Fully decked out with upgraded tubes and Jupiter Capacitors, FORGE represents something we’ve always wanted to do at Headphones.com which is to make a tube amplifier that fits our favourite headphones!
After months of testing to get the perfect configurations and back and forths with Justin Weber, founder of Ampsandsound, FORGE was born and with it we made the decision that there should be two versions.
The first variation of FORGE comes with a Low Z Headphone output of 32 ohms and High Z headphone output of 300 ohms making it the perfect match with one of our favorite headphones, the Sennheiser HD 800S, or any high impedance headphones in general.
The second variation of FORGE comes with a Low Z Headphone Output of 8 ohms and a High Z Headphone Output of 100 Ohms. We recognize that not everyone has ultra-high impedance headphones, and for anyone looking for a bit more versatility from their amplifier, this is the one to go for. This version is a perfect match for the Focal lineup of dynamic driver headphones - with the Utopia sounding truly amazing out of the 8 ohm out - along with a wide range of planar magnetic headphones with different impedances and sensitivity. Speaking from experience, we absolutely love planar magnetic headphones like the Rosson Audio Design RAD-0 off this amplifier as well.
Specifications
With JJ KT88s:
Input Sensitivity 1.6v P-P
Max Power Hi Z (300ohm) 4Watts
Max Power LoZ (32ohms) 4.5watts
Noise HiZ 680uv RMS
Noise LoZ 460uv RMS
Hmm, I see the Pendant v2 has 8 ohm and 100 ohm headphone impedance out connections. That would be closer to the other version, but then the Pendant uses different tubes as well.
In theory, the 32/300 model should pair best with ZMF. However, see series of posts before and after the link below. For ZMFs and A&S made amps, I believe the sweet spot is 32 and 100. 300 didn’t work well for me; it has for others.
Unfortunately, I suspect the answer is “it depends”, as it will depend on a combination of your personal preferences and also the tubes you’re using.
@bpcarb and I were discussing this a few weeks ago when I was comparing 100 and 300 on my Nautilus (different amp, but closer family connection to the Forge than the Pendant). At the time, I was enthralled with how exciting the 300 ohm output sounded on rock music, using my Verite. But I neglected to post later that after the excitement wore off, it was just too much, and I reverted to using the 100 ohm output.
I’m using 5AR4 rectifier tubes, which have an aggressive quality to them, and in combination with the 300 ohm output, it was like watching a TV set to ‘vivid’. It’s really impressive because you are bombarded with so much detail, and bass lines are locked in. But just like tuning the settings on my TV to make it more pleasing for extended viewing, I came to realize that I couldn’t listen to the 300 ohm output for hours on end, whereas I can do that using the 100, which gives me a more liquid presentation that seems softer in direct comparison to the 300 when I switch over, but eventually sounds more natural to me.
The same effect can be heard when using the Aeolus, but maybe because it’s less resolving than the Verite, I can have more extended 300 ohm listening sessions with the Aeolus when I’m seeking some extra excitement while I’m listening to Tool.
So for my personal preferences, with my tubes, I would choose 100 ohms for ZMF, but YMMV.
First, congrats to Andrew, Taron and Justin on this!
Hope it does well for all of you!
Second, it’d be useful to have some specs. I can glean the tube types from the pictures of the top-plate, and the impedance options are posted, but what about all the other salient info?
I expect the 100 ohm out is actually the better option for the 300 ohm ZMFs - or at least for the Verite. There’s a reason why the Pendant went to 100 ohm on the High Z, and it’s a good move in my opinion. Speaking from experience with the 300 ohm Kenzie and the Verite, while it didn’t change the FR all that much (maybe a 2dB bass boost), there was still an audible noise floor that I wasn’t able to eliminate. Contrast this with the 300 ohm Sennheisers and I had no noise floor whatsoever.
I should note, it still sounded great off the 300 ohm out, just at the cost of a little bit of noise floor. If you’re not bothered by that then no issue.
Additionally, I can only speak to the OG Kenzie on this. The Mogwai (and Forge) may be a bit different and I still need to test that - but I expect this has more to do with a particular synergy on output impedances than the rest of the differences for the amp in question.
