Thinking of a DIY amp

[Paul]

Hi all
I'm new here and have been reading into the DIY amps as I want a dedicated stereo amp for music.preferably a power amp/mono blocks from my TC7520

Can you please help , I have never done anything like this before but am eager to learn and can read a wiring diagram and solder fairly well as I do this in my job quite alot ( motor vehicle tech )
I have seen this site and it looks fairly easy to build, but I wanted to know what you all think about it as you all seem to know your stuff.
http://www.diabloid.pwp.blueyonder.co.uk/GBV2.html
Thanks
Paul
:)

[aquapiranha]

Hi Paul. I have heard a couple of gainclones in my system (built by John Blackburn, a member here) and they are great and don't appear to hard to build. What speakers are you partnering them with?

Steve

[Ali Tait]

Well that's a sweeping question! As Steve says,what speakers do you use,and what kind of amp are you looking for? SS,Tripath,Chip,Valve? Have you any thoughts on which path you wish to go down?

[DSJR]

Another fairly easy suggestion may be a ZAP250 from Avondale - What it consists of is a couple of used Naim or new NCC200 boards, a suitable transformer, recification and smoothing parts and the option of a case. maybe not what you're looking for, but results are very good for a few hundred quid and easily as good or better than an "Olive" NAP180.

[Paul]

Hi
Sorry should have put that in , speakers are Tannoy MX2 standmounters on Alphason stands.
The sort of amp I'm looking for is just one that sounds better than the Denon AVR1910 I use for everything atm, not sure if I want to go Valve yet , I like the idea but have yet to hear one .Not sure of what path to follow , but to start with something fairly simple to get my foot in the door so to speak.

The only amp's I've heard are Denon and Kenwood and I'm giong back a few year since that happened, there are no hifi shops near me apart from a Sony centre .

So in a nutshell something/anything with more detail and better soundstage.
Cheers
Paul:)

[DSJR]

Where you live is fairly close to Audio File in Bishops Stortford, although since Bev sold it I don't know what state it's in. HiFi dave is located just south of Saffron Walden and he has loads of affordable goodies for your delectation, allbeit ready built and warranted. the Rega Brio comes to mind as a decent UK made and affordable little amp of great capability.

Otherwise, have a look at a Gain-clone or similar. I need to get a proper drill-press, as the thought of drilling out metal boxes terrifies the poo out of me. it was bad enough drilling out a plastic box for the X10 power supply and I've just bought another for the regulated Lentek supply....

[Ali Tait]

A good way to start I'd say is with a Tripath amp.Get some TA2022 boards on ebay and then all you need is a suitable transformer and a box to put it all in.Plenty of threads in the class d section of the diyaudio forum.Dead easy to do,and no high voltages like in valve amps.I find they sound very good too,with more than a touch of the valve sound,but with the bass grip of a good SS amp.Will certainly comfortably outperform your Denon IMO,and for not a lot of dosh!

[Reid Malenfant]

Well we are here to give you ideas ;)

Here are amplifiers in various states from pre-populated PCBs to just the PCB itself or a kit of parts (http://www.signaltransfer.freeuk.com/) :)

These amplifiers were designed by a chap called Douglas Self, who knows a thing or two about audio. I can't say i have listened to any myself but he has taken a bog standard generic class B amp & gone to town on it to get distortion as low as possible.

If i was going to buy one (sorry, a pair :lol:) it'd have to be the Trimodal amps, this way you get class A when you want it just by flicking a switch even while the amp is powered up :eyebrows:

If you are interested the same people are selling on ebay & at the very same prices (http://shop.ebay.co.uk/audioginge/m.html?_nkw=&_armrs=1&_from=&_ipg=&_trksid=p3686) :)

I happened to recently purchase one of the balanced output RIAA phono pre amps from this chap & it arrived in 3 days as a kit. All components were there & as described. What i wasn't expecting was what wasn't mentioned in the listing - a rather nice extruded aluminium case to house it in :) I used to work in the electronics industry & i was very surprised at the PCB quality, it's very good indeed. Thick double layer fibreglass PCB with through hole plating & gold flashing, as good as you'll get in other words.


Oh by the way, welcome to the site & enjoy :wave:

[Paul]

Well we are here to give you ideas ;)

Here are amplifiers in various states from pre-populated PCBs to just the PCB itself or a kit of parts (http://www.signaltransfer.freeuk.com/) :)

These amplifiers were designed by a chap called Douglas Self, who knows a thing or two about audio. I can't say i have listened to any myself but he has taken a bog standard generic class B amp & gone to town on it to get distortion as low as possible.

