One question:
What is the minimum transformer VA recommended for the VSPS and the phonoclone?
-steve
What is the minimum transformer VA recommended for the VSPS and the phonoclone?
-steve
A tough question but one I've been asked often enough to be able to fudge an answer:
Technically anything above even 5 VA will be sufficient to get the job done, but 50 VA is a good "sweet spot" : decent price, relatively compact, and commonly available - while still packing a reasonable punch. I use a 160 VA toroid, but mainly only as I prefer to be able to interchange my power supplies between gainlclone and preamp circuits, and the Plitron model is conveniently supplied with electrostatic screen and magnetic shield. Or at least that's the excuse. Truth is even 160 VA is not necessarily overkill.
So, minimum recommended is 35 VA. Bigger is generally better, but quality counts, too.
-rjm
Technically anything above even 5 VA will be sufficient to get the job done, but 50 VA is a good "sweet spot" : decent price, relatively compact, and commonly available - while still packing a reasonable punch. I use a 160 VA toroid, but mainly only as I prefer to be able to interchange my power supplies between gainlclone and preamp circuits, and the Plitron model is conveniently supplied with electrostatic screen and magnetic shield. Or at least that's the excuse. Truth is even 160 VA is not necessarily overkill.
So, minimum recommended is 35 VA. Bigger is generally better, but quality counts, too.
-rjm
Project completed but RFI problems...
Hello,
in the attached pictures you can see my phonoclone prototype.
My choice of components is almost compliant to the most common audiophile obsessions (1W metal film resistors, Elna Cerafine for power supply decoupling, polystyrene caps for RIAA, Blackgate N as output cap), and I have fitted the boards to a small aluminium enclosure. Power is +/- 18 V from an external source that I already had (choke filtered LM317 circuit).
After testing the psu, I mounted the opamps and connected the thing... OUCH! I got a serious problem with RFI (I can hear voices coming from the loudspeakers if I listen close to them) and some hiss from the tweeters.
However, I could not resist to put some records and, despite this noise, I liked a lot what I heard (very dynamic and detailed sound).
Any suggestions to fix the RFI? I followed the gounding scheme proposed by Richard and the circuit is grounded to the metal case.
p.s. I would like to thanks Richard for having shared this project
Hello,
in the attached pictures you can see my phonoclone prototype.
My choice of components is almost compliant to the most common audiophile obsessions (1W metal film resistors, Elna Cerafine for power supply decoupling, polystyrene caps for RIAA, Blackgate N as output cap), and I have fitted the boards to a small aluminium enclosure. Power is +/- 18 V from an external source that I already had (choke filtered LM317 circuit).
After testing the psu, I mounted the opamps and connected the thing... OUCH! I got a serious problem with RFI (I can hear voices coming from the loudspeakers if I listen close to them) and some hiss from the tweeters.
However, I could not resist to put some records and, despite this noise, I liked a lot what I heard (very dynamic and detailed sound).
Any suggestions to fix the RFI? I followed the gounding scheme proposed by Richard and the circuit is grounded to the metal case.
p.s. I would like to thanks Richard for having shared this project
Attachments
The RFI is most likely picked up from one of the cables, either the phono interconnect or power supply umbilical. I guess my approach would be to first unplug the phono interconnect from the Phonoclone input, and/or make sure the noise isn't present with the unit connected but powered off.
Try also connecting the phono amp chassis to earth. After that its a game of disconnecting or rearranging things until the problem goes away.
Twisting the lead wire might help, though in a shielded case as you have it that shouldn't matter...
A photo of your power supply arrangement might be informative.
-rjm
Try also connecting the phono amp chassis to earth. After that its a game of disconnecting or rearranging things until the problem goes away.
Twisting the lead wire might help, though in a shielded case as you have it that shouldn't matter...
A photo of your power supply arrangement might be informative.
-rjm
rjm said:
Hi Richard, I have already tried both things you suggest with no success. However, I just replaced the my old phono (SUPA Phono by Hormann Audio) with the clone. The SUPA was very quiet using the same cables and power supply. This would suggest that the problem may be in the case (but a similar aluminium case is used in the supa) or somehow in the circuit itself...
I will try...
Richard, it is just an external box connected by a shielded 3 conductors cable. I can provide a picture later.
Few months ago I had a similar RFI problem with a Gainclone: in that case, as suggested in the LM3875 datasheet, I added a small cap (200 pF or so) between the inverting and non inverting inputs of the opamp and this solved the problem. I was wondering whether this could be appropriate for the Phonoclone...
carlo
The Phonoclone isn't especially sensitive to RFI - the circuit bandwidth is only 200 kHz or so - but then I would have said the same thing about the Gainclone, too. Unlike many commercial designs, the Phonoclone has no inbuilt anti-RFI measures of any kind. Its up to you to add whatever might be needed in this regard.
I'd definitely give that trick with the 200pF cap over the inputs a try. Perhaps some ferrite beads near the input and/or outputs might help.
Richard
(I'm still pondering on how you can get RFI with the inputs disconnected and everything shielded in a circuit with such low bandwidth. Parasitic inductance? I'm no expert here so its a llittle beyond me...)
I'd definitely give that trick with the 200pF cap over the inputs a try. Perhaps some ferrite beads near the input and/or outputs might help.
Richard
(I'm still pondering on how you can get RFI with the inputs disconnected and everything shielded in a circuit with such low bandwidth. Parasitic inductance? I'm no expert here so its a llittle beyond me...)
This might help, its a bit over-simplified but...
http://internet.aca.gov.au/ACAINTER.65650:STANDARD:1183193359:pc=PC_1264
"SOME METHODS FOR ELIMINATING CITIZENS BAND RADIO TRANSMISSIONS FROM YOUR HI-FI STEREO OR AUDIO EQUIPMENT"
You'll have to copy-paste the URL. I couldn't link it.
-R
http://internet.aca.gov.au/ACAINTER.65650:STANDARD:1183193359:pc=PC_1264
"SOME METHODS FOR ELIMINATING CITIZENS BAND RADIO TRANSMISSIONS FROM YOUR HI-FI STEREO OR AUDIO EQUIPMENT"
You'll have to copy-paste the URL. I couldn't link it.
-R
RFI problem solved
Hi,
the RFI problem is gone with the addition of a 220 pF capacitor between the inputs of the first opamp (terminals 2 and 3).
This seems also not having degraded the sound which is still very open, dynamic and detailed (and I still have to wait finishing the break in).
I wish good luck to the other builders of the phonoclone, this project is really good!
Carlo
Hi,
the RFI problem is gone with the addition of a 220 pF capacitor between the inputs of the first opamp (terminals 2 and 3).
This seems also not having degraded the sound which is still very open, dynamic and detailed (and I still have to wait finishing the break in).
I wish good luck to the other builders of the phonoclone, this project is really good!
Carlo
Ive just completed mine and Im very pleased indeed. However I do have a couple of question;
Using the phono pre on my valve amp (uses a simple passive pre) I have to really turn the volume up. Ive set the gain to the standard 40dB. Will changing this to 50dB via R2 & 3 solve this without causing any other probs? My other question is relating to the cartridge itself. At the mo Im just using a cheap AT95 but Im looking at a new cartridge. Most are recommending the Denon DL110 or 160. These give an output of 1.5mV, how Im I best adapting the phono pre to suit?
Using the phono pre on my valve amp (uses a simple passive pre) I have to really turn the volume up. Ive set the gain to the standard 40dB. Will changing this to 50dB via R2 & 3 solve this without causing any other probs? My other question is relating to the cartridge itself. At the mo Im just using a cheap AT95 but Im looking at a new cartridge. Most are recommending the Denon DL110 or 160. These give an output of 1.5mV, how Im I best adapting the phono pre to suit?
stueyh:
The VSPS, like most phono stages, doesn't have as large an output as a typical CD player. So the volume level will have to be set a little higher to get the same loudness.
