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Old 7th June 2010, 01:30 PM   #31
juma is offline juma  Germany
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Quote:
Originally Posted by thanh1973 View Post
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Maybe I should also try the toshibas in the front end of my Aleph 30.....
I would not do that - you'd need a lot of current through that LTP and it doesn't seem like a good idea at all, especially in context of the amp as a whole.

Best upgrade would be to turn your Aleph into Aleph-J (Toshiba JFETs at the input.)
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Old 7th June 2010, 03:56 PM   #32
EUVL is offline EUVL  Europe
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> The F4 has less than unity gain, not very practical for a headphone amp, imSo.

My DAO Follower also has unity gain.
All those who built it loved it, especially if you have low impedance phones.

Much easier to build than a down-versioned F4, may I add.


Patrick
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Old 7th June 2010, 10:02 PM   #33
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Best upgrade would be to turn your Aleph into Aleph-J (Toshiba JFETs at the input.)
Thanks. I have one of those too (ie Aleph J).
I have been away for a while, and I can see my enthusiasm is getting the better of me.

I will definitely be giving these mosfets a go in my F5.
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Old 8th June 2010, 04:37 AM   #34
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How about using these on the burning amps 1 and 2 to replace irf610.
Do they really need to be biased high? How about 50mA or 100mA
I understand you want to bias them high on the F5 output stage, but do you really need to bias them that high in a circuit such as BA2.
The other option is to throw a power Jfet in that position, however that is an expensive option.
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Old 8th June 2010, 08:11 AM   #35
juma is offline juma  Germany
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There's a nice test you could make - go ahead, do it and report back
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Old 14th June 2010, 09:06 AM   #36
prakit is offline prakit  Thailand
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Hard-wired the thing during the past weekend. I picked what I thought a rather generous sized heatsink so I could play with high current bias. And hopefully build a balanced version with these sinks.
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Old 14th June 2010, 09:28 AM   #37
juma is offline juma  Germany
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Looking good prakit
You should be fine with that heatsink, just use white heat-transfer paste more liberaly
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Old 21st June 2010, 08:09 AM   #38
prakit is offline prakit  Thailand
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To follow up my attempt to try this a line amp...

I supplied each channel with a set Jung's super regulator set at +/-23V as seem the attached picture. I've been listening to the line amp for a week now. This version of F5 with a pair of k2013/j313 indeed makes a very good lineamp.

I tried varying the bias of the output Mosfets up to 450mA where the regulators seemed running out of steam(the heatsink for the pass devices became very hot). It did sound better at higher bias but the dc drift at the output was getting bigger too. I settled at 250mA where it sounded good and the dc stability was good too.

This circuit should make a very good sounding headphone amp too.

Anything I can do to minimize the dc drift at higher bias?

Regards
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Old 21st June 2010, 08:46 AM   #39
juma is offline juma  Germany
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Originally Posted by prakit View Post
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Anything I can do to minimize the dc drift at higher bias?

Regards
Of course, the most simple, but very effective thing to do is to add NTC resistors (like in F5). They are changing their resistance with temperature thus keeping the current through MOSFETs and DC offset constant.

Btw, great build
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Old 9th July 2010, 07:23 PM   #40
generg is offline generg  Germany
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Quote:
Originally Posted by thanh1973 View Post
How about using these on the burning amps 1 and 2 to replace irf610.
Do they really need to be biased high? How about 50mA or 100mA
I understand you want to bias them high on the F5 output stage, but do you really need to bias them that high in a circuit such as BA2.
The other option is to throw a power Jfet in that position, however that is an expensive option.

I tried the other option and put two SSR100 instead of irf610

......sounds more liquid!
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