*** The DIY Audio Thread ***

[MikeHunt79]

delivery for the cheap dac was about 4 days. no customs either.

Ok, I'm looking on e-bay now. There seems to be 2 versions, one with a transformer and one without. The descriptions are pretty poor, so I'm guessing the tranformer simply so make the 5v, 12v and -12v the board needs?

 

[chet84]

sounds very good for the money. probably the best bang for buck amp you can build.

I have a enough parts to put together a kit if anyone is interested (at cost + postage). Only thing to bear in mind is i had some bits an bobs before hand (e.g caps).

no NFB pot (or tube saturation). This amp design is by Pete Millet, he has used a novel method for biasing the mosfets (on the big heatsinks) with the tube heaters. Its a simple circuit that works wonders.

Hi mate - have you still got this - looking at getting my hands dirty

 

[Kanifee]

Both options should come witht he DAC and Power supply board, the power supply board regulates and manages the current down to a level each rail can use, 5v, 12v and -12v, the optional extra the transformer takes the mains current of 230v ac and takes it down to a manageable value the psu can work with ie: 12v 0 12v rails.
Depending how anal you are about things depends on what option to go for, the transformer supplied will be quite adequate to do the job but will no means be a Best option, better transformers produce better music, to what degree is debatable and down to personal oppinion. For ease get the option with the trafo, if you want to get all audiophile on your self opt for the one without it and get a Higher quality trafo, what differance it will make i cant comment on as im yet to hear mine sing atall!

 

[adamau5]

Chet84 - sorry its gone, but i can give you a bill of materials from farnell if you want.

 

[adamau5]

wouldnt worry about the transformer, these dacs need naff all current. I got the one with the blue encapsulated tranny. Works a charm.

just looking at output caps options, am i right in assuming that becuase this will be goign to volume pot on the amp (50k) that the dc blocking cap can be super small without effecting bass rolloff.

 

[MikeHunt79]

Transformer option ordered, thanks guys.

Is there any more info on these boards as the e-bay listing has very little info? I've had a quick hunt on diyaudio, but mostly turned up irrelevent threads.

 

[p4radox]

p4radox ill be keeping a close eye on your amp10 build as this is a serious contender for my main amp in replacement of my LM3886, very fortunate its going to be paired with the cheap DAC as well, i can treat it as a precursor to my own project. Do you my mind keeping a detailed build log and construction log? it will make very interesting reading while i work on my shigaclone and cheap DAC, will be interesting to see what hurdles you come across and what your overall thoughts about the pairing are!

Will do. I was planning on doing a log anyway.

Transformer option ordered, thanks guys.

Is there any more info on these boards as the e-bay listing has very little info? I've had a quick hunt on diyaudio, but mostly turned up irrelevent threads.

A few that I bookmarked a couple of weeks ago:

http://lampizator.eu/LAMPIZATOR/LAMPUCERA/CD DAC Lampucera lampizator.html

http://www.diyaudio.com/forums/showthread.php?s=&postid=1561987#post1561987

http://theartofsound.net/forum/showthread.php?t=315

http://rockgrotto.proboards39.com/?board=m&action=display&thread=1672&page=1

I haven't read them all, so some may be completely irrelevant!

 

[Dr.EM]

Some progress with the midtop speakers. I have one functionally complete, just needs prettying up . Actually think this one will look better with grilles on, the large "border" itn't very attractive imo.



Inside behind the mids is the wavey enclosure and between this and the main box is a sand fill to control panel resonances. The baffle is 12mm ply and 12mm MDF bonded together. All this means that the speaker weighs about 30kg. Hard to judge the sound as it doesn't have a matching partner (just a prototype) nor does it have the essential bass cabs which it will eventually be perched atop. Overall clear though, especially with voice, but I still hear resonances and can't figure out why. Perhaps it's just the room (bedroom), its far from ideal for a system of this size and I am aware of this

 

[Kanifee]

Is that not tucked a tad close into the corner? Id try it with room to breath, where is the bass port? Looking pretty good though

 

[Dr.EM]

I will need to move everything out of here and set it up the best I can when its all ready. Will invitably still be near the corner though. Definately no bass port on this box, its only mid and top range so both are sealed. As it would happen my bass will also be sealed when its finished. This allows use of an electronic bass extension filter whilst providing lower group delay and elimination of port noise etc. These are the bass drivers waiting for thier boxes:

http://www.swanspeaker.com/product/htm/view.asp?id=64

 

[MikeHunt79]

Dr. EM - nice to see some more speakers in the thread. My tapped horn is still bare ply, my thoughts are function over form. What active crossover are you going to be using?

