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Old 21st March 2010, 03:34 PM   #1111
Salas is offline Salas  Greece
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A Rega P3 + arm went on eBay yesterday for 277 euro....

jd
Look for any Systemdek or Audionote in very good condition too.
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Old 22nd March 2010, 09:36 AM   #1112
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I found a JLH buffer with higher current output, usable as headphone buffer.
It is called a Jisbos and was posted by Juma. Good soundquality is reported.
i have and idea of an even simper 4 transistor buffer with gain, based on folded cascode priciples like in the MPP. I will post that later.
Today i am building the darlington version of the JLH buffer.
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File Type: pdf Jisbos Headphone Buffer.TSC - TINA.pdf (40.5 KB, 138 views)
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Old 22nd March 2010, 11:42 AM   #1113
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I build the JLH Darlington Buffer and it works very well.
It is much faster then the verion with BC550 / 560.
It goes up to 14MHz - 3dB, the first version only went to 1.4MHz.
It has a slight overshot in the 9Mhz region so i will try to raise the gate stopper.
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Old 22nd March 2010, 07:09 PM   #1114
Salas is offline Salas  Greece
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Now I think if we put BD139,140 directly in the JLH Jfet-BJT compound follower, maybe we can directly drive headphones with just 4 semiconductors and a healthy voltage input for it?
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That should be posible.
The circuit as is can drive 150 Ohm, so even that circuit could already drive high impedance phones.
Quote:
Originally Posted by Joachim Gerhard View Post
I found a JLH buffer with higher current output, usable as headphone buffer.
It is called a Jisbos and was posted by Juma. Good soundquality is reported.
i have and idea of an even simper 4 transistor buffer with gain, based on folded cascode priciples like in the MPP. I will post that later.
Today i am building the darlington version of the JLH buffer.
Aha, that was tried after all. Cool. Now if you will add some gain successfully too, we talk a very diy friendly solution. Good luck.
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Old 22nd March 2010, 08:36 PM   #1115
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Here is the basic idea.
Itīs a kind of High Current High Z MPP with feedback.
I have to work out the resistor values and i will come up with a better Bias solution.
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File Type: pdf Folded Cascode Buffer with Gain Alpha.TSC - TINA.pdf (32.5 KB, 145 views)
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Old 23rd March 2010, 12:14 AM   #1116
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The JG Self Preamp takes shape.
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Old 23rd March 2010, 12:17 AM   #1117
iko is offline iko  Canada
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PCBs may be nice and tidy, but there's a charm that these "air sculptures" have and I like them a lot. Nothing else says "research" more than these.
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Old 23rd March 2010, 05:54 PM   #1118
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One channel of the JG Self is up and running.
No hum and very low noise. This new AD chip is superbly quiet.
I listened to headphones ( Sennheiser HD280 Pro) and drive is ample and clean.
Offset can be adjusted with the trimmer in the buffer so a servo is not neccesarry
Ofset before the subsonic filter is around 200mV and 1mV after it, so this is no problem.
Offset is a bit dependent on the setting of the volume control. It is 0.4mV full down and -0.5mV full up. I think that is no big deal.
Attached Images
File Type: jpg JG Self Right Channel.jpg (81.7 KB, 371 views)
File Type: jpg JG Self Full Down.jpg (612.4 KB, 362 views)
File Type: jpg JG Self Offset Full Up.jpg (629.7 KB, 338 views)
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Old 24th March 2010, 02:44 AM   #1119
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Default Self ready

The JG Self is ready in Stereo. Itīs quiet like a brick and worked right away.
It even drives the AKG701 to decent volume. That LME49713 is powerfull.
Bass is tight, fast and clean. No question the result of the well designd subsonic filter.
Tomorrow i listen over loudspeakers but i know what to expect.
The sound has a kind of vintage character that is typical for a design with english genes.
Very neutral and nothing is overemphasized. Each intrument has the same proportion so to say. RIAA should be superbly accurate anyway.
i got a new poweramplifier on lone. It is a Berentzen Special Edition so i am much looking forward to the tomorrow session.
By the way, the Baxandall active volume control works superbly well. Itīs a shame that it is not used more. I use a Vishay-Spectrol 148 conductive plastic and channel balance is superp without using an exotic pot. That Spectrol costs around 10,-€ at Farnell.
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Old 24th March 2010, 10:35 PM   #1120
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Default Aditions to homelab

I started to think about usefull adtions to my homelab that i can make myself.
First i build a measuremnt setup for Rbb. It uses the substitution method after Mc.Cormick.
i bought parts for a RIAA encoder too.
In the long run i will get a Quan-Tech noise analyser if i can find one.
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