100W Ultimate Fidelity Amplifier

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#13,662
anyway I checked prices, here is a screen shot for 20 PCBs , around 48 USD total with Fed Ex shipping to India. But our customs dept is active these days and charge a hefty duty especially after the border issues.
So these days I am avoiding ordering from "China"
 

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#13,663
Hello Prasi, how is this FH9 different with the other XRK mod based on which I built couple of amps for friends? I guess that was called as FH9HV hexFET. It is an awesome sounding amplifier using 35v transformer almost giving 100+100w. I thought even the FH9HV was laid out by you 🙂

Thanks
 
#13,666
If memory serves me, the FH9 was XRK's work around to the FX8 so he could use the cheaper HEXFETs for the output instead of the Lateral MOSFETs. I guess it is getting increasingly more difficult to get laterals these days. The FX8 was one of the best sounding small amps I've built.
 
#13,667
prasi said:
Thanks,
these are stereo boards, no need to cut in half.
Simple salvaged MS chassis of an old 5.1 receiver would do perfectly.
I even plan to use the heatsink from the old receiver.

you can even plan for pesante 3U kind of chassis which is cheaper compared to dissipante. Pesante 3U – diyAudio Store
if you have a single heatsink of 100mm height, you can mount it inside the case near the holes/slots for heat dissipation.
Click to expand...
I am considering the following chassis from ebay with external dimensions:245x213x70mm. (internal width: 162mm and outside width: 213mm)
 

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#13,668
Looking for suggestions on what Apex Amp to build?

Hello,

I am looking for help on deciding what Apex amplifier to build for my third amp build.

Ideally I would like an amp to be 100 watts at 8 ohms and be able to handle a 4 ohm load. I build speakers for a "main" hobby (lol) and I want to be able to drive anything I build.

Low noise and 20-20Khz as flat a response as possible is very important.

Preferably something with easy to source parts (no obsolete or hard to find transistors), not necessarily inexpensive and with an existing BOM. Something with a track record of successful builds by relative noobies to the amp building world.

Ordering boards is not a problem, I already have Prasi's CRC power supply boards and Mark Johnsons soft start boards. I also built Marks Quasimodo board and know how to use it with an Oscilloscope.

I can solder and "kit out" an enclosure properly.

The first amp I built was Toms Neurochrome LM3886DR with Power-86 Power Supply Board and the super clear instructions were very helpful. Toms amp is very nice, but not enough power, I don't like the idea of an amp playing on "8".

Next I built an LM1875 amp from a pair of those $2.00 ebay kits (just used the boards, bought all new legit parts) and used a premade Aliexpress SMPS. It is a little noisey with the SMPS, but this was purely a building exercise and not because I needed this amp.

There are *so* many Apex amps on here to chose from,

What would you suggest?

Thank you,

David.
 
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#13,669
Search for AX-14 (BJT) or FH11 or FH12 (MOSFET). Both have 2-pair outputs and all easy to source parts. You can use the generously provided gerber files to order your own boards and there are BOMs for them as well. If you like tubes or a laid back sound go for the mosfet if you like a lively and open sound go fir the BJT option. Both sound great.
 
#13,670
hanair said:
I am considering the following chassis from ebay with external dimensions:245x213x70mm. (internal width: 162mm and outside width: 213mm)
Click to expand...

the height is only 70mm, so you wont be able to fit it , you need to go for some other design or cut the pcb right down the middle but that would be a hassle.

another design for Apex XRK FH-9 is shown (attached) , although shown as side mounted, you can mount transistor vertically on heatsink.

pr like Terry says go for FX-8, its one sweet sounding amp in 50 x 50 mm size , you find gerbers and stuff somewhere in the thread, but uses lateral mosfets which are hard to source or costly.

There are many more apex amps , compact but great sounding like FX-11 or AX 14 etc. with BJT instead of mosfet
 

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#13,672
DaveFred said:
Hello,

I am looking for help on deciding what Apex amplifier to build for my third amp build.

Ideally I would like an amp to be 100 watts at 8 ohms and be able to handle a 4 ohm load. I build speakers for a "main" hobby (lol) and I want to be able to drive anything I build.

Low noise and 20-20Khz as flat a response as possible is very important.

Preferably something with easy to source parts (no obsolete or hard to find transistors), not necessarily inexpensive and with an existing BOM. Something with a track record of successful builds by relative noobies to the amp building world.

Ordering boards is not a problem, I already have Prasi's CRC power supply boards and Mark Johnsons soft start boards. I also built Marks Quasimodo board and know how to use it with an Oscilloscope.

I can solder and "kit out" an enclosure properly.

The first amp I built was Toms Neurochrome LM3886DR with Power-86 Power Supply Board and the super clear instructions were very helpful. Toms amp is very nice, but not enough power, I don't like the idea of an amp playing on "8".

Next I built an LM1875 amp from a pair of those $2.00 ebay kits (just used the boards, bought all new legit parts) and used a premade Aliexpress SMPS. It is a little noisey with the SMPS, but this was purely a building exercise and not because I needed this amp.

There are *so* many Apex amps on here to chose from,

What would you suggest?

Thank you,

David.
Click to expand...

A23
 
#13,673
prasi said:
Here are final files and gerbers
Click to expand...

I got a quote for the quoted stereo board from my local board house for usd 3 per pcb. if people want me to go ahead with ordering and supply, I can place the order.
If interested, please PM me your quantity (in number of PCBs) , paypal email and name+ complete postal address+ country. Once the PCB are delivered to me I will send out a Paypal invoice; once paid , pcbs will be shipped out via tracked post(doesnt track to usa, canada, australia, etc). [Shipping / packing and paypal charges extra, which is generally about 6-8 usd for 2 pcbs] .Request not to post your pcb requirements / questions regarding pcb/ shipment in this thread to keep it clean.

pcb specs
Stereo (2-ch) Apex -XRK mod FH-9 , size: 100mm x 100mm, 1.6mm thick FR-4, double sided, green mask, white silk on top, 35 um copper, HASL, qty of order will be limited (30-50 pcbs, if i can gather so many interests) and first come first serve basis. If cant get to that qty, I wont place the order.


Note: DIY member xrk971 has been running a GB in the GB section for a mono version of the amp here
FH9HVX - Budget Conscious 100w Class AB for Lean Times
people should take a look at it. It’s available immediately from XRK’s online shop.
Posted with permission from xrk.
 
#13,675
#13,677
You are right, Stocktrader. The schematic for the stereo FH9 is missing a 22k resistor to ground at the base of T7. The mono board a few posts up has it though.
Thanks for pointing that out. I have added an LED in series with that 22k resistor to GND and it gives a good indicator that the amp is on, and that the CCS is working.
 
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