[GirgleMirt]

Finally ordering the parts for a meta42

I have a question on the case though. I've seen the Hammond 1455 mentionned more than a few times, and it looks like a very nice case, but in the pictures I've seen of built metas with it, it seems to open on top. But on the hammond website, from what I can see on the pictures, it dosen't seem to open on top?!

also, size:
Length (Inches): 4.72 Width: 4.06 Height: 2.09

is that a good size for meta42 with crossfeed? Thinking black, version 2. Comments/suggestions?

thanks!

 

[JMT]

The cover slides off after you remove either the front or rear panel.

 

[fiddler]

The Hammond datasheets say the "bottom" slides off, but as JMT said... almost everybody uses it as a lid instead.

 

[GirgleMirt]

cool, thanks

Didn't look like it opened.. (from the picture)

Ordered the parts from Tangent! But I have a few more questions, or actually, here's what I have now for settings :

Gain ~12 (planning to use Crossfeed with Grados are possibly other future headphones..)

OPA 2132PA [edit]Its a AD8620 actually
C1: 0.22 uF prolypropylene film & foil, 50V
C2/C3: Four 220uF 35V
C4: Wima MKS-2 6.8µF/50V (2)
C5: unpopulated
clear blue led 4.9V, 2-5 mA
6 Elantec EL2001CN buffers (stacks of 2)
50k panasonic volume pot
Elpac WM080, 24V, 033A, 8W Power Supply

r1: 1K
r2: 500K (10 times the 50k panasonic volume pot)
r3: 1K
r4: 11K
r5: 4.99K
r6: 845K
r7: 100
r8: --
r9: --
r10: --

1) Do those resistance value look OK?

2) 1% Metal Film Resistances, does the type actually matter? I'm puzzled by brand & power, Yageo have 1/4W and seem the cheapest of the resistors available at digi-key, BC Components are more expensive and have 0.4W or 0.6W, does that make a difference in the amp? I mean, change the sound or anything? I'm planning to get the BC Comps 0.4W just to be sure... Or actually, is it a bad idea? (they're a bit more expensive so I figured they might do the job a bit better?)

3) Wires and solder: After hearing how interconnects, cables affect the sound, and seeing how I'll be adding crossfeed (many wires), should I be worried about the type of solder and wires I use? If so, anything from digi-key or mouser you'd recommend?

4) Crossfeed switches: The article 2 mentions DPDT switches, I guess I need one with 3 positions? On-On-On, right? (Since 1 switch has High cross. Common and Low cross. and the other has Enable, Common and Bypass) looking at the mouser catalog, that seems to leave only one choice! The others have on-off-on, that wouldn't work, correct?

thanks a lot!!!

 

[fiddler]

About the switches, you need two 2-pole, 2-throw switches... one to enable crossfeed, and one to switch between high and low. Tangent's board is designed in a way that makes it easy to use this switch config. If you want stick with one switch, you'd have to get a rotary switch just as Tangent describes in his article, or stick with just one crossfeed level. Your gain is a bit high perhaps for Grados, but I suppose if you need it to work with other headphones in the future, it might be a good idea to set it a bit high as you have.

 

[JMT]

Quote:

OPA 2132PA

I'd personally go with an AD8620, or at the very least the AD823.
Quote:

C2/C3: Four 220uF 35V

Bump those up to 470µF/25v Panasonic FC's
Quote:

6 Elantec EL2001CN buffers (stacks of 2)

So you are planning to stack the VG buffer too?
Quote:

3) Wires and solder: After hearing how interconnects, cables affect the sound, and seeing how I'll be adding crossfeed (many wires), should I be worried about the type of solder and wires I use? If so, anything from digi-key or mouser you'd recommend?

I personally use Kester "44" 63/37 solder. It is easy to find and is easy to use. As far as hook-up wire, think about ordering some Belden 22awg silver tinned teflon coated wire. You can order it from Handmade Electronics. It's good wire to use in the signal path, and because it's stranded, it is easy to route without breaking.

 

[GirgleMirt]

Quote:

Your gain is a bit high perhaps for Grados, but I suppose if you need it to work with other headphones in the future, it might be a good idea to set it a bit high as you have.

#1, checked!

#4 Quote:

About the switches, you need two 2-pole, 2-throw switches

Ah ok I think I get it, the pad and the switchs are 2 different possible configurations? Hmmm.. maybe not, a bit confused about that part:

Quote:

Pad Function If you use a standard DPDT toggle switch, the pad functions will line up so that you can put a "rainbow" of wires between the switch's solder lugs and the pads on the board. That is, the bottom-most lugs on the switch will be wired to the pads at the edge of the board, the top lugs to the pads farthest from the edge, and the middle lugs to the pads in between. See below for a picture showing this arrangement. The functions on S1 are High crossfeed, Common, and Low crossfeed. The functions on S2 are Enable, Common, and Bypass.

so with the 2 switch config, you basically get On/Off High/Low or you can use a DPDT toggle switch for the 'pad function' (whats a pad?!) and get a Enabled/Common/Bypass (basically On/dunnoWhatCommonIs/Off) and a High/Medium/Low crossfeed setting??

