I also built an O2 and it's a wonderful headphone amp. I did use it as a preamp when a friend brought a tube poweramp to my house and we needed a stand alone pre. It worked well in that role too.
I don't think putting a pot in between the source and power amp is optimal due to impedance matching issues. Also check out the B1 or DCB1 buffer if you can do without extra gain.
I don't think putting a pot in between the source and power amp is optimal due to impedance matching issues. Also check out the B1 or DCB1 buffer if you can do without extra gain.
Different how? And compared to what?
It's certainly going to sound different from a passive pre. It's going to sound different from an iPod or something similar as well.
The O2 is a fantastic little device - it has a near-zero output impedance, and the ability to drive damn near anything. If you are hearing something, it's probably a mis-match between the other thing and the F5... in my experience, using the O2 to drive many different amps (Gainclone, Millett DCPP, F4, F5, F6, Aleph J, BA-3, ST-70 and more) the O2 is essentially perfect - it has no effect on the signal. And the amps that need a low source impedance thrive with it.
It's certainly going to sound different from a passive pre. It's going to sound different from an iPod or something similar as well.
The O2 is a fantastic little device - it has a near-zero output impedance, and the ability to drive damn near anything. If you are hearing something, it's probably a mis-match between the other thing and the F5... in my experience, using the O2 to drive many different amps (Gainclone, Millett DCPP, F4, F5, F6, Aleph J, BA-3, ST-70 and more) the O2 is essentially perfect - it has no effect on the signal. And the amps that need a low source impedance thrive with it.
Can you describe the differences you hear? It will of course be subjective, but I'm willing to check for similarities in my setup. Also, What is your main source?
The signal comes from PC via USB, odac -> o2 -> F5.
I've had the F5 connected to the odac directly previously. I then had to adjust the volume via OS and had quite a bit of noise from my computer's USB power (ever noticed buzzing sound when moving the mouse? awful!). With the O2 this noise was reduced quite a bit.
I had a adum4160 between usb and odac before, which eliminated that noise, too, but I somehow managed to fry it. Waiting on a new one currently.
It appears that the highs are not that dominant anymore with the O2.
I've had the F5 connected to the odac directly previously. I then had to adjust the volume via OS and had quite a bit of noise from my computer's USB power (ever noticed buzzing sound when moving the mouse? awful!). With the O2 this noise was reduced quite a bit.
I had a adum4160 between usb and odac before, which eliminated that noise, too, but I somehow managed to fry it. Waiting on a new one currently.
It appears that the highs are not that dominant anymore with the O2.
Do you have a powered USB hub? If so, use it, what you describe seems to be a USB power issue - some computers are really nasty. The "dominant highs" may just be HF noise from the USB.
The Odac is USB powered, if you have a problem there, it's going to be continued down the line.
The best description I've seen is in the FAQ of this product -- Schiit Audio, Headphone amps and DACs made in USA.
The Odac is USB powered, if you have a problem there, it's going to be continued down the line.
The best description I've seen is in the FAQ of this product -- Schiit Audio, Headphone amps and DACs made in USA.
Yup, that's why I've used the adum4160 before. It's a simple IC to isolate USB peripheral equipment (has separate Vbus/Gnd/D+/D- for in and out). It really works wonders. Too bad I fried it after a couple of weeks.
I don't quite understand why the odac doesn't use its own power supply. Having the usb port power the analog side of the circuit seems like a huge design mistake.
I don't quite understand why the odac doesn't use its own power supply. Having the usb port power the analog side of the circuit seems like a huge design mistake.
I also use a PC as a source but with JRiver Media Studio which allows for completely bypassing the noisy Windows drivers via SP/DIF over a 16' BNC cable. There are differences between the 32 and 64 bit versions of programs, but a little experimentation will get you there if your DAC can accept ASIO or WASAPI data.
If your motherboard has SP/DIF pins an adapter can easily be made to tap in for an even cleaner signal. Here are some links to what worked for me:
MB Info
DIY Bracket
I suspect that it was much easier to have it USB powered than adapt something to power it from the O2. Physical space considerations likely became a huge issue.
USB can be quiet... but too often isn't. I really want to get a Wyrd - it's complete and utter overkill to use a 723 for USB power, but gawd in heaven, I like that idea!
After you mentioned the LM723 I've been looking through its datasheet. Since it's not much more hassle to build figure 20 of the datasheet (http://www.ti.com/lit/ds/symlink/lm723.pdf) instead of a 7805 or equivalent, I might give that a try for the next power supply (for the adum, peripheral side).
What's its dropout voltage? It doesn't say in the datasheet.
The Wyrd faq mentions that it doesn't use galvanic isolation since it wants to keep its usb 2.0 hi-speed capabilities (the isolation chip which I've mentioned can only do full-speed). Doesn't that kind of defeat its purpose? Well, since it helps, it probably doesn't..
What's its dropout voltage? It doesn't say in the datasheet.
The Wyrd faq mentions that it doesn't use galvanic isolation since it wants to keep its usb 2.0 hi-speed capabilities (the isolation chip which I've mentioned can only do full-speed). Doesn't that kind of defeat its purpose? Well, since it helps, it probably doesn't..
Hi all,
My amp kept blowing up the fuse.
I've finally found it is one of the bridge rectifier that went bad.
I'm looking to purchase a new one but there are so many options!
SOLID STATE, VISHAY, FAIRCHILD...
Can someone recommend brand? should I go for higher specs like 40A, 800V?
Should I replace both rectifiers while at it?
I didn't listen for so long, got to fix this ASAP...
Thank all
IK
My amp kept blowing up the fuse.
I've finally found it is one of the bridge rectifier that went bad.
I'm looking to purchase a new one but there are so many options!
SOLID STATE, VISHAY, FAIRCHILD...
Can someone recommend brand? should I go for higher specs like 40A, 800V?
Should I replace both rectifiers while at it?
I didn't listen for so long, got to fix this ASAP...
Thank all
IK
Clean the heat sink carefully with alcohol, deburr the mounting hole, and use a thin layer of silicon grease
on the rectifier block. Torque the mounting screw properly.
one CL60 adds ~10r when cold to the primary circuit.
At switch on with 0r2 of cabling resistance and 0r5 of transformer primary resistance, the peak start up current could approach 220*sqrt(2)/{0r2+0r5+10r} ~ 29Apk
That repeated a few times will fatigue a mains fuse. It might not blow on first start up, but it's life in terms of re-starts will be limited.
I suggest that for 220/240Vac mains you use at least two 10r Power Thermistors.
The smallest resistor values I use on the UK's 240Vac is 40r. For smaller transformers I have used up to 140r.
At switch on with 0r2 of cabling resistance and 0r5 of transformer primary resistance, the peak start up current could approach 220*sqrt(2)/{0r2+0r5+10r} ~ 29Apk
That repeated a few times will fatigue a mains fuse. It might not blow on first start up, but it's life in terms of re-starts will be limited.
I suggest that for 220/240Vac mains you use at least two 10r Power Thermistors.
The smallest resistor values I use on the UK's 240Vac is 40r. For smaller transformers I have used up to 140r.