[JayB]

I apologize if these questions have been asked before.

1. I am buying parts for my Piccolo, and have decided on PRP resisters. I've checked with Parts Connexion and Sonicraft and not all values are available. I know that others have used them in their preamps so where did you get them? Did you settle on values that were close but not exact?

 2. Has anyone tried using a pot for setting input resistance? Soundsmith has a MC pre that uses this method. Of course, it would probably need to be of good quality. At least you could use it to find the best resistance value, and then insert that value resister into the circuit.

[BobM]

I went with Dale/Vishay's when I built mine. If you're going for boutique resistors there are probably only a few that are critical to the circuit. The PRP's should be fine though.

I know there's a lot of talk about the variable resistance. The bottom line, yes it makes a difference, but setting your VTA correctly makes more of a difference. I find that anything close to what the cartridge wants is close enough. Don't go crazy with it.

[Bill Epstein]

Try Handmade for PRPs.

http://www.hndme.com/productcart/pc/viewCat.asp

[Brinkman]

For R10 (232 ohm) the closest value in PRP land is 220 ohm. In this case, I paralleled two 470 ohm PRPs and got real close to the spec'd value. For all the other instances the closest PRP values are within 1% of the spec'd value, and that's nothing to worry about.

[JayB]

Thanks All. BobM, which circuit board positions do you consider critical?

[BobM]

If you look at the manual on the hagtech website you'll see any resistor in line with the inputs and output jacks are playing a critical role. So certainly R3 and R10 at a minimum, but probably also the others in the area if you're looking to maximize things.

[BobM]

I tried some rather special resistors in these key spots on my Hagerman Piccolo step up. I built the whole board with Dale/Vishay bulk metal foil's However I had some generic Digikey metal foils laying around for some values so I used those in a few places where I could.

One place I used those happened to be in a fairly key location, where it was directly in the signal path. The sound was a little hard and edgy to my ears so I began looking a little deeper. There are actually 2 resistors directly in the signal path that could be upgraded.

I got some Vishay nude resistors for both spots and replaced them. The sound immediately opened up a little more and that metallic "ting" was gone. Very nice improvement, but still not completely musical. So I also ordered a pair of Riken Ohms from Partsconnexion for one of the locations. I've read that these can add a touch of warmth and bloom to the sound if used judiciously. If over used things can get muddy.

So I kept the nude Vishay in the first position and replaced the second with the Riken. After about 4 sides of vinyl the initial haze burnt off and there was bloom and warmth and extension and musicality again. However, I can see why you would not want to use Riken's everywhere (aside from cost).

So yes, I do believe that resistors can have a sound and can be used to tune a system and that it is worthwhile to look over a circuit and put in higher quality parts in key locations.

I've also heard similar results using those Caddock white paddle-like resistors in a signal path. Very open, musical and involving.

Enjoy,
Bob

[Bernie]

I think it will be tough to go wrong with using DALE/VISHAY or RIKEN OHM resistors in place of those few that you can't get in the prp brand.

Bernie.

[miter53]

Another good source is http://www.soniccraft.com/prp_resistors.htm. Good outfit and very helpful.

[jameshuls]

Bob, some good advice regarding the critical resistors and your findings. I will have to incorporate your suggestions into some modifications of my piccolo when it comes time. I notice partsconnexion is now selling the TI Z series nude foil resistors (available at the end of March). Suposedly these are the best of the best, as they should be at $16 a piece

I know there's a lot of talk about the variable resistance. The bottom line, yes it makes a difference, but setting your VTA correctly makes more of a difference. I find that anything close to what the cartridge wants is close enough. Don't go crazy with it.

Regarding this statement, I think this is highly dependent on what type of cartridge you are using. For example, on my Dynavector Karat 17D3 with its vey short diamond cantilever, I found that VTA had a moderate affect in my system (VPI Scout with Signature arm, Melody H2AS, modified Zu Druid MKIVs), whereas loading had a profound effect on the sound. I found that the loading intervals were spaced too far apart and so into the shop it went for a modification of resistor loading values... where it remains, as I am currently using a Cartridge Man Music Maker III, a MM cartridge, while my Karat is being repaired at SoundSmith (thanks to a careless housekeeper).

As for what floats the boat for resistors in the piccolo, I think there were good suggestions by the previous folks. However, IME, build it up and listen to it with your cartridge for awhile until you settle on the two values, high and low, which seem to work the best for the cartridge (and you!), Then, replace the loading resistors with a range encompassing those highs and lows to fine tune the ideal loading. At this time you could use really high end resistors... or you could wait until you find your favourite value and replace that with some really high end resistors like the TI nude foil Z series. This might be a better strategy as you can maximize your $$$. This method also allows for a progression of understanding regarding the subtle changes you are making. If you step too big too fast in DIY it is easy to lose your way. I have found that progressive steps leads to a better understanding of what changes matter most to your idea of musical perfection in each component. This knowledge will (hopefully) eventually lead to a musical system tailored to your tastes without spending a fortune. See Tubesforever's posts,as he has really put this philosophy in action.

