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Fool On The Hill » Blog Archive » DIY Audiophile Quality Amplifier

Would anyone be interested in reading about my latest DIY project? It involves building an audiophile quality amplifier that can run with the big dogs – you know, amplifiers that cost many thousands of dollars. The kind favored by audiophiles who can ‘hear’ the difference between a power supply and an SLA (Sealed Lead Acid Battery). They swear they can hear the difference between speaker cables and insist that tubes and vinyl are not dead. When they talk about their equipment it sounds like they are describing fine wines. If this sounds out of your class, please keep reading.

This project first piqued my interest a few months ago when I read a news story about a ‘toy’ amplifier that people were saying unbelievable things about. It is readily available on the web and costs around $20-$30 depending on where you buy it. Out of the box it sounds OK. After a few simple modifications, it moves to a whole new level. My son and I have had a blast building and modding our first amplifier, but we’ve enjoyed listening to music on it much, much more. The first thing I listened to was a Mozart CD. It sounded horrible (noisy) and I was very discouraged until the music stopped – it was the CD. Wow! You’ll hear things that have been hiding in your music. This can become the core of your home hifi system, a heaphone amp or even the ultimate iPod dock (puts that Bose dock to shame).

♦ Reviews and Expert Opinions

OK! I’m going to do this a bit slowly. Hopefully by the time someone is ready to actually warm up their soldering iron it will be done. My son and I are going to start on another one and we’ll take pictures of our progress. I’m sure that some of you are a bit skeptical. So I thought I’d throw out a few reviews from the audiophiles. The basic amplifier is made by a company called Sonic Impact and it’s called the T-Amp. There are now many versions of this amp in both kit form and ready-made. They have all been improved and tweaked, but they cost much more. It’s not unusual to see a modded T-Amp with a

New Case
New Potentiometer
New Connectors
Power Supply
A few Components Replaced

being sold for $500. Here are some of the reviews I’ve come across –

A Stereo Times review is HERE

A review from Audio Ideas is HERE

TNT Audio has an article HERE (translated from Italian)

Six Moons has a review HERE

Another article on some of the other Tripath Chip varients from TNT Audio is  HERE

These reviews should whet your appetite for my next installment – What the engineers and DIY modders have to say about the T-Amp. (Nerd Alert – Woop Woop Woop).

♦ Test Phase – TAMP Finds it’s Voice

Here is a picture from the most fun stage of the modification process – when you first hear the amp come to life! Everything is just temporarily connected. All of the difficult soldering has been completed and the new wires are hot glued down to the board for strain relief (more on this later). Still to be completed –

Mount everything in a new case
New connectors (speakers & input)
Permanently attach the new components
New Switch
New Potentiometer
Power Supply connection

The T-Amp is approximately the size of 2 AA batteries so look carefully (board is upside down)

TAMP test phase

♦ Basic TAMP Resources

The best source of tech information that I’ve found has been from the DIYAUDIO forums and some related sites. These guys have some serious DIY issues. They would buy 2 or 3 T-Amps and dissect them. The result is a complete schematic and recommendations on modifications that will noticeably improve your T-Amp. A word of caution – some of the threads are very long and full of flame wars. I’ve spent a month or so perusing these forums. There are many dangerous rabbit holes that will distract you – stay away from the Transmission Line speakers or anything to do with ¼ wave designs. You will likely never be seen again…….. (c8 If you want to build your own Power Supply, just build the ‘Snubberized’ design and ignore the flame wars. I have a really great Aston power supply (way over specc’d for the T-Amp) that I’m using. I have also tested a 3amp Radio Shack model with good results. Aston makes a very similar 3amp model to the Radio Shack and it’s the same price at GIGAPARTS.COM.

The T-Amp is fairly low powered (6watts into 8ohms) so you may want to consider using some higher efficiency speakers. I’ve been testing it using some Acoustech HT75s (BIC America Klipsch clones). They are rated at 96db/watt@1meter (high efficiency). Our next attempt will be on some lower efficiency speakers (~88db). The Acoustechs can make your ears bleed at half volume. I have no doubts that the T-Amp will have little problem with most any decent speakers.

