Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by TomB, Aug 6, 2018.
Any info against the Stellaris?
With tubes my Stellaris is 4 or 5 times the cost of this amp. The Stellaris performs better with most headphones, IMO.
Was curios to get an idea of the sound compared to something I know well. The T4 is an intriguing amp on my radar.
I spent a limited time with a loaner T4 (with stock tubes) which may have had a tube issue. However, this is exactly how I would characterize T4 with HD800SDR and HD650K.
I took the T4 loaner to a mini meet where there was also a Stratus (I believe in stock form). I thought the Stratus was definitely better especially in clarity, tone and bass. I haven’t heard Stellaris, but reading your reviews I would think T4 is not in the same league, but then again many amps probably aren’t either.
I also have T4 and tried it with Mullards as well as with Genalex. Mullards are a bit noisy tubes but very pleasant to my ears. Genalex Gold Lion (new stock) were microphonic AF so I'm going to return them. Both are T7 tubes. I also didn't like how Genalex sounded, to me, imo mids are too exaggerated. I didn't expect to hear much difference when rolling tubes but oh well, I did hear a difference between them.
One thing to add - I tested using Beyers T5P gen 2 which are probably not that optimal for the amplifier. With ZMF Verite Mullard tubes are perfect and almost no noise.
Four more T4 PCBs finished. Only power transformer and casework assembly remain.
How much heat does the T4 put out compared to the Aficionado?
Top and front: 38 °C (100 °F)
Heat from top vent: 51 °C (124 °F)
CV4024 top: 54 °C (129 °F)
2A3 tubes will produce significantly more heat.
Atomicbob's FLIR pics are illustrative of how the amp develops heat. The tubes radiate significant heat, but are really focused around the tube holes and the immediate area on the top plate.
The rest of the heat comes from the DSHA differential buffer and CCS transistors. Those are all tied into the thermal bar that conducts through the bottom plate and the rest of the metal casework. The first two pics show this. The amp's case work and knob will get somewhat toasty (warm to the touch, but not car-metal-in-the-sun hot). That's when the amp reaches steady-state and will stay that way without over-heating for over a day or overnight.
Having left the amp on several times that long myself, I may have been a bit too cautious in the Owner's Manual about powered operation. If it is standing alone in open space, it will not over-heat over dozens of hours, maintaining that somewhat toasty feeling consistently.
Bob's last note is important, though - 12AZ7 tubes and the like run 225ma heater current (12V), whereas 12AT7/12AY7 run only 150ma heater current (12V). My comments above are based on the 150ma current, only.
I should have stated FLIR measurements were taken after the T4 had been on for at least 3 hours. During lab renovation from water damage I have had occasion for the T4 to remain powered 9+ hours (CV4024), listening off and on, wishing for more on time. The T4 is a high match with one of my personal preference profiles.
Any more info on future Walnut X DAC builds ?
I should have four of them available soon.
I apologize for being absent for a while (looks like more than a month!). However, there were two T4s out in the wild with a troubling issue: Right channel dead. One was a re-sale. The other, I'm very sad to say, was the very first customer. Unfortunately, he is an international customer whose shipping costs are particularly expensive. So, we were exploring other avenues before resorting to sending the amp back to me.
In the meantime, the re-sale domestic customer experienced the very same issue - after receiving it from an original owner who had nothing but a successful experience with it. That gave us the chance to find out what was causing the issue without burning several hundred dollars in international shipping.
Apparently, the foam in the Pelican-like cases (that I thought were bullet-proof), was soft enough to allow the front of the T4 - in particular the volume knob - to strike the inside of the Pelican case front upon a very hard drop. (Sort of like NFL concussions - even with a helmet, the brain is still bouncing around inside the skull.) This was enough impact force on the Alps volume pot shaft to break the front wiper board's PCB pin connectors. (Naturally, the front wiper board is the Right channel!) The Alps pot is pretty robust as is, so this damage was all internal. There was no visible evidence whatsoever (at least before disassembly).
To be honest, the international customer had narrowed it down to this through measurement, but I was reluctant to believe it. I thought a busted Alps pot would at least manifest some static, scratching, or intermittent contact. As it turned out, these breaks were totally clean, completely severing the Right channel signal path.
Upon disassembly, I was able to detect a very tiny "blip" of a bend in the inside front plate, on the bottom beneath the pot. No one would detect it unless they were looking for it. Sure enough, replacing the Alps pot fixed the issue - with both the domestic and international T4. I just shipped back the international T4 yesterday, after successfully running it all day Friday.
So … no more shipping T4s in those Pelican-like cases! Because of that, accessories, including the case, will no longer be included. However, Doug and I are also lowering the pricing slightly, so that should make up for any lost expectation. I will let you know the official pricing change soon.
Thanks for your patience. I apologize for the delay and being absent for awhile, but I was not going to finish and ship the latest batch until I knew what this issue was and how to stop it from happening again.
In a follow up to the above post, I was the domestic customer that ran into the issue and I just wanted to say a huge thank you to both @TomB and @Roman.
I had purchased the T4 from Roman in the summer and he was a standout seller. He's the kind of person you hope you are working with when something goes wrong. He worked with me to contact TomB and send the amp off for repair, even covering shipping, so a huge thanks to Roman and I'd recommend him as a seller to anyone.
TomB was incredibly understanding and took care of diagnosing and fixing the amp. Always responding to my emails and keeping me up-to-date on the progress. And I have to say, since I received the amp back a few weeks ago, I've been listening to it for at least 2-3 hours every night and it's been absolutely fantastic. I'll post a more thorough review in the future.
Thank you both @TomB and @Roman, Super Best Audio Friends indeed...
Does anyone have a comparison of the T4 and DNA Starlett? My good friend who has knowledge of DIY said that the T4 is going to sound more unique while the Starlett is pretty traditional but to be honest that doesn't help much lol.
Thanks in advance,
Not only does it not help, but that's a very wrong way to look at things. It's like judging how a soup would taste, based on the recipe.
Fair enough EagleWings but more impressions will be appreciated.
@StageOne seems like you've had the T4 for a bit now, any impressions you'd like to share?
I've had my T4 for a few months now and the Starlett for almost 2. They are both fantastic amps with superb build quality and you can't go wrong with either. It will probably come down to your preferred headphone or system synergy.
My chain for both is Roon > RPi > Gungnir MB > Freya S > ECP T4/Starlett > HD600/HD6XX/Focal Clear
The biggest differences between the two are the Startlett has a bigger soundstage, more instrument separation, and is super smooth. While the T4 has faster transients and a bit more bottom end. For headphone pairing, I prefer the Senns with the Starlett as I can use the high Z setting and it seems to enhance the midrange on both of them. With the T4, I lean towards the Clears as the punchiness of the it works really well with the dynamic Clears.
The type of music you listen too might also be a deciding factor. I love classical/jazz/acoustic guitar on the Starlett while rock/blues sounds excellent on the T4.
I was also able to listen to both amps with a borrowed HD800 (thanks @Ntbm3) and I think the smoother treble of the Starlett tamed the peaks of the HD800. These were un-modded so if you had done any mods, it might change the outcome.
I have yet to post the T4 measurements as during data vetting I found several IMD measurements with an incorrect generator amplitude setting for the second frequency giving a slightly inaccurate result. These have been ready for months except the need for redo with correct generator settings. Problem is I have a habit of listening to the amp intended for measurement while warming up. The T4 presents a challenge as those few warm-up songs tend to turn into multiple albums and the time allotted for measurements absorbed in a most delightful way. Enjoyable listening time is far more important than measurements.
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