DIY Pre-amp with MP3 Player (and FM Tuner)

[activexp]

I wanted a Pre-amp to go with my TA2024 chipamp and after seeing the products on offer from various Chinese eBayers I rather fancied having a go at building my own.

The USB MP3 Player and PSU came from Helder HiFi. Both were well packed in cardboard boxes and were delivered in about 2 weeks.

http://a8.sphotos.ak.fbcdn.net/hphotos-ak-ash4/374787_10150531866944832_528289831_11439565_122647 7631_n.jpg



http://a2.sphotos.ak.fbcdn.net/hphotos-ak-ash4/391764_10150531866909832_528289831_11439564_104267 2895_n.jpg

Adjustable 11- 14V @ 3.5A Switched Mode PSU




The Pre-amp module from Zoe Tsang which came bubble wrapped inside an unpadded buff envelope. Although seemingly inadequate, no damage done. Delivery took about 10 days.

http://a6.sphotos.ak.fbcdn.net/hphotos-ak-ash4/375854_10150531867064832_528289831_11439566_151619 112_n.jpg

Four inputs, volume, balance, bass, middle, treble and 3D. The board I received differed slightly from the one shown. The control pot on a separate board with a ribbon lead has been replaced with one integrated on to an extension of the display board. This made mounting the assembly much more tricky.

http://a4.sphotos.ak.fbcdn.net/hphotos-ak-ash4/s720x720/375591_10150531867144832_528289831_11439567_853191 504_n.jpg

The metal case came from CPC.

http://a3.sphotos.ak.fbcdn.net/hphotos-ak-ash4/s720x720/377826_10150531866884832_528289831_11439563_325124 804_n.jpg

During assembly I noticed that the MP3 module had an 'aerial' symbol on the board. Out of curiosity I connected a piece of wire to the marked hole on the PCB and was quite surprised to hear Radio2 coming through loud and clear. The product description does not mention an FM Tuner. Bonus.

It all works pretty well apart from a problem with the remote controls - they both operate on the same frequency! However the pre-amp remote revealed two more undocumented features of the MP3 module - FM station memory (not sure how many, on autoscan it stored 25 but only about 10 are listenable using a piece of wire as an aerial) and 6 sound 'equalizer' settings ranging from bassy to toppy with something inbetween. Now I can't decide which one gives a 'flat' response :doh:

As for the pre-amp module, no surprises although I haven't discovered how to alter the brightness of the display which apparently can be done using the remote.

All in all I enjoyed this little project but doubt I'll ever master cutting accurate openings in sheet metal.

Cheers,
Steve

[Reid Malenfant]

Neat little project Steve :) What you need to do is cut the hole too small & then file it out to the correct size ;)



The Pre-amp module from Zoe Tsang which came bubble wrapped inside an unpadded buff envelope. Although seemingly inadequate, no damage done. Delivery took about 10 days.
Just received 12 x 250W class D amps from Zoe Tsang myself this very day! Shipped on Monday via DHL, I really didn't fancy taking any chances with that sort of money.

Had to laugh as the form on the front said value was $20, which is true if taken individually :lol:


Keep up the DIY Steve, it's all good fun :cool:

[StanleyB]

It is a very commendable effort :). We need more of that sort of thing on AoS.

[activexp]

Neat little project Steve :) What you need to do is cut the hole too small & then file it out to the correct size ;)



Just received 12 x 250W class D amps from Zoe Tsang myself this very day! Shipped on Monday via DHL, I really didn't fancy taking any chances with that sort of money.

Had to laugh as the form on the front said value was $20, which is true if taken individually :lol:


Keep up the DIY Steve, it's all good fun :cool:

There's so much tempting stuff from the Chinese Ebayers. I did contemplate getting a T-amp and the pre-amp in kit form but if for any reason it doesn't work you're stuffed.
The customs label on the package from Helder said 'Electronic components no commercial value', and from Zoe Tsang 'Sample, Value $0'. :)

What have you in mind with 12 class D amps? Sounds like a big project!

