[cetoole]

Nothing interesting on AIM or IRC tonight, and I finished the book I was reading, so I figured why not do another random amp board layout? Anyways, here it is, a slight modification of a common design seen around here, but larger, at ~66mm x 90mm. Feel free to comment, or make suggestions. I may or may not have a couple made up for me to actually build, it was done mainly for fun.

 

[Polaris111688]

Looks kind of like a simplified PPAv2.

 

[NeilR]

Looks more like a Pimeta for the brave new BUF634less world

If it were mine, I would make it 100mm long so it slides sideways into a Eurocard sizze case, but then the POT would need to be turned 90 degrees, killing the nice layout.

If you are going to use a largish board, why not make the output trannies TO220 size?

Then modify the design for a scaled down M3 type topology using Mosfets, which would simplify the output buffer considerably. I haven't seen anyone try to do that, but a more transportable/portable M3 would be interesting.

These suggestions should fill another evening of spare time, at least

 

[tomb]

My thoughts, exactly, Neal - and I replied as much first thing this morning on you-know-where. That's where cetoole posted first, apparently.

Yep - Diamond Buffer PIMETA, and yes - it would be nice if the board had enough space on the sides to fit in Hammond case slots. I don't know enough about your other comments, but as noted in another thread - I've been trained to perk my ears up at the mention of MOSFET.

 

[NeilR]

I retract my comment about the TO220 size; I see I missed that when I got lost in the sea of TO92's.

Not to leave any stone unturned, it might be interesting to add a little space for TO220 heat sinks. Just the tiny ones that are used with Treads, for example. It would be interesting to see how high those parts can be biased with a little sink.

Further thought on board size- you could even add the 10mm and leave it empty so it can be cut off if you want to miinmize the board size.

Tomb, great minds think alike!

 

[blueworm]

Quote:

Originally Posted by NeilR Looks more like a Pimeta for the brave new BUF634less world

I like this idea how about a solution for the brave tle2426less world also while you are at it.

Perhaps a discrete rail spliter like sijosae had designed or why not dual supply.

 

[NeilR]

Quote:

Originally Posted by blueworm I like this idea how about a solution for the brave tle2426less world also while you are at it. Perhaps a discrete rail spliter like sijosae had designed or why not dual supply.

Here is a simpler solution.

 

[tomb]

Jameco appears to have 200 of the non-ROHS TO-92 version of TLE2426 - for $1.19 and less. As Neil's link proves, there are other sources as well.

I think we are pretty far away from the BUF634-type shortage for TLE's.

EDIT: So when's the Group Buy for this thing?

 

[cetoole]

Quote:

Originally Posted by NeilR Looks more like a Pimeta for the brave new BUF634less world If it were mine, I would make it 100mm long so it slides sideways into a Eurocard sizze case, but then the POT would need to be turned 90 degrees, killing the nice layout. If you are going to use a largish board, why not make the output trannies TO220 size? Then modify the design for a scaled down M3 type topology using Mosfets, which would simplify the output buffer considerably. I haven't seen anyone try to do that, but a more transportable/portable M3 would be interesting. These suggestions should fill another evening of spare time, at least

It could be made 12mm wider to fit the Hammond 1455K1201, which would give room for a tread or something behind the amp. The RK27, or, if I built it for myself, the equivalent Nobel (I got 10

), is just a bit too tall for the J series and shorter Lansings, like the DN2, which is a shame, because I rather prefer that profile. The height of the pot is the issue here, I cant find any cases that I am really enthusiastic about that fit the amp without much excess room. For these reasons, I didnt optimize the board for any specific case, but if anyone here wants to do so, or has specific case recommendations, I will see what can be done, or send board files.

 

[mono]

You might consider moving from 2N5484 to 2N5485 or 86, since the resistor will allow reducing CCS with any of them, but some people might want it higher than a random sample of 2N5484 would allow.

As it stands, there should be no need for TO220 output parts or heatsinks, they just wouldn't build up much heat at the max possible 5mA CCS of 2N5484.

