toddg
7 posts
Jan 03, 2011
6:22 PM
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Hi ,
I just bought a 1963 Concert Amp .
I was wondering if there are any pre amp tube swaps anyone uses ?
http://www.flickr.com/photos/57898141@N08/5322429972/
http://www.flickr.com/photos/57898141@N08/5322430084/in/photostream/
Last Edited by on Jan 03, 2011 6:23 PM
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MP
1223 posts
Jan 03, 2011
9:43 PM
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-why do you want to swap the pre-amp tube? to increase volume before feedback?
if that is the case, lots of people change out the existing 12AX7 with 12Y or 12AU. you don't need to re-bias after doing this. everybody has differing opinions as to the best tubes to use(i won't go there). also, there is the school that would NEVER tube down.---------
MP
hibachi cook for the yakuza
doctor of semiotics
superhero emeritus
Last Edited by on Jan 03, 2011 9:44 PM
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toddg
8 posts
Jan 03, 2011
10:09 PM
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Yes it's to increase volume before feedback
Ps I tryed to post the pictures but it just put the links .This amp is the cleanest I have ever seen !
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LittleJoeSamson
460 posts
Jan 03, 2011
10:33 PM
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Why not do some swapping ( if you have a source for tubes ) ?
Since it's a two channel, I would try subbing a 12AY7 or a 6211 in V1.
For V2, a 5751 would be good.
Keep the 12AX7/7025's for any effects.
Phase inverter / V6 , might be a 12AT7 in there now. See if you can find a 6829 ( taller bottle, milspec tube ), or a 12DW7/7247.
Sucker should be loud and tasty.
What did you pick it up for ?
Have the electrolytics checked out, too. ( Tho, if it sounds fine, they're prolly OK ).
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5F6H
459 posts
Jan 04, 2011
1:36 AM
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I dont know anyone (but I'm sure there are people who do) that runs anything other than 12AX7 tubes in a Concert. A 5751 or 12DW7 can work in V6 (next to the power tubes, counted from R to L) but I would keep 12AX7 in V1 (Normal channel preamp).
The tolex Fenders are not quite as flexible as the tweeds when it comes to tube swapping, a Brown Concert may hit max volume before feedback at anywhere from 2.5 to 4 on the vol control, yes they can be a bit touchy until you get used to them but subbing preamp tubes is not usually the way to go. If you want to calm down the sweep on the volume pot you will need to change the pot to a 250KA fed by a 470K resistor, instead of the plain wire from the treble control, or tack a resistor of the desired value from middle tab of the stock 1MA volume pot to ground (try 27K to 47K values?).
Also try a 56K to 82K 3W resistor to drop the preamp voltage, last resistor on the Right when looking at the cap pan (resistors at the bottom, cap "-" at the top).
To reduce feedback, run the power tubes colder, at say 7-15mA per tube, sometimes Sovtek 5881 WXT just drop in at these kinds of currents in late brown amps. Otherwise you will need to rebias.
Even with the stock preamp tube config, a good brown Concert is about as loud as 2x6L6 harp amps go.
I'm not saying you can't run low mu tubes in it, just that it is unlikely to result in more volume, you may still like the tone. A 12AU7 in V6 draws alot of current accross the PI plate resistors...don't know if I would be comfortable with this for extended periods.
Last Edited by on Jan 04, 2011 1:37 AM
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toddg
9 posts
Jan 04, 2011
2:05 AM
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I did use the amp at a Jam last night and I ran the vol at 2 1/2 treble at 5 1/2 and bass on 7
And it sounded plenty loud ! with a great tone !!
I also play Slide Guitar so I will probably just keep it with the stock tubes so I can use the amp for both harp and guitar .
Did you see the pics of the chassis from the links ? It's like a brand new amp ! I paid $ 1,750 . plus shipping .
Thanks for all the Great feedback !!
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MP
1225 posts
Jan 04, 2011
10:32 AM
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-great amp! i'd leave it stock myself.---------
MP
hibachi cook for the yakuza
doctor of semiotics
superhero emeritus
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