[charlie]

I'm just sending an Ipod Photo off for the Imod at Red Wine. I notice that the voltage output is 1.0 volt. This is lower than most CD players. If you own an Ipod with Imod, do you notice that it's quieter than your CD player?

And I plan to use a passive preamp that is effectively a four way silver switch with four levels of resistance. So four volume settings. I'm using a 50 watt Naim amp and EPOS ES14 speakers. I wonder if this will be loud enough, or will I need to use an active preamp to boost the Ipod's low output. Your thoughts? Does anybody here use a passive preamp with the mod?

Thanks all,

Charlie

[Jampot]

Good plan Charlie!

For sure the output from the Naim at a given volume setting will be less than your cdp. Whether the amp will develop full power given the low output of the imod will depend upon the sensitivity and gain it has. If you have the manual it may well be in there otherwise yoy can probably find it on the Naim website.

For instance, I am looking at specs for an old British amp I just dug out of the attic. It says cd sensitivity 1 volt
tape and tuner 300mV

In this case this amp, fed by the iMod through the cd input,will develop full power if called for. I haven't ever had a problem  with mine either running into a Clari-T with volume control (no pre amp gain) or using a simple switch with volume pot into a Teac AL700P.

If the sensitivity is down on the Naim you just need to turn it up a notch, I don't suppose you ever have it past 12 o'clock anyway, do you?

For what it's worth, when travelling I find the output sufficient to drive a pair of a certain companies 'quite comfort' head phones using a Koss in line volume control (OK, I know it aint audiophile but the noise cancelling is great on a transatlantic flight!).

Enjoy your iMod when you get it back from Vinnie.

Jim

[Jampot]

I forgot to say, since I got my iMod I don't use a cd player

Jim

[jrebman]

For what it's worth, when travelling I find the output sufficient to drive a pair of a certain companies 'quite comfort' head phones using a Koss in line volume control (OK, I know it aint audiophile but the noise cancelling is great on a transatlantic flight!).


Jim,

You can get as good or better noise isolation by using the Ultimate Ears Superfi Pro-5 earphones, especially when used with the foam eartips.

I own a set of these that I bought back in April and they are great.  I use them for monitoring when I'm doing mobile recording, listening on my Oqo computer with a Total Bithead, and very often on my mixing board when at home.  I also have a set of Etymotic ER4s's, which also sound terrific, but at the expense of very low sensitivity -- the mixing board drives them well enough, but any other situation would require a mobile headphone amp for best quality.  You can get a set of the Pro-5's for around $200, and the Etymotics for about $270, and they are truly worth it (at least to my ears, and especially on airplanes.)

Now maybe we need Vinnie to mod a total bithead and build a SLA battery pack for the whole rig -- iPod and Bithead. (thought I'd throw that in there to keep this sort of on-topic .

-- Jim

[TheSloth]

Now maybe we need Vinnie to mod a total bithead and build a SLA battery pack for the whole rig -- iPod and Bithead. (thought I'd throw that in there to keep this sort of on-topic .

-- Jim

Why? They are both already battery powered, and there is no way to send battery power into a Bithead from an external pack unless you wire them directly to the battery terminals. No, you can't do it through the USB port.

[charlie]

Jim, thanks for your response. My Naim amp is not an integrated amp. It doesn't have a volume control. It is just a black box with an on/off switch, two imputs on the back and two speaker connections.

At the moment I have an Ipod plugged into it and I use the Ipod's volume control. With the Imod I'll have to use a preamp. But do I need a preamp to boost the signal or a preamp to reduce the signal? Active? or Passive?

See? I guess none of you are using your Imods with a preamp.

Charlie

[Jampot]

Charlie,

According t the Naim website, the nap 150 and nap 175 (you don't say which) both have 50 watts output and 29db of gain. Unfortunately they don't say what the input sensitivity is, but 29db of gain sounds a lot to me - time for Vinnie to chip in I think

You will need a means of controlling volume but if Vinnie can confirm the gain is adequate, then it can probably be a very simple passive.

Jim,

thanks for the tip about Ultimate Ears,  will have a look before I buy a pair of the 'quiet comforts' for my wife aa

I just acquired a pair of Wharfedale Isodynamic 'phones on ebay and have them dismantled for re-wiring and to replace the old rotted foam earpads. I had a pair of these in the 1970's so it will be interesting to see how they compare. Bit large for travelling though and they use speaker outputs

Good listening all.

Jim

[Vinnie R.]

Hi Charlie,

Welcome to Audiocircle and the RWA forum!

And I plan to use a passive preamp that is effectively a four way silver switch with four levels of resistance. So four volume settings.

If you were to feed an iMod into your Naim using a passive volume attenatuor with a range from minus infinity (mute) to 0dB (no attenuation), and with input impedance in the 10k to 50k range, I'd say you'd be fine with it driving your Naim. 

However, I do not know the attenuation levels of your passive preamp.  Four volume settings doesn't seem like much control, and is the max setting going to still attenuate, or pass thru the input? 

Also, what is the input impedance of your attenuator and does it change with the setting? 

Best regards,

Vinnie

[jrebman]

Now maybe we need Vinnie to mod a total bithead and build a SLA battery pack for the whole rig -- iPod and Bithead. (thought I'd throw that in there to keep this sort of on-topic .

-- Jim

Why? They are both already battery powered, and there is no way to send battery power into a Bithead from an external pack unless you wire them directly to the battery terminals. No, you can't do it through the USB port.

This from theTotal Bithead page on headphone.com:

"BitHead can NOT accept any AC power supply. It can only operate from batteries or
by slaving power via the USB connection to your computer."

If you run the unit connected to a *powered* USB port (most are, but some, especially USB 1.0 and 1.1 passive hubs are not) then the unit will work with the power switch off.  Turning on the power switch will supply battery power to both the DAC and analog circuitry at much lower noise levels.

Why SLA? because it is cleaner power, especially under load, than any other battery chemistry, with old-fashioned carbon zinc batteries coming in second.  Longer life, and greatly reduced portability .

In all honesty though, it was just meant to be fun.  I put the smiley after it hoping it wouldn't be taken seriously.  Sometimes we engineers like to just come up with silly things, especially those of us who spent a good part of our careers working with extreme high-voltage .

-- Jim

[borelek]

I forgot to say, since I got my iMod I don't use a cd player

Jim

Thanks Jim ; It will be my definitive comparative judgement too. And if I remember well, my Naim CD 3.5 is not bad at all, you know.

borelek