What might be nice is if the board had a divider, with a Tread-like supply and/or a dual supply (if to appease those who want to avoid the TLE2426 for some reason). That part of the board could be scored and snapped off if the builder didn't want it integrated, and the supply tracks from it to the other board used jumpers so if the board were scored and broken, it didn't leave traces going to the separated board edges.

Another idea would be to allow for paralleled BD139/140, at least a 2nd of each.

I also like the idea of rotating the pot 90', and maybe putting a 1/4" HP jack at the opposite end of the board. Of course not everyone would like this but I get on this kick to reduce wires...

I would like the board files for this, please. I don't know if I have time to get anything done, but I like it already and given all the input it may receive and the early stage, it might change more than I'd want, I might like it better as it is now. I had already planned on doing a derivative of PPL's Lisa2 and your design incorporates some of the changes I'd considered.

 

[cetoole]

Quote:

Originally Posted by mono You might consider moving from 2N5484 to 2N5485 or 86, since the resistor will allow reducing CCS with any of them, but some people might want it higher than a random sample of 2N5484 would allow. As it stands, there should be no need for TO220 output parts or heatsinks, they just wouldn't build up much heat at the max possible 5mA CCS of 2N5484. What might be nice is if the board had a divider, with a Tread-like supply and/or a dual supply (if to appease those who want to avoid the TLE2426 for some reason). That part of the board could be scored and snapped off if the builder didn't want it integrated, and the supply tracks from it to the other board used jumpers so if the board were scored and broken, it didn't leave traces going to the separated board edges. Another idea would be to allow for paralleled BD139/140, at least a 2nd of each. I also like the idea of rotating the pot 90', and maybe putting a 1/4" HP jack at the opposite end of the board. Of course not everyone would like this but I get on this kick to reduce wires... I would like the board files for this, please. I don't know if I have time to get anything done, but I like it already and given all the input it may receive and the early stage, it might change more than I'd want, I might like it better as it is now. I had already planned on doing a derivative of PPL's Lisa2 and your design incorporates some of the changes I'd considered.

I thought the 2N5484 and 2N5486 were both the same pinouts, just having different range of IDSS values. Unless that is not the case, I dont see what the problem is. I have eagle parts libraries for the 2N5484, and not the 2N5486, which is why you see that part on the board.

As for integrated dual PS, I dont personally see the need to have it integrated on board, especially with jumpers required to utilize it. It is an interesting idea, though requires more work for the builder. I have done a layout recently for the tread (Tangent comes up with such great schematics, I cant help myself. Thanks Tangent

), and it wouldnt be difficult to integrate a pair of these replacing the TLE2426.

I dont really like the idea of paralleled output buffers; I would think the TO220 package would be able to dissipate enough heat that class A wouldnt be an issue with most of the headphones used. Three of the output transistors now have enough space to allow the use of small heatsinks, and it should be simple to add enough space for the others, I am just not sure if its needed.

See that space next to the pot? That space used to hold a board mounted neutrik combo jack, which is, IMO, one of the nicer jacks of the sort I have seen so far. The main reasons I scrapped that were flexability, and it greatly complicated the trace layout. Unfortunatly, with the pots I like to use, the amp would be just a bit too tall to fit the Hammond 1455L1201, and mounted sideways, the next case that would fit is the 1455N1201, which is much taller than we need. It would give space though for the dual treads you were talking about earlier, and I cant find any other cases that I like more, so I will think about it. If you want the board files, just shoot me a PM with your email address or some way to send the files.

 

[mono]

Quote:

Originally Posted by cetoole I thought the 2N5484 and 2N5486 were both the same pinouts, just having different range of IDSS values. Unless that is not the case, I dont see what the problem is. I have eagle parts libraries for the 2N5484, and not the 2N5486, which is why you see that part on the board.

It's no problem, was just a passing comment since I saw the 2n5484 on the schematic. They do have same pinout.

