An Pass F5 Build

O&B HCA300 Power Amplifier
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kroyin

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Gentlemen please go easy on me :-)

This is just a 1 channel experimental Proof Of concept. The final build will be with fresh boards & fresh components.

So the setup

kry3732.jpg




Testing with Dinky HT speakers & mobile phone before i connect the amp to my Sonodyne 2504 (91db sensitivity) followed by my Troel Gravesen Nomex speakers (90db sensitivity).

The toughest part is drilling holes in Aluminum Heatsinks with <3mm bits. After a lot a trial & error (as evident in the pictures) and broken drill bits i got the formula right.

kry3733.jpg


The amp board with scarred heatsink. The board has the following characteristic
---No current limiting component (will use them in final build)
---No thermistor (will perhaps not use them in final build)
---Green Resistors are 220E 5W (use them rather than 100ohm to get 6db more gain)
---Red Ones are 1 Ohm 5 watt (original circuit calls for .47 ohms but i had burnt through them :-)). Used V=IR to set voltage so that I=1.2Amps
---Had recycled through 1 FET, Couple of resistors,1 trimpot during various experiments.

And the powersupply

kry3734.jpg



About sound... ooh whao (but remember i am coming from a AVR), so for most of you guys the WOW factor would be less. If i have to quantify the bass is is deeper and tighter .. to top opens up very nicely... I cant describe what i hear but it is damn good.

Volume is adequate, in fact i keep on searching for Volume control, but have'nt build one yet :-)

I'll add details more details over the long weekend.
 
Last edited:
Last edited:
kroyin said:
Gentlemen please go easy on me :-)

This is just a 1 channel experimental Proof Of concept. The final build will be with fresh boards & fresh components.

So the setup

kry3732.jpg




Testing with Dinky HT speakers & mobile phone before i connect the amp to my Sonodyne 2504 (91db sensitivity) followed by my Troel Gravesen Nomex speakers (90db sensitivity).

The toughest part is drilling holes in Aluminum Heatsinks with <3mm bits. After a lot a trial & error (as evident in the pictures) and broken drill bits i got the formula right.

kry3733.jpg


The amp board with scarred heatsink. The board has the following characteristic
---No current limiting component (will use them in final build)
---No thermistor (will perhaps not use them in final build)
---Green Resistors are 220E 5W (use them rather than 100ohm to get 6db more gain)
---Red Ones are 1 Ohm 5 watt (original circuit calls for .47 ohms but i had burnt through them :-)). Used V=IR to set voltage so that I=1.2Amps
---Had recycled through 1 FET, Couple of resistors,1 trimpot during various experiments.

And the powersupply

kry3734.jpg



About sound... ooh whao (but remember i am coming from a AVR), so for most of you guys the WOW factor would be less. If i have to quantify the bass is is deeper and tighter .. to top opens up very nicely... I cant describe what i hear but it is damn good.

Volume is adequate, in fact i keep on searching for Volume control, but have'nt build one yet :-)

I'll add details more details over the long weekend.
Click to expand...

Congrats for your attempt and determination. Long way to go before the build looks good and SAFE...

Cheers.
 
Build complete :-)...
got parts from digikey,jfets from Spencer...dropped office on Friday :-)...listened throughout saturday & sunday...sounds fabulous
 
congrats. That was fast! You got components and assembled in a very short period. How much time/ research did it need?

Please share more on how you got the components, how much money and time you spent on this project, so that more people can be inspired to take it up. Also share some pics.

Anilva - what are the safety issues we need to address in the amp?
 
In my book Anil is our ustaad on this..He has done it elgantly and well, and it sounds very nice provided of course, the speakers match the amp. This is a good project for someone in India to diy.
 
Ok this is going to be long one.

My research & component gathering began in late January. Initially i had thought of building one channel as a Proof Of Concept (the result of which you see above posts). While i'll post pictures of the completed channel it has to wait for a few days. Now in the nutshell about what i have learned....

Speakers

Do not try this amp if you have speakers less than 89db sensitivity (or) a real small room. For my room (26ft L*18 ft B * 14 ft H) used with a 91db diy 2&1/2 way they are plenty loud.

