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Old 27th January 2012, 12:02 PM   #141
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You might find that pin 6 is not used.

Have a look at the JJ for instance http://www.hebertech.com/datasheet/jj/el34.html

The Mullard http://www.hebertech.com/datasheet/mullard/el34.html notice pin 6 is denoted as NC (not connected)

Again with the Telefunken http://www.hebertech.com/datasheet/telefunken/el34.html

Also, for the 12AX7 replacement have you considered the JAN-GE 5751 http://thetubestore.com/jange5751.html although the Preferred Series 7025 looks very good also.

Last edited by data; 27th January 2012 at 12:19 PM.
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Old 27th January 2012, 12:46 PM   #142
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Just swapped them in, no dramas, obviously had to readjust the bias. Also installed the Preferred 7025's. Listening now.
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Old 27th January 2012, 12:55 PM   #143
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Let me know how the 7025's perform
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Old 27th January 2012, 11:33 PM   #144
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Will do, I'm not sure about the Tung-Sol EL34s.. I'm not great at assessing the sound when I can't listen back to back. My first impressions are that there is less impact and less detail, so I'm going to go back to the Shuguangs.
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Old 28th January 2012, 04:15 AM   #145
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Give them time to run-in, they get better over time initially.
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Old 28th January 2012, 02:41 PM   #146
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Originally Posted by data View Post
Edit: While my amp was still a Yaqin I replaced the .1uf coupling caps with Mundorf silver & oils, and replaced the resistors in the signal path with Kawame's, this was after Triode strapping the EL34's and severing the GNF line, all this made marked improvements to my ears. Although reducing the output power.
Severing the GNF would really up the output impedance and demo the OPT's damping factor. Didn't doing this trash the bottom end?
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Old 28th January 2012, 03:12 PM   #147
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Severing the GNF would really up the output impedance and demo the OPT's damping factor. Didn't doing this trash the bottom end?
After triode strapping the EL34's it was done as all it did was add distortion throughout.

The bottom end was better, as overall the the amount of distortion was less, and it also gave the sense of greater gain.

Edit: I'm using the same transformers now with a new (better circuit), Triode strapped with only local feedback, and I have a better sound than I ever have.

Last edited by data; 28th January 2012 at 03:17 PM.
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Old 29th January 2012, 01:26 AM   #148
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The triode (if we ignore Nelson's new devices) are the most linear amplifing devices made by man, so one can get away with no GNF.

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Old 29th January 2012, 05:04 AM   #149
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The triode (if we ignore Nelson's new devices) are the most linear amplifing devices made by man, so one can get away with no GNF.

dave
The 10L doesn't use triodes though, it uses power pentodes which have MUCH higher plate resistance than triodes. Higher plate resistance = higher output impedance, which if not rectified via GNF, = poor damping factor which = boomy, mushy bass...or so I thought.
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Old 29th January 2012, 05:29 AM   #150
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Easy enuff to wire them into triodes, (lets not get into level shifters instead of a resistor).

MY PP EL34 has a switch to toggle them between triode & pentode.

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