[kukkurovaca]

Haven't had much time with it yet, but it's currently driving T20RP MkIIIs better than anything else I own

Oooh. Which other amps have you used with the T20RP's?

 

[MyPants]

Glad you like them, MyPants. Let us know how it goes with the rest of the cans. The HE400i’s are challenging but I think they were working admirably well considering how low sensitivity they are. I am curious about how well your 600ohm cans sound.

I too am curious to see how it performs with the 600ohm DT880s. Tomorrow I have a bunch of clerical work to do at my desk, so I'll have a chance to demo it with the HE400i and the DT880. Tonight I gave it a little over an hour between the T20RP and the thinksound On2 which also arrived today, and the NHB paired wonderfully with both. I'll probably run the first set of batteries out tomorrow, so I'll have to wait till saturday or sunday to test all the IEMs. I don't wanna swap the batteries out until my ESD wrist strap comes in saturday evening.

Oooh. Which other amps have you used with the T20RP's?

My other solid state amps are a cMoy BB kit from JDS Labs and an o2 that I built, and I also have a Little Dot MkII OTL tube amp. The cMoy drives them fine volume-wise and does the highs/mids reasonable justice but gets a little loose in the bass. The o2 actually does a really good job, but simply isn't as musical or engaging as the NHB. The NHB also seems to deliver better overall bass response (tighter/deeper/slam-ier). The Little Dot has heaps of voltage and current on tap, but equal heaps of output impedance... This is fine and even somewhat preferable with the 600ohm Beyers, but makes the T20RP sound really incoherent and uncontrolled (relatively speaking of course).

 

[xrk971]

Just make sure you discharge your fingertips on the tin itself and you will be fine to change batteries. Just don’t touch the circuit board directly. Have fun.

 

[MyPants]

Can confirm the NHB does a beautiful job of driving TH-X00 Purplehearts. Kindof a ludicrous headphone to truly take "portable", but the easy chair sure is far from my desktop rig...

 

[xrk971]

Here is the latest custom amp for a HeadFier - based on the Pocket Class A amp core but with removable 9v battery compartments and built in DC-DC step up for regulated 18.0v rail and Cap Multiplier to clean up the wall power followed by 30,000uF of CRCRC filtering. Anyhow, it is running a hot 75mA bias current and uses 1600uF of output coupling capacitance. Drives most headphones with power. Even HE400i’s work. The transition from wall power to battery or vice versa is seamless. The sound is really clean with 18v rail power. The ability to pick it up off the desk and take it out to the pool, patio, park, etc is a real bonus.

 

[xrk971]

The long awaited desktop amp with built in cap multiplier and CRCRC and ability to run up to 125mA bias current is almost here. Layout by BabyDontHertzMe and JPS64 on DIYA.

Double plane traces with a thousand vias to connect both sides for high current. Central star grounding with separate ground planes for left-right and PSU.

A cap-roller’s delight with lots of space and holes for many different sizes and BIG caps.

It will be a very fun amp to have.

 

[DBaldock9]

Both of these are Single-Ended?

 

[xrk971]

Yes same topology as title amp.

 

[DBaldock9]

@xrk971 - Is there any possibility that you could offer an add-on circuit board to fit in the "other half" of the Altoids tin (leaving space for a 3.7V Li-Ion battery), containing the 5V USB to 3.7V charger, cap multiplier, and CRCRC - for us DIYers, who aren't afraid to cut the trace that's required, and solder the 3 or 4 wires to the Amp circuit board - so we can run the PCA from USB power, and not have to constantly swap 9V batteries?

 

[Slater]

@xrk971 - Is there any possibility that you could offer an add-on circuit board to fit in the "other half" of the Altoids tin (leaving space for a 3.7V Li-Ion battery), containing the 5V USB to 3.7V charger, cap multiplier, and CRCRC - for us DIYers, who aren't afraid to cut the trace that's required, and solder the 3 or 4 wires to the Amp circuit board - so we can run the PCA from USB power, and not have to constantly swap 9V batteries?

I second this.

 

[xrk971]

Let me think about it - I have other developments coming along that might make this not needed. But seems like a nice aftermarket upgrade board for the Gen 1 amp.

 

[xrk971]

New Desktop Class A (DCA) amp comes to life. Fired up the first time no issues. Built in cap multiplier and CRCRC. Running 22v rail and 150mA bias current.

Here is FFT for 1.0vpp into 270ohm load with the low THD optimization:

If you like it more tubey sounding with H2 higher than H3 by about 8x, this optimization looks good:

 

[gikigill]

Price for the Desktop Class A?

Can you please provide a figure of wattage @50ohms.

 

[xrk971]

Right now the DCA is just a PCB. If you want a custom build in a case, PM me or contact me on my Etsy shop and we can work it out. I just did a test to get max power for you. With a 51ohm load resistor in parallel with on board 270ohm load, we get 42ohms net. I boosted Vcc to 25v and connected the Cayin N3 as source playing a high res 1kHz FLAC file. I maxed out the volume on the N3 (100%) and still could not get the DCA to clip. Here is the test with the DMM showing 3.34vrms and O-scope trace showing unclipped behavior. 3.34vrms into 42ohms is 265mW. So I guess you are looking at some HiFiman ro Audeze planars at 50ohms? Assuming meager 84dB sensitivity, 265mW is about same as 256, which conveniently is 8 doublings of power from 1mW. So we know 8 doublings x 3dB = 24dB. So the 84dB cans can play 84dB+24dB=108dB SPL with this amp. That's pretty loud.

Here is O-scope screen shot:

So there you have it. This is running a hot 180mA bias - but heatsinks are doing fine.

I am listening to it with my HE-400i's and at max volume on the Cayin N3, I cannot open the volume on the amp to max without it being too loud to be comfortable. So I think this amp can drive inefficient planars just fine. Sounds very, very nice. Unbelievably dynamic with no sign of distortion or compression artifacts on bass peaks.

Just realized that I did the max power test with the volume pot not in max postion, so there is probably some more power left. Maybe 3dB more or at least 500mW or 111dB on the 84dB headphones.

Edit: quick re-test shows 4.78vrms and that is 544mW into 42ohms. I was close...

 

[gikigill]

How about a sensitivity of -73db@50hms.

I am thinking of commissioning a desktop full Class A amp for planars.