• Registered: 2023-07-04
  • Posts: 10

Topic: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

I know this question is asked 1 million times before but just double checking again before I buy the speaker and the AMP.

I am planning to buy IOM 500 Stereo (NCx500) and connect with KEF r3. My setup will be more or less: I will connect a streamer and TV to ADI-2 DAC, then to IOM 500 then to KEF r3 and will use the DAC with my HD800s.

My question is: Will I be able to control the volume through DAC with Auto Ref and not make anything explode? Also I hope steps when I increase the volume will be small enough since the AMP is quite powerful. I want to buy the amp as I learned that it is a very very good paring and the price is good.

Thank you

2 Reply by ramses (edited by ramses 2023-07-04 12:56:18)

  • ramses
  • DAW Mastermind
  • Offline
  • From: UTC+1
  • Registered: 2012-10-14
  • Posts: 13,184

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

If there is no other possibility at the amp itself to lower the sensitivity of the analog inputs,
then you will most likely need an attenuator, see also this thread.

https://forum.rme-audio.de/viewtopic.php?id=25399

Which kind of attenuator depends on the amps inputs, I think you can check it out yourself.

You might also need the most silent reference level as fix reference level, depending on what volume remains even after using an attenuator. +1 dBu. It's also possible to use the RCA output (unbalanced) to have a 6dB lower output signal compared to XLR (balanced).

BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14
  • Registered: 2023-07-04
  • Posts: 10

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

I am actually planning to use XLR and not RCA so I assume I need to use attenuators.

The AMP page is here: https://internetofmusic.nl/product/iom-500-stereo/ just in case i missed something about analog input sensitivity. All I can understand is that it can handle 4v-12v and from DAC manual XLR voltages are within that range. 

What is still confusing for me (because I have no where to try it) when I use AutoRef and control the volume only from the DAC (Streamer and TV will have a fixed volume) how will that work. I am just trying to avoind being in position where the volume will be always to high or if there is a pop-sound e.g. when you connect/disconnect something to damage something.

4 Reply by KaiS (edited by KaiS 2023-07-04 17:47:05)

  • KaiS
  • DAW Mastermind
  • Offline
  • From: Germany
  • Registered: 2020-02-05
  • Posts: 3,525

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

lumzhaveli wrote:

I am actually planning to use XLR and not RCA so I assume I need to use attenuators.

The AMP page is here: https://internetofmusic.nl/product/iom-500-stereo/ just in case i missed something about analog input sensitivity. All I can understand is that it can handle 4v-12v and from DAC manual XLR voltages are within that range. 

What is still confusing for me (because I have no where to try it) when I use AutoRef and control the volume only from the DAC (Streamer and TV will have a fixed volume) how will that work. I am just trying to avoind being in position where the volume will be always to high or if there is a pop-sound e.g. when you connect/disconnect something to damage something.

If you get the IOM 500 amp with the:
“connection board”, not the “custom buffer-board”,
you might save the use of external attenuators (and some money).

The “custom buffer-board” adds unnecessary 14.6 dB gain that is contra-indicated for use with a serious preamp like ADI-2.
The NCx500 module’s own 11.5 dB gain is a perfect match with ADI-2.

Go for the RCA interconnects in the first place (the +13 dBu output matches best for home use), switch on Auto Ref Level, and ADI-2 cares for the rest - that’s all!


13dBu output + 4.5dB ADI-2 headroom + 11.5dB NCxCore gain = 29dBu NCxCore output, = 60 Watt @ 8 Ohm speaker –> nothing can “explode” smile

KaiS's Website

5 Reply by emeissl (edited by emeissl 2023-07-04 18:08:35)

  • From: living in Cologne
  • Registered: 2022-01-14
  • Posts: 41

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

Kai, as I read it, NCx500 module has its own input buffer, which adds up to 26.5 db of gain. By using the custom IOM buffer this own input buffer is being bridged, or the IOM buffer is connected directly to the class D amp. Don't know. In your proposed case the ADI would need to be connected directly to the class D amp as well.
I consider this a little but DIY.

Cheers, Ernst

ADI-2 PRO FS R BE / ADI-2 DAC FS / some old multibit treasuers ;-)

6 Reply by KaiS (edited by KaiS 2023-07-04 22:11:32)

  • KaiS
  • DAW Mastermind
  • Offline
  • From: Germany
  • Registered: 2020-02-05
  • Posts: 3,525

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

emeissl wrote:

Kai, as I read it, NCx500 module has its own input buffer, which adds up to 26.5 db of gain. By using the custom IOM buffer this own input buffer is being bridged, or the IOM buffer is connected directly to the class D amp. Don't know. In your proposed case the ADI would need to be connected directly to the class D amp as well.
I consider this a little but DIY.

