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Old 7th July 2008, 10:46 AM   #181
Tolu is offline Tolu  Germany
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Quote:
Originally posted by Nelson Pass
One of the keys to good performance with that chip is an
extremely high impedance load.

Nelson,

does this mean that the DS1802 isn't suitable for the B1 / JBOZ ? Or do you have a little trick (circuit) how to use it?
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Old 7th July 2008, 12:19 PM   #182
juma is offline juma  Germany
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Nice and simple way to use DS1802:
http://www.pedjarogic.com/spot/index.html
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Old 7th July 2008, 01:03 PM   #183
Tolu is offline Tolu  Germany
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But not so suitable when I read this:

Quote:
Note that the DS1802 will not, working with shown supply (you can try to push it harder but you will do that on your own risk), accept the conventional output level of the CD players. It will certainly clip with usual 2V RMS and more, and with such sources DS1802 is unusable unless you decide to attenuate the signal before it enters the pot (in my view this approach does not have much integrity though). Clipping is instant and very unpleasant but generally all is well as long as it does not occur. So, a lower voltage at the pot input is a must. This, however, won’t be that bad for those using common base based or purely passive I/V converters in their CD players – almost always such kinds of stages will be happy to develop lower voltage.
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Old 7th July 2008, 01:25 PM   #184
GuidoR is offline GuidoR  Italy
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Quote:
you can pretty easily use exact schmtc

Zen Mod: Why 16V and not 18 as in B1's schematic?
It's enough to add a LED to obtain 18V?

Many thanks
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Old 7th July 2008, 02:02 PM   #185
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by GuidoR
Quote:
you can pretty easily use exact schmtc

Zen Mod: Why 16V and not 18 as in B1's schematic?
It's enough to add a LED to obtain 18V?

Many thanks

naah
just think - it's not carved in stone ;

that schematic isn't originally intended for B1 , but for some Serbian NS10 project for newbies (for 24V); and l;ater someone asked me to rearrange things for 16-17V ......

more precisely - voltage on output will be approx . 8xUled + 1V35 , where 1V35 is Ube for darlington . it wasn't made for extra precise voltage , but rather for stability

if you use green leds , they can be anywhere between 1V9 and 2V1 , but - as with most project s, difference of 10% in PSU voltage is important just for newbies .......
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Old 7th July 2008, 02:04 PM   #186
massimo is offline massimo  Italy
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Zen Mod / George (Clooney)

J1 - for choke_what else!

What kind of choke_what else?

Can you specify?
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Old 7th July 2008, 02:10 PM   #187
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by massimo
Zen Mod / George (Clooney)

J1 - for choke_what else!

What kind of choke_what else?

Can you specify?

either shortie ( so - no choke ) or any choke you have in drawer , starting from 5mH/200mA with no more than 10 Ohms Rdc

clear enough ?

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Old 7th July 2008, 02:23 PM   #188
GuidoR is offline GuidoR  Italy
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difference of 10% in PSU voltage is important just for newbies .......

....it seems that around Milan (where also my home is) there's a newbie's nest.....

Thanks Zen Mod

Ciao Massimo
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Old 7th July 2008, 02:56 PM   #189
MEH is offline MEH  United States
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Default JFET grades

Why does the B1 (and Pass amps more generally) use GR or BL grade 2SK170s? I mean, the circuit obviously has to be designed to use some Idss grade, and Papa did design it to use GR or BL, but why? Is there something about lower Idss grade JFETs that makes them audibly superior to higher Idss parts, or is this just another example of Papa using the parts he has on hand, even though another part could have been used equally well in a slightly different design?
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Old 7th July 2008, 03:05 PM   #190
ctong is offline ctong  United States
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Default B1 as a headphone amp?

A question somewhat outside of the discussions here.

Can the B1 be used as a headphone amp for high-impedance, high sensitivity headphones, such as Sennheiser HD600 (300 ohm nominal, 97db/mw). I do not think such headphones will need more than a couple of mA to reach very high sound levels. I have been using my DIY Aleph P with excellent results. And I almost never need to go past unity gain.
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