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Post subject: Tech. Question about the BDRI
Posted: Mon Apr 11, 2011 12:34 pm
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For some time, I've been considering getting an attenuator, but never could be sure I'd be satisfied with the significant cost and the bulk of another piece of equiptment to carry around. I've also toyed with the idea of getting a vol. box to put in the effects loop for some time and finally spent the $20 to get one. (Waste more than $20 every week on who knows what...so why not gamble?) I realize it's just an audio taper pot, two jacks, and a box, but I was hopeful that it would allow me to get around the very sensative pots on the amp that jump from silent to too loud with very small movement. This box has done that for me, and so is worth it to me.

My questions are:
1) Is it my imagination, or has this device enabled me to get slightly more "dirt" since the clean vol. and channel two's master are now set higher on the amp with the vol. box decreasing the signal between the preamp and power tubes?
2) Perhaps the same question asked in a different way: 1st the clean chnl vol. knob...is it affecting power to the preamp tubes, the power tubes, or both. 2nd regarding the drive chnl....with the drive setting constant does the master knob affect power to the preamp tubes, power tubes, or both?

I think I understand that on a two channel (switching) amp with a true Master volume knob, the channel specific vol/lvl knobs affect the respective preamp, and the Master volume affects power to the power tubes????? So on an amp like the BDRI without a true Master volume, how does it work?

For you knowledgable electronics readers, I'd appreciate insight on this...Thanks

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Post subject: Re: Tech. Question about the BDRI
Posted: Mon Apr 11, 2011 3:44 pm
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I don't know exactly what you are asking, but the "Clean" volume and "Master" volume have nothing to do with each other and are not in the circuit at the same time. The Master volume is only in the circuit when you are using the Drive channel/Drive volume control (in which case the Clean volume control is not in the circuit). The Master volume is a true master volume for the Drive channel.

Here is the service manual for the BDRI. Look at the schematic on page 11 and you can see which control is in use for each channel.

http://www.blueguitar.org/new/schem/fen ... eissue.pdf

In my opinion, adding the volume pot is just introducing an unneeded control and extra circuitry. I have controlled the overall loudness in my BDRI by replacing the 12AX7s in V1 and V3 with a 5751 in V1 and a 12AT7 in V3. This reduces the overall gain of the amp and allows you to operate the various volume controls in a smoother part of their curve, thus avoiding the big jump in volume between 2 and 3 on the controls. The amp is just as loud with everything cranked, but the controls are much more useable.

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Post subject: Re: Tech. Question about the BDRI
Posted: Mon Apr 11, 2011 4:13 pm
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Thanks for the response, Bill.

Perhaps my post is a little confusing since the BDRI calls the volume or level "Master" on the Drive channel and I referred to another common design in amps that has a true Master volume which control volume of both channels. I am aware that on the BDRI that "Volume" (clean chnl.) and "Master" (drive chnl.) are unrelated.

I've been looking for a solution (other than a speaker attenuator) to deal with two characteristics: the volume sensativity of the amp, and a way to add (not reduce) some gain especially on the drive chnl. I have changed tubes targeting increased gain not decreased with minor success.

This box, while certainly being "extra circuity" has addressed the volume sensativity issue and possibly added some gain. My questions were intended to see if more power is going to both the preamp and power tubes as a result of having the amp volume turned up...i.e. as a result of turning up the vol. does more power go to the preamp tube whose output is reduced by the "box" prior to going to power tubes which also now have more power to them do to the amp vol. being turned up? (Sorry if this is confusing..I don't know how to better explain myself).

Am I hearing things, or could the amp now be "dirtier" due to using this box?

Thanks,
Bob

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Post subject: Re: Tech. Question about the BDRI
Posted: Mon Apr 11, 2011 4:48 pm
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By turning up the clean or drive volume and turning down the master or volume box, you are getting more preamp drive and distortion. You are not getting any more power tube distortion unless you really crank all of the controls up. The volume box really is nothing more than a redundant master volume control.

