[Freo-1]

 With the continued interest in this little amp, thought it appropriate to start a new thread about the modifications that can be made or are available to enhance its performance.
 
I’m not one to get into hyperbole about “what’s better”, as those arguments are like teaching a pig to sing (A: it is not achievable, and B: it annoys the pig).  What makes more sense is to discuss a products strengths, limitations, and observed comparisons between products for a given environment/setup.  In the final analysis, one’s own judgments (and ears) should be trusted above all.  Having stated the above disclaimer, on to the subject at hand.
 
The TBI Millenia’s performance is a league well above its pay grade.  There is a LOT of gear that costs several times the price of this unit that, in most low wattage applications are not going to provide the same level of performance that this amp can provide. 
 
The amps provide a lot of flexibility in stock configuration, in that it can operate from both 24 VAC and 12 volt internal battery.  It also has the ability to be connected to a SLA battery setup from 12 to 24 volts, making it very flexible for usage in low wattage applications.  Additionally, if one has speakers in the 87/88 db/watt range, an additional 30% of power can be achieved by using a pair in mono.  The mono configuration also provides lower distortion, runs cooler, and allows for individual adjustments of each channel.
 
So far, the modifications have centered on the following:
1.     External Battery Power Supply: Provides a significant improvement in sound with stock amp
2.     Upgraded Binding Posts: Provides improved sound
3.     Upgraded RCA Jacks: Provides improved sound
4.     Upgraded Fuse: Meant to provide improved connection to the power supply
 
The battery power supply with the Stock Amp provides the largest improvement to the playback.  The results are detailed in another thread, therefore, no need to repeat them here.  The binding posts and RCA jack upgrades speak for themselves, and upgrading these does provide an improved performance.  The fuse upgrade is also meant to provide a cleaner signal to the power supply.  The audibility of replacing the fuse is hard to quantify.  Personally, I did not hear much of a difference when the fuse was upgraded.  Taking in all of the upgrades mentioned above, one can achieve outstanding audio reproduction from the stock amp with the aforementioned upgrades.
 
Recently, Jan Plummer at TBI offered an upgrade to the power supply filtering section of the TBI.  He came up with the upgrade after a lot of interest was generated here at AC (and elsewhere) about power supply connections.  After all, at its most basic level, an audio amplifier is simply a device that provides voltage and current gain by modulation of the power supply, hopefully as close to the input signal as possible, only with more power to drive the speakers.  The modification is fairly basic: An addition of couple of filter caps and resistor to handle the loading of the external power supply.  The modification was designed (optimized) primarily for use with the 24 volt AC supply.  The modification absorbs the variations placed on the power supply by reproducing the input signal, thus proving more linearity in operation.
 
So, I re-connected the TBI amps to my audio only system, and sat down for a listen.  The system used consists of the following components:  MHDT Havana (Balanced) DAC, Modwright Oppo BDP-95 (Tube) player, a Conrad Johnson clone preamp (consists of 4 12AX7 tubes line stage), two TBI amps in mono, Cary Silver Oak Model One speakers, and a Genesis G928 subwoofer.  CD and DVD Audio used the MHDT, and SACD/Blu Ray was via the Oppo.  The amps were on the AC power source.
 
The first disc was Rachmaninoff Piano Sonata #2; a piece I’m very familiar with (CD).  I was surprised at how much of an improvement the power supply modification made to overall playback.  I was expecting a modest improvement, but this was significant.  It sounded even better now on the AC than using batteries.  Even my bride remarked how realistic the piano playback sounded, as if we were in the room with the musician.  I then tried a DVD Audio of the Eagles Hotel California.  I had always thought that the DVD A was a little brittle, but with the TBI, that was gone.  Instead, one was treated to a performance that made one think you were listening to a first generation master tape.  From there, tried the Pink Floyd Dark Side of the Moon SACD, which was never better.  Then tried a couple of older rock/jazz CD’s, and was duly impressed.  One of the near unique qualities of this amp is to make old recordings sound more enjoyable, in that it plays back the performance without overly emphasizing the limitations.  In short, the power supply modification showed improved performance from every disc and music type that was tried.
 
With the upgraded power supply modification, the TBI gets even closer to emulating the best qualities of a SET tube amp, but with some noticeable differences.  The bass is tighter and more natural sounding; the treble is a bit more extended, but totally non-fatiguing.  The presence region is where this amp really shines.  One almost thinks that the music is coming from a very pricey SET, not a Class BD amp. 
 
TBI is offering the upgrade to all existing owners of the amp.  I would strongly encourage existing owners to contact your amps reseller (or TBI directly if you can’t contact your reseller for whatever reason), and get this modification done to your amp.  I am still amazed that this upgrade improves the amp as much as it did. 
 
Lastly, I have used a variety of amps with the above system, and the TBI amps in mono has provided more musical enjoyment than any other amp I have tried to date. 

[cab]

And a class d at that.....

Thanks for posting the details...

[hoxuanduc]

Freo-1,

Much thanks for your impression and detailed upgrade.  May I ask what brand of RCAs, speaker binding posts, and fuse you'd recommend?  It's probably buried somewhere in the other thread.

Thanks,

Duc

[Freo-1]

And a class d at that.....

Thanks for posting the details...

Indeed.  I have not cared for Class D amps in general, but this specific unit is truly the exception.  There is just enough unique topology to this amp to make it stand apart from the other Class D amps I have heard/used/owned.

[Freo-1]

Freo-1,

Much thanks for your impression and detailed upgrade.  May I ask what brand of RCAs, speaker binding posts, and fuse you'd recommend?  It's probably buried somewhere in the other thread.

