Lepai T-Amp with TA2020

[sashmo]

Thanks,
I'm glad to have found this site. I've had my SI for over a year now and have been powering with a AC/DC converter.
Output 17VDC Max0A
13VDC Min 1.3A
I presume that this means I'm getting about 13V so would you recommend I keep using this?
My only "mods" have been the usual new box, real speaker terminals, on/off switch, separate volume pot. and the only way I was able to do it was by an instructional complete w/ diagrams.
Luckily for me and those like me, there is a wealth of info and ideas provided by people like yourselves.

Thanks again

[zBuff]

The new SMPS you got most likely will be better, I'm not sure about that specific one, but most of them you can change the output voltage by a trimpot on the board. so you should be able to dial the voltage down to 12V. I'm sure Fin will be able to help you out in that regard.

I personally wouldn't risk running anymore voltage than 12v on a SI with addition Heatsinking or at least better airflow.

[Fin]

Originally posted by zBuff
Could someone else test their Lepai and tell me if they're getting any DC offset as well? I've been trying to get rid of it recently I noticed that the Blue LED is fed off the speaker outputs of the left channel, I thought THAT's it, removed the LED and my DC offset actually increased from 150mv to 170mv

It will be the weekend before I can test mine.....my multi-meter is elsewhere at the moment.

Originally posted by sashmo
Thanks,
I'm glad to have found this site. I've had my SI for over a year now and have been powering with a AC/DC converter.
Output 17VDC Max0A
13VDC Min 1.3A
I presume that this means I'm getting about 13V so would you recommend I keep using this?

That sounds like your old power supply (AC/DC converter) is not regulated. With no load (no current being drawn) the voltage will be 17V. The more current that you draw from the supply, the lower the voltage drops - until you draw the maximum current of 1.3A.....at which point the voltage will be 13V. I would think that you S.I. was probably seeing a voltage considerably higher than 13V.

You new supply is regulated and would therefore be a bit safer even though its voltage is a bit high for the S.I. At least it won't be drifting upwards towards that 17V when it is not using much current.

I've read about some people using their S.I. with voltages up to the absolute max of 16V......but there is little information about the long term effects of this. I certainly wouln't suggest going anywhere near as high as that. Some are using theirs at 13.8V because there are many supplies available with this output. However, like zBuff, I'm comfortable with mine at 12V.

You could always build a regulator and set it at 12V.....and add some additional filtering. Then you could choose whichever supply you would like to use.

Originally posted by sashmo
My only "mods" have been the usual new box, real speaker terminals, on/off switch, separate volume pot. and the only way I was able to do it was by an instructional complete w/ diagrams.
Luckily for me and those like me, there is a wealth of info and ideas provided by people like yourselves.

Have a look at replacing the input capacitors. Michael Mardis has a nice "Stealth Mod". You might find that this boosts the appearant power of the amp by improving the bass response - and reduces your need to squeeze more power by increasing the voltage.

Originally posted by zBuff
The new SMPS you got most likely will be better, I'm not sure about that specific one, but most of them you can change the output voltage by a trimpot on the board. so you should be able to dial the voltage down to 12V. I'm sure Fin will be able to help you out in that regard.

I haven't looked at it yet - but it should be possible.....or just add a low drop out reg and some extra filtering. Should make a nice, clean supply.

Originally posted by zBuff
I personally wouldn't risk running anymore voltage than 12v on a SI with addition Heatsinking or at least better airflow.

Agreed.

[zBuff]

Originally Posted by myself

I personally wouldn't risk running anymore voltage than 12v on a SI without additional Heatsinking or at least better airflow.

sorry errors, gave quite the wrong message before.

[Fin]

Originally posted by zBuff
sorry errors, gave quite the wrong message before.

Nah....I thought your advice was clear and appropriate.....and I agree. It is consistant with everything else I have read and also what Pano himself recommends.

Maybe Sashmo should grab one of these little Lepai amps.....would be perfect with that 13.5V SMPS......and we would have another member in our exclusive little club.......

[Lostcause]

Hey Fin...

just add a low drop out reg and some extra filtering. Should make a nice, clean supply.

I have a really nice 20V SMPS, small with high quality components and was thinking about this....Got any more direction on this one?
I may be OK at the practical stuff but not this

[sashmo]

Sashmo would love to get his grimy little hands on a Lepai...if you could tell me how.

