[kelly]

Quote:

Originally posted by KR... From all the reviews that I have read, Wadia has always made the best cd players. Head-Fi is suppose to review their top of the line CD Player (not the transport/dac combo) sometime is summer. Who gets to review this one? Maybe the person can get a blockhead loan for the review, if they have enough posts.

I think the 861 has the new output stage. It should be an awesome player, maybe better in some ways than the 270/27ix. Of course, it's like $8000. *grumble*

 

[Audio-Me]

nt

 

[Audio-Me]

nt

 

[Audio-Me]

nt

 

[Duncan]

Quote:

Originally posted by kelly I agree mostly with A&M's sentiment that source is more important than people on HeadFi make it out to be. There's more than a couple of over-the-top amps plugged into sub-$500 CD players on this forum. But really it's a matter of where your prirorities are.

Yes I'm behind you 110% Kelly, whilst not saying that my source is anywhere as good as others have here - it is head and shoulders over what it was (sonically) when I had the player on its own...

You can only get out what you put in...

 

[Audio-Me]

I'd like to point out that I was the bald guy wearing white long sleeved dress shirt. Yah, I didn't have the HeadRoom shirt on; I brought it with me but it was too hot that day to wear a heavy black shirt.

Although I let Dan handle most of the Etymotic stuff, I did talk to some of you guys, and hopefully you all didn't think I did too terrible as a volunteer. Again, props to Tyll for doing such a kick ass service to the community. Rock on!

 

[morsel]

It is important realize that the meta42 is a board with vast potential for variation in configuration, component quality, assembly quality, case size, and style. Reviews of meta42 amps are _meaningless_ unless the configuration is stated in great detail. A good meta42 configuration should compare to amps costing 2-3 thousand dollars. A poor configuration, well, all bets are off.

Was it a real version 1.0 meta42 board, an earlier prototype, or a space oddity board that eric made a few months ago? Did it use the best opamps available such as the AD8610 or did it use lesser opamps that don't sound as good? Did it use the FET cascode current source available only on the production board and final prototypes to bias the opamp into class A operation? How good and how big are the input, power supply, and reservoir capacitors? Are the buffers single or stacked? Are they EL2001 or EL2002? Resistor values can also significantly alter the performance of the amp. We are still experimenting to determine optimal and/or reasonable values.

So you see, it is a very custom, personal amp, dependent on what components go into it and who builds it for you.

 

[Audio-Me]

It's a yellow PCB, uses AD8610, single EL2001 per channel, BUF634 as ground, there appears to be two small caps (mini wimas?) near the opamp, then there are two large wima caps (1,0 uF MKP 10), two large elna cerafines (25v 470uF) and a single smaller cerafine (25v 47uF). I see a place in the board that says XFEED with some soldering marks, cool its got internal crossfeed!? The amp does indeed look high quality.

And I believe you are correct in that it competes with $2-3k amps.

So, does the new board in Class A operation with dual el2001 indeed improve the sound? (for use with Sennheiser HD600). And can even bigger cerafine caps fit and improve the sound? Like say 2200uf? (The case size isn't really a problem) If so, then let the upgrades pour in!

 

[kelly]

Quote:

Originally posted by morsel A good meta42 configuration should compare to amps costing 2-3 thousand dollars. A poor configuration, well, all bets are off.

Of course you know--this is a very lofty claim. Is what you consider a good implementation documented somewhere? I'd really like to see the details. I have a pretty good idea of what A&M's amp is made up of and what he says it sounds like. Show me more on the full blown version.

 

[Audio-Me]

kelly, mine will be full blown soon enough.

(well it won't be dual monoblock since I'm guessing that's what you are interested in about) Mine still needs to be able to fit in a large backpack as it will be used as a travel amp.

 

[tangent]

Quote:

It's a yellow PCB, uses AD8610, single EL2001 per channel, BUF634 as ground, there appears to be two small caps (mini wimas?) near the opamp, then there are two large wima caps (1,0 uF MKP 10), two large elna cerafines (25v 470uF) and a single smaller cerafine (25v 47uF). I see a place in the board that says XFEED with some soldering marks, cool its got internal crossfeed!?