I really suggest that you look at the schematic in the service manual I attached. It will give you a better understanding of all the interrelationships between the various controls. As drawn, it shows the clean signal path active.

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Post subject: Re: Tech. Question about the BDRI
Posted: Mon Apr 11, 2011 5:22 pm
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Thanks Bill,

I will look at the link you attached. I just have to wait for an "off peak" download period due to restrictions on my internet satellite. I live in a very rural area and it's satellite or dial-up which is awful.

Between my last post and your most recent, I was thinking of how confusing I was making this, and thought the better question I should have asked would have been directed toward a 2 channel amp with each channel having a volume control plus a true Master volume control affecting both channels.

The question should have been: Is a true master volume control simply a pot which reduces the signal level coming from either preamp? And if so, has this "box" on the BDRI then in essence added the same feature?

If this is the case, I now understand that I am hearing more preamp distortion and no difference in power tube distortion.

Thanks for sorting through my convoluted question and steering me in the right direction.

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Post subject: Re: Tech. Question about the BDRI
Posted: Mon Apr 11, 2011 5:54 pm
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Let's try this: When you look at the schematic, you will see that the clean volume control comes between the two halves of V1. Typically, dependng on the output of your pickups and which input you are plugged in to, you have to turn the clean volume up to around 4 to 6 in order to start getting any breakup from the amp. This is a combination of preamp and power amp breakup. And it is LOUD.

Now, switching to the drive channel you will see that the two halves of V1 are now connected directly together for maximum gain out of V1. The drive volume is now between the tone stack and the input to V2. This allows you to overdrive V1 and V2 while using the master volume to lower the overall volume. But the power tubes are now not being hit as hard. The net result is that most of the drive is coming from the preamp and not the power amp.

Adding the volume box into the loop just adds a master volume for the clean channel, but the effect is the same as the original drive channel. Turning up the clean volume and turning down the volume pot results in more preamp drive and less power amp drive.

Switching to the drive channel with the volume box in the loop just adds another (and unnecessary in my opinion) master volume control. I do not believe that this is very useful unless you are really cranking the drive volume and the master volume is not enough to reduce the overall volume. Again, more preamp drive and less power amp drive is the overall result.

Personally, I feel the added volume box to be of very little practical value. But that is just my opinion.

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Post subject: Re: Tech. Question about the BDRI
Posted: Mon Apr 11, 2011 8:09 pm
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I had been playing the amp at around 2-1/2 to 3 on the clean chnl vol. in a 16X20 room w/ 10' high ceiling. My guitar has P-90's, vol. cntrls for each (set @8) plus a master vol. control lowered to 4. With these settings, it was as loud as I could stand it yet further lowering just made it sound muddy. It was very clean.

On the "drive" channel, I had the drive maxed out and the master was around 1-1/2 where 1 is silent. This was very difficult to control as a tiny movement of the master would shut it off or make it too loud. Distortion was minimal. I was looking for a bit more.

With the box in place, I have the clean chnl @ 6 and the drive chnl drive maxed and master vol. @ 4 (where it is not so sensative). The box is somewhere around half to give me the same volume as I had with the previously mentioned settings. The result (to my ears) is slight distortion on the clean, a little more distortion on the drive channel, no muddy sound, and a lot easier to control the overall volumes. I had expected, or at least hoped for, the improved ease of control, but the additional distortion was a surprise since everyone said there would be no additional power tube distortion, but no one mentioned anything about increased preamp tube distortion which seems to be occurring.

You and I probably are looking for different sounds, but I am quite pleased with the additional distortion on the drive chnl. The additional distortion on the clean channel is fine (it's minimal), but in a perfect world I'd have kept it the way it was. All in all, I'm pleased more than $20 worth, but was very curious as to what occurred.

I'm sure it's not for everyone, but for those of us who are less picky about the differences between preamp and power tube distortion (and maybe have difficulty recognizing the difference in a blind test) and want greater ease of control over the volume, it's $20 well spent.

