DIY Audio Projects Forum

I suggested in the BoZ thread that the whole of BoZ - both channels - could be completely constructed on the output caps. Because I am using high quality polypropylene 10uF caps there is just enough real estate to construct. And Gio through down the challenge. Thanks Gio!!!

I could have made each channel separate but instead, to make the whole construction look even more compact, I have bonded both output caps together. This means I only have one side to do the total construction. AM I MAD? Remember that this BoZ, similar to my BoZSE, has no input caps (BDP-83SE (source) has output caps) and no attenuator (all sources must have level control).

I feel the secret of why BoZ sounds so incredibly good is the 20,000 to 30,000Ff of storage cap right on the cct. brd. There is no way I can do BoZ on a cap with massive storage caps like this. So BoZ on a Cap or BoZoaC will never sound quite like its fat brother-BoZSE.

I can go part the way there and build BoZoaC with reasonable storage caps onboard and bring along some of those lovely sweet Pass-ages (as in Mr Pass) of construction. Two 1000uf/35V low ESR caps are part of the BoZoaC construction and for good measure I threw in the 1ohm 1W R.

I do not know if this project will see light of day or even Pass music but come along for the journey and see how far we get. The power section has already been partially constructed. Super glue is now my friend. I'm hoping this will become a step-by-step instruction on how-to build a BoZoaC engine.

It is my intention to run this build on batteries (27V) but an external PS will work also. I'm just trying to keep everything mini. Images tomorrow of construction so far and some explanation.

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Projects: Oatley K272C - headphone amp in a tin can | "VoXDeuX" - Inexpensive two-way speaker | "VoXItBassO" - stereo 12" sub-woofers ]
Website: [ retro-thermionic ]

Very cool. The layer of glue bonding the other components to the cap will provide superb damping.
Could sound very good indeed.

_________________
Kind Regards,
Dinesh

Some of my diy audio projects:

• Elliot Sound Products - P3A 100W Amplifier
• TMM 2.5 Way Loudspeaker with Scanspeak 18W8546
• 2-Way MTM Loudspeaker with Scanspeak 21W8554 and D2904-7100

From the images it is easy to see the placement of the larger caps. The brown are the output polies. The 1ohm resistor feeds the collective positive wire of the 1000uf low ESR storage caps and then extends as a +V feed for the one resistor (each channel) which will connect to it. The two smaller resistors at the front are the 470ohm output coupling resistors.

Two negative voltage feed lines run under the caps to provide connection points for other resistors. Double sided tape holds the bigger components together and super glue the smaller parts.

_________________
Projects: Oatley K272C - headphone amp in a tin can | "VoXDeuX" - Inexpensive two-way speaker | "VoXItBassO" - stereo 12" sub-woofers ]
Website: [ retro-thermionic ]

This is great Mark. Take a lot of photos! With the oddball shape, you will be able to house this in a small cylindrical shaped tin or similar.

Also, if you power the circuit off of batteries, you likely will not need the big tank capacitors and the large power resistors.

Cheers

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[ DIY Mains AC Power Cable Cord ] - [ K-12 Tube Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]

Gio, you think that powering the preamp from batteries would mean you could use smaller storage caps but in think in practice this is not the case. And I'm a little lost why large storage caps for such a low current drain device is even suggested. But it just seems to work. Against all common sense the large storage caps appear to provide much greater bass weight. So I fear that though this has a reasonable storage cap, in fact two good size caps onboard, the preamp may not perform as well as the 30,000uf Nelson suggests. You could always add these big caps in a remote PS, still a possibility.

_________________
Projects: Oatley K272C - headphone amp in a tin can | "VoXDeuX" - Inexpensive two-way speaker | "VoXItBassO" - stereo 12" sub-woofers ]
Website: [ retro-thermionic ]

Hi Mark, that could be due to 9V cells being rather limited in how much current they can deliver. That may not be the case f you used a bunch of AA batteries in series.
Cheers

_________________
[ DIY Mains AC Power Cable Cord ] - [ K-12 Tube Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]

I have used lithiums in the past which have a 1200mAH rating. You would think they would have enough current. I think you just can't beat big storage caps when in comes to SS devices. But, hey! I might be wrong.

Without trying a cct. with and without large caps its just an obsevation or a feeling at the momment. But of all the preamps I have built the two Pass's seem to be the most bassy.

_________________
Projects: Oatley K272C - headphone amp in a tin can | "VoXDeuX" - Inexpensive two-way speaker | "VoXItBassO" - stereo 12" sub-woofers ]
Website: [ retro-thermionic ]

The resistors which run from the output cap to ground have been added and a thick, pure silver earth strap now connects the two negatives of the storage caps together. The remains of the negative wire of the storage caps becomes the common earth. To this point the other two resistors which connect to ground will be connected.

To this point I have been trying to keep the sides of the brown polies clear. I will now use these to attach the last two resistor which go to ground, the one resistor which goes to the pos. rail and to the jFET drain and the JFET its self.

In each case the parts have been soldered in place then super glued. Because often where the glue is there is no pressure the "fast drying" glue takes many hours to dry.

_________________
Projects: Oatley K272C - headphone amp in a tin can | "VoXDeuX" - Inexpensive two-way speaker | "VoXItBassO" - stereo 12" sub-woofers ]
Website: [ retro-thermionic ]

Further development in BoZoaC: The only components to connect to the pos. rail is the drain Rs - 2K2. These have been added, under the polies and connect the input to the output caps (brown polies) and the drain together.

The jFETs have finally been added and one side of the polies (as above) connects to the drain. I wanted the flat side of the jFETS to super glue to the side of the polies. And I wanted the drain to be closes to the poly leads. To do this one jFET has to mounted upside down. Also the the 10ohm resistor which connects the source to ground has been added.

I tried to be very clever with the 10ohm and 2K2 resistors additions but in the end found the solution in the images the easiest and the best!! Don't think too hard about this build if you do it but be prepared to try some "dry" moves before the final placement.

I could have finsihed the BoZoaC engine right here with the addition of two more resistors, but I wanted to display clear step-by-step images of what is added and when (right or wrong). The next images will show the BoZoaC complete. I snookered myself a little. I was going to use the brown polies leads to mount the BoZoaC engine but now have bent one of the leads up to connect to the jFET.

OK who has some ideas how can attach this thing to a cct. brd. or whatever? I'm open to suggestions.

_________________
Projects: Oatley K272C - headphone amp in a tin can | "VoXDeuX" - Inexpensive two-way speaker | "VoXItBassO" - stereo 12" sub-woofers ]
Website: [ retro-thermionic ]

Mark,

Have you thought of sealing it in a small plastic case full with epoxy?
Then the solid cube can be stuck to the case by double sided tape.
Have holes drilled into the main mould for the output wires.
You can name it "Mark's fully encapsulated Boz on a cap "
Sounds silly though...ahaha..

_________________
Kind Regards,
Dinesh

Some of my diy audio projects:

• Elliot Sound Products - P3A 100W Amplifier
• TMM 2.5 Way Loudspeaker with Scanspeak 18W8546
• 2-Way MTM Loudspeaker with Scanspeak 21W8554 and D2904-7100