Totaldac D1-Driver, the (pre)amplifier driver

I am not in the habit of starting threads unless I feel a product is of significant enough importance to do so. The Totaldac D1-Driver is such a product. The official product description states D1-Driver, the amplifier driver. I have deliberately added (pre) in the thread title.

The Totaldac website description reads:

The d1-driver is an analog driver. It is usually connected to the output of the DAC.
It is an answer to the endless question "is it better with or without preamp?".
The strength of preamps is there active stage more than their volume control. The active stage helps driving the power amp.

It was designed for directly driving a power (or integrated amplifier!) using the built in Totaldac digital volume control:

Its drive capability allows the d1-driver to improve the sound of a DAC, improving bass control, articulation, presence, soundstage and life. It has been tested when connected between a DAC and a power amplifier (transistor or tube), but also between a DAC and an integrated amplifier. The d1-driver has no volume control because it relies on the DAC volume control.

Around 6 weeks ago we travelled to Slovenia to deliver a SGM Extreme server to Matej Isak for a review. I ended up leaving being deeply impressed by the liveliness and dynamic range of Matej's reference system. Upon asking Matej told me something about the importance of proper gain matching. I did not give it much further thought until we visited forum member Mike Lavigne a few weeks later where he played a few tape cuts with a similarly shocking display of brute force dynamic range. Every since returning I have been searching for explanations for this particular phenomenon. Until I received a pair of Totaldac D1 drivers from Vincent last Friday.

I need to add a bit of history context to this now as I was not unfamiliar with the D1-driver. I have tested an older version before, the current D1-driver is in its second generation now. At that time I was impressed by its dynamic range and transparency, but found it lacking in refinement and micro detail rendering compared to my AudioNet Stern (Euro 35.000) preamplifier. If I remember correctly my commentary to Vincent was "a diamond in the rough". It also did not manage to match the Stern's sound staging abilities, upon which Vincent commented I would probably need a pair to get there. I shipped it back and did not give it much further thought, therefor the penny did not drop until Vincent told me he had a MK2 version of which he was confident it would solve my "issues" and if I would be interested in trying a pair of them. This turned out to be a totally different ballgame. Not only does it manage to match the Stern's sound staging abilities, refinement and micro detailing, it has also improved upon its previous strengths with even better dynamics, and an "Iron grip" control over the lower registers which sounds like it has doubled the already high damping factor of my AudioNet Heisenberg power amplifiers. It has incredible control and slam, at first I thought it was lacking low end extension, but after some back and forth switching it is just much better defined and controlled turning a mass of "1 tone bass" into a variation of cues and pitches. It does give me the eagerly desired dynamic range I found my system lacking of after hearing Matej's digital and Mike's tape. Therefor I consider it to be a substantial product worthy of its own thread.

Using both the Stern and D1 drivers in a DAC - Driver - Preamp configuration does preserve most of these qualities with just a slight decrease in overall transparency, clarity and a loss of ultimate "control". Inserting the Stern creates a slightly more distant, slightly more laid back perspective, where just the drivers give you a closer more direct perspective.

Matej Isak has reviewed the D1-direct and D1 driver here, worth a close read:

https://www.monoandstereo.com/2019/09/totaldac-d1-direct-d1-seven-d1-driver.html

I will copy a few relevant snippets:








To summarize, this is a product to seriously consider, not just to combine with a Totaldac DAC, and not only to replace a preamplifier. But consider trying it with any brand DAC and/or any Pre-amplifier.

 

Vertere are absolutely amazing cables. They commanded my respect early on and are expensive. They are on the same level as Steve Nugent's reference cable. I use to purchase them out of the UK without any issue.

I recommend Vertere without reservation.

