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The Vinyl Adventure
31-07-2009, 16:02
right, im going to slowly build one of these chipamp kits
i think im going to start by doing as much as i can myself with the help of you guys!
i feel that i may get to the stage that im taking at least one of you up on some hands on help (mike) but until that stage i need some help selecting parts/suppliers

firstly can anyone tell me the difference between these:
lm3875
lm4780
lm3886

i have found US suppliers very easily for the top two but have read about the other 1 too.. does anyone know of uk supplyers?

secondly
if i get something like this http://audiosector.com/lm3875.shtml am i right in thinking the only other parts i need are

transformers
plugs and sockets
on/off switch
internal wiring

case is sorted - but im not sure about how its going to work out, is it possible to have 2 cases that plug into the mains individually, propper monoblock style?

im literally crap at this, but i think with the help of all on here i will get somewhere (especially if i can take people up on the offer of building the scary bits ie mains bits)

this is going to take me a while i think as money is a bugger and i still havent got round to getting the 1210 yet but the way i see it these threads arnt going anywhere and i can refer back to them when im ready

The Vinyl Adventure
31-07-2009, 16:10
oh.. and i am right in thinking this is this "gainclone" right

alb
31-07-2009, 16:43
Hamish.

It's a long time since i built a gainclone, but i think a LM3875 would be adequate for most people.
These amps are easily built without a pcb, but if this is your first go at it then one of the kits would be a good start. I would go for the "classic" kit as i don't think the other warrants the extra dosh.
You will have to buy the things you have listed but they need not be expensive.

Have a look at Nick Whetstones excellent site here.
http://myweb.tiscali.co.uk/nuukspot/decdun/gaincloneindex.html#top1

I had never built an amp until i read this. There is sufficient info here to successfully build a gainclone, and it will answer most of your questions.
There will be enough help on here to talk you through any problems.:)

leo
31-07-2009, 16:47
Do a have a good read at the above posted Decibel site, its what got me started in diy , theres a lot of good info

The chip amps are just like op-amps, most of the important bits crammed inside a single chip, external bits are things like FB resistors for setting gain, filters, psu 's etc

LM3875 is the most popular mono chip, majority of Gainclone (or chip amps) was based around these
Rated at 56w

LM3886 is a more powerful version of the LM3875, its pin outs is a little different to LM3875 so their not interchanagable , its also mono
Some claim the less powerful LM3875 is the best sonically
Rated at 68W

LM4780 is a stereo version built in a single chip which can be configured as Bridged mono
Rated at 60w stereo or 120w mono

These chips are avaialble from Farnell, RS may also stock them

The modules from Audiosector are mono so you can build a pair of monoblocks in separate cases, I think you only get the pcbs and components in the kit, things like wiring , plugs etc isn't included

Theres going to be a lot of kits out there, even ones using valves on the input
http://cgi.ebay.co.uk/60W-HLLY-AMP-4780-HIFI-AMPLIFIER-Board-National-LM4780_W0QQitemZ260451687563QQcmdZViewItemQQptZLH_ DefaultDomain_0?hash=item3ca4215c8b&_trksid=p3286.m63.l1177

http://cgi.ebay.co.uk/HIFI-AMP-KIT-radio-tube-6N11-LM4780-2-60W_W0QQitemZ180388773347QQcmdZViewItemQQptZUK_Aud ioTVElectronics_HomeAudioHiFi_Amplifiers?hash=item 2a00023de3&_trksid=p3286.c0.m14

Most Gainclones/chip amps I tried was hardwired onto the chip pins, obviously a pcb kit would be a lot easier for you.
Hopefully others will post links to any kits they've tried and can comment on the build etc

These chip amps don't go well with hard to drive speakers, infact the more sensitive the better

Tom472
03-08-2009, 12:03
Looks good - with all the mains stuff you can have a go, then post some good close-up pictures of it and we can tell you if it's safe etc.

Not sure if I'm missing something but you'll need heatsinks in addition to those things listed in the first post. I have one of these in my house somewhere which I built a long time ago and IIRC it got pretty toasty with my dodgy homemade aluminium angle based heatsinks.

The build should be pretty simple, the one thing I messed up when I first built one was to ground the input sockets to the metal case - use insulated sockets.

