[n_maher]

I'm tweaking one of my MINTs to be used specifically with low imp. phones like my grados and 4Ps. What I'm thinking about doing is just using 220ohm for R4 resulting in a gain of 2. Does anyone see a problem doing this? Or have a better suggestion for resistor values to get the net gain of 2?
Opamp is a OPA2227, which according to TI's docs is unity gain stable.

I've experimented with Tangent's calculators so I know there are literally hundreds of combos that will work, so I'd really be looking to hear from someone who actually tried the config that they suggest to make sure that it works. I can't find anything in any of the pages to suggest that having these two resistors as the same value is a bad thing.


Thanks in advance,

Nate

 

[Syzygies]

You'll want to add 75 ohms resistance to make the 4p into 4s, at least one some music. I use an external cable, but I'll probably do this internally in the future. Then, a gain of 4 or 5 makes more sense, depending on your source.

 

[n_maher]

I've got two PtoS adapters. And a gain of 2 should work fine even with 100ohm cans/phones. If memory serves me correctly Tangent runs most of his amps with a gain around 2.

The gain is currently 5 and I have issues with the Panny pot and crappy channel matching at the volume that I like listen at, so I'm looking to go much lower.

N

 

[Megaptera]

I'm running my PPA with no voltage gain at all, and I find the volume knob turned to about 1/2 to 2/3 position with my MS-2s. A gain of 2 will definitely give your Grados enough volume, and almost certainly your 4Ps, too (just guessing on that one; I've never played with a pair).

If the MINT is already built according to Tangent's suggestions, the other resistors are more or less balanced to let you swap out R4 to adjust the gain. It's probably easiest and safest to simply adjust that rather than swap in a whole new set of resistors.