Gorgeous! The curved joint is amazingly powerful.

But but but... details! Any tidbits about the topology? Which tubes, and are we looking at a pair of matched pairs, or a matched quad? Tube gain, input and output transfos, or something else... Does "Copenhagen" still mean there is a SS pentode inside?

And just selfishly, is the output Z Focal-friendly?

The Copenhagen is a differential cascode circuit. The Copenhagen V uses tubes (valves) for the upper device, while the Copenhagen S uses transistors (sand). They are otherwise just about the same. It does indeed use input and output transformers (amorphous Lundahls in both cases, though the inputs can use mu metal instead). The tubes (E81L's) need not be matched at all.

It is what is often called a "transconductance amp". In essence, it uses the headphone's impedance as an I/V converter, and it takes advantage of the slight Sennheiser impedance bump to make it a bit more euphonic. When used with Senns, I'd describe the sound as happy and punchy (kind of making them sound like how Grados would sound if they were not grating) - some people hate it, others love it, but it definitely has a sound. It can be linearized with the addition of some parallel resistance on the output (this is what a triode amp does except the parallel load is the tube plate impedance). Without doing that, it is not great with the Focals. Even with, they are so poorly damped that it would not be my first choice for powering them. With phones that have a flat impedance, it is pretty neutral. It's not an amp for everyone (definitely not for the objectivist crowd), but it is my favorite these days - I use a Copenhagen S with 650's for most pleasure listening.

Edited April 13, 20188 yr by dsavitsk

Damn Doug! I can't express how beautiful those are! Just wow!

^^^ What he said.

^^^definitely!

Yes.  Awesome!

I still have a couple of prototype amplifiers available. One is a Black Diamond with an upgraded power supply ($1100). The other is a DSHA2 ($1200). Both amps use transformers for gain. More information at http://ecpaudio.com/stuff.shtml, or send me a PM.

I auditioned the blue DSHA-2 before and that's a great sounding amp.  If not for owning the Ravenswood and L3, I would buy that in a hurry.  

The T4 is now available for preorder. More info at Beezar.com.

Looks great, Doug. Goodbye, torpedo shape!

More like good riddance!

The  prototype T4 sounded amazing during the ATL minimeet.  Has it got even better?

Edited August 14, 20188 yr by purk

Is amazing not good enough?

1 hour ago, dsavitsk said:

Is amazing not good enough?

This is Headcase. There are many levels above "amazing" -

uber amazing,

holy frickin' shit amazing

The Mother of All amps  amazing 

and of course "I eargasmed" amazing.

Not to mention the Infinite Jest-esque "it is so amazing that people who listen to it literally die from happiness!"

8 hours ago, dsavitsk said:

Is amazing not good enough?

With your amps, "sounding amazing" is just the norm. 

On 4/13/2018 at 1:52 PM, k1arg said:

Gorgeous! The curved joint is amazingly powerful.

                                   You're so right!

Edited August 16, 20188 yr by Voltron

The internal pictures are gorgeous, hard to convince myself not to pull the trigger

Maybe this is a good time to repurpose the T3 design into a phono stage #wishfulthinking

So what are the differences between this and the L3?

Also now that the torpedo series isn't DIY anymore, is there any major difference in how you approach the T4/T5 and the other ECP amps?

The L3 is a single feed (not single ended) differential tube amp. The T4 is a parafeed differential hybrid amp. The T5 will be, if it every gets done, a more powerful version of the T4 that also does away with the parafeed cap.

The T4 was designed to be less expensive by reducing the power and by eliminating a bunch of assembly labor. But within its output limits I think it is 98% of the  quality of the other amps. There are of course a few things you can do with a higher budget, but they are mostly gild on a lily.

I hope that your T5 will sound worst than the L3 that I have.....

10 hours ago, purk said:

I hope that your T5 will sound worst than the L3 that I have.....

Probably not

7 hours ago, recstar24 said:

Probably not

I heard the prototype T5 and it was more or less the same as my L3.  Of course, that was a prototype unit.