Choke for 60 watts amp ?

[Rod]

Hi!

What choke would you recommend for a Engl screamer 60 Watt amp? I wan to add more tight low ends.

Thanks.

[pdf64]

What is the current screen supply arrangement (schematic)?
Pete

[Rod]

Hi Pete!

I only have the preamp attached schematic.

[J M Fahey]

I wan to add more tight low ends.

1) who told you that's the way to do it?
2) does it have a choke now? How does it feed the screens?
Yea, basically Pete's question, but even without a schematic, you can look and see whether it has a choke or not.

EDIT: just checked: ENGL SCREAMER-50 SCH Service Manual free download, schematics, eeprom, repair info for electronics
It does not have a choke, you can add one if you wish, but the

add more tight low ends

will be *much* less than you imagine, if any.
Those screens already have 470 ohms each, anyway, so replacing the 470 ohms filtering resistor with the, say, 40 to 60 ohms a choke has, won't be *that* different.
More of a Forum thing than real practical difference.

[pdf64]

Thanks for the schematic JM.
Agree, a friend with a Traynor YB1A asked me to fit a Marshall type choke to replace the 470 ohm resistor, equivilant to R70 in the Engl.
I admit that the internet 'received wisdom' / BS had led me also to expect all sorts of improvement.
The reality was that there was no difference, on the bench the max clean and overdriven power outputs were the same, and there was no discernable audible difference, even using a G12H equipped 4x12.
On the bench there was less Vac ripple voltage at the screen grid power supply node with the choke, so it's technically 'better' but that didn't benefit the audio output.
Pete

[Chuck H]

Looking at the schematic I'd say that nothing you do to the power amp will help the low end definition. Maybe I'm out on a limb here, but I seriously doubt anyone is overdriving the power tubes in these amps. The signal is so processed by the time it gets to the power tube grids that any further clipping would be pedantic. Tighter low end in amps where the preamp is the clipper and the power tubes are just serving reference duty are usually best modded at the preamp for tighter lows. More lows is a matter of speaker choice and output power in this case. But tighter lows means trimming fudge out of the preamp.

[big_teee]

I thought the main Purpose of Chokes and Caps, was to filter the Ripple.
Clean up the B+.
IMO I would tune it, in other areas.
Like maybe Coupling Cap Values.
But, I am no expert!

[Chuck H]

Yup. Smaller coupling cap and cathode bypass cap values in spots. Then fire it up into a 4X12 with G12H Anni's. Big, tight shred monkey tone all up in yer face.

[Tage]

I agree on the coupling cap reduction, engl preamps have some big caps, i.e. all the 47n coupling caps, wich could all be reduced to around 10n or less and really cut the mud out, also the tone stack could be trimmed a bit. Although eventually it might be getting very far from what engl had intended...

But hey put in any choke that can deliver the current the screens need, at least 100ma rated, if you wanna spend mercury has chokes with tons of taps for differing inductance values, you can hook up different ones and see if increasing the inductance actually changes the tone! then report back to us

I think your money might be better spent on some good reading material like Merlins preamps book or a couple TUT books.

[kleuck]

In simple (tweeds or the like) amps, a choke can improve power, make the amp more "stiff" (not necessarily what you want) and improve the lows slightly, though a bigger cap would be a better solution.
In simple amps the power line is actually the main part of the sound imho, not with modern ones.

[exclamationmark]

IIRC engl's always uses a 47n coupling cap for the channel switching features, but the high gain section uses something like 1n and 680/470p caps into fairly small loads, in series with the 47n caps, essentially ignoring any effect the 47n cap has. Literally every engl amp I've looked at uses this type of scheme for the pre-amp. But they sound killer A lot of hi-fi guys swear by using choke loads because it gives them better transient response... but then again, these are hi-fi nuts.