[andrzejpw]

How much would a middle of the road meta42 cost to build? I don't need battery power. Just a wall wart. . .

I don't want boutique caps. Just standard stuff. Not the cheapest stuff either though. . .

 

[Nezer]

Talk to Erix about the power caps. Get some Cerafines as they aren't THAT expensive (a few bucks at most for all you'll need). Yes, they do make that big a difference in the sound IMHO. Percentage wise they are probably about double what cheap caps run but the total difference is only going to be a few bucks. Certainly nothing anyone is going to flip over. If your dad freaks out still, ask him why he prefers titanium clubs. These caps are about the equalivent in the audio world. A little more money, but subtle they are not.

Follow the parts list on Tangent's page as a guide. Use the Panasonic film caps he recommends if you can't buy the Wimas.

Use a decent but inexpensive opamp. Again, Tangent reviews several on his site.

The power supply is going to be the toughy. I doubt your flks will let you spring on an expensive medical-grade linear regulated wall-wart so go with a decent HF switching wart. Just make damned sure the switching frequency is well outside of listening range! Again, Tangent comments on this on his site.

As for resistors, get some 1% metal film resistors. You could save some money if youre really patient and get som 5% resistors and buy a LOT more than you really need and match them with a meter. Or you can just buy what you need and pay a bit more for the 1% rather than spending more buying 10x what you need and matching.

The only place matching is critical is between channels. If the specs call for 100 ohms and your running 95 or 105 instead, no big deal, but if on one channel you are running 95 and the other 105... then it IS a big deal as the channels will be unbalanced.

Avoid getting the cheap irons from radio shack as people have reported problems with the tips wearing out REALLY fast. you want a pencil and NOT a gun. Also try and spring for Eucetic solder preferably with some silver in it. It's a small thing but all the little things add-up and can mean big differences in the end.

Good luck and happy building.

 

[ppl]

Do Not use a switching power supply on this Amp. A great part of the power-supply design is implimented so as to give a Cleen Analog Powersupply and not contaminate the Power to this unit with Digital Grunge an any frequency. A modest unregulated wall wart i asure you will sound alot better that an expensive lab grage switching supply.

The perfered way to go AC only is to use a good Split rail Bipolar or what ever you wish to call a supply with both a Positive as well as a negitive Voltage referenced to ground. Do not use the EL-2001 and the TLE-2426 Rail Splitters you will not need them and if your outboard supply is not exactly split in half and most are not the Virtual ground will overheat trying to balance the rails.

 

[tangent]

Quote:

How much would a middle of the road meta42 cost to build?

The parts are about $50 for a minimum configuration, and like everything in audio, it can go way up from there.

Quote:

You could save some money if youre really patient and get som 5% resistors and buy a LOT more than you really need and match them with a meter.

Why bother? You can get MFRs in 5-packs from DigiKey for 54 cents apiece. You'll need about 8 values, and you won't need more than 5 of anything, so you're out $4.32. Or, you can buy Vishay Dales one at a time from Mouser for 16 cents apiece. There are 21 resistors on the META42 board, so that's $3.36.

It's not worth cheesing out on resistors.

That said, I still hand-match resistors even when using MFRs. It's a hedge against getting a mislabeled/mispackaged resistor, and it removes one more possible source of suboptimal sound. It's quick and easy, so why not do it?

Quote:

try and spring for Eucetic solder preferably with some silver in it.

If it has silver in it, it's isn't eutectic (note spelling) any more -- only plain 63/37 is eutectic. Whether silver helps or not, I cannot say.

Quote:

A great part of the power-supply design is implimented so as to give a Cleen Analog Powersupply and not contaminate the Power to this unit with Digital Grunge an any frequency.

It's true that the META42 has no power supply filtering to speak of, aside from the main power caps -- no linear regulators, etc. However, I also wonder how much it matters for switching power supply noise to get into the amp. But hold this train of thought for now, because I will be doing some measurements on this issue in about a week. I'll know more then.

If you do go with an unregulated wall wart, andrzejpw, spec your power caps to be able to tolerate a 15% or so overload, since any surges on the house power will be sent straight through the power supply and into the amp. That is, if you use a 15V power supply, spec your power caps as though you were using an 18V power supply. Also take into account the fact that many power supplies are already a bit "hot" -- they're spec'ed to supply a certain voltage at a certain current level, and at lower current levels the voltage drifts upward. That 15V power supply might be providing 17V with a low current load a like headphone amplifier, and so you would want to plan for about 20V.