Quote:

As for integrated dual PS, I dont personally see the need to have it integrated on board, especially with jumpers required to utilize it. It is an interesting idea, though requires more work for the builder. I have done a layout recently for the tread (Tangent comes up with such great schematics, I cant help myself. Thanks Tangent ), and it wouldnt be difficult to integrate a pair of these replacing the TLE2426.

I wasn't necessarily suggesting everyone would want it, but, some might and it's easily enough snapped off. It was just another passing idea after reading that someone had pause about using TLE2426. Plus, it's like a bonus, getting a single or dual regulator board for a different use for trivial cost difference if boards are made.

Quote:

I dont really like the idea of paralleled output buffers; I would think the TO220 package would be able to dissipate enough heat that class A wouldnt be an issue with most of the headphones used. Three of the output transistors now have enough space to allow the use of small heatsinks, and it should be simple to add enough space for the others, I am just not sure if its needed.

I put 6mA CCS through TO92 parts and they didn't break a sweat. There shouldn't be any need for 'sinking now... but that goes back to what the builder ultimately decides to use for the CCS, 2N5484 or another part.

Quote:

See that space next to the pot? That space used to hold a board mounted neutrik combo jack, which is, IMO, one of the nicer jacks of the sort I have seen so far. The main reasons I scrapped that were flexability, and it greatly complicated the trace layout. Unfortunatly, with the pots I like to use, the amp would be just a bit too tall to fit the Hammond 1455L1201, and mounted sideways, the next case that would fit is the 1455N1201, which is much taller than we need. It would give space though for the dual treads you were talking about earlier, and I cant find any other cases that I like more, so I will think about it. If you want the board files, just shoot me a PM with your email address or some way to send the files.

Some people like the pot and jack close and some don't. I fall into the latter category, I always want at least 40mm unless using a teeny volume knob. I'm frustrated by case options too and am real real close to just ordering thick plate aluminum and DIY case from scratch. Anybody know the best way to DIY anodize a clear coat?

YGPM

 

[cetoole]

Quote:

Originally Posted by mono I wasn't necessarily suggesting everyone would want it, but, some might and it's easily enough snapped off. It was just another passing idea after reading that someone had pause about using TLE2426. Plus, it's like a bonus, getting a single or dual regulator board for a different use for trivial cost difference if boards are made. I put 6mA CCS through TO92 parts and they didn't break a sweat. There shouldn't be any need for 'sinking now... but that goes back to what the builder ultimately decides to use for the CCS, 2N5484 or another part. Some people like the pot and jack close and some don't. I fall into the latter category, I always want at least 40mm unless using a teeny volume knob. I'm frustrated by case options too and am real real close to just ordering thick plate aluminum and DIY case from scratch. Anybody know the best way to DIY anodize a clear coat? YGPM

Yeah, I guess with the way pcb costs are it would be only a buck or so extra, if that, to add a pair of the following boards to each pimeta, and everyone can always use extra regulator boards, if not for this project then something else.

I agree with liking some spacing between the pot and the output jack, though if the case had been one that was just barely larger than the board, there wouldnt have been too many options. Large milled solid aluminum knobs are what I greatly prefer, I cant stand any of the plastic or composite ones. I say go for the custom casing, that could be pretty nice. I dont have the tools to do something like that here, so I am more limited. DIY Anodize I hear is possible, although difficult and potentially dangerous. I have heard of Alodine being suggested for DIY instead of anodizing, might be something to look into.

YGEM

 

[mono]

Eagle files up, thank you cetoole! Email sent.

PimetaDB3.sch
PimetaDB3.brd

 

[ATAT]

mono... clear ano isn't that hard if you have a nice fat vat of sulfuric acid and some car batteries. coloring it, however, is a whole different story.

As for custom cases, I had an idea while back that utilizes 1/8th plate stock all around with 4-40 hex cap screws to bolt the whole thing together. It looks nice in cad, and only takes a drill press and bandsaw..
if you have acess to a mill though, you could mill yourself a full case out of just 1/4 in alu stock.

Meh.