Author Topic: Brightness,tubes and amps... (Read 3192 times)

viking · « **on:** October 12, 2007, 03:29:49 AM »

Hi! I'm the lucky owner of a M&B Nomad55;i find it a bit too bright and i'm thinking of changing the 12AX7 (GT12AX7M) for a Jan-Philips 5751 in the V1 preamp socket to smooth out and warm the gain.What do you think?I've never done that before.Changing Powertubes is easy but the preamp tubes seems more difficult to take out...Difficult to reach but ,also,there is a cover on it !Is it easy to take out or is there a "special technique"? There is also some noise (hum) with the reverb and only for some time,so i think i would swap another 12AX7 to check that too...Someone suggested to try the Tungsol 6L6 GC-STR for a warmer/less bright sound instead of my TAD 6L6 WGC/MB 6L6.Any advice about those matters would be greatly appreciated :)

hamfist · « **Reply #1 on:** October 12, 2007, 07:42:11 AM »

Hi Viking,
I'm not quite sure what you mean by "smooth out and warm up" the gain. If I was using those words I would be meaning I wanted the tone to be less bright and harsh, definately a bit darker. I will assume you are meaning that.
A 5751 will not necessarily change the tone in that way (although it might). Changing a 12ax7 for a 5751 in the pre-amp will reduce gain though - however, the basic nature of the tone should not change.
JJ Ecc83's are one of the "darkest" pre-amp tubes out there, and can be useful in taming harsh/bright amps. Pre-amp tubes should be pretty simple to change. Just make sure the amp is OFF, remove the tube cover (if there is one) and gently ease out the old tube. With the nw tube, first make sure the tube pins are aligned with the socket, then push down with slight circular movements until the tube is sitting nice and tight down to the socket. Replace the cover - done !

However, instead of changing out power or pre-amp tubes, I suspect you will have more effect trying different speaker(s). In my experience, speakers have a more profound effect on the tone than tubes. Eminence Cannabis Rex's are very good at taking out an over-bright top end.

Alan

Twinfan · « **Reply #2 on:** October 12, 2007, 08:36:56 AM »

I disagree with Alan slightly here as I don't find JJ ECC83s dark sounding - they're my favourite preamp tubes (nicer than the old Brimars I have lying around). I find the JJs full sounding, crisp and clear but not shrill.

I'd agree with Alan about speakers though. I'd invest in a new set of pre-amp valves (around £9 each) and see how the amp sounds. The metal covers over them just twist and pull off.

If your amp is still shrill with new valves, then I'd look at your speaker(s). This is what I'd recommend:

1x12 = Celestion Vintage 30
2x12 = Celestion Vintage 30 and G12H (Heritage series if you can afford it)
4x10 = Celestion Vintage 10s

Elliot · « **Reply #3 on:** October 12, 2007, 08:39:42 AM »

I would agree about the Eminence C Rex - the Swamp Thang and to a lesser degree the Texas Heat do the same thing.

I use one of Watford's cryo GE 5751 in V1 of the pre-amp tubes of my Blues Junior (a notoriously bright amp) - its doesn't smooth things out, although the sound is somehow 'bigger' than with a 12AX7.

Using a 5751 improves the clean headroom of the amp as V1 is not pushed into distortion so quickly. That doesn't mean that the amp remains clean at all levels, indeed at top tilt the BJ is a beast. I find using a 5751 helps if you use pedals as the gain from the pedal's pre-amp can push a bright amp into OD too soon - giving a nasty bright sound. The 5751 calms that effect giving you break up slightly later and thus allowing a more saturated sound.

In other words - its worth experimenting with....

viking · « **Reply #4 on:** October 15, 2007, 02:00:04 AM »

Thanks to you all ! :D I was away and couldn't find a PC before...I will experiment!But how do you experiment with speakers?We don't have many options left in Brussels...

By the way,how would you describe the Black Shadows (Celestion 12") by M&B,if anybody knows them..?

Elliot · « **Reply #5 on:** October 15, 2007, 09:45:14 AM »

I just looked up the Nomad - I think a 5751 would go very well in this amp to sweeten things up - but it would emphasise the amp's more 'American' side.

As to the Black Shadows - they are similar to the original G12-80 from which the current day Classic Lead 80 derives but (I think) with more bass and top end.

viking · « **Reply #6 on:** October 15, 2007, 05:11:03 PM »

Quote

I think a 5751 would go very well in this amp to sweeten things up

8) Sounds nice! (English language is really suggestive !).And good luck with your speaker's experiment (G12H100 etc.),Elliot! Cheers!