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Old 19th October 2006, 08:22 PM   #1
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Default ECF80 instead of 7199

The price for a famed and (lovely sounding) 7199 is getting out of hand...but the price for an ECF80 is way lower and better still they are in production. I find'em sound good and better than the 7199 Sovteks.

Anyone using a ECF80 instead of 7199 as a split-load phaseplitter ? I get good results from both pentode and triode (sim mu) using slight variation of same components but requires re-layout surgury.

I've also tried the ECF82 (triode higher mu) but sounded rather poor and harder to setup. Anyone agree?


richj
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Old 20th October 2006, 01:24 AM   #2
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Default Maybe

richj,
I've used Oz production NOS 6BL8 which according to my tube manuals is an ECF80 for this duty.
Also used it in a preamp to add bass and treble controls, Sounded great there too.

My tube manual says 6BL8, ECF80, 6C16, 7463 are all equivalent

Cheers,
Ian
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Old 20th October 2006, 02:53 AM   #3
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Hi richwalters ,

I strongly recommend the use of the cheap 6AN8 , a
med-mu triode / sharp cut-off pentode ( like 6BL8 / ECF80 )
with minor changes in resistors values , the high-quality
sound will surprise you .

Don’t forget that David Hafler , used the 6AN8 in the DYNACO
Mk II , and later he changed the 6AN8 for the 7199 , in the
STEREO 70 model , but the circuit topology remains the same.

Regards ,

Carlos
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Old 20th October 2006, 07:00 AM   #4
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Thanks all for replies......I would add that the orig appl note on the 7199 (somewhere in Ned's triode electronics dusty files) mentioned the (wretched) sensitive g2 setup for min distortion. Indeed this is a pain for most pentodes. In every case I find g2 needs to be roughly 1/3 of anode volts (10M dig meter on pin) and with both nos 7199 and ECF82 is much more critical. The ECF80 g2 voltage can be varied much more without detriment to thd.

In my early days my books mention med/high mu triodes over 40 were not for advised for split load phasesplitter apps.......low mu triode sections make better signal handling capability esp in split load functions......nowadays yes/no ???

richj
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Old 20th October 2006, 08:40 AM   #5
gianis is offline gianis  Greece
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Default ecf80

a schematic with 6bl8 / ecf80..
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Old 20th October 2006, 08:42 AM   #6
gianis is offline gianis  Greece
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Default ecf80

Sorry too large file..
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Old 20th October 2006, 02:09 PM   #7
bembel is offline bembel  Europe
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Hi all,

I have settled two ECF80 (NOS Mazda) since a few days in my Dynaco ST70 chinese clone (in place of the chinese 6F2 that looks like ECF82).
Sound is good.
I found filaments were too hots in 6F2 (2 tube alone on a 4ADC supply) with ECF80 the problem didn't occur (just inrush current & then color is nice, whilst chinese tubes were bright clear orange.)
No problems for now.

Hope this helps
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Old 20th October 2006, 06:15 PM   #8
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The 7199 is fast becoming a collectors item and for a few bucks the ECF80 can do a better job. I find the pentode gain sim but the tube likes a touch more current. I’ve enclosed a diag of the front end of my 150W amp which uses it. The pentode g2 is the single setup problem area and despite other configurations, the orig with discrete resistors performed the best.
Swapping the 7199 for ECF80 plus some surgury gives virtually identical stage performance, pentode 43dB and slight drop in cathode resistor value. The rest is standard amplifier building. An ECL82 pentode configured as triode self balancing voltage follower with feedback Doing the math; assume front end stage gain of 40dB the ECL82 stage gain of about 16dB. For input of 70mV will give 50V+50VRMS driving p-p parallel o/p stage at 530V will give around 140W+. Going for higher driver gain isn’t desirable with this type of circuit if one wants to keep the noise floor at –75dB down with 20dB NFB...(Vin then becomes 0.7V) Going for a 12BY7 (a brilliant tube) would only enhance the 1st stage pentode noise (10dB worse) and require even more NFB to counteract. The values shown for 1st stage snubber and interstage cap value of 8n2 are for good output transformer quality... NFB has to be increased to 36dB before hints of LF instability. This drastic increase is a good test of any tube amp.
SOme have queried the use of an ECL82 as a driver. True, this tube in triode config has rather bad curves...( I get far less thd from these than from a 6SN7 in sim circuit) and as I have several ECL82 ..I’m using ‚em. I’ve also used the med high mu triode section as a see-saw phasesplitter.....but the performance was disappointing as the two halves due to layout are some distance apart, which ruins the HF into high thd. By all merit the split load phase-splitter in one tube offers about the best for what one gets for the price.
On audio listening the split-load HF performance with the balanced voltage driver offers about the best hi-fi performance vs. simplicity and cost. Comparing this with another amp that uses the see-saw phase-splitter, the top end notes sounded quite „raspy“ especially cymbals coming through as a tizzle this due to the thd from the HF misbalance which it creates.

richj
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Old 20th October 2006, 06:38 PM   #9
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Bit better image.

richj
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Old 21st October 2006, 02:45 AM   #10
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Rich,

Your work suggests that the 6BL8/ECF80 is somewhat easier to use than the 6U8/ECF82. That I will not dispute. However, think about NOS RCA 7059s. The 7059 is an inexpensive automotive variant of the 6U8, with a "12" V. heater. That's not a bad way to add RCA "chime" to the total voicing package.
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