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Stepped attenuator for Dynaco SCA-35?

GreatTone

GreatTone

Super Member
Has anyone replaced their volume control with a stepped attenuator? There are several options for sale online, from $12 which uses SMD resistors, to $100, which uses 0.1% resistors. I never use the loudness button, so unless it needs to be connected to make it work (I think it can just be left unconnected), a regular 3-lug pot should work. It's 250K btw. Worth doing or leave it alone?
 
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I have some stepped stuff, but even with 20 positions I find myself wanting something between two steps. All in my head I'm sure, like not being able to hit woods. An easy way to double the steps is to add a simple toggle and resistor to give you two ranges. If the signal passes through the attenuator, I say they are worth the trouble. If it doesn't, like a Haller shunt, a nice clean tracking pot will do for me. The one thing about is, just about anything you want to improve on, the iron in those will take advantage of it.
 
Hey, thanks! Yeah, the signal goes through the volume pots, so there's that possible improvement using the stepped with decent quality resistors. Looking at the schematic again, I see the temptation to remove the tone controls from the circuit, to avoid using the PECs, which have a number of caps/resistors that may not have the best audio characteristics. My main problem is I'm not sure I can stand to take it out of service long enough to work on it. The last time I did was over a year ago, when I implemented the EFB mod. Very large improvement, so I'm glad I did it. Maybe this is next.
 
Don't buy a DACT. They cost around $200.00 and they are junk. I had one that lasted a few months. Then it started to spit and drop out etc. They recommend that it only be cleaned with their own special brand of pot cleaner. Another $ maker for them.

I went out and bought an Alps Blue Velvet pot and I have never been happier!

By the way, if you do buy a new volume pot, get it at parts connexion.

http://www.partsconnexion.com/

They are an audiokarma sponsor!

Also, be aware of fakes. Ebay is full of fake pots. Parts Connexion has only valid suppliers.

later,
ken99
 
I tried a stepped attenuator volume control in a tube preamp, I tend to agree with jaymanaa about them.

I have installed several Alps Blue Velvet pots in amps and preamps and I was very happy in everything
I used them in.
 
I took the tone controls out of my SCA-35 by running through the filter switch.......found the directions through a link on AK. That way you can switch them in and out of the circuit if you like. To me it is am improvement and gives you quite a bit more usable volume at lower volume control settings.

I think the documentation was from DynaKit Parts.

I would be kind of like warm on the piped volume control as well. The good ones are intriguing but I think space would be at a premium in the SCA as well as the initial cost of a high quality unit.

Good luck!
 
ken99 said:
Don't buy a DACT. They cost around $200.00 and they are junk. I had one that lasted a few months. Then it started to spit and drop out etc. They recommend that it only be cleaned with their own special brand of pot cleaner. Another $ maker for them.

I went out and bought an Alps Blue Velvet pot and I have never been happier!

By the way, if you do buy a new volume pot, get it at parts connexion.

http://www.partsconnexion.com/

They are an audiokarma sponsor!

Also, be aware of fakes. Ebay is full of fake pots. Parts Connexion has only valid suppliers.

later,
ken99
Click to expand...

The DACT I was looking at was only $12, but I'm still glad you steered me away. If it weren't for the cost, I'd go for this:

http://www.ebay.com/itm/370773677209?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
 
I have a 100K stereo DACT volume control. I bought it maybe 4 years ago when prices were a little cheaper. It works great. I've never had problem one with it. I use it in a little EL84 cathode biased integrated amp I built. It's hot under that chassis but the DACT works fine. But Alps Blue Velvet work just as well--I can't tell a difference between the two.

The DACT did have a bit more even response at very very low volume levels..but I never listen at those whisper levels anyway...so it didn't matter in my case and I won't have a need to probably ever use a DACT again in the future.

Well...I take that back..if I ever build a nice headphone amp, I might consider a DACT.
 
OK, so an Alps pot may be just as good, it sounds like. Is is ok just to leave the loudness circuit out? Since there is no loudness tap on the Alps, and I never use it anyway.

PS: OMG! I just looked at the prices on the (real) DACTs! Almost $400 for a stereo 250K....yikes! No way!
 
GreatTone said:
OK, so an Alps pot may be just as good, it sounds like. Is is ok just to leave the loudness circuit out? Since there is no loudness tap on the Alps, and I never use it anyway.

PS: OMG! I just looked at the prices on the (real) DACTs! Almost $400 for a stereo 250K....yikes! No way!
Click to expand...

You won't be disappointed with the Alps. I don't have enough background on that amp to answer your loudness circuit question. As to your cost statement on the DACT...yeah...outrageous huh?
 
So I cleaned my old beat Alps blue pot and that was a real eye opener but is was effed up so I considered thishttp://www.ebay.com/itm/2P-23-Step-DALE-Attenuator-Volume-Pot-Stereo-Potentiometer-250K-Y-/400436775938?pt=US_Amplifier_Parts_Components&hash=item5d3be44c02 but couldn't wait so I sprung for a Goldpoint for $150. More bass detail and the clarity is pretty sweet. $100 would be better. Has a grinding feel to it. Guess I need to pull the trigger on some lube but I'm hesitant to muck with it.
 
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