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Old 16th December 2009, 01:50 PM   #11
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Quote:
Originally Posted by Skorpio View Post
Instead of one common ECC81 (one half for each channel) I am using two seperate ECC81, one for each channel with one half left unused...
Oh yes that makes sense, I was unsure of what you meant initially. Sounds like an interesting idea.
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Old 16th December 2009, 02:59 PM   #12
hwong is offline hwong  Canada
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Anyone have an idea about the Panasonic FM series cap compare to the FC that was included in George partlist from Digikey? Is the FM series good for Audio application?
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Old 16th December 2009, 03:20 PM   #13
rknize is offline rknize  United States
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Quote:
Originally Posted by Ty_Bower View Post
When you install the electrolytic capacitors, don't have them tight up against the board when you solder them in. Leave a small (1/16" ~ 1/8") gap between the bottom of the cap and the circuit board.

George makes a passing mention of this somewhere in the assembly instructions. If you keep them tight against the board, then each time they expand/contract from thermal cycles, they pull at the leads. Eventually it can cause early failure of the cap. Leaving just a tiny wiggle room here eliminates this problem.
Actually he goes into incredible detail about it. Can caps these days have a rubber or foam foot at the bottom to prevent this problem. However it doesn't hurt other than making the amp a little less vibration resistant (which is not an issue unless you are shipping UPS .
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Old 16th December 2009, 03:25 PM   #14
rknize is offline rknize  United States
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Quote:
Originally Posted by Skorpio View Post
Is it possible to change from UL to triode mode and from feedback to non-feedback during playback?
Do as we say and not as we do.

The UL/triode switch causes some pretty nasty transients on this SE amp it seems. I can do it on my ST-70 with only a tiny click. The Simple SE makes an angry scratchy pop, which I'm sure my speakers don't like. I generally avoid doing it with the amp powered on but nothing has burst into flames as a result of doing it. Also remember that you are switching several hundred volts with a switch that is probably rated for 250VAC at best. The contacts don't see much voltage across them, but relative to the chassis....

The feedback switch is much more benign and sounds perfectly clean when flipped on my amp. I suspect the transients are slugged-out by the cathode resistor bypass cap.
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Old 3rd May 2010, 11:48 AM   #15
Skorpio is offline Skorpio  Denmark
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Giving second life to this old thread...

I have finally received parts for my SimpleSE amplifier. Output tubes will be EL34 and output transformator 5000/8, powersupply about 420-450VDC.

There is only one primary winding on the OPT (25W type) so I have no option for UL...

Seeking some answers:

1) What will be the output power in Triode and Penthode mode?
2) Will 470R be a good value for Triode connection and Penthode connection?
3) What will input sensitivity be in the two modes?
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Old 3rd May 2010, 12:22 PM   #16
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Output power in triode mode with 450 volts B+, EL34 tubes, 5K primary loading, and 470 ohm cathode resistance should be about 6.29 watts. See George's chart here: Tubes & Transformers

Power in UL mode would be higher, but you say you do not have the required tap on the OPT secondary for it. George's board is not inherently designed to operate the finals in a true pentode mode. You would have to rig up some kind of screen supply for that.

I think 470 ohms cathode resistance is much too low for EL34 types, especially if you expect to have B+ around 450 volts. The tubes will be significantly over their dissipation limit. I'm using 810 ohms in my Simple SE (started with 560, and added another 250 in series).

I've found my Simple SE to be fairly sensitive, but the final result depends on many factors (output transformer's effective primary impedance, use of cathode feedback, use of ultra-linear connection, etc). I need very little gain from my preamp to drive it to the levels I want. I should expect it could be driven directly from an iPod or CD player without the need for a preamp at all.
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Old 3rd May 2010, 12:42 PM   #17
Skorpio is offline Skorpio  Denmark
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Hi and thank you for your answer!

This table was what I was looking for...partly...

I would not use 470R as cathode resistor, but as a resistor connected from grid to +B to enable penthode mode...

What are the sonic differences between triode and UL on your amp?
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Old 3rd May 2010, 12:57 PM   #18
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Quote:
Originally Posted by Skorpio View Post
What are the sonic differences between triode and UL on your amp?
UL gives more power and noticeably higher sensitivity. As far as the quality of sound is concerned, I think I prefer triode mode - although I couldn't explain why. Overall, the differences seem subtle to me.
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Old 3rd May 2010, 02:43 PM   #19
rknize is offline rknize  United States
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Not too many people run the SSE in pentode mode. I have not tried it. You'll most likely want CFB when using pentode mode to improve the output impedance and DF.

The simplest way to do it is to connect the screens to the B+ rail...probably right where the OPT gets B+ from. You just need to watch that you are not exceeding the screen's rating. This puts the screen voltage above the plate voltage, which is normally not what you want (though many designs get away with it). The "proper" way to do it would be to add another RC step after the B+ rail and connect the screens to that.

On my system, the main difference between triode and UL mode on this amp depends which speakers I am using. My less sensitive speakers (~90dB) like the extra power from UL mode, but I don't hear a huge difference otherwise. My more sensitive speakers (98dB) have horns and they seem to protest less when the amp is in triode mode, perhaps simply due to some HF roll-off from driving the finals in triode. There is also more "detail" or "sound stage" in triode mode.
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Old 2nd November 2013, 03:00 AM   #20
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sorry for the thread revival, but how would one use a ecc81 as a CCS? It seems that this question was never answered and i am rather interested in this as i also have a chassis with an orphan 9pin socket that i would love to employ instead of the CCS IC
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