Reducing gain on Bride of Zen?

Yochim · 11th September 2002, 07:02 PM

Hello All,

I will try to make this my last post on the BOZ

. I built a BOZ for my friend and it sounds great but we can not get past the second click on the volume control as things get very loud very fast.

I am thinking that to decrease the gain I should increase R108 & R208.

Am I right on this?

Thanks for any info.

Y.

eLarson · 11th September 2002, 07:22 PM

Increasing R108 (and R208, if that is the right-hand channel) would do it. You could also decrease R104/R204. Or some combination of both.

Increasing R108 would tend to decrease your bias current as well. If you want to maintain the 40 mA bias, you should bump up the gate voltage accordingly using P102.

Alternately you could also put pads on all of your inputs to a greater or lesser degree (whateve it might take to get all of them at roughly the same input level) and put your volume control at the output. You'd get the added benefit of having all the volumes be roughly equal when you switch from one to another.

Regards,
Erik

jh6you · 11th September 2002, 10:26 PM

I
recommend
an
input
attenuator.

JH

Yochim · 11th September 2002, 10:43 PM

Hey Guys, thanks for the replys.

jh6you, should I place an input attenuator before the input caps.? Also do you have a recommended value for the attenuator.

I thought perhaps putting a resistor in front of the outputs.

Y.

eLarson · 12th September 2002, 12:58 AM

Yochim,

First things first: I would put it before the cap.

I'm planning on rebuilding mine with fixed attenuation for each input. That way I won't have to fiddle with an extra knob, or add the extra expense of another variable attenuator.

On the plus side all of my inputs will have close to the same amplitude going into the amp so I won't have to worry about remembering to turn down the volume before selecting my CD player after listening to the tuner.

That's all personal preference, of course.

I suppose I could get by with a 3 position bat-toggle switch labeled "mute", "about right" and "loud".

The plus side to having two variable attenuators is that you can vary input level and the output level at will.

Hope that helps,
Erik

jh6you · 12th September 2002, 08:20 AM

Hi Yochim

Yes, in front of the input cap and any of fixed or variable attenuator.
My successful experience was with the standard 100K.
But, any size would work.

Regards

JH

Nelson Pass · 12th September 2002, 07:43 PM

I would prefer to see maybe a 25K pot for the
best performance.

Yochim · 12th September 2002, 08:21 PM

Thanks again everyone and Mr. Pass I will try a 25K precision dual pot.

Ciao.

Y.

Nelson Pass · 12th September 2002, 08:34 PM

Semi precision will probably do.

Yochim · 13th September 2002, 02:01 AM

One final question please, I am having a problem finding a dual gang pot. locally, if I use two pots. is there a technique for measuring the level of each channel with my multimeter for level adjustment?

Thanks.

Y.

11th September 2002, 07:02 PM	#1
Yochim diyAudio Member Join Date: May 2002 Location: Vancouver, B.C., Canada	Reducing gain on Bride of Zen? Hello All, I will try to make this my last post on the BOZ . I built a BOZ for my friend and it sounds great but we can not get past the second click on the volume control as things get very loud very fast. I am thinking that to decrease the gain I should increase R108 & R208. Am I right on this? Thanks for any info. Y.

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11th September 2002, 07:22 PM	#2
eLarson diyAudio Member Join Date: Aug 2002 Location: Gaithersburg, MD	Increasing R108 (and R208, if that is the right-hand channel) would do it. You could also decrease R104/R204. Or some combination of both. Increasing R108 would tend to decrease your bias current as well. If you want to maintain the 40 mA bias, you should bump up the gate voltage accordingly using P102. Alternately you could also put pads on all of your inputs to a greater or lesser degree (whateve it might take to get all of them at roughly the same input level) and put your volume control at the output. You'd get the added benefit of having all the volumes be roughly equal when you switch from one to another. Regards, Erik

11th September 2002, 10:26 PM	#3
jh6you Account Disabled Join Date: Aug 2002 Location: Near to the Pacific Ocean	I recommend an input attenuator. JH

11th September 2002, 10:43 PM	#4
Yochim diyAudio Member Join Date: May 2002 Location: Vancouver, B.C., Canada	Hey Guys, thanks for the replys. jh6you, should I place an input attenuator before the input caps.? Also do you have a recommended value for the attenuator. I thought perhaps putting a resistor in front of the outputs. Y.

12th September 2002, 12:58 AM	#5
eLarson diyAudio Member Join Date: Aug 2002 Location: Gaithersburg, MD	Yochim, First things first: I would put it before the cap. I'm planning on rebuilding mine with fixed attenuation for each input. That way I won't have to fiddle with an extra knob, or add the extra expense of another variable attenuator. On the plus side all of my inputs will have close to the same amplitude going into the amp so I won't have to worry about remembering to turn down the volume before selecting my CD player after listening to the tuner. That's all personal preference, of course. I suppose I could get by with a 3 position bat-toggle switch labeled "mute", "about right" and "loud". The plus side to having two variable attenuators is that you can vary input level and the output level at will. Hope that helps, Erik

12th September 2002, 08:20 AM	#6
jh6you Account Disabled Join Date: Aug 2002 Location: Near to the Pacific Ocean	Hi Yochim Yes, in front of the input cap and any of fixed or variable attenuator. My successful experience was with the standard 100K. But, any size would work. Regards JH

12th September 2002, 07:43 PM	#7
Nelson Pass The one and only Join Date: Mar 2001	I would prefer to see maybe a 25K pot for the best performance.

12th September 2002, 08:21 PM	#8
Yochim diyAudio Member Join Date: May 2002 Location: Vancouver, B.C., Canada	Thanks again everyone and Mr. Pass I will try a 25K precision dual pot. Ciao. Y.

12th September 2002, 08:34 PM	#9
Nelson Pass The one and only Join Date: Mar 2001	Semi precision will probably do.

13th September 2002, 02:01 AM	#10
Yochim diyAudio Member Join Date: May 2002 Location: Vancouver, B.C., Canada	One final question please, I am having a problem finding a dual gang pot. locally, if I use two pots. is there a technique for measuring the level of each channel with my multimeter for level adjustment? Thanks. Y.

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