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Old 26th November 2017, 04:37 PM   #1381
xrk971 is online now xrk971  United States
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The solder paste is solder particles in a carrier fluid of flux. It flows nicely and self-removes solder bridges via surface tension from each pad. Assuming you don’t apply too much paste I have never had a problem with bridging. Even if you start with bridged paste, it clean up after itself. Quite amazing and 100% success rate so far with many boards (40+).
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Old 28th November 2017, 02:36 AM   #1382
stellarelephant is offline stellarelephant  United States
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Good to know. I enjoy making each joint by hand but if I have another failure I'll be firing up the hotplate...

BTW I couldn't resist nabbing a Cyber Monday deal, so I just bought my first set of planar headphones, the Mayflower 1, which is a modified version of the Fostex T50RP MkIII. They are notoriously hard to drive, but Funch said his Pocket Class A build made his fully custom T50RP-based cans sound the best he'd ever heard them... Will report back!
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Old 28th November 2017, 03:31 AM   #1383
xrk971 is online now xrk971  United States
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Hi StellarE,
Quote:
I enjoy making each joint by hand


I hope those planar cans are not too low impedance. What are they rated at and what is sensitivity?

I have a customer from HeadFi who bought the NHB amp for the HD6xx and it works great for that. She just got a planar HE4XX from Massdrop (93dB and 30ohms) and reports that it is not a good match (and I predicted thus - distortion would be quite high).

However, I ran some sims and it seems if you use the OKcells 9v rechargeable LiPo’s, they will work much better due to the higher voltage (fixed at 9v with internal DC step up). The THD with EBL’s would be 0.12% for 99dB and with the OKCells, only 0.07% THD. I want to test this out. Does anyone have HiFiMan HE400’s?
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Old 4th December 2017, 08:44 PM   #1384
stellarelephant is offline stellarelephant  United States
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The T50RP are rated at 50 Ohms. Sensitivity is only 92dB...maybe this is not looking so good for me. I almost got HD600 but wanted more bass. I have been talking with a guy on Head-Fi who has tried everything and now powers his T50RP with a 200wpc speaker amp...seems ludicrous to me but he swears it's the best he's heard them sound.

I am still using the OKCells. Eventually I will switch to the RaptorLightning LiPo setup, which would give me the option to boost voltage even higher, up to the limits of excess heat. I had no idea that driver sensitivity and THD were inversely related. I hope I can get an acceptable result.
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Old 4th December 2017, 08:50 PM   #1385
xrk971 is online now xrk971  United States
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It should be ok with 18v battery voltage and not played too loudly.

Planars will work well with a beefy SE Class A with 1.2amp bias current. Like Sikicon Harmony or MoFo, etc. need to drive with the Aksa Lender pre to get sufficient voltage.

They are reputed to sound awesome once given enough power though.
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Old 7th December 2017, 05:29 AM   #1386
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Quote:
Originally Posted by stellarelephant View Post
Finished my first RaptorLightning cap multiplier today. Truly easy peasy as Juma's name for the circuit suggests.

The Raptor USB load sharing board, however, has proven to beyond the limits of my soldering skills and equipment. The micro USB jack is the only hard part. Those five pins are absolutely tiny and hardly protrude from the main jack body at all. I tacked the steel housing down first and then tried to quickly drag a hot drop of solder across the pins...and ended up with a huge bridge across ALL the pins AND the nearest part of the housing lol. I then cranked up the heat and sucked up most of the solder with a solder braid, but I lifted a pad in the process. I can do most SMT but apparently not all. Honestly, those pins are so tiny, I don't think I'd ever be able to visually tell if I got every pin soldered or not. Argh. There must be an easier way to get the two power leads out of a micro USB...?

Here's a pic of my one success today.
Flux. And just the right amount of solder. If you can bridge the heat to all the pins you're fine. Get just the right amount of solder in there with -tons- of flux and it will find the correct home. Bridging comes from either too much solder or not enough flux to carry the heat to the pads and remove the thin layer of surface oils/oxidation that cause it to not stick and flow.

Edit: I'd love to post a magnified video of what I'm talking about. I use water soluble flux which has about the same viscosity as water and basically "boil" the connections in a small pool when I solder them, in no way stingy or careful about application unless I solder things that shouldn't get too wet with flux (potentiometers, etc.). It is the best way I've found to get joints like my earlier pictures of the PCA board. Cleanup has to be absolutely thorough, especially with the water soluble flux. However, thorough isopropyl washings with a brush, followed by a good surfactant cleaner, water, and compressed air work great.

Last edited by raptorlightning; 7th December 2017 at 05:46 AM.
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Old 9th December 2017, 02:54 AM   #1387
stellarelephant is offline stellarelephant  United States
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Raptor, your detailed description is very helpful and reflects perfectly the flux "magic" I observed in several videos. I'll "boil" the next one, lol.

In other news...yes my Pocket Class A drives my new Mayflower Fostex planars. In fact, I can keep the volume pot around noon unless I really want to rock out hard. Man, these things do realistic instrumental textures like I've never experienced from a headphone. Really awesome detail. I have never heard these cans powered by a beastly multi-watt desktop rig, so I have no point of reference to say if THD could be lower. What I can say is that they sound great with this amp biased at 64mA.
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Old Today, 01:59 PM   #1388
xrk971 is online now xrk971  United States
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StellarE:
Nice to know it can drive the Fostex planars. I know it struggles with 30ohm 85dB HE400's. I see that you are using MELF resistors. Where did you get those as I was trying order for my Aksa Lender preamp and all the US distributors (Mouser, Digikey, Newark) are wiped out.
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