RPA-1 man
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Post by RPA-1 man on Mar 14, 2010 17:54:57 GMT -5
I'm considering experimenting with passive pre's and need to know the output impedance of the ERC-1. This info is not available in the owners manual.
Thanks.
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jlafrenz
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Post by jlafrenz on Mar 14, 2010 18:33:22 GMT -5
Not sure what the impedance of the unit is, but it will work with a passive preamp. I just went passive myself and the ERC-1 has plenty of output voltage for the amps.
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RPA-1 man
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Post by RPA-1 man on Mar 14, 2010 18:41:36 GMT -5
What passive are you using?
How do you like the sound?
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jlafrenz
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Post by jlafrenz on Mar 14, 2010 19:35:40 GMT -5
I went with the Goldpoint SA4. I really like the sound with the passive. It is cleaner and more open on the top end.
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Post by vincedog3 on Mar 16, 2010 15:18:29 GMT -5
With the high voltage peak output of 7 volts on the ERC-1 ;D , I think you will be in good shape running a passive preamp.
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RPA-1 man
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Post by RPA-1 man on Mar 16, 2010 17:49:41 GMT -5
Thanks guys. It should be fun experimenting.
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jlafrenz
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Post by jlafrenz on Mar 16, 2010 23:34:03 GMT -5
Thanks guys. It should be fun experimenting. Keep us posted on what you end up getting what your results are. I am curious as passive is a new venture for me too!
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RPA-1 man
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Post by RPA-1 man on Mar 20, 2010 10:49:16 GMT -5
Well, with summer around the corner and many projects to think about I decided to make take my adventure into passive pre's the DIY route. I dug out a parts preamp I had stored in the closet. I realize it won't be as good as a Goldpoint or other high quality passive but it will give me the many inputs/outputs I like plus a built in Phono stage. Gotta have that. It will also help me to identify whether my sources will work with a passive pre. The only time I need to power it on is when I'm spinning vinyl. Attached is an image for you to critique.
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jlafrenz
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Post by jlafrenz on Mar 20, 2010 10:55:07 GMT -5
If you want to test weather your components will work with a passive, you can build a volume control that will tell you. All you need is a volume pot from Rat Shack and some basic soldering skills. Here is the diagram you will need. www.goldpt.com/info.htmlAnd here is the part you will need. www.radioshack.com/product/index.jsp?productId=2062359The guy at Goldpoint told me that the Radio Shack unit is actually quite good. So if you like it, you may consider doing a DIY project with it.
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RPA-1 man
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Post by RPA-1 man on Mar 20, 2010 13:38:52 GMT -5
Thanks for the link. I've previously checked out the info link but decided that using the preamp I already had would give me the complete package including housing, selector and volume control. It was just a matter of removing a few parts and redirecting the signal from the volume control wiper directly to the output jacks. It only took a short time to complete.
I've been listening to it with the ERC-1 cdp, tuner and phono with the RPA-1 amplifier and so far so good. I haven't tried the cassette deck yet. Removing some switches and eliminating the Balance and Stereo/Mono control may yield even better results but so far it gets a thumbs up.
The sound is more dynamic. Subtle sounds/notes are easier to hear. They don't seem to be hidden in the background so much. There seems to be no low or high end roll-off.
So my initial impression is that the passive is definitely giving me all of the music plus. I'm feeling confident that this could work out very well.
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jlafrenz
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Post by jlafrenz on Mar 20, 2010 14:11:34 GMT -5
Seems like you have had some of the same results as me. I seemed to get more clarity, detail and a more open top end with a passive. The bass is about the same for output, but it is certainly more distinguished and has a more true to life sound.
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RPA-1 man
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Post by RPA-1 man on Mar 20, 2010 15:15:52 GMT -5
I forgot to mention that my interconnects are only .5 meter in length from my sources and 1 meter from pre to amp.
I just finished listening to Diana Krall "Live In Paris" and the violins are so nice with this diy passive. There is definitely more balance and separation of instruments and vocals. I'm loving it.
Before I spend $500 on a passive I may have to purchase a nice Alps pot or step attenuator and try connecting the pot/attenuator in a "shunt to ground" configuration rather than have the signal passing directly through the pot/attenuator.
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jlafrenz
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Post by jlafrenz on Mar 20, 2010 15:27:28 GMT -5
I forgot to mention that my interconnects are only .5 meter in length from my sources and 1 meter to the amp. Based on what everyone has stated about using a passive preamp, I have the worst setup interconnect situation. From the DAC they are 1 meter and from the passive they are 16 feet. Doesn't seem to pose any real issues and I think it sounds great. The BJC LC-1 are very low capacitance, so that is probably helping.
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Post by RPA-1 man on Mar 20, 2010 15:29:28 GMT -5
I'm using Straightwire Chorus interconnects. Can't find any capacitance specs on them.
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jlafrenz
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Post by jlafrenz on Mar 20, 2010 15:52:56 GMT -5
I forgot to mention that my interconnects are only .5 meter in length from my sources and 1 meter from pre to amp. I just finished listening to Diana Krall "Live In Paris" and the violins are so nice with this diy passive. There is definitely more balance and separation of instruments and vocals. I'm loving it. Before I spend $500 on a passive I may have to purchase a nice Alps pot or step attenuator and try connecting the pot/attenuator in a "shunt to ground" configuration rather than have the signal passing directly through the pot/attenuator. I would seriously give that Rat Shