The Phonoclone and VSPS PCB Help Desk

[waltroman]

I am having a hard time finding a .25 amp slow-blow fuse to fit a Cooper Bussman holder. It takes 1 1/4 X 1/4 or 6.3mm X 32mm fuses. I am in the states so need 125 volt rated. Can find plenty of 250v rated fuses in this size and I am wondering if 125 volt power I should use .5 Amp slow-blow? I need to buy a holder and fuses for my VSPS power supply so I am open to suggestions, would like to stick to Mouser to save on shipping.

[troystg]

You can use a higher VOLTAGE rating with no issue, just keep the SAME current rating.

[Bibio]

good evening.

i would like to as a few questions if that's ok.

i'm planning on buying a Denon DL103r as my new cart and i have read a good part of your threads regarding the phonoclone being designed to run with the Denon and i have come to a decision that i would like to build one. i'm also after a headphone amp till funds permit me to build some power amps at a later date.

my questions:

can the phonoclone and the headphone amp (sapphire) be powered from the same power supply?

would it be possible to add to the headphone amp to give it function as a pre-amp so come the time i can use it to feed the power amps?

you touch on the fact that the B-board could be used as a headphone amp, is this the case?

is there a way to make the headphone amp specific as regards the ratings of my headphones which are beyerdynamic 770 pro 80ohm?

i'm handy with a soldering iron but i know nothing about electronics so is there a complete 'build it for dummies' tutorial on how to build and test and what tools are required for testing?

i know that's a lot of questions but i'm keen on building my own gear :-)

[rjm]

In order of appearance,

Yes. Yes. Not really. Yes. and No.

You should be able to share the power supply.
Any headphone can double as a preamp without modification.
The B-board is of limited use as a headphone amp, since it has unity gain.
No special modifications are needed for 80 ohm 96 dB headphones, that's a "generic" spec.
The kits come with instructions but a basic level of familiarity with electronics and electronics is assumed.

[waltroman]

Got my VSPS 300 kit today. Nice looking boards. Should have everything to complete in the next few days. I need some standoffs and going to get a different on/off switch but Radio Shack has those items. Can't wait. Thanks Richard for the fast service!

Walt Roman

[waltroman]

Getting close to completion. It has taken me a lot longer than I expected but that is normal for me. I checked every resistor twice before populating the boards and triple checked every solder joint as I cleaned the joints with alcohol. I did find one joint that did not receive solder the last check. I guess being a little anal pays off. Other than speakers and crossovers this is my first piece of solid state electronic gear.

[waltroman]

My VSPS is up and running. After a minor mishap, wired right channel output at the board out of phase, it is settling down nicely after a few hours of play. The sense of depth is very good and bottom end is filling out. I am not missing any detail but seem a little too smooth but I think that is due to my output caps the Obbligato Gold, they will probably take some time to open up. Right now I am feeding it with a tuner through a reverse RIAA attenuator box to give is some on time for a few days.

Other than the output caps the only other change I made to the board is to increase gain to 48-50 DB.I believe R3 is 2.7k and R2 is 330 ohm if I have that order right. I am getting some NOISE that may be power line noise with the signal turned up. I have the power supply case grounded to the line neutral on a shielded power cable but did not connect the shield of the cable to the PS case. I have 3 wires out to the preamp box: ++, --, and the common. The ground for the turntable is connected to the ground connector of both boards and the case itself. The RCA plugs were not grouded to the case and are floating. Before I installed the final op amp both boards were reading identical or within a few tenths of a volt on the suggested + and - pin outs following the suggested checks before install IC1 in their sockets. I may be getting stray EMF from the tube preamp on the shelf below and I can get some change moving the position of the preamp and VSPS but doesn't eliminate the noise. I can say that it is not noticeable with music playing. I did use a power switch with a led in it and wonder if that could be it? Could swapping the position of the wires that feed the diode bridges ( the two wires from the transformer secondaries ) make any difference?

[waltroman]

I believe I got it. I think I created a ground loop at the switch. The switch has three tabs: power in, power out and neutral. Instead of neutral I connected the house wiring ground to the neutral tab and jumped after it to ground the chassis with the neutral connection, more 2am foggy logic I will fix it in the AM and report back.

[waltroman]

I have what appears to be 120HZ noise I cannot get rid of. Should the metal cases of the diode bridges be grounded to the PS? Lifting the ground and reversinf polarity do not affect the noise. Using a Avel Lindberg 250VAC toroid with 25 amp bridges. Shielded power cable to the PS and same to the VSPS but the shield is not connected to ground. Moving the VSPS in reference to other components did not make a difference. Tried adding ferrite cores to power lines with no result. Everything is plugged into a low budget home theater surge suppressor that is new but no effect on CD player or tuner. Tried removing the VSPS PS and plugging it into the wall to no effect. Any suggestions?

[mavallarino]

Sorry if this has already been asked/tried; have you grounded the signal inputs?