I see you import the Waversa line of products. They seem to have a high end router and switch. Care to let us know more abou them. They might be a good fit for an Extreme based system?
https://www.kevalinaudio.com/product-page/waversa-wrouter

 

The administrators here have been gracious to allow me to write about Waversa under the Manufacturers section of WBF.
https://www.whatsbestforum.com/threads/w-router-ultra-low-noise-audio-grade-router.30735/

I was lucky to be introduced to Vincent and TotalDac through a mutual friend, Paul Hovenga of Many Moons Audio. Vincent's creations are enjoyed on the daily, including two D-1 drivers!

 

The administrators here have been gracious to allow me to write about Waversa under the Manufacturers section of WBF.
https://www.whatsbestforum.com/threads/w-router-ultra-low-noise-audio-grade-router.30735/

I was lucky to be introduced to Vincent and TotalDac through a mutual friend, Paul Hovenga of Many Moons Audio. Vincent's creations are enjoyed on the daily, including two D-1 drivers!

I missed that. Thanks.

 

What is this analog jitter?

Analog compression as well as digital jitter.

 

Re: cables that is true. My former Neumann mastering desk was partially rewired at Columbia with Belden....

When I rewire analog signals, I use pure silver OCC wire with cotton insulation and usually twisted-pairs, signal and return. A lot of damage is done to analog signals with dielectrics, including conformal wire insulation and even FR4 epoxy circuit boards with long traces. I avoid it like the plague. I learned these lessons from 10 years modding other companies components, including pro-audio stuff.

Another thing I avoid like the plague is stranded copper wire with no plating on it. Silver or tin plating is fine, but never bare stranded copper wire. The oxidation kills the audio quality, even for power supply feeds.

 

Here are updated photos of the d1-driver.

Rear view of the stereo version:


Rear view of the monobloc version:

 

For clarity.

If you have an unbalanced preamp or amplifier receiving the signal, two stereo units set up as mono blocks would be the same as the monoblock version.

Only when feeding into a balanced circuit would monoblock be required for a true balanced signal.

I have single ended circuitry throughout and later purchased a second d-1 driver for better signal separation.

 

For clarity.

If you have an unbalanced preamp or amplifier receiving the signal, two stereo units set up as mono blocks would be the same as the monoblock version.

Only when feeding into a balanced circuit would monoblock be required for a true balanced signal.

I have single ended circuitry throughout and later purchased a second d-1 driver for better signal separation.

Yes it is similar in this case.

 

I have single ended circuitry throughout and later purchased a second d-1 driver for better signal separation.

John,

how big is the SQ difference in your case between one and two single ended drivers?
Thanks

Matt

 

Question for Vincent. If you have a customer who will run two units in a unbalanced system, would you recommend monoblock configuration and if so, why?

The benefit of separating channels may vary depending on the signal implementation downstream.

I was immediately impressed and felt the investment paid benefit. True separation of signal and independent power supplies. Any other benefits I am not considering?

 

Question for Vincent. If you have a customer who will run two units in a unbalanced system, would you recommend monoblock configuration and if so, why?

The benefit of separating channels may vary depending on the signal implementation downstream.

I was immediately impressed and felt the investment paid benefit. True separation of signal and independent power supplies. Any other benefits I am not considering?

I would recommend getting monoblocs with RCA + balanced outputs so you can accept any amplifier.

The soundstage is also larger in all directions, with the monobloc version.

 

I would recommend getting monoblocs with RCA + balanced outputs so you can accept any amplifier.

The soundstage is also larger in all directions, with the monobloc version.

Balanced is certainly better for several reasons, including common-mode noise rejection and higher amplitude and thus higher signal to noise ratio, however using the term "true balanced" should be done with a grain of salt.

Most analog balanced outputs on modern equipment, except for maybe pro-audio are not "true balanced". This is because they are driven directly from solid-state or tube circuits and not through a transformer. The original pro audio balanced configuration was always through transformer and terminated with 600 ohms. This has a number of benefits, including the fact that even cheap balanced cables will sound great. The downside is that the transformers must be very good quality and the drivers must easily drive 600 ohms, both adding cost and challenges.

