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12-25-2012, 12:03 PM
| | | | Attenuator solutions?
I have a tube amp with only one output jack (rated for 8 Ohms). I usually use an 8 Ohm cabinet when performing, but occasionally would like to use a second 8 Ohm cabinet or use a cabinet with a different (lower) impedance.
Are there any devices available the can be plugged in-between the amp/cabinets to solve this problem? Maybe a power attenuator?
I'm thinking it may be best to just replace the output transformer with one that has an 8 Ohm and 4 Ohm tap and reconfigure the line-out jack to a second cabinet jack. |
12-25-2012, 12:08 PM
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HPF Technology: Protecting the Pocket since 2007 | | Join Date: Mar 2004 Location: Madison WI | | AFAIK Peavey used to sell a speaker level matching transformer. Alternatively, upgrading the amp would probably be the way to go. |
12-25-2012, 12:10 PM
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Endorsing: Ampeg | | Join Date: Apr 2005 Location: Apopka, FL | | | What amp is this?
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12-25-2012, 01:01 PM
| | Registered User | | Join Date: Oct 2006 Location: Rhode Island, USA | | | Yes, an attenuator can do this. I have of the old Tom Scholz Power Soaks and it can present the amp with either 4, 8 or 16 ohm loads, and has two speaker out jacks. Using either or both jacks doesn't affect the load that the amp sees. |
12-25-2012, 03:50 PM
| | | | Amp I have is Fender Studio Bass (tube head, chopped from a combo; six 6L6 output tubes- 200 WRMS @ 8 Ohms). Mercury Magnetics makes one with a 4/8/16 Ohm tap.
I would like to consider an external device, since I could use it with other amps as well... but my other tube amps have multi-tap outlets or selection switches.
Last edited by RobbieNuke : 12-25-2012 at 04:34 PM.
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12-25-2012, 04:01 PM
|  | mi la ré sol | | Join Date: Mar 2002 Location: Reims, Champagne, France | | According to these schematics, the output transformer to your amp should be a 012413. These are supposed to be switchable. There should be several output on the transformer with different values, all your amp may be missing is a switch to go from 8 to 4. 
An attenuator is a bad solution in your case. You're simply going to lose half of your power. |
12-25-2012, 04:45 PM
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HPF Technology: Protecting the Pocket since 2007 | | Join Date: Mar 2004 Location: Madison WI | | The schematic shows two output terminals, so it's not switchable. The pics in the following eBay auction shows that there is not an extra wire. http://www.ebay.com/itm/Fender-Studi...p2047675.l2557
My advice would be to find a higher sensitivity cab. |
12-25-2012, 05:11 PM
| | | | Studio Bass schematic
The are some schematics going around, like the one you posted, that have the "180 Watt Studio Bass" imposed upon the nomenclature and the Super Twin output tranny, p/n 012413 (which is actually 4 Ohms, not 8 Ohms... it was connected to a pair of 8 Ohm speakers in parallel). The correct schematic is titled "Schematic- 200 Watt Bass amplifier" and has an output tranny, p/n 012991, which is 8 Ohms.
As far as I know they are two very similar transformers, but neither is multi-tapped or has a selector switch (my amp does not). Of course, these are both very similar amplifiers with the Super Twin having a Distortion/Boost circuit and the Super Twin Reverb having reverb as well. |
12-25-2012, 05:25 PM
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Bedford guitars | | Join Date: Apr 2009 Location: sheffield, uk | | | get a different OT or cab
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12-25-2012, 06:08 PM
| | | | different cabs
No need for a different cabinet. The main cabinet I use with this amp is 8 Ohms and matches. It's mostly if I want to use multiple 8 Ohm cabinets or cabinets of a lower impedance.
OT replacement is a good consideration... it's just that if there is an external device that would provide the same 'fix' (i.e. allow amp/load impedance mismatch w/o damage) that would be better since I could use it with my other amps as well. |
12-26-2012, 09:20 AM
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12-26-2012, 09:53 AM
| | | Quote:
Originally Posted by JHAz  | He needs a 200W something. This probably contains a Weber WZC-100 impedance converter transformer which is about half the price.
I'd suggest a SS slave amp, either with a speaker DI or using the line out. The speaker DI would give the added benefit (if it is in fact one) of a speaker load on the amp output; if both cabs were the same make/model then he should get the same output from both. | | Thread Tools | Search this Thread | | | | 
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