Thanks Andrew
I have no problems with the current setup in terms of impedance (unless you can see some glaring issue?). The 47kΩ figure is from the amp's spec sheet - so I presume it includes the stock volume pot, is that what you assumed? That 50kΩ figure is for the stock pot already in there.
The reason I considered a stepper is because the L/R channel balance of the stock pot isn't good (measured ~5-10% difference depending on setting.
What are you improving by reducing the 50k to 10k, and is there a downside to this?
Also - do you have any recommendations on regular pots that are a bit better matched - or are you a fan of the stepped ones too? I'd appreciate any part suggestions - ebay or other (happy to build if needed). Goldpoint well outside of budget unfortunately.
This has been very good and quiet, with perfect balance. Very reasonable price,
and built in 10k to 250k values. Check out the internal photos.
DACT Type 21 Stepped Attenuator / Potentiometer 10K * D Shape Shaft * HiFi grade | eBay
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I agree with Ray. Those Chinese stepped attenuators are easily a "best buy" when it comes to reasonably priced volume pots.
Carbon pots(ALPS included) don't even come close when it comes to channel balance.
My first choice would be the Goldpoints, but they're over 10 times the price of the Chinese DACT Types.
Carbon pots(ALPS included) don't even come close when it comes to channel balance.
My first choice would be the Goldpoints, but they're over 10 times the price of the Chinese DACT Types.
I have had one of these for years, it's extremely well matched even at very low levels, and this is a very good price Alps Black Beauty Audio Taper Potentiometer Rk40312 Log Stereo Pot 50k Rk40 | eBay I've just read in the description that it says it's a stepped pot, mine isn't, it looks identical, I would check that if I were you
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your ratio of source impedance to receiver impedance is not good.
It is usual to look for at least 1:5 source:receiver and preferably >1:10, I prefer to aim for 1:20
Your 50k vol pot has an output impedance of {50k+Rs}/4 i.e. ~12k7
Your receiver impedance is 47k. That gives your impedance ratio ~ 1:3.7
I consider that far too low.
A 10k vol pot will give you ~ 1:18 and the 10k is more capable of driving the interconnect.
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I'm pretty sure it is not a switched resistor type. It does have clicks from a detent wheel.
Yes, Radio Shack used to sell a $2 Alps stereo pot with an external detent wheel.
It was a very good control otherwise, so I just removed the detent wheel to allow
continuous rotation. I used those for years for Dyna PAS upgrades.
it was similar to this one. https://www.radioshack.com/products...lume-control?gclid=CMqKneSO3tMCFVEdgQodo6MHnQ
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Nice! At first glance I assumed it was a normal pot for that price. I didn't find those when I looked, glad I asked now. Thankyou.
What's the friction like to turn it compared to a non-stepped knob, do you think a motor drive from a regular volume control (eg. std motorised blue Alps) would struggle to turn it or be okay? I could always gear down my drive system anyway, just curious - motor thing is a future project.
I feel like you're not understanding correctly, the 47kΩ value is the rating for the whole amp (from the spec sheet, i.e. at the RCA input) and the volume control already exists as part of it (so I'm not adding an external 50kΩ volume pot to a 47kΩ input impedance amp). I am unsure of the input impedance of the power amp stage itself (which is probably what you're thinking of).
My understanding was that the ratio of source impedance to amplifier impedance in this case was just the 50Ω (DAC) to 47kΩ?
Please correct me if I'm wrong though. I'm happy with the setup as-is aside from the balance mismatch so would prefer not to risk new problems.
The torque is very similar to a regular pot, and you don't notice any clicks.
There are versions with flatted 1/4" shaft, and a knurled shaft. Bushing size is metric.
Sounds perfect, thanks again.
I'm pretty tempted to buy one right away (in the same impedance as the standard built-in pot, which I'm replacing here), but Andrew has me confused so I'll wait for a response before deciding on impedance value.
In your system, there should be no problem at all with the usual 10k pot value.
Unless there's a problem elsewhere (acoustics, etc.), the channel balance will be
rock-stable centered throughout the entire range of the volume control.
Remember that the body of the control is intended to be grounded via the
mounting on the panel.
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I don't understand how you guys find 21 steps (or 24) sufficient ? I have a Noble pot which isn't a true DACT-style but has indents so that when you rotate it you get discrete steps even though it's 'just a pot'. I found that I wanted to set a volume in-between the indents and although I could persuade it to kind of balance in this no-mands-land it was annoying so I replaced it with a blue Alps. I concluded that I need a smoothly varying pot rather than one with indents, or rather than a DACT style. Somtimes a source signal is stronger or weaker and the volume control has to be controllable at 3 o'clock and other times controllable at 7 o'clock. I do wish the chinese guys would figure out how to make an affordable 50 step option.
I use 10k for a passive volume control, seems to me a good compromise between not loading the source, not being too high to 'drive' the amplifier and also a common value that's easy to buy.
I use 10k for a passive volume control, seems to me a good compromise between not loading the source, not being too high to 'drive' the amplifier and also a common value that's easy to buy.
You can add a series resistor before the pot for more attenuation, switching it out when you
want more gain. I think your problem may be with the taper.
Then there's this type: http://www.vaneijndhoven.net/jos/relaixedpassive/index.html
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Perhaps it is the taper, if I had more control at low volumes it would be better - I should check to see if that Nobel pot is linear or log.
Measure the resistance at the center of rotation, it should be around 1/10 (-20dB)
of full scale for a log pot.