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Old 22nd May 2012, 05:22 PM   #21
TheGimp is offline TheGimp  United States
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Simulation shows 0.196% THD at 180mVrms. this is predominately 2nd order.
Third Harmonic is down at 4.66e-5
4th is at 8.26e-7. (below -120dB)

I'm using Dmitry's triode mode model.
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Old 22nd May 2012, 06:26 PM   #22
mogliaa is offline mogliaa  United Kingdom
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Quote:
Originally Posted by TheGimp View Post
Simulation shows 0.196% THD at 180mVrms. this is predominately 2nd order.
Third Harmonic is down at 4.66e-5
4th is at 8.26e-7. (below -120dB)

I'm using Dmitry's triode mode model.
Sounds promising Steven. Would you mind sending me your circuit so I don't start from scratch?
thanks
Ale
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Old 22nd May 2012, 06:52 PM   #23
TheGimp is offline TheGimp  United States
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Here is the circuit and 6E5P_T model in a zip.
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File Type: zip 6E5P_Headphone_Amp_1.zip (1.8 KB, 76 views)
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Old 22nd May 2012, 07:02 PM   #24
mogliaa is offline mogliaa  United Kingdom
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Quote:
Originally Posted by TheGimp View Post
Here is the circuit and 6E5P_T model in a zip.
Thanks Steven. I thought you simulated what Lars was proposing. I can work from this one (which is same one as I had but with Dmitry's model).
Cheers,
Ale
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Old 23rd May 2012, 01:40 AM   #25
Bigun is offline Bigun  Canada
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Originally Posted by mogliaa View Post
Hi Bigun,
On the last edition of Morgan Jones' book he found that 6BX7 shows a big variance in distortion so these need to be manually chosen for audio use...
Cheers,
Ale
Thanks - that's a good tip to know about.
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Old 23rd May 2012, 06:11 AM   #26
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Think the whole idea of OTL is doubtful as the tubes are working in an unlinear area.

Add a 4:1 transformer after a single 6E5PT cathodefollower(hereticalstyle) and we are talking at least ten times lower distortion. Load is now in the ballpark of .5k. One have to watch the DCRs though, as these contribute to Zout. And is there a suitable transformer available??

You can dump the input transformer but need to keep the CCS to add necessary current.

Last edited by revintage; 23rd May 2012 at 06:14 AM.
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Old 25th May 2012, 06:09 PM   #27
mogliaa is offline mogliaa  United Kingdom
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Quote:
Originally Posted by revintage View Post
Think the whole idea of OTL is doubtful as the tubes are working in an unlinear area.

Add a 4:1 transformer after a single 6E5PT cathodefollower(hereticalstyle) and we are talking at least ten times lower distortion. Load is now in the ballpark of .5k. One have to watch the DCRs though, as these contribute to Zout. And is there a suitable transformer available??

You can dump the input transformer but need to keep the CCS to add necessary current.
Hi Lars,
Will the classic Sy heretical stage be sufficient? Perhaps need some valves in parallel. Will simulate over the weekend.

Interesting proposal, however, need to check what OT could fit there...
Thanks
Ale
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File Type: jpg 6e5p headphone circuit .JPG (114.3 KB, 168 views)
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Old 26th May 2012, 07:49 AM   #28
mogliaa is offline mogliaa  United Kingdom
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Here we go again. Well, 36mA of anode quiescent current per valve. Need three to get THD down to 0.10% at output voltage of 100mVrms. This is a nice operating point for the 6e5p, and FFT looks clean to me.

Is there a better choice of CCS transistors?

Only cap is input, which could be removed if an input transformer is used.

I think I should breadboard this one and listen to it?
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File Type: png 6e5p OTL headphone version2.png (30.1 KB, 149 views)
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Old 26th May 2012, 07:59 AM   #29
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Do you hope to have 6E5Π's that well matched that they ll work well with one CCS?
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Old 26th May 2012, 08:07 AM   #30
mogliaa is offline mogliaa  United Kingdom
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Clearly that is one of the challenges here. Will need to test some and see if I can make a matched trio
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