If I had been satisfied with the sound of the drive channel with the drive set much lower and a corresponding increase in the master setting, the control sensativity would not have been such an issue and I'd never have purchased "the Box".

You've provided a lot of clarification...I appreciate it. And I'm still going to look over the schematics for a better general understanding even though I'll never get inside an amp to do anything other than perhaps bias check.

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Post subject: Re: Tech. Question about the BDRI
Posted: Mon Apr 11, 2011 9:22 pm
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I'm happy you're happy. :D

If all you ever plan to do is bias the amp, you definitely want to understand the schematic. I have done a lot of experimentation with the BDRI in regard to tube selection and bias adjustment. Feel free to shoot me a PM or just post your questions here.

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Post subject: Re: Tech. Question about the BDRI
Posted: Mon Apr 11, 2011 10:14 pm
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Hey guys,

I have the HRD, same issue. The reason being is the amp is built with cheaper linear pots. As dbs is a measured in a logarithmic scale, most amp volumes are fitted with logarithmic pots. When fitted with Logarithmic pots, we "hear" that the amp is twice as loud when going from 2 to 4, 4 to 8 or 5 to 10. When fitted with linear pots, as the BDRI and HRD are, you're pretty much maxing out the amp in dbs by the time you've hit the 5 mark. So thats why you're experiencing the issue you've got.

Now, the volume box you've purchased, thats sitting between your preamp (which has a volume control for the drive channel, thats the drive nob) and your poweramp. The volume box, as you've probably guessed by now, has a logarithmic pot in it. So it allows you to drop the volume with far more control than what the amp (with its linear pots) will allow.

If you're going for that clean, or pre-amp distorted sound, then you've nailed it with this setup. If you're trying to squeeze out the power amp distortion of a dimed tweed to give you that ball busting blues tone, probably wont nail it. Having said that, a decent tube-screamer / blues breaker type pedal to drive the preamps to breaking point, then dialing in the volume you want with your volume pedal could acheive pretty good results.

If you want to have everything cranked, and still play at lower volumes, thats what you need the attenuator for. It takes the power outputted by cranked power tubes, and resists it (basically converts it to heat), so that the volume outputted is lower, but the signal has already gone through the tubes running at full power.

The upside of this is better "tone", you'd have to hear it yourself to find out if you like it, its complete subjective to the player. The down side, and this is a very real downside, it basically takes everything that is outputted from your amp and diminishes the signal. the "wave" is basically the same, but its smaller. This means the distance between your rhythm volume and any boost volume is now closer, and in some instances you may not be able to max out your boost enough to over come this.

I think from what you have described you're happy with the current setup, hopefully this gave you an insight into an actual practical example of what the other option holds.

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Post subject: Re: Tech. Question about the BDRI
Posted: Tue Apr 12, 2011 10:56 am
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Impulse7 wrote:
Hey guys,

I have the HRD, same issue. The reason being is the amp is built with cheaper linear pots. As dbs is a measured in a logarithmic scale, most amp volumes are fitted with logarithmic pots. When fitted with Logarithmic pots, we "hear" that the amp is twice as loud when going from 2 to 4, 4 to 8 or 5 to 10. When fitted with linear pots, as the BDRI and HRD are, you're pretty much maxing out the amp in dbs by the time you've hit the 5 mark. So thats why you're experiencing the issue you've got.


If you would bother to look at the schematic, you would see that both the BDRI and HRD use audio pots for both the clean volume and the drive volume. A linear pot is used only for the master volume (midrange control also).

