Is there a certain set of somethings that I need to do to set up a differential (balanced) B1. I actually need a balanced input, single ended output. I could use a That 1280 at the input of my single ended B1, but...
You could do that with a transformer, or a opamp circuit, or something like the aikido cathode follower
Cool, thanks! One of these days I'll manage to repair (or have repaired) my actual (non-diy) Krell KSA-80B. Then I will be seriously wanting a balanced B1. There are nice instructions for a balanced BA3. Maybe I'll do that.
An instrumentation amp converts bal to unbal using three amplifying stages.
The first two stages (non inverting) could be B1 and the third stage (summing) could be an ordinary audio quality opamp.
The first two stages (non inverting) could be B1 and the third stage (summing) could be an ordinary audio quality opamp.
Would the two B1s have to be immaculately matched, as is the case with other differential amps? I assume .1% resistors and carefully matched jets. Should be doable with a circuit as minimal as the B1.
No, it's the impedances that must be exactly matched.
A balanced input is actually a balanced impedance connection
It's the cable and the two end termination impedances that must be balanced.
The transmit end must have matched resistances and matched capacitances. Hopefully layout will sufficiently match the inductances.
The receive end must have matched resistances and matched capacitances. The layout will hopefully, sufficiently match the inductances.
The cable and plugs/sockets must be of balanced style.
A balanced input is actually a balanced impedance connection
It's the cable and the two end termination impedances that must be balanced.
The transmit end must have matched resistances and matched capacitances. Hopefully layout will sufficiently match the inductances.
The receive end must have matched resistances and matched capacitances. The layout will hopefully, sufficiently match the inductances.
The cable and plugs/sockets must be of balanced style.
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Thank you very much. You Pass Labs forum guys are great!! Such an amazingly rich resource, thanks again.
I would like to add a 3.5mm stereo output socket to the front panel of my B1(to output to a headphone amp), is it a simple case of adding a simple dpdt switch and connecting the input of this to the boards L & R outs then connecting the switch outputs to the original phonos plus the 3.5mm socket or am I mising something?
B1 ready. Pictures here:
http://www.diyaudio.com/forums/pass...-your-diy-pass-amplifier-282.html#post4061215
http://www.diyaudio.com/forums/pass...-your-diy-pass-amplifier-282.html#post4061215
Using stepped attenuator in design
I note that Mr. Pass uses a linear pot instead of a log one. Does anyone know why? I was thinking of constructing a stepped attenuator to use with the design, but now am unsure of the calculations for the resistors.
Could someone point me in the right direction?
Thanks,
Jazzzman
I note that Mr. Pass uses a linear pot instead of a log one. Does anyone know why? I was thinking of constructing a stepped attenuator to use with the design, but now am unsure of the calculations for the resistors.
Could someone point me in the right direction?
Thanks,
Jazzzman
search stepped attenuator calculator
dozens will turn up.
I like the Akido but they got the relative resistance ranges, between the small steps and the big steps, all wrong and it needs re-calculating to get it to work properly.
Three-Switch Stepped Attenuators & Aikido SE Amplifiers
dozens will turn up.
I like the Akido but they got the relative resistance ranges, between the small steps and the big steps, all wrong and it needs re-calculating to get it to work properly.
Three-Switch Stepped Attenuators & Aikido SE Amplifiers
Thank you for the response, AndrewT.
I guess to be more precise, my question related to the recommendation for a linear pot in the circuit. Maybe I am just overthinking this, but I am aware of a method of simulating a log pot by attaching a resistor between the wiper and ground of a linear pot. (Rod Elliott explains the principle in his project one, see ESP - A Better Volume Control) Looking at the B1 schematic, I do not see such a resistor, but I am not sure that something equivalent might be in there. (And hence, the recommendation for the use of a linear pot.) If so, I could goof up the law of the pot by using inappropriate values for my resistors. The calculators are not designed to take that type of circuit into account. So my question really is, do I need to worry about this at all? If the circuit compensates for a linear pot, can I just use the calculations for a linear pot? If the circuit does not compensate for a linear pot, what is the rationale for not using a log pot?
Thanks for any input anyone can give me.
Jazzzman
I guess to be more precise, my question related to the recommendation for a linear pot in the circuit. Maybe I am just overthinking this, but I am aware of a method of simulating a log pot by attaching a resistor between the wiper and ground of a linear pot. (Rod Elliott explains the principle in his project one, see ESP - A Better Volume Control) Looking at the B1 schematic, I do not see such a resistor, but I am not sure that something equivalent might be in there. (And hence, the recommendation for the use of a linear pot.) If so, I could goof up the law of the pot by using inappropriate values for my resistors. The calculators are not designed to take that type of circuit into account. So my question really is, do I need to worry about this at all? If the circuit compensates for a linear pot, can I just use the calculations for a linear pot? If the circuit does not compensate for a linear pot, what is the rationale for not using a log pot?
