The Phonoclone and VSPS PCB Help Desk

Thanks rjm... The DC voltgage reading from the bridge was sweeping from 0 to 14v. I did have it wired incorrectly until I downloaded a datasheet to see how each of the 4 posts were supposed to be wired. I blew a few fuses until I figured this out and might have damaged it. I swapped in the new one at it gives a strong consistant DC reading. The problem now is that the circuit is dead quiet... not a buzz, not a squealch, not a peep... nada from either board/channel. I just noticed that the voltage regulators I am using are 12V negative. Were these supposed to be positive?
 

rjm

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I just noticed that the voltage regulators I am using are 12V negative. Were these supposed to be positive?

The negative regulators go in the position marked 79xx, the positive in the position marked 78xx. The dot denotes pin 1.

I should apologise, that's not as clear as it perhaps should be.

Worse, on the beta version the regulators are unmarked. The two negative regulators go on the edge with the V- pad, the two positive regulators go on the edge with the V+ pad. Again, the dot marks pin 1.

Also, in the diagram, I show bridge rectifiers with the AC connections side-by-side. I do this because its easier to draw the connecting wires this way. Of course on most bridges the AC connections are opposite on the diagonal. You are responsible for correctly wiring whatever configuration you happen to to use, simply because there are far too many options for me to cover individually.

As more people get into building the power supplies, its becoming clear to me that to assume the distiction between a 7812 and a 7912 would be obvious to everyone was a mistake on my part. I'm not quite sure what to do about it ... the only advice I can give is if unsure, ask first here for clarification before plugging it in and blowing things up.

needlz, your regulators are most likely still ok, just replace the two on the positive rails V+ of each channel with 7812's.

-rjm
 
Don't sweat the rectifier or regularor thing. Your directions are great... I was only mentioning it because I found out my newbie problems. The funny part is I always seem to figure out what happened after I post a question. There must be something internally that happens after asking for help. :) I have always used 4 diodes (or tube) for rectification and never used the all-in-one box. I have some 7812s handy and will replace them now.
 
I didn't have a large enough enclosure for both boards but I did have a bunch of smaller ones from my stompbox makin' days. Each enclosure has it's own mic unbilical coming in. The seduction sitting next to them is sweating... might get religated to the other room.

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.
 

rjm

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Joined 2004
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Ooooh. That's pretty neat to think that you got even one Phonoclone PCB stuffed in there! Those twisted pair CAT5 interconnects and Hammond boxes, that's a build close to my heart, indeed.

When you get the chance, could you report on the noise level, with and without the inputs connected?

Thanks,

-R
 
The enclosures are mechanically tied together (will have them on stand-offs if they sound good post burn in). I was going to connect a twisted pair from the TT and split them between the two but it seems going to one from the TT and connecting the two enclosures did the trick.

The den shares a wall with my neighbor's bedroom so I will need to wait until manana before I can resume the listening.
 

rjm

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If its basically quiet with the inputs disconnected, switching to a shielded phono interconnect might be a good idea, combined with putting as much distance between the input signal cables and potential noise source (Phonoclone power supply, turntable motor, other power transformers.) as possible. Since you didn't have the problem before, the Phonoclone power supply is an obvious suspect.

If its really RF interference (radio stations, rather than hum), you could try connecting a 220 pF cap over the inputs (pin2,3) of the input op-amp, as per the earlier post by cjunk.

Sounds to me though like you've got magnetic field coupling from a power supply transformer into the interconnect cable. The Phonoclone circuit, having zero input impedance, may be more sensitive to this than other topologies, or it might just be that the high gain makes the noise more obvious.

-R
 

rjm

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roughly 220pF...

Sounds like you just need to busy yourself with some cable routing and general housekeeping. Hope that's all it is, anyway.

By the way, the Phonoclones inverting input topology means its intrinsic noise behavior is the opposite to most components. Its quietest with the inputs open, and noisiest with the inputs shorted. Do not, btw, short the inputs. Its not pretty. The positive side is that you can change headshells and so forth with the volume turned up without hearing a thing through the speakers.
 

rjm

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Pictures of the completed Phonoclone (1)

The "guts" of it, completed and connected but chassis-less.
 

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rjm

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Pictures of the completed Phonoclone (2)

The gritty details: Panasonic filter caps, polypro RIAA caps, Black Gate output coupling. Riken Ohm (R1, R2), Allen Bradley (R8), Takahashi (?) carbon comp resistors (RIAA), and Panasonic carbon films for the remainder (R3, R4, R7). Socketed Analog Devices OP27 input and output.

I was asked to build one, so I did. This is the result. The stuffing and soldering when smoothly with no problems. I'll be giving it a quick test listen before I ship it, and report back here if I encounter any anomalies.

/R
 

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rjm

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Initial comments, with both channels working.

  1. 100uF is a sufficiently large value for C8-C11. (Original prototype had 220uF)
  2. R2=1k2 gives a very useable gain with the DL103 @ 40 ohms. Total calculated gain 60 dB, 30 dB per stage.
  3. Noise is on the same level as the prototype, with a little bit more hash - most of this is surely due to it running as in the photo above, no case and unshielded wires dangling all over. Noise makes no impression at normal listening levels, even now.
  4. No hint of any RFI/EMI problems.
  5. Black Gates burnt in for 100h at 20V AC prior to use. OP27s also burnt in for several hundred hours. (used previously in my prototype.)


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    Totally subjective first impression is that this Phonoclone sounds more effortless, or elegant, than the first one I built. The soundstage has gone from 3D to near holographic. Wide use of carbon composite resistors most definitely did not result in a bad case of the fuzzies. Actually I highly recommend you try them.
 
Well I just finished my Phonoclone, I think everything turned out pretty well. I used a 330pF film cap on IC1 input since it was the only thing I had sitting around and I was getting some hum and hint of radiostation on the input. It's dead quiet now which is nice. What would the diffirence in sound between using the 220pF cap vs. the 330pF? My system consists of Denon DL-160 cartridge mounted to a Rega P25 table. I'm pretty much just driving a gainclone with a pot on the input. Hopefully I can post some pics soon and some other folks will do the same! :D

Michael
 
115 mV DC in and 240mV AC out

Finally able to power the phoneclone up, after an internal relocation inside our house.

One Channel is perfect, the other one gives 115 mV DC in and 240mV AC out, with no signal attached. I don't have a scope to use at short notice.

At the start I had a loose earth on the negative power.

What can have happened?

E&E