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Discussion in 'The Stomp Box' started by David Meiland, Nov 21, 2020.
Go on then, I’ll be ‘that guy’: Yamaha THR10
I have never seen the need for anything like that. I play nearly always at home and at volumes no louder than normal speaking volume (or less). I can easily hear TV dialog while playing, yet my guitar sounds nice, clean and clear to me.
So today I built this 33/10 ohm fixed-resistor attenuator. It cuts the 6V6 output down to where it's almost quiet enough for the bedroom with all Plexi knobs dimed. When followed by the Realistic L-pad to bring it down a smidge more there's no noticeable treble loss and to my ears it's as good as the Weber Mini-mass for a fraction of the cost. Subbing the 33 ohm with a 50 should get the max loudness just right and will only bring the input impedance up to 8.5 ohms, more or less.
Just make sure you know your own desires and preferences. Because it comes down to a simple but important question: what is it about playing with your amp turned up that makes you happy?
If it's the way your amp responds when the amp is being pushed--the compression, the response--then an attenuator is a good investment. You'll get more of that compression and response at a lower volume.
But for many people, it's not the tone that they love. It's the volume. Or more precisely, it's the way you perceive that tone and the playing experience at higher volume. This is the whole Fletcher-Munson thing: how you hear frequences changes as the volume goes up. And there's the whole full-body experience of playing at volume. If that's what you love and are responding to, then any attenuator, no matter how good it is, will satisfy you.
Most people who dislike attenuators dislike them because they conflate these two things. But the distinction really matters. So if you decide to buy an attenuator, just make sure that you're after the former and not the latter.
Those simple two resistor attenuators from Rob Robinette are interesting and are the right way to do a simple version. The key thing is the resistor in series with the speaker, then the parallel resistor to correct the ohms seen by the amp. The series resistor makes sure the speaker sees a high resistance, which mimics the relatively high output impedance if a tube amp, particularly one with no NFB, letting the speaker react accordingly.
You can stack these stages end to end, keeping a consistent output impedances and input imoedance. Do this and basic tone remains intact. Ive built resistive attenuators with three such stages.
What you lose though is the dynamic response of the amp reacting to a reactive load, at different levels of drive. This is a more subtle effect, the basic tones are still ok but it too can be fixed.
My thread on the Marshall forum has a series of designs that keep the tone of the amp at all levels. Each one is developed from a basic two-resistor circuit, very much like RR's, but as a multiple of switched stages with a reactive front end.
Design M2 is linked near the top of the first post.
I had a 20w Marshall Origin going into a 2x12... for apartment use. Serious overkill so I bought a JHS Black Box volume control to go into the effects loop. Hated it... made everything fizzy and drained the tone.
Switched to a 5w Supro Blues King 10 and never been happier.