[dta116]

Here is the link:

Meta42 Pics, Description (link)

P.S. I accept criticism.

 

[JMT]

Dave, no criticism. Great work!! I especially like how you modded the Serpac to use dual 9vs for your AD843s.

My compliments!

 

[tangent]

I just looked at your page in more detail, Dave (since posting to your other thread, I mean), and it's very interesting, some of the choices you made. I hope you don't mind, but I'm going to send a link to your page to Serpac -- I think we need to see Revision B of the H-67 now.

It's a brilliant hardware hack that should be part of the standard version of the case.

It looks like you're using the Radio Shack heavy duty 9V connectors? If so, that's real encouraging -- if they fit, you've got plenty of space in there for this.

 

[dta116]

Tangent;
Thats the purpose of DIY and Free help.
If it's good for the public, I'm all for it. Go ahead and use what you can from my meger attempt to improve a simple project.

 

[geom_tol]

Great work! Your work looks very precise.
I was wondering if two 9v batteries would fit in this case, and you did it. Cool!

 

[ChenaynayC]

Very, very nice. I am very impressed you fit the two 9vs in there. I'm studying up for a meta of my own and you give me hope.

 

[blip]

Nice job

 

[puppyslugg]

dta116:

Nice work! How does it sound with the ad843?

 

[dta116]

As of now it has not yet been broken in or run for any length of time. I am still testing different variations for a lower current draw.

With the 10k pot it has plenty of range, even for my gratos.
I will put the thing in break-in mode by the weekend then will report on the findings.

I feel the AD843KN's will be superior with the stacked buffers, although I am looking at converting the TLE2426 to the dip package which should help. (this is something I need to discuss with tangent for his next board revision).

It seems easier to convert the dip package to the TO-92 than the other way around.

Tangent, are you listening?

 

[morsel]

Great job, dta! I have wondered for some time if it was possible to squeeze two 9V batteries into an H67 case. If you want to drastically reduce current draw, use an AD8620 (or two AD8610 on a Browndog adapter). If you are determined to stick with the AD843, then get rid of the cascode current source, as the AD843 is already class A. Of course that will only save you a couple mA. Going to the AD8610/20 will save you about 20mA and should be comparable sonically.

 

[morsel]

I see no point to using a DIP TLE2426 instead of the TO-92 version.

 

[HD-5000]

Anyway, great job! This is one of the cleanest META42's I've seen in the Serpac case.

 

[tangent]

Well, the DIP version of the TLE2426 is capable of better performance than the TO-92, but one of the main reasons we went with the TO-92 version was to save space relative to a pair of resistors. The DIP-8 chip would be even larger than a pair of resistors, so we're really unlikely to move to the DIP version. That would require removing features.

Face it, this is a compact amp board. It's a design choice, not a lack of ambition in design or anything like that.

 

[dta116]

I have added a small mod last night.

The original green led draws about 3ma, so I found some high intensity blue led's and replaced the green one with the blue one and used a 470K RLED resistor. It now only draws .6ma.

I an get away with such a high resistance because these lamps are extremly bright to start with. this high resistance brings the brightness down to a level thats more normal and reduces the overall current draw.

Just a small tweak, but every little bit helps with a battery powered amp.

Will do more tweaking tonite.

 

[tangent]

Another reason blue LEDs can save on current is that they tend to have high voltage drops relative to red, green and amber ones. This reduces the voltage that RLED sees, so it reduces the current level even without changing RLED's value.

This isn't to say that you always get current savings with blue LEDs. I tend to run the blue LEDs I use at roughly the same current level as my others, for various reasons.