LTP vs. Cathodyne for 6L6 tweed

ben-horn · 10-17-2009, 10:48 PM

Hi,
i'm on a 5E5-A Tweed Clone and I like it very much.
The Power Tubes clipps first and smooth but driven harder the
cathodyne PI gives some raw and fuzzy distortion.
Do you think a conversion to Long tailed pair PI could work for me ?
Is there a different sound from different PI 's ?
Thanks

loudthud · 10-18-2009, 12:37 AM

Try an experimental mod I posted in reply #3 of this thread:

Paul C mod for PR

The self-biased concertina PI doesn't always bias at the optimum point. The mod allows you to easily set the bias point and also allows you to try different tube types. Does your presence control adjust as expected? Some other builders have had less than expected results.

ben-horn · 10-18-2009, 09:01 AM

thanks loudthud

Yes, the presence works very subtle but I expect this cause of very low nfb.
I already did the Paul C Mod with higher Bias Resistors. 3M9 into 1M was the best for me.With 4M7 into 1M the cutoff was very raw sounding while 3M3 into 1M reduced the headroom too much. Would you tell me your impressions about the sound differences of LTP vs. cathodyne ?

Thanks

soundmasterg · 10-18-2009, 11:21 AM

You might try Merlin's grid current limiting approaches from his site and book.

The LTP will drive the power amp harder than the concertina. I haven't tried switching back and forth in an amp between the two, but I do know the LTP drives the power tubes harder. A paraphase will also. They both have more swing than the cathodyne.

Greg

10-17-2009, 10:48 PM	#1
ben-horn Junior Member Join Date: Sep 2009 Posts: 4	LTP vs. Cathodyne for 6L6 tweed Hi, i'm on a 5E5-A Tweed Clone and I like it very much. The Power Tubes clipps first and smooth but driven harder the cathodyne PI gives some raw and fuzzy distortion. Do you think a conversion to Long tailed pair PI could work for me ? Is there a different sound from different PI 's ? Thanks

10-18-2009, 12:37 AM	#2
loudthud Supporting Member Join Date: May 2006 Location: Texas USA Posts: 923	Try an experimental mod I posted in reply #3 of this thread: Paul C mod for PR The self-biased concertina PI doesn't always bias at the optimum point. The mod allows you to easily set the bias point and also allows you to try different tube types. Does your presence control adjust as expected? Some other builders have had less than expected results. __________________ WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personel.

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10-18-2009, 09:01 AM	#3
ben-horn Junior Member Join Date: Sep 2009 Posts: 4	thanks loudthud Yes, the presence works very subtle but I expect this cause of very low nfb. I already did the Paul C Mod with higher Bias Resistors. 3M9 into 1M was the best for me.With 4M7 into 1M the cutoff was very raw sounding while 3M3 into 1M reduced the headroom too much. Would you tell me your impressions about the sound differences of LTP vs. cathodyne ? Thanks

10-18-2009, 11:21 AM	#4
soundmasterg Senior Member Join Date: May 2006 Location: Cornelius, Oregon Posts: 669	You might try Merlin's grid current limiting approaches from his site and book. The LTP will drive the power amp harder than the concertina. I haven't tried switching back and forth in an amp between the two, but I do know the LTP drives the power tubes harder. A paraphase will also. They both have more swing than the cathodyne. Greg

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