The Objective2 (O2) Headphone Amp DIY Project - Page 215 - diyAudio
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Old 26th February 2012, 08:33 PM   #2141
agdr is offline agdr  United States
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Quote:
Originally Posted by unsopa View Post
Thanks, agdr,
but what I meant was to omit the O2 power management also and just to build the main amplification first and to get some first impressions. As far as I know the DCT 200 power-supply ist truely transformer-isolated and short-crcuit-protected. Under these circumstances - how big is the risk to damage the headphones by temporarily using just the 2 x 9V outputs on the rails of the amp-section?
Well, I would consider that too risky if I were doing it, unless the headphones involved were $20 throw-away test phones. If I were not using the power management circuit then I would instead use a headphone protector circuit on the output, like an e12

The ε12 Muting / Protect Circuit

or the output relay modification I posted a while back

O2 amp CRC, diode, cap, and heatsink mods

But... that is just me. Other folks here may have some feedback for you. I just consider it too risky for any headphone amp not to have output protection of some sort.
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Old 26th February 2012, 08:57 PM   #2142
Zigis is offline Zigis  Latvia
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Quote:
Originally Posted by unsopa View Post
Thanks, agdr,
but what I meant was to omit the O2 power management also and just to build the main amplification first and to get some first impressions. As far as I know the DCT 200 power-supply ist truely transformer-isolated and short-crcuit-protected. Under these circumstances - how big is the risk to damage the headphones by temporarily using just the 2 x 9V outputs on the rails of the amp-section?
If you build just amp part, without power management, this is very risky.
If you accidentally disconnect one PS, you got full 9V on phones and burn it in few seconds.

If you want quick amp and building practice, you can build simple CMoy (I know, I know)

If you plan to use only from wall power, get small 12V-0-12v or 15V-015V transformer and build standard regulated PS and O2 amp part on protoboard
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Old 27th February 2012, 12:04 AM   #2143
unsopa is offline unsopa  Germany
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Quote:
Originally Posted by Zigis
If you build just amp part, without power management, this is very risky.
If you accidentally disconnect one PS, you got full 9V on phones and burn it in few seconds.
Uh, thank you for the warning! Then I understand the meaning in the O2 details:"The circuit prevents potentially damaging headphones with DC". - This risk is the price for DC-coupling of the headphone, that's my uneducated guess.

The CMoy is not an alternative as it has not near-zero output impedance afaik, which makes the O2 so attractive to me. Thanks for your links to other protection circuits and to show me these options, agdr, it's just with a little more effort I can build the O2 power management circuit. Hm.
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Old 28th February 2012, 03:54 PM   #2144
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Phew. Finally got to the end (started reading back at post one). It's been an interesting read.

I have to say, you guys; adgr, sofaspud, qusp, sgrossklass, nezbleu et al deserve a lot of credit for helping so many people with their builds. I'm sure RS really appreciates you all carrying the ball here while he's obviously very busy. You guys rock.

To anyone in general, what have you folks found to be the optimal gain values with Grado SR80s and AKG Q701s with a 1V source? I don't ask in regards to clipping, but where the best balance of pot travel lies with the 3B taper.

Cheers, everyone.
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Old 28th February 2012, 07:45 PM   #2145
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Gain for Grado SR80i from a 1V source would be about 1.25x and the gain for the AKG Q701 from a 1V source would be about 3.15x. If you're a quiet listener like me, then the common 2.5x low gain setting would be enough for the AKG's with some room to spare on the volume pot.
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Old 28th February 2012, 09:55 PM   #2146
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Hey, you're one of the people I forgot to mention in my post above. Here's a belated "you rock". Sorry about that - my memory just ain't what it used to be.

I had been thinking 1.5x and 3.0x, so I wasn't far off for once. I am a quiet listener, but I wondered what people were finding when they tried some really quiet/dynamic recordings with the AKGs. Thanks for chiming in, sir.
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Old 29th February 2012, 02:56 AM   #2147
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Quote:
Originally Posted by Cpl Clegg View Post
Hey, you're one of the people I forgot to mention in my post above. Here's a belated "you rock". Sorry about that - my memory just ain't what it used to be.

I had been thinking 1.5x and 3.0x, so I wasn't far off for once. I am a quiet listener, but I wondered what people were finding when they tried some really quiet/dynamic recordings with the AKGs. Thanks for chiming in, sir.

I use 1x and 3x, but I'm using the 15A taper. The 1x is plenty imo for efficient headphones even with a 1V source.
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Old 29th February 2012, 02:56 PM   #2148
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@shadow419,

Thanks for the input. Which headphones are you using?
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Old 1st March 2012, 03:04 AM   #2149
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I use Senn HD 25-1 II, and Brainwaivz HM3 for the most part. Have a pair of Senn 558, but don't use those much at all. Used a friend's k701's for a few days with the amp and 3x was plenty of volume for me. The Brainwavz HM3 I can use with 3x gain but the 15A taper has a lot to do with that.
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Old 1st March 2012, 08:05 AM   #2150
Grief is offline Grief  United States
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Hi! I am going to order a set of Beyer DT 990 Premium 250 Ohm headphones very soon and I have been researching all day the best headphone amp for my budget. Around $100-$150, there aren't many good options besides the E9 and the O2 seems to be a much better one.

The O2 seems to be perfect for my situation, and I have decided to go with that one, but I have a few questions first.

How does the O2 operate with my choice of headphones? I have a feeling they will work perfect since the O2 can drive much higher impedance phones and they seem to work great across a wide range of headphone types.
Just looking for some personal experience here.

Secondly I have some questions about the best/cheapest place to get the parts to put this together.
I decided to just order the PCB pre-assembled from JDS labs since I have limited time, experience, and funds (would cost me about $40 just for the soldering kit).
I feel like I could get some better prices on the batteries and power supply since they come to about $30 for the package.
I also don't like the way their enclosure front panel looks. I would definitely prefer something more clean, something like what Fiola has done here would be perfect, the only thing I would like more is black on black with no lettering.
I saw the enclosures at boxenclosures.com but didn't know if that is the best place to order.

Basically what I am looking for is the best place to order power supply, batteries, enclosure, and front plate. I have a feeling Mouser has all of these, but there site is pretty deep and I have a feeling someone more experienced may be able to guide me.

Thanks!

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