Thanks for any input anyone can give me.
Jazzzman
do not worry about log or lin (stereo)pot.......
there are personal preferences (e.g. i always build in a lin pot, because its channel imbalance is lower than in a log one. but if there are res in parallel to the wiper, it will get some kind of "log shape" - if you want or not........)
there are personal preferences (e.g. i always build in a lin pot, because its channel imbalance is lower than in a log one. but if there are res in parallel to the wiper, it will get some kind of "log shape" - if you want or not........)
we have ears/brain that listen in a log fashion.
The vol pot needs to attenuate in a log fashion to make our hand/knob rotation match what we hear.
Linear gives good adjustment of sensitivity. Great for a PA amp that need a little bit od tweaking to match other equipment. Great for adjusting the treble level of an active filter set.
The vol pot needs to attenuate in a log fashion to make our hand/knob rotation match what we hear.
Linear gives good adjustment of sensitivity. Great for a PA amp that need a little bit od tweaking to match other equipment. Great for adjusting the treble level of an active filter set.
Thanks 6L6!
Thanks 6L6 for this excellent guide. I actually bought my B-1 board and JFETS over 5 years ago, and a nice Modushop chassis from Italy a couple years after that, but only got around to building it now. Your guide helped me overcome my fear/inertia. Actually the hardest part was drilling holes in that nice chassis. I splurged on some nice caps and wire and so on, but otherwise did a really standard build. It sounds terrific.
Now to put my Peter Daniels F5 and PSU boards to good use!
Thanks 6L6 for this excellent guide. I actually bought my B-1 board and JFETS over 5 years ago, and a nice Modushop chassis from Italy a couple years after that, but only got around to building it now. Your guide helped me overcome my fear/inertia. Actually the hardest part was drilling holes in that nice chassis. I splurged on some nice caps and wire and so on, but otherwise did a really standard build. It sounds terrific.
Now to put my Peter Daniels F5 and PSU boards to good use!
Attachments
Looks great! Congrats on completing such a nice project!!
Try to be more careful when soldering around those big expensive caps - we've all done it, so don't feel bad.
...Heck, the last time I did it I completely destroyed the cap... 🙁
Anyway, you'll love the F5. 🙂
Try to be more careful when soldering around those big expensive caps - we've all done it, so don't feel bad.
...Heck, the last time I did it I completely destroyed the cap... 🙁
Anyway, you'll love the F5. 🙂
Jazzzman, use a stepped ladder in the B1. Will crush the Alp pots or any other wiper type pot. I have the Alps, but now use a $20 stepped ladder from Hong Kong and it murders the Blue Alps pot. It's such a big difference I'll never go back to a standard pot again. Even if you spend $150-200 on a stepped pot, it's still worth it. It's like listening to two completely different units.
Lafish, I used the Mundorf Evo S/G/O caps in my B1 and it sounds great. Also built a version with V-Caps, Obbligatos and Duelunds and it's a monster. Unfortunately, I built the Duelund version for someone else. 🙁
At a fraction of the price the Duelund/V-Cap B1 beat out a few tube preamps, one costing $7000. Any way you build it, the B1 is a serious preamp.
Lafish, I used the Mundorf Evo S/G/O caps in my B1 and it sounds great. Also built a version with V-Caps, Obbligatos and Duelunds and it's a monster. Unfortunately, I built the Duelund version for someone else. 🙁
At a fraction of the price the Duelund/V-Cap B1 beat out a few tube preamps, one costing $7000. Any way you build it, the B1 is a serious preamp.
Seriously, anything will be better than a wiper type.
I recently picked one up at Analog Metric. Should be getting one in the mail soon.
Shipping from Hong Kong takes about 2 to 3 weeks. I'll post a pic.
24 Step Ladder-Type Potentiometer (Stereo)_Volume Control_Accessories Kit_Analog Metric - DIY Audio Kit
8audio.com had 25k pots but ran out.
Check ebay too.
Also if you're up for it make your own. PartsConnexion.com has switches.
Shunt types are a bit easier and less expensive but stepped ladders are better.
Btw- There's also khozmo, dact and goldpoint.
I recently picked one up at Analog Metric. Should be getting one in the mail soon.
Shipping from Hong Kong takes about 2 to 3 weeks. I'll post a pic.
24 Step Ladder-Type Potentiometer (Stereo)_Volume Control_Accessories Kit_Analog Metric - DIY Audio Kit
8audio.com had 25k pots but ran out.
Check ebay too.
Also if you're up for it make your own. PartsConnexion.com has switches.
Shunt types are a bit easier and less expensive but stepped ladders are better.
Btw- There's also khozmo, dact and goldpoint.