ECP Audio T4 Headphone Amplifier

Got it - thank you!

There is no light on the front of the case. The metal behind the volume knob is silver. I thought maybe it should be black anodized, too, but then the whole front of the case would disappear in the shadows.

The light on top is Doug's standard ECP Audio logo - a brass tag embedded in transparent acrylic. It's lit from an LED on the PCB below.

 

Reading the bit about the 75 Ohm low Z setting being for Focals, I'd be curious about any details / impressions of how the T4 compares to e.g. the DSHA-3F. More the output section I guess, because tubes. Also, that 75 Ohm is the load presented to the circuit by the output transformer, while the traditional "output impedance" would be somewhat lower, right?

 

The DSHA3F and the T4 have very similar output stages. The primary difference is that the '3F runs at low voltage and high current while the T4 runs at high voltage and low current (there are other differences that are not germane here). The T4 then uses a stepdown transformer to trade voltage for current.

The output impedance of the '3F is just a few Ohms. The output impedance of the T4 is the circuit impedance stepped down by the impedance ratio of the OPT + the primary DCR of the OPT stepped down by the OPT impedance ratio + the secondary DCR. The ratio is 100:1, the circuit adds just a few ohms (divided by 100, so it is negligible, less than 1/2 an ohm). The primary DCR is ~250 ohms which becomes 2.5 ohms while the secondary DCR is 2.2 ohms. When you total it up, the output impedance is about 5 Ohms, just a bit higher than the 3F.

Keeping the impedance contribution of the OPT low was a primary consideration in how we had them designed as this is very beneficial for the Focals.

 

Just to update you guys on how things are going. I've placed a rather large order to a local (Atlanta) metal fabricator and finisher for the T4 production casework. It should be ready by the end of the month or very soon thereafter.

Meanwhile, I finished the first production PCB and have been testing and listening this weekend. A few minor tweaks were made that seemed to have improved things even more - stronger, cleaner bass and a darker background. This is most likely due to the production PCB completely removing the transformer from the board and mounting it directly to the casework. I increased all the electrolytic sizes slightly, too.

 

I volunteer to come by and listen and then report back to the boys since I'm local

 

I offer Ice-man as tribute.

Any thoughts on a loaner? Too early?

 

Speaking of... Any idea if or when this will be available for DIY?

I need a winter project, since the garage gets so cold I can't do woodworking. Well, I could, but... Cold. You know.

 

Judging by the photo, it looks like a silver version will also be available as well as black.

 

That is black. The lighting just makes it look silver.

 

Hopefully soon, but I'll let Tomb chime in on that.

No plans for DIY on this one.

 

We are starting a loaner program next week with the production prototype shown above (red PCB). The only difference between this prototype and the actual production models are that we reduced the size of the tube holes back to 1" in diameter. We thought the smaller holes looked better and the larger ones added very little to heat dissipation.

Marv also created a Beezar sub-forum here under the "Industry Sub-Forums" section. He suggested to me that I post a bit about Beezar and ECP Audio history and how Doug and I started working together. I'll try to begin that sometime this weekend.

We've had a few hiccups in trying to get the production models ready (nothing about the amp's design, though), but we're getting close. Thanks for all of the interest and your patience. We trust you'll find it's worth it!

 

This amp is incoming this afternoon! I'll have to bring one of the kiddos along (local pickup), but she likes to ride so no problem.

 

Okay, off the cuff initial impressions...

1. Case work with aluminum chassis and polished wood looks nice. I much prefer the landscape footprint to the portrait footprint of the t3. The craftsmanship is very high level. The volume knob needs a contrasting "dot" so that I can see where I am with volume.

2. I really like the voicing of this amp. I'm using new Gungnir Multibit>t4>hd650. This is one of if not the best amps that I've heard my 650. If you just need an amp for high impedance this could be an end game solution. The sound stage is huge. Tonality is spot on and gorgeous. This is a much better amp than the t3 (based off memory).

3. There is good separation of instruments and voices. A nicely layered sound. I'm saving for gs-x mini because I need something that will also drive planars. Otherwise this amp would be on my shortlist.

4. High Z is really not working for me. I'm getting the best results from the switch in the low position. In the high position I'm hearing too much bass and somewhat exaggerated. Low position is perfect for me. I had this same experience with ampsandsound Kenzie where I preferred the lower impedance tap. This may just be a matter of personal preference. The next person may enjoy the extra bass. I thought I might be feeding the t4 too much voltage with the Gungnir Multibit, but after checking it's 2 volts and not 4 volts like I had thought over SE. Only 4 volts over balanced output.

5. Speaking of bass, it's fantastic with the t4/650 combo. The 650 bass is not always my favorite aspect of that headphone. But the t4 certainly gives it some tightness and extension that it's often lacking. This amp helps mitigate one of the shortcomings of an already very good headphone. I like this. I'm hearing good "scale" with the t4 with the 650. This is definitely a big boy amp.

6. The tone of the 650 with the t4 is something that I could listen to all day. Delicate and detailed without fatigue.


Time for more listening...on to the hd800

 

I should add that this is entirely my responsibility and was due to a family emergency. Things should be back to normal now, so we are moving forward again.

This is basically due to the interaction between the copper resistance in the output transformer and the impedance bump in the headphone. We tried very hard to keep the resistance as low as possible, and Lundahl did some clever things to help in that regard. But at the end of the day it is an issue with any output transformer based amplifier. (It is, however, much better than on the T3 or the L2.)

Every designer is looking for something different. For me, tone is king - I listen to a lot of minimalist music (Phillip Glass, etc.) where I just want to hear the instrument. The upgraded output transformers over the ones used in the T3 as well as a few circuit changes made a big difference in this regard so I'm glad you like it.

Thanks for the impressions!

 

Looking forward to impressions vs. ZDS with Utopia, since both amps are at similar price points and both claim to be (and in case if ZDS it has already been verified) heavenly match with that particular headphone.