Hi there,
I'm new to the whole tube story, but I just wanted to give it a try. While I was researching all around, discovering the abyss of output transformers and their costs I stumpled over power guitar amplifiers.
To be specific the Engl Tube Poweramp 840/50.
It's using 6L6 as PP in the output, all composed in a 2HU 19" case.
All that for €500 in good used condition.
To the ones who know: To me the OTPs seem a little small for 50Watts of output power and above all, simple EI cores.
What is to expect from them? Are those instrument amplifiers even specified for (almost) Hifi, so roughly 20Hz to 16Khz?
Could that be a good basis over all the chinese amplifier kits?
Or are the OTPs not up to the HiFi job?
BR, Markus
P.S.: I'd have no worries about the fan 😉
I'm new to the whole tube story, but I just wanted to give it a try. While I was researching all around, discovering the abyss of output transformers and their costs I stumpled over power guitar amplifiers.
To be specific the Engl Tube Poweramp 840/50.
It's using 6L6 as PP in the output, all composed in a 2HU 19" case.
All that for €500 in good used condition.
To the ones who know: To me the OTPs seem a little small for 50Watts of output power and above all, simple EI cores.
What is to expect from them? Are those instrument amplifiers even specified for (almost) Hifi, so roughly 20Hz to 16Khz?
Could that be a good basis over all the chinese amplifier kits?
Or are the OTPs not up to the HiFi job?
BR, Markus
P.S.: I'd have no worries about the fan 😉
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Looks like a bad idea to me. Who wants a guitar amp working linearly from 20Hz ~ 20kHz? Nobody.
HiFi-amplification != guitar amplification.
And, btw, this is a mono amp as well.
HiFi-amplification != guitar amplification.
And, btw, this is a mono amp as well.
OK, so I take your message as if the OTP probably won't do 100Hz -3dB ?
It's a stereo btw....
Edit: Sorry, I mean OutPutTransformers = OPT
It's a stereo btw....
Edit: Sorry, I mean OutPutTransformers = OPT
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I understand guitar amps are designed to have a limited freq response range, a non-flat freq response and to generate distortion. The OPT is usually undersized to reduce weight, reduce cost and help produce some distortion to boot. The premise of a modern guitar amp is the antithesis to a hi fi amp. It’s mayb3 possible to mangle a hi fi amp into a guitar amp but there’s no sensible path the other way around.
Alright, yeah, I did some calculations... They where not in the favor to the Engl... Although, at the cost of assembling time... But who knows how long these lockdowns will last 😉
Grrr... I'd bet that amp would sound very nice with some "Viecher"-hornloaded widebands. On the other hand, that wouldn't be seriously called "HiFi" =)
Grrr... I'd bet that amp would sound very nice with some "Viecher"-hornloaded widebands. On the other hand, that wouldn't be seriously called "HiFi" =)
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The OPTs are probably the most important part of a tube amp, but good OPTs can be had for €70, if you shop around, and you can probably buy a full set pf transformers for not much over €200.
There are plenty of kits where you can build on a PCB, bolt everything together, and build a decent sounding amp for a bit under that €500 price you mentioned.
One option is the Baby Huey EL34, which would have a similar power output to the amp you are looking at.
What stage are you at? Weighing up the options, or do you have one of those guitar amps to adapt?
There are plenty of kits where you can build on a PCB, bolt everything together, and build a decent sounding amp for a bit under that €500 price you mentioned.
One option is the Baby Huey EL34, which would have a similar power output to the amp you are looking at.
What stage are you at? Weighing up the options, or do you have one of those guitar amps to adapt?
Low note on guitar is 82Hz. And distortion IS allowed: a guitar speaker won't project 82Hz nearly as well as its harmonics. Harmonics add music emphasis to the dull tone of a naked steel string. The Engl player would surely work with a bassist, who dominates the tone up to ~~250Hz. So the guitar OTs can be much smaller and lighter than a "hi-fi" claimed to be "perfect" to 20Hz (more likely 45hz).
That said: I've had much enjoyment using good stage amps for playback.
That said: I've had much enjoyment using good stage amps for playback.
