[Freo-1]

Got some feedback on the volume pot from Mr. Plummer I would like to share:
 
" An error concerning initial rotation has more to do with the high gain designed into Millenia when used in conjunction with high output sources and very efficient speakers. The sound is output at first motion of the control but at very low levels and one channel may be audible first.  The volume control is ahead of the gain stage so it looks at everything so the tolerance is magnified at this point.
This higher gain was employed so as not to limit the volume attainable from the variety of portable digital sources people might use with lower line levels.  It is not a common problem. (Only a few affected), but they seemed to work around the issue.   It is one of the best ones available for this miniature application without something custom that would drive the price up unnecessarily."
 
 
I remain very positive about this amp.   There is nothing else on the market that comes close (at this price point) for overall performance.  Again, it is best in a Low Wattage setup, and careful attention must be paid to the speaker selection to get the best from this unit. 
Several people have reported that this unit has outperformed much more expensive amps.  I can state that it gave some much more expensive amps a good run for the money. 
 
 
 

[DaveC113]

Lol, it's REALLY obvious the volume pot doesn't track both channels evenly when used with my 2V RMS (max) DAC and 94 dB efficient speakers. The volume pot feels cheap and there's WAY, WAY too much gain in this amp as well. IMO the volume control and gain structure are a huge weak point in this amp and would be enough for me to not bother considering it or recommending it if the pot can't easily be bypassed and the gain can't be adjusted. It seems like this amp would be good for high-efficiency speakers but the gain and volume control make it so it doesn't work so well in this application... this seems really strange.

[wushuliu]

Lol, it's REALLY obvious the volume pot doesn't track both channels evenly when used with my 2V RMS (max) DAC and 94 dB efficient speakers. The volume pot feels cheap and there's WAY, WAY too much gain in this amp as well. IMO the volume control and gain structure are a huge weak point in this amp and would be enough for me to not bother considering it or recommending it if the pot can't easily be bypassed and the gain can't be adjusted. It seems like this amp would be good for high-efficiency speakers but the gain and volume control make it so it doesn't work so well in this application... this seems really strange.

I think because it wasn't designed for hi efficiency audiophile speakers but for desktop and portable devices. The audiophile performance is purely coincidental. What needs to happen now is for a proper dedicated amp to be made, based on the chip used (or the newer chips, provided they sound better). That Mr. Plummer has no plans at this time to do so is... unfortunate.

[Freo-1]

I think because it wasn't designed for hi efficiency audiophile speakers but for desktop and portable devices. The audiophile performance is purely coincidental. What needs to happen now is for a proper dedicated amp to be made, based on the chip used (or the newer chips, provided they sound better). That Mr. Plummer has no plans at this time to do so is... unfortunate.

I think you are close.  Jan did design the amp for low voltage portable units.  I also think he designed it with high efficiency audio speakers in mind.  The power supply mod stepped up it's performance to another level. 

The amp is obviously not for everyone, but one would be hard pressed to find it's sonic equal anywhere near it's price point.  There is a very good reason it was a product of the year for positive feedback magizine. 

[DaveC113]

Well...  a pot isn't that complicated. My $100 Trends T-amp has jumpers on the PCB that can be moved to bypass the volume pot, and I'd bet it wouldn't be much more difficult to reduce the gain on this amp. The fact the volume pot doesn't even track channels evenly and there is no balance control makes it unusable in my system as-is.

The TBI is a good value for the money, but it really, really needs the ability to bypass the volume pot and adjust gain. I'm sure this could be done by somebody knowledgeable enough to mod the amp, but putting a few jumpers on the PCB doesn't seem like it would add more than ten cents to the cost of the amp.

[kp93300]

I have the evaluation board with the same chip and has adjustable gain from 20 db to 36bd. In my set up, i find the lowest gain setting sound best .
My speaker is a diy V2 with powered sub and has 91bd/w sensitivity. I have a buffer for the dac ( B2) which has 2V rms output. It has no problem driving the speaker to more than 90db in my  small  room of about 200 sq ft

i agree with wushulu that the chip is very sensitivity to power supply mods and one can get great transparency with a little bit of diying in the power supply caps on the board.

