EHHA Rev A - Interest Thread

[qusp]

hehe, yeah but I dont know how trivial it would be. so yep, put me down for 4 boards 

 

[runeight]

This is a really interesting discussion. I'm glad we're having it.
 
Along with circuit tweaks, the primary idea here was to relieve you of the external PS complexity. This change was aimed primarily at SE (non-balanced) amps. Make the build easier and have separate PSs on each board to reduce crosstalk through the PS.
 
But, the snap-off version does increase board size by 10mm in length. making built-in PS version a little less compact and useful for its original purpose and even more challenging for a balanced amp.
 
Before we fix on the latest there is another alternative still.
 
I could simply redo the original EHHA board with the circuit tweaks. The only thing that would change would be to reduce the number of heatsink locations from four to two.
 
Then we could figure out a PS arrangment for those who don't want the s22.

 

[fishski13]

Quote:

This is a really interesting discussion. I'm glad we're having it.
 
Along with circuit tweaks, the primary idea here was to relieve you of the external PS complexity. This change was aimed primarily at SE (non-balanced) amps. Make the build easier and have separate PSs on each board to reduce crosstalk through the PS.
 
But, the snap-off version does increase board size by 10mm in length. making built-in PS version a little less compact and useful for its original purpose and even more challenging for a balanced amp.
 
Before we fix on the latest there is another alternative still.
 
I could simply redo the original EHHA board with the circuit tweaks. The only thing that would change would be to reduce the number of heatsink locations from four to two.
 
Then we could figure out a PS arrangment for those who don't want the s22.

this is an amp i want to build.  i already have a s22 powering my B22, but would like to have the option of populating the on board PS or using my s22.  count me in for a stereo pair.

 

[Beefy]

Quote:

Originally Posted by runeight /img/forum/go_quote.gif
 
I could simply redo the original EHHA board with the circuit tweaks. The only thing that would change would be to reduce the number of heatsink locations from four to two.
 
Then we could figure out a PS arrangment for those who don't want the s22.

That sounds like a much better idea. I don't think that there is any particular benefit to having the PSU on the same board...... but a separate board for a specific power supply simpler than the S22 might be handy for some.
 
Still, I suspect most will opt for the S22 anyway......

 

[Forte]

 
Quote:

Along with circuit tweaks, the primary idea here was to relieve you of the external PS complexity. This change was aimed primarily at SE (non-balanced) amps. Make the build easier and have separate PSs on each board to reduce crosstalk through the PS.
 

 
I like the idea of a simple build, complicated isn't always better. 
Keep the on board PS with the option to use an external supply for those who want to go all out.
 
Can the new design still use 6922/6DJ8 & 6H30 tubes?
I thought I saw an answer to this but re-reading this thread cannot find it now.

 

[pabbi1]

I know this is a bit afield, but would this amp benefit from adding adding DC heaters, or is that a complexity that may not add real benefit? 

 

[jdkJake]

This is a really interesting discussion. I'm glad we're having it.


 


Along with circuit tweaks, the primary idea here was to relieve you of the external PS complexity. This change was aimed primarily at SE (non-balanced) amps. Make the build easier and have separate PSs on each board to reduce crosstalk through the PS.


 


But, the snap-off version does increase board size by 10mm in length. making built-in PS version a little less compact and useful for its original purpose and even more challenging for a balanced amp.


 


Before we fix on the latest there is another alternative still.


 


I could simply redo the original EHHA board with the circuit tweaks. The only thing that would change would be to reduce the number of heatsink locations from four to two.


 


Then we could figure out a PS arrangment for those who don't want the s22.

So, I guess I liked the idea of the built-in power supply. I would even forgo the snap option to get the board back to being as small an implementation as practical. Of course, I am looking to build a SE version and not a balanced version.

Are the remaining circuit tweaks enough to justify a respin of the original EHHA? To me, the attractive part is a smaller, simpler implementation that does not require an additional power product. Otherwise, is the original EHHA that far off from the new design?

Then there is still the big unanswered question, will the new version sound any better?

 

[runeight]

New design can still use 6922/6h30 although these might be less optimal.
 
DC heaters are ok and might reduce noise.
 
Will it sound better? I don't know. I know it will be faster, but this difference will be at fairly high frequencies.
 
Seems like we have different thoughts about on-board or off-board PS and whether to just tweak the orignal EHHA board or use the new one.
 
I guess we need to think on this further.

 

[jdkJake]

I'm flexible. Anyway you want to do it is fine by me.

There are distinct advantages to a separate power supply as well advantages to the current boards ability to use external heat sinks, so, that works as well.

Whatever the consensus is works for me.

 

[tcpoint]

I, actually, prefer having the power supply on the board.  This looks like a fun build.

 

[fishski13]

i haven't built the original, but what are the issues here?:
 
-you want to use the boards to drive HPs with or without the newly added on-board PS (me).
-you want to use the boards to drive speakers, but will need to use an off-board PS (s22 or other home-brewed regulated or unregulated).
 
seems like it's easily rectified with a scored PS/Amp board PCB.  the new PCB has the new PS on one scored portion and the Amp on the other with pads on both sections to solder in the PS.
 
Alex,
what JFETs/resistors are the CDRs replacing?  is this just to simplify to CCS - do the JFETs  need to be matched?  and while CDRs are more expensive, they offer a simple design approach, like zeners?  can i have PCB pads for CDR, CCS, and a dumb resistor

.  

 

[runeight]

Next step. Trying to meet all the needs.

 
This is the same split board as before with some mods. I've left the bottom layer power planes visible so you can see how they traverse the board. Click the pdf and you can get the full sized image.
 
First, the PS section has an additional set of mounting holes. It has two connectors on it now so it can stand alone. If you split this off you can use it to make a separate, stand-alone regulated supply for other purposes provided that you don't exceed the power dissipation in the heatsinks.
 
If you leave the PS section connected it will automatically power the amp board through the power planes on the bottom and ground plane on the top. In this case you don't use the terminal blocks in the middle of the board except to take the O/P. But, you can also use the terminal block on the PS section to run wires to another board that doesn't have the PS section.
 
Or, you can split off all of the PS sections and use a different supply.
 
The only thing not done is to get the O/P devices to a convenient location for off-board heatsinks. To do this will substantially increase the size of the board and maybe make it impractical.
 
However, what I can do is to ensure the the mosfets are oriented in such a way so that they can be laid flat on heatsinks that would be on either side of the board. I haven't done this yet, but if you all like the rest of the board I can make this change.
 
The bjts will not be oriented correctly for this, but the fets will.
 
fishski, the CRD is replacing Q3, R8, R9, D1, D2. R6 has also been removed, but was not part of the CCS. I think I will leave it alone. You can always put a resistor there if you want, but adding a bjt ccs will be more complicated.
 
There are no jfets in this amp so no jfet matching is required. For the 2SC2705/2SA1145 it is best to buy them in the same gain classes, but no further matching should be needed.
 
Are we getting closer?
 

 

[runeight]

Board might look something like this
 

 

[fishski13]

i understand the CCS now after spending some time looking over the schematic.
 
well you could do off-board heatsinks as is if the output devices are mounted underneath.  are those C9 and C12 electrolytics near the output devices?  at less than 0.5" tall, you could bottom mount these and use 0.5" stand-offs to allow top-side mounting of the output devices for off-board heatsinks with an L-bracket.  

 

[stixx]

Nice, compact looking board...
I am still in for a stereo pair, but give it some time until you make it a Group Buy
(vacation until Sep 11)