Current source for BOZ

Current source

1.Yes

2.Yes

Dale.

You might have to bribe Harry with a case of Foster's larger.
Harry is correct but if I were you I would build the balanced version and current source that.

Jam

Jam,
Would it be better then to built Aleph P1.7?

given that it is such a low dissipation i would use a standard dc current source.

Peter,

I think the Aleph P 1.7 is a better preamp, it seems to be more datailed. I used to own one but if you like a slightly warmer sound stick with the balanced Zen. However both are excellent units.

Jam

So finally somebody shed some light on how those two preamps compare. I think there is another advantage to Aleph P. It uses only positive supply while Balanced BOZ needs both positive and negative rail.

Couple questions on building Aleph P 1.7

Jam or anybody .......
1. Is building Aleph P 1.7 a lot more involved than building BOSOZ?
2. If it is, what are some of the tricky areas?
3. Isn't it true that they have a patented volume control?
4. Is the volume (controller?) easily built too?
5. Does anybody know approximately what it would cost to built this pre-amp?
6. Is all the parts shown on the schematics easily obtainable?

yes more involved in general...

it's the x-series preamps that have the special volume control ... the p 1.7 control is pretty simple

The disadvantage of he P circuit is that you need input coupling capacitors. I have not tried a current sourced balanced BOZ against an Aleph P (1.7). The current sourcing will surely elevate the performance of the BOZ coupled the with the elimination of the input capacitor may give the P a run for it's money.

Jam

fcel I just love your questions. You are able to cover every angle.

1. From looking at both schematics I'd say that Aleph P is 3 times more complicated but requires only positive supply so I'd say it's almost the same complexity.
2. The tricky areas here would be more circuitry you have to deal with. So if you decide to do PCBs - more complicated artwork, if you wire p2p - more work. But nothing serious really.
3. I don't know if the volume is patented but I woudn't touch it. From what I see it's more complicated than a preamp. I would just use switched attenuator, something like the volume in Pass Labs Dac. Very simply and it works great.
4. I guess I answered it previously.
5. The cost greatly depends on the componets, power supply and chassis. If you want to do it really cheap it might cost you $50, on the other hand doing it the way I like you might have to spend $500 (still it's only rough calculation)
6.If you not talking about original volume cotrol no problem with parts.

jam,
It's a really good point with a capacitor. David Broadhurst has an "improved" balanced BOZ on his site: http://www.geocities.com/d_broadhurst/preamp.html
You can even buy PCBs from him.

Peter,

Looks like a good design I believe it is different from the P(1.7) in that it uses cascodeing and the P uses an active load on the drains of the differential. Should make an interesting comparison.
I have been working on cascoded version of the BOZ (low current) with outputs hooked to current sourced buffers.

Jam

i just finished a boZ point to point wired on a piece of wood, 100*100mm, and the aleph p volume control with 6 of takamisawa ry12w-k, driven by BC550C, on perf board 100*80mm, 2 1/2 hours of work each.

fcel,

I am also interested in making an Aleph P 1.7, and I am planning on laying out some pcbs next fall, and possibly getting together another bulk order in august/september if there is enough interest.

I think that you should build the BOSOZ for now, since there are good quality boards available for a reasonable price from audioXpress.com. I am almost done building mine. The parts were quite easy to get. I used all of the components listed in the article, except for I used Vishay Dale RN55 resistors instead.

It should work great with your aleph, and you can later on use the same chassis for an Aleph P, should boards be made.

--
Brian
brian@brian.prohosting.com

Brian,

For your information, I have built the BOSOZ already and I'm very happy with it. I spent 80% of the time building the chassis because I don't have the right tools and that's why I decided to invest a little bit on the tools for building the Aleph 2 and possibly many other projects in the future. When I said building the chassis, I actually meant modifying a case that I bought from swap meet - took out all the internal parts, drill holes and so on.

As for the BOSOZ itself, I have asked a couple times (including you) about getting a 4 gang 10K pot for the volume control (at a reasonable price) but so far no luck. I'm currently using two 2 gang pot for the left and right volume control. I have built it with balanced input and output.

Then the subject came up about building a Aleph P - it's probably you or Dale that brought it up. I want to let you know that I would be interested to join again for another bulk order.

fcel,

Sorry for the confusion. If you happen to find a decent 4-gang pot, let me know.

--
Brian
gte619j@prism.gatech.edu

It might be hard to find cheap 4-gang pot, especially in the low resistance value. Why don't you use 2 gang pot the way it was implemented in Dac 1. Just place it between positive and negative side of balance output. You only need two decks for that. Very simple.