Research

While you would want to troll every nook & corner of diyaudio (like i did) the following are must reads

http://www.firstwatt.com/pdf/prod_f5_man.pdf -- Firswatt watt manual. Read, understand & memorize :-)

An illustrated guide to building an F5 - diyAudio -- Illustrated Build Thread

F5 Bias Problem - diyAudio -- Biasing & Issues

How Hot Is My F5? - diyAudio -- Heat & Heatsink
 
Components

While there are multiple sources (ebay, diyaudio store).. The following is what i used

----Amp PCB
eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices

---PSU PCB & Parts

eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices

Remember is used a DUAL-MONO build. If you intend to have only one tranny then i would get the following board

CRC Power supply PCB for class A Power amplifiers ! | eBay

---Heatsinks

I procured them locally in Kolkata. 165mm (H) * 450mm (L) with 15 fins. The base is 10mm thick , the two outer fins are 50mm while the inner fins are 40mm in length. All fins are ribbed for better heat dissipation.

I have a link. Not sure whether sell retail (or) ship domestic

N.K.Electronics

---Resistor

I used 1/4 watt Dale CMF series (1%) available from Digikey
Panasonic 3 watts 5% for feedback & source resistors

---Mosfet

There is a raging debate going on for the pro/cons between IRF,FQA,Toshiba mosfets. Out of these three IRF is the cheapest and easily available. I used that. Note that if your are using only 1 pair of o/p devices (as per the original circuit) the mosfets need not be matched.

---JFET

Jims audio kit includes JFET's that are a step down from what people use. You have order them from Spencers (fetaudio.com)

---Capacitors

I used Chinese capacitors (company called Jicon) 8*10000uF 50V per rail with half decent specs
 
Cost

I have 3 things running simultaneously (DAC, Pass B1 & F5) so cant put a exact figure but i guess something in the range of 30K. If i had to do it again it will be around 25K.

Feedback

F5 offers a 15db gainusing 4 100ohm 3W resisotors. You can increase the gain by another 6db by using 4*200 ohm 3 W resistors

Component Placement & Serviceability

---Mount the source resistors (.47 ohm) elevated from the board. This allows easier attachment of multimeter leads during biasing
---Mount R3/R4 elevated from the board. You might have to add resistors in series to them if you cannot bias properly
---Solder the above resistors on the top side facing you. This will help in removal without removing the board from the heatsink
---Place the PSU & amp boards in such a way that you clear access to the trimpots with everything (expect top) buttoned up.
---While zero-ing the trimpot resistances you can actually measure them across R3/R4 (make them zero)

Gotchas/Safety Issues

---Drilling & tapping holes in heatsink is difficult (at least to me)
---Proactive measure temperatures. Use a multimeter with K type input & appropriate sensor. Measure the temperature across the drain leg of each mosfet. Do not let them rise above 70C.
----Do not accidentally short outputs, there is a very good chance that mosfets would blow & without a speaker protection circuit pass 24V to the speakers thereby blowing the drivers (though the built in current protection circuit will give you some protection)
 
Might be a good idea if using 500 or more VA trafo..the actual F5 uses a single 300VA though :-) & the build thread I listed uses a 600VA w/o soft start
 
Nice to know a class A project going on here...congrats on your build:clapping:
It would be nice if you post more pictures of your final build.
I am too in the middle of a project, its JLH 2003(Updated) class A, will be approax. 10 watts/ch, have designed the PCBs, bought all local components from Chandni Chowk, a salvaged transformer, currently looking for heatsinks. Looks like you are in Kolkata, me too :yahoo: , may be we can meet and share experiences, let me know if you are interested.
 
smyastat said:
Nice to know a class A project going on here...congrats on your build:clapping:
It would be nice if you post more pictures of your final build.
I am too in the middle of a project, its JLH 2003(Updated) class A, will be approax. 10 watts/ch, have designed the PCBs, bought all local components from Chandni Chowk, a salvaged transformer, currently looking for heatsinks. Looks like you are in Kolkata, me too :yahoo: , may be we can meet and share experiences, let me know if you are interested.
Click to expand...

Looks like Kolkata DIY family growing strong :clapping::clapping:

Krishnendu, tag me along if/whenever you two decide to meet.

Bhaskar
 
I had purchased black anodized heat sinks from a shop in chandni when I went there in October. He had many designs. Unfortunately had bought only 2 so have non efor my pass 5 build.
 
Grubyhalo..all heatsinks that I have seen have horizontal fins so my amp has to stand on its faceplate & it easily passes the 5 second hands on test :-)....about affecting the ambient, class a & room heater is most probably a joke ..my 42 inch plasma heats up the room more than the F5
 
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Purchase the Audiolab 6000A Integrated Amplifier at a special offer price.

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