

AndrewT,
I am reading up on LED biasing and I suppose it is less noisy than a plain diode, but people have also recommended using a simple NiMH battery (self recharging) as the bias device and say it sounds even better. Any thoughts on rechargeable batteries as the bias on the LTP current sink?
 
prasi

prasi

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Joined 2014
sites.google.com/site/analogdesign1234/
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saikatbiswas82 said:
Looking at the post count it seems FX8 is getting very popular among DIYers.
Click to expand...
AX-11 has also been quite popular, so also the AX-14. Also there are many other popular amps by APEX like studio reference series and also the DC servo mosfet amp, etc.
FX -8 has received recent attention here for sure:).
 
prasi

prasi

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Joined 2014
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xrk971 said:
The sound quality is from my listening impressions with base FX8 on left channel and modified on right channel and I switch back and forth but using right input to amp at all times. Of course in mono is all that makes sense.

There is quantitative data in terms of frequency response measurement with calibrated mic at same position with same speaker, only amp changing. It is measurable difference in bass response and lower HD in mids and highs. For some reason, the lateral FETs have a rising distortion from 1k and up. The same board with the mods and hexFETs have lower distortion. This means it might have been rather high to appear at a speaker (>-40dB or 1%). The shape of the response is pretty much the same above 300Hz, with the hexFET more bass response below by about 1.5dB and deeper extension by a few Hz.

I really need an amp distortion analyzer and would like to make a DIY one somehow - suggestions welcome. I am thinking a USB audio digital interface with a resistor voltage divider network and measure signal on dummy resistor load vs a mic?

Regarding cost: MPSA42 is $1.00 for a bag of 50, genuine IRFP240 and IRFP9240 are $4.50 a pair.

latFET are $15/pair
Click to expand...
This could be a good method to compare amp FR, but always using the same speakers, speakers themselves behaving over entire audible spectrum. Ofcourse I am no expert or even an EE, can the same info be obtained from an oscilloscope or some other means? This could answer bass/ low bass/ low highs/ great highs, etc questions.
Reg
Prasi
 
B

benz2

Member
Joined 2016
prasi said:
Hi Ben and XRK,
That would be really nice. Mr. Mile can review it regarding which is the best variant and design. this is what this thread needs, a nice "Table of Contents" sort of.
excellent!
Reg
Prasi
Click to expand...

Yes! My "catalog" is simply a folder structure for all Apex Audio designs that I have encountered. Under each folder, I have DATED the images. In order to have something that is usable by our community, my perception is that we need a website that does something similar, adding verbiage, of course.

We see this approach from Pass Labs, etc.

Required Resources:

1) A website
2) One or more admins
3) Setup/Config data capture of "raw" information, scraped from the thread.
4) Additional input / refinement, particularly from Mr. Mile and other SMEs, including Terry and Prasi
5) On-going maint.
 
xrk971

xrk971

Founder of XSA-Labs
Joined 2012
etsy.com/shop/XRKAudio
Paid Member
Benz2,
Great that you have that, but for now, simply a listing of amp name, and hyperlink to schematic and pcb would be great. This would simply be a list administered by Apexaudio in post #1. As the OP, he has rights to update post #1 as often as he sees fit. Here is an example of how I provide an index with links for all my Foamcore speaker projects to give you and idea:

http://www.diyaudio.com/forums/full-range/223313-foam-core-board-speaker-enclosures.html

If you can provide APexaudio with a post showing the amp and links to schematic, pcb pdf, pcb sprint, pcb Gerbers, and BOM (if available) would be super.

Amp Name and version* / Date* / Schematic* / PCB pdf's / PCB Sprint File / Gerber Files (all, if applicable)

* minimum info is first 3 items

Thanks,
X
 
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prasi

prasi

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Joined 2014
sites.google.com/site/analogdesign1234/
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I have to agree with Still4given entirely:up::up::up:, ("enjoyment is in building and learning" , additionally in my case its -layouting:).)
Yes reading is good and helps one pick up itsy-bitsy things that helps one for life long in this hobby, especially thread like this one and slewmaster are gifts to newbies (eager to learn types). Consider this as an advice to all newbie’s from a newbie.:)
one can browse entire thread and then to quickly locate required amp is where an index helps. Especially for repeat visitors, it saves lot of time.
 
C

camelator

Member
Joined 2013
AndrewT said:
We either need a proper index, or separate Threads for each amplifier model.
Click to expand...

Hi,

+1 :)

as a lot of people, I would like to thank every contributors for this interesting thread, it give me appetit for the FX8 amplifier.
I come from Class D amplification.

I took me two days to read carrefully 1/3 of the posts :)
I would like to start to build a FX8.
I think I found the right gerber & schematic file
I was able to start a BOM project on Mouser that I'll share

I have few questions to start my project:

I read here about the FX100 PSU. Is it the more suitable/pricely PSU for the FX8?
Is it possible to use a SMPS?

Second question for XRK971:
Thx for your contribution here, as all your contribution it is very positive,
I would like to start building more amplifiers ...
I red somewhere you bought electronic components on alliexpress,
please, could you detail a little bit more? I found electronic components providers on alliexpress, but at this very first step I found the components don't look audiophile....
What kind of electronic components did you buy? Where ?

regards,
 
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