You’re right, the input buffer needs to be bypassed, else you get 26 dB of gain instead 11.5 dB.

I’d ask the amp manufacturer for such a mod.
Else passive attenuators are suggested.

KaiS's Website

7 Reply by lumzhaveli (edited by lumzhaveli 2023-07-05 21:01:06)

  • Registered: 2023-07-04
  • Posts: 10

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

Thanks for clarification. I will ask the manufacturer if they can do such thing for me or I will just buy 2 passive attenuators, preferably I would go with XLR in that case (get -40db attenuators).

In case of going for custom buffer-board what would be the ideal negative gain.

EDIT: The manufacturer replied that with buffer board the gain can be chanced easily. The next step is to determine what would be the best setting for me in this case (preferably XLR as it tents to produce better quality as I manage to understand) so I will set the gain settings correctly now. Also when I get everything hopefully by the end of the month I would happily share the results back in the forum

8 Reply by KaiS (edited by KaiS 2023-07-05 20:32:40)

  • KaiS
  • DAW Mastermind
  • Offline
  • From: Germany
  • Registered: 2020-02-05
  • Posts: 3,525

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

lumzhaveli wrote:

...The manufacturer replied that with buffer board the gain can be chance easily. The next step is to determine what would be the best setting for me in this case (preferably XLR as it tents to produce better quality as I manage to understand) so I will set the gain settings correctly now. Also when I get everything hopefully by the end of the month I would happily share the results back in the forum

The NCx500 module’s basic gain of 14.5 dB is the best fit to ADI-2 DAC.
I’d ask the manufacturer for this variant, buffer gain = 0 dB.

I calculated this scenario above, with RCA interconnects.


Using ADI-2’s XLR outs you get 6 dB more level, resulting in 4 times the max. power, hence ca. 240 W into your 8 Ohm speakers.
This is about their upper limit, so short term they should stand it in case of an “accident” - which is unlikely to happen anyway.

Usually you wouldn’t run ADI-2 full up in any case, and switching sources isn’t problematic too, as various native digital sources don’t differ that much.

KaiS's Website

  • Registered: 2023-07-04
  • Posts: 10

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

Before I sent the order I just want to wrap this around my head and double check. There are quite a few new things I learned for audio and how amplification works along this journey thanks to posts here.

So, as far as I understand the gain of the NCx500 in buffered mode is 26.8dB.

The gain of the IOM buffer board can be set to 14.6dB or 17.6dB. With a gain of 11.5dB of the NCx500 module in unbuffered mode the total voltage gain of the amplifier is delectable between 26.1dB & 29.1dB. Thanks to the manufacturer, he can change the gain of the IOM buffer board in something else you want. I will ask him to set the gain in IOM buffer board to 0 for RCA as suggested by @KaiS

So my last question.

I will have my DAC connected with 30-50cm cables but I wanted to use XLR because I read that the sound should be better but in theory with those with short cables the sound should be the same and no EMI should occur. In case I want to really go with XLR instead of RCA I should set the gain in buffer board = -6 dB?


Also for running ADI-2 I am planning to use it with Toslink for TV and from a streamer with USB so switching sources shouldn't be an issue even when the volume is high or if the power is super high like 240w with 8 Ohm.

10 Reply by KaiS (edited by KaiS 2023-07-06 12:23:43)

  • KaiS
  • DAW Mastermind
  • Offline
  • From: Germany
  • Registered: 2020-02-05
  • Posts: 3,525

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

I‘d go for 0 dB gain, both RCA and XLR, on the buffers.

XLR / balanced is less prone to interference, and anyway with the well fitting 14.5 dB total poweramp gain audible noise is very unlikely.
So, ADI-2 DAC‘s 6 dB extra output level on XLR doesn‘t hurt, just gives you a 2nd option.

KaiS's Website

  • Registered: 2023-07-04
  • Posts: 10

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

Thanks for the answer.

I will go and order the AMP with buffer board with 0dB gain and will use RCA. Also I will try to find some better cables RCA cables in Netherlands. Currently I have a pair but they are few euros per pair that I use with my Schiit stack.

Any cable suggestion is welcomed.

12 Reply by emeissl (edited by emeissl 2023-07-06 13:59:02)

  • From: living in Cologne
  • Registered: 2022-01-14
  • Posts: 41

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

Cordial from Thomann is a good choice in my eyes.Good enough, reliable and reasonable cheap.