That's a revision I prototype from late March or early April. It's not actually a "META42"; you could call it an ETA42, since it was made before Morsel got seriously involved. (AFAIK, her only contribution to that revision is the use of the TLE2426.) What that board is missing relative to the v1.0 version, ignoring things like size and layout issues:

1. Multiloop topology. Revision I allowed local or simple global feedbacj, Eric probably used global feedback which means...

2. ...that the board's crossfeed pads won't work. They will only work when you configure the amp for local feedback only, in which case you get errors from the buffer creeping into the sound. That's why there isn't a specific set of crossfeed pads on the final META42 -- the idea is that you just put it "in front" of the amp section. I've built a few META42s with that layout, and it works well.

3. Provision for output resistors, should you care.

4. Virtual ground buffer is another EL2001, for lower power supply ripple vs. using a BUF634.

5. We ditched the power supply "stability" cap -- the 47uF Cerafine on your board. Morsel deemed it too silly to live.

6. Several small tweaks.


To touch on a few other topics raised in this thread:


Does the META42 compare well to $2-3K amps? I have no idea, since I've never heard such a thing.


Regarding interference: I've tested the final META42 pretty hard for this. I won't guarantee that the META42 can't be interfered with, but I certainly wouldn't say it's "easy" to get interference with it, either. The ETA42 does favor wiring simplicity to layout tightness; the META42 takes the opposite tack, so there are no layer changes or vias, and the traces are all a lot shorter. Perhaps this explains the interference Eric found with that board.

There's another possibility, if Eric used an ALPS Blue Velvet pot: these pots have to be case-grounded to avoid adding noise, in my limited experience. The META42 board has a provision for this: the PG pad. (Pot Ground) If you use a metal case, you get case grounding for free -- if you use a plastic case, you need to ground the pot to the board.

 

[Audio-Me]

tangent, I plan on upgrading the "ETA42" later on. Do you deem it wise to switch to the final board? Will the sound indeed be better? Lol, so the decoupling cap is really unnecessary? Have you done a before and after? I like the idea of another EL2001 instead of the BUF634, I have no idea why, except that it matches, hehe. I don't want/need the internal battery support anymore, but I'd still like to use a battery pack every once in a while. (two parallel pairs of 9V in series). Since eric said he'll be using a case that's the same as the one I have now but twice as wide, could I use bigger cerafine caps? Say 2200uf or something? Or could that actually have an adverse effect (or unfavorable to my preferences) on the sound, or not even possible to run off battery pack? Mine uses the Alps blue pot, I'd like to change it to the TKD stepped attenuator.

 

[tangent]

Quote:

Do you deem it wise to switch to the final board?

I'll have to let Eric answer that one definitively, since he's the only one who's used both boards. The META42 is indeed a superior board, as I've described. Would it be worth ripping your old board out and using a new one? I dunno -- personally I'd just build a new amp around the better board, but then, I'm a builder, not a buyer.

I guess it depends on how much it costs, which depends on whether you do it yourself or get someone else to do it for you.

By the way, I forgot to mention the current source in my list of improvements. ppl says this makes the 8610 sound even better.

Quote:

so the decoupling cap is really unnecessary?

If you're talking about the small cap across the power rails, then yes -- properly configured, the META42 board has only insignificant amounts of ripple on the rails, even under extreme conditions. It doesn't need any more stability.

I didn't test with and without this cap. Instead, I discovered that I could do without it when I built the EL2001-based power supply to test against a BUF634-based one. Since we needed the board space, that cap got nuked. I suppose it might help if you have small main power caps, but that's not a problem any META42 builder should face.

Quote:

could I use bigger cerafine caps?

That's probably the ETA42's only advantage: it has a huge amount of space for power caps. The META42 will only allow 4x220uF in Cerafines. You could put the bigger caps out-board, but personally I wouldn't do it. I'd rather use high-capacitance generics. Then if there's a speed problem, I would parallel them with 10uF Wima MKS2 film caps, which we designed the META42 board to accept. This gets you a good combination of speed and compactness. I don't regret making that tradeoff at all, since the META42 is designed to be portable.

 

[Audio-Me]

The new board seems interesting. I mean bigger caps as in higher capacitance. Hrm, mine has 2 x 470uf, wonder how 4 x 220uf sounds in comparison? I will definately have to go over this with eric, he'll be able to do A/B testing when I send it back to him.

 

[lextek]

Does anbody sell these META amps or is just a DIY?