I hope it is. At least it measures -+18.9 VDC.
When I installed the ground post on P3 amp back panel I wondered if this should have been an isolated post so it only gets connection from the star ground. But I guess it does not matter as the BOM ground post is not meant to be isolated either.
When I installed the ground post on P3 amp back panel I wondered if this should have been an isolated post so it only gets connection from the star ground. But I guess it does not matter as the BOM ground post is not meant to be isolated either.
Well, I finally plugged in the A2 amps with the Maggie 1.7.
First off, it has more gain -as a system- than the Sissy and AN speakers. And, well, the Maggies have better top to down bass.
I did hear more hiss than with the other set up, but I did have the system playing a lot louder. I think at one point I had the Maggies playing louder than I've ever heard them. The dynamic range of the P3 really shines through. And the bass is truly solid.
I listened to Rachmaninoff.... piano concerto #2, Chesky. Earl Wild. The Royal Philharmonic.
Frampton Comes Alive, run of the mill LP
Waylon Jennings, Willie Nelson, The Outlaws Live, run of the mill LP
Suzanne Vega, run of the mill LP
Alan Parsons, I Robot, MoFi.
Red Knuckles and the Trail Blazers -bought it at one of their concerts in Boulder in '82
Dire Straits, Brothers At Arms, MoFi 45PRM.
Any how, by the time I was playing Frampton, I had the darn thing LOUD. No cowbell, but likely one of the best LOUD concerts from the 70s. With the Maggie Sound stage, the sound of the audience enveloped you (*).
So, I won't tell you about the bass, midrange, treble.. dynamics, low level, accuracy, etc, etc.... I was just having a hell of a good time.
And THAT is what matters, I guess.
Now, to figure out how to remove those amps without wrecking anything. I got the tools but I haven't used them for a while.
(*) I'm thinking of putting together a mono surround rear signal for my main system. I need to organize my records... couldn't find Old and in the Way.
First off, it has more gain -as a system- than the Sissy and AN speakers. And, well, the Maggies have better top to down bass.
I did hear more hiss than with the other set up, but I did have the system playing a lot louder. I think at one point I had the Maggies playing louder than I've ever heard them. The dynamic range of the P3 really shines through. And the bass is truly solid.
I listened to Rachmaninoff.... piano concerto #2, Chesky. Earl Wild. The Royal Philharmonic.
Frampton Comes Alive, run of the mill LP
Waylon Jennings, Willie Nelson, The Outlaws Live, run of the mill LP
Suzanne Vega, run of the mill LP
Alan Parsons, I Robot, MoFi.
Red Knuckles and the Trail Blazers -bought it at one of their concerts in Boulder in '82
Dire Straits, Brothers At Arms, MoFi 45PRM.
Any how, by the time I was playing Frampton, I had the darn thing LOUD. No cowbell, but likely one of the best LOUD concerts from the 70s. With the Maggie Sound stage, the sound of the audience enveloped you (*).
So, I won't tell you about the bass, midrange, treble.. dynamics, low level, accuracy, etc, etc.... I was just having a hell of a good time.
And THAT is what matters, I guess.
Now, to figure out how to remove those amps without wrecking anything. I got the tools but I haven't used them for a while.
(*) I'm thinking of putting together a mono surround rear signal for my main system. I need to organize my records... couldn't find Old and in the Way.
Last edited:
Sounds like a lot of fun, as Papa says, the happiest audio.....One thing that I really like about this forum, aside for how generous people are is that the equipment serves the music. Love the variety of music and depth of knowledge!
This is really getting me excited to start my build, received multiple goodies today, including @Gianluca's lovely chassis and Flux! 😁
This is really getting me excited to start my build, received multiple goodies today, including @Gianluca's lovely chassis and Flux! 😁
what's the noise of a 47k resistor at 300K, gained up by 60dB over a 20kHz bandwidth with RIAA correction? The "sssshhhh" is to be anticipated. It will be different when you connect an MC cartridge. Not noticeable when you play ABBA, or the Concerto for two vioins in d minor.
That's a good question.
There are two valid ways of looking at it...
1) It's always there, it is a large value resistor with lots of thermal noise, and as everything counts in phono, there are worse places to spend time and money, so go for it.
or
2) The noise of the cartridge itself will always swamp the loading resistors, so will you actually hear it?
I don't think there's a wrong answer, but I lean towards 1) myself... hence why the kit has a Dale in that position.
There are two valid ways of looking at it...
1) It's always there, it is a large value resistor with lots of thermal noise, and as everything counts in phono, there are worse places to spend time and money, so go for it.
or
2) The noise of the cartridge itself will always swamp the loading resistors, so will you actually hear it?
I don't think there's a wrong answer, but I lean towards 1) myself... hence why the kit has a Dale in that position.
I think the issue of background / thermal noise needs to take into account system gain. Will a high gain line stage and low gain power amp handle the noise better? Or the opposite?
When I run the P3 with CJ (high gain preamp) into the Sissy (relatively low gain) I hear less background noise than when I put in the A2s.
With the CJ and A2 I run the preamp volume about 10 steps lower than with the Sissy. I think this relates to an 8 db difference ( 0.8 db per step ).
So perhaps, it's better to implement the overall system gain lower and run it all closer to its gain limit? Otherwise you're throwing gain away and running the system in a noisier range?
The Charcroft Z-foil has these specifications.
As you write it is DIY and just fun so I ordered 2 x 47k of these.
