Step Up Transformers? Pros / Cons?

[sergeauckland]

If you're buying it new, the dealer ought to be able to set it up properly and earn their markup.

If you're doing it yourself or buying used, make friends with a local tech type and put it on their bench. In Seattle, that should not be difficult to find.

I would be very surprised if any dealer knew how to do that. I'd be extremely surprised if any turntable dealer had an oscilloscope and astounded if they knew how to work it.

As far as I can tell, most dealers 'understand' changing mains cables to affect the turntable's sound, but wouldn't know a capacitor if it bit them on the leg.

S.

 

[Zog]

I would be very surprised if any dealer knew how to do that. I'd be extremely surprised if any turntable dealer had an oscilloscope and astounded if they knew how to work it.
S.

If they actually offered to do that then you could knock me over with a feather. And if they actually did do all that in a home visit I would stop taking hallucinogens.

 

[SIY]

A couple of general notes:

1. Setting an input to "0" pF does not mean it's 0 pF, and in fact, it's seriously doubtful that it will be. And the cable going from the transformer to the input will not be 0 pF. And 0 pF may or may not be the desired load, depending on the cartridge and transformer.

2. If a dealer doesn't have a square wave generator and scope, get another dealer. This is not exotic equipment and any service department will have it. Given that some people plopped down a kilobuck for a step-up, perhaps spending less and investing the difference in a 'scope might not be a bad thing!

3. Am I making step-ups seem like a very hit and miss proposition? They are indeed. Set it up right, and there's nothing that will beat it. But as I've said before, 99% of the time, it's not set up right.

4. Something I've linked before: doing it right.

 

[Frank Dernie]

Well I confirmed with the designer that the phono stage was different after the D-Premier. Not a lot different, he said, but different. Now all of the models from 200 to 1000 have the same which he believes is more adjustable and more accurate than any other.
As an aside he mentioned they looked into making the configuration not being on an SD card and he pointed out that not only do legacy units have no network connection capacity but that they want it to be stand alone so when a unit is switched on not connected to the network it stillhas its configuration. After looking into the pluses and minuses he isn't going to change the configurator away from their web site.
Another aside, if you do want to make "active" speakers if you give him the transfer function for each unit he will send you a configuration file to achieve it. They have already done this with 4 Devialets driving B&W Nautilus for 2 customers.

 

[Soniclife]

View attachment 29597View attachment 29597

Not seen the shiny black versions before, is the fetish look deliberate?

 

[watchnerd]

2. If a dealer doesn't have a square wave generator and scope, get another dealer. This is not exotic equipment and any service department will have it. Given that some people plopped down a kilobuck for a step-up, perhaps spending less and investing the difference in a 'scope might not be a bad thing!

In my particular case, I bought my cartridge online, my tonearm online, my turntable and amp 2nd hand from Audiogon.

So there really isn't a dealer in the picture and never has been.

 

[SIY]

Be nice to someone with a scope.

 

[watchnerd]

Be nice to someone with a scope.

I would if I knew anyone with a scope.

 

[SIY]

You're in Seattle. Surely there's an audio club or repairman or kind forum member from here or elsewhere that can help. Be resourceful!

 

[watchnerd]

You're in Seattle. Surely there's an audio club or repairman or kind forum member from here or elsewhere that can help. Be resourceful!

Sure...I didn't say I couldn't find one...but audio repairmen with scopes are a dying breed. As are audio clubs with scopes. As are dealers with scopes.

No offense, but being in a midsize metro doesn't solve for the death of brick and mortar dealers with scopes.

As for asking....

@amirm Are there folks at Madrona who can measure SUTs with scopes? Or are they all home theater / room correction techs?

 

[Frank Dernie]

Not seen the shiny black versions before, is the fetish look deliberate?

All the colours were gloss so I suspect this is more the photographers choice of lighting.
I was going to order a BRG pair but preferred the Epilogs on the final comparison. I very much wanted these for the styling though...

 

[watchnerd]

For SUTs that have two ratios / gains available, what are the pros / cons of using the lower vs higher gain options?

 

[SIY]

For SUTs that have two ratios / gains available, what are the pros / cons of using the lower vs higher gain options?

There's not a general answer to this- it's one component of overall system gain structure. Optimum gain will depend on the cartridge output, preamp gain, and overload. A higher gain may be worse from a frequency response POV, but it may not be, and if it is, that's easily adjusted, usually with an RC network across the secondary.

edit: I should have been explicit that it also depends on whether the phono preamp will still be the noise limitation. If it is, the higher transformer gain will reduce the noise.

 

[watchnerd]

Came back from my week long business trip to find my K&K Audio / Lundahl 1931 SUT has arrived:

There are a couple of tiny switches on the board to control the gain, plus some jumpers for grounding.

I need to add resistors at the bottom (after all, this is normally sold as a kit) to add resistive loading.

The AT33 series, with an internal 10 ohm resistance, will want a minimum of 100 ohm or higher, so I'll need to do some calculations for what the parallel resistor value needs to be to achieve that.

 

[sergeauckland]

AT's own recommended transformer for the AT33 is the AT630. This has a 10:1 turns ratio, thus presenting the cartridge with a 470ohm load when used into a standard 47k MM input. It's what I use, and have been completely satisfied with the results.

