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Post subject: Re: Supersonic effects loop query?
Posted: Fri Jun 22, 2012 12:13 pm
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IM4Tone wrote:
Reason is the BDRI's drive channel did not give me as much distortion as I wanted without making my ears bleed! I very much like it in the BDRI, and yes, it's $10 worth of parts costing $19....that sure isn't a big deal to me.


Really? Either you do not understand the design of the BDRI preamp and how the clean and drive controls function, or your amp has a problem. I can turn the master volume down to almost nothing, crank the drive control, and drive the crap out of the preamp on mine. And that is with a low-gain 12AY7 in V1. As has been stated numerous times, master volume amps only allow you to get preamp distortion at low sound levels. The amp still has to be cranked up LOUD in order to overdrive the power tubes. A volume box will not help to make that happen.

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Post subject: Re: Supersonic effects loop query?
Posted: Fri Jun 22, 2012 12:21 pm
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shimmilou wrote:
The OP said he had a SS Twin, not a 22. :idea:

You kinda jumped right into the middle of a response for the OP. :lol:

??? I missed your point????

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Post subject: Re: Supersonic effects loop query?
Posted: Fri Jun 22, 2012 12:28 pm
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bluesky636 wrote:
IM4Tone wrote:
Reason is the BDRI's drive channel did not give me as much distortion as I wanted without making my ears bleed! I very much like it in the BDRI, and yes, it's $10 worth of parts costing $19....that sure isn't a big deal to me.


Really? Either you do not understand the design of the BDRI preamp and how the clean and drive controls function, or your amp has a problem. I can turn the master volume down to almost nothing, crank the drive control, and drive the crap out of the preamp on mine. And that is with a low-gain 12AY7 in V1. As has been stated numerous times, master volume amps only allow you to get preamp distortion at low sound levels. The amp still has to be cranked up LOUD in order to overdrive the power tubes. A volume box will not help to make that happen.

Mine is the only BDRI i've every played, but I can assure you that on the drive channel, I can max the "drive" pot and the amp stays much cleaner than I want it unless I turn the master up to very excessive volumes. Don't know if that is a defect or not? And yes, I'm totally aware that I'm getting pre-amp not power amp distortion using the volume box.

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Post subject: Re: Supersonic effects loop query?
Posted: Fri Jun 22, 2012 12:32 pm
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I tried the vol knob yesterday, A,B ing my supersonic and BDRi at work once everyone gone home so I could really get both fairly cranked up.
I found that on the BDRi, with it last in the chain, the was a slight change in overall tone. But nothing drastic. This is what I expected as I use it on a regular basis in my rig.
Moved onto the SS. Wow. But not in a good way. Sounded awful tbh. Sounded dense and heavy, and could feel the amp being stifled and restricted. Took it out the loop. All was well. :D


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Post subject: Re: Supersonic effects loop query?
Posted: Fri Jun 22, 2012 1:15 pm
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IM4Tone wrote:
bluesky636 wrote:
IM4Tone wrote:
Reason is the BDRI's drive channel did not give me as much distortion as I wanted without making my ears bleed! I very much like it in the BDRI, and yes, it's $10 worth of parts costing $19....that sure isn't a big deal to me.


Really? Either you do not understand the design of the BDRI preamp and how the clean and drive controls function, or your amp has a problem. I can turn the master volume down to almost nothing, crank the drive control, and drive the crap out of the preamp on mine. And that is with a low-gain 12AY7 in V1. As has been stated numerous times, master volume amps only allow you to get preamp distortion at low sound levels. The amp still has to be cranked up LOUD in order to overdrive the power tubes. A volume box will not help to make that happen.

Mine is the only BDRI i've every played, but I can assure you that on the drive channel, I can max the "drive" pot and the amp stays much cleaner than I want it unless I turn the master up to very excessive volumes. Don't know if that is a defect or not? And yes, I'm totally aware that I'm getting pre-amp not power amp distortion using the volume box.


Totally ignoring the master volume control or the volume box for the moment, the design of the BDRI preamp is pretty simple.

http://support.fender.com/schematics/gu ... _Rev-A.pdf

In the clean mode, the volume control resides between V1A and V1B. The drive control between V1B and V2A is switched out and replaced by a 15K Ohm resistor. This 15K Ohm resistor, along with the 220K Ohm resistor following the tone stack, forms a voltage divider to drive V2A. When the clean volume control is turned all the way up, V1 operates at maximum gain, driving the tone stack and eventually V2A. The output of the tone stack is dropped across R8 and R102 (most of it actross R8) to drive V2A. The signal from V2A then goes to the phase inverter and the power output tubes. When set to maximum volume, you get a combination of preamp and power amp distortion and the amp is quite loud.

Now, switch to drive mode. In drive mode, the clean volume is switched out and replaced by a 240K Ohm resistor. This is effectively the same as having the clean volume maxed out. V1 provides maximum gain and signal level to V2A. Also, the drive control is switched in. When maxed out, the drive control acts as a 250K Ohm resistor, again forming a voltage divider with the 220K Ohm R8. Because the maxed out drive control is larger than the 15K Ohm R102, a larger portion of the voltage output from the tone stack is applied to the input of V2A. V1 is now driving V2A much harder than it was even with the clean volume maxed out. The net result is greater preamp distortion in drive mode than in clean mode. The master volume control is then used to set the overall volume level of the amp, allowing max preamp distortion at low volume levels.

When inserting the volume box into the effects loop and using the clean channel, even when the clean volume is maxed out, preamp distortion is going to be less than preamp distortion available in the drive mode. But because the preamp is driven differently when in clean or drive mode, the tonal character of the preamp distortion may be different between the two modes. You may prefer the sound of one over the other. I would not be surprised if that were indeed the case.

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