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
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
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.
I personally wouldn't risk running anymore voltage than 12v on a SI with addition Heatsinking or at least better airflow.
zBuff said: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.
sashmo said:
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.
sashmo said:
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.
zBuff said:
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.
zBuff said:
Agreed.
zBuff said:
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.......
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.
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.
Lostcause said: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/showthread.php?postid=567257#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.
sashmo said:
Send me a Private Mail by clicking on the "email" button below - and I'll give you Eric's contact details......
sashmo said:
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.
sashmo said:
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.........
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.
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.
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
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
sashmo said:
I'm trying to think of a safe way to get an email to you. I don't like posting email addresses on a public forum.
Yeah - I'm tempted to get a few more of the NAN40's myself.
Lostcause said:
You should be fine with LM317. It's rated up to 1.5A so it should be OK. The main reason I mentioned LM1085 was becuase it is "Low Dropout".......so it only needs an input voltage that is 1.5V above the desired output voltage. Sashmo could use one with his 13.5V supply to bring the voltage down to 12V. However, if you are using that 20V supply - then LM317 will do. It needs the input to be at least 3V above the output. Sashmo could use one with his older AC/DC converter (probably).
Lostcause said:
I would think that a large cap before the reg...and a smaller one after the reg would work well. It also depends how far things are away from each other. If the reg can be placed very close to the circuit it is feeding - and that circuit already has a power supply cap or decoupling cap - then you might not need to place a specific cap after the reg. However, if the reg is further away - like on another board - then a cap after the reg is required. This is where you end up with 2 caps between the reg and the device it is powering.
And....there is another cap.........that can be placed on the adjustment pin of an adjustable reg like LM317. This cap helps lower the noise of the reg and is normally in the order of 10-100uF.
Please not that I have not tried the following and it is only a suggestion. Proceed at your own risk.........
My initial feeling is that someting like this would be appropriate:
Power supply output (13.5V - 20V DC)........10,000uF cap........LM317 (set at 12V or 13.5V).......150uF cap...........DC input of T-amp PCB (with 330uf/470uf/560uf/680uf cap onboard).
The 150uF cap might need to be bigger.....but not bigger than the 10,000uF cap. It would be good to experiment with this value.
just a little update, I've removed the ground wire that was ontop the treble pot now. Removed some of the power links to the opamp that would have been a little parasitic on the power rail, haven't removed the ground lines to it yet though.
I would remove the blue LED is I could get rid of my DC offset.
Everything is just a little bit cleaner and sweeter now.
Does anyone think there would be any advantage is separating the power/digital ground and the analog ground?
Sorry still haven't got around to putting the schematic of the preamp portion into a computer yet, but I think I remember someone mentioning that a Tamp doesn't really gain much from a separate preamp stage, I don't think you'll be able to use the preamp on that board for anything like impedance matching anyway, I should have measured it for any DC offset before I distconnect the power to it.
I would remove the blue LED is I could get rid of my DC offset.
Everything is just a little bit cleaner and sweeter now.
Does anyone think there would be any advantage is separating the power/digital ground and the analog ground?
Sorry still haven't got around to putting the schematic of the preamp portion into a computer yet, but I think I remember someone mentioning that a Tamp doesn't really gain much from a separate preamp stage, I don't think you'll be able to use the preamp on that board for anything like impedance matching anyway, I should have measured it for any DC offset before I distconnect the power to it.
Hi all, I was working on a Lepai yesterday - it's not all that easy to mod. Some tight spots in there near the chip board.
Anyhow, the signal flow is basically like this:
RCA -- Volume Pot -- DC blocking caps (says 3.3uF on PCB, nice were 10uF) -- Opamp (gain 6dB) -- blocking caps --- tone section --- blocking caps --- sub board -- chip.
I think that's it.
The input signal connects to the chip board right at one end. I cut the traces there. You could use that as a new input point, if you wanted to. Will post a photos here in a minute.
I had a 1st planned to use the opamp as an active low pass filter, as this is going to be a bass amp. Then for various practical reasons I decided to keep the LP filter in another box.
Sooo... I replaced the cheap 10uF caps that come after the pot with some nice Panasonic FC 3.3uF that came from an AMP6. From there I jumped to the edge of the chip board. Now my signal flow is: RCA -- pot -- blocking caps -- chip board. A much reduced signal path.
I know this is almost impossible to follow without photos and arrows, but I will post those ASAP.
Also replaced was the power stiffener cap. The stock was a 2200uF 25V of dubious quality. It's rather small for its value - not a good sign. I squeezed a big Panasonic 2200uF 25V in. That's my trademark cap, the Panny FM.
Also replaced the two little electrolytics on the chip board with 1200uF pannies. A very tight fit.
So now it's a Super Lepai. It will be renamed "Cafe de laPaix." If it were for full range use, I would use film caps on the inputs, not the 3.3uF electrolytics that I did. Soon I may swap them out. Just wanted to get it up and running, you know?
Anyhow, the signal flow is basically like this:
RCA -- Volume Pot -- DC blocking caps (says 3.3uF on PCB, nice were 10uF) -- Opamp (gain 6dB) -- blocking caps --- tone section --- blocking caps --- sub board -- chip.
I think that's it.
The input signal connects to the chip board right at one end. I cut the traces there. You could use that as a new input point, if you wanted to. Will post a photos here in a minute.
I had a 1st planned to use the opamp as an active low pass filter, as this is going to be a bass amp. Then for various practical reasons I decided to keep the LP filter in another box.
Sooo... I replaced the cheap 10uF caps that come after the pot with some nice Panasonic FC 3.3uF that came from an AMP6. From there I jumped to the edge of the chip board. Now my signal flow is: RCA -- pot -- blocking caps -- chip board. A much reduced signal path.
I know this is almost impossible to follow without photos and arrows, but I will post those ASAP.
Also replaced was the power stiffener cap. The stock was a 2200uF 25V of dubious quality. It's rather small for its value - not a good sign. I squeezed a big Panasonic 2200uF 25V in. That's my trademark cap, the Panny FM.
Also replaced the two little electrolytics on the chip board with 1200uF pannies. A very tight fit.
So now it's a Super Lepai. It will be renamed "Cafe de laPaix." If it were for full range use, I would use film caps on the inputs, not the 3.3uF electrolytics that I did. Soon I may swap them out. Just wanted to get it up and running, you know?
I was wrong to remove the earth wire from the board to the top of the treble pot. Removing will cause hum when you touch the case or the volume pots with your hand.
I did something stupid, I tried pulling up one of the legs of the resistor to the blue LED, I must have had it shorted against something because when I turned the amp on there was spark and a little smoke. Now my amp is dead, the red LED just blinks. I think I might have fried the chip.
Should have double checked everything before turning it back on.
I did something stupid, I tried pulling up one of the legs of the resistor to the blue LED, I must have had it shorted against something because when I turned the amp on there was spark and a little smoke. Now my amp is dead, the red LED just blinks. I think I might have fried the chip.
Should have double checked everything before turning it back on.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.