When there is no transformer in the circuit, it cannot be truly balanced because the + and - signals will never be exactly the same amplitude. Impossible. There is also the issue of the + signal and the - signal having the same dynamic characteristics and linearity over frequency. Also difficult to achieve.

This is why I developed the Final Drive transformer isolator/converter. It changes the balanced signals to "true-balanced". The sound quality improvement is obvious with most amps.

 

For some, "true balanced" means that it is not just an unbalanced signal over a XLR connector
For some it means that it uses signal transformers (even if 2 taps in a transformer are never exactly similar, so not perfectly balanced)
For some is means that the amplifier as two fully independent amplifiers per channel, one driven by the positive signal, another driven by a negative signal, making a bridged amplifier in reality with the associated output impedance and spectrum.

Balanced helps to manage ground loops and noise in complex and noisy environnement, but in high end hifi it is easy to manage a very low noise with unbalanced interconnects, avoiding signal transformers or un-necessary extra electronic circuits.

My current system uses two d1-driver monoblocs, with RCA interconnects, and I get no noticeable noise even on this 105dB speakers

 

For some, "true balanced" means that it is not just an unbalanced signal over a XLR connector
For some it means that it uses signal transformers (even if 2 taps in a transformer are never exactly similar, so not perfectly balanced)

One should not use the term balanced unless it is, and true balanced requires a transformer.

"taps" on a transformer should not be used for balanced signaling. It is a simple 2-winding transformer on one or both ends. The difference in windings will have a slight effect on amplitude, but not distortion. If there is a tap, it is in the center and used at one end for DC common, but usually not necessary. Sometimes it is wise to earth-ground the transformer steel. Without the transformer, the difference in the two signals will cause distortion.

 

Wikipedia's definition of fully balanced in audio.
https://en.wikipedia.org/wiki/Balanced_audio

"A small number of audio products have been designed with an entirely differential balanced signal path from input to output; the audio signal never unbalances. This design is achieved by providing identical (mirrored) internal signal paths for both the "non-inverting" and "inverting" audio signals. In critical applications, a 100% differential balanced circuit design can offer better signal integrity by avoiding the extra amplifier stages or transformers required for front-end unbalancing and back-end rebalancing. Fully balanced internal circuitry has been promoted as yielding 3 dB better dynamic range, though at increased cost over single-ended designs. "

This is the way the d1-driver monoblocs XLR to XLR works, without signal transformer. I don't mean that it is better than anything else, it is just the way it works.

 

Wikipedia is mostly but not 100% accurate.

 

... The original pro audio balanced configuration was always through transformer and terminated with 600 ohms. This has a number of benefits, including the fact that even cheap balanced cables will sound great. ...

Now thats worth having

 

We are focused so far on balanced output, but not a mention of inputs. If a circuit is 'fully symmetrical' you lose the cmrr of a balanced receiver circuit, no?

 

Steve and Vincent - thank you for this ongoing dialog. I found it valuable and appreciated.

 

Following the useful advice from members of this forum (thank you to all), and Vincent’s usual efficient delivery, I am now enjoying the significant benefits of having a pair of d1-drivers in place between my d1-direct and active monitors.

There were also some recommendations earlier this year to look at adding a passive preamp (typically an A-TVC). I have a need to manage the overall gain to a greater amount than the optimum area of the TotalDac digital volume control allows , so I am now exploring this idea further.

Recently hearing the designer of the PSAudio BHK preamp speak on YouTube about his need to have a mental model of how the technology works as well as actual listening – I recognized that this is something important to me too.

My current understanding is that the impedance impact of a transformer volume control should work well together with the effect that the d1-drivers are having (protecting the DAC from the activities of the power amps and providing enough “energy” to drive the audio chain well).

There seem to be two arrangements that could work:

• d1-direct > d1-drivers > TVC > poweramps
• d1-direct > TVC > d1-drivers > poweramps.

It feels like it would be safe to try both arrangements and see which sounds best.

Any thoughts from those that have tried something similar ?