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05-12-2011, 11:54 AM
| | Banned | | Join Date: Dec 2009 Location: Cleveland, Ohio | | | Mesa 400(not plus) people!
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So im gonna have the Bias pot mod done to my amp by an amp tech here in Cleveland. He also suggested putting preamp tubes to drive the Slider EQs as well, to get a warmer sound when using the EQ.
Any thoughts? |
05-12-2011, 11:58 AM
|  | Sponsored by Jagermeister | | Join Date: Nov 2002 Location: Seattle / Tacoma | | Quote: |
Originally Posted by TaylorO' He also suggested putting preamp tubes to drive the Slider EQs as well, to get a warmer sound when using the EQ. | Sounds intersting. Are there any locally known heads he's done that to that can be heard? |
05-12-2011, 12:16 PM
| | Banned | | Join Date: Dec 2009 Location: Cleveland, Ohio | | Quote:
Originally Posted by Caca de Kick  Sounds intersting. Are there any locally known heads he's done that to that can be heard? | Not particularly. His name is Jeff Scarborough. He builds Scarborough Amps, which around here have a good reputation. He said looking at the schematics for my amp he noticed that the EQ was all transisitors and stuff and not affected by the tubes at alll and that putting in two ax7s or 1 ax7 and 1 au7 would probably "warm" it up...generally i dont use the EQ(sliders) because i dont like the sound of it, but this is an interesting idea... |
05-12-2011, 12:16 PM
|  | The "G" is for Gustav | | Join Date: Jun 2006 Location: Maryland | | | Sounds like he doesn't know what he is talking about. I wouldn't do it. You will ruin the resale and won't get any more warmth from it. The signal path is all tube already so you will just be messing up the gain structure. The EQ is a simple LC network - it doesn't have any ICs in it. |
05-12-2011, 12:21 PM
| | Banned | | Join Date: Dec 2009 Location: Cleveland, Ohio | | Quote:
Originally Posted by JGR Sounds like he doesn't know what he is talking about. I wouldn't do it. You will ruin the resale and won't get any more warmth from it. The signal path is all tube already so you will just be messing up the gain structure. The EQ is a simple LC network - it doesn't have any ICs in it. |
im on the fence about it for now. But def gonna do the bias mod. As for "ruining the resale" thats never something i consider when i buy something. i dont buy things with the possibility of reselling them later, but to each their own.
Yeah still just gathering opinions on this one... |
05-12-2011, 12:35 PM
| | The "G" is for Gustav | | Join Date: Jun 2006 Location: Maryland | | Quote: |
Originally Posted by TaylorO'
im on the fence about it for now. But def gonna do the bias mod. As for "ruining the resale" thats never something i consider when i buy something. i dont buy things with the possibility of reselling them later, but to each their own.
Yeah still just gathering opinions on this one...
| Fair enough on the resale aspect, but I hate seeing nice amps butchered. Adding more tubes does not equate to more warmth. You will get more noise though, not to mention more current draw on the PT. |
05-12-2011, 12:38 PM
| | Banned | | Join Date: Dec 2009 Location: Cleveland, Ohio | | Quote:
Originally Posted by JGR Fair enough on the resale aspect, but I hate seeing nice amps butchered. Adding more tubes does not equate to more warmth. You will get more noise though, not to mention more current draw on the PT. |
Jeff is a reputable guy... when we spoke on the phone he was in and out of his office and didnt have a lot of time with the schematic, so by the time i get the amp to him he may have changed his mind on that. We shall see. The EQ section has always kinda sounded a little cold to me... but maybe im just deaf or something haha.. |
05-12-2011, 12:50 PM
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Editor-in-Chief, Bass Gear Magazine | | Join Date: Apr 2003 Location: North central Ohio | | | I would not mess with the EQ. That head sounds plenty warm as it is. I'm also a bit on the fence regarding the bias trim mod. I did have my Bass 400 modded (first by a company in Cleveland - not your guy - who screwed it all up, and then later fixed/refurbed by British Audio Service, who did a fantastic job), and while I am happy with the results, I have to say, Randall did do some pretty cool things, and those heads sound pretty good with the fixed bias, too. |
05-12-2011, 01:28 PM
| | Sponsored by Jagermeister | | Join Date: Nov 2002 Location: Seattle / Tacoma | | | I never thought it sounded cold either. Maybe just try different preamp tubes?
The way I see it, the stock eq'ing giving you two options is plenty great sounding. |
05-12-2011, 01:38 PM
| | Banned | | Join Date: Dec 2009 Location: Cleveland, Ohio | | | my main want in all this is to get away from 6l6's without blowing anything up... Like i said the EQ thing i can wait on. But im afraid to drop in 6550s or kt88s and just go with it... |
05-12-2011, 01:41 PM
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Editor-in-Chief, Bass Gear Magazine | | Join Date: Apr 2003 Location: North central Ohio | | Quote:
Originally Posted by TaylorO' my main want in all this is to get away from 6l6's without blowing anything up... Like i said the EQ thing i can wait on. But im afraid to drop in 6550s or kt88s and just go with it... | The Bass 400 can handle KT88s without blowing up. |
05-12-2011, 01:44 PM
| | Registered User | | Join Date: Sep 2009 Location: Minneapolis | | | The graphic equalizer is transistor based, everything else in the amplifier is a tube driven signal. I sure can't hear a degradation in sound quality by switching on the EQ, but if you want to avoid the transistor portion of the circuitry simply stick to the rotary tone controls.
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05-12-2011, 05:09 PM
| | Registered User | | Join Date: Aug 2004 Location: under your bed | | Quote:
Originally Posted by tombowlus The Bass 400 can handle KT88s without blowing up. | Mine handled 'em just fine. The fixed bias point may not have been optimal for the JJs I threw in there, but it sounded good and had no problems.
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Meh.
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05-13-2011, 06:02 AM
| | Registered User | | Join Date: Jan 2003 Location: Philippines | | | From my experience in modding and building tube amps, adding this to your amp may or may not do what you want. There are plenty of examples of adding tube stages to a circuit with either minimal or even negative results as far as improving "tube" tone.
If I were going to do this mod on my own amp I would try to breadboard the circuit first to see if I liked the result before committing to the actual mechanical installation.
For what it''s worth I once had a Fender Studio Bass Combo (200 watt all tube) that I converted to head only. This amp has a tube driven LCR type 5 band eq section. Very limited range. I wound up using a solid state eq to get the tone I was looking for. |
05-13-2011, 07:47 AM
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Originally Posted by TaylorO' my main want in all this is to get away from 6l6's without blowing anything up... Like i said the EQ thing i can wait on. But im afraid to drop in 6550s or kt88s and just go with it... | The fixed bias in the 400 (non plus) was designed around the 6550. That is the tube it is optimized for and there is definitely no need to install a bias adjustment to use 6550s. | | Thread Tools | Search this Thread | | | | 
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