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Laurie
Double Platinum Member
Canada
4854 Posts |
 Posted - 02/08/2009 : 06:19:44
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| Does someone have a link to instructions about how to halve the power of a Fender amp by dropping 2 of the 4 output tubes? Thanks in advance!! |
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Dirk
Platinum Member
Netherlands
1309 Posts |
Posted - 02/08/2009 : 11:18:25
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| Can't you just pull out a pair of power tubes, either the inner or the outer pair, just like a Marshall amp? |
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Witloofboer
Gold Member
Belgium
513 Posts |
Posted - 02/08/2009 : 12:20:03
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quote:
Originally posted by Dirk
Can't you just pull out a pair of power tubes, either the inner or the outer pair, just like a Marshall amp?
That's some risky business!
You can try to install triode/pentode switch on the output valves. |
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zerksies
Double Platinum Member
USA
3406 Posts |
Posted - 02/08/2009 : 13:22:01
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| you can do it but you have to pull out tubes 1&3 or 2&4 you can't pull it out any other way or the amp won't work |
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FRANZONI
Double Platinum Member
Ireland
3543 Posts |
Posted - 02/08/2009 : 15:18:13
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I always thought it was 1 and 4 or 2 and 3(the outside two and the inside two are paired together) or do fenders work differently to other amps..? also pulling two of the output tubes shouldn't cause any long term harm as far as i have read up on the subject..what some peope recommend is,if you pull two tubes change the impedence selector to a different setting to replace some of the freq loss from pulling half the output tubes...it doesn't really lower the volume a lot,it just makes the amp distort a bit quicker....
I emailed a guy in your neck of the woods Laurie, a few years back before i discovered Bossarea,about a problem i had with my marshall head and he very kindly sent me back two emails with suggestions..his name is Kevin O'Connor and his company is called London Power... www.londonpower.com he also has a very good FAQ page IMHO........
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Edited by - FRANZONI on 02/08/2009 15:20:06 |
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verivorax
Platinum Member
Canada
1185 Posts |
Posted - 02/08/2009 : 19:35:00
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I'm with Franz on this one. I've always been told 1/4 and 2/3 are the matched pairs and either could be pulled - but not all amps like this.
I believe it's possible with Fenders and Peaveys, but NOT with newer Marshalls. Dual Recitifiers can do it, but the TripleRec can't. This is old info buried in my brain.. and it could be flawed!!
The Traynor tube amps currently in production are self-biasing, and I've seen an 80w dropped to a single power tube (from 4) and operate very well!
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jaymzHal
Silver Member
United Kingdom
297 Posts |
Posted - 02/09/2009 : 19:09:10
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| Does this only work for fender amps with 4 output tubes? My Pro Junior has 2 input and 2 output, does that mean I can't do anything? |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 02/09/2009 : 19:17:06
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OK... thanks for all the info! Did more checking, and it looks like it is outer or inner pair (1-4 or 2-3). Then double the output load (use a 16 Ohm cab on the 8 Ohm output).
Does it really not make that much difference to the total volume level? I have a Bassman 100 on loan that needs WAY too much volume to start really sounding good. Although when it is driven by my MT-2 Stormchaser with the amp input at 10 and the master at 8 through a Marshall 4x12 ... while it is overpoweringly loud, it does have more balls than a driving range...
I've been reading the threads about power brakes with some interest, and am thinking about building my own with nichrome wire (my old design with 10W power resistors just isn't big enough for this beast).
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FRANZONI
Double Platinum Member
Ireland
3543 Posts |
Posted - 02/09/2009 : 19:25:04
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quote:
Originally posted by jaymzHal
Does this only work for fender amps with 4 output tubes? My Pro Junior has 2 input and 2 output, does that mean I can't do anything?
Yes only amps with output stages with four valves..you can't remove the preamp valves(the small ones) as one boosts the input stage of the preamp and the other is probably a phase splitter,your pro junior has only two output valves and you would unbalance the output stage if you removed one...this was an old trick that guitarists used to do with Marshalls etc..i.e amps with a lot of watts to try to tame tham a bit and get them to sound a bit more distorted..it doesn't really lower the output that much... maybe with an amp like a AC30 you might notice a drop in volume but i tried it with my musicman and didn't notice much to be honest.... |
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zerksies
Double Platinum Member
USA
3406 Posts |
Posted - 02/09/2009 : 23:11:54
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| Cause when you put in new output tubes you have to put the matched pairs in spots 1&3 and in 2&4. |
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pawnshop_trash
Gold Member
USA
603 Posts |
Posted - 02/09/2009 : 23:50:51
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quote:
Originally posted by Laurie
I've been reading the threads about power brakes with some interest, and am thinking about building my own with nichrome wire (my old design with 10W power resistors just isn't big enough for this beast).
I know a guy that uses his Marshall TSL head with a Scholz (sp?) attenuator, to the great relief of his family... but you should also be aware that the use of a power brake will void your warranty with some amp manufacturers. so if it's new and under warranty, be careful.... |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 02/10/2009 : 00:22:26
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quote:
Originally posted by pawnshop_trash
I know a guy that uses his Marshall TSL head with a Scholz (sp?) attenuator, to the great relief of his family... but you should also be aware that the use of a power brake will void your warranty with some amp manufacturers. so if it's new and under warranty, be careful....
Thanks for the additional manufacturer info!
Nah... no worries with the warranty - it expired on this puppy 35 years ago 
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zerksies
Double Platinum Member
USA
3406 Posts |
Posted - 02/10/2009 : 02:52:22
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quote:
Originally posted by Laurie
quote:
Originally posted by pawnshop_trash
I know a guy that uses his Marshall TSL head with a Scholz (sp?) attenuator, to the great relief of his family... but you should also be aware that the use of a power brake will void your warranty with some amp manufacturers. so if it's new and under warranty, be careful....
Thanks for the additional manufacturer info!
Nah... no worries with the warranty - it expired on this puppy 35 years ago
Give it till march premire guitar is doing a story about them |
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jaymzHal
Silver Member
United Kingdom
297 Posts |
Posted - 02/11/2009 : 01:09:04
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quote:
Originally posted by FRANZONI
quote:
Originally posted by jaymzHal
Does this only work for fender amps with 4 output tubes? My Pro Junior has 2 input and 2 output, does that mean I can't do anything?
Yes only amps with output stages with four valves..you can't remove the preamp valves(the small ones) as one boosts the input stage of the preamp and the other is probably a phase splitter,your pro junior has only two output valves and you would unbalance the output stage if you removed one...this was an old trick that guitarists used to do with Marshalls etc..i.e amps with a lot of watts to try to tame tham a bit and get them to sound a bit more distorted..it doesn't really lower the output that much... maybe with an amp like a AC30 you might notice a drop in volume but i tried it with my musicman and didn't notice much to be honest....
Ah thanks Franzoni, I see exactly what you mean. I'm surprised it doesn't effect the tone more, i'm assuming you are either bypassing the valve socket entirely or it's acting as another earth? I'm surprised they don't cut out entirely! |
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4 tube to 2 tube mod on Fender amps