If for whatever reason the compensation is unacceptibly large (I'd say more than a quarter turn) then the gain of the VSPS can be increased up to 50dB as you point out. Technically noise and distortion increase somewhat, and bandwidth decreases... but I've gone as high as 55dB and not noticed any audible degradation in sound.
Whether that will be sufficient with the lower output level Denon DL110 depends on your amplifier and speaker sensitivity. I would suggest it should be OK, but as I said at the beginning please understand that you shouldn't expect the volume level to be the same as if/when you listen to CDs.
btw: The Phonoclone, on the other hand, is a bit of a rarity in that it easily produces a 2V line-level output with even the lowest output moving coil.
cjunk:
Happy to hear you fixed the RFI problem. You asked me by email how quiet my Phonoclone was. I would say average to quiet. You should expect about 20dB higher noise floor than the amplifier by itself, just because of the high sensitivity. At normal listening levels I can hear no noise for the speakers. With the volume all the way up there is audible hiss and fustle, but no hum whatsoever.. and no local radio stations! 🙂
I tried to point out in the building pages that the circuit common (COM) connects to the phonoclone chassis (and the turntable) but is NOT connected to the power supply chassis which is earthed. Disconnecting COM from the power supply case might help the RFI somewhat.
-Richard
The VSPS, like most phono stages, doesn't have as large an output as a typical CD player. So the volume level will have to be set a little higher to get the same loudness.
If for whatever reason the compensation is unacceptibly large (I'd say more than a quarter turn) then the gain of the VSPS can be increased up to 50dB as you point out. Technically noise and distortion increase somewhat, and bandwidth decreases... but I've gone as high as 55dB and not noticed any audible degradation in sound.
Whether that will be sufficient with the lower output level Denon DL110 depends on your amplifier and speaker sensitivity. I would suggest it should be OK, but as I said at the beginning please understand that you shouldn't expect the volume level to be the same as if/when you listen to CDs.
btw: The Phonoclone, on the other hand, is a bit of a rarity in that it easily produces a 2V line-level output with even the lowest output moving coil.
cjunk:
Happy to hear you fixed the RFI problem. You asked me by email how quiet my Phonoclone was. I would say average to quiet. You should expect about 20dB higher noise floor than the amplifier by itself, just because of the high sensitivity. At normal listening levels I can hear no noise for the speakers. With the volume all the way up there is audible hiss and fustle, but no hum whatsoever.. and no local radio stations! 🙂
I tried to point out in the building pages that the circuit common (COM) connects to the phonoclone chassis (and the turntable) but is NOT connected to the power supply chassis which is earthed. Disconnecting COM from the power supply case might help the RFI somewhat.
-Richard
to stueyh :
pics please!
Actually to anyone who is building either the Phonoclone or VSPS, you are most welcome to send photos of complete or in-progress projects to me by email. My yahoo account can accept full-res pictures with ease, up to 10 Mb per email, so don't be shy! 😀
-rjm
pics please!
Actually to anyone who is building either the Phonoclone or VSPS, you are most welcome to send photos of complete or in-progress projects to me by email. My yahoo account can accept full-res pictures with ease, up to 10 Mb per email, so don't be shy! 😀
-rjm
Could I ask folks what they are using for C4-C7? I'm trying to decide what to go with. I have some Panasonic FC's at 220uF that I was going to use for C8-C11. I'm just looking for some good starting suggestions I guess? I can always upgrade down the road 🙂
Naz
Naz
Naz, I will use Wima FKP2's as RJM suggested. I might try some other types later on. I used FKP3 in the P2P VSPS I made earlier, and they sounded pretty good.
Steen.
naz was asking about C4-7, the bypass or decoupling capacitors placed on the output of the regulator. This is probably the part with the widest possible variation, as you could go with nothing at all (the regulator and op-amp are so close that even the datasheet 0.1 uF isn't needed) up to, well, I've seen people put up to triple bypass 2200uF+0.1uF+0.001uF in similar situations.
