[makasin]

EDIT:
Do you know how the Steinchen drop in buffers will be sold?
Group Buy? Will they be prebuilt?

Also, what enclosure did you guys for your SOHA?
I'm looking for one that will let me fit the transformer as well as the tube inside and made of plastic or something that a dremel can drill through. Having the tube inside the enclosure, will this cause any heat problems? I am thinking of making a bunch of holes on the top (like making a honeycomb design made of holes above the tube) to cool them. Will this be sufficient? Also, how do you guys mount the board to the enclosure?

I am trying to box up my SOHA so I can sell it and build a crazy one hehe.
Do you think, with the buffers instead of OPA2134, I could make a SOHA that could be better suited for my Senn HD650s than a Gilmore Lite?
The one I have sounds pretty damn close and that one IMO was a relatively sloppy build with parts that were much less than ideal.
For example I got the wrong rectifiers. The pinouts were very different, which didnt allow me to put them in directly. I had to run a wire from one of the pins into the board. The board has ones where the 2 (-) poles are on one side of the chip and the (~) on the other side. Mine had them crossed:

-~
-~
instead of
--
~~

Anybody know of the part number for the correct one on Mouser?

 

[headphonejunkie]

I used the parts list on the mb3k site. You might want to try the 15 volt regulators though. I think all you need to do is substitute 15 where the 12 is in the part number. Most op amps usually run at 15 volts. I don't know why they did not use 15 volts instead of the 12 listed.With 15 volts you get that much more voltage swing; +-15 instead of +-12. I am planning on building a case with my woodworking tools. Sort of along the lines of a ear+ but out of wood. With wood you won't have all of the grounding issues like with a metal chassis.

 

[regal]

I am sort of playing devils advocate here but I do not believe that any of the popular 1455 Hammond enclosures will work well with the discrete buffers. Not the drop ins or the air-wires. Here's why:

The drop-ins won't fit in the 1455's because they are too tall. The board will need to be on the 2nd from bottom slot. Steinchen says we will need to put the output caps on the bottom of the board for the drop-ins to fit. Obviously this won't be possible with the PCB in the 2nd slot from the bottom. Also with the drop-ins there isn't room for a headphone jack, so this means you will have to push the board back, meaning you will need the 8.6" long 1455 if you want a transformer in there. I guess you could air wire the output caps and just leave them loose next to the HP jack, but I don't like to here an amp rattle when I pick it up.

With the air-wires and the biggest 6"x8.6" hammond you will have to put the buffers up front on each side. This will put the headphone jack and the volume knob very close to each other in the center of the front panel if you want the transformer in the case. The other issue I am having trouble with is any 1455 wider than 100mm means standoffs. So now you will have to pull the tube before you can slide off the lid. So a standoff is needed under the tube, meaning no LED. Also with the PCB on standoffs, it will be very very difficult to line up and drill the hole in the top for the tube. You will also have to put all your big caps on the bottom of the board so the tube is high enough to pull before removing the lid.


In summary any of the 1455's will be a very difficult case to use with the SOHA + discrete buffers. I am considering the Jameco 209358, which is 7.5Lx9.8Wx3.2D, but I haven't seen one and don't know what the aesthetics are like.

Your question is a very good one and I am very interested to hear what case others are considering for the SOHA w/ d buffers.

 

[tomb]

Quote:

Originally Posted by headphonejunkie /img/forum/go_quote.gif I used the parts list on the mb3k site. You might want to try the 15 volt regulators though. I think all you need to do is substitute 15 where the 12 is in the part number. Most op amps usually run at 15 volts. I don't know why they did not use 15 volts instead of the 12 listed.With 15 volts you get that much more voltage swing; +-15 instead of +-12. I am planning on building a case with my woodworking tools. Sort of along the lines of a ear+ but out of wood. With wood you won't have all of the grounding issues like with a metal chassis.

There are many opamps that cannot operate with +or-15V. Notably, the AD8620 and AD8066 are among them. There is plenty of voltage leverage in the basic design. In fact, it operates HD580's much better than something like Grados - this with the original design using TO-92's in those regulator positions. Remember that the original design intent was something less than $50 for an amp.

