Phono Step-up Transformer

107.2.245.185

Posted on July 15, 2021 at 16:42:24

throwback
Audiophile

Posts: 762
Location: Colorado
Joined: December 8, 2003

I have been playing with a modded Atma MP-3 to replace my highly-regarded (and expensive SS line and phono preamps). Very nice improvements I can describe only in non-engineering terms like: "more 'there there'," "rounder," more "relaxed," more "air" and "sense of space," non-"transistory." In short, I am enjoying it more. But - - and it's a fairly small "but" - - it is a bit noisy when used with my Miyajima Madake low-output moving coil cartridge (.23 mv).

The obvious solution is a step-up xformer. But which one? Atma sells the Jensen 347, but Dave Slagle also makes one as does S.A. Lab and several others. Has anyone made a comparison? What are your recommendations.

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Whatever stepup you get

Ralph

11:14:22 07/16/21

RE: Whatever stepup you get

throwback

14:40:50 07/16/21

RE: Phono Step-up Transformer

Elixir63

21:33:25 07/15/21

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Whatever stepup you get

Ralph

11:14:22 07/16/21

RE: Whatever stepup you get

throwback

14:40:50 07/16/21

RE: Phono Step-up Transformer

Elixir63

21:33:25 07/15/21

4

RE: Phono Step-up Transformer

throwback

05:33:27 07/16/21

3

RE: Phono Step-up Transformer

Elixir63

08:52:51 07/16/21

2

RE: Phono Step-up Transformer

Ralph

15:12:57 07/16/21

RE: Phono Step-up Transformer

throwback

14:30:24 07/16/21

RE: Phono Step-up Transformer, posted on July 15, 2021 at 21:33:25
Elixir63 Audiophile Posts: 101 Location: North Coast Joined: April 19, 2021	Had you thought of consulting the cartridge manufacturer ? Might be a good place to start.

RE: Phono Step-up Transformer, posted on July 16, 2021 at 05:33:27
throwback Audiophile Posts: 762 Location: Colorado Joined: December 8, 2003	Yes. They make one too. Pretty darned expensive though. Thanks for responding.

RE: Phono Step-up Transformer, posted on July 16, 2021 at 08:52:51
Elixir63 Audiophile Posts: 101 Location: North Coast Joined: April 19, 2021	I have two friends who are using step-ups.One uses an Allnic/Purpleheart NS and the other a Myajima Madake with their Myajima step-up. I prefer a good solid-state unit, prior to a tube pre.

Whatever stepup you get, posted on July 16, 2021 at 11:14:22

Ralph
Manufacturer

Posts: 4778
Location: Minnesota
Joined: April 24, 2002

-make sure that you pay attention to the proper loading for it.

In some cases the loading will be simply hooking it to the preamp. In other cases such as the Jensen we use, there is a specific loading network of a resistor and capacitor in series that will be needed on the cartridge loading terminals. Jensen has that information on a pdf.

0.23mV is indeed a bit low for the MP-3. Your input 12AT7 tubes (the two by the rear panel) really have to be quiet for that to work. If loaded right the SUT will work quite well. BTW, the Jensen has multiple windings so it can be configured for different gain settings (which also affects the loading). We usually use the lowest gain setup we can for them as they mess with the sound the least that way.

RE: Phono Step-up Transformer, posted on July 16, 2021 at 14:30:24
throwback Audiophile Posts: 762 Location: Colorado Joined: December 8, 2003	Thanx, Elixir63, but I have been the SS route and and I prefer the tubed MP-3.

RE: Whatever stepup you get, posted on July 16, 2021 at 14:40:50
throwback Audiophile Posts: 762 Location: Colorado Joined: December 8, 2003	Good info, Ralph. Thanks.

RE: Phono Step-up Transformer, posted on July 16, 2021 at 15:12:57

Ralph
Manufacturer

Posts: 4778
Location: Minnesota
Joined: April 24, 2002

I prefer a good solid-state unit

I understand the lower noise thing quite well.

The problem I have with solid state is not what they sound like. Its ticks and pops. Now this doesn't happen all the time, but its quite annoying when it does.

The cartridge is an inductor and the tonearm cable has capacitance. Together they create an electrical resonance; with a LOMC cartridge this might be at a couple of MHz- and it can be a good 30dB peak! (30dB suggests 1000x higher than the cartridge signal)

If that peak is energized (goes into 'excitation', the radio world term for this phenomena) the resulting energy can overload the input of the phono section, resulting in a tick or a pop, unless the input circuit has a very good high frequency overload margin. With tubes this is easy to do, so if there is an overload in a tube phono section it starts at the output of the circuit and progresses backwards if the input signal continues to be increased.

In a solid state circuit the overload can occur right at the input circuit itself. If this happens you can get a tick or a pop, sounding for all the world as if its on the LP surface. If the phono section employs an opamp at its input this can be very hard to avoid!

Now if you design with this electrical peak in mind, a side advantage is that you will find you don't need the 'cartridge loading' resistor since its there to detune that electrical peak; IOW its there for the benefit of the phono section rather than the cartridge.

When you load the cartridge from the stock 47,000 ohms down to 100 ohms you are asking it to do over 2 orders of magnitude more work. This causes the cantilever to get stiffer, which can affect how the cartridge performs in the arm.

OTL Asylum

Phono Step-up Transformer

107.2.245.185