I also have an EMT TSD15 cartridge which seems perfectly happy into a 47k input without a step-up.

S

 

[watchnerd]

AT's own recommended transformer for the AT33 is the AT630. This has a 10:1 turns ratio, thus presenting the cartridge with a 470ohm load when used into a standard 47k MM input. It's what I use, and have been completely satisfied with the results.

I also have an EMT TSD15 cartridge which seems perfectly happy into a 47k input without a step-up.

S

I may not need to add any parallel resistors at all, as this is what the docs say:

"LL1931/LL1933 set for a step-up of 18dB (with no Rload the load impedance is 727 ohms)

LL1931/LL1933 set for a step-up of 24dB (with no Rload the load impedance is 180 ohms)"

Between the 200 ohms I was using on the Devialet and what you're saying (470 ohms), I may be able to just get away as-is, depending on the gain.

 

[sergeauckland]

I may not need to add any parallel resistors at all, as this is what the docs say:

"LL1931/LL1933 set for a step-up of 18dB (with no Rload the load impedance is 727 ohms)

LL1931/LL1933 set for a step-up of 24dB (with no Rload the load impedance is 180 ohms)"

Between the 200 ohms I was using on the Devialet and what you're saying (470 ohms), I may be able to just get away as-is, depending on the gain.

I've always thought that with an MC cartridge, gain was more important than load once some 10x the cartridge's coil resistance. Excessive gain might help reduce noise, but noise shouldn't be a problem with any decent phono stage, whilst overload margin could well be. The example of my TSD15 is a case in point. It has an output of 200uV per cm/sec and a resistance of 24 ohm, so should theoretically benefit from 5-10x stepup, but is fine into EMT's own MM phono stage which has sufficient gain adjustment and low enough noise for it not to be audible.

In your circumstances, I would use the lower gain setting which will give you more adjustment on the volume control and a much better overload margin, whilst still hopefully being of sufficiently low noise.

S

 

[watchnerd]

I've always thought that with an MC cartridge, gain was more important than load once some 10x the cartridge's coil resistance. Excessive gain might help reduce noise, but noise shouldn't be a problem with any decent phono stage, whilst overload margin could well be. The example of my TSD15 is a case in point. It has an output of 200uV per cm/sec and a resistance of 24 ohm, so should theoretically benefit from 5-10x stepup, but is fine into EMT's own MM phono stage which has sufficient gain adjustment and low enough noise for it not to be audible.

In your circumstances, I would use the lower gain setting which will give you more adjustment on the volume control and a much better overload margin, whilst still hopefully being of sufficiently low noise.

S

I'm not sure if this is true in my case since the MM input is configurable to accept from 1mv to 10mv (it's DSP based, uses an ADC).

In other words, the overload margin is adjustable.

But maybe I'm missing / not understanding something.

 

[sergeauckland]

I'm not sure if this is true in my case since the MM input is configurable to accept from 1mv to 10mv (it's DSP based, uses an ADC).

In other words, the overload margin is adjustable.

But maybe I'm missing / not understanding something.

In 'normal' analogue phono stages, sensitivity and overload margin are connected, as more gain reduces overload margin and vice versa. This may be the same with an ADC system, but may not be, as it depends what happens before the ADC, in the analogue domain. If the analogue gain is switched, then yes, overload margin tracks gain, but if the sensitivity is done digitally, after the ADC, then it will not track, as the ADC will overload at the same point regardless of digital gain. In practice, it may not matter as the ADC process has very low noise, so there can be lots of headroom allowed.

S

 

[watchnerd]

I think level matching is important. The Rothwell site the OP referred to is a nice discussion of the basic considerations for matching SUT and cartridge. My first SUT was a Bob’s devices Sky 40, which I paired with an AudioTechnica AT1000 (handmade by a Japanese grandma in the Audio Technica basement). That cart has a rated output of 0.2 mV and internal impedance of 3 ohms. Bob Sattin likes to match impedance, so he recommended his Sky 40. My phono stage has an input impedance of 47000 ohms, so doing the math, a Sky 40 presents a load of about 29 ohms to the cartridge. That’s pretty darn close to the theoretical minimum of 30. So far, so good.
I was pretty happy with the result. My phono stage has separate MC and MM inputs. The MM is straight tube (12AX7), but the MC input adds a jFET gain stage between the cart and the first tube stage. The MC input actually sounds pretty good with the AT1000, but the volume is a little low because the cart only puts out 0.2 mV. With the Sky 40 into the MM input, it was a lot louder. But I think it was too much. The signal level presented to the MM input was 40x0.2= 8 mV. The input sensitivity of the MM input of the phono stage is rated at 4.5mV. So while the Sky 40 gave a good impedance match, I think it was overdriving the input stage.
I decided to try a K&K diy kit, because at the time Lundahl had just come out with a new series of transformers, one of which seemed a likely good match as it had a turns ratio of 1:24. That gave an output level of about 4.8 mV, which matched the input sensitivity of the phono stage much better. I’ve been using that setup since, and find it marvelous.

Did you add any load resistors to your Lundahl / K&K kit?