I recently bought a small 5W valve amp from gear4music and, at certain settings, sounds ok. It's identical to the HB Tube5 which gets decent reviews. At £118 delivered it was worth a punt.
However, overall I wasn't particularly impressed with the sound, although it's 50 years since I regularly used (bigger) valve amps. Sounds a bit flat unless I turn the volume way up.
So, I tried using it with my ultra-cheap EQ pedal from Thomann and it transforms the amp into a superb sounding monster. Is there a simple explanation for this? Without using the pedal, is there a way to modify the stock EQ?
Comments
Even if you’re using the pedal to cut, modifying the amp circuit to be more selective in the frequencies it shelves is probably going to be more hassle than it’s worth with the existing PCB.
Cheap as it is, that EQ pedal will be a far more sophisticated circuit than anything in the amp’s tone network.
https://i.postimg.cc/NFNS6tCp/EQ-Pic.jpg
I found a schematic for the HB Tube5. It’s superficially similar to the 5F1 tweed Champ but has a 10uF bypass capacitor added to the cathode bias resistor on the first gain stage. Maybe suggests the designers were trying to increase gain in the higher frequencies to compensate for the small speaker ‘woofiness’, a bit like your EQ settings.
Yeah, it works great with the pedal. The transformation is so pronounced that I wonder why they don't incorporate a better EQ when they make these little amps. Cost, I guess?
Anyway, thanks for all the replies.
Then I guess you'd want a smidge more power, so changing the output stage to a pair of 6V6s in push-pull would do the trick. Add a reverb and trem and you've got a Princeton. More money.
It might be interesting to make the existing amp into some sort of hybrid - keep as is but add an active EQ. Then you'd need regulators for the +/-5VDC opamp rails etc. which would add a bit, but that stuff's cheap compared with making bigger cabinets and adding larger speakers.
I guess with the proliferation of cheap modellers like the Nux and Yamaha THRs there'd be no market for it.
Any guitar-related marital disharmony in my gaff is less the noise, more the number of similar-looking large black boxes cluttering up the place
I’m tempted by one of these - I don’t need one, but…
https://images.app.goo.gl/6NURsKEwJGwxoh9g7
None of this is what you'd call mad high gain stuff, but they've gone to the effort nonetheless of adding a snubber to the second gain stage. I can't imagine they were having massive problems with oscillation? Also that's going to knock a bit of treble off, maybe that was the idea.
I'd like to have been in the room when they were designing this thing, genuinely interested in the thought process.
I always write these posts in the knowledge that the time-served amp guys on here will put me straight if needs be, I've learned quite a bit that way
This circuit I just find ever so slightly odd - they deliberately pass high frequencies with a bright cap on the volume pot, then immediately after, add that snubber cap in parallel with the plate load on the second stage which is going to take some high frequency back out again. Just wonder about the thinking, there was obviously a reason.
And yeah, I don't think I've used a 'low' input on any amp ever
Had some buzzing so arranged a replacement.