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Old 12th December 2013, 10:28 AM   #61
Kram is offline Kram  United Kingdom
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Trying again, lol.

Q1 collector 10v
Q2 Emitter 10v and Base 5v
Q3 collector 5v
Q8 collector 5v
Q6 collector 0.5vp-p

Q4 base 102mV, emitter 0.5 v p-p

Thanks for trying to help out kenpeter, what you said did seem strange to me too so I went back and measured again, results above.
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Old 12th December 2013, 11:13 AM   #62
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Try a 15pF ceramic capacitor across the base and collector of Q3 .
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Old 15th December 2013, 05:29 AM   #63
Kram is offline Kram  United Kingdom
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Thanks for the tip, it seems to have worked so far.
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Old 15th December 2013, 08:26 AM   #64
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Thanks for the feedback
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Old 15th December 2013, 05:56 PM   #65
OV54ZXH is offline OV54ZXH  United Kingdom
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Default JLH Hedphone Amp as Preamp

Could I use this as a preamp for the JLH Class A Amp?
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Old 21st January 2014, 10:13 AM   #66
cHoc is offline cHoc  Netherlands
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Quote:
Originally Posted by siliconray View Post
Oppps..Both should be 500 Ohm.

Both 10 and 20 works for R15. For low impedance headphone 10Ohm is better. Just keep them the same value.

Sorry for the inconveniences.
Do the 10 and 20 Ohm resistors then work better for the higher impendance headphones, 300ohm and up?
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Old 3rd February 2014, 11:31 PM   #67
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This will be my first DIY power amplifier and I have ordered almost all the necessary parts today. I really like to make this high-end.

I will be using the free JLH 2005 circuit board, and the Darlington design power supply discussed earlier in this thread Free Power Supply PCB For JLH Amplifier - Boards | Kits | Components | Modules | Tools

Transformer not yet... I remember when the company TeraDak changed all their transformers to R-Core type, they said it took away the hum.

I saw some comments about a 200W transformer earlier in this thread, is 200W recommended?

My power sockets are around 230V. How are these specs 220V, 200W, 20V+20V output?

ebay.com/itm/220V-200W-R-Core-Transformer-Output-20V-20V-/121189176316

Is it better to use one with two output values? For example there is one with 40V+40V and 15V+15V.

When I type "R-Core 200W" into Ebay I get 10 results, which one should I pick? I hope someone can help me find the ultimate transformer !!

K Lacer

Last edited by K Lacer; 3rd February 2014 at 11:49 PM.
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Old 3rd February 2014, 11:54 PM   #68
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What would actually happen to the amplifier if I used a 50W transformer? Like this one? 50W 220V R Core Transformer 18V 18V | eBay

I don't really get the difference. Thanks for any help!
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Old 4th February 2014, 12:20 AM   #69
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- deleted, these questions were meant for the power amp thread -

Last edited by K Lacer; 4th February 2014 at 12:27 AM. Reason: mistook thread title
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Old 30th April 2014, 06:29 PM   #70
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What sort of current load do these headphone amps impose on the power supply - I believe they run at 100mA quiescent current? I have some +/- 12V supplies based on LM317/337 devices that I would like to use, one per channel; only problem is they already have PCB mounted transformers that only deliver around 330mA, though they could be replaced with off-board transformers if necessary.

Thanks
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