F5m kit

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#1,422
I would buy the following, 300VA, +/-18Vac

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#1,424
I managed to buy F5m kit. After 7 hours later because of the time difference between US and EU. If it would be possible next time to consider also that EU people who usually sleep at nights can have same change to get the kits. 🤣

I have some bunch of questions and hope that these also will help others.

Thermistor- B57236S0479M000 Epcos - If I have 500VA 230AC and 2x18V AC then do I need to get bigger thermistor with amps and how 5 Ohm or 10 Ohm thermistor affects this if I am planning to use 40 000uF per rail or higher and to bias F5m with 1.4 - 1.7 Amps? Planning also to use this PSU with other amplifiers to try them out with higher bias and different mosfets. Amplifier case will be 4U or 5U with 500mm.

Resistors - I have heard with my own ears how they affect sound quality even if they are used in collector pin location.
R6 and R7 are wirewound resistors 0,47 Ohm. Can this value also be 0.4 or lower/higher? How that affects this amp and sound if biasing amps are the same? Is it OK to use multiple metal film resistors or even multiple 1W MELF resistors in this position?

I am still rookie. 🤣

This will be my first amp to build.

🙄
 
#1,427
The best place to start is with Nelson’s document on the F5m. Read it, then go back and read it again. It offers recommendations and answers many questions.

The F5m is a relatively simple amp to build. If you follow the recommendations.
It is not intended to be a massively powerful amp. A 300VA transformer is sufficient, as is a basic 4U chassis. Even a 3U chassis is Ok. No need to spend too much on this one, it is also supposed to be less expensive.
 
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#1,428
Jacruzer787 said:
Based on this, why not build it as is and spend some time listening, then play with modifications. I am also a rookie and plan to build it as per the instructions. It is DIY and there is nothing preventing you from trying…. YMMV

Best,
Jose
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Very well said Jose. That would be my exact advice as well.

Best,
Anand.
 
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#1,433
Pierrick59 said:
sorry a line have been wrote in french you can delete it
@Peppe what are you listening by FW build
(sorry it's my first amp build )
what it brings to have 400 va?
for the case i have seen modushop but there is not more affordable?
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There are some interesting options on Alibaba but the shipping (to the US) is steep and you'd need to drill and tap the heatsinks yourself. This isn't a big deal but something to keep in mind if you don't already have the necessary tools. Drill, tap, tap handle, cutting fluid.
Modushop chassis, on the other hand, are pre-drilled and tapped to fit these boards (UMS) and are a good value with a number if options available.
300va vs 400va? I use the 400va because the cost differential is minor and I like the flexibility of having more current available for other projects. Mr. Pass ships his FW products with a 300va xfmr and I would go that route for a permanent build.
 
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#1,434
@Jacruzer787 alright man, my wife is going out of town for a week so I'll have extra time on my hands for some extending listening/testing. *Fair warning, my subjective listening report will be limited to a pair of MA 10p Pensils for now. My ability to hear and articulate differences? I'll do my best...
A second pair of channels are only lacking soldering in the fets and leads, so I'll also try to get to drilling/tapping another pair of HS to allow back-to-back comparison between ~1A and 1.5A bias settings. A basic CRC PS, 18V/400va > 44,000uF- 0R17- 20,400uF will be used.

Cheers
 
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#1,435
seventenths said:
@Jacruzer787 alright man, my wife is going out of town for a week so I'll have extra time on my hands for some extending listening/testing. *Fair warning, my subjective listening report will be limited to a pair of MA 10p Pensils for now. My ability to hear and articulate differences? I'll do my best
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Oh snap! Mrs. Seventenths is leaving you for a whole week!!! :rofl: Looking forward to your impressions, and who cares what you can or cannot articulate. This is not sterophile mag, just sharing among friends. Maybe that will convince me to build some pensils!

As long as its not WOW! Just wow!:headshot:
 
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