 

[fyleow]

How does the sound of the Meta 42 compare to the CMOY? I'm using the OPA2132P in my CMOY right now...I assume that if I make the Meta 42 using the same Opamp it will just sound the same or really close to it?

How do the Analog Devices Opamps stack up to the OPA2132P?

 

[tangent]

Quote:

How does the sound of the Meta 42 compare to the CMOY?

They're not even related, sound-wise. I know this will sound like hype, but the META42 sounds better in all respects than a CMoy amp. I'm not saying that no one should ever build a CMoy amp again -- they have plenty of virtues (size, simplicity, cost...) But if you have the extra money and can stand the extra complexity and case size, I think you'll be much happier with this amp than a CMoy.

Quote:

I assume that if I make the Meta 42 using the same Opamp it will just sound the same or really close to it?

No, the META42 will make any op-amp sound better, for several reasons:

1. There's a better power supply driving the op-amp. This means that the chip will be less likely to clip at low supply voltages, it will have more instantaneous current available, etc.

2. The op-amp is buffered by the EL2001, so it only has to do voltage gain. The reactive headphone load is handled by the buffer

3. Distortions are lower due to the multiloop topology.

4. The class A feature may improve the sound of the chip some. I haven't tried it with an OPA132/134 chip yet, but it's possible.

Quote:

How do the Analog Devices Opamps stack up to the OPA2132P?

See my reviews for my opinions on the subject and links to threads here and at Headwize that have other views. Those tests are all done with CMoy amps, but the META42 doesn't change the overall character of the op-amp chip, it just relieves the chip of some of the burdens it must shoulder in the CMoy design, so that it sounds its best. The reviews are still relevant to the META42, except that issues like output current aren't an issue with the META42 like they are with a CMoy. For example, I describe the AD823 as a little weak in a CMoy amp, but in a META42, it's a fine little chip.

 

[fyleow]

Hmm I just finished my CMOY perhaps I will build a Meta42. Quick question though, if I want to make a "high end" Meta42 can I use the OPA627? I don't think it's possible because of the high power requirements?

 

[tangent]

Quote:

if I want to make a "high end" Meta42 can I use the OPA627? I don't think it's possible because of the high power requirements?

Ummmmm.... I haven't a clue what you're referring to. Any chip that will work in a CMoy amp will work in a META42. The OPA627 will require an adapter to work in the META42, but that applies to any single-channel op-amp.

 

[fyleow]

Quote:

The downside is that the AD843 requires substantially the same amount of voltage as the OPA627: I was unable to get it to avoid nasty distortion below 11V. In the worst case, the AD843 required 12V to get rid of the last of the distortion. In the best case, the OPA627 can operate down nearly to 8V before succumbing to easily-audible distortion.

I was referring to that...

Does that mean it just needs more power? Like another 9V battery to be part of the power supply?

 

[andrzejpw]

are there any power supplies on headwize that would fit the bill here?

Also, which op amp should I be using? I've read your reviews, and if I find a way of getting 627s cheaply. . .

would those be a good choice? Or should I go for something from AD?

I noticed audio&me's is using 8610s. How are those?

 

[finleyville]

andrzejpw,

Finleyville here. I am making out a META42 parts list right now and will be ordering sometime soon. If you want to double up on our orders to save shipping money since you live across town, that would be cool. I plan on using Dale-vishey resistors, Cerafine and Orange Drop caps, the fake Alps blue stepped pot (I will have an extra if you want it), and the AD8620. (the dual version of the 8610). The only problem I'm having is finding a decent, affordable power supply that would work with the AD8620 and the TLE2426 voltage divider. I was trying only to order from mouser, but their min order of the tle2426 is 100 pcs. PM me and we will talk about it.

Oh yeah, if anybody has an extra TLE2624, I'll take it.

 

[mkyy]

finleyville, I think you can order tle2426 by piece from digikey.

 

[JMT]

Quote:

but their min order of the tle2426 is 100 pcs

Check Digikey, they have no minimum for those parts.

 

[finleyville]

I figured that out. I just didn't want to order from two different places: Mouser for the Dale resistors, and Digikey for the rail splitter. I guess I'm too cheap to pay S&H to two different places.

 

[JMT]

Welcome to the world of Parts Searching. I was up ordering last night and now am expecting packages from: Digikey, Newark, Mouser, and Allied Electronics.

I think I am into this because I'm addicted to getting packages.