[Reid Malenfant]

What have you in mind with 12 class D amps? Sounds like a big project!
Fair size project yes ;) Six low dissipation class A power amplifiers, you can take a look here if you like (http://theartofsound.net/forum/showthread.php?t=8780), though there isn't much happening right now other than modification of the class D amps I just received :)

Once they are tried & tested then it'll be time to design the class A sections :cool:

[activexp]

Fair size project yes ;) Six low dissipation class A power amplifiers, you can take a look here if you like (http://theartofsound.net/forum/showthread.php?t=8780), though there isn't much happening right now other than modification of the class D amps I just received :)

Once they are tried & tested then it'll be time to design the class A sections :cool:

Hi Mark, all very cool! Despite my reservations about building kits, you've whetted my appetite in having a go at TA2022 board from zoe_tsang. It's this one:

http://www.ebay.co.uk/itm/TA2022-50-150W-Can-BTL-amplifier-Kit-SC-/200618748754?pt=UK_AudioTVElectronics_HomeAudioHiF i_Amplifiers&hash=item2eb5cf2b52#ht_10307wt_906


http://farm4.static.flickr.com/3069/5706438146_9081ef8221_o.jpg


It's reasonably cheap so if it goes up in a puff of smoke it's no great loss! I'd only use it in stereo, the BTL mode isn't required for my purposes.

One thing I need some advice on is a suitable transformer :scratch: I assume I need at least 200VA. The recommended 24V seems hard to come by as does 22V and 20V so it looks like I'll have to settle for 18V.

Your comments would be welcome. Incidentally, the designer of the board and of your L20D IRS2092 posts on DIYAudio forum as ljm_ljm.

Regards,
Steve

[Reid Malenfant]

One thing I need some advice on is a suitable transformer :scratch: I assume I need at least 200VA. The recommended 24V seems hard to come by as does 22V and 20V so it looks like I'll have to settle for 18V.

Your comments would be welcome. Incidentally, the designer of the board and of your L20D IRS2092 posts on DIYAudio forum as ljm_ljm.

Regards,
Steve
Hi Steve, just take your time with it & I feel sure you'll have no problems ;) There are no surface mount components so it should be a walk in the park. I remember the first L15D pair of amps I bought as a kit from the same seller on ebay (yet again) & the IRS2092 needed soldering onto the PCB. Not easy but i managed both with no faults ;)

I'll see what I can find for you transformer wise, so keep an eye out for a PM & I suggest you do so fairly regularly as some may be auctions on a well know site :eyebrows:

Cheers for the info about the amp designer. Think I'll take a look :cool:

[activexp]

Hi Mark, thanks for the PM regarding a suitable transformer for the TA2022 board. Do you think I can get away with 25V? I asked zoe_tsang and the response was basically no, 24V or less is better.

If that's the case then my best option appears to be 18V, this one:

http://cpc.farnell.com/multicomp/mcta225-18/transformer-225va-2x-18v/dp/FF01585

Any good?

Cheers,
Steve

[Reid Malenfant]

Hi Steve, yes that transformer would do the job ;)

However, you could use the 25V transformer as long as you put a couple of high current diodes (5A would do) in both the transformer lines (but not the ground. Two in series in each line & another two again in series but connected in parallel with the others but reversed would drop 1.4V & give you a 23.6V AC output.

You'd need 8 diodes in total. If you need a circuit to show you what I'm on about I'll get something together for you :)

I'll do some checking on the IC & see what it's maximum ratings are ;) Once I find out I'll get back to you...


Ok I have taken a look at the spec of the TA2022 chip. There seems to be no reason why it cannot be run on a 25V transformer. The absolute maximum voltage rating is +/- 40V DC, but the recommended operating conditions are a maximum of +/- 36V DC..

5662

Given your transformer is 25V AC you need to multiply this by 1.414 & then subtract 0.7V allowing for one diode drop to reveal the DC voltage on the rail... Or if you like +/- 34.65V DC...

