Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: birt on December 30, 2015, 07:53:42 am
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I've been looking to reuse the iron of a PP ECL800 amp. (a single tube with triode PI and 2 pentodes for about 9W PP)
the datasheet of the tube tells me it uses a 11K OT but i'm not sure if that is for 1 pentode or for 2.
it's probably very obvious but i'm a bit confused here.
what output tube options do i have when i use my transformers in a new project? (and maybe some extra heater juice)
i was thinking maybe ECL80 in PP?
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I read on the Lorenz data sheet Ra-a is 10K at 250VDC. I would think if you are running voltages ~300VDC, this would open up lots of possible tubes. It was common for Hammond (Organ Company) to use 6v6 with 10K to the 8ohms. Also Zenith used EL84's with a 10K primary for their consumer console amps. I am not 100% sure. but I think the tube is the same as ECL80 with a internal driver.
Compactron tube with a driver and 2 Output Pentodes. I believe you would have plenty of options. Check out page 42 of this: http://www.americanradiohistory.com/Archive-Electronics-Illustrated/Electronics-Illustrated-1964-07.pdf (http://www.americanradiohistory.com/Archive-Electronics-Illustrated/Electronics-Illustrated-1964-07.pdf)
I believe it will give you all the info you would want to know about the use of the ECLL800 since it is a build using the tube and you can get all the specs.
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You can use the OT with a pair of EL95 tubes in PP
the EL95 is the single pentode vorsion of ELL80 (2 x pentode tube), the ECLL80, if I remember correctly, is an ELL80 plus a triode
Franco
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You can use the OT with a pair of EL95 tubes in PP
the EL95 is the single pentode vorsion of ELL80 (2 x pentode tube), the ECLL80, if I remember correctly, is an ELL80 plus a triode
Franco
well i thought so as well but i can't find confirmation anywhere that the pentodes of ELL80 and ECLL800 are the same.
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On this datasheet you can see the ECLL800 tube in PP at 250v class AB need a 11k aa OT for 8.5W output
http://tdsl.duncanamps.com/link.php?target=C8259F25 (http://tdsl.duncanamps.com/link.php?target=C8259F25)
On this datasheet you can see the ELL80 tube in PP at 250v class AB need a 11k aa OT for 8.5W output
http://tdsl.duncanamps.com/link.php?target=0025A2EE (http://tdsl.duncanamps.com/link.php?target=0025A2EE)
On this datasheet you can see the ECLL80 tube in PP at 250v class AB need a 11k aa OT for 8.5W output
http://tdsl.duncanamps.com/link.php?target=C8259F25 (http://tdsl.duncanamps.com/link.php?target=C8259F25)
On this datasheet you can see the EL95 tube in PP at 250v class AB need a 10k aa OT for 7W output
http://tdsl.duncanamps.com/link.php?target=2C259BDC (http://tdsl.duncanamps.com/link.php?target=2C259BDC)
Not exactly the same performance and OT request but very similar to the ELL80 & ECLL80
Also a pair of 6AQ5 tubes can be used with that OT
http://tdsl.duncanamps.com/link.php?target=09259DBB (http://tdsl.duncanamps.com/link.php?target=09259DBB)
Franco
p.s.: I forgot, give a control to the OT you recovered to define the effective primary impedance
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ECLL800 makes no sense except as a push-pull amp.
The sheet suggests 250V at 10K or 11K load.
Since ECLL800 is unobtainable now, but the iron survives, you want a tube(s) to suit. 6V6, EL84 are suitable. Bigger than you need for 9 Watts/pair, but readily available and won't be strained.
> confirmation anywhere that the pentodes of ELL80 and ECLL800 are the same.
They are probably very similar. Philips rang-up multiple variants on the same guts with different gain factors. But the main thing is: tubes is tubes. If it is generally "the same size of a dog", it can be made to work. Sending a beagle to do a corgi's work, that's more dog than you need, but a beagle can turn a corgi's dog-wheel.
6V6 has a sheet condition for about 250V and 10K load; 10K, 11K, who can tell?
EL84 does not bother with 250V 10K, but suggests 8K. Worked into 10K-11K it will give 72%-80% of sheet power, and you can run the bias 20% colder to save heat.
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ECLL80 is close to 6BM8/ECL82. i'd use those. ECLL80 is 6W plate diss. 6BM8/ECL82 is 7W.
something else to consider: what wire gauge was used in those transformers? will they handle current of P-P 6V6/EL84 at 300V?
just my 2cents...
--pete
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ECL82 looks like a good choice. i'll have to add some more heater current but that's ok.
i looked at a datasheet and it seems ok with 10K as well.