[tubesforever]

I've been entirely satisfied with the sonic results using PRP resistors in my Piccolo.  I used Holco's for the 232 resistor values.   You have to double check the resistance of the PRP's, several were way off value and had to be replaced.

I am an amateur musician, so I am very picky about the sonics of guitars, pianos, and percussion.

The PRP's really are a great resistor.   I might try nude vishays in the direct signal pathway down the road in the future, but I am not missing any detail or hearing any trace of hiss which basically says the resistors are not being thermally stressed. 

I am using Dynamicaps for the film caps and Russian FT-2 0.10 uf for the final signal coupling caps. 

The sonics are actually quieter than my SUT and there is less sibilance with vocalists which is a big plus for me. 

I am using Black Gate electrolytic caps for mine and their -160db noise floor probably accounts for the low noise results I have achieved.

Cheers!

[BobM]

One thing I am noticing. Since I replaced these resistors I'm getting a hum out of my Piccolo. If I touch it with my hand the hum diminishes. I tried running a ground wire from the lug to another ground on my phono stage, but the hum got louder. I tried relocating the Piccolo away from everything else but that did nothing. It's definitely being generated by the Piccolo and it gets louder as I increase the gain (obviously) and also as I move the loading from low numbers to high numbers.

Any thoughts?

[tubesforever]

Bob, has anything changed in your system?

When I record LP to CDR I often times hear a 60 hz hum in the recordings even though I cannot hear the hum from my listening seat.  Luckily its way way down in the noise floor so it does not impact the recordings, its just annoying on the cdrs.

When I kick off my Bedini amps, I am eliminating 3 transformers within a few feet of my Piccolo and the recordings are much quieter. 

I was thinking of building a Mu Metal enclosure for the Piccolo just to see if it responds to a lower EMI but then perhaps the EMI is getting in through the power cord or the IC's? 

Hey Bob, did you check to make sure you have a good solder connection?  When replacing components on my boards I generally run my iron just a little hotter and leave the contact on just a little longer to make sure I get a good solder joint on both traces on the double PCB boards.   

One last thing, why not try both nude Vishays again and give them just a little time to break in.  They are not dry or analytical in my system.  They are just refreshingly abscent of noise and distortion.

I would rather tune the warmth with different tubes in my Clarinet and C2. 

[BobM]

The Piccolo was very quiet before I put in the nude Vishays. I have a feeling these are the culprit. I'm using one set in the 22 ohm spot (R3) and a second in the 220 ohm loading position. I'm using the Riken in the 220 ohm spot (R10).

The soldering should be OK, but I do have more "leg" showing  on these than I would like. I may have to take them out and see if I can get them closer and tighter to the board.

[tubesforever]

Bob the nudes should not be an issue.  I have 14 of them on my Cornet 2 and have no hum issues.  I have 8 on my Clarinet with no hum issues. 

I have the nudes mounted tall on the board with as much leg as possible.  That's because I hear you can damage them soldering them up.  With a taller leg I could use a heat sink.

I asked if anything has changed in your system because sometimes you need to find different grounding schemes to get things quiet after you make a change here or there.


Good luck, with enough time and resources this will all work out.   

One final question Bob, are you running shielded IC's for the phono input and line out of the Piccolo? 

I shield these wires to make sure I am not running down the wrong road when it comes to hum.

Let us know what works when you get it all settled out.

Jim

[BobM]

Yeah, the wires are shielded. I will touch up the solder connections again just to be sure. Hum is just like looking for a water leak - sometimes you just get lucky finding the true source of the problem, and sometimes you don't.

[BobM]

Gave more of a listen last night, but unfortunately I dodn't have time to check solder connections and such. I'm not exactly getting hum. It's more like a throbbing motor noise, so I'm guessing I'm picking it up from somewhere and it's not originating in the Piccolo since there's nothing to throb in there.

But moving the Piccolo didn't seem to resolve it. Maybe I'll move my speed controller to another shelf and see how that works out. There are transformers and a motor chip in there (to step up the 12V DC power supply into AC for the TT motor) that could certainly be causing a throb. Right now I have it placed between the Piccolo and my Trumpet (it could actually be the Trumpet picking up the noise, come to think of it, but it didn't do that before I got my Piccolo).

More experimentation is necessary. I hate hums - they're as hard to resolve as a water leak somewhere in the house.

[poty]

But why do not disconnect everything from the Piccolo's input and do the short of the input? If the noise disappears - then it could be external cause or loading resistors. If it is not - then there is something bad inside (or after the Piccolo).
The trumpet has less sensitivity than Piccolo, so it may be less vulnerable to noise.

[BobM]

Good idea, thanks.

[BobM]

Solved it. It was a motor noise issue from my speed controller. I've always had this betwen the Piccolo and Trumpet and never noticed a problem before I put in the new resistors. So I relocated the motor conroller and it got better but it was still there a bit. I had to plug this into a separateoutlet from the Trumpet (actually on an isolated balanced transformer isolated circuit right now) to totally remove its influence on the rest of the system. So it wasn't totally resistor sensitivity, it was going through the AC line too.

Now the background is as quiet as tubes get (i.e. a little tube rush) and th sound is wonderful. Crisp and clear and musical.

Thanks guys.