Hybrid DIY cct of LM3886+6N11

[Pemo]

I agree

Hi Pemo.
When it's loud (like, 75/80wpch), there is some compression, but if I had a regulated 30/0/30Vdc PSU @ 10A, or even 35/0/35 @ 10A, instead of a Tx on the end of the supply chain then I'd be a lot more satisfied.
You just CAN'T HAVE too much power supply...

I agree with you, there is not such a thing as "TOO MUCH POWER".
I'm planning on using this board stock, with a 24-0-24 transformer, and I was wondering (because I don´t have much information on this board, schematics or anything) if the PSU in this board is enough. In other projects with LM3886 I´ve used 40,000 mF (4 caps) and liked it very much.

RGDS

PEMO

 

[copperweed]

Sometimes, if the output stage has gone short-circuit, it can sound like it's oscillating at 50 or 60 Hz. The power has been transformered, rectified and smoothed, but then, if the smoothing caps are shorted to ground through the speakers, it can sound like a full-power oscillation. I need to know aprox frequency to be sure. Whistling or whining could be osc., but loud buzzing could be a blown chip.

Sorry, just re-read ur post. What I said was true, but not in ur case, I think, because you don't mention any frightening or mysterious noises.

What is your supply voltage? Every 5v extra on the PSU adds nearly 30% to the amplifier cct's dissipation, from +/- 20 to +/-25 to +/-30. And there are four amplifiers on your board!

I know you're confident in your heatsink, but I'd still be tempted to double it or add a fan.
cw

 

[copperweed]

I agree with you, there is not such a thing as "TOO MUCH POWER".
I'm planning on using this board stock, with a 24-0-24 transformer, and I was wondering (because I don´t have much information on this board, schematics or anything) if the PSU in this board is enough. In other projects with LM3886 I´ve used 40,000 mF (4 caps) and liked it very much.

RGDS

PEMO

This is what I'm thinking...

 

[pinnocchio]

Sometimes, if the output stage has gone short-circuit, it can sound like it's oscillating at 50 or 60 Hz. The power has been transformered, rectified and smoothed, but then, if the smoothing caps are shorted to ground through the speakers, it can sound like a full-power oscillation. I need to know aprox frequency to be sure. Whistling or whining could be osc., but loud buzzing could be a blown chip.

Actually it sounds fantastic with no issue whatsoever in the sound but the chips becomes hot extremely fast. 70-80C in 1-2min... And this even at moderate levels... With my other LM4780 amp they never really get that hot... What's the max safe temp I should be seeing on the top surface of the chip?

This is the reason I thought it was oscillating.

Thanks
Do

 

[copperweed]

Actually it sounds fantastic with no issue whatsoever in the sound but the chips becomes hot extremely fast. 70-80C in 1-2min... And this even at moderate levels... With my other LM4780 amp they never really get that hot... What's the max safe temp I should be seeing on the top surface of the chip?

This is the reason I thought it was oscillating.

Thanks
Do

OK, doesn't seem like any power-draining parasitic osc I ever heard of. And if it were RF, the output RC network would be BAKING at that sort of power.
I ask again, what is the at-rest supply voltage?
And also, is there more than 0.1V dc at the speakers, also in at-rest condition?
And, are you running those dual-amp chips in single,parrallel or bridge?
U kno, they are pretty bomb proof!!!
SC, under-volts, over-volts, max 250 C internal, dynamic SOAR; u gotta ask, "do they actually NEED a heat-sink?"... but I say just make it bigger. Like PSUs, u can't have a good-enough heat-sink...

 

[kallel123]

schematics here for lm3886 6n11

An externally hosted image should be here but it was not working when we last tested it.

 

[kallel123]

risistor replacer

here are some pics i did this for my daughter. she loves the sound. it is quite good no hum dead silent.all

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

i need to do now is replace the input with a newly developed LDR based mod... link= Build An Amp i cleaned up the wireing since then its been going strong for about six months now without a hiccup

An externally hosted image should be here but it was not working when we last tested it.

 

[kallel123]

speakers

p.s it took me a while to find some deacent speakers for the lm3886+6n11 .i was on a painting job in london i complimented the owner on them and he said he was tossing them out. you like them you can have them. nice bonus they sound out standing.i also added a buffer stage . it has one 12ax7 and one 12au7 which ive rolled a little bit to see witch ones complimented the speakers best for my set up. long plate square getters worked out perfect! i think when im done my surround sound set up im going to buil another one exectlly the same i also notice a few caps could be upgraded to 105c there just cheap caps but the the uprade is more for longevity i didnt notice a difference with expensive caps at all .i also swapped out the 6n11 for a 6922 even sweeter sound .hope this all helps best regards

 

[copperweed]

p.s it took me a while to find some deacent speakers for the lm3886+6n11 .i was on a painting job in london i complimented the owner on them and he said he was tossing them out. you like them you can have them. nice bonus they sound out standing.i also added a buffer stage . it has one 12ax7 and one 12au7 which ive rolled a little bit to see witch ones complimented the speakers best for my set up. long plate square getters worked out perfect! i think when im done my surround sound set up im going to buil another one exectlly the same i also notice a few caps could be upgraded to 105c there just cheap caps but the the uprade is more for longevity i didnt notice a difference with expensive caps at all .i also swapped out the 6n11 for a 6922 even sweeter sound .hope this all helps best regards

