In search of a perfect attenuator

[Peter Daniel]

How about buffer unit before the TVC? How does that compare to the buffer before the resistor attenuator?

Does the buffer give some drive and bite to the TVC sound that it was missing?

I tried the TVC with a buffer but I was still getting more resolution "edge" with resistor based attenuator. However, that may depend on particular systems and personal preference. I cannot say that one or the other is definitely better.

 

[SamL]

According to some of the folks in Headwize, Shunted Linear Pots have varying impedance to the source which wll affect the sound quality.
http://tangentsoft.net/audio/atten.html

Have fun,
Sam

 

[A. J. Gandulfo]

ALEPH30 and ATTENUATOR

Dear Peter:

Congratulations for your work.

I purchased from you a DAC, 1 Premium LM3875, 1 Premium LM4780 Kits and from your partner, George a PRE T-1.

Please can you let me know if you still have Aleph30 boards in stock, and what about the selected Mosfets.
Wich is the 22KMF power supply capacitors Brand and type you recomend.

Regarding the Attenuator proyect I am interested to purchase one, can you tell me what do you thimk to offer and wich resistors Brand and type you preffer ?

 

[Peter Daniel]

Hi Georgio,

I will reply later in more detail to your post, however, I could not resist commenting right now on the quote below:

According to some of the folks in Headwize, Shunted Linear Pots have varying impedance to the source which wll affect the sound quality.

Thanks for an interesting link. The article didn't mention anything about affecting sound quality, it only comments on source's performance, which is not neccessarily the same:

"Another problem with this technique is that a shunted pot presents a varying impedance to the source as you turn the knob. A pot without a shunt resistor presents a constant impedance to the source, so the source's performance doesn't change as you turn the knob."

So, success with implementing such attenuator will depend on the source itself, but with well designed outputs, it shouldn't present major problems. My source has high current drive capability with 6 ohm output resistance.

I'm using series 10k resistor at the amp's input (fixed) so input impedance never goes below that value. I don't need wide range of volume setting for normal listening, and so far, I only needed shunt resistors values between 402R and 3.48K. That varies input resistance between 10402R and 13480R. I don't think it affect any performance.

I would not recommend linear pot for such application: only a switch with discreet resistors.

After saying that, the attenuator board I'm working on, has constant input impedance that does not change through all 130 steps.

 

[A. J. Gandulfo]

ALEPH 30 and ATTENUATOR

Dear Peter,

You answer another post, please read again mine.

Thanks and congratulations again.

 

[Peter Daniel]

Re: ALEPH30 and ATTENUATOR

Please can you let me know if you still have Aleph30 boards in stock, and what about the selected Mosfets.
Wich is the 22KMF power supply capacitors Brand and type you recomend.

Regarding the Attenuator proyect I am interested to purchase one, can you tell me what do you thimk to offer and wich resistors Brand and type you preffer ?

Thanks for appreciating my products

I will have more Aleph30 boards next week, as I ordered new batch. I also have one more set of output mosfets left.

Regarding 22,000uF caps I have some Siemens Sikorel, but those would be quite expensive. Another good brand could be Nichicon Super Through from Percy Audio.

The attenuator still needs programming to be done. The resistors I like here, are nude Vishays from Texas Components in series position, and with GC amps, Caddocks MK132 in shunt position.

 

[XELB]

Nice work Peter

I think you read people mind, I am just needing something like that

 

[SamL]

Hi Peter,

Thanks for your replay.

After saying that, the attenuator board I'm working on, has constant input impedance that does not change through all 130 steps.

You got me very interested now. Looking forward to the product release.

I'm using series 10k resistor at the amp's input (fixed) so input impedance never goes below that value.

Is it possible to have 25K resistor at the amp input? This will work better with my not so granty source like tuner and video.

Have fun,
Sam

 

[jleaman]

I to are also interested. Has there been any more progress on this ?

 

[Peter Daniel]

As mentioned in the other thread, the control board has been already fabriacated and my partner in that project, Veteran, is working on programming.

The input resistance can be set to any value.

 

[jleaman]

What i mean with progress was any idea when you will be offering this soon ?

 

[Peter Daniel]

No idea, I'm afraid.

 

[A. J. Gandulfo]

LOGIC

Dear Peter

You can design a logic using just 6 CMOS 8INput NAND's an another CMOS 4X2INput NAND's, a 23 positions one pole switch and a few not expensive components.

I understand these solution is just 23 steps.

Your solution is better, these is a cheaper one.

Nice job.

 

[johngalt47]

Any progress?

Peter,
Any progress yet?

 

[jleaman]

Options

Peter do you know what options you are going to have with this project Do you know if yuo are goig to have different models and stuff ones with more features or not ?

Just asking that is all.


Jase

 

[Peter Daniel]

I need to ask Veteran about progress, as he was developing software. The boards layout is completed, the only option might be different resistor choices.

On a control board therte is an option for source selector.

 

[jleaman]

I need to ask Veteran about progress, as he was developing software. The boards layout is completed, the only option might be different resistor choices.

On a control board therte is an option for source selector.

Right on thanks for the update peter.. Keep up the good work.

Jase

 

[cliffforrest]

schematics?

I am probably being v. stupid, but I can't find any links to a schematic for this attenuator.

I can more or less work it out from the spreadsheet, but there must be an easier way?

 

[cliffforrest]

Re: schematics?

I am probably being v. stupid, but I can't find any links to a schematic for this attenuator.

I can more or less work it out from the spreadsheet, but there must be an easier way?

<fx: drums fingers on counter>

Anyone minding the store?

 

[sonokeling]

stepped attenuator

I'd like to mention my experience with line signal attenuation. I'm not so familiar with the term shunt etc. So maybe this wheel reinvention, but here goes....
I've been looking at avoiding the resistor directly in the signal path, by draining the signal through the earth lead using a fixed resistor.
I've found that cheap carbon resistors work very nicely. The range is extremely limited, but I've found thatvalues between 4.7-6.8 ohm give good results with a variety of amps at home. I've got a Cyrus 1 which has direct input from the RCA's to the blocking capacitor on the main power amps with no resistor directly in signal. The resistor 'bleeds' the signal from this point to earth.
The sound is very stable and airy with low noise. Sorry for intruding on your discussion of esoterica!