Bottlehead SE Experimenters Amp Mods 2016
Here we are again. Perhaps perspective is everything. This I keep learning over and over.
I’ve had the Bottlehead Single-Ended Experimenters (v2.1) amplifier for over a year, and after a handful of mods and 10 months or so, I shelved it for a few months. The Ampsandsound Mogwai amp is my latest addition, and was intended to be my primary amp for both two channel and headphone listening. It’s a great amp – and I think an excellent value – it’s covered here. All the while, I’ve been feeling guilty about neglecting the Bottlehead amp. I hadn’t dressed it up the way I wanted – initially, I was in a rush to listen to it. Well, we’ve remedied that.
I made some cosmetic changes. The grey finish on the base and multiple gloss coats make for a nice feel. Painted the hardware white, and added a silver volume knob. Simple changes that for me bring the appearance closer to its perceived level of performance.
About that – this is Bottlehead’s earliest kit, and so not their best performing, or newest amp. But with the mods they’ve offered, and the capacitor and stepped attenuator upgrades I added it handily competes with the handful of headamps I’ve heard. Those range from $300 to $1800 in price.
More importantly, I’ve replaced both the .1uf caps and 1.5uf output caps with Jupiter Copper&Foil capacitors. So far the output caps have great tone, texture and weight with additional extension in the high freqs in comparison to the Jupiter HT caps I had in before. Bass performance is generally better too – not clear how much of this is the new caps design and how much is the rating. I had the Jupiter HT 2.2uf output caps in before, and these are 1.5uf – like the stock caps – so, I’m unable to make a direct comparison.
Need to give them a lot more time before making any final impressions on sound quality.
Whoa. This is what I’ve grown to love about diy audio – first, you can get world-class sound with Bottlehead kits. Next, you can experiment with the capacitors, for example – see for yourself how they affect the sound quality. In a circuit like this, it’s significant. These Jupiter Copper&Foil caps are phenomenal. I’ve not compared them to other brands…yet. But now I know from experience (extended listening) that the Copper&Foil are worth the investment, if you are inclined make the leap. Of course there are numerous brands and designs on the market to satisfy your own needs – Teflon, SIO, paper and wax. All deliver a different sonic character – at least from what I’ve seen on the forums and from folks who’ve been doing this a long time.
And while experimenting is simply fun regardless of outcome, I knew the Jupiter caps were going to be the right choice based on prior reading. The eight caps I’ve purchased do represent a larger investment than the initial kit did. That’s ok – the learning, and ultimately the incredible sound quality it’s now delivering are worth the cost. And, it’s possible the current build is still less expensive than a comparable commercial offering when it comes to sound quality.
A note on my listening tests:
I’m running both amps, feeding them from the dual SE outputs on the Yggdrasil, and both with Anticable RCA interconnects. So, I was able to switch quickly and eliminate as many upstream variables as possible.
The Mogwai outputs 1.8watts RMS @ 1khz, 7.6VRMS to the 32 ohm headphone output. 3 watts into my 8 ohm Tekton Lore. The SEx amp outputs 2 watts. I’ve mine wired at 8 ohms because I was driving the speakers too, initially. The Nighthawks are 25 ohm ‘phones, so the 8 ohm setting works fine. Of course, the SEx has a bit of noise audible with these sensitive ‘phones. With my AKG Q701’s (62 ohm) this hum is not audible.
The Mogwai is more muscular – which shouldn’t come as a surprise – using the Gold Lion KT88 for power duty. The mid-range is clear and bass is excellent. It’s silent when driving the Nighthawks. Of course I can’t turn it up to 9 o’clock so I feel I’m not hitting the Mogwai’s sweet spot. Again, I use it to drive the speakers almost 100% of the time now that the SEx is back on the rack.
It also has great bass, though driving speakers it can’t compete when it comes to stage size, grunt and low end performance. Where it outclasses the Mogwai is with its natural tone, clarity and nuance and micro-dynamics. The attenuator, and cap upgrades have pushed this little amp to a fantastic level of musicality.
When driving headphones, the SEx is the more musical amp. This is saying a lot, because the Mogwai is great. With the current SEx build, I’ve got approximately $1k invested. The Mogwai runs for $1800 at this time. Again this is less a knock on the Mogwai and more a testament to Bottleheads efforts to create affordable world-class amp circuits for diy’ers. If you like to build, and want great sounding gear, it seems like a no-brainer. They are cheaper because they dispense with the fancy casework, and parts in some cases. The beauty is you are free to upgrade as you see fit. I have certainly proven for myself that sonically they compete way above price class.
I’ve been thinking about my next project build since I grabbed the SEx amp. Still thinking the Stereomour II is the best choice for my system, room and listening habits.
Now, what do I sell to fund that purchase…