Sorry that no one answered that. The input impedance is about 100k Ohms and is set primarily by R13. You can see that in the schematic. As I recall, this was originally chosen in the original MyRef and carried over since then. Perhaps others can comment on if this is critical or not.
Jac
It is not critical.
It becomes of importance when the interconnect is disconnected at one end.
Otherwise it does little, other than help to define the high pass passive filter that should be added to every input.
It becomes of importance when the interconnect is disconnected at one end.
Otherwise it does little, other than help to define the high pass passive filter that should be added to every input.
I have an AMPROBE AM-270 (about $80), I think on the suggestion of Soil4x4. I haven't checked the Brymen specs to compare it yet, but I found the AM-270 to have pretty good specs for the price. I like it a lot, although I will admit I don't have complete confidence in the capacitor measurements at the small end of its measurement range. I also have an old dedicated capacitor measurement tool. When measuring a 50 pF capacitor, the cap tool was very close to the 50 pF spec and the AM-270 wandered a bit and was farther from the spec.
Everything else seems great.
As for the Uni T model 61, lots of guys do fine with a $30 multimeter, so the Uni T is probably fine.
I think Bob has an inexpensive one that he likes a lot and Dario has a different, inexpensive choice.
Jac
Actually Amprobe is really reasonable multimeter.
It is on my list I just did not read into it.
Thank you
It is on my list I just did not read into it.
Thank you
I added this meter a couple months ago. Madisonears suggested I get something with LC functions for use in speaker crossover tweaking. I have all the parts to upgrade the Sunflower Redux but not the time as yet. It has been accurate, stable and outperforms my $90 Ryobi. Unless you plan to dig in really deep, I agree some of the $15 - $30 units are fine for general MyRef construction.
I purchased from Amazon for $42 plus $6 shipping. It appears to be out of stock everywhere and I'm not sure if it is still being made. That company has several similar models in the price range.
Sonimeter
Remember - I'll be happy to purchase and ship U.S. items via USPS "If It Fits - It Ships" boxes. Shipping is generally ~ $4-$7 and takes about 5 to 10 days. (England)
I purchased from Amazon for $42 plus $6 shipping. It appears to be out of stock everywhere and I'm not sure if it is still being made. That company has several similar models in the price range.
Sonimeter
Remember - I'll be happy to purchase and ship U.S. items via USPS "If It Fits - It Ships" boxes. Shipping is generally ~ $4-$7 and takes about 5 to 10 days. (England)
I'm not pushing or promoting - but I thought that might be a problem also. This one has a very sensitive scale reader that shows a giant "OL" and it's easy to bump the dial up or down.
Like some other devices, the manual approach can be beneficial to those of us with incipient arthritis - have to keep those fingers moving and nimble.
😀
Like some other devices, the manual approach can be beneficial to those of us with incipient arthritis - have to keep those fingers moving and nimble.
😀
🙂 I ll take my time to choose something better.
Don't want to pay twice, you know.
Good meter, good tools in general better than cheap.
Plus FE is not only one thing I am planning to build...
I had a look even on the diy synths to power up to my ableton 😀
Don't want to pay twice, you know.
Good meter, good tools in general better than cheap.
Plus FE is not only one thing I am planning to build...
I had a look even on the diy synths to power up to my ableton 😀
Is any of this audible? Regardless of which cap goes where, they are all in parallel and the signal will travel the same distance regardless of whether it's in a capacitor lead or a PCB trace, high or low frequency. There is no "shorter route" if they all start and end up at the same place in the circuit. Seems like you're brewing a tempest in a teapot here. Capacitor characteristics will surely swamp the extremely minute difference of inductance, if, in fact, there is any. It is certainly worthwhile to keep all paths as short as practical, but drilling extra holes in a PCB trace is unnecessarily fussy and possibly damaging. I can't imagine much worse advice for someone building their first (or fifth, for that matter) amp, especially on boards as beautiful as these.
MUST this and MUST that. Is any of this really mandatory to get the amp to work?
How about this instead: MUST solder both ends of all components! I'm sure all of us have tried a circuit after missing one lead/pad. The best that can happen is nothing, as in no smoke or frightening noise. I ran a MyRef with one end of C7 unsoldered for several months until it finally got bumped and became intermittent.
Peace,
Tom E
Thanks for the reply Jac.I have been thinking that as I have four of the pcb's that bi-amping might be worth considering and wanted to make sure that my pre would be capable of driving two amps.Looks like it should be ok.
