[ppl]

I hear Ya! That I lobbied the other Team PPA members for from the onset and got voted out.

However in lue of the Non short circuit protection The True locking non Board mounted jack with pads located right at the Necessary point by the required jack lug for a short connection. As it is now requires care on the part of the assembler but this was assumed due to the nature of the Beast.

I also wanted a board mounted bass boost switch as it also requires care in routing on the Builder. so if ya all want to support me on this maybe the other team members will accommodate

 

[tangent]

Quote:

Why is a capacitance multiplier being considered instead of a full out regulated one?

Several reasons:

1. It's neat, and you can't get them anywhere else. If you want a linear regulated supply, many DIYable choices exist already: the Gilmore, the Wellborne PS1, one or two from Rod Elliott, Velleman... And in the commercial market, there are many more.

2. A properly-done capacitance multiplier should be able to have stability every bit as good as a regulated supply over the short term, which is what you care about. For long-term wall voltage changes, the output will also slowly change, but op-amps can cope with this no problem.

3. I'm fairly sure that it's more efficient. No turning excess voltage into heat.

4. Morsel and ppl had some neat ideas they wanted to try out, and I'm willing to go along with them.

Quote:

if the board is populated with the 2200uf Panasonics this would create 26,400uf of filter capacitance

I agree that this is probably overkill. The other side of the argument is that it's nice to have the ability to do this if you want to try it, and we don't really intend that you use generic capacitors with this amp anyway. At the very least, dig up some nice Nichicon Muse series or something. Then you can have merely a moderately insane amount of high-quality capacitance -- a few thousand mics is easy to hit, even with exotics.

I should point out that the second row of C1's is the first thing that will go if we need space. We're not dead-set on keeping all those caps if we have a better idea of how to use all that space.

Also, Morsel brought up an alternative earlier that people need to consider: is it better to use one row of 16 or 18mm diameter caps instead of two rows of 12.55mm ones? To decide this question, we need people to provide specific capacitor examples and show that the alternative with 12.5mm caps is in some way less appealing. The only one given so far is the Cerafine 1000uF/35V. Besides being hard to get, this cap is very tall: we only have about 31mm of space above the board for C1 if you put a battery board in the case, too, and this cap is 37mm tall. We'll need better examples than this to convince us to go to a single row of fat caps.

 

[tangent]

Quote:

I lobbied the other Team PPA members for from the onset and got voted out.

My objections to this haven't changed from what I said in my post on this subject above. However, I'm willing to be swayed on the matter. I just want to make sure that people who request this understand the consequences. It's expensive in at least a couple of senses of that word.

Quote:

I also wanted a board mounted bass boost switch as it also requires care in routing on the Builder.

I offer a challenge to anyone who wants to board-mount everything: how would you route S2R's pads to the front of the board?

 

[eric343]

Can you post a picture of the layout without the ground plane?

 

[Whit]

Quote:

To decide this question, we need people to provide specific capacitor examples and show that the alternative with 12.5mm caps is in some way less appealing.

The 2200uf FC cap that is mentioned on the PPA site would be 35mm tall as well as rated for only 25V. If the diameter is boosted to 16mm then the 2200uf cap would be 31.5mm tall and rated for 35V. If a 35V, 16mm, 1800uf FC cap is used then the height is 25mm. In short, the larger diameter caps would allow for more vertical space for things such as the battery board. If the vertical space is not needed then boutique caps could be used such as the cerafines or blackgate. All of the 12.5mm caps on the PPA site are only rated for 25V. Since they will be seeing the full 24V(or whatever Voltage) this time versus the meta42 a 25V rating is too close for comfort.

Here are three black gates that would work with the 16mm spacing.

BlackGate STD 470uf 50V [16mm x 36mm]
BlackGate NX 680uf 35V [16mm x 24mm]
BlackGate STD 330uf 50V [16mm x 32mm]

Here is a nichicon muse:
470µF..................50V KZ ......... 1.75 ........16mm x 35.5mm

Here is a elna silmic:
35/470uf 16 x 33mm

Whit

 

[tangent]

Quote:

The 2200uf FC cap that is mentioned on the PPA site would be 35mm tall as well as rated for only 25V.

You're right, Morsel should probably remove mention of that cap and maybe use one of the 1500s or something instead.

If we go with board-mount everything and the custom panels that that requires, we'll have to require that everyone mount their PPA board in the case such that a battery board could fit underneath even if you don't use it. I don't want to multiply the number of panels I have to prototype and stock by another 2x. Thus, 31mm or so above the board is pretty much a hard limit. 31.5mm is probably do-able, but we haven't tested case space issues in detail yet.

It's just as well -- 12x 2200uF is pretty silly. Again, the idea is to use smaller capacitance, higher quality parts rather than huge capacity generics.

 

[tangent]

Quote:

Can you post a picture of the layout without the ground plane?

What's under there are the traces from the input pads at the rear of the board going to the pot, and then the traces coming from the pot's wipers to R1 on each side.

