|
Post by mazzer on Jan 4, 2019 4:53:31 GMT -7
Hello all,
I recently bought a Maz18NR mk2. Great tones, very happy with it. But since my band rehearsals are in a (rather small) studio (and live I always mic the cab), I found the stock amp too loud. I experimented with attenuators, but still prefer the ‘direct’ tone from an amp. Long story short: I put a 12AU7(A) (TAD Premium) in V1. I LOVE the tonal result: much less volume, cleaner, same great response - and I get to turn up both Volume and Master without going deaf (currently both around 10 0’ clock, producing about 89-90 dB at 1m from speaker). BUT, here’s my question: will a 12AU7 in V1 cause any unwanted side-effects? Will it require some kind of xtra care?
Thank you all, Mazzer
|
|
|
Post by premiumplus (Dave) on Jan 4, 2019 8:59:06 GMT -7
Welcome to Z-Talk, it's full of great people and lots of goodness. Re the 12AU7, it won't hurt a thing. It's basically just a very low gain version of a 12AX7.
|
|
|
Post by DRZ on Jan 4, 2019 9:05:22 GMT -7
In the MAZ 18 MKII a 12AU7 in v1 should not cause any electronic issues. A 12AU7 is a currant source device, that is it will drive a signal very well with little or no increase in amplitude or gain, that is why you like it in the V1 position. The only concern with that tube used in a 12AX7 circuit design is Cathode Currant draw, which is higher on a 12AU7 .
The MAZ 18 NR MKII uses a parallel triode connection and the Cathode Resistor is 1.2K which is on the high side of biasing a 12AX7 so you'll be safe with a 12AU7. A little over your head info, in a Parallel Triode connection you half the value of plate resistor and half the cathode resistor. Using a 1.2 K cathode resistor in this configuration is equal to a single 2.4K cathode resistor , which is what is normally used on a 12AU7. There did totally confuse you by explaining that ?
Z
|
|
|
Post by Chilly Gibbons (Todd T.) on Jan 4, 2019 9:23:34 GMT -7
That's why we leave the engineering to you Doc!!
|
|
|
Post by mazzer on Jan 4, 2019 9:37:07 GMT -7
Thanks all for the - reassuring - info! And yes, Doc, I did experience a slight dizzyness upon reading your technical explanation ;-). But I focus on your opening statement, that the 12AU7-type tube won’t cause any issues. Great news, thanks again and keep up the good work! 👍
|
|
|
Post by zpilot on Jan 4, 2019 18:00:13 GMT -7
I think I would go with a 12AY7 instead. That was a common first gain stage tube in a lot of tweed Fenders. Rock players would replace them with a 12AX7 to get more gain. The gain of a 12AY7 is a little more than a 12AU7 but considerably less than a 12AX7. Whichever you use don't expect the amp to breakup at a much lower volume. It will just be quieter at the same control settings and the tone may be a little warmer. A guy I tech for plays with a jazzy tone and I put a 12AY7 in his first stage. He likes it better than a 12AX7. It breaks up later. Some folks would call that more headroom.
|
|
|
Post by mazzer on Jan 26, 2019 10:18:41 GMT -7
zpilot: I tried a 12ay7 first. It was still to loud. Good tone, though. Thanks for the suggestion.
|
|