The chip will not have a problem, it may well be that some of the electrolytic capacitors are only rated at 35V DC though, which is cutting it close. Ok so they do tend to have a surge voltage, but there is no point pushing things ;)

You need to check the capacitors when your kit arrives :cool:

[Reid Malenfant]

Steve, I have just had a thought :lol: Can you link me to this 25V transformer? I have just been thinking about transformer regulation. On a low load you'll get more than 25V AC out of it, it should be designed to give 25V AC on full load. We'd need to see how much regulation the transformer has, but in all honesty it's making things worse :rolleyes:

E2A:- If you eventually decide to go for an 18 0 18V transformer then give me a shout as I have a toroid here that I could do you cheap, don't think I'll ever use it in reality.

[Reid Malenfant]

24 0 24 200VA transformer (http://www.ebay.co.uk/itm/NEW-Transformer-200VA-230V-PRI-48V-24-0-24V-SEC-/350472811803?pt=UK_BOI_Electrical_Components_Suppl ies_ET&hash=item5199ceb51b) ;)

This below should be the best deal buy a long chalk :)

225VA 24 0 24 transformer. (http://www.airlinktransformers.com/chassis_mounting_toroidal_transformers_standard_ra nge/3-CM0225224.html)

Please remember that the last one needs VAT adding & it also needs shipping adding. But that would be the one I went for :cool:

[activexp]

Here's the 25V one:

http://cpc.farnell.com/multicomp/mcta225-25/transformer-225va-2x-25v/dp/FF01586

Power Rating: 225VA
Secondary Current Nom: 4.5A
Secondary Voltages: 2 x 25V
Transformer Mounting: Chassis
AC Power: 225VA
Approval Bodies: UL Recognised
Bolt Length: 60mm
Bolt Size Max: 6
Current Rating: 4.5A
External Diameter: 110mm
External Length / Height: 51mm
Mounting Type: Chassis
Output Voltage: 25V
Primary Voltages: 115V / 230V
Regulation: 7%
Secondary Power: 112.5VA
Temperature Rise: 56��C
Transformer Type: Toroidal
Weight: 2.2kg
Weight: 2.2kg

Looking at the data sheet for the 2022 it appears that some resistor values need to be calculated depending on the chosen supply voltage and refers to the under and over voltage protection. The formulas are all a bit over my head :scratch: Looks like ljm decided to play safe with a max of 24V.

I'm all for keeping things simple so rather than attempting to swap components for 30V operation (the resistor values look a bit odd like 242K 1%) I reckon my best bet is 18V. That said I'm very interested in the transformer you have available!

What are the specs and diameter (i.e. will it fit my case) ;)

Cheers,
Steve

[Reid Malenfant]

I'll give it a measure tomorrow Steve, it's a low profile toroidal on a PCB that has been wired in series. You may as well have the lot if taking it as there is an IEC mains chassis socket that you may be able to use on this project.

[activexp]

Hi Mark, that Airlink one looks the business and even with VAT and delivery the price is OK :) Your Google must be better than mine. Thanks for the link!

I'm still at the planning stage, sourcing all the bits so I haven't ordered anything yet. Hopefully the amp will fit in the same case as the pre-amp for a matching pair. Still undecided about a heat sink for the 2022 as I can't find any specifically for Tripath chips. The alternative is to use the back panel of the case, a cost effective solution ;)

Cheers,
Steve

[Reid Malenfant]

I might be able to help you out with a heatsink, I have them coming out of my ears :eyebrows:

Yes I'd go for the Airlink transformer, even over my 18V jobby!

I'll get back to you tomorrow anyway Steve as I'm just about to fire up the PJ & have a film :)

All the best :cool:

[activexp]

Board ordered from Zoe_Tsang, with any luck I'll get it before Christmas and give me something to do over the holiday ;)

For the transformer I'm going for the 300VA one as it's not much more.

Any joy with the heatsink Mark?

Cheers,
Steve

[Reid Malenfant]

For the transformer I'm going for the 300VA one as it's not much more.

Any joy with the heatsink Mark?