No. 1 son has been using the SI with the AC/DC converter using an 87dB (I think) pair of home made Accusound speakers (no plug but they are remarkably good) on his PC and they have not even got warm yet.

I do take your point about the long term outlook though....they may be cheap BUT.... really what I am trying to do here is to gain a LITTLE bit of know how on the way to finding out about using D class as THE way to a realistic replacement of my present (beautiful) vintage setup.

I don't know if this is even a possibility at this stage but it certainly looks like I have struck the right place to find out.

[Fin]

Originally posted by Lostcause
Hey Fin...

I have a really nice 20V SMPS, small with high quality components and was thinking about this....Got any more direction on this one?
I may be OK at the practical stuff but not this

Thsi is where it gets even easier (and maybe more fun) than modding an existing item........

Go to the National Semiconductor site and download the datasheet for LM1085. It is a 3A voltage regulator and comes in a variety of pre-set voltages (including 12V) and an adjustable version if you want to set 13V, 13.2, 13.5...or whatever. There is also LM1084 which is a 5A version - I think.

You then need to go to you local electronics store and buy one (a couple of bucks). Make sure you get the TO220 3 pin package...easiest to work with. You can also get a little heatsink for it. Connect it up on a small piece of board....with your choice of caps before and after.....but don't go overboard with the caps after the reg as you might run into trouble when you switch off and things want to start flowing backwards. Basically - follow the suggestions in the datasheet.

Plug in your power supply and test the output voltage. It should be rock steady on whtever value you have chosen.

For more details on this and some ideas on various setups with recommended capacitor values - do some searches on LM1084/5/6 and on LM317 (similar, but not low dropout and only 1.5A). There will be lots of information on LM317 as it is very popular for use in CD players and pre-amps but I think a higher rated unit would be better just in case.

This is the type of thing that Motherone is doing here:
http://www.diyaudio.com/forums/showt...257#post567257
He mentions diodes - but you only need to consider those if your supply output is AC. Being a SMPS it should already be DC and regulated. Another stage of regulation down to 12V or 13.5V (depending on which amp you will be using it with) will be a good thing.

Just a thought....you could build two outputs from that supply. One at 12V for your S.I. and another at 13.5V for your Lepai. If it is unlikely that you would ever want to use both amps together - then you could just have one output with a switch to alter the resistor that adjusts the voltage.

Originally posted by sashmo
Sashmo would love to get his grimy little hands on a Lepai...if you could tell me how.

Send me a Private Mail by clicking on the "email" button below - and I'll give you Eric's contact details......

Originally posted by sashmo
No. 1 son has been using the SI with the AC/DC converter using an 87dB (I think) pair of home made Accusound speakers (no plug but they are remarkably good) on his PC and they have not even got warm yet.

I was using mine with a small pair of 87db/w speakers and the volume level was adequate for me. Now I've changed to a pair of slightly larger and more sensitive 93db/w speakers. The difference in quite noticeable. Also, unless your PC has a very good sound card, you won't be hearing the full potential of this amp. I've noticed significant differences by swapping a variety of quality CD players.

Originally posted by sashmo
I do take your point about the long term outlook though....they may be cheap BUT.... really what I am trying to do here is to gain a LITTLE bit of know how on the way to finding out about using D class as THE way to a realistic replacement of my present (beautiful) vintage setup.

I don't know if this is even a possibility at this stage but it certainly looks like I have struck the right place to find out.

Try building a regulated supply for it using either of your converters/supplies - and the regulator described above. Maybe use your old converter with the regulator - for the SI.....and the NAN40 with a Lepai (if you decide to get one). Whatever way you go, it will be good for your SI and teach you how to do it for the more elaborate models when the time is right.........

[sashmo]

I tried sending you an email but as I'm still under moderation I'm not able to. I do want a Lepai so could you email me the details?
I don't imagine the moderation thing is 2 way.
BTW I've just ordered 6 more NAN40s, 1 for me and 5 for a tech friend who is quite impressed with them.
I appreciate your taking the time and offering advice.

[Lostcause]

Hey Fin, thanks for the reply...
LM108's......The words 'rocking horse' and 'rare' spring to mind!
They do look good though!
I have found similar spec'ed regs but none at the corner shop that's for sure.
Looks like the good old LM317 for me! or wait until I've got a nice shopping list before doing an on-line order.
It's those caps that confuse me as well...some say no cap after the reg...some say two...some say...whatever!
I think it's going to be a switchable input as well, so I can do a quick A/B on the effect of more power...

TTFN