The leg spacing is 5mm. PCB has probably a bit more spacing for the resistors.
I guess I can solve that. I hope the specs are a bit better than a standard metal film resistor. -+0.2 ppm/C looks low.
As you write it is DIY and just fun so I ordered 2 x 47k of these.
The leg spacing is 5mm. PCB has probably a bit more spacing for the resistors.
I guess I can solve that. I hope the specs are a bit better than a standard metal film resistor. -+0.2 ppm/C looks low.
The thermal noise in resistors is related strictly to the resistance value. Any 47 kΩ resistor will by definition produce the same thermal EMF noise as any other.
Where the bulk metal foil resistors offer an advantage is in other aspects of performance, one of those being what is called 'excess noise' - this refers to the sources of noise above and beyond the unavoidable thermal noise. Comparing bulk metal foil to wire wound to ordinary metal film resistors, this difference is primarily in what is called 'current noise', or excess noise generated by current flowing through the resistive material. As the name suggests, current noise increases as current increases. So in a phono cartridge loading application where both the AC and DC current and voltage imposed on the resistor are smaller than a flea fart, the bulk metal foil really has nothing to offer here.
The other main advantages of the bulk foil types are in temperature coefficient, voltage coefficient, and usually absolute precision. Here again, these advantages will not manifest in a phono cartridge loading application, since the resistor will only dissipate extremely low power levels and see extremely small voltages, and the cartridge response will be quite insensitive to the precise resistor value. 0.01% tolerance and ±5ppm TC will not help here.
So I would submit that an expensive Vishay bulk foil offers nothing in this case that you won't get from a Dale or other decent quality MF resistor. I would save those precious bulk foils for applications where the precision, stability, and low voltage coefficient can matter - positions which see significant DC current, large signal voltage swings, matching or precision balance sensitive situations, thermal drift sensitive circuits, etc.
On the other hand, it can do no harm, so by all means feel free to indulge if it suits your fancy.
Where the bulk metal foil resistors offer an advantage is in other aspects of performance, one of those being what is called 'excess noise' - this refers to the sources of noise above and beyond the unavoidable thermal noise. Comparing bulk metal foil to wire wound to ordinary metal film resistors, this difference is primarily in what is called 'current noise', or excess noise generated by current flowing through the resistive material. As the name suggests, current noise increases as current increases. So in a phono cartridge loading application where both the AC and DC current and voltage imposed on the resistor are smaller than a flea fart, the bulk metal foil really has nothing to offer here.
The other main advantages of the bulk foil types are in temperature coefficient, voltage coefficient, and usually absolute precision. Here again, these advantages will not manifest in a phono cartridge loading application, since the resistor will only dissipate extremely low power levels and see extremely small voltages, and the cartridge response will be quite insensitive to the precise resistor value. 0.01% tolerance and ±5ppm TC will not help here.
So I would submit that an expensive Vishay bulk foil offers nothing in this case that you won't get from a Dale or other decent quality MF resistor. I would save those precious bulk foils for applications where the precision, stability, and low voltage coefficient can matter - positions which see significant DC current, large signal voltage swings, matching or precision balance sensitive situations, thermal drift sensitive circuits, etc.
On the other hand, it can do no harm, so by all means feel free to indulge if it suits your fancy.
Hello,
You are speaking about the limits of vinyl playback.
The program will mask the "sssshhhh" and the "sssshhhh" will mask the delicate program material a bit.
Thanks DT
In terms of resistor caused distortion Carbon resistors are the worst and not far behind are the bulk foil resistors.
The bulk foil resistors have very low thermal mass, they heat and cool rapidly more than canceling their DC and HF low TC performance.
By my APx555 testing, Dale RN60 or CMF 25ppm resistors are among the best performers.
Try this one:
https://www.mouser.com/ProductDetail/Vishay-Dale/CMF6047K000BEBF?qs=A%2B/NCR0PvNUgR9U4flCE3A==
Thanks DT
Curiosity leads me to ask. What is the purpose of the R37/C23 selection on DIP switch position #8? I also not that the cartridge loadings are heavily weighted toward MC cartridges. I'm thinking that remapping the Dip switch values to get more selection between 8246 and 47K ohms might be advantageous to us MM cartridge owners...
You can so reduce the MM cartridge loading resistor so that the 75us compensation can take effect at the input stage. Cordell showed how to do this in his "VinylTrak" phono preamplifier. While this reduces the likelihood of overloading on "clicks and pops", it regrettably reduces the output voltage going into the first stage.
In his 1982 AA article describing a pre-preamp for moving coil cartridges, Richard Marsh argued for very low impedances comparable to the cartridge Z to lower distortion. A part of this was to increase electromotive damping to address groove rattling. His circuit used negative feedback to lower the impedance to a minimum of 0.5R (measured 0.68R).
R37/C23 - post #271
Regarding re-mapping DIPs for MM. To the best of my knowledge, most MM's are set up for 47k. What cartridge(s) are you using?
Hmmm. I was kidding Jack! It’s my tinnitus!
And if i play ABBA, there’s a different problem…
Many MM carts work at 47k, but optimal loading can vary from 22k to 100k.
Looking at the schematic -- and please correct me if I'm missing something -- I don't see why one couldn't substitute any useful R or C values for the DIP switch. Depends what carts you're going to run and how much cart rolling you expect to do.
Nice to have this option on the board. I just had my own boards fabbed for adding adjustable loading on some other phono stage projects.