Looking to Pull the Trigger, but...

[BNAL]

I have been looking to pull the trigger on a new phono pre and with the current deal on the Eros  i'm extremely tempted. The only thing holding me back is I'm running a passive volume control switch with a 10K ebay DACT attenuator. The Eros product page states that at least a 15k input impedance is required.

Does this mean that I should change the attenuator to 15k or higher. The manufacturer of the amp recommends with a passive pre that you should not use a attenuator. The other option could be using a buffer.

Any recommendations would be greatly appreciated.

[johnsonad]

I can't help you Brad but I wanted you to know I bought one too with this sale😊

[galyons]

The manufacturer of the amp recommends with a passive pre that you should not use a attenuator. The other option could be using a buffer.

All a passive pre is is connectors, wire and an attenuator. So, this comment is, to me, confusing.   

The Eros is spec'd for a 0.47uF output cap. Mine shipped with a 1.0uF cap.  The issue is the low frequency fall off.  Calculating Fo at 0.47uF, the Eros output with a 15k next stage input impedance gives you 22.6Hz. That is a bit high.  If you build with the 1.0uf, Fo would be 10.6Hz.  Still high. Where Fo is the crossover frequency, this is the 3dB down point, the signal will be essentially flat at 10 times Fo.

At more typical, at least for tube gear, input impedances, say 50K or 100K, you would have  Fo's of  6.8Hz and 3.4Hz, respectively with a 0.47uF output cap.   PJ may have other reasons for the 15K minimum input impedance, as well.  Check with your amp's manufacturer to see if there are any issues with a passive having 50K or 100K input.

All of that being said, I would jump on the Eros sale.  When built out, it is a marvelous piece of kit. Mine has bested some very well regarded pricey commercial units!

Cheers,
Geary
 

[BNAL]

Geary,

Thanks that makes sense. Now I see why I would need to add a buffer to proved the >15K input and lower output impedance the amp needs.

Arron,

You did recommend the Eros, and I will take your advice and pull the trigger.

I will take the savings and put is towards a buffer.

Thanks,
Brad

[tsingle999]

For another idea you could run the eros into a quickie.
I use a reduction into the quickie and run a separate preamp for other sources.
Quickie is great!

[johnsonad]

Thinking back on it, I've used the Tube Phono (same output impedance I believe via RCA) with a MQ Ingot which has a 10k input and honestly I didn't notice the difference.  This time I used the $150 in savings to upgrade resistors and capacitors in the signal chain. This is my third Eros/Tube Phono variant and should be the last 😊

[BNAL]

I pulled the trigger. I just could not pass on the deal.

[johnsonad]

I hope that you enjoy it as much as I have! This will be the second Eros in my current system (one for tape).

[Paul Birkeland]

The issue is the low frequency fall off. 

There is indeed this issue, but also the issue that whatever you have connected to the output of the Eros will load down the 6922 output stage.   We have found that the performance of this stage seems to hold up reasonably well down to a 15K load, but going lower risks higher distortion operation. 

On your 10K control, you can add a pair of 5K resistors between the output of the selector switch and the input of the 10K attenuator to bump the impedance up a little bit.

Adding a Quickie will also completely remedy the issue. 

Just out of curiosity, what's the input impedance of your amplifier?

-PB

[BNAL]

Just out of curiosity, what's the input impedance of your amplifier?

I believe it is 25k.

I going to build a buffer and use a 100k eBay DACT attenuator..

[xcortes]

I use a tube repro (three of them actually) from the unbalanced output which is a circuit identical to the eros iirc. My preamp is a pair of Magnequest silver 10k:10k inputs (Mexico series, of course) feeding a 10k pot and the sound is superb.

[BNAL]

I use a tube repro (three of them actually) from the unbalanced output which is a circuit identical to the eros iirc. My preamp is a pair of Magnequest silver 10k:10k inputs (Mexico series, of course) feeding a 10k pot and the sound is superb.

Xavier,

Aaron said the same thing, so I feel confident that if I just use the passive it will spit good. Thank you for your experience, it helps.

[johnsonad]

Xavier and I wouldn't steer your wrong and we are using the same speakers. I just added subs to mine. Give it a try 😊