DOS,

I spoke to Jan about removing/bypassing the volume pot and he said it wasn't a good idea.
I also asked him if a straight power amp was in the mix, with the same topology as the MG3 and he said no.
Perhaps if there is enough interest in a straight amp he may consider it?

Why not purchase one and figure out how to do the bypass.
I would be very interested in finding out if it sounds better.
I would do it, but I don't have the know how.

Chris

 

.

[kp93300]

Hi DaveC113
I have 2 Trends audio amp also.
This chip is much much better to my ears
cheers
kp93300

[OzarkTom]

I have had the opportunity to breakin some Vaughn Cabernet II speakers the last three weeks. Thank you Kenny.

I have three amps breaking these in. One is a high cost tube Set amp of 16 wpc, a Stello AI700 integrated, and the TBI. As long as my AC power holds up coming into my house, the AC amps all sound fantastic with these speakers. I am overwhelmed by how the TBI keeps holding its own with the high priced amps.

But last night during a snow storm here, all three amps sounded horrible on AC. It was very flat and strident. But since my wife was out bowling, I couldn't waste the evening with the system off. Happily, I switched to 12V battery on the TBI and voila, the magic was back. These Vaughns have a sensitivity rating of 100db/1 watt, so I can blast these louder than I want with the TBI. This is an incredible system. $500 amp pushing a pair of $9K Vaughn speakers. Jim Vaughn said his goal was to make high efficient speakers for the lower powered amps. He hit this right on the nail. Watch for a lot of rave reviews for these speakers in the future.

[abernardi]

  I had a chance to hear this amp when it landed here on tour (thanks trackball  ) and we played around with it on a couple of systems and both posted our thoughts.  Well, I liked the amp so much that I picked up a used one here on AC (thanks Freo  ) and have just put it into my system tonight and of course a few issues came up that maybe you guys would have some insight on.

  I'm using it to drive the low end of a bi-amped system:  Mac-mini running Audirvana > Ultra-Fi DAC 41 > Dodd battery pre-amp > Marchand XM9 active crossover (Fourth order filter slope at 500Hz) > Dodd battery amp for the highs > Avlar Prodigy AMT and the TBI (on a 12V battery) for the lows > Avlar Prodigy 8" woofer.  The TBI replaced a Virtue Sensation on 24V battery.  The Prodigy is a two way speaker with a big folded ribbon AMT with an sensitivity of 100db/1W and an 8" SEAS woofer which is in the low 90's.

  At first I turned the volume pot all the way up on the TBI and almost blew my woofers across the room.  This little amp is putting out a lot more current than the Sensation.  The thing I hate (love) about active crossovers is the added control.  Nothing makes me mistrust my ears more than having that kind of control.  I rolled back the low end significantly, and tried again.  I noticed right away that the output of the TBI differs a lot from the Sensation.  I don't have an SPL meter, but compared to the Sensation there seems to be a rather big hump as you go below 50 or 60Hz or thereabouts.  I kept having to pull back on the low end of the crossover to get that bottom octave to not distort.  I hope I didn't damage the drivers.  They were really huffing.  But the more I pulled back for that bottom octave, the thinner the upper bass got.  That's why I'm thinking the output of this amp may not be flat.  I already had a lot of attenuation on the high end, around -12dB, tried some more, almost to -20, but now the high seemed a little dull and the mid bass was still kind of thin.  Then tried increasing gain on both the highs and lows equally, keeping the same relation to each other, but that made the highs harsher.  These AMT's are REALLY sensitive. 
  I was also getting a nasty little buzz, which showed up a few weeks ago when I put the DAC-41 in the system (another story).  But now with the TBI the buzz was louder.  Enough so that it was a problem.
  So, I decided to use the volume pot on the TBI as well to see if that made any difference and it did.  I had the pot at about 12 O'clock and added gain on the crossover.  That smoothed things out a bit and reduced the buzz significantly (which I actually think is coming off the crossover).  I was going to experiment some more, but by then I had lost all objectivity.  So I sat back and played some tunes and hey, I was really getting drawn into the music - a very good sign - the midrange was sounding very sweet.  So as I left it tonight, the sound is a bit leaner than with the Sensation and doesn't have as much drive, yet that lower octave is still really potent.  Actually, I don't think I was even hearing that lower octave with the Sensation.  I feel like I need a high pass filter, it's just too much for those woofers to handle.  I'm planning to play with it some more tomorrow. 
  Has anyone else noticed a hump in the low end?  Any advice? 