I went with a 100uF electrolytic on the basis that I didn't want to use a (possibly inductive) film cap, and I didn't want to use a big, slow electrolytic. 100uF has a reasonably low impedance over the frequencies of interest in this circuit. (And I could use the same cap for the input and output, a plus.)
Some brave person might want to substitute a tantalum cap, perhaps 4.7 or 10 uF in this position. Or, for amusement, try it first with no bypass caps and then add an electrolytic in the 47-220 uF range, see what if any difference it makes.
In terms of brands you either go with a generic model, a low impedance model, or a audio model. There probably isn't much difference between brands within those three classes. While I favor low impedance types, 47 labs probably uses generic parts.
naz: I'd use those 220uF FC's for all C4-C11 and not give it much further thought until I was ready to really play around with it later.
-R
I went with a 100uF electrolytic on the basis that I didn't want to use a (possibly inductive) film cap, and I didn't want to use a big, slow electrolytic. 100uF has a reasonably low impedance over the frequencies of interest in this circuit. (And I could use the same cap for the input and output, a plus.)
Some brave person might want to substitute a tantalum cap, perhaps 4.7 or 10 uF in this position. Or, for amusement, try it first with no bypass caps and then add an electrolytic in the 47-220 uF range, see what if any difference it makes.
In terms of brands you either go with a generic model, a low impedance model, or a audio model. There probably isn't much difference between brands within those three classes. While I favor low impedance types, 47 labs probably uses generic parts.
naz: I'd use those 220uF FC's for all C4-C11 and not give it much further thought until I was ready to really play around with it later.
-R
Thanks rjm
I will try using all 220uF FC caps for now and see how it goes, my other idea is to pick up some Elna Cerafine caps and drop those in.. I guess the best idea is just to get something in there so I can start listening to it.. 😀
Naz
I will try using all 220uF FC caps for now and see how it goes, my other idea is to pick up some Elna Cerafine caps and drop those in.. I guess the best idea is just to get something in there so I can start listening to it.. 😀
Naz
Hey all... I just built my phonoclone and a 12V powersupply. I never used a bridge rectifier before and bought this one (bought 2 but am only using 1) from partsexpress...
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=050-060
I am getting weird DC readings from it's output and am assuming this is because it's not full wave rectification... I am trying to build my powesupply like this...
http://www.geocities.com/rjm003.geo/rjmaudio/images/phono_dia2.gif
Can I wire 2 of these together to get full rectification or should I just get something like this from mouser?
http://www.mouser.com/index.cfm?han...uctid=340289&e_categoryid=131&e_pcodeid=52602
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=050-060
I am getting weird DC readings from it's output and am assuming this is because it's not full wave rectification... I am trying to build my powesupply like this...
http://www.geocities.com/rjm003.geo/rjmaudio/images/phono_dia2.gif
Can I wire 2 of these together to get full rectification or should I just get something like this from mouser?
http://www.mouser.com/index.cfm?han...uctid=340289&e_categoryid=131&e_pcodeid=52602
I'm using the exact same 400V/25A bridge rectifier in my Phonoclone now.
You can use one or two. Hooked up correctly - carefully check the package for the terminal identification - they work great. Actually I really like the sound of these parts.
Without more info, I have no idea what you mean by "weird DC readings", but don't forget that until you actually hook it up to the Phonoclone there is no capacitance in the power supply, so the output is just a rectified AC wave, with no smoothing. You can still verify the polarity, though, even if you cant measure the true DC output until you have capacitance and ideally a load there.
-rjm
You can use one or two. Hooked up correctly - carefully check the package for the terminal identification - they work great. Actually I really like the sound of these parts.
Without more info, I have no idea what you mean by "weird DC readings", but don't forget that until you actually hook it up to the Phonoclone there is no capacitance in the power supply, so the output is just a rectified AC wave, with no smoothing. You can still verify the polarity, though, even if you cant measure the true DC output until you have capacitance and ideally a load there.
-rjm