Regards
Tom

RochaCullen
06-08-2009, 09:31
Hey guys,

I have been doing a lot of reading about building a gainclone and you are right, Nick Whetstones site is by far and away the most comprehensive and informative. One thing I thought was really interesting was how he swapped out his normal power supply for a switch mode power supply, and this, he says, gave him some of the best results out of all his mods to the gainclone. The details are here:

http://myweb.tiscali.co.uk/nuukspot/decdun/gainclonesmps.html

I want to build mine with an SMPS (switch mode power supply), but can't get my hands on the one nick mentions. Can anyone point out a power supply on farnel or RS that could be used, or give a basic check list of features one should look for, e.g., single output, 60W, 15v? This would be very handy. I have done plenty of reading on SMPS, but the things I find tend to talk above my modest level of understanding.

Ideally (if my first works out well), I would like to build three gainclones, one for each standmount speaker in biamp config, and then a separate mono to power my sub. So this would be three SMPSs: two SMPSs powering two channels each (two biamp standmount), and one powering onechannel (mono sub).

The other thing that I wondered about was how I would daisy chain my gainclone power amps. No one seems to include the inputs AND outputs in their gainclones. So basically my question is, do I need to do anything special to allow the pre-amp's signal to pass through one gainclone and into the next, i.e., my pre-amp only has two outputs, is there much involved in pushing the signal through three further boxes?

Any advice would be much appreciated.

Nathan

roscoeiii
07-08-2009, 03:30
diyaudio.com is as comprehensive a DIY site as I've come across. You can find many details on chips and design options there. Although this will require digging through tons of pages of forum threads.

I bought a pair of monoblock Gainclones built by Tim Rawson (rawsonte on Audiogon), and am loving them paired with a DIY Bride of Zen preamp (Nelson Pass degin). Pics of the Gainclones below.

The Vinyl Adventure
07-08-2009, 07:26
How much did you pay for them? I know you ahve mentioned thus on another thread but I couldn't find it when I started this one

Puffin
10-08-2009, 05:51
I have built lots of Gainclones. If you need some help you might find you live near someone who has experience of building these. Where in the UK are you?

This may not help you to build a kit, but I have 2 Chipamp.com monoblocks (LM3886) that have been gathering dust for ages. They are in enclosures which are a bit unusual, but you could re-case them. It would give you an idea of what Gainclones sound like. You are welcome to take them and try them.

Just looked at your site. You are based in Worcester. I am in Surrey.

Krisbee
10-08-2009, 11:50
Hamish,

Have you seen this on-going thread re-building DIY monoblock amps based on LM3886 kits from ChipAmp.com?

http://community.whathifi.com/forums/1/260055/ShowThread.aspx

In blog like fashion there's plenty of instructive photos and commentary as the build progesses.

The Vinyl Adventure
10-08-2009, 12:07
thank you i have... i have been following it my self with interest! he is much ferther on in his diy abilitys than me i fear... it is very interesting none the less!!

i am at the mo waiting on aranging payment with another member of this forum to buy a pair of built - uncased lm3875 kits and some smps psus... when i get these bits i will be back on here for ferther advice on how to get the best out of it!!

RochaCullen
10-08-2009, 15:57
Hi Hamish,

I'd love to know who this forum member is, as they might be able to point me in the right direction as regards the right SMPS to use for a gainclone. Apparently they improve the sound. Getting to grips with which are the right ones to use is not the easiest.

Nathan

The Vinyl Adventure
10-08-2009, 16:09
he is called smithy but i dont know if he will be able to help you anymore than this site does as they are the same ones he used

http://myweb.tiscali.co.uk/nuukspot/decdun/gainclonesmps.html

alb
10-08-2009, 17:46
Nathan.

If you are planning to biamp, i take it your speakers are not all that efficient.
If this is the case, you may need two of the smps modules per amp.
If you manage to buy one, i think you may struggle to get the other five.

Also, other available smps supplies might not be up to same standard of Skynet modules, and unless you happen to be an expert, there's no real way of knowing.

Of course there may be some experts on here.

The Skynet modules are also perfect for some of the Tripath amps as well, which is what i used mine for.
In some respects i prefer these to the chipamp.