Once the subject of add-on buffers comes about (probably because of obvious comparisons with the Millett), this reasoning goes out the window. Current demands mean that even TO-220 regs cannot run without heat sinks. However, the Digi board is woefully crowded in those positions. There's no chance for an efficient extruded heat sink. Hence, the upgrade to 15V regulators. The higher voltage means more power for less current, mitigating the sink requirements somewhat. This allows the use of less optimum stamped/finned heat sinks which can be bent into shapes around some of the other board components.

 

[tomb]

Quote:

Originally Posted by regal /img/forum/go_quote.gif I am sort of playing devils advocate here but I do not believe that any of the popular 1455 Hammond enclosures will work well with the discrete buffers. Not the drop ins or the air-wires.

I disagree, and you may not be rising to the challenge.

Remember that Steinchen is dealing with the very same issues.

Quote:

Here's why: The drop-ins won't fit in the 1455's because they are too tall. The board will need to be on the 2nd from bottom slot. Steinchen says we will need to put the output caps on the bottom of the board for the drop-ins to fit. Obviously this won't be possible with the PCB in the 2nd slot from the bottom.

Steinchen quoted a general height of about 1.2" above the opamp socket. With the board in the 3rd slot, it is almost 1.25" to the bottom of the top plate. The typical Wima MKP's fit on the bottom in this position, which happens to be where all mine are - and I have three sitting in Hammon 1455 cases in the 3rd slot.

Quote:

Also with the drop-ins there isn't room for a headphone jack, so this means you will have to push the board back, meaning you will need the 8.6" long 1455 if you want a transformer in there. I guess you could air wire the output caps and just leave them loose next to the HP jack, but I don't like to here an amp rattle when I pick it up.

See the above about the output caps - it isn't a problem, except for perhaps some wacko boutique caps, with which strange mountings should be expected. As for the headphone jack, this has yet to be determined. Certainly, the locking Neutrik's I have wired will not fit in a "normal" position. They may fit, however, in a vertical position from the top plate, not an uncommon position for many traditional tube amps. There is also plenty of room in back, but granted, that's not a preference. However, with something like this, there is always some give and take. If you go back to a 3.5mm jack, it will fit almost anywhere - including right in the front.

Quote:

With the air-wires and the biggest 6"x8.6" hammond you will have to put the buffers up front on each side. This will put the headphone jack and the volume knob very close to each other in the center of the front panel if you want the transformer in the case.

A walwart enclosed transformer is superior both in sound quality and convenience. Since you are already looking at Jameco from your note below, I suggest you consider one of the Jameco walwart enclosures. All you need add is an in-line fuse holder or PolyFuse. The in-line's are available at Jameco, other online vendors, and any Radio Shack. You can use dual 2.1/2.5mm std plugs/sockets, DIN, or simply hard-wire it with sufficient length, as Batman did in the original SOHA thread.

As for the jack, there was never any PCB-mounted jack on Digi's board anyway - the leads would simply be a little longer. If the volume control is board-mounted, that will require a shaft. So, you have a case in that respect. Nevertheless, shafts are available, and air-wiring an end-plate mounted pot is done all the time.

Quote:

The other issue I am having trouble with is any 1455 wider than 100mm means standoffs. So now you will have to pull the tube before you can slide off the lid. So a standoff is needed under the tube, meaning no LED. Also with the PCB on standoffs, it will be very very difficult to line up and drill the hole in the top for the tube. You will also have to put all your big caps on the bottom of the board so the tube is high enough to pull before removing the lid.

As demonstrated above, mount your xfmr in a walwart and use the extra length available (the basic Digi SOHA board is very, very short) for the buffers. The SOHA board itself will be held in place by the endplate in the back, and the standoff mounted buffers in front. If not exact, perfboard or other plastic sheet may be used to lock the SOHA board in place between the buffers and the rear endplate - without standoffs. The board and top can still be removed in one step to change the tube.

Quote:

In summary any of the 1455's will be a very difficult case to use with the SOHA + discrete buffers.

It may require a modicum of ingenuity, but DIYer's are more than capable of doing this.

Quote:

I am considering the Jameco 209358, which is 7.5Lx9.8Wx3.2D, but I haven't seen one and don't know what the aesthetics are like. Your question is a very good one and I am very interested to hear what case others are considering for the SOHA w/ d buffers.

Your choice, but some positive thinking may help.

 

[regal]

The drop-in jisbos he shows in the headwize thread ilooks more like 1.75" w/out heatsinks. I used photoshop to scale it based on 1/16" thick PCB.