[wakibaki]

+1. I also found the Alps are not that good. Also, the 10 times rule can be 4 times according to the RCA
Radiotron Designers Handbook. Of course 100 times is complete nonsense.

---------------

Something to remember is that with DC output coupling, 20K May be ok. However, with capacitive output,
the size of the cap is very important not to weaken the bass response. I would check the output capacitor for size.
 
However, midpoint resistance of 20k (approx 2 o'clock rotation) is barely ok as the high frequency response
will be minimum at the mid resistance point. This is especially important if ICs are directly connected
(relatively high capacitance) to the wiper arm. Thus it is important that the balance control is near maximum or near
minimum rotation for the best high frequency response.

Cheers.

Steve

It's all very well to go 'Alps are not that good', but I don't see you making an alternate recommendation. Just a little something you might like to remember before you race to open your mouth to criticize.

As far as the rest of it goes, what I've said is based on the quoted specifications of the equipment. ICs don't have a high input capacitance, opamp input impedance is typically a high resistance, some hundreds of kohms minimum with at most 25pF in shunt, so with respect to the HF performance, irrelevant until you get to RF.

If you just go down the street, turn left, turn right, turn right again, you'll see a little lane on your left. Well, you don't go up there.

Cheers.

w

[Steve]

It's all very well to go 'Alps are not that good', but I don't see you making an alternate recommendation. Just a little something you might like to remember before you race to open your mouth to criticize.

As far as the rest of it goes, what I've said is based on the quoted specifications of the equipment. ICs don't have a high input capacitance, opamp input impedance is typically a high resistance, some hundreds of kohms minimum with at most 25pF in shunt, so with respect to the HF performance, irrelevant until you get to RF.

If you just go down the street, turn left, turn right, turn right again, you'll see a little lane on your left. Well, you don't go up there.

Cheers.

w

1) Just agreeing with Destroyers of smiles, and others presented alternatives did they not, including you??

For these reasons I suggested a 20k pot or switched attenuator

and

The Blore Edwards Type 72 30-way switch is good.

2) ICs are interconnects, which can have very high or very low capacitance. As such, the
high frequency response could suffer in the high gain channel unless the control is toward
maximum or minimun rotation and IC capacitance is small. And yes, one should add the
input capacitance of the next active device to the IC's capacitance if directly connected to the wiper arm.
(If just IC chip and no IC (interconnect), no problem.)

3) My comments were directed towards the public's benefit, what to look for, how things work,
what to consider when modifying a system.

I am sorry you misunderstood what I was discussing.

Cheers.

[4krow]

I am in agreement with Wakibaki about being able to attenuate one channel. My room has a similar problem and I have been using a Glassware volume control design that uses 3 separate 6 position switches. The center stereo switch controls the volume in 6 db steps, and each flanking switch adjusts the volume the left or right channel only, by 1.5 db. In total, there are 36 positions available. In my system it has worked really well.

[jackman]

Roscoe,
I have the same situation.   Luckily, my SAS 10A preamp has dual mono volume controls.  I adjust one until the center image is in the correct spot.  It's pretty easy.

I'm not going to comment on pots because its not my area of expertise.  That switch box on the previous page looks like a complete disaster.  I'd make sure there is a good return policy before going in that direction.

Good luck!  I look forward to getting together soon in Chicago.

Cheers

Jack

[wakibaki]

I'm not going to comment on pots because its not my area of expertise.  That switch box on the previous page looks like a complete disaster.  I'd make sure there is a good return policy before going in that direction.

Pots aren't your AOE but 'switchboxes' are? It's easy to sit on the sidelines and heckle. Post a design of your own and maybe you'll be taken seriously.

Jealousy will get you nowhere.

w

[wakibaki]

I am sorry you misunderstood what I was discussing.