Markus,
You can employ the "tricks" we relied on, at the start of the "El Cheapo" project to squeeze OK, if unspectacular, performance out of the O/P "iron". The provided graphic shows Fender "Deluxe" replacement stuff.
Triode wire the O/P tubes and bandwidth limit bass extension at the I/P of the circuitry.
Those O/P tubes are probably 6L6GC or KT66 specimens. If they test strong, they can be sold for a few €. Passing less power into the O/P "iron" to improve its bass performance is necessary and moving down in the 6L6 family to Russian 6Π3C-E (6p3s-e) stock, a 5881 equivalent, seems good to me.
Tried and very true Mullard style topology would fill the small signal circuitry requirement, while exploiting the 3 Noval sockets.
You can employ the "tricks" we relied on, at the start of the "El Cheapo" project to squeeze OK, if unspectacular, performance out of the O/P "iron". The provided graphic shows Fender "Deluxe" replacement stuff.
Triode wire the O/P tubes and bandwidth limit bass extension at the I/P of the circuitry.
Those O/P tubes are probably 6L6GC or KT66 specimens. If they test strong, they can be sold for a few €. Passing less power into the O/P "iron" to improve its bass performance is necessary and moving down in the 6L6 family to Russian 6Π3C-E (6p3s-e) stock, a 5881 equivalent, seems good to me.
Tried and very true Mullard style topology would fill the small signal circuitry requirement, while exploiting the 3 Noval sockets.
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The Engl output transformers are tiny even in guitar amplifier terms. My younger son has got a Fireball 60. When I opened it by chance, I stumbled over it's OT that is small even if it were for a pair of EL84's in hifi use.
But there are/were guitar amps as well with OT's that were apt for hifi use as well. Hiwatt bought their Partridge transformers right from the manufacturer's hifi and studio equipment line. The early DR103 OT's even featured a 100 V line secondary.
Best regards!
But there are/were guitar amps as well with OT's that were apt for hifi use as well. Hiwatt bought their Partridge transformers right from the manufacturer's hifi and studio equipment line. The early DR103 OT's even featured a 100 V line secondary.
Best regards!
Definitely use triode wired 6Π3C-E "finals", to obtain reasonable bass extension. FWIW, the lowest note a "standard" double bass makes is 41 Hz.
Engl have the smallest OPTs in that range.
It is also true that the cut alot on lows to give definition to the amount if gain they have.
I don't see the gain in buying it as a (ugly) hi-fi base.
I'd go for an Hammond wooden/steel chassis and some standard trafos.
Then a kit bought on this forum (to get tons of help) and that's it.
It is also true that the cut alot on lows to give definition to the amount if gain they have.
I don't see the gain in buying it as a (ugly) hi-fi base.
I'd go for an Hammond wooden/steel chassis and some standard trafos.
Then a kit bought on this forum (to get tons of help) and that's it.
Well, thanks for all your thoughts. Its a pity that a decent OPT would probably not fit inside a 2HU case.
I wouldn't mind the factory input stage, that I'd probably replace by some kind of aikido + phase inverter.
Personally I'd prefer the look and design of the named amp much more than any of these old-school "tower" design that fully-tubed amplifiers usually sport. I can't stand visible and touchable transformers, kind of weird....
I wouldn't mind the factory input stage, that I'd probably replace by some kind of aikido + phase inverter.
Personally I'd prefer the look and design of the named amp much more than any of these old-school "tower" design that fully-tubed amplifiers usually sport. I can't stand visible and touchable transformers, kind of weird....
Toroid OPT’s could well fit inside a 2HU case (88 mm). Look for example at Toroidy’s toroids.
Regards, Gerrit
Regards, Gerrit
Look here. Toroidy's offerings seem to be a fixed 80 mm. in height. That's a very tight squeeze into 88 mm., when mounting hardware is taken into account. A possible solution to the problem would be a cosmetically attractive "acorn" nut on the outside of the enclosure.
I know it’s tight, but it could work. Measure carefully the exact inside dimensions of the casing before purchasing to be sure.
Regards, Gerrit
Regards, Gerrit