Phono Cartridge Loading

[Clive]

Clive, is the project you're building described as a 'head amp'? It takes place of the SU TX I'm guessing yes?

DTB

Hi Dave, yes it would replace my SUTs. I have the parts from Andrew to build the Marshall head amp but I thought what the heck I'll build the Piccolo, it seems well executed.

[Lee S]

Will you take £20 for those old S&B SUTs you won't be needing then Clive ???

[Clive]

Will you take £20 for those old S&B SUTs you won't be needing then Clive ???

Hi Lee, thanks for your kind[ offer, mine are even in those nice Bent Audio Mu cases but I might just be looking for a little more than £20......but I don't want to get ahead of myself, if might be the Piccolo I'll end up selling.

Cheers,
Clive

[Gerry]

Lee

Great news.
It is a cracking cartridge for the money if set up correctly.
Don't believe everything you read about it....especially relating to VTA.
Sit back and enjoy. It is a musical little number!
And will get better...

Regards
Gerry

[Lee S]

It has actually transformed it quite a bit Gerry. The soundstage seems wider too. It is very musical indeed. I like what it is doing now. It seems a lot more balanced. It's put flesh on the bones and improved it no end.

I will have to get the router out to lower the VTA even further. Might be worth it though. I can fit the levelling nuts back in and have a more accurate play with the VTA.

How long are we talking before it settles down for good? It has probably only got 10 hours on it so far (not bad in two days!!).

Is the 103R that much better than the 103?

Cheers

[Clive]

Could you effectively raise the VTA by putting some form of spacer (cardboard?) under the platter mat as a test to see if you need to get your router out?

[Lee S]

Yeah, I suppose I could Clive. I could slip another mat under the one that's on now. That would give it another couple of mm. Will give it a try tomorrow I think.

Cheers

[pre65]

Hi-thats what i have done to mine today.

Reading Gerrys comments i thought i would give it a go.

That,and the CCS on my 832 has given me real bass now,and not at the expense of mid and treble.

[Cressy Snr]

Hi-thats what i have done to mine today.

Reading Gerrys comments i thought i would give it a go.

That,and the CCS on my 832 has given me real bass now,and not at the expense of mid and treble.

I take then that you are pleased with the results of your mods to the 832A output stage of your amp Philip.

Steve

[Lee S]

...and I take it that you're only playing with the 832 whilst you wait for the Dodd Special to settle down? Have you had a good listen to that yet Philip? What's it sounding like? Are you pleased with it?

[Andrew]

Hi Lee,

1:10 might be better, less lossy, I can't help feeling that you don't get something for nothing, if you see what I mean.

I've been meaning to try this on mine with primary loading, but not got a round tuit yet...

cheers,

-- Andrew

[Dave the bass]

To Andrew,

So it's this unwanted reactance that is the unwanted quantity in the SUT's that were trying to null out but in actual fact are shifting in the freq spectrum yes?

The pesky stray capacitance is causing the problem and combining that with the coils inductance is forming the filter you speak of yes? Have I got that right?

Sorry to keep asking questions but I want to learn what we're all doing here, would you mind moving closer so we can discuss this further down the pub

DTB

[Andrew]

To Andrew,

The pesky stray capacitance is causing the problem and combining that with the coils inductance is forming the filter you speak of yes? Have I got that right?

Yes, basically the transformer cannot be a perfect device, it will have parallel and series capacitance, plus series resistance and other unwanted stuff going on - not to mention coupling loss.

Equally, the cart is not a perfect generator, it will have an output impedance.

The 103 has about 40R output impedance so is less perfect than say a Kontra B at 5R. Perhaps I should use "ideal" device not "perfect" device. So a 103 is less ideal, but its not actually broken in any way.

When you parallel a big resistor across the windings it forms and LCR filter that approximates a 3rd order low pass, thus knocking out the treble.

With primary loading you're using a smaller resistor in parallel with the windings, so the 3db point of the filter is not as low down in the freq range cos the resistive component of the filter is not as big.

Finally, a higher Z out cart is less able to deliver current into the transformer thus exacerbating the problem.

Clive says this issue is , ot some extent, present with a Kontra B and I have no reason to doubt him.

cheers,

-- Andrew.

[Dave the bass]

Thanks for the further explanation Andrew,

Right, I now have 560R resistors across the primary. I'll get connected up tonight and see whats happening. I've got a free night to play silly buggers and do lots of listening.

DTB

[Lee S]

Slapped another mat under the original mat to give me another 3mm raise. The arm is now slightly arse down and likewise, so is the cart. This is another improvement again!! It just gets better. The mids and highs have not suffered, but nor have they improved. Only the bass and maybe the low-mids appear to have improved. More weight and authority. More meat again. Listening to PFs "Comfortably Numb", I can actually say that, yes, I am Mr. Gilmour - by the performance of this £80 piece of plastic!!

I think I am going to reduce the gain on the SUTs again to 1:10. I like the primary loading though and I will have another play with loading when the SUTs are back to the original setting.

Cheers