*** The DIY Audio Thread ***

my diy preamp, which is then feeding the valve amp (baby huey).

I hear a significant improvement, and its isnt that subtle. The top end is definately more refined.
 
So does the transformer do a similar job to a capacitor-coupled buffer then? Just blocks and DC and provides a decent output impedance?
 
Am hoping to build some floorstanders soon, using CDT audio ES06+ components. They are made for cars which gives me 2 advantages:

They are 4 ohm so can extract more power from amps.

Can cut them down and use them in the car at a future date :)
 
Nice work adam, what are you using as a LPF?

EDIT: Just read above, resistor and cap, sounds doable, now I just need a couple of 1:1 transformers. :)
SoundsGood said:
I've got a couple to unused TA2020 chips spare if anyone needs one £cheap :)
Click to expand...
How many do you have? If you have 2 I'd definitely be interested...

After tinkering with my Lepai, I appear to have killed the TA2020... :( Overcurrent protection was bypassed with this amp and I simply had it running too loud. :eek:
 
p4radox said:
So does the transformer do a similar job to a capacitor-coupled buffer then? Just blocks and DC and provides a decent output impedance?
Click to expand...

sort of, it blocks the dc of the differential output, turns the balanced signal into single ended but and provided decent loading to the dac by using the series resistance. it doesnt lower output resistance too much, but these dacs a drive a fairly high load.
 
Soundsgood: One TA2020's you sent me is soldered and working. Sounds great in the little Lepai.

This little Lepai amp is rather good, it looks horrible, but even with no mods sounds decent. I've had to use the infamous clothes peg again, this time with royal mail elastic band!
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I managed to break the original volume pot while trying to get the front panel off, so I decided to replace it with a higher quality pot and make a new front from perspex. The only thing is, I don't have any knobs which fit the 'D' type pot, so until I order some more goodies I'll have to stick with the peg. :D

I've made a few changes, I've changed to cheap connectors at the back for better quality ones, the PSU cap has been changed for a better one, overcurrent bypass zener removed, and once I get a DPDT toggle switch I'm gonna attempt a tone control defeat switch and fault LED.

If anyone want to hear a tripath amp for less than £20 and doesn't want to solder then the Lepai is a great buy, I'd take it over the sonic impact T-amp anyday. :)
 
Apologies in advance for my noobish post....but my parents are wanting a very compact speaker system just to hook up to the laptop in order to just get a bit more volume to occasionally watch stuff on youtube, maybe internet radio...etc. Obviously not audiophiles.

I've got a pair of satellites from a creative gigaworks S750 5.1 system. These are very small and rated at 70W rms each....however since they are from a 5.1 system I assume the midwoofer thing is crossed over around 200-400 Hz or so?

Anyway, I simply want to extend the cutoff range down so that the satellites become full range speakers. I understand the midwoofer thingies might not perform very well below the cutoff range (very small speakers anyway) but I'm really just curious and want to mess around.

I've been doing some reading on crossovers this morning and opened up the speakers to examine the crossover circuit...I'm a bit confused as to which kind of crossover circuit this is...and what I need to change out in order to extend the midwoofers range to lower frequencies.

After looking at the crossover PCB, it looks like this is the circuit. I apologize for my lack of ms paint and schematic skills lol...the stars are the inductors...unknown inductance.....and I have no idea what the rectangle thing is...it says 10w6ΩJ on it.

The woofer is 8ohm and tweeter is 4 ohm. Thanks in advance, if nothing else I just want to understand this basic passive crossover.

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the long thing that you don't know what it is is probably a resistor

CAN you post a photo?

also if you bypass the 1st 200uF (are you sure it's not 200nF?) capacitor on the left, that should remove the HPF on the woofer.



In other news, I now have a tone control bypass switch on my Lepai, sounds much nicer when the tone controls are bypassed.

Pic:
11062009241k.jpg
 
Yes, just bypass the 200uF capacitor to remove the high pass filtering. The inductor in series is the low pass filter which limits how high the woofer plays, leave it in place.

The white rectangular thing is indeed a resistor, it lowers the level of the tweeter. There's a nice plastic film cap at the left of the board, 4uF, which isn't on the diagram. Don't know what that's doing :confused:
 
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Sorry I was doing all this before I had any coffee and somehow missed out on that plastic film cap. Will take another look at the circuit in a bit.


On another note I've just finished my 2nd millet starving student build, this time using a PCB. Sounds great and a lot quieter than my messy P2P build...however the balance seems a bit off...got to look into that one. Other than that it sounds fantastic and I've graduated from plastic ****** boxes lol.
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Looks good :)

Are the semiconductors bolted directly to that heatsink from inside? I ask because I doubt you'd get great thermal transfer through the case with that ribbing effect.

The skewed balance is likely to be the volume pot, they don't often match that well. Do you have the volume dial set very near the low end usually? The matching is usually worst at the lowest settings.
 
Thanks. The imbalance is all the way at full volume so I don't think it's the pot....could it be a grounding problem?

Here's a pic of the internals. I used arctic silver 5 epoxy that I had laying around to bond the mosfets to the top of the chassis (insulator in between). I also used some cheap thermal paste in between the heatsink and the chassis.

There are a lot of layers of thermal interfaces but the amp has been playing Metallica, Sonata Arctica, and various electronic music for over an hour now and I just checked the mosfets with a temp probe and they are 46-48C so the heatsink and chassis seem to be doing about 15C better than my old to-220 sinks as the mosfets on my old SSMH were about 58-65C

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That's nice, how the PCB slots into the case :)

So long as the MOSFET's don't overheat you'll be ok, they are by nature less prone to thermal runaway than BJT's, espacially lateral units.
 
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