 

[JMT]

Quote:

so with the 2 switch config, you basically get On/Off High/Low or you can use a DPDT toggle switch for the 'pad function' (whats a pad?!) and get a Enabled/Common/Bypass (basically On/dunnoWhatCommonIs/Off) and a High/Medium/Low crossfeed setting??

1. A "pad" is the area on the board where you land and solder the wires.
2. Simply put, you will have two DPDT switches. Both switches need to be "on/on" meaning that when the bat is thrown one way, the center pole is still in contact. That is the "common" pole.

 

[GirgleMirt]

Almost simultaneous post JMT!

Quote:

I'd personally go with an AD8620, or at the very least the AD823.

Ooops.. I was looking at other opamps and got mixed up! I'm getting an AD8620 from tangent.

sorry about that!

Quote:

Bump those up to 470µF/25v Panasonic FC's

Really? Tangent says: "However, it may be better to have four 220 ìF capacitors than two 470 ìF capacitors, if only because it will let you get shorter capacitors or caps with higher voltage ratings. If voltage rating and part height aren't an issue, going with only two capacitors will probably save you a bit of money." Or you mean use four 470µF/25v Panasonic FC's?

Quote:

So you are planning to stack the VG buffer too?

Hmmm... I didn't really think about it... On the order parts page it said you needed 3, I just doubled that number to have stacks.

Looks like I'm gonna have an extra buffer, so might as well stack the VG too no? LOL

first amp, plz don't make too much fun about me!!

Quote:

I personally use Kester "44" 63/37 solder. It is easy to find and is easy to use. As far as hook-up wire, think about ordering some Belden 22awg silver tinned teflon coated wire. You can order it from Handmade Electronics. It's good wire to use in the signal path, and because it's stranded, it is easy to route without breaking.

#3 checked! I'll try to get those! (If the master builder uses them, they must be good!)

#4 (pad/switches) checked!

 

[tangent]

Quote:

I'm getting an AD8620

In that case, I would make R5 3.3K and R6 1M. Unless, that is, you plan on rolling slower op-amps into the amp for the heck of it. If so, make R5 4.7K and R6 470K. (4.75K and 475K are close enough.)

Quote:

Or you mean use four 470µF/25v Panasonic FC's?

Definitely he means 4 caps, if you have room. If you don't have room for 470s, at least get 4x 330uF's. 220's are minimal.

Quote:

I just doubled that number to have stacks. Looks like I'm gonna have an extra buffer, so might as well stack the VG too no? LOL

Theoretically, 2x buffers on the virtual ground should help, but I have yet to be able to detect any difference. Stacking output buffers is much more obvious an improvement. Still, I wouldn't leave the extra buffer out of the amp unless you wanted a "just in case" spare, or you were powering the amp from batteries and needed to save power.

Quote:

is that a good size for meta42 with crossfeed?

Yes, that's the size of the case you see in the pics on the crossfeed page. It's got plenty of room for this config. You could probably get away with going down to the K size case, if small size was important to you; you might have to use small caps or get creative with mounting the crossfeed board, though. Switches would also be trickier to mount on the smaller K panel.

Quote:

Gain ~12

Gain of 11 should be sufficient, and extra 10K resistors will be more useful in future projects than 11K's.

Quote:

r2: 500K

470K or 475K is close enough for this purpose, and these values will be more useful in other projects.

 

[GirgleMirt]

Thanks for all the recommendations! They've all been duly noted, getting the four 470µF/25v Panasonic FC's, gain changed to 11, R2, R5 and R6 changed

Pretty much all the extra parts are ready to order from mouser and digikey.

They have the solder at Mouser, Kester "44" 63/37, 0.025 inch diameter, 1/2 lbs. It's not much more expensive than the 1/2 pound 60-40 roll Radio Shack sells, it's better stuff, and half a pound will last me for a very long time. Indeed the Kester may last longer, because I selected a thinner wire: 0.025" vs. 0.032". (If you have deja vu tangent its because its from you from another thread

Just found it!)

Unfortunately, for the wire they have a 50$ min order, and a 16$US shipping fee for internation orders (canada)

So I'll have to get something else

So I guess I'll look locally for a similar wire.

Thanks all!