If you post 'IC' and expect anybody to interpret it as anything other than Integrated Circuit you will be misunderstood.

w

[Steve]

If you post 'IC' and expect anybody to interpret it as anything other than Integrated Circuit you will be misunderstood.

w

They will? ICs have meant interconnect cables for literally decades, since at least the 50s.
Unfortunately ics can now also mean integrated circuits as well. However, I saw no
mentioned of an integrated circuit before I posted. If so, I missed it.

As we go through, I merely expanded upon your experience, what we should
look out for, and what you actually presented.

1) You posted an outboarded passive pre, volume control. As such, an IC is necessary.

2) This means the wiper arm is directed connected to the interconnect cable and its capacitance
plus the amplifier input capacitance plus any stray capacitance.

3) With an IC (interconnect cable) one will not have 25pf but
much higher capacitance, thus lower frequency response. Some will attempt this
and should know the possible outcome.

4) With a total IC, amplifier input capacitance, and stray capacitance of just 90pf and
5k (your 20k ohm pot at mid resistance, two parallel 10ks), your -3db point will be approximately 155khz.
This means that there will be some loss of high frequency response well within the 20khz band.

With 200pf total, the -3db point will only be approximately 70khz. One will be down approx -1db at 30k to
35khz. The highs will obviously be negatively affected. Very important to check IC (interconnect) capacitance.

No harm meant by me. It is good, though, for the public to know all the possible combinations, including
worst case scenario, and the possible out come.

For instance, if the control were installed within the amplifier, with no IC, the
scenario is much much better. But it is always good to keep the capacitance to a minimum,
as you indirectly suggest.

Cheers.

 

[jackman]

Pots aren't your AOE but 'switchboxes' are? It's easy to sit on the sidelines and heckle. Post a design of your own and maybe you'll be taken seriously.

Jealousy will get you nowhere.

w

Let's see...a guy is having issues with the balance of his system and asks people for suggestions on a DIY balance control to use with his existing preamp.  He also uses a digital EQ (which can also be used as a preamp) with the system.  You propose the addition of a passive preamp to use with his system as a suggested correction?  I'm not an expert and have never designed any electronic gear but I would have to think there is a simpler solution. 

Is adding a passive preamp in front of his existing active preamp and digital EQ the simplest solution?  I'm not familiar with the DSpeaker Anti-Mode but was going to suggest contacting the company to see if it has a balance control or if the EQ can be used to correct the problem.  A passive preamp in front of an active and the Dual-Core would essentially give him three preamps in the signal path.  That seems like a complicated solution to a simple problem, but I'm merely a sideline heckler, so I might be wrong.   

[wakibaki]

Steve

f3dB=1/(2*pi*R*C)

@ 5k and 90pF that gives 356.6k not 155k.

Get your facts straight.

You're making a mountain out of a molehill to try and make yourself look good

w

[wakibaki]

jackman

Get your facts straight.

I suggested he use a pot. Read the whole thread.

I'm retired. Financially secure. My designs are given away, they're not for sale.

w

[jackman]

So you are getting a CNC mill to produce a single piece of gear for yourself?  Sounds interesting.  I must have imagined the passive preamp you posted on the previous page.   

It's cool that you give your designs away for free.  Has anyone ever built one if your designs?  I'm sure they are worth what you charge for them. 

Cheers

Jack

[Steve]

Steve

f3dB=1/(2*pi*R*C)

@ 5k and 90pF that gives 356.6k not 155k.

Get your facts straight.

w

Correct, my mistake. Interpolated incorrectly from a textbook I had handy. With
200pf, the -3db is only approx 160khz.

However, Jackman's and my points still apply, in order to help the public.

We simply addressed the variables to help the public understand what to
watch out for in their own systems, how it affects the performance. We were certainly
polite about it. (See my previous posts on what to look for.)
There is no need for your behaviour when we are helping the public.

Jackman is correct Roscoii, for maximum benefit, get rid of the redundency, simplify
if possible as patch work is never optimum, although if finances
are involved, we all understand.

Cheers.