The best modding resource that I’ve come across is in THIS THREAD on the DIYAUDIO forums. It’s very long, but full of good data. These guys are way over the edge and tend to want to replace every component. I looked at all of the mods with a cost-benefit approach. What modification will give me noticeable improvements with the least amount of work? The good news is that the point of diminishing returns is reached very quickly. For my T-Amp I decided to:

Purchase a good Linear Power Supply (cost is ~$29 for a Rolls Royce model)
Replace the Input Capacitors (fix the built-in bass roll off)
Supplement the PSU capacitor (helps with bass too)
Replace the Connectors (one of the biggest complaints)
Replace the Potentiometer (existing one is noisy and not well balanced)
Put the whole shebang in a nice case

The posts can be somewhat misleading – heading off in many different directions and often ending up in a dead end. Most of the mods involve simply soldering a new wire onto an existing component or solder point on the PCB. The hardest mods and the course that I chose involve removing two SMDs (teeny tiny surface mount devices) – the input caps. You can read about this mod and see pictures HERE (version 2). They are so tiny I needed a good magnifying glass to work on them. I replaced them with much larger Polypropylene Film mounted off the board (attached with wires), but you can also replace them on the board with some SMDs that are the correct value. The SMDs are mounted directly to very tiny trace pads on the PCB. This was the biggest challenge – remove the SMDs and attach wires in their place. The posts at DIYAUDIO are full of story of guys tearing off the pads or melting them into oblivion. Working slowly and carefully is the way to go. I would also consider a good soldering iron as a necessity. The new wires attached to the SMD pads need to be hot melt glued down to the PCB so they won’t pull the traces off. This may seem overly hard, but the alternatives are worse and involve rebuilding large parts of the circuit off the board. If you have any questions about why I decided to go the direction I did – please ask.

♦ Parts & Tools Needed

Soldering Iron – pencil tip (I use an industrial Weller like THIS)
Wire cutters
Wire Stripper
Small Screwdrivers
Solder – rosin core (I prefer the really fine gauge stuff like THIS
Hot Melt Glue gun
Third Hand or Project Vice (like a Panavise)
Desoldering Bulb or Braid
Magnifying Glass (I use an illuminated magnifying glass on an arm)
Drill and bits (regular bits and some step bits like THIS)
A large vise is also a good idea

30 gauge wire (two different colors needed) is HERE
(bigger is OK, but more difficult to work with)

Heat Shrink tubing like THIS

Temporary Speaker Hookup Wire (for testing)
(anything you may have laying around)

Permanent Speaker wire – whatever looks good to you!
Check out some of the choices HERE

Alligator Clip Connectors (for temporary hook-ups) like THESE

12v Power Supply
If you are going to build a PS, start now – you are on your own……(c8
Snubberized Power Supply plans are HERE and HERE

The Aston 12v 3amp power supply is HERE

Sonic Impact T-Amp
Google for places to purchase. Prices range from $19-$39
Check for availability first

Hammond Aluminum 1455 series case:
Hammond Enclosures are HERE
6″x4″x2″ black Mouser part number – 1455N1601BK
(any enclosure that looks good is fine – 2″x4″ end plate is minimum needed for all of those connectors)

Alps 50k RK27 Potentiometer (AKA Blue Velvet)
RK27112AS25C0A503 is available HERE

Speaker Binding Posts
Dayton BPP-G Premium Binding Post Gold (pair R&B – 2 needed) are HERE

RCA Connectors
Dayton RCA-CHRB RCA Chassis Mount Jack Gold (pair red/blk) are HERE

Banana Plugs (needed for Power supply and possibly speakers)
Dayton BASS-GRB Banana Plug Set-Screw Type (pair red/blk – get enough for speakers and power) are HERE
or Spade Connectors
Dayton SPCO-GRB Compression Spade Pair Red/Black are HERE
or Pin Connectors
Dayton Gold 12 GA. Pin Compression Connector Pair are HERE
(Depends on what your speakers need)

The connectors may seem overly fancy, but the end result will be a high quality amplifier. It just didn’t seem right to go cheap

Power Switch
(whatever looks good to you)
SPST Round Snap Mount Rocker w/ LED is HERE

Bushing for power cable
Strain Relief 1/2″ (20 pcs. black) is HERE

Volume Knob
Eagle Plastic Devices 450-6008 1.25″ Aluminum Knob is HERE
(or whatever looks good to you)

Input Capacitor
Solen 2.2uF-400VDC Polypropylene Capacitor (2 needed) are HERE
(must be mounted external to the T-Amp board – way too big)
or
You can try the Black Gate brand (mounted directly to T-Amp PCB)

Power Supply Reservoir Capacitor
Any Electrolytic over 1000uF and 16v or more
(I used a 4700uf 48v noname I had laying around)

PS – I forgot a few things………A short piece of shielded 2 conductor wire for the input connection (optional I guess)
Radio Shack SHIELDED INPUT CABLE

A piece of perfboad and some stand-offs to mount the T-Amp
Radio Shack PERFBOARD (enough for 2)
Radio Shack STANDOFFS

♦  Completed TAMP Pictures

We got our first T-AMP all packaged up today. Looks pretty sweet (it sounds even better).