A chipamp with a conventional transformer/filter power supply, can still sound very good. I thought mine to be at least the equal of a Musical Fidelity A3, which i fairly quickly sold, and i didn't miss it at all.
Shortly after this i stopped buying hifi and got stuck into DIY.

RochaCullen
20-10-2010, 14:05
Hi,

I've finally taken the plunge and bought myself the dual mono setup from chipamp.com. I am going to build two separate monoblock gainclones. I've ring fenced all items I need but one: the transformer.

I will of course need two transformers. Most (all as far as I see) documentation on the net focuses on the power supply of a stereo gainclone, so I have no idea what the optimal transformer would be for a monoblock.

I've gone for the lm3886 and the current transformer I am looking at is a 2-25v, with a rating of 300va, you can see it here on RS: http://radionics.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2238207

The other thing I am worried about is the output current, and what that should be.

Any help would be appreciated guys.

Thanks,

Nathan

Reid Malenfant
20-10-2010, 14:47
First up find out the maximum DC votage rating of the chips that you'll be using ;) From what i have seen most people tend to use 22 0 22V transformers & these will give you approximately +/- 30V DC. 25V secondaries will result in about +/-35V rails allowing for rectifier losses & transformer regulation.

Once you know the maximum DC votage you can roughly calculate the RMS power that you can supply to your speakers. Tbh a 300VA transformer would be very nice for powering both amplifiers let alone a single monoblock.

As you are only likely to be looking at 40 - 50 W RMS into 8ohm max or 100W RMS into 4 if you are lucky, you'll be able to get away with a small VA rating transformer (though a bigger PSU tends to make amps sound better) of 225VA or even 160VA.

Just checked the LM3886 specs & it'll be fine with a +/- 35V supply. This will give a bit more power than the above so i'd suggest a minimum of 200VA transformer per amplifier. That's still well overated though ;)

RochaCullen
20-10-2010, 15:17
Thanks Mark,

The price difference between the 225 and the 300vac transformer is minimal. So I might just go for the bigun.

I've just finished reading through the whathifi thread: http://community.whathifi.com/forums...howThread.aspx

Is it just me or has this guy gone a little over the top. Is there really any need for a soft-start circuit?

The safety steps are understandable as the prospect of playing with mains voltages scares me too. But is there any easier way of ensuring your saftey without building some made light bulb indicator as this guy has?

He has also used an EMI/RFI filter, could this also be a bit over the top, or could it potentially affect the sound in a negative way?

Regards,

Nathan

Reid Malenfant
20-10-2010, 15:21
Linky no work for me :eyebrows:

Until i can see what this guy has done i can't really comment. If i remember correctly though a lot of these types of chip will have a shutdown for the output stage. Thinking about it this one does to, the -Ve votage rail needs to be at least 9V DC lower than ground for it to activate, this tends to get rid of thumps in the loudspeaker at switch on & off.

RochaCullen
14-02-2011, 17:59
Hi All,

Its taken an age, but I have just about assembled everything I need to build my gainclones.

So to start with I got onto chipamp.com and ordered the dual mono kit, and with a little bit of effort and some sifting through the internet for pictures to make sure I was putting the right things in the right places, I assembled the two amplifer boards and the two power supplies.

Amp board:

http://i830.photobucket.com/albums/zz230/rochaCullen/GaincloneBuild/ampBoard.jpg

Power supply:

http://i830.photobucket.com/albums/zz230/rochaCullen/GaincloneBuild/powerSupply.jpg

I've just noticed a stray bit of wire on the board, oops.

Full set:

http://i830.photobucket.com/albums/zz230/rochaCullen/GaincloneBuild/chipampKit1.jpg

The next thing I had to decide upon was the transformer I was going to use. I went a little overboard and ordered two 300va torroidial transformers.

http://i830.photobucket.com/albums/zz230/rochaCullen/GaincloneBuild/transformer.jpg

I also went a little overboard on the heatsinks I ordered, but I had a very specific design in mind and the heatsinks had to be a decent size to carry this off. I wanted to create a set of amplifiers that looked a little like the meridian monoblocks of about a decade ago, the 205 etc.

