The 6BM8/ECL82 is nice tube for making low power amps.
IMO, the circuit shown leaves much to be desired. It uses full pentode mode and no NFB. Can you say IM distortion and a wretched damping factor?
Contact member Jeff Yourison for the particlulars of the "Dirt Cheap SE" project he and I worked on. We tweaked an old Mullard design and the result deals with the issues outlined above and more.
IMO, the circuit shown leaves much to be desired. It uses full pentode mode and no NFB. Can you say IM distortion and a wretched damping factor?
Contact member Jeff Yourison for the particlulars of the "Dirt Cheap SE" project he and I worked on. We tweaked an old Mullard design and the result deals with the issues outlined above and more.
Three Watt Economcal Stereophonic Amplifier
You can't go much wrong with this. Just a few little tweaks and the ECL82 could be used instead of the ECL86.
Regards,
James.
You can't go much wrong with this. Just a few little tweaks and the ECL82 could be used instead of the ECL86.
Regards,
James.
Sure. A series resistor from the secondary of the output transformer to the cathode of the triode. You may need to reverse the connections to the secondary to assure that you're getting negative feedback rather than positive feedback.
It may not be the ultimate amplifier but it would be worth a try.
It may not be the ultimate amplifier but it would be worth a try.
Enric,
That much money is in the range of a scratch built "El Cheapo". Magnetics are always the big ticket items. So, let's start with budget O/P trafos. Edcor's $37.01 model GXPP15-6-8K will give satisfactory results into both 4 and 8 Ω speakers. You will be restricted to triode mode "finals", as the magnetic headroom necessary to employ ultralinear (UL) mode is absent. The power yield is approx. 6 WPC, which works well combined with mid 90s sensitive speakers.
IIRC, the "Aikido" preamp has some gain. That means you get to "ditch" the volume control circuitry and switch to the inexpensive 6J6 as the splitter driver.
BTW, any member of the 6V6 "clan" works with the parts values shown. "Obscure" tubes other than the 'AQ5 include the 12AB5 and 14C5.
Attachments
Einric
Look at this before you make up your mind.
Kit - Stereo Integrated Tube Amplifier | Antique Electronic Supply LLC
Look at this before you make up your mind.
Kit - Stereo Integrated Tube Amplifier | Antique Electronic Supply LLC
If you are going to consider that, you might consider 2 of these instead: K-501 Monoblock Tube Amplifier
dave
Is this schematic as you modified it Eli? I had this on my hard drive...
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[IMG=http://img214.imageshack.us/img214/7086/dirtcheap6bm8.jpg][/IMG]
An externally hosted image should be here but it was not working when we last tested it.
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[IMG=http://img214.imageshack.us/img214/7086/dirtcheap6bm8.jpg][/IMG]
I just sent an inquiry to them about a pair of K-501's to see if they would offer them without power and output transformers.
The ones they supply are kinda fugly.
But, I love the simplicity of that circuit.
Are there any suitable replacements for the 11BM8? There doesn't seem to be much info out there about them.
The ones they supply are kinda fugly.
But, I love the simplicity of that circuit.
Are there any suitable replacements for the 11BM8? There doesn't seem to be much info out there about them.
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Not wanting to thread-jack, but some other low power simple projects you may want to consider:
I built this http://www.diyaudio.com/forums/tubes-valves/113917-new-se-6p15p-project.html based on this design Flea-Power 6N1P - 6P14P SET Amplifier with PIO caps
Also, Decware Zen used to have the schematic on their web site, but now it is a PC kit. Schematic is:
I built this http://www.diyaudio.com/forums/tubes-valves/113917-new-se-6p15p-project.html based on this design Flea-Power 6N1P - 6P14P SET Amplifier with PIO caps
An externally hosted image should be here but it was not working when we last tested it.
Also, Decware Zen used to have the schematic on their web site, but now it is a PC kit. Schematic is:
Seems to me that a single 6BM8 might benefit from an RH treatment. Look up Alex's RH84 which uses 1/2 a 12AT7 and an EL84.
The triode in the 6BM8 is almost identical to 1/2 a 12AT7 and the 6BM8 pentode section is a bit like a lower power EL84 (well more like a lower power 6V6 or 6AQ5).
This may have been done before - anyone know?
Cheers,
Ian
The triode in the 6BM8 is almost identical to 1/2 a 12AT7 and the 6BM8 pentode section is a bit like a lower power EL84 (well more like a lower power 6V6 or 6AQ5).
This may have been done before - anyone know?
Cheers,
Ian
Hey Ian,
What makes you think this particular triode likes a close to vertical loadline? If wanting to go Schade it would be better to dump the triode alltogether and use a MOSFET driver ala Michael Koster for low distortion.
If using an ECL86 it could maybe be worth a try to do a SE-Huey, as that tube is 1/2 ECC83 plus a 9W EL84.
What makes you think this particular triode likes a close to vertical loadline
? If wanting to go Schade it would be better to dump the triode alltogether and use a MOSFET driver ala Michael Koster for low distortion.If using an ECL86 it could maybe be worth a try to do a SE-Huey, as that tube is 1/2 ECC83 plus a 9W EL84
.Yes, that's the 1st iteration that I came up with. IIRC, Jeff Yourison has a neater and "final" diagram. Like "El Cheapo", the history of the "Dirt Cheap SE" was lost in the "hacking" of the AudiophileTalk site.
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