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Old 11th October 2003, 12:23 AM   #1
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Default Pearl input overload?

Hi,

I looked through the archives but didn't find any discussion on this. I'm trying to figure out the optimum setting for my MC stepup transformer (Lundahl LL9206). It can be set for 1:5, 1:10 and 1:20 turns ratios. My cartridge is a Denon DL103, which has an output of 0.29mV.

I currently have the 9206 set up for 1:10 (and the Pearl's input resistor adjusted to present the appropriate reflected load to the cartridge), which means the Pearl is 'seeing' roughly a 3mV cartridge. Looking at the manual, this isn't the optimum input level as far as noise goes, lower would be better. However, the gain structure of the rest of my system prevents me from going any lower. In fact, I would like to have more gain out of my vinyl front end.

So, my question - if I connect the 9206 for 1:20 (and adjust the input resistor accordingly), that would make the Pearl 'see' a 6mV cartridge. Assuming I ignore noise for the moment (my amps are SETs, so I think the Pearl's THD will be orders of magnitude lower), is this input too high for the Pearl? Will I clip or otherwise overload the phono stage by using this connection? I looked through the manual, but didn't see any discussion of how much overhead/margin this phono stage had.

Any input would be appreciated. I thought I'd run it by you guys before I try to re-solder 30AWG wire

Thanks,
Saurav
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Old 11th October 2003, 03:26 AM   #2
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Default Re: Pearl input overload?

Quote:
Originally posted by Saurav
Hi,
I am surprised that with a 10:1 step up and your 103 that the gain is low. Does a disc player work okay here?
The noise issue comes from hum, step ups can be a pain. Moving cables and other units can help. But pay attention to grounds, the arm, the turntable itself, and the phono.
I had hoped to use my Denon 103R (also 0.29mv) straight in with a 900 ohm loading resistor. Sounds like the step up will need to stay.
On the step ups, usually the lowest gain sounds best. If you can live with 10:1 it should sound better than wiring it up at 20:1.

George

I looked through the archives but didn't find any discussion on this. I'm trying to figure out the optimum setting for my MC stepup transformer (Lundahl LL9206). It can be set for 1:5, 1:10 and 1:20 turns ratios. My cartridge is a Denon DL103, which has an output of 0.29mV.

I currently have the 9206 set up for 1:10 (and the Pearl's input resistor adjusted to present the appropriate reflected load to the cartridge), which means the Pearl is 'seeing' roughly a 3mV cartridge. Looking at the manual, this isn't the optimum input level as far as noise goes, lower would be better. However, the gain structure of the rest of my system prevents me from going any lower. In fact, I would like to have more gain out of my vinyl front end.

So, my question - if I connect the 9206 for 1:20 (and adjust the input resistor accordingly), that would make the Pearl 'see' a 6mV cartridge. Assuming I ignore noise for the moment (my amps are SETs, so I think the Pearl's THD will be orders of magnitude lower), is this input too high for the Pearl? Will I clip or otherwise overload the phono stage by using this connection? I looked through the manual, but didn't see any discussion of how much overhead/margin this phono stage had.

Any input would be appreciated. I thought I'd run it by you guys before I try to re-solder 30AWG wire

Thanks,
Saurav
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Old 11th October 2003, 05:38 AM   #3
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Well, I have a passive linestage (so no gain there), and a 3.5W amp with not a whole lot of gain there either. I could change either of those, but I like them both, so at this point I'm looking for other alternatives.

Quote:
On the step ups, usually the lowest gain sounds best. If you can live with 10:1 it should sound better than wiring it up at 20:1.
Didn't know that, thanks for the info. I wonder why that is so?
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Old 12th October 2003, 12:20 AM   #4
Boban is offline Boban  Canada
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Hi,
I have Pearl with Lundahl 9206 (1:10 mode) and using it with low output catridge, around 0.4mV. This is more than enough gain for me.

And, somewhere I found the quote that max gain is the way to go, guess I am confused now.....

Boban
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Old 12th October 2003, 12:24 AM   #5
Boban is offline Boban  Canada
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George,
resistor of 900 ohms will be only 9 ohms under 1:10. This will be way to low for any cartridge. Am I missing something?

Boban
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Old 12th October 2003, 03:57 PM   #6
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Quote:
Originally posted by Boban
George,
resistor of 900 ohms will be only 9 ohms under 1:10. This will be way to low for any cartridge. Am I missing something?

Boban
Boban,
Are you loading the output of the Lundahl with a lower value resistor than the 47K to get it down to 900 ohms? I do not understand where the 900 ohms comes in.
The effect of ratios on sound quality came from discussions with Audio Note UK. They recommend using the lowest ratio that can be tolerated. Also Sowter has the same comment on their website.
I think that high ratio step ups can br built that deliver good sound quality, but it is much more difficult. The bad things like interwinding capacitance and losses are worse with the higher ratio models. Plus look at the current. The current coming out of a low output moving coil is not very high, then decrease it either 80% (5:1), 90% (10:1), or 95% (20:1). This is where the input capacitance of the phono stage comes in. A couple of uA's will not drive much capacitance.
The reflected impedance is a funny issue. Most recommend matching the relected load to 10 times the cartridge. But also the actual impedance of the step up (resistance mainly) to the cartridge also. The impedance of the 103 is 40 ohms. The impedance of the Lundahl will vary depending on how it is hooked up. Which ratio is closest to the 40 ohms of the cartridge?
For reference I use a AN step up wired for 12 ohms with my 14 ohm Denon 103R. The other hookup option is 3 ohms. This is achieved by either series or paralleling the secondaries. The series connected secondaries cut the step up ratio in half also.
But the relected impedance is not even considered here. AN UK and Sowther seem to base their recommendation on actual cartridge and transformer impedance.
Check a couple transformer manufacturer websites to see if there is either more up to date info or conflicting opinions.

George
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Old 12th October 2003, 04:24 PM   #7
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Thanks, you brought up a couple of points that I hadn't really thought ot.

Nevertheless, if anyone has any idea of how much input signal the Peral can handle before it starts to overload, that would be useful to know.
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Old 12th October 2003, 06:42 PM   #8
Boban is offline Boban  Canada
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George,
I was making a comment on the part posted above:
>>>
I had hoped to use my Denon 103R (also 0.29mv) straight in with a 900 ohm loading resistor. Sounds like the step up will need to stay.
<<<
I was under impression that it was your comment.
As for transformer issue, I believe that Kevin (K&K) said somewhere that Lundahl transformers sound the best with the highest ratio. But again, I might be mistaken.
I am very happy with my 1:10 settings. I'll post the pictures some day, I have only pictures of my power supply ready (if anyone is interested).

Regards,
Boban
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Old 12th October 2003, 07:36 PM   #9
jam is offline jam  United States
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You could raise the gain of the Pearl by reduceing the value of the j-fet source resistors. If if can get away with it without running into noise issues, it should be better than using a transformer.
Another possibility is duplicating the first stage of the Pearl.

Regards,
Jam
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Old 13th October 2003, 05:09 AM   #10
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So that would be the four 22 ohm resistors? How much can I reduce those by? And would that affect the RIAA EQ in any way?
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