Thanks,

Duc

 
No worries.  The binding posts and RCAs are all Cardas, available at the parts connection. The fuse is AMR 3.15 Euro fuse.

[OzarkTom]

My buddy Rex has tried numerous brands of RCA's and binding posts, so far the Cardas has been the best. The Cardas RCA's is not his favorite to use since he has to do a lot of grinding for these to fit.

There is another highly regarded brand that he is going to try next month, the company had all of their stock bought out from someone in Europe recently. Those should fit with no grinding.

[rodge827]

Freo-1,

Nice write up  ...are you using any kind of AC line conditioning with your system?

[Freo-1]

Freo-1,

Nice write up  ...are you using any kind of AC line conditioning with your system?

Yes.  I have the two power supply units plugged into an Adcom ACE Line Enhancer.  Nothing fancy, but seems to work well with the TBI power supply.

[wcvb]

First a disclaimer:
I'm the Caribbean distributor for TBI.

I've modified my Millenia as well.  I've changed the RCAs and binding posts and replaced the fuse with the AMR 3.15A fuse.  I'm awaiting parts to do the power supply mod.

The binding posts I used were WBT 0703s http://www.wbt.de/fileadmin/ppr-ftp/WBT-0703_Cu_Datasheet.pdf

The RCAs were WBT 0210 Cu. http://wbt.de/index.php?id=73&backPID=73&tt_products=56

[Rclark]

And a class d at that.....

Thanks for posting the details...

Yeah no kidding. In the past Freo was vehemently opposed to class d, and look what happened. It's true, it's a whole new world, class d will soon be the king if it already isn't.

[OzarkTom]

First a disclaimer:
I'm the Caribbean distributor for TBI.

I've modified my Millenia as well.  I've changed the RCAs and binding posts and replaced the fuse with the AMR 3.15A fuse.  I'm awaiting parts to do the power supply mod.

The binding posts I used were WBT 0703s http://www.wbt.de/fileadmin/ppr-ftp/WBT-0703_Cu_Datasheet.pdf


The RCAs were WBT 0210 Cu. http://wbt.de/index.php?id=73&backPID=73&tt_products=56

Those look nice. I will probably have to try those. Did you have to do any filing or alterating the chassis?

[wcvb]

Hi Tom,

I had to make some changes to the case.  I had to enlarge the holes for the RCAs and the binding posts.

The WBT 0703s were larger than I thought they would be.  I now think that the WBT 0708s (http://www.wbt.de/fileadmin/ppr-ftp/WBT-0708_Cu_Datasheet.pdf) would be better as they are a bit smaller.  I'm going to use these for my next mod.

I'll post some pictures in a couple days.

[Freo-1]

Yeah no kidding. In the past Freo was vehemently opposed to class d, and look what happened. It's true, it's a whole new world, class d will soon be the king if it already isn't.

Don't go overboard here.  Up to now, the vast majority of Class D amps still do not sound all that musical.  This unit is a major exception.  The topology is quite a bit different from most other Class D amps.
 
 
It does bode well for the future.

[wisnon]

First a disclaimer:
I'm the Caribbean distributor for TBI.

I've modified my Millenia as well.  I've changed the RCAs and binding posts and replaced the fuse with the AMR 3.15A fuse.  I'm awaiting parts to do the power supply mod.

The binding posts I used were WBT 0703s http://www.wbt.de/fileadmin/ppr-ftp/WBT-0703_Cu_Datasheet.pdf

The RCAs were WBT 0210 Cu. http://wbt.de/index.php?id=73&backPID=73&tt_products=56

Where are you located?

[wcvb]

Hi wisnon,

I'm in Trinidad and Tobago

[wcvb]

Hi,

As promised here's a picture of my modified Millenia:



Regards,
wcvb

[Rclark]

Looks a whole lot like a Virtue. It will be neat to pick up on Monday.

[Rob F]

A friend has just bought one of these amps. I had a look with him at the innards. I think there are more fundamental improvements which could be made to the amp than have been attempted so far.

The first thing that struck us is that there is an electrolytic input coupling cap. I suspect a coupling cap is needed because the opamp buffer has a single rail supply. If you are using the phono inputs only the coupling cap could be removed or simply bypassed and a film cap wired direct to the centre pin of the phono socket, the cable to the board would then be soldered to the other end of the cap. I recall the input coupling cap being 10uf, which if I am right is likely to be a much larger value than necessary. It would be necessary to disconnect the input on the front panel from the board if removing the cap.

Secondly, while the binding posts are industrial quality, the output cable is wired to a metal tag on the posts (which is retained against the posts by nut and washer) rather than directly soldered to the posts themselves. Righting that should help reduce the damage done by the original posts to the sound. Alternatively do a Ric Schultz by drilling a chassis hole, routing the internal speaker wire though it and loop stripped ends of the wire onto the posts. You can then have a direct wire to wire contact with your speaker cables.

The front panel input avoids the longish interconnect from the phono sockets to the board, using this with conventional interconnects would be problematic without disfiguring the front panel with a set of phono sockets. Still if it is solely better sound you are after...

I also seem to recall that using the headphone socket mutes the output, is that correct? If so, there is a switch there begging to be bypassed. Once again that involves a compromise, but if it is better sound you seek...

Rgds

Rob.

[OzarkTom]

Hi Rob, TBI welcomes DIY'ers to mod their amp. If you can bring up any improvements, feel free to post them here.

One easy mod I did was just to replace the stock cord with a $25 Pangea AC-14 power cord from the Audio Advisor. That opened the sound up even more.

[jtwrace]

Tom

I'm sure it's been mentioned but I haven't seen it.  Can you tell me / us about the company?  Where it's made, who designed it and how he has gotten to this point?