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Old 16th August 2001, 12:59 AM   #1
arnach is offline arnach  United States
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I just downloaded the service manual for the Pass Labs Aleph Ono. I'm very surprised I haven't seen more interest in this design, as I know there was just a thread asking about phono pre-amp circuits??

Anyway, I have an MM cartridge (Grado) and an amplifier with SE only inputs (Mark Levinson).. so I would not need either the moving coil section or the unity gain invertor portion of the circuit. That would leave me with the highly simple power supply and MM gain stage, which I could probably PCB and build in less than a week.

I would probably build a power supply chassis, a left chassis, and a right chassis, all small, and use the circuit exactly. Anyone thought of or done anything like this?

The unit was supposed to sound pretty darn good.

Thanks.. --arnach
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Old 16th August 2001, 01:16 PM   #2
arnach is offline arnach  United States
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Default Helloo


So I redrew the schematic and PCB removing all the components I didn't need and it looks very nice and compact and will fit into a couple nice Thailand Audio (Thlaudio.com) chassis, went and got a price qoute for them.

I was surprised to see that this preamp dosen't have a dual supply, it is a single toroidal transformer (ok), but rectification and regulation (bad?). Is there any situation where this is good? Does this help channel matching?

In my experience and my feeling is to use completely seperate supplies including seperate transformers and make them identical as possible.

All in all with seperate supplies and even three chassis (two p/s, one audio) this will a very inexpensive project.

-- Aaron Finley
arnach5@hotmail.com
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Old 17th August 2001, 02:07 AM   #3
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Aaron,
I had looked at the Ono (so where's Yoko?), but decided against it, as I wanted to pursue the balanced tube circuit I've been working on.
I'm all in favor of separate power supplies and regulation. For no more current than you're going to need for a stripped down version of the circuit, it shouldn't be expensive; I suspect that your problem will be finding a transformer *small* enough, current-wise, so that you're not wasting money. It might be better just to use one transformer, then have separate left & right regulators.
I, too, have heard good things about the sound of the circuit. It should be a worthy project.

Grey
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Old 17th August 2001, 03:48 PM   #4
hifi is offline hifi  Sweden
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hello, i would be most interessted to se your layout for the ONO when you are done!

/micke
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Old 24th August 2001, 10:48 PM   #5
peted is offline peted  United Kingdom
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Hi Aaron - I had similar thoughts on this design - strip it right back for unbalanced MM use only. Looks like this may be my next project - let me know how you get on...

cheers

Pete
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Old 26th August 2001, 03:08 AM   #6
arnach is offline arnach  United States
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Default progress


Just got back from vacation and am going to start drawing the PCB tommorow. Right now I am collecting the various datasheets for the active components and having a rather tough time.

In so much as there are 27 resistors in my take of the design, and 8 of them I have deemed of special importance, I plan to make the 19 not-so-special resistors of the Holco variety, and the 8 of the Vishay variety.

Due to the low number of capacitors also I plan to use high-end capacitors throughout and very expensive high-high tolerance (haven't looked at the catalog yet, can you tell?) caps for the RIAA eq and roll-off.

As for transformers, no single transformer I can buy will not be a total waste of money so I plan to use two per channel. I am going to use the Talema encapsulated devices, they look nice and a relatively inexpensive.

-- Aaron
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Old 26th August 2001, 03:17 AM   #7
arnach is offline arnach  United States
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Question hm?


Anyknow know where I can find a datasheet for the 2SC1844 and the 2SA991?

Google's best hit is the Aleph Ono service manual. heh.

Thanks in advance. --Aaron
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Old 17th September 2001, 11:01 PM   #8
peted is offline peted  United Kingdom
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Hi Aaron - these guys (in the Czech Republic) seem to have all 3 Xono semis - 2SK389, 2SC1844, 2SA991. Don't know about data sheets but if they can supply the real thing does that matter?

http://members.tripod.co.uk/cz34806/semicon/
Has anyone else sourced these semis?

I also found datasheet for 2SK389 - http://www.semicon.toshiba.co.jp/eng...df/e001543.pdf - no they don't have the others. 2SK389 appears to be a power device!!

The best I did with the others is:
2SA991 SI-P 60V 0.1A 0.5W 90MHz
2SC1844 SI-N 60V 0.1A 0.5W 100MHz

both from http://members.tripod.com/Malzev/comp/transist.htm#2sk

So has anyone managed to substitute any of these semis from some place less esoteric - e.g. Farnell/Maplin etc?

I'm not sure on how closely these devices need to be matched. I think only Q5 is critical - and that's looked after by the dual package. Can anyone comment on this? (MM use only - I saw the bit on matching the MC stage semis)

BTW I found these using hotbot.com

Many thanks

Pete

[Edited by peted on 09-18-2001 at 05:25 PM]
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Old 18th September 2001, 05:14 PM   #9
tvi is offline tvi  Australia
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NEC no longer list the 2SA991/2SC1844.
NEC Datasheets <a href="http://www.ic.nec.co.jp/discrete/english/bipolar/products/part_number_st.html#2sa"><b>here</b></a>
They don't have a discontinued item listing either.

My data book list the following in addition to <b>peted</b> posted data
2SA991 NEC 400h<sub>FE</sub> | 5.5pF C<sub>ob</sub> | ECB pinout

2SC1844 NEC 400h<sub>FE</sub> | 4.8pF C<sub>ob</sub> | ECB pinout
Pinout is face on leads pointing down

My Japanese equivelents book lists
2SA991 = 2SA1016K (Sanyo), 2SA1083 (Hitachi) <2N5087(SAMS Listing)>
2SC1844 = 2SC2362 (Sanyo), 2SC2545 (Hitchi), 2SC2602 (Mitsubishi) <MPSA18 (SAMS listing )>

Hope this helps

Regards
James
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Old 8th October 2001, 11:05 PM   #10
lohk is offline lohk  Europe
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You should get 2SK389GR (this is a dual JFet with low noise) and 2SJ170BL at http://www.schuro.de/ in Germany.

2SK389GR DM 3,69
2SJ170 BL DM 0,77

which is pretty cheap !
It do not know if they are available now.

greetings
Klaus
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