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Pass HPA-1, what do we know?
Pass HPA-1, what do we know?
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Old 5th December 2016, 09:57 PM   #21
Zen Mod is offline Zen Mod  Serbia
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Pass HPA-1, what do we know?
yup

though - proper ratio of shunt /load currents starts with 1:1 , but rougher/wilder the circ, we must increase headroom
however , that roughness is limited with A class circs having moderate output currents ... and going with mentioned ratio above 3:1 is likely nothing else than waste of heat

btw. mentioning shunt regs - I'm not messing with PL construction decisions .......... I know that you boyz know how to make shunt reg , same as anything else

edit : what you are obviously lacking of , on that picture , is proper amount of mess on bench

that's too tidy .......
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Last edited by Zen Mod; 5th December 2016 at 10:00 PM.
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Old 5th December 2016, 10:26 PM   #22
jam is offline jam  United States
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Hi Zen Mod,

I just happen to be a big fan of shunts ...that is a personal opinion and does not necessarily reflect the thoughts of other people at Pass Labs.

I have always been a fan of your work because you build stuff before you come to a conclusion.

As far as the mess goes I did clean the bench up a little for the picture. I will try to follow proper bench etiquette in future.
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Old 5th December 2016, 11:10 PM   #23
mlloyd1 is offline mlloyd1  United States
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Pass HPA-1, what do we know?
don't do it jam!
with a clean bench comes no respect!
a true builder with a clean bench?
naaaaaahhhhhh ...



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Old 6th December 2016, 07:01 AM   #24
juma is offline juma  Germany
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Quote:
Originally Posted by xrk971 View Post
... Component values? ...
It's a basic circuit and values are easy to calculate. The fun is in the additions: different types of current mirrors, cascodes, shortened feedback loop, no feedback loop, etc.
The playground is wide here so everyone can find what he likes the best...
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Old 6th December 2016, 07:30 AM   #25
2 picoDumbs is offline 2 picoDumbs  Australia
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Quote:
Originally Posted by jam View Post
Yeah Pico,

.........it would be Pico on the barbie!
I just had a vision.

https://www.youtube.com/watch?v=C1nxaQhsaaw
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Old 6th December 2016, 07:36 AM   #26
jam is offline jam  United States
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Juma, I could not agree with you more, I have been following your posts for some time now, keep up the good work.

Current mirrors are great building blocks and get you around some of the problems of a traditional VAS as long as some care is taken, but in the end it is how you use a given topology to meet your design objectives.


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Old 6th December 2016, 07:42 AM   #27
jam is offline jam  United States
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Nice one pico!
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Old 7th December 2016, 05:15 AM   #28
Hikari1 is offline Hikari1  United States
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Thanks guys. Especially nice to hear from Jam about this amp.

I am not trying to reverse engineer it...more interested in the knowing what Jam and Pass Labs likes topology-wise for headphones. It's interesting stuff and it's info you can't get from other manufacturers.
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Old 7th December 2016, 01:57 PM   #29
jam is offline jam  United States
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Hi Hikari,

Juma is essentially correct about the topology but I use a different type of mirror in the HPA-1.

One thing I need to add is that most modern headphones, especially planers are a lot harder to drive than the traditional headphones so you have to adjust your designs accordingly. I am not married to this topology as each design is different, that being said I am a big fan of current mirrors in the right application.
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Old 7th December 2016, 02:10 PM   #30
Dennis Hui is offline Dennis Hui  Canada
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Pass HPA-1, what do we know?
Hi Jam,

One thing that caught my attention was the preamp out functionality of the HPA-1.
What is the max voltage swing from the HPA-1?

Thanks,
Dennis
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