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Simple High Performing Headphone Amp
Simple High Performing Headphone Amp
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Old 12th June 2018, 07:33 AM   #71
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by darbost View Post
Could this be a good preamp as well?
Certainly yes, with the ability to drive ANY impedance (even 8ohms) and low distortion, and what distortion there is when driven hard, is all second harmonic and monotonically descending higher orders 3rd and 4th...

It's also very good as preamp from standpoint of JFETs on input stage, so very low currents flow and pot makes no noises when adjusting volume.

As a DC-coupled amp, it is brutally revealing. Make sure your source has no DC or you might want an AC-coupled 4.7uF filmcap input coupler (toggle switch in/out).

I would imagine this amp driving a 10kohm load is a walk in the park.
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Old 12th June 2018, 10:27 AM   #72
darbost is offline darbost  Indonesia
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Originally Posted by xrk971 View Post

As a DC-coupled amp, it is brutally revealing. Make sure your source has no DC or you might want an AC-coupled 4.7uF filmcap input coupler (toggle switch in/out).
This means even for a low dc offset (less than 10mV, around 5mV) it will need a filmcap?
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Old 12th June 2018, 08:47 PM   #73
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Make sure your source has no DC or you might want an AC-coupled 4.7uF filmcap input coupler (toggle switch in/out).
Would this be on the board?
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Old 12th June 2018, 09:20 PM   #74
xrk971 is offline xrk971  United States
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Originally Posted by badboygolf16v View Post
Would this be on the board?
Not yet but letís see if JPS64 can add it.
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Old 13th June 2018, 05:01 PM   #75
xrk971 is offline xrk971  United States
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The amp design is moving along. With more bells and whistles. Now with selectable Xfeed and optional input cap coupling. Built in single 12vdc to dual rail with DC step up and TI LDO 4uV regs and CRCRC.

Simple High Performance DC Coupled Class A HPA with sub PPM THD-fr4_complete_v1_top_6-xfeed-png
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Old 19th June 2018, 03:00 PM   #76
xrk971 is offline xrk971  United States
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New DC-DC PSU with LDO, cap Mx, and CRCRC tested in hand etched prototype and works well.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

More here:
Simple High Performance DC Coupled Class A HPA with sub PPM THD
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Old 19th June 2018, 03:17 PM   #77
badboygolf16v is offline badboygolf16v
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See ya later toroid!
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Old 26th June 2018, 08:44 AM   #78
sarathssca is offline sarathssca  India
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Originally Posted by xrk971 View Post
This one
Click the image to open in full size.
I think here J3 and J4 needs to be matched (read somewhere)..
Do all the 4 jFets needs to be of same type or can we have J3 and J4 as BF862 as it is and use the cascode transistors with some other fFet or BJTs (bc5xx series )?
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Old 26th June 2018, 11:56 AM   #79
xrk971 is offline xrk971  United States
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Yes, J3 and J4 need to be matched and J5 and J6 can be another type of JFET of similar Idss. Changing to BJT will require additional components I think and I have not tested it that way. You are welcome to try and mod it or suggest a BJT. However, the BF862 is so cheap that it doesn’t make any sense to.

Btw, measurements of the DC-DC PSU shows that it really does resemble a battery in low noise performance.

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Old 26th June 2018, 12:47 PM   #80
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by darbost View Post
This means even for a low dc offset (less than 10mV, around 5mV) it will need a filmcap?
With a 10mV offset from the source and 20dB gain, you will have 100mV dc offset at the output. I hibk thatís probably an unacceptable level of offset for most headphones.
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