How long can my Turntable interconnects be?

trav0810

Or I guess the more accurate question is; How long can the interconnects be from my Bottlehead Seduction preamp to my Linestage preamp?

mhardy6647

depends upon the output impedance of the Seduction (which I don't know, even though I have one). One to two meters would be no problem -- EDIT -- the issue with the Seduction (and its replacement the Reduction) is that it has no output stage per se (e.g., a cathode follower), so it's probably a little more sensitive to the I/C load than would be a preamp with an output/buffer stage.

I say this mostly based on the comments on Bottlehead's Reduction, which isn't all that different in terms of its basic topology than the Seduction.

https://bottlehead.com/reduction-phono-preamplifier-kit/

The phono preamp has a gain of approximately 36 dB at 1 kHz and is intended for use with phono cartridges of 2.5mV and higher output, with 5mV output being the design center. Higher than 5mV output is certainly fine, and one may also use lower output cartridges with a suitable step up device. Input impedance is 47.5K ohms, input capacitance is 50pF. Remember that your phono cable’s capacitance will add to this figure and increase your cartridge’s capacitive load somewhat. Frequency response exhibits +/- 0.3dB RIAA curve accuracy. The Reduction is designed to operate into line stages with 50K or higher input impedance through interconnects of 1M or shorter length. At 4.5mV input THD is 0.12%, THD+noise is 0.6%

FWIW -- I think 2 meters is fine, empirically

Oh, the other "issue" with the Seduction/Reduction is the relatively low gain (see the quote above pertaining to the Reduction; I think that the Seduction is more or less identical in terms of gain -- I could check if someone really wanted me to! ).

mhardy6647

By the way -- and you probably know this already (but just in case) -- the output signal from a phono cartridge is much more delicate than the output of the phono preamp! The interconnect's capacitance must be low and/or the length of the interconnect should be short (as short as possible) to ensure no degradation (mostly in the form of treble roll-off).

The line-level output of the phono preamp is considerably more robust (although not arbitrarily robust, as I tried to say my earlier post!).

trav0810

I knew that I would want the cables between the TT and the phono pre to be as short as possible, but I'm using the standard factory installed cable on the Rega, so I don't have much choice on that. For the layout of my room and available shelves/stands, my TT and phone pre will be about 8 from my Linestage

mhardy6647

Is that 8 feet? Well -- try the preamp with shorter cables vs. long-enough ones & see 1) you hear a difference and 2) if you do, does it bother you?

Bottlehead would say 8 feet is too long -- my knee-jerk assessment would be that it's borderline.

I would say if you're lookin' at 8 feet - either make your own I/Cs or get some made to the right length (if you go the store-bought route). I.e., don't default to 3 meters (nearly 10 feet) if you need eight.

Cheap in the long run to do it as 'right' as possible.

[Deleted User]

If you make your own cables use RG62u for the lowest capacitance per foot.

trav0810

I'll certainly make my own. And I don't know if this makes any difference or not, but they are going to be converted to XLR at the Linestage

trav0810

Ok, thanks for the heads up.

mhardy6647

Ken can probably speak to the net impact of that -- I can't, I'm afraid.

I'm an unbalanced kinda guy, mostly -- except when necessary (i.e., pro-style hardware, like my Otari and a few other bits and pieces here).

tratliff

I would give HeliPilotDoug (Doug) a shout. He is very helpful in cable planning and can give you a recommendation on what would be the best approach.

www.douglasconnection.com

I have not seen him around lately...

mhardy6647

tratliff wrote: »

I would give HeliPilotDoug (Doug) a shout. He is very helpful in cable planning and can give you a recommendation on what would be the best approach.

www.douglasconnection.com

I have not seen him around lately...

It's a good idea and I do believe I've seen him post recently.
I'm sure he's contactable (is that a word?) via his website, regardless.

http://www.douglasconnection.com/Douglas-Connection-Analog-Interconnect-Cables-DCFAIC.htm

trav0810

I do business with Doug frequently. I've already talked to him a little about making me some XLR to RCA's!

mhardy6647

why the heck were you asking us, then?

trav0810

He'll build what I need, but I don't think he is a big Vinyl guy.

txcoastal1

trav0810 wrote: »

He'll build what I need, but I don't think he is a big Vinyl guy.

Doug's old enough to know better

Viking64

Turntables in helicopters cause skipping records.

tratliff

He built my phono cable and I couldn’t be happier. Doesn’t look I have a picture of it on my phone. I will send a pic in the morning when I’m on my pc.

tratliff

Here is the one Doug built me earlier this year.

trav0810

I have ZERO doubt in Doug's build quality. I just wasn't sure if he would know about the cable length I could use, unless he had experience with the particular phono preamp I'm using. That is why I came here. Not to get a cable, but to find out the length I would be able to get away with.

soundfreak1

If it helps, I had a concern about that as where my TT needed to be (10ft away from preamp) researched cables for loss and basically found anything under 20 ft (using really good cable) was irrelevant for all practical intents.