Front:

http://i830.photobucket.com/albums/zz230/rochaCullen/GaincloneBuild/heatSink1.jpg

Back:

http://i830.photobucket.com/albums/zz230/rochaCullen/GaincloneBuild/heatSink2.jpg

In an effort to isolate the transformer from everything else and also isolate the power supply from the amp board, I asked my father to make a couple of pieces for me to encase the transformer. I also asked him to drill the heat sinks, as you will notice there are four holes drilled so the heatsinks can be screwed onto what will be a wooden case, but also a fifth 3mm hole that was drilled to allow the LED from the power supply be seen.

http://i830.photobucket.com/albums/zz230/rochaCullen/GaincloneBuild/isolation2.jpg

The transformer enclosure looks a little rusty in the picture, but is really not at all that bad in the flesh, so to speak.

Based on some advice from Leo our DIY room moderator, I decided against getting myself an IEC inlet with surge protection et al, opting instead for a simple enough connector with an on board switch.

Front:

http://i830.photobucket.com/albums/zz230/rochaCullen/GaincloneBuild/IECInlet2.jpg

Back:

http://i830.photobucket.com/albums/zz230/rochaCullen/GaincloneBuild/IECInlet1.jpg

I am a little confused as to how this will be wired up, but I am sure I will be able to get one or two hints on how to do this from some of the good people on this forum.

So I have only three things left to get my hands on, some phono sockets for the input signal, binding posts for the speaker output and some wire to wire it all up.

To give you an idea of how I will be assembling the items, here is a layout picture for one of the mono gainclones.

Elevation:

http://i830.photobucket.com/albums/zz230/rochaCullen/GaincloneBuild/layout1.jpg

Plan:

http://i830.photobucket.com/albums/zz230/rochaCullen/GaincloneBuild/layout2.jpg

Inside the case all items will be raised up about 10mm or so, to allow the internal wiring to go where it needs. I can't wait to get the rest of the pieces, and start assembling.

I will be needing some advice on how to test each part before I go wiring things up, so I don't go breaking anything. Also any hints or tips on the type of wiring to use or configuration, e.g., do I braid the + and -, do I use thin solid core for signal, etc., would all be very much appreciated.

The Vinyl Adventure
14-02-2011, 18:45
Oooo looks like a lot of fun!!
Looking forward to seeing this get finished!

Rare Bird
14-02-2011, 19:12
can't you make the enclosure from non ferrous metal: Copper or summert?

RochaCullen
14-02-2011, 21:24
I may have to give it a coat of some paint, that should sort it, but as I mentioned in the post its actually not nearly as bad as it looks.

Rare Bird
14-02-2011, 21:33
i was refering to the ferrous metal you made it from, not a good idea imho..

RochaCullen
16-02-2011, 17:09
So I want to get started on this thing by wiring my IEC connector to the power supply, so I can test that it is supplying the right values.

Problem is I have no idea how to wire the IEC connector that I bought. :mental: Its a little on the complicated side.

On connectors I've used in the past I've wired to positive, negative and earth. But there are a few more connections here.

I can only assume that I run both positive and negative vertically downwards on each pin to connect first to the fuse and then to the rocker switch?

Any direction would be appreciated.

The following is the connector:

http://i830.photobucket.com/albums/zz230/rochaCullen/GaincloneBuild/IECInlet1.jpg

and

http://i830.photobucket.com/albums/zz230/rochaCullen/GaincloneBuild/IECInlet2.jpg

Nathan

Reid Malenfant
16-02-2011, 17:56
Hope this helps :) 3779

RochaCullen
16-02-2011, 20:58
Thats fantastic mark, thanks for your help on that. Onwards and upwards.

Nathan

RochaCullen
23-02-2011, 10:25
Hi,

I am about to do my final run to Maplin to get the last bits of kit needed and I was reading a tip on the decibel dungeon site: "Place a small Class X1 rated capacitor (around 0.1 uF /275 volts is fine) across the switch contacts. This will help protect the contacts from arcing and also stop them from making a noise when the switch is operated. This is optional but recommended. "

I've not managed to find a Class X1 cap, but found a Class X2:

http://www.maplin.co.uk/metallised-paper-rfi-class-x2-capacitors-98166

Do you think the 0.1 uF cap listed here would do the job?