Wow, fantastic job. And thanks for the 6n11/6922 tip. I'll search out some NOS. And did u have to mod the SP Rx cct like I did? see here; http://www.diyaudio.com/forums/solid-state/208506-hybrid-diy-cct-lm3886-6n11.html

 

[kallel123]

Thanks for the compliment. no i left every thing as is except 2 caps and if you want a beefier supply, why not piggy back some more caps you can add as many *** you like>id be careful with higher voltage trafos these caps are only 50 volts! im running mine at 22-0-22 so i can run 4ohm speakers or 8 ohms nothing gets to hot if went to 30 volts ac i would change at the very least the big cans 80v 100v they should run nice and cool.. im trying a point to point lm3886 next based on elliot but then i seen this powerhouse http://i47.tinypic.com/11kjxg9.jpg[/IMGDEAD]]Photobucket | The most recent pictures on Photobucket

 

[kallel123]

oops wrong link

 

[copperweed]

I've bought another board. Bi-amping, here we come...

 

[copperweed]

Hiya
Long time no post.
Finally got that 35vDC Fully Regulated supply built for my 4ch 6n11/3886 gainclone built (pics to follow).
YES, THESE BOARDS CAN HANDLE A REGULATED 35V DC POWER SUPPLY.
And they sound gorgeous.
No-one can tell on mine if the volume is set to MAX or MIN.
I've got two of the afore mentioned 6N11/3886 boards in a full dual mono-block implementation with a derivation of the PSU circuit I also mention in an earlier post, with a slight re-design to accommodate the chassis' 80-0-80v transformers. Yeah, the regs get a bit warm... Wadaya gonna do???
LOL
Sounds bloody lovely on my new Dundee6s
cw

 

[copperweed]

http://www.diyaudio.com/forums/atta...0793-hybrid-diy-cct-lm3886-6n11-psuschem1.jpg

I pulled the 4700uFs and used 2200uFs @63V instead, and also increased the zenner diode's 3K9 feed resistors to 4K7 ohms, but that's about it folks.

cw

 

[copperweed]

Got sum pics up here

Scrap-lifier MkII; 4ch, 50w, Fully Regulated 35-0-35 PSU. Sounds Amazing! | Alacrity Audio

cw

 

[copperweed]

The donated chassis was a Sherwood 200W monster of a power-amp. The main boards had gone down and were cooking the transformers. It was a full dual mono-block design to start with, so I just had to replace the boards and include a supply regulator to drop the 80-0-80 float-voltage to a more manageable 35-0-35.
I tried to fit a volume-control, but the fascia stands so far off the front of the chassis that the potentiometer stem does not reach through the aluminium extrusion.

'First-World' problems...
Fascia-plate being a right-royal PITA to get it pretty, if I'm honest. I just haven't got the time or patience (or space!!!) for spray-painting. Might make a new one in our usual perforated ali.
More pics when we've got more done.
Any questions about our 35-0-35 vdc, 12-0-12 adc Power regulators?
cw

 

[Bangla H]

Hallo copperweed.
I've also ordered the Boards from Jims- Audio Ebay Store HongKong.
Than they are fully assembled with my own Parts- mostly German Distributor.
The PSU- Capacitors are KG Nichicon 15000µF/50V ordered by HifiCollective in UK.
The Sound also impressed me. So i began to Test different familar Tubes, like: 6N23P;
6922EH; 6N1P; 6N1P-I; 6N1P-EV. It Ends up that i was in Twise about the Plate- Voltage by reading in Forum. I tell that Question to an Expert, he is also Distributor
Vacuumtubes and needed Parts.
I think he crossed Hands above his Head and thays "oh Man".
After his anthwer i ordered a customize toroid Transformer with all needed Voltages.
Core: 150VA, 24-0-24V, Heating:6,3V 0,5A, Plate Voltage in three 3!!! Steps 0-60-75-95V with some mA.
I tested out everyone for a Wile and end up with the highest 95VAC Voltage.
In my opinion THAT is the way to get more Sound out by this Hybrid Amp, not only by
higher Ub for the LM3886.
The Input Buffer, i feel, can better work in optimal Condition (higher Current Workpoint?) with higher Plate Voltage.
If possible you should test it out.

Regards.

 

[Dondragonfly]

Transformer question

Ive been eyeballing this intriguing project for a while now. I have one toroidal transformer handy and I hope I can make it work. It's 28-0-28 4A with taps at 18-0-18 .3A. So the voltage is a bit high but ok as voltage is concerned, will the 4A affect anything negatively? It would be poetic to make the 18v work for the tube/pre section but no biggie if I have go another direction there.

 

[copperweed]

Ive been eyeballing this intriguing project for a while now. I have one toroidal transformer handy and I hope I can make it work. It's 28-0-28 4A with taps at 18-0-18 .3A. So the voltage is a bit high but ok as voltage is concerned, will the 4A affect anything negatively? It would be poetic to make the 18v work for the tube/pre section but no biggie if I have go another direction there.

Hi Dragonfly. Hope your project went well (4A taps should give plenty of current). There are some links under the board to separate the tube supply, but on my boards the components are missing so I haven't tried.
One thing I have found to work well is to supply the tube heaters with a pre-regulated supply. I'm using a 9v wall-wart.
cw