I always set out with the objective of making my designs as unobtrusive as possible. I am never aiming to deliberately add colour but to provide the lowest noise and distortion within the capabilities of the technology. You can design tube stages to add deliberate colour but I do not. I spent a lot of time in the early days trying different tube topologies trying to find one that provided low distortion without NFB. I discovered the mu follower and the 6SN7 tube which together are capable of excellent performance. My classic mixer designs use a 6CG7 mu follower (a 6CG7 is just a 6SN7 in a B9A envelope) or the more compact 6922.
The only problem with mu followers is they have a limited drive capability - they cannot drive 600 ohm loads to professional levels. After a lot more work I came up with the Eurochannel which has the same low distortion as the mu follower but can drive over +20dBu into a 600 ohm load. Both designs have very similar sonic signatures and are designed as far as possible to be transparent. Having said that, many people who have built them say they really like the sound.
First a quote by Sirio Balmelli who purchased my very first all tube mixer:
"The CTC-1 is the best mixing console I have ever used. There is no reservation on that statement. The slew rate (transient response) and noise floor figures are competitive against it's classic solid-state brethren, but the low and high end are (dark) magic. There is a very perceptible tightening effect in the bass frequencies, and the highs are smoothed over the tiniest bit. The midrange is extremely clear. Stereo separation is nearly absolute. Don't be fooled: this isn't the tube one-trick-pony that "glues" everything together. A super-polished late 80's style mix going through the CTC will maintain every inch of percussiveness and every mile of reverb tail. It will handle an EDM mix with aplomb. It keeps and enhances the details and quiet elements in a mix. Somehow, it lends a very tangible sense of cohesiveness and realism to the entire mix, without being obtrusive. I find myself not "mixing into it" but rather doing less processing to the source tracks themselves - and somehow getting a superior result. It doesn't distort - even when nearly clipping my stereo ADC (with a 10dB pad on it!). I admit, this review is a bit skewed - to tone down on the superlatives so it remains credible. With a product like this the analog/digital, audiophile, summing, dithering and other debates simply don't apply. It puts a smile on my face every. single. time. that I use it. I regularly get sceptical and bypass it or A/B it against something else - and I put it right back in. End of argument for me - the CTC-1 is a keeper. An enormous thank-you to Ian Thompson-Bell for the magnificent work. Sirio"
Here's what Ben Melnick said about his mixer:
I have been enjoying the EZ Tube mixer now for a few months and have put it through its paces as a mixer, channel strip, and even a 2 channel mastering processor! Whenever I get something in that is new, I immediately have to test it against things that I know to be great in my studio. I have to say, there is not one area where the EZ Tube mixer did not excel! It was either on par or better than my best equipment!
As a preamp - rich and detailed. I have a really great tube preamp in my studio that has been built with hand wired transformers. The EZ Tube mixer used as a preamp without the eq in sounds as clear as amazing as this pre! However I find the EZ Tube preamps to be able to give a richer warmer midrange on certain settings. Also, I find that the EZ Tube preamps are amazingly quiet with ribbon microphones! This is one area where my other prized preamp falls a little short!
As a channel strip I found the EQ to be very beautiful, and I once again have a Pultec style EQ with hand wound inductors and transformers! The EZ Tube Pultec EQ's are nearly identical to the sound of this Pultec style EQ I have, and that is saying a lot! Just switching in the EQ on the EZ Tube gives a magic to the sound, and I have found that ribbon mics and dynamics have not sounded better than with a channel strip of the EZ Tube mixer. Period.The STC 4021 "ball and biscuit" is one of my favorite mics.... I have an old Brenell reel to reel electronics that really makes this mic shine and give it a magic nothing else can do. Only one problem - it is quite noisy. Could you imagine my surprise when I plugged the STC 4021 into an EZ Tube mixer channel and turned on the EQ -no hiss and even nicer tone!!
As a mixer the EZ Tube is great! Using my 4 channel analog multi-track machines I found this mixer to be all I need to get the song to CD. The headroom is amazing - you can pretty much drive this mixer as hard as you want (to quite a high point before distortion) and the mixes become loud and strong to CD! You don't get that hash or smear that you get when pushing lesser mixers. The sound stays open and clear and smooth!
As a 2 channel "mastering" device, I found that a 2 track mix ran through 2 channels of the mixer yielded the same loud clear sound I previously
could only get by daisy chaining 3 high quality processors together before! It was almost comical how just the EZ Tube mixer alone could get those
mixes big and strong to CD!
The nice thing about the EZ Tube mixer is that it is so much more than a mixer: Great preamps, great EQ, or combined channel strip, a "mastering processor" if you dare, and of course a fully functional mixer for "summing" purposes or just good old analog mixing from any analog recorder. If I could only keep one thing - ok 2 things - (not counting mics haha!) it would be my EZ Tube mixer and one nice analog recorder. That is all you need to make beautiful real music with soul!
Holger Classen built a 12 channel mixer based on my EZ Tube Mixer design which he calls Krassemaschine. This was reviewed by Fritz Fey in Studio Magazin. Fritz said:
"The Krassemaschine sounds 'better than reality' and refines every signal in a specific manner. It is a unique item with a spectacular sound signature which makes the heart of every sound engineer leap. (...) But caution, this sound will lead to dependence and the way back to 'normal' will be arduous"
jensenman of groupDIY said "Awesome is pure understatement. I´ve yet to hear a better sounding desk..."