So I did try all those different potentiometers

[Vikash]

http://www1.jaycar.com.au/productView.asp?ID=RP8760&CATID=&keywords=potentiometers&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=

I went for the 10k.

 

[KT]

I put an Alpha 50k pot in a Sonic Impact amp and the pot is, indeed, very nice. Great rotational feel.

If anyone has an extra 10k log Alpha that they would like to swap for a 50k log version of the same, please contact me.

I bought a bunch of the 50k pots, probably more than I'll need for a while, and would like to try the 10k.

Thanks,
KT

 

[Joe Rasmussen]

Calling from Munich...

Hi Guys

Munich calling.

Glad there is such an acceptance of the Alpha pot, as I said before, as in the JLTi Mk1 review in tnt-audio, I consider them a minor miracle. BTW, the way I discovered them was entirely by mistake, in fact I picked up the wrong pot... There is a word for that: Serendipity. But too good to sit on it, so I volunteered... I hate conductive plastic pots, haven't heard any that isn't tonally flawed.

Now I do want to make a point on these comparisons, and this is in no way disrespect to Peter, but I would rather have selected two sets of resistors as L & R voltage dividers to, say, -20dB or whatever suits the setup, then set the 'test pot' to match the output of the dividers. Best to measure with a test signal, or test CD, with a suitable sine signal (1KHz is fine as the voltage meter accuracy is not critical), do it on the speaker terminals.

In fact average out L & R by adding and dividing by two. Match by better than 1% (or 0.1dB)

Choose resistors that you consider neutral, but IMHO pots are far worse than decent resistors. But whatever you might think, all the pots should be compared at the same amplitude/volume.

In Munich, just attended ETF 2004 (European Triode Festival) and met up with Lynn Olson, John Atwood, Morgan Jones, Gary Dahl, Steve Bench and Gary Pimm, all of the U.S. OOPS! MJ is a Brit! Then there was our own Franz Gysi, illuminating us from all the way from Switzerland. 😀 He sold a pair of cute little transmission line boxes to Allen Wright. Because of that I was deprived of having a nap, couldn't recline the seat on the way back to Munich.

Main theme of ETF 2004? Push-Pull is making a come-back! And so are GCs, right? PP, that is. OK, they were talking tubes, but we like both, don't we?

Off to Copenhagen tomorrow to see some relatives. Keep buying those Alphas, they are nice! If you like them, then I like you! 😉

Joe R.

 

[homer09]

Improving the PEC pot further?

What do you guys think of fake lawing the PEC linear pot? Do you think this would yield an even better volume control than the log version of the pot?

Digikey sells the mono versions of the pot in both standard log and extra long life linear versions for ~$12 CAN. If what is stated here: http://sound.westhost.com/project01.htm is true for this pot also, then will an extra long life fake lawed linear PEC carbon pot outperform the standard log PEC carbon pot?

Is it only worth it for the stereo version or also some gain to be had in the dual mono setup?

 

[ThorstenL]

Re: Improving the PEC pot further?

Konnichiwa,

What do you guys think of fake lawing the PEC linear pot?

Absolutely. I have been repeating for the better part of the last 10 Years like a mantra "The cheapest lawfaked carbon pot tends to sound better than expensive Audio Taper Audio grade pots". There is even a reason for that.

If what is stated here: http://sound.westhost.com/project01.htm is true for this pot also,

Likely.

then will an extra long life fake lawed linear PEC carbon pot outperform the standard log PEC carbon pot?

Probably.

Is it only worth it for the stereo version or also some gain to be had in the dual mono setup? [/B]

Sure. If you want to go one better on sound use a pair of precision 10 or 20 Turn wirewound pots, you can gang them together and adjust the volume very finely. I know of nothing better short of a TVC and a REALLY WELL implemented "true ladder" stepped attenuator.

Sayonara

 

[homer09]

Kuei Yang Wang,

Thanks for the confirmation on linear pots. but, i still think turning a volume control 3 or 4 rotations is a bit annoying especially if im using separate mono controls.

so im going the fake lawing route (no offence to your preference!). ive seen lots of different opinions on value of fake law resistor anything from 1/6 to 1/20. is there a way to calculate the graph of a fake lawed pot based on resistor values (in excel for example), would this not put an end to the argument? best log curve aproximation wins....

im using this volume control in a NI gainclone based on brainGT's boards. I was thinking of a 25K log pot. What value of linear pot do i need to emulate the same volume curve?

 

[ThorstenL]

Konnichiwa,

i still think turning a volume control 3 or 4 rotations is a bit annoying especially if im using separate mono controls.

Simple solution. Use gears and gang the controls. I'd probably use a 1:10 gear with a big knob as the main control and have below left/right the individual controls. Then simply use rubber belts and suitable pulleys to gang the individual controls to the "master" Button. Then you can adjust the balance individually if needed.

(no offence to your preference!)

Non taken.

Back in the 80's we used a steelwire & pulley system to turn 10-Turn wirewound pots into precision slider/fader volume controls for mixing desks (individual channels and masters). Using these we got excellent sound, excellent sound and resolution etc. We used them in an feedback arrangement to get accurate "log" responses.

so im going the fake lawing route. ive seen lots of different opinions on value of fake law resistor anything from 1/6 to 1/20. is there a way to calculate the graph of a fake lawed pot based on resistor values (in excel for example), would this not put an end to the argument? best log curve aproximation wins....