[SearchOfSub]

Thank you Stephen for joining the tour. We appreciate your feedback. Stephen is sending the amp back to Rex for replacement of the AMR fuse. Are their any other candidates that want to hear the amp?

It would be interesting to hear the TBI with the IFI IDAC on a pair of Tectonic M-Lores. That would have to be a best buy system that anyone would love to own for the money. That system would fall around $1500.

So I decided to give this system a try but with the Tekton Lore-S. Do you think itll work? Do you have any cable recommendations to go with this set-up?

[SearchOfSub]

So far I have a direct-tv HD (upto 1080i only)/ Bluray player/ xbox 360.

I am going to be playing my music cd's through the bluray player. I am about 95% movies and 5% music.

I am thinking of picking up a pair of M-Lore w/ Mondorf silver oil upgrade, using the TBI MG3 for the amp and iFi iDAC as the DAC. I am in a 13 x 13 x 10 room.

is the DAC necessary?

Also, what do you guys recommend for speaker cables and interconnects? Thanks.

[electriceye]

Has anyone had any luck with a switch box for this? Would love to be able to use a turntable and dac without getting up and pulling out rcas, this is my only beef with this amp. Thinking of the decware switch box.

[roscoeiii]

There are a number of good switch boxes out there. I got one that I like which was made by Luxman.  You should be fine with any input selector of decent quality.

[OzarkTom]

The IFI Micro Itube is just out for 299 bucks. I will get one  to try out. It has a volume control with a special holographic switchable circuit built in. I was told by someone in the know, once you switch the holographic circuit in, you will never turn it off. And this includes the higher priced systems. This should give a high quality tube preamp  for the TBI without spending the big bucks.

[roscoeiii]

Don't see anything about the iTube on the iFi site yet, but all of their other gear has gotten pretty great reviews.

Look forward to hearing your impressions, Tom.

[OzarkTom]

Don't see anything about the iTube on the iFi site yet, but all of their other gear has gotten pretty great reviews.

Look forward to hearing your impressions, Tom.

The first time I saw anything on the Itube was on their Facebook page. IFI calls it their Swiss Army knife.

[roscoeiii]

Got a link with any iTube details?

[OzarkTom]

Got a link with any iTube details?

This is the only link I can find, but they are now here in us.

http://forums.hardwarezone.com.sg/headphones-earphones-portable-media-devices-314/spoiler-alert-4189579.html

[rodge827]

WOW!

Just got a look at this thing, and had been contemplating a high quality tube buffer for my system.
The boy's at AMR have gotten the iFi line right!
It's great to see a company, that is well renowned for reference gear, bring that technology to budget gear. 
Without it being some watered down, cheepo, under-performing version with their name on it, just for profit! 
I had the iPhono and the thing was amazing and performed waaay above it's price point.
I will buy another one when my listening room is rebuilt. 

Will be looking for one of these units when it hit's the market! 

Any idea of the tube used?

[roscoeiii]

Well, if just a tube buffer was satisfying enough, everyone would be using a tube buffer as opposed to a tubed preamp or amp. It also seems that the iTube won't address the need for multiple inputs, unless I am missing something here.