Also, a well designed tapped horn will have no group delay also, but I've looked at the specs of your bass drivers and they aren't really ideal for a tapped horn enclosure, so you're probably better off going to sealed anyway.

A few that I bookmarked a couple of weeks ago:

Thanks for the links, I'm working my way thru the first link right now, it looks like a very nice DAC. It has balanced output to also which is a bonus (for me at least). I can't wait for it to arrive now.

 

[p4radox]

Mike, what happened to the "Top Tips" sig? I liked that...

 

[Kol]

3hrs and £33 = point to point mini millet hybrid.

If you fancy building one for me, I'd love one of those. Looks awesome.

 

[adamau5]

I have ran out of valves unfortunately so would have to do a special order.

I do have a soha amp for sale, lovely valve amp using 12au7. its more powerful than the mini millet. bit more expensive though - £85 in parts.

 

[Dr.EM]

Hi MikeHunt79, I'll be using this crossover:

http://sound.westhost.com/project09.htm

I have the PCBs, just need lots of breadboard experimentation before comitting to solder! Currently have very rudimentary 12db crossover on breadboard, component values arn't very exact. The crossover unit will also have to accomodate the ELF circuit for bass, possibly tweeter phase/time alignment correction and possibly even notch filters if resonances are still an issue. Also in the box will be a 6 channel attenuator and the startup logic to switch on the amplifiers. Should be fun

For my application I think your right, sealed will be best. I didn't mention but those drivers will cross to the midtops at about 400hz so the the driver will need to be near to them and forward facing. They perform quite well in a sealed box even without any extension circuitry, they have slightly subwoofer characteristics in that respect (low fs, fairly high xmax, high power) yet still have the decent upper range performance of a typical woofer.

 

[MikeHunt79]

Mike, what happened to the "Top Tips" sig? I liked that...

It will make a return once I get some hosting sorted.

Hi MikeHunt79, I'll be using this crossover:

http://sound.westhost.com/project09.htm

I have the PCBs, just need lots of breadboard experimentation before comitting to solder! Currently have very rudimentary 12db crossover on breadboard, component values arn't very exact. The crossover unit will also have to accomodate the ELF circuit for bass, possibly tweeter phase/time alignment correction and possibly even notch filters if resonances are still an issue. Also in the box will be a 6 channel attenuator and the startup logic to switch on the amplifiers. Should be fun

Good luck! Sounds like you have quite a challenge on your hands (pardon the pun). believe it or not, I also plan on building that exact same crossover for my car, but just the very basic version (2 way, 112Hz crossover, 24db/oct). Did the PCB's take long to arrive from Aus? I was planning to just use breadboard for the whole crossover.

I did cheat a bit tho, I also have a DCX2496 DSP unit which I tried in that car for a while, just to see what crossover slopes and crossover points sounded nice before deciding on 112Hz. It's an amazing unit, and also auto time alignment (with a mic connected), limiters, EQ's, etc. I'd at least consider this unit as it would kill many birds with 1 stone, and even if you don't plan on using it for your final sound system, it's great for testing out different crossover slopes and time alignment.

You'd still have to use some sort of 6 channel attenuator tho, I've also looked into this, and found quad gang pots readily avaliable, but 6 gang pots a little harder to get. Another option is a stepper attenutaor, but these are pricey and I imagine 6 channel versions being even more expensive.

For my application I think your right, sealed will be best. I didn't mention but those drivers will cross to the midtops at about 400hz so the the driver will need to be near to them and forward facing. They perform quite well in a sealed box even without any extension circuitry, they have slightly subwoofer characteristics in that respect (low fs, fairly high xmax, high power) yet still have the decent upper range performance of a typical woofer.

Yep by the looks of the specs they should go pretty deep, I didn't realise you were crossing over as high as 400Hz, this definately rules out tapped horns as they are only good for limited bandwidth (mine isonly useful between 30-100hz).

If your bass units act as a stand for your mid-tops, you may not need much (if any) time alignment... If your unlucky you may get some bass cancellation as you have speakers in different places doing things below 100Hz, but with any luck you'll be able to get round this with good speaker placement or basic room treatment.

 

[Col_M]

Hi guys, this definitely looks like something I'd like to get into and give a go. How much electronics knowledge do you need to take a project on, I've got a reasonable electronics knowledge as I was taught a few electronics modules at uni so know most of the basics, I've also done a lot of soldering in the past (did work experience at BAe).

Where is a good place to read material online and get an understanding of how amplifiers work? I like the idea of making a tube amp to drive some smallish bookshelf speakers if that helps point me in the right direction

 

[chet84]

Chet84 - sorry its gone, but i can give you a bill of materials from farnell if you want.

That would be great! Would you say it's relatively simple? I know little behind audio electronics but completed an electronics and communications degree a couple of years ago!

 

[Dr.EM]

MikeHunt79, The boards took no more than two weeks but I can't remember exactly how long it was. I paid via paypal. Probably worth getting, breadboard in a car might not last very well; stripboard should be up to the job though.

The DCX2496 sounds like a very useful bit of kit, would certainly save effort with my limited measuring equiptment. It'll either be that or lots of experimenting on breadboards. Will likely end up on the PCBs in the end anyhow.

I would like to use this for the attenuator:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=81541&highlight=
But the chips look hard to get.

I have to crossover not much lower than 400hz. Although those drivers look like they might go quite deep they are strictly midrange with a fs of 250hz! The time alignment would be between the mids and tweeter but hopefully won't be required anyhow. The tweeter protection capacitor adds some shift so that may need to be corrected is all really. Hopefully I can keep a smooth enough response with the 2 woofers but there are room nodes to compete with anyhow so bass performance in this room will be hindered a bit.

 

[MikeHunt79]

Hi guys, this definitely looks like something I'd like to get into and give a go. How much electronics knowledge do you need to take a project on, I've got a reasonable electronics knowledge as I was taught a few electronics modules at uni so know most of the basics, I've also done a lot of soldering in the past (did work experience at BAe).

Where is a good place to read material online and get an understanding of how amplifiers work? I like the idea of making a tube amp to drive some smallish bookshelf speakers if that helps point me in the right direction

Hi, the soldering experience will help a great deal. Unless you plan on soldering SMD parts you shuold have no problems.

The diyaudio wiki has some good info, but far from complete:
http://www.diyaudio.com/wiki/

Have a look on the forum also, there is plenty of info there, have a look at existing projects for some inspiriation...

MikeHunt79, The boards took no more than two weeks but I can't remember exactly how long it was. I paid via paypal. Probably worth getting, breadboard in a car might not last very well; stripboard should be up to the job though.

Good idea, I'll try it on stripboard, I should be able to build it into the amp chassis so it should be pretty well protected.

The DCX2496 sounds like a very useful bit of kit, would certainly save effort with my limited measuring equiptment. It'll either be that or lots of experimenting on breadboards. Will likely end up on the PCBs in the end anyhow.

I would like to use this for the attenuator:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=81541&highlight=
But the chips look hard to get.

I found another page which may be of interesting while looking for info on that chip:

http://www.picbasic.co.uk/forum/showthread.php?t=7717

It does look like it might be a PITA to get hold of tho...

I have to crossover not much lower than 400hz. Although those drivers look like they might go quite deep they are strictly midrange with a fs of 250hz! The time alignment would be between the mids and tweeter but hopefully won't be required anyhow. The tweeter protection capacitor adds some shift so that may need to be corrected is all really. Hopefully I can keep a smooth enough response with the 2 woofers but there are room nodes to compete with anyhow so bass performance in this room will be hindered a bit.

Ahh, I didn't see that they had an fs of 250hz (I'm sure it said 26Hz on the website). I guess you will have less problems with nodes with less going on below 100Hz.

Hopefully you should be able to use a few op-amps as all-pass to compensate for the tweeter cap.