A Visit to the Phono Doctor ... and other stories

[IslandPink]

I had an emergency drive out to Halifax at the weekend .
My phono amp was creating massive amounts of hum, since I brutally attacked the top plate last weekend to suspend the signal circuitry ( this was hoping to cure some annoying but non ear-damaging hum that was there before ) .
After about half an hour ( and some lunch ) Dr. 'Eagle-Eye' Gorham was able to spot that I had a loose joint in my earth bus. I had forgotten that the earth line was not actually one continuous piece of copper, but had a join across some double sided tag strip in the middle . He noticed ( underneath the biasing batteries for stage 2 ) that the copper wire was only loosely associating with the tag strip . One quick soldering job and the thing was quiet and sounding very nice .

Anyway, we had about 5 or 6 hours of listening including the 'fix' and discovered a few things .

I'll try to detail these a bit more later , but Nick's phono is definitely very very good - but not as refined as mine at the top end . I can think of some reasons why ( coupling caps, step-up transformers ? ) . The mids and bass are better . There are better bass dynamics , and better tonal colour through the bass and mids. There is a sense of better 'harmonic integration' through the bass and mids . It makes the music structure a little more organised and meaningful .
This is interesting, because I don't think there is much more, apart from some very expensive bits , that I can do with the D3a, D3a phono now . The recent mod of the lower-impedance RIAA section ( 20k start ) has been very good though .

So, more to follow .

Mark

[Nick]

Yes, just to add to what Mark has posted, his phono stage is doing something very nice at the top end. So I have sent a email off to Tribute as I can't help thinking that those wizzy stepups have some part in this.

[IslandPink]

So anyway, last night the motor on the turntable ( Hyperspace ) packed-in . Very peed-off .

OK the TV packed up this evening . This is getting ridiculous .....
I started to freak out with the silence, but the neighbour lent me a portable so I'm OK now .

MJ

[Andrew]

Mark, you've heard both S&B and Tributes. Obviously the Tributes won your heart, but was there much in it?

PS Jon Chapman who used to OEM S&B step ups until S&B decided to concentrate on their won products only has got Magnequest to wind a new step up for him, he's going to supply these raw as well as in his own products.

-- Andrew

[Andrew]

Anyway, we had about 5 or 6 hours of listening including the 'fix' and discovered a few things .

I'll try to detail these a bit more later , but Nick's phono is definitely very very good - but not as refined as mine at the top end . I can think of some reasons why ( coupling caps, step-up transformers ? ) . The mids and bass are better . There are better bass dynamics , and better tonal colour through the bass and mids. There is a sense of better 'harmonic integration' through the bass and mids . It makes the music structure a little more organised and meaningful .

Mark

The LCR does require some pretty large coupling caps to maintain freq response if the cap is topologically placed before the LCR units.

-- Andrew

[IslandPink]

It's close between the S&B's and the Tributes . The Tributes ( 1:10's that is ) seem to be a bit more detailed and have slightly more tone in the mids and treble . Both units are very good, but the S&B's need more effort to run-in .

I'd like to see if the treble of the LCR phono units can be improved , because the rest of their performance is great . I was talking to Nick about the big caps he's got in there, and suggested since he's using eg. 22uF , why not try some Black Gate 22u/350 VK's ? ... a bit of money required of course , but they are not very expensive , and are quite neat and small .

At present I would hold back on buying the bits for that circuit , but I'd like to hear yours also to compare . If I built it, I wouldn't need the large exit coupling cap , which is only needed to drive a TVC etc in Nick's system . I'd probably go E810F , D3a and run the D3a's as per my current one, say 12 to 13mA , save some PS current .

There are a few other things I need to sort before the phono goes up another stage anyway - it's pretty good as it is .

Mark

[Andrew]

I'd like to see if the treble of the LCR phono units can be improved , because the rest of their performance is great . I was talking to Nick about the big caps he's got in there, and suggested since he's using eg. 22uF , why not try some Black Gate 22u/350 VK's ? ... a bit of money required of course , but they are not very expensive , and are quite neat and small .

Mark

With a bit of jiggery pokery I managed to get the internal coupling caps down from 22uF to 22nF, the biggest cap now is the output cap and, as you say Mark, this is, to some extent, governed by the external load.

The 1k5 is actually somewhat overly honest with poor eighties pop recordings etc and will be bright if the material calls for it. I suspect much of that is down to the cheapo output coupling cap, generic load resistors etc. I have a Russian PIO lined up for output duty but I hope to try some interstages on the output instead.

-- Andrew

[IslandPink]

Is the extra 3.18uS corner part of Dave's supplied iron , or is just a resistor in the 2nd leg ?
I'd quite like the option to NOT have that part, as I don't feel it does much other than emphasise surface noise ... Ooops , unfashionable viewpoint .

MJ

[Andrew]

Completely optional, Dave just supplies the chokes "au naturelle" as he puts it. So you can chose how exactly to implement the RIAA, S&B is the simplest circuit, I did the full monty including the 50k point, cos I wanted to try it.

You do need to keep the PSU well away from the chokes, however, unless you shield & pot them like S&B did.

-- Andrew