We are building another one in the next week or so (Jr wants one real bad). I’ll take some pictures of the construction details. We’ll be using a 3amp Aston Power Supply that’s only a bit bigger than the T-AMP case (that ‘ol 12amp PS is way too big).

♦ Building a T-Amp

The first steps are necessary to remove the circuit board from the cheesy plastic case that it came it. There are six screws on the bottom of the case: four are under the rubber feet and two smaller ones are in the battery compartment.

Next pop off the ‘knob’ and there are 3 more screw that hold the small volume control sub-board. We don’t use any parts in this board. You can easily just unplug it and leave it in the case. I’d suggest removing it as it’s useful for testing the amplifier before any permanent mounting is done.

The main circuit board is held in place by two mushroomed standoff posts (plastic) and some hot melt glue. Cut, Grind or Drill off the mushroom heads and  pick off the glue. The board should simply pop off.

The speaker clips need to be removed from the case. We won’t be using them, but we’ll need them for easy testing. Use a pair of diagonal cutters and just cut the case to release them. First mark them so you can tell which is right and left later on.

The final attachments are the power leads from the battery compartment. You can break or cut away the plastic to release the terminal ends (only the outer two). If this seems like too much work, just cut the wires. Not much advantage in saving them.

I would suggest connecting everything up making sure it works at this point. Alligator clip leads are perfect for this job. Check the first picture I posted in this thread to see the ‘mess’ all connected and working. The audiophiles all recommend breaking in your amplifier for around fifty hours before judging it’s sound. They also have the same recommendations for new speakers. You will definitely notice a lot of bass roll off. Don’t despair improving this shortcoming is one of our main modification goals. Enjoy the music!

So far we have tested them on high efficiency speakers: the Acoustech HT-75s (94db) towers and some Klipsch RB25s (94db) bookshelf models. The Acoustechs are very sweet sounding. Hopefully the next one we build will use some lower efficiency speakers. The T-Amp only puts out 6 watts, but believe me this is way more than enough.

Now the hard work begins. We need to do some soldering, rewiring and the case end panels need to be drilled and cut. Let’s start with the circuit board modification. This is by far the most nerve wracking part. It’s also the easiest to screw up. Fear not – others more skilled than all of us have tried and failed miserably. You can console yourself that your investment is only $19 if things go wrong. Take it slowly and patiently. I’ve done two so far without problems. The second one was definitely much easier. It’s hard to describe how small the SMDs (surface mount device) are. The two extra dots after the period (normal 10pt type) in the picture below are the two capacitors we are replacing.

Here is a picture of one of these capacitors with the soldering iron tip nearby. I shot most of these pictures through a large illuminated magnifying glass. I also did all of the close work with the magnifier.

We are going to remove the capacitors labeled C3 and C4. One is on the top of the board and one is on the bottom. On the second amp we used 32 gauge wire wrap for the hookups. It was many times easier than the 24 gauge stranded stuff we used on the first one. Hopefully you have read through most of the material I presented earlier. I’d direct you back to Michael Mardis’ site. We are doing the version 2 modifications. He has some schematics and pictures that you may find useful. The long thread on DIY Audio also has some good  advice.

Here are the two capacitors we are interested in –

Here is the board after the removal of C3 and C4

Next we attach our hookup wires to the circuit board pads just vacated by the capacitors that we removed. I believe I read somewhere that the side closest to the chip is the positive side, but the Solen film capacitors we are using don’t have any polarity so don’t get too nervous about what colors you use. The solder traces are VERY delicate and will pull off of the circuit boards quite easily. After you finish soldering a pair put a blob of hot met on the wires to secure them to the board and provide some strain relief.

After your excellent soldering job, stop and hook up your amp again (alligator clips). See how much difference the new capacitors made. We need two more hookups on the circuit board for the new power supply reservoir capacitor that we are adding and for the LED in the switch. Fortunately we don’t need to remove anything difficult. We are just adding a larger electrolytic capacitor to the existing one. This is an electrolytic capacitor and the polarity matters. The caps are marked so pay attention to the exiting. Connect the new one in paralell, matching negative to negative etc. The existing reservoir capacitor is in the center of a group of 5 round components in the middle of the board. The hookups are attached on the bottom of the board right here –

We will simply cut off the existing LED leaving plenty of lead and solder our hookup wires to these. The polarity of the LED is important. The LED is mounted to bottom. Looking down from the top, the negative cathode (notched side) is on the left. Fortunately if you do it wrong, a simple switch of two wires will put things to rights.

The easy way to install everything in our Hammond case is to use a piece of perfboard that will slide into one of the slots on the case. We will attach our T-Amp board to the perfboard with some standoffs. We’ll mount the three new capacitors to the perfboard and solder everything up.