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Post subject: Re: Tech. Question about the BDRI
Posted: Thu Apr 14, 2011 12:56 pm
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Linear Taper pots aren't really cheaper, they're different. They were used to give the illusion of the HRD Series amps being much louder than they really are. It's a marketing ploy pure and simple. The amps is running pretty much full bore by the time you hit four on the volume dial. It's loud, no doubt, so is every other 40 watt amp. If you turn a HRD amp past four, it really doesn't get all that much louder. Getting loud so fast is the Hot Rod part. It makes you think it has a lot more volume than any other 40 watt amp. Truth is the amp can't cut a mix all that well. When I had my HRDlx, I was drowned out by someone with a DRRI. Why? The DRRI cut the mix better. My 20 Watt Egnater does the same thing. It can easily hang with most 50-75 watt amps when I run two 112 cabs and easily sounds louder than ny HRDlx ever did.

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Post subject: Re: Tech. Question about the BDRI
Posted: Thu Apr 14, 2011 1:21 pm
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63supro wrote:
My 20 Watt Egnater does the same thing. It can easily hang with most 50-75 watt amps when I run two 112 cabs and easily sounds louder than ny HRDlx ever did.


+1

My 12-watt Princeton, converted to a 2 x 12 piggyback with a pair of K120's, has no problem keeping up with an AC30TB, HRDlx, or even a '67 Pro Reverb.

Arjay

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Post subject: Re: Tech. Question about the BDRI
Posted: Thu Apr 14, 2011 4:13 pm
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63supro wrote:
Linear Taper pots aren't really cheaper, they're different. They were used to give the illusion of the HRD Series amps being much louder than they really are. It's a marketing ploy pure and simple. The amps is running pretty much full bore by the time you hit four on the volume dial. It's loud, no doubt, so is every other 40 watt amp. If you turn a HRD amp past four, it really doesn't get all that much louder. Getting loud so fast is the Hot Rod part. It makes you think it has a lot more volume than any other 40 watt amp. Truth is the amp can't cut a mix all that well. When I had my HRDlx, I was drowned out by someone with a DRRI. Why? The DRRI cut the mix better. My 20 Watt Egnater does the same thing. It can easily hang with most 50-75 watt amps when I run two 112 cabs and easily sounds louder than ny HRDlx ever did.


Clean volume and Drive volume = audio taper (A)

Master volume = linear taper (B)

Original Hot Rod Deluxe (NOT Series III):

http://support.fender.com/schematics/gu ... ematic.pdf

Original Hot Rod Deville (NOT Series III)

http://support.fender.com/schematics/gu ... ematic.pdf

Original Blues Deluxe (Master Volume is shown as an audio taper pot):

http://support.fender.com/schematics/gu ... ematic.pdf

Original Blues Deville (Master Volume is shown as an audio taper pot):

http://support.fender.com/schematics/gu ... ematic.pdf

Blues Deluxe/Deville Reissue (Master Volume is back to linear but clean volume and drive volume are audio taper):

http://www.blueguitar.org/new/schem/fen ... eissue.pdf

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Post subject: Re: Tech. Question about the BDRI
Posted: Fri Apr 15, 2011 7:41 am
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Been using a volume box on my BDRI for about a year. Have a Hot Plate attenuator trying to get rid off. The volume box does exactly what I needed and lets me keep my BDRI settings constant and I just adjust the "master volume" with the volume box for the situation.

Wouldn't be without it now.


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Post subject: Re: Tech. Question about the BDRI
Posted: Fri Apr 15, 2011 8:31 am
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Stinger22 wrote:
Been using a volume box on my BDRI for about a year. Have a Hot Plate attenuator trying to get rid off. The volume box does exactly what I needed and lets me keep my BDRI settings constant and I just adjust the "master volume" with the volume box for the situation.

Wouldn't be without it now.

I feel the same way. Did you notice a different (better) tone when using the Hot Plate and overdriving the power tubes?

To those familiar with various amps circuity:
One of my questions that wasn't addressed: In comparison to a two channel switching amp that has Vol. on the clean chnl., and gain and vol. on the "drive" chnl. plus a master volume that raises the volume on both channels...does placing the "box" in the effects loop of the BDRI effectively duplicate that of the previously described amp?

Thanks,
Bob

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