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Posts by mrarroyo

  Nice review although I did not find the 627 grainy as stated.
RFI is an issue with a lot of electronics, personally when I have an iPhone in use close to the amp (couple of feet) I can hear noise.
IMO the LME49720HA is an outstanding sounding op-amp and in many applications the best. I have had great results with them in the HLLY SMK-II and the sound is more open and detailed while maintaining a punchy bass. BTW, I used heat sinks on the op-amps. I have also replaced the volume pot with a cheap attenuator from eBay, see pic below.  
  Your are! Glad you are enjoying the new toy.
I have had this amp for a bit over two months. As stated above it has too much current going to the valve so I replaced a resistor with a 20 ohm 5 watt one and the amp draws less current and runs a bit cooler. As a side benefit the amp run time has gone from about 3 hours to 4.5 hours. Next I tried op-amp rolling and replaced the NE5532 with: AD8620, AD797 (two to one board), and LM4562. Of those the AD8620 sounded the best but not necessarily better than the NE5532 just...
I would try a different manufacturer unless you are buying a rebuilt Singlepower by a know repair shop. I still have my Singlepower MPX3 SE Slam that has been made safe and I love its sound, you may want to look into Mapletree amps by Dr. Lloyd or if you want to spend the moola Red Wine Audio amps.
^ Hi there, long time since I post here. I concur with your statement, Grado cans sound IMO great and unfortunately with the proliferation of new cans by various vendors people do not seem to be enjoying them as much. A pity since the Grado sound is unique and quite engaging with far more styles of music than just rock.  Currently listening to jazz via a highly modified SR80, which sounds great but of course not in the same league as the RS1 and higher Grado cans.
Had the HE6 on loan and have had the HE500 for a while as well as two K1000. As much as I like the HE500 the K1000 is IMO a whole different beast and the one I prefer. Granted we all hear differently and our music, sac, amp, etc can steer us into different directions. Just try it and decide which is better for you.
Find an used 1970's receiver from Marantz/Pioneer/Technics/etc in the 20-35 wpc range. and use the 1/4" headphone out or the speaker outputs to drive your cans.
I have had this amp for about a couple of months. Out of the box the unit runs very hot, has a gritty volume pot, and the battery life is around 3-4 hours. In order to improve the battery life and reduce the operating temperature I replaced the resistor shown below with a 5W 20 ohm and the amp runs much cooler as well as having a battery life of around 5 hours.          
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