Everything should be working be working better than ever at this point. How about another test? We need to start on the case components now and it will be nice to have some music while we are working on the end plates. I cover the end plates with masking tape and layout the holes. Next we center punch all of the centers and drill pilot holes. The case is aluminum and working it is quite easy. I use stepped drill bits for the holes after measuring them with a caliper. The switch is tricky (use one size smaller than you think). Several parts require key slots to prevent them from spinning. Take your time – you want this part to look good! You can see the rough cuts for the speaker binding post notches here –

The switch I used also needed a key slot and the potentiometer needs a second smaller positioning hole. You’ll also need to cut the potentiometer shaft down for our knob. After you have cut and dry fit everything, install all of them and tighten them down (you’ll forget to do this later). We should make a short power supply lead (some of your deluxe speaker wire) and install it in the case end with a strain relief grommet.

We are now all done with the T-Amp volume control so we can cut this off and start to connect it to our components. The connections to this control are laid out like this –
(from Left to Right):
V + Ri Li G Lo Ro

V = switch 12volt out (red wire) to power switch
+ = switch 12volt in (red wire) to power switch
Li = from volume control to amp left channel
Ri = from volume control to amp right channel
G = ground
Ro = to volume from right channel (cut short – not used)
Lo = to volume from left channel (cut short – not used)

We are bypassing the T-Amp’s input connector (it shorts to ground when the plug is removed) and we won’t need the Ro and Lo lines (cut them shorter and don’t strip). You’ll need some two conductor wire with shield for our input signal from the RCA jacks to the potentiometer. This input wire needs to connect each end of the case so make it a bit longer than the case. Follow the schematic and work slowly. After the potentiometer is done, complete the power switch and the LED.

Next you need to remove the spring clips and output capacitors from the T-Amp’s speaker connectors. Attach the output wires to our new binding posts and then tack on the capacitors that we just salvaged. All that is left is the power connection. You’ll need to shrink wrap or tape this exposed joint. Put the case together (don’t forget the top) and you are all done.

My son and I completed this latest amp in around six hours – figure a few extra hours if you do it solo.

I found these Copper RAM heatsinks that fit the chip perfectly

♦ Power Supplies

A 12v wall wart will work better than AA batteries, but it’s probably still not enough especially if you are running on lower efficiency speakers. Power supply design has a major impact on audio quality. Many of the true believers use SLA batteries (sealed lead acid). I’ve been using a 3a 12v regulated bench supply, but have been working on a design of my own. I should have parts in a week or so and will report back on the build details. Here are the calculations I used for my power supply.

Square root of: (Power x 2) x load impedance = peak voltage, or in our case

Sq. Root of: (6 x 2)x8 = 11.4641V, or simply 11.5V peak.
To obtain a mean figure, we must divide our result with the sq. root of 2:
11.5 / 1.41 = 8Vrms.

Power-wise, what this means in practice in case of a true voltage source amplifier down to 4 Ohm loads, is outlined below:

6W/8 Ohms = 11.5 V peak / 1.44 Amperes peak
12W/4 Ohms = 11.5 V peak / 2.88 Amperes peak

What this means is that to drive 12watts into 4ohms you are going to need close to 3amps at 12v. If you only ever run it at 8ohms, 1.5amps is enough. You will notice the feeble power supply when you drive the system (she needs more power captain). Try it and see if your ears can hear a difference. I got a 3a 12v regulated supply at Radio Shack recently for $10 (closeout? New model is HERE – $41). I also have used a smallish Astron 3a model (RS-3A]) that was around $29. I’m sure that my T-Amp + Power Supply will need a bigger case, but I think that’s a price I’m willing to pay.

Designing and building your own power supplies is an art unto itself. You can chase down many rabbit holes on DIYAudio researching them. The model you linked to is a switching power supply. These are generally not viewed as high enough quality for audio reproduction (this is usually from the guys who only use Sealed Lead Acid batteries for their systems), but it will still work within limits. I think I remember that they are considered rather noisy(?) Another thing to keep in mind is that the manufacturer listed specs are often overly optimistic. In my own limited TAmp power supply research I remember calculating the requirements………

A true voltage source amplifier supplies (peak) 1.5 amps for 8 ohm outputs (at 6 watts) and 3 amps at 4 ohms (at 12 watts). Your DC power supply will need to at least match these figures. More capacity doesn’t matter (just more expensive), but less will be something you can hear.

I am lower than a novice on power supply design so do some research of your own. Be aware that these engineers can get very nasty…… (c8

That’s it, I hope you enjoy this project!

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