I'm assuming that you're asking in response to my challenge, so I'll just tell you that the idea won't work. Since the trace on the bottom of the board going from the pot wiper to R1R extends virtually clear across the top edge of the ground plane, you can't get underneath the ground plane from its top edge except to the right of R1R. And you don't want to move the R1R trace out from under the ground plane because that's one of the traces the ground plane is there to protect. You also can't play games with vias to get under there unless you manually cut a hole in the ground plane to go around the via, since ExpressPCB doesn't know how to do that itself. That means cutting a perfectly good ground plane into at least four pieces. Bleh.

 

[ppl]

When the Board is mounted in it's uppermost posistion so the top of the Vol pot just clears the Top corner of the hammond Enclosure so as to make room for the battery board then 30 MM High caps ar the largest useable as that just clears the inside top of the case and 25 MM for the caps on the outer edge of the Board.

The Quality of the capacitors will have less of an inpact on the sound than thay would on conventional Grounded Headphone Configuation But still quility caps Proabaly make a difference I'll report on this when i replace the Nitchicon 1000uF 35 Volt 12.5 x 30 MM types of whitch (6) are installed with silmics II's at a later date in the prototype. if you are going to use the AD_8610 opamp your supply is limited to 25 volts or less anyway and thus 25 volt caps would be best as you will be operating the caps in there most linear range there working voltage. while Higher voltage caps work you lose capacitence as the actual operating voltage is reduced from the Working voltage.

 

[tangent]

I've got a better idea than an image without the ground plane: one with overlapping traces in purple. If it's purple, you can't cross it.

 

[JMS]

Tangent: I hadn't thought about the routing issues you brought up. Thanks for pointing them out.

Quote:

Before we can even think of board mounting everything, we have to get everyone to agree on a single set of components.

What I had in mind was that the designers will choose a single set of components and layout -- just like the set of resistor values. You don't have to please everyone exactly. It will be a compromise: people who use the "reference" design may not get exactly what they want, but in exchange they will get a better-looking amp that's easier to build. Those who must have something else can still make it themselves. Thus, you don't have to make 4 kinds of face plates for bass boost/crossfeed/etc. combinations -- just one for everyone.

Thanks for considering our suggestions!

 

[tangent]

Let's start getting down to brass tacks, then. For all those who want board-mount everything, what are your views on the following issues?

1. Which type of RCA input jacks to use?

2. How many sets of RCA jacks? Just one input? Two inputs, switchable? One input and one passive or buffered pass-through?

3. What 1/4" output jack to use?

4. ALPS Blue I presume?

5. Bass boost switch?

6. Crossfeed switch?

7. Where does the LED go, centered or to the left side of the panel? If centered, does it go near the top, down at board level, or centered precisely within the panel area?

8. Ditto for the output jack: is it centered so you can unplug even the stiff locking Neutrik jack one-handed with either hand, or on the left side like most amps do it, but requiring two hands to unlock it for lefties, and maybe righties, too?

9. What kind of power connector?

10. How big should the volume knob be? Style?

11. What style of power switch?

12. Allow space for 1/8" jack holes to be drilled near RCAs and 1/4"? Surely you wouldn't want holes in the panel that you have to plug if you don't want 1/8" jacks as well.

 

[eric343]

Tangent, thanks for posting a much bigger and more readable layout

For the S2R routing, move the trace that's right under the C4x text onto the left side of the C4x's left pads. Use the vacated space to run two parallel blue traces from S2R (actually, C5R) under the C4s and under R1L-R3L. Alternately, put the bass boost switch on the back and route the blue trace under R1R-R3R, which might need to be moved a bit.

An in-optimal solution to be sure, but it would help if the amplfier/buffer blocs were closer to the C1s.

 

[tangent]

Quote:

move the trace that's right under the C4x text onto the left side of the C4x's left pads.

You mean to the right, surely.

Still and all, your solution would probably work. Bonus: it goes under the ground plane, which may help considerably.

Quote:

Alternately, put the bass boost switch on the back

Then you have similar problems with S2L. Besides, it belongs on the front.

 

[eric343]

Yes, to the right of course... what can I say, it's midnight.

And yes, good point... maybe separate the two??

...hey, this is supposed to be a 'no-holds-barred-mostly' amp, it's not hifi if it isn't at least slightly inconvenient...

 

[JMS]

My preferences:

1. Any gold-plated RCA jacks, such as Radio Shack's.

2. One set of input RCA's, one set of output RCA's in parallel with headphone jack. Both sets on the back panel.

3. Any good-looking 1/4" jack is fine. I don't care about the locking part. In fact, I'd rather pull the jack out by accident than rip my headphones off my head by accident. The possible accidental output short, to me, is a very low expect cost of not more than a dollar, given the low probability with which it happens.

4. ALPS Blue.

5. Bass boost switch (on/defeat) if bass boost circuit is in, although I don't need the bass boost.

6. Crossfeed switch (on/defeat) if crossfeed in. Crossfeed would be nice but not necessary.

7. Headphone jack on the left. Volume on the right. Switches and LED(s) in between. All vertically centered.

8. Headphone jack: two-handed plug/unplug is fine. I'd think that carrying around this amp and having to unplug it with one hand is a very rare ocasion.

9. Power connector: A DC jack? Any is fine.

10. Volume knob: big, shiny metal, such as Kilo DDS-90-1-5 (Allied Stock # 664-2451) which has a nice skirt.

11. Power switch: any is fine.

12. No space needed for 1/8" jack for me.