I would not atempt to approximate the best log curve. That is because normal volume controls do not approximate a log curve well. Yet in systems with a well derived gain structure they usually produce good control. What you will find with normal "Audio Taper" pots is that at 1/2 rotation you have around 20db attenuation.

This suggests a 20:1 ratio for the Pot to lawfaking resistor, in other words a 1M Linear Pot gets a 50K lawfaking resistor and a 500K one gets a 25K lawfaking resistor. Lower pot values are not particulary useful for lawfaking, I'd draw the line at 250K Lin....

I have found in practice that the 20:1 yields a well usable volume contol, the 6:1 is very hard to use....

I was thinking of a 25K log pot. What value of linear pot do i need to emulate the same volume curve?

If you take the passimistic view than the value of the lawfaking resistor becomes the nominal (minimum) value of the Pot.

Sayonara

 

[homer09]

Simple solution. Use gears and gang the controls. I'd probably use a 1:10 gear with a big knob as the main control and have below left/right the individual controls. Then simply use rubber belts and suitable pulleys to gang the individual controls to the "master" Button. Then you can adjust the balance individually if needed.

I was also thinking of some kind of pulley system. But i dont understand how you can gang up both channels to a master control yet retain the ability to control channels individually. Wont turning the left channel also turn the master control as well at the right channel since they are all linked by pulleys/gears? Do you have any pictures or simple drawings of an effective pulley system?

We used them in an feedback arrangement to get accurate "log" responses.

What is a feeback arrangement?


Have you tried the technique outlined in the following site? what do you think of it?

http://www.audiosold.com/passivepre.htm

And finally, any recommendations for 10 turn wire wounds that are reasonably priced? (~25$ CAN each)

Thanks for the advice, there is nothing better for a newbie than learning from an experienced DIYer.

 

[ThorstenL]

Konnichiwa,

I was also thinking of some kind of pulley system. But i dont understand how you can gang up both channels to a master control yet retain the ability to control channels individually.

Make sure your rubber belts, strings etc allow some minimal slippage.... ;-)

Do you have any pictures or simple drawings of an effective pulley system?

No, I have not worked with that kind of stuff of well over a decade.

What is a feeback arrangement?

I meant feedback arrangement, a circuit where a linear pot is looped into the feedback such that a true log curve of attenuation ves percentage of trave is obtained.

Have you tried the technique outlined in the following site? what do you think of it?

http://www.audiosold.com/passivepre.htm

Yes, I did not feel it any better than lawfaking a good linear pot and it has the same or worse drawbacks. Plus it requires an audio taper pot or a switched attenuator, if you already invest all the money for a switched attenuator (as in that project) why not do the job properly.

And finally, any recommendations for 10 turn wire wounds that are reasonably priced? (~25$ CAN each)

Not off-hand. I have in recent times not looked around for them that much. But you should find them in any well sorted industrial electronics parts catalogue, usually also suitable gears and so on....

Sayonara

 

[kimschips]

Hello all.
Alps RK40 10K potmeter?

I like it and it sounds almost good as a attenuator with resistors!

Downside is price and has no motor.

It´s now sold for about 40$ in Denmark

Please comment if you have something better/or as good with motor or any experience with the RK40

Best regards
Kim

 

[Bgt]

just placed the Dact CT2-10k-2 in my passive....awsome. I had an Alps, sounded Ok but this is more honest.

 

[vmac011]

Greetings to all members of this happy congregation!
I'd like to draw your attention to cheep step attenuator available in kit (or assembled format +A$20).

http://www.diyfidelity.com.au/product_info.php?cPath=0_33&products_id=32

I live in the land where Alpha pots are aplenty, in fact, Jaycar store is just 100 meters away. DIY Fidelity is a kilometer further up the road. Someone might say "lucky bastard".
Being a naturally inquisitive, it's needless to say I've compared them both.
Alpha is very, very good, but the attenuator win by a mile!

 

[Elso Kwak]

DACT

The DACT will be rotten in a few years. 10µm of gold, hahahaahaa

 

[Bgt]

thats surely not expensive. I'll try it and compare it to the DACT attenuator.

 

[Bgt]

Re: DACT

The DACT will be rotten in a few years. 10µm of gold, hahahaahaa

Is this a joke or not??😕

 

[Bgt]

Re: DACT

The DACT will be rotten in a few years. 10µm of gold, hahahaahaa

What do you suggest?

 

[Elso Kwak]

Re: Re: DACT

Is this a joke or not??😕

Hi no joke. I have four rotten Elmas which are esentially the same.
Now have Shallco with solid silver contacts, 47 positions. Available from Michael Percy. For selectors Electroswitch.
http://www.percyaudio.com/
😎

 

[carlmart]

Re: Re: Re: DACT

Hi no joke. I have four rotten Elmas which are esentially the same.
Now have Shallco with solid silver contacts, 47 positions. Available from Michael Percy. For selectors Electroswitch.
http://www.percyaudio.com/
😎

Wow, I didn't know about the Elmas. Why does that happen?

I bought a 27 position Electroswitch some time ago from Parts Connexion, but I haven't yet assembled it. It looked much better than the Elma


Carlos

 

[Elso Kwak]

Elma

see
http://db.audioasylum.com/cgi/m.mpl?forum=tweaks&n=44474&highlight=elso+elma&r=&session=
😎

 

[Bgt]

The alpha pots are carbon. I remeber them getting bad after some time. They would start making noise when you use the on the same position for a long time. Thats why I switched to the blue Alps pots a long time ago.