Cheers, Ernst

ADI-2 PRO FS R BE / ADI-2 DAC FS / some old multibit treasuers ;-)

13 Reply by lumzhaveli (edited by lumzhaveli 2023-07-10 08:35:07)

  • Registered: 2023-07-04
  • Posts: 10

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

I will order the AMP with buffer board gain set to 0dB and NCx500 + ADE-2 (0dB +11.5dB + 14.5dB = 26.0dB). I need to wait around 2 weeks for it to be assembled and shipped (next week the engineer working on my AMP will be on holidays). I will write back how the results are and hopefully it will help with similar situation.

14 Reply by lumzhaveli (edited by lumzhaveli 2023-07-24 22:27:23)

  • Registered: 2023-07-04
  • Posts: 10

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

I got the AMP last Friday.

So far I am very please with it: the sound is really good, nice base, plenty of power, not as bright as i though from reading the forums, pretty fast IMO (I will write more details next week as I will have more friends to come and listen and try new cabled and other DACs, and I won't have a biased opinion).

I tend to not keep the volume >20dB (with ref level -5dB)as its pretty loud for my apartment in Amsterdam and I don't want my neighbors to knock on my door yet. Setting gain in buffer board to 0dB was the right thing to do. Thanks to everyone for advising me to do that.

The AMP is set to use NCx500 as-is so the buffer board just has the gain set to 0dB and doesn't use any om-amp.

This is my current stack in case others are wondering: Wiim pro -> Toslink (bit perfect) -> ADI-2 DAC FS -> Cheap RCA for now, XLR Custom cables later -> IOM 500 series AMP -> QED  XT40i -> Kef R3

  • KaiS
  • DAW Mastermind
  • Offline
  • From: Germany
  • Registered: 2020-02-05
  • Posts: 3,525

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

lumzhaveli wrote:

Setting gain in buffer board to 0dB was the right thing to do. Thanks to everyone for advising me to do that.

The AMP is set to use NCx500 as-is so the buffer board just has the gain set to 0dB and doesn't use any om-amp.

Great it made a perfect fit!

KaiS's Website

  • Registered: 2023-07-04
  • Posts: 10

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

KaiS wrote:
lumzhaveli wrote:

Setting gain in buffer board to 0dB was the right thing to do. Thanks to everyone for advising me to do that.

The AMP is set to use NCx500 as-is so the buffer board just has the gain set to 0dB and doesn't use any om-amp.

Great it made a perfect fit!

Yes, so far its its looking good. I forgot to mention that my typical listening volume with Auto Ref Level is round 60-45dBr. Going above 40dBr seems too loud for my apartment.

I hope this will help others choose and set the AMP gains properly when pairing with ADI-2.

17 Reply by KaiS (edited by KaiS 2023-07-25 00:11:53)

  • KaiS
  • DAW Mastermind
  • Offline
  • From: Germany
  • Registered: 2020-02-05
  • Posts: 3,525

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

lumzhaveli wrote:
KaiS wrote:
lumzhaveli wrote:

Setting gain in buffer board to 0dB was the right thing to do. Thanks to everyone for advising me to do that.

The AMP is set to use NCx500 as-is so the buffer board just has the gain set to 0dB and doesn't use any om-amp.

Great it made a perfect fit!

Yes, so far its its looking good. I forgot to mention that my typical listening volume with Auto Ref Level is round 60-45dBr. Going above 40dBr seems too loud for my apartment.

I hope this will help others choose and set the AMP gains properly when pairing with ADI-2.

Would mean you could still use some -20 dB attenuators:)
Maybe get some with the XLR cables.

Good you have the lowest available gain in the amp!

KaiS's Website

  • Registered: 2023-07-04
  • Posts: 10

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

KaiS wrote:
lumzhaveli wrote:
KaiS wrote:

Great it made a perfect fit!

Yes, so far its its looking good. I forgot to mention that my typical listening volume with Auto Ref Level is round 60-45dBr. Going above 40dBr seems too loud for my apartment.

I hope this will help others choose and set the AMP gains properly when pairing with ADI-2.

Would mean you could still use some -20 dB attenuators:)
Maybe get some with the XLR cables.

Good you have the lowest available gain in the amp!

Do you think its worth going that route?
I was thinking just getting some XLR but I guess that might be too loud, or just stay with RCA but get better ones not monoprice (they are 30cm so i should be fine).

  • Registered: 2023-07-04
  • Posts: 10

Re: Pairing IOM 500 Stereo with ADI-2 DAC as preamp

I went with XLR and -20dB attenuators for now to test. me and my friends auditioning think with the AMP pairing it sounds a bit more open and airy to say.

I might make custom cables with -20dB attenuators when I find some free time.

Again, thanks for all the tips. You made a man very happy XD