low down 12ax7?

Safe haven for everything low-frequency. Bass players unite in this forum.

low down 12ax7?

Postby gypsy moth on Sun May 14, 2006 2:53 am

any suggestions for a 12ax7 that brings out the bass - without getting muddy?
I'm trying to make my 100 watt lead amp behave a little more like my 200 watt bass head :roll: , without surgery.

thanks
gypsy moth
King
 
Posts: 5294
Joined: Mon Oct 06, 2003 7:01 am
Location: in the midst of fanatics & zealots

Postby ozsubrosa on Sun May 14, 2006 3:40 am

I tried out various types with a 4xEL34 Laney PA. For bass, I actually preferred the GE 12AX7WA over the Mullard. I do like the Mull, and guitar definitely sounds better, but the GE is less middish. Cheaper, too. The RCA 7025 is nice, but the GE is less trebly.

Of the over-the-counter moderns, I like the Lizhiou Chinese AX7 (try PM or Golden Dragon) or the Ei. Avoid the Sino Chinese which sound buzzy.

Another alternative, if you don't mind losing a little gain, is the Mullard or Brimar CV4024. This is actually a 12AT7, but it works well. Smooth, buttery, doesn't lose its composure in V1.

Just my own ops/exps,
Oz
"Have bass, will valve"
ozsubrosa
Baron
 
Posts: 2672
Joined: Sat Jul 17, 2004 7:01 am
Location: NW England

Postby gypsy moth on Sun May 14, 2006 3:27 pm

less mids the the mull and less treble than an RCA says more bass overall :D thanks Oz

at least with power tubes, I find my mull/ relabels to be overdone in guitar lows, they just distort too much and too early for guitar - let alone bass. although maybe two of them with two C's would work for me.
I'm pretty high gain on either, but don't like it to get muddy.
gypsy moth
King
 
Posts: 5294
Joined: Mon Oct 06, 2003 7:01 am
Location: in the midst of fanatics & zealots

Postby soundandthecity on Mon May 15, 2006 5:28 am

Try out a JJ ECC803. It is way inexpensive compared to Mull`s/Brimars and brings a lot of warmth in the sound with getting muddy.
Hope it helps,
SATC
soundandthecity
Squire
 
Posts: 536
Joined: Wed Feb 25, 2004 8:01 am
Location: Northern Germany

Postby Der Bassmann on Mon May 15, 2006 9:11 am

in my SC120, i have a 5751 (12AX7A) in the input stage. a very fine tube, quite low-gain, clean and warm sound.
Der Bassmann
Peasant
 
Posts: 32
Joined: Wed Apr 05, 2006 9:34 am
Location: Germany

Postby gypsy moth on Mon May 15, 2006 4:38 pm

thanks guys - if I remember right the 7025 & 5751 are slightly less gain than an ax7, but more than an at, with the 7025 being another designation for the ax7.
I'm thinking (uh oh) that this stuff was mostly designed post war for record players, with the brits listening to soothing stuff like white cliffs of dover at apartment volumes, the US market going towards eight foot consoles in suburban homes belting out brassy Sousa and Glen Miller, so brit speaker design and tubes muddy up early because they wanted warmth at low volume, the US stuff is bright and clear in comparison - and I want dynamic string and choir sounds. The Germans engineers may have been listening to Wagner et al real loud, and may have designed around that parameter, and the consumer will like it because it is designed better, even if they don't have the equipment to benefit from it?

I've got some of what is mentioned, or similiar to it between my three amps, and it's not doing what I want in this one, so I'll try and test this theory, as my only german tube is an rft at7 in the 200's PI, which made a big difference in output on my 200, although no big tone difference in that position.
gypsy moth
King
 
Posts: 5294
Joined: Mon Oct 06, 2003 7:01 am
Location: in the midst of fanatics & zealots

Postby runmikeyrun on Tue May 16, 2006 11:49 pm

i have a budda tube distortion pedal w/ two pre tubes in it. I use a telefunken 12at7 and mullard 12au7, in that order. The pedal's design still allows as much gain at max gain settings as the 12ax7s even with those tubes in place. Not sure about your amp but you may come close enough.

If the tubes aren't enough, you can probably just increase your coupling cap values a little, that will help a lot with minimal surgery. I'm not sure about amps but when i mod guitar distortion circuits for bass i change coupling cap values from 0.1/.22 uF to 1.0, 2.2, or even 10uF. Usually multiplying by a factor of 10 will give you a good amount of low end. Remember when you parallel caps the values add together for the final capacitance. So you wouldn't even have to remove the existing caps, just piggyback ones on top to experiment. When you find the right value, substitute one cap in place of the two.

Good luck!
Chuck Norris doesn't tea bag, he potato sacks!
runmikeyrun
Knight
 
Posts: 1584
Joined: Wed Jul 24, 2002 7:01 am
Location: Akron, OH

Postby gypsy moth on Wed May 17, 2006 12:50 am

thanks mikey, I don't quite have confidence in my soldering or schematic skills to do things typically described as simple mods.
plugging in tubes I can handle - provided no bias adjustment is required :oops: .
gypsy moth
King
 
Posts: 5294
Joined: Mon Oct 06, 2003 7:01 am
Location: in the midst of fanatics & zealots

Postby ozsubrosa on Wed May 17, 2006 2:11 am

:lol: , Moth - I'm the same. Holding off the solder -trying to get by with tube-swaps. The 7025 is a low-noise, same-gain 12AX7 (a 12AX7A or 12AX7WA can have the same purpose in life). The 5751 is low noise (and just about the most undistortable preamp tube I've tried) but it does have about 70% of the gain of a 12AX7/ECC83. A 12AT7/ECC81 has about the same amount of gain.

I've tried good, blackplate 5751 in the input gain stage but didn't really like it. OK for bass, 2-D flat for guitar and beaten to a pulp by the Brimar CV4024 (12AT7) using guitar or bass. A lot depends on amp, guitar, ear'oles, though.

Oz
"Have bass, will valve"
ozsubrosa
Baron
 
Posts: 2672
Joined: Sat Jul 17, 2004 7:01 am
Location: NW England


Return to Bass Talk

Who is online

Users browsing this forum: No registered users and 1 guest