Yes. And put a little pin on the rotary that actuates the 20dB step when you go through the ends, up or down depending on direction. Easy for a diy-er.
Jan Didden
Jan Didden
janneman said:
You read my mind Jan!! .. I thought about that afterwards. Mimmicking a multiturn control....
Rodolfo
Mechanically thats more difficult that it looks to be. It may be possible to get a movement that will do this but getting the pin to move the next decade one step requires some tricks. If you look at watch movements that do this they are not as simple as they seem. I have wanted to do this for years. There is a mechanism in the old Fluke differential voltmeters that works this way-
An externally hosted image should be here but it was not working when we last tested it.
I have a couple and the mechanisms are not smooth. They have a bigger problem with more digits but the core issue is the same.
How about a latching relay with a micro switch activated by said pin at each end? This does guarantee the biggest volume bang.1audio said:
Several old pre-amps had coarse and fine volume controls.
Interesting mental exercise. Not very practical. It is difficult to do any volume control right.
Depends on the architecture. If its 1 dB steps and 10 dB steps you still need six or more steps on the 10 dB level. The mechanical device to do this is one of these: Berg but they are very expensive. Electronically it can be done with some sequencing of relays but the clicks and pops suggest you would be better off with different solutions. Or all relays if you go there.
You only need one 'pin-switch' to get right. Everything else can be done with some glue logic.
I'd try a micro-switch for the 'pin-switch'. They can be had with levers that are very precisely adjusted.
Jan Didden
I'd try a micro-switch for the 'pin-switch'. They can be had with levers that are very precisely adjusted.
Jan Didden
Re. those TKD stepped attenuators:
Did anyone ever try to contact their local TKD sales reps? Considering the price of a unit I guess they might still be interested in selling even a single unit directly. I read about a DIY fair here in Germany last year where the German TKD representative was present; this tells me they ARE interested in DIY sales.
Did anyone ever try to contact their local TKD sales reps? Considering the price of a unit I guess they might still be interested in selling even a single unit directly. I read about a DIY fair here in Germany last year where the German TKD representative was present; this tells me they ARE interested in DIY sales.
Of course you can get TKD pots cheaper than $800 from the manufacturer, and more local sources. We did, but they are still too darn expensive for most people. However, our customers are not 'most people'. It is the same with auto tires, etc. If you want the 'best' be willing to pay for it.
Once, about 20 years ago, we used an Alps dual pot that we got from Radio Shack for $2.79 and it was actually pretty good. Not great, but pretty good. Kind of like a bargain tire for your car.
Once, about 20 years ago, we used an Alps dual pot that we got from Radio Shack for $2.79 and it was actually pretty good. Not great, but pretty good. Kind of like a bargain tire for your car.
I have gone from 2 knobs for vol plus 2 switches to control their range to a single Alps pot covering the full range, I wouldn't go back to the old system. Does it sound better? It doesn't sound any worse, I have not done a DBT. Ergonomics is important, I wouldn't rush to the next room to change a record even if it sounded better with the turntable out of the listening room.
Generally speaking, all else being equal, more pots is worse than less pots, BUT we have to be reasonable as well. Therefore, we usually try to minimize pots in series.
That is what we do as well. For the JC-2, we put the balance pots in series to change the overall gain.
Right. With an attenuator for each channel I could alter the balance, now I can't, so I would be very interested in any comments about the best way to do a balance control, I find them useful. Thanks.
Actually, I don't like balance controls and I have never seen a dedicated volume control that was really well made. On the Blowtorch, we just used dual precision attenuators. It works OK, but doesn't lend itself to remote control or user convenience.
I should have said 'dedicated balance control' The concept is OK, but I have never seen a really well made one.
On an early product I used a rotary switch and inserted a series resistance in one channel or the other with .5 dB steps. Centered it was out of the circuit. Cranked all the way to one side or the other it was 3 dB. Total correction was 6 dB in effect. If the program was worse than that it has real problems. If the system needs correction a balance control is the wrong place to fix it.
john curl said:
Thanks, that sums up the situation nicely.
I am going to try fixed series resistors feeding the tops of the stereo pot then connect the arms of a mono lin pot across these with the wiper earthed. Maybe no better than stereo pot in series with the vol pot but a good single pot should be cheaper than a ganged pot.
1audio said:
Good solution.
I only found a bal control useful after getting back into vynl. I have an all tube phono stage, no feedback, and swapping tubes usually produces some channel imbalance.
fredex said:
There is a good chance that more than gain will be different between the channels. If you have any cathode degeneration it should reduce the unit to unit variations a lot. If they remain the tubes must have big intrinsic difference that will also show in different frequency responses.
Early on the feedback effects of cathode degeneration were used in instruments to reduce the instability of gain etc. Tek tube scopes don't have feedback in the conventional sense on the fast amplifiers however careful design usually ensure they meet spec. with tube variations. Another possibility is tube end of life cathode aging.
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