I agree with you and am planning some bi-amping myself in the future. I've seen amps as low as 10k and a lot around 50k, so this somewhat high 100k is probably to our benefit.
Enjoy.
Jac
If you find something that you want to buy that is offered in the US and not in Europe, either Bob (post #1146) or I would be happy to buy it for you here and send it to you. Bob describes the details and typical cost. Think of it as fair play for the mini-group buy where Dario saved us US guys a lot on shipping capacitors.
Jac
Seem a very good one but I would consider the VC 97 that can be found on ebay from various sellers, one example that shipis from UK, it's a bit less precise but it cost much less.
It's the one I'm using and it works well.
I'm no expert, just an interested user like you. Overall, the 37XR-A looks very good. The only concern is that the resistance ranges are very high. The lowest range appears to be 1000 Ohms with a resolution of 5 Ohms + digit error. You will probably want to measure smaller resistances than that. However, if you have another good resistance measuring tool, then the combination might be great.
Note that this is similar to my AM-270 for capacitance measurement. With a lowest range of 40 nF and a resolution of about 1 nF, you will find yourself looking to measure pF caps and having trouble.
It is nice that it has logic and inductance. Very cool.
I notice on the data sheet (under resources on the Amprobe page) that they have an office in Germany, so there may be hope of finding one in the EU.
Jac
There you go. Buy the VC97 and an LC meter (below) for less than the Amprobe. That would get you down to 30 pF with accuracy.
3 1/2 LCD Inductor/Capacitor LC Meter 2nF-200uF/2mH-20H | eBay
OT Alert !!
Tom, I only had time to listen to "Galaxy of Emptiness" once and didn't get the full effect as you described. However, today I called up the Carver Sonic Holography memory (close your eyes and wait for your ears to adjust) and had much better results. I believe you refer to the mid/low drones and the vocal echos. They can be missed easily as particularly the voice moves a lot from front to side and back to front. Haven't heard much from behind yet but I'm sure moving some things in the room would change that. I have open back mids and side baffles for early reflection reduction which also have an effect. None the less - an interesting track to play with.
Still planning to do some heavy room arrangement tests when this amp building phase is complete.
For those who might be interested, here is a link to the C-1 user doc that has more information than you ever wanted to know about what I believe Beth Orton's recording dudes were after.
The Sonic Hologram Generator. (Pg. 16)
Tom, I only had time to listen to "Galaxy of Emptiness" once and didn't get the full effect as you described. However, today I called up the Carver Sonic Holography memory (close your eyes and wait for your ears to adjust) and had much better results. I believe you refer to the mid/low drones and the vocal echos. They can be missed easily as particularly the voice moves a lot from front to side and back to front. Haven't heard much from behind yet but I'm sure moving some things in the room would change that. I have open back mids and side baffles for early reflection reduction which also have an effect. None the less - an interesting track to play with.
Still planning to do some heavy room arrangement tests when this amp building phase is complete.
For those who might be interested, here is a link to the C-1 user doc that has more information than you ever wanted to know about what I believe Beth Orton's recording dudes were after.
The Sonic Hologram Generator. (Pg. 16)
Oh my...
I been looking into the supply half a day.
1. So many people dismiss vc97 so I aimed at least to get uni t 61e. But Dario's words change it again,as I do beleive you, man 😀
2. Amprobe- 37 datasheet is next to 270 version datasheet on my desk and I am concerned about low value measurements...So as Bob noticed- it is a problem.(I have found inexpensive seller here though).
So question is- buy cheap or buy fluke. It is always nice to have good equipment which is precise and of good quality. But probably such precision is not required..
Will get VC97 and separate capacitance meter.
Thanks again.
BTW boards really nice, Dario.
0805... my colleague asked how would I solder this small bit. I told him to look inside the actual container for resistors 😀
I been looking into the supply half a day.
1. So many people dismiss vc97 so I aimed at least to get uni t 61e. But Dario's words change it again,as I do beleive you, man 😀
2. Amprobe- 37 datasheet is next to 270 version datasheet on my desk and I am concerned about low value measurements...So as Bob noticed- it is a problem.(I have found inexpensive seller here though).
So question is- buy cheap or buy fluke. It is always nice to have good equipment which is precise and of good quality. But probably such precision is not required..
Will get VC97 and separate capacitance meter.
Thanks again.
BTW boards really nice, Dario.
0805... my colleague asked how would I solder this small bit. I told him to look inside the actual container for resistors 😀
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