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still looking at the ECL80 as well since i have a bunch of those and the heater current is just 300mA.
i can get about 3W PP and it should work well with the OT i have. this will make it a very low watt amp though.
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another suggestion:
use a pair of EL95/6DL5: they're still relatively inexpensive and available NOS. a pair come in at 400mA heater draw and within required total heater budget of a single ECLL800 which is 600mA. for the driver, use a sub-miniature 5719 or a 7 pin miniature 6AB4 single triode for phase inverter and you're total system heater draw is under budget by 50mA.
spec-wise the EL95 are about a very close match to the ECLL800 power pentodes. S is 5mA/V on EL95 and is 6 mA/V for ECLL80; Pdiss is 6W for both.
if you look at the spec sheet for the ECLL800, the triode has a very low mu: 1.2. i think the triode was meant to be used as a split-load (cathodyne/concertina) phase inverter.
--pete
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I agree with Pete
a tube you can use as pre is a 6ak5 (filament 175mA) or an ef86 (filament 200mA) or a 5879 only 150mA for filament
if you have not enough current for the heaters to supply a PI you can think to build a PP section without PI if you are comfortable with a low power output
(give a look to the link)
https://www.ampbooks.com/mobile/amp-technology/6L6-phase-inverter/ (https://www.ampbooks.com/mobile/amp-technology/6L6-phase-inverter/)
Franco
p.s.: I assumed you have 600 mA of current available for the heaters ..... but ... is so or you have more ??
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the amp has an ECLL800, 12AX7 and EZ81. but heater current is no problem at all, i can add a little 6V transformer.
the reason i wasn't looking at the EL93 (which is the logical first option) is because i don't have any.
i do have loads of ecl80 and some ecl82. for the preamp i'll try something with another tube i have in abundance, like ECF83 or ECF80 for example :-)
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>>> p.s.: I assumed you have 600 mA of current available for the heaters ..... but ... is so or you have more ??
i assumed he wanted to replace the same number of components with available parts and remain within the allotted 600mA heater draw for the three components. i had a hunch there were more gain stages since the one bottle is not necessarily a complete amplifier.
>>> the reason i wasn't looking at the EL93...
is there such a tube? i can't seem to find data on an EL93.... link?
--pete
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I think he mean EL95 ....
With the ecl82 you have many options
Gibson GA8T
(http://www.drtube.com/schematics/gibson/ga-8t.gif)
Univox U45B
(http://music-electronics-forum.com/attachments/3324d1225222064-u45_orig.jpg)
Watkins Westmister
(http://www.vintagehofner.co.uk/britamps/watkins/schematics/west10wschem.jpg)
And others
Franco
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>>> p.s.: I assumed you have 600 mA of current available for the heaters ..... but ... is so or you have more ??
i assumed he wanted to replace the same number of components with available parts and remain within the allotted 600mA heater draw for the three components. i had a hunch there were more gain stages since the one bottle is not necessarily a complete amplifier.
>>> the reason i wasn't looking at the EL93...
is there such a tube? i can't seem to find data on an EL93.... link?
--pete
sorry EL95 :-)
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> ECLL800, the triode has a very low mu: 1.2. i think the triode was meant to be used as a split-load (cathodyne/concertina) phase inverter.
No, that would give significantly unbalanced outputs.
If you just wire it as a "voltage amplifier", the mu of 1.2 degrades to effective gain very close to ONE. Negative one counting polarity. So if you have a driver and one power pentode, want a PP output, this tacks-in, taps the existing drive, inverts it, and drives the second power pentode.
http://www.radiomuseum.org/images/tubeenvdiag_klein/ecll800.png (http://www.radiomuseum.org/images/tubeenvdiag_klein/ecll800.png)
In fact, Tg1 is hard wired to P1g1. And all three cathodes are common. And triode Gm is very tiny. There's hardly any choice. (Nor any reason you should know this; it is a very odd obscure duck.)
But all moot because ECLL800 is too valuable to play with.
And if you are not up-marketing your 1958 Radio 500 into a new/improved for 1959 Radio 600, you can find better ways to do a push-pull output.
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I've just find this Hagstrom mod 310 schematic
an ECLL800 guitar amp, I post it just for connoissance
(http://edgaraudio.se/tubes/Hagstrom/Renovera310-filer/310.jpg)
(http://www.gbmusic.co.uk/GBHire/hire/Hag310TWEED.jpg)
Hangtrom has build also other amps for guitar and bass with the ECLL800 tube
(http://elektrotanya.com/PREVIEWS/63463243/23432455/hagstrom/hagstrom_210-bass_sch.pdf_1.png)
(http://www.hagstrom.org.uk/images/Visitors/Graeder/210amp/b210--0003_1_1.JPG)
Franco