Cheers,
Steve
Good choice on the trafo ;)

Glad you reminded me about the heatsink :eyebrows:

If I don't get back to you by next weekend send me a PM or put another reply on here ;) I'm just trying to think what I have got that'd be suitable, in reality it doesn't need to be very big, but bigger = cooler & greater efficiency as well as the thing will last longer :)

You'll need to insulate the chip from the heatsink if it's attached to the chassis, I have stuff that'll cover that to so need to find it :cool:

[activexp]

Thanks Mark. The heat sink doesn't have to be particularly large. I've seen this one on eBay:

http://i.ebayimg.com/00/s/NDAwWDQwMA==/$%28KGrHqQOKi4E6fG-,jd2BOtokEhPh%21~~60_12.JPG

Should do the job :) If you've got anything similar PM me.

It won't be attached to the chassis so insulation isn't needed :)

Cheers,
Steve

[Reid Malenfant]

Hi Steve, you just reminded me & I think I have just the thing ;) I'll have a dig in the shed tomorrow for a dead NAD CD player that has a similar heatsink on the back panel. Better still I'm sure it's anodised black :)

[Reid Malenfant]

Steve, please send me a PM & let me know your address ;)

I have a nice black anodised heatsink for you that will be perfect for the job in hand :)

[activexp]

Hi Mark, I've now got the Airlink transformer and a hefty beast it is too! The secondary windings are black-red and orange-yellow. I assume that for dual rail I join the yellow and black together for the 0V centre tap?

You can tell I'm a noob to this scratch building lark :mental: !

Cheers,
Steve

[Reid Malenfant]

Did you get any kind of wiring diagram with it? Only asking simply because it's easy to get the starts & finishes of the windings mixed up. The result would be zero volts output or miniscule :eyebrows:

Yes you'll need to join two wires together & that point will be zero volts, which ones I don't know. If you have a diagram them good, if not you'll need to test it with an AC voltmeter to establish the right ones ;)

[activexp]

No wiring diagram, only a label:

Input 0 - 230V Blue-Brown
1st sec Black-Red
2nd sec Orange-Yellow

Logic suggests that 24V is on Red and Orange with the 0V centre tap on Black and Yellow. But equally the centre tap could be Black and Orange :scratch: Guess I could e-mail Airlink for clarification.

[Reid Malenfant]

If you have an AC voltmeter connect the Black & Yellow leads together & measure the voltage at the Red & Orange leads. Assuming it's a 24V transformer you should read around 48V AC.

You won't mess it up if the leads are wrong, just don't short any of the other secondary wires together. If you happen to read zero or near zero volts then simply swap over one secondary lead so that Orange connects to the Black & re-measure.

Make sure you have some kind of fuse on the mains side. A 3Amp fuse in a plug should be ok for testing purposes.

If you are unsure then ask & don't go electrocuting yourself please ;)

[activexp]

Thanks for the advice Mark. I'll see if I get any response from Airlink before risking electrocution :eek:

[Reid Malenfant]

Hi Steve, I have a question for you :) How much was the shipping on that 300VA transformer? The amount of times I have looked on the Airlink site & I have never seen shipping costs mentioned :doh:

[activexp]

Hi Mark, it was £7.50 (plus VAT). I've had a reply from them regarding the wiring which pointed me to a link for technical information complete with a diagram. I feel slightly embarrassed not to have spotted this! :doh:

So no danger of electrocution this time. My assumption that yellow/black was 0V is correct :)

[activexp]

Noticed a problem with the pre-amp, noise in the form of buzz mainly from the mid range unit. I know it's the pre-amp as the noise disappears when it's switched off or disconnected from the power amp.

I'm sure it's the switch mode power supply that's the cause so I might replace it with a linear. Hopefully that will fix it. :)

[activexp]

Added a TA2024 amp board at a cost of 8 quid including delivery from Arjen Helder.

It actually sounds quite good, no buzz or hiss. Surprisingly punchy and dynamic for such a tiny amp. Running at 13V from a regulated linear PSU.

https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-prn1/s720x720/560461_10150903178684832_528289831_12748181_147291 1778_n.jpg


https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-ash3/s720x720/523841_10150903178924832_528289831_12748182_654661 751_n.jpg

https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-ash3/s720x720/558469_10150903179159832_528289831_12748183_890464 493_n.jpg