First DIY project?

Hi all, i've just recently discoverd an intrest in hifi and im almost done buying my first system. Since my friends father has a nice home made preamp and tube power amp i figured that i should give this DIY thing a try and build my own power amplifier, just for fun and learning more about how it all works. Therefor i got myself a pre and power combination for my system, so that i could test the amp im going to build and hopefully the many many more amps im going to build (the amplifier i bought is a Sugden AU41 pre and a Sugden A21-a power amp).

Well to cut to the chase, what amplifier is best to start out with? it shouldn't be all to complicated since it will be my first. i've been looking alot at passlabs ZEN and SOZ, mostly the ZEN since it isn't balanced (my preamp doesnt have a balanced output). if someone knows a better amp to start out with please do tell me, either on this forum or by mailing me at: [email protected]

Thanks, Pontus Fyhr
 
I can't recomend any single power amplifier project to start with. I can, however, provide some general guidelines for selection.

1. Choose a project where the PCB can be purchased. PCB layout is more of an art, then a science. Most of the available boards have been around for a few years, and work fairly well.

2. Pick a low to medium power amplifier. The voltages and currents involved in a high-power amplifier aren't something you want to have to deal with in your first project.

3. Don't pick an esoteric design. There are many amplifier designs out there that are VERY complex (Borbely comes to mind here), or use hard-to-find parts. These should probably be avoided as a first project.

4. Select one that's within your budget. There are few things that are more discouraging than having an almost complete project that only needs a few parts, and having it sitting around for a few months while you save up for those parts. In some cases, it's enough to cause the project to be dumped.

Good luck.
 
Good starter project

My first amplifier was the JLH design - i wired everything off a tag strip and it worked first time!

The design has been updated and a PCB is now available. It is simple, uses low voltages (i.e it's safe), can be built cheaply and sounds like you've spent 10 times as much - the downside is the output power of about 15 watts.

A website dedicated to the amplifier is;

http://www.gmweb.btinternet.co.uk/index.htm

It's aguably the best start you could make!
 
Great feedback thanks!

Thanks for all the replies, im taking a look at the JLH right now. I really must say that the ZEN seems very suitable, it doesn't contain all that many parts and the passlabs site provides both a good circut layout, a board design (though it looks a bit odd), and parts layout.
I think ill go for thisone, not that its the cheapest one to build atleast not for me. Beeing a seventeenyearold student my budget is limited, but it goes far enough to spend 100$ on a diy project (heatsinking not included, yikes). I'll post my final desicion and result when im done :p

Pontus
 

paulb

Member
2001-06-01 4:53 pm
Calgary
Fyhr,
If you're on a limited budget, watch out for the costs of the power supply. Class A amps like the Zen, SOZ, or DLH are less efficient and require more power than the equivalent class AB (There's a Forum on Class A vs. AB here somewhere). I am also told that Class A are more prone to noise from the power supply, so you need bigger capacitors (more money). Transformer, caps, and heatsinks (and maybe the case) are most of the cost in a Class A amp.
Power supplies are also more complicated than they appear.
 
Fyhr,
As far as supply problems in Sweden, I'm not sure where to direct you; Petter is using IRF parts (I think) in his X-amp experiments. Being closer to your part of the world, he may be able to direct you to sources for IRF parts in northern Europe. At least as far as North America is concerned (as of ten minutes ago...) Digikey was showing stock for the IRFP140, IRFP9140, and IRFP9240, depending on which version of the Zen you want to build. Other suppliers, such as Newark, also stock IRF parts. For what it's worth, I've found Newark a bit of a nuisance to deal with, so don't take that as a recommendation.
If you want to substitute parts, go to the IRF website: http://www.irf.com and look up the specs on the parts you want to replace, then look for another part with a different case, but the same specs. There's plenty of lattitude in Nelson's design, so don't be afraid to substitute parts if you want--just make sure to keep heat dissipation and voltage & current ratings in mind.

Grey
 
WRT MOSFETs for a ZEN amplifier, Nelson Pass did some tests will similar MOSFETs (IRF040, 140 and 240), and found that the lower voltage version (040) created lower distortion (see http://www.passlabs.com/projects/znret_4.htm). I'm not sure what reason he gave (if he did), but I think the reason is lower input capacitance.

Also, I can't remember who did the testing, but I seem to recall someone finding that MOSFETs with higher transconductance (sometimes called Forward Transfer Admittance on the spec. sheets) will lower distortion in a ZEN.

Finally, the IRF9140 is the current source. It has little effect on the sound. You should be able to substitute almost any high-power P-Channel MOSFET. Watch the pinout.

You might want to keep this information in mind when you select your MOSFETs. With all the new MOSFETs out there, you might be able to find some that are even better that the IRF040.

According to what I've seen, the ZEN is probably a good amplifier for your first Class-A. By all reports (I've never built one), the amp sounds good (necessary for a first project). Overall, it's fairly simple to construct, with fairly few components. This amp doesn't deal with lethal voltages, and the currents aren't too bad, for a Class-A. The latest version (ZEN Revisited) has a PCB layout (someone might even sell the PCB; I've never checked). Getting good heatsinks, and a heavy enough transformer might be a little expensive, but it's still not too bad.

The one item it's missing (along with >90% of DIY schematics) is safety features (Overcurrent Protection, DC Output Protection, Temperature Sensor and Speaker Turn-on Delay).

Overcurrent protection could be as simple as a fuse in the power rail (actually, that's the only place I see to put it). All of the rest can operate by opening a relay in the speaker line. This is a minimal invasion of the circuit path (assuming you pick a good relay), considering what it may save.
 
Pontus,

Watch out for the difference in the Power Dissipation of the device you finally choose to use. Pd rating should not be exceeded. Being your first project, get some local help in thermal management and have on hand fairly low value but high wattage resistors to slowly discharge the huge capacitor bank. Inexperience in these areas could be highly dangerous.

Although this might be too late a post, a medium power class A/B amplifier might be a good choice for a first-timer.

Anyhow, all the best.
 
agree with Paulb on powersupply $$

Pontus,

I can confirm PaulB's and Samuel's remark about the power-supply.
I've kept a log of money spent and give a breakdown:

for one channel:
amp components + heatsink: 35 EUR
I got a chance to select matched pairs from a tray in a shop myself.
heatsinking once-off price: I got out the last 4 from the shop, next one will cost me around 40 EUR.

ps components+ hs: 140 EUR
transformer and capacitors are 50% of that money.

I've had my pcb's made by a factory: 40 EUR for 1 amp+ 1 ps board..

Gold-plated terminals, case, wiring, nuts&bots, mains plug etc :
around 100 EUR.

AND around 10 EUR in 'replacement' stuff, I smoked some transistors/voltage regulators in the process.

So, yep the ps is expensive.

Succes
Jos
 
An other complication is to convince the electronic sales man to sale you the part (very disapointing, I agree)

He don't believe that a little amp of 30 W (the Aleph3 but he does'nt know it) need so many caps. He simply refuse to sale the caps filtor, it's the reverse world. And in my region (Rouen, France) it's hard to find surplus parts.

I stay in expectative...