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Post by Deleted on Sept 23, 2021 0:00:30 GMT
I happened to see this when I was perusing an email from the company I recently bought some cables from. It was the first time I was aware that the company sold musical gear so I was interested. To be honest, I'm not in the market for another amp and I'm not thinking of buying it, but I was intrigued because it seems to be in the same general class as the Fender Champ. This amp's a single-ended 5 watt tube amp with a 12AX7 and a 6V6GT, and an 8" Celestion speaker. From reading customer reviews, comments indicate that the amp's clean at low volume, but tends to get overdriven when it's dimed, and a common reaction is that it runs out of headroom very abruptly. What puzzles me is one owner's remark that if you substitute a 5751 for the 12AX7 preamp tube, that headroom improves dramatically. I understand that a 5751 is a lower gain preamp tube, so it stands to reason that when the amp's turned up, it'll sound cleaner than it did when being driven harder by a 12AX7. What I'm puzzled about is the comment that clean headroom improves dramatically with a lower gain preamp tube. Am I missing something here? My thoughts are that the amp might be cleaner but lower in volume when it's dimed with a low gain preamp tube, but I'm having trouble with the idea that somehow dynamic range is extended by it.
Regardless of that, this seems like it would be a cool little bedroom amp for a couple of hundred bucks. It has a 1 watt/5 watt switch and the 8" Celestion is said to be quite smooth after the initial break-in period.
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Post by highdeaf on Oct 3, 2021 16:57:43 GMT
There's so much misused nomenclature in the MI world, that's what you're seeing here.
You are correct in that a lower gain preamp tube will not increase 'amp' headroom. It decreases gain in the early stage of the amp, so it can never hit the power amp as hard. If they are cascading one stage of the 12AX7 into the second, then the gain from the 1st to 2nd stage is also decreased, again meaning less distortion. Nothing to do with headroom, which is mostly a power amp characteristic.
Five watts from a 6V6 is about average (so not underdriven like a 6L6 would be at the same power rating). Sometimes, that lack of headroom is desirable, if you like to push the power amp at reasonable (not quiet) levels. Five watts into a 100dB/1w*1m speaker will still produce 106+ dB three feet away from the amp, before it even starts to clip. That's still pretty loud but workable in some situations.
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