Thanks,

Nathan

lurcher
23-02-2011, 10:54
X2 will be fine, X1 is rated for a impluse of 4kV, X2 2.5kV, both are designed to go line to neutral.

RochaCullen
23-02-2011, 11:06
Thanks Nick,

Getting there slowly but surely.

Nathan

RochaCullen
23-02-2011, 11:22
Another thing I probably need to get is some heat sink compound.

Does anyone know if I definitely need to put compound between my LM3886 chip and my heat sinks?

Nathan

RochaCullen
23-02-2011, 11:57
Just had a look at the chip and it is the LM3886TF, so its the insulated version, therefore no compound required.

RochaCullen
23-02-2011, 16:17
So, I've returned from Maplin, freshly ripped off, (this chip amp is proving more expensive than I had initially hoped). I have all remaining items needed to get this thing finished.

So tonight I want to hook up and test my power supplies.

Now this bit is confusing me. At the back of each of my power supplies I have 2 sets of double inputs, that is, two little terminal blocks that I soldered to the bottom of the board, into which the transformer is to be wired.

The transformer has one set of primaries and two sets of secondaries.

http://i830.photobucket.com/albums/zz230/rochaCullen/GaincloneBuild/transformer.jpg

Blue-Brown obviously are wired to my IEC input. But are both Red-Black and Yellow-Orange wired into the back of the power supply using the aforementioned terminal blocks? Red-Black into one and Yellow-Orange into the other?

You can see the wires going into the thing in a pic from the chip amp site, but the business end is hidden from view!!!!

http://www.chipamp.com/diyaudio/snubber.jpg

The assembly guide that comes with the chipamp kit does not go into detail on this, and anything I read on the web seems to take this part as a given.

Any help appreciated.

Nathan

Puffin
23-02-2011, 16:50
I seem to remember that the rectifier boards are marked AC1 and AC2 on both feeds. So yes, Red and Black to one set of diodes and the Orange and Yellow to the other.

lurcher
23-02-2011, 16:59
Just had a look at the chip and it is the LM3886TF, so its the insulated version, therefore no compound required.

Heat transfer paste will still improve the thermal coupling between the device and the heat sink.

RochaCullen
23-02-2011, 17:01
Yea, I did some more reading after I posted that comment and that was the gist of what I got. Apparently, elimination of air between heatsink and chip is key. So I'll be making one more trip to the shops.

Nathan

RochaCullen
23-02-2011, 17:04
So, just say later on this evening all is going well with the power supply and the voltages it is outputting are what I need. How do I then link it up to the amp board?

I see a variety of PG+, PG-, V+ and V- on both power supply board and amplifier board. Are these to be connected? And if so how?

Nathan

RochaCullen
24-02-2011, 09:43
Just had a look at the chipamp assembly manual and the question below is covered.


So, just say later on this evening all is going well with the power supply and the voltages it is outputting are what I need. How do I then link it up to the amp board?

I see a variety of PG+, PG-, V+ and V- on both power supply board and amplifier board. Are these to be connected? And if so how?

I was all set to get cracking on testing the power supply last night, but as we've now got a 4 week old baby in the house who just wasn't settling, I had to shelve any plans I had with my soldering iron. I think the weekend will have to do. Although the six nations might have something to say about that :cool:.

RochaCullen
08-03-2011, 12:42
I know its taking a lot of time, but I got around to testing the boards last night:

http://i830.photobucket.com/albums/zz230/rochaCullen/GaincloneBuild/gainclonetest.jpg

I'll be starting on the enclosure this weekend, which should be a bit of fun. But a lot of work.

I've been getting distracted by this little fella, seen here having his bath first thing this morning as I was leaving for work, 5 weeks old and counting :):

http://i830.photobucket.com/albums/zz230/rochaCullen/morningbath.jpg

Alex_UK
08-03-2011, 13:52
Congrats Nathan! Don't get the two projects confused! :eyebrows:

RochaCullen
08-03-2011, 13:59
Congrats Nathan! Don't get the two projects confused! :eyebrows:

Ha. I don't think little Harry would appreciate that!

The little fella does have a fine appreciation of music, however. He was having a colic induced conniption the other night, and I decided to try and calm him down with some choons, and during one whole play of Simply Red, Stars (Surprisingly good recording) there wasn't a peep out of him. :cool: