Firstwatt F2 Build Log

[hugz]

Quote:

Originally Posted by varro /img/forum/go_quote.gif Have you tried to put a cover to the transformer?

Not yet. The whole thing is still uncased because I became unemployed (now re-employed but awaiting my first paycheck) and I'm having serious difficulties sourcing someone who will sell my aluminium sheet cut to size here in Australia. Everyone just wants to sell me full sheets (for something like $280), which is doubly a pain when you consider that I dont want my case to all be of the same thickness (so to do it exactly how i'd like I'd need to buy TWO sheets).

So i'm either going to have to try hunt down some scrap metal that's approximately the right size and cut it myself, or change my plan from anodized aluminium to powdercoated steel and perspex.

</vent>

I dont think the transformer is the problem because moving it around has made no noticable difference.

I put my one remaining 0.0033uf film cap on the output of the transformer and that seemed to cut down on the noise a bit. Unfortunately there's two transformer outputs (1 per channel) and I only have one low-value cap left, so I couldn't do it for both outputs. So i'm back to suspecting that crappy power is my problem.

I do have a 1uf cap, but would that be way too high for power filtering? I'm really not sure how it all works, but if 1uf is ok for power noise filtering then I'll put it on and see what happens

Quote:

Originally Posted by splaz /img/forum/go_quote.gif Any pics ? Looks nice but out of my budget

Thankyou. No new photos since it's still uncased, so there's just the stuff thats earlier in this thread. I'll definitly be doing a big update with lots of photos when I get around to casing it.

here's a photo of it powering my sennies. http://img62.imageshack.us/img62/1603/ghettorigqg8.jpg

the photo doesn't really show much but I liked how silly it all looks

Quote:

Originally Posted by nightfire /img/forum/go_quote.gif I highly recommend Digikey's resistor kits (though I haven't tried their SMD ones). I just bought 3 @ $30 each, and they in total include ~1500 1% 1/4 watt, 5 of each value, all the way from 1k to 1M. At least that's one less thing to worry about when working on projects. And obviously especially good for experimenting. Their capacitor and transistor kits don't seem nearly as useful though.

i really wish i did that.

 

[cotdt]

i had a noise problem too, but then i decided to run it balanced and it fixed the problem. completely black background and it was nice. but i had to make another pair of amps for the other channel.

 

[hugz]

Quote:

Originally Posted by cotdt /img/forum/go_quote.gif i had a noise problem too, but then i decided to run it balanced and it fixed the problem. completely black background and it was nice. but i had to make another pair of amps for the other channel.

I dont think line noise is the problem, however I suppose it may be a possibility. I played around with the power supply a little more today and it seems to be getting quieter.. i think

I have a zhaolu here with me at the moment (balanced) so i suppose that if I have time I'll try make it into a mono balanced amp just to test what happens. i dont have any xlr cables for the zhaolu though ..

 

[cotdt]

Quote:

Originally Posted by hugz /img/forum/go_quote.gif I dont think line noise is the problem, however I suppose it may be a possibility. I played around with the power supply a little more today and it seems to be getting quieter.. i think I have a zhaolu here with me at the moment (balanced) so i suppose that if I have time I'll try make it into a mono balanced amp just to test what happens. i dont have any xlr cables for the zhaolu though ..

it's true that there could be any number of possibilities that could cause the noise, and you eliminated many of them already. i think it's worth trying. you can open up your zhaolu and direct solder the connections. this is the world of DIY after all =).

 

[hugz]

What would you do?

OK, so you have a nice amplifier that you've built yourself. It's powering your speakers (which incidentally, you built yourself) and your headphones.

And now you have the opportunity to mod it in any way your heart desires. After all, it's your handiwork so there's nothing to lose.

SO, what would all of you guys do to the firstwatt to make it even better if it was your amp? All I can think of so far is:
- upgrade the caps
- beef up all the internal wiring
- add a switch to allow it to change the damping "on the fly" (theoretically - changing the bass - a bass boost switch)
- MAYBE use XLRs or something else for all inputs and outputs (rather than RCAs and banana) even though it's not balanced. I'm not sure if the hypothetical sound advantage is worth the inconvenience

I could possibly silver wire it all. Probably not much of a sound difference, but it could be fun.

Any suggestions for cool mods to leet up my amp?

Quote:

Originally Posted by cotdt /img/forum/go_quote.gif it's true that there could be any number of possibilities that could cause the noise, and you eliminated many of them already. i think it's worth trying. you can open up your zhaolu and direct solder the connections. this is the world of DIY after all =).

Indeed, and thanks for the suggestion. The zhaolu is a loaner so i probably shouldn't hack it up

but I can probably get my hands on a xlr

 

[Jon L]

What kind of change in sound do you want to achieve through mods? You mentioned it sounds "soft and warm," so do you want to add a bit of edge definition and resolution?

Rewiring with silver will push the sound in that general direction; however, I highly doubt the end result will be what exactly you wanted in terms of tonality and density.

I would favor rewiring with good awg continuous cast copper wiring for power and speaker wiring and smaller awg of same stuff for signal wiring.

I don't know how much feedback the design has, but can you make it adjustable?

A dial to change the bias of the output devices would be useful, too. Pure class A solid state is great, but sometimes depending on speakers/headphones, a little push towards class AB 'can' result in apparent decrease in the (overly) soft and round warmth.

 

[cotdt]

Pics?

 

[cotdt]

You can change all the power supply capacitors to Blackgates. It does make a difference. Are you using Panasonics? Those are terrible.

 

[hugz]

Quote:

Originally Posted by cotdt /img/forum/go_quote.gif You can change all the power supply capacitors to Blackgates. It does make a difference. Are you using Panasonics? Those are terrible.

nichicon caps, panasonic resistors.

no way in hell am i black gating the power supply. Although its true that I'm no electrical engineer, i seriously doubt that the brand of caps in the psu will make that much difference... but maybe i'm missings something.

the psu has 120,000 uF of capacitance in it. If i'm going to spend more money on caps for it then i'll probably just double the capacitance (if that can be done and if its worth doing). I imagine 120,000 uf of black gates would break the bank.

Thanks for the suggestion nonetheless

Quote:

Originally Posted by cotdt /img/forum/go_quote.gif Pics?

there are pics all over the first page

Quote:

Originally Posted by Jon L /img/forum/go_quote.gif What kind of change in sound do you want to achieve through mods? You mentioned it sounds "soft and warm," so do you want to add a bit of edge definition and resolution? Rewiring with silver will push the sound in that general direction; however, I highly doubt the end result will be what exactly you wanted in terms of tonality and density. I would favor rewiring with good awg continuous cast copper wiring for power and speaker wiring and smaller awg of same stuff for signal wiring. I don't know how much feedback the design has, but can you make it adjustable? A dial to change the bias of the output devices would be useful, too. Pure class A solid state is great, but sometimes depending on speakers/headphones, a little push towards class AB 'can' result in apparent decrease in the (overly) soft and round warmth.

Yes it is warm and soft etc, and I do like this.. however I would like to push a bit more high end out possibly. My speakers lack high end sparkle as does my dac (thinking of replacing it with something brighter), so when combined with a SETish amp it can be a tad too warm. Silver may be good, but i'm not entirely sure what i shoudl expect it to do.. if anything.

the design has no feedback

a gain dial may be cool. you say that i may want to try pushing it into AB... that would involve increasing the power, right? I could try that but I may become worried about the heat. I have enough spare mosfets to maybe try it anyway .....

Turning down the gain/power could be good too for headphone use. at the moment i'm running resistors in parallel with the headphones to reduce the output, but reducing the gain is probably a cleaner way of doing this. is there any harm to be done from reducing the power further? i kinda get the feeling that pushing it "further" into class A cant hurt (as opposed to pushing it into AB to get more power), but i'm not sure

thank you both for the input

 

[Jon L]

Quote:

Originally Posted by hugz /img/forum/go_quote.gif Turning down the gain/power could be good too for headphone use. at the moment i'm running resistors in parallel with the headphones to reduce the output, but reducing the gain is probably a cleaner way of doing this. is there any harm to be done from reducing the power further? i kinda get the feeling that pushing it "further" into class A cant hurt (as opposed to pushing it into AB to get more power), but i'm not sure thank you both for the input

It's always much easier on components to go from A to AB; you shouldn't have to add any extra stuff to bias things a little less hot. However, if you push it further into class A, you might have to add more heatsinking, and there's chance some of your parts/components will start to go into their non-linear, higher-distortion part of operating curves.

IME, Fets can sound a bit warm to begin with, and class A can push this too much in the same direction. Ditto for no negative feedback.

Power will increase in AB, which can have surprisingly large effect on speakers. Unless speakers are truly in 105+ dB sensitive range, a few more watts can go a long way in terms of frequency extension and dynamics, especially at "realistic" volume levels.

 

[cotdt]

you can add a supertweeter with a 0.47uF capacitor for more high end sparkle.

agreed about the Class AB thing. more power really helps.

 

[Garbz]

But that would completely destroy the full range speaker concept if you add another driver

Super tweeters are a waste of time IMHO unless your speakers actively roll off before 20k.

 

[splaz]

Quote:

Originally Posted by cotdt /img/forum/go_quote.gif You can change all the power supply capacitors to Blackgates. It does make a difference. Are you using Panasonics? Those are terrible.

No they aren't Panasonic capacitors as they don't have the curved T vents.

What's wrong with them anyway ?

I know I've heard that they're bad as decoupling caps but FM/FC have good specs for power supply use. A fairly good combination of low esr, high ripple and long life.

Although I guess if blackgates in the power supply gets you that placebo effect and you're happy to pay a premium for it, whatever floats your boat.

 

[cotdt]

Quote:

Originally Posted by splaz /img/forum/go_quote.gif No they aren't Panasonic capacitors as they don't have the curved T vents. What's wrong with them anyway ? I know I've heard that they're bad as decoupling caps but FM/FC have good specs for power supply use. A fairly good combination of low esr, high ripple and long life. Although I guess if blackgates in the power supply gets you that placebo effect and you're happy to pay a premium for it, whatever floats your boat.

you can stop pretending to be an objectivist by calling me a snake oil guy. low esr is not the whole story for power supply capacitors, and i don't even think this is an important factor. there are more complex measurements that can show the difference. i have switched out various capacitors on power supplies and heard a difference, while you have obviously not deemed it worthy to even try based on your pseudoscience (there can't possibly be a difference if you can't explain it). i can offer you to hear for yourself, or arrange a blind test, but based on my experience people like you tend to refuse this simple offer. i have my own theories as to why choice of power supply capacitors matter, but that is for a chemistry forum not here (i have a university degree in chemistry).

 

[splaz]

I apologise if that came off as a personal attack in any way, I feel I worded it slightly wrong.

Sorry hugz for bringing this up in your topic and I ask that no one else continue this discussion, I'll be taking it over to pm.