If i was going to buy one (sorry, a pair :lol:) it'd have to be the Trimodal amps, this way you get class A when you want it just by flicking a switch even while the amp is powered up :eyebrows:

If you are interested the same people are selling on ebay & at the very same prices (http://shop.ebay.co.uk/audioginge/m.html?_nkw=&_armrs=1&_from=&_ipg=&_trksid=p3686) :)

I happened to recently purchase one of the balanced output RIAA phono pre amps from this chap & it arrived in 3 days as a kit. All components were there & as described. What i wasn't expecting was what wasn't mentioned in the listing - a rather nice extruded aluminium case to house it in :) I used to work in the electronics industry & i was very surprised at the PCB quality, it's very good indeed. Thick double layer fibreglass PCB with through hole plating & gold flashing, as good as you'll get in other words.


Oh by the way, welcome to the site & enjoy :wave:

Oh my , now you talking .
I like the look of that kit and its pricing, I take it I'l need to buy a power supply and heatsink plus case to fit it all into?
Is it a mono block or stereo?
Has anyone got / heard one of these?
Will it be ok with a 4ohm load?
What sort of voltage would be required to get approx 50w /channel?
What sort of power supply would be best

Thanks
Paul

[john blackburn]

Hi Paul.

Take look here http://myweb.tiscali.co.uk/nuukspot/decdun/

And here http://sound.westhost.com/projects.htm

The ESP designs are very well respected and the site has a huge amount of information as does Decibel Dungeon.

John

[Paul]

Thanks John ,
they both look like they may have some good info,lots of reading to be done!
Paul

[Reid Malenfant]

I like the look of that kit and its pricing, I take it I'l need to buy a power supply and heatsink plus case to fit it all into?
Is it a mono block or stereo?
Has anyone got / heard one of these?
Will it be ok with a 4ohm load?
What sort of voltage would be required to get approx 50w /channel?
What sort of power supply would be best

Thanks
Paul
No problem Paul. Just don't rush in to anything! To answer your questions in order:-

Yes you'll need a power supply or supplies if you fancy dual mono supplies (better stereo seperation), heatsinking to cater for the amp/s & a case/s.

The amplifiers are supplied individually, you could make monoblocks with a seperate PSU (power supply unit) or put them in one case & use one PSU that's big enough for both.

I haven't heard one, however you listen to something similar but more compromised (or should i say less developed) in virtually every generic class B amp made for the last 20 years. I know the circuit & it's well thought out. It just depends if you are in the school of thought that global feedback can cure things & good design avoids problems. Personally i prefer less global feedback but more local feedback to sort things out. If you like Naim you will probably like these ;)

4 ohm load is no problem for these amps, the load invariant amp is designed to drive a 2 ohm load with the minimum increase of distortion, any of the others will also drive 2 ohm, but with a tad more distortion.

50W channel (8 ohm) will require a PSU of about +/- 35V with an unspectacular PSU.

Best PSU would be hefty toroidal transformers with hefty capacitors, the PSU is the engine after all. Give it an oversized PSU & it'll breeze any music & impedance variations in your loudspeakers. If it was me i'd use at least 250VA transformers per amp with 22,000uf capacitors per rail. This wouldn't be too expensive as the rail voltage would be fairly low.


Hope that helps :)

[Ali Tait]

Can't disagree with Mark's suggestion,but I think you could get an as good or better sounding Tripath amp for less money.Try buying one of the many very cheap Tripath amps on ebay to see if you like what they do.If yes,spend a bit more on a diy version.Dead easy to do,the pcb's have labelled connectors for the power supply and audio out etc.

[Reid Malenfant]

:) I can't fault Alis' suggestion either :lol:

In all honesty the Tripath will be a much cheaper option, but you can't flick a switch to make the thing class A ;)

In reality the Trimodal amp is only designed to be a low power amp like the Tripath @ about 20W RMS channel into 8 ohms. It depends on what you want, & how much you are willing to spend in not only time but £££ as well. It could be modified to accept extra output transistors so it would be capable of 50W RMS 8 ohm class A but you'll need some monster heatsinks! Dissipation would be about 150W per channel doing nothing! As you increase the volume some of that power would be fed to the speakers & the amp would actually run cooler :)

Perfect excuse that...Officer i have to have it loud to stop my amp blowing up :lolsign:

I'd love to get to listen to a Tripath Class T amp, they are rather ingenious variable frequency class D amps that use a switching frequency of up to 1.5MHz at low power & gradually revert to a more conventional class D amp with a lower switching frequency at higher volume levels.

[Ali Tait]

Not all low power,for instance the TA2022 chip in the Hlly T-amp 90 will give,yes you guessed it,90w into 4 ohms and about 30 or so into 8.A great sounding amp for 158 quid delivered.But,you're right,no class A,though I found this particular chip to have quite a valve-like sound.

[Techno Commander]

Seeing the Rod Elliots site mentioned reminds me of an unfinished (unstarted:)) project.
I have a set of his DOZ (http://sound.westhost.com/project36.htm) class A amp boards and the necessary transistors. As well as the matching pre amp (http://sound.westhost.com/project37.htm) and power supply boards. I think a few components have been soldered on the pre board. If you are interested, they would be cheap.

[Paul]

Not all low power,for instance the TA2022 chip in the Hlly T-amp 90 will give,yes you guessed it,90w into 4 ohms and about 30 or so into 8.A great sounding amp for 158 quid delivered.But,you're right,no class A,though I found this particular chip to have quite a valve-like sound.

Nice idea , I take it you mean this one http://cgi.ebay.co.uk/HLLY-TAMP-90-90W-Class-T-AMP-AMPLIFIER-Tripath-TA2022-/260505669141?cmd=ViewItem&pt=UK_AudioTVElectronics_HomeAudioHiFi_Amplifiers&hash=item3ca7590e15

Techno Commander
I wouldn't need the pre amp as I want to use my TC7520 as a pre ,or would I ?
what else would I need to complete the amp and how much?

thanks for all the input
Paul

[Ali Tait]

Yes that's the one.Don't let the low price put you off,it's a very good amp,though if you wanted to diy you could buy some boards using the same chip.

[Paul]

Yes that's the one.Don't let the low price put you off,it's a very good amp,though if you wanted to diy you could buy some boards using the same chip.

Or maybe modify that one if I liked it ?

Can someone explain the difference between T ,D , B , AB and A class please.

thanks
Paul

[Reid Malenfant]

Can someone explain the difference between T ,D , B , AB and A class please.
I'll try.

Class A:- The output transistors are always switched on & to a point where all the current that the loudspeaker will ever require is already being dissipated by the output transistors. Thus they never need to turn on more current & only swing a voltage. This results in a very low distortion amplifier.

Class AB:- The output transistors are turned on so that some current is flowing accross the output stage. This may be a few hundred milliamps or more & will result in class A operation up to possibly a few Watts of power. Above this the transistor supplying say the positive output current will need to turn on harder & as it does this the transistor connected to the negative rail will gradually lower it's cuirrent until it all of a sudden switches off. This switching creates a distortion known as "crossover distortion".

Class B:- The transistors are just turned on & flow a small current, this is adjusted to create the least amount of distortion & is usually about 25ma per transistor pair. You'll still get crossover distortion but if designed as well as say the AB, the B will distort slightly less.

Class D:- This involves switching the output transistors (usually mosfets) on & off at a very high frequency from rail to rail. This is probably done at frequencies approaching 500KHz. The output transistors are modulated in such a way as to create a waveform that resembles the input to the amp but in time not voltage. You see the output is going rail to rail at 500000 times a second so a high voltage will appear as a wide pulse & a low voltage a narrow pulse. The output from this is fed to a low pass filter which removes the 500KHz fundamental & the reconstructed audio comes out of the filter.

Class T:- Similar to class D with the exception that at low power the switching frequency is increased into the MHz region to increase linearity. As the power output is increased it'll revert back to a lower switching frequency as this is more efficient (switching takes time & there are losses in the mosfet switches).

Hope that helps :)

[Techno Commander]

Paul,

I just dug the boards out. It would appear that the pre amp is complete apart from the capacitiors and the pre amp PSU is finished. I used Panasonic resevoir caps which are a bit bigger than the standard caps in the BOM and these sit proud of the PCB by a couple of mm.

The DOZ boards cost approx £15 (plus postage) and the pre amp board & PSU are approx £12 (plus postage). The output transistors are £7.40 each from RS.
If you are interesrted, you can have everything for £35 posted RMSD.

http://i246.photobucket.com/albums/gg116/sillystuff99/sale/DOZ.jpg

Currently, I cannot find the BOM & construction details, so I have e-mailed Rod for duplicates. I therefore wouldnt post them until I had all the necessary paperwork to include with them.

[Paul]

Thanks Andy
Let me know when you get all the pieces together and we'll sort out payment details, looks like I have my first progect!

that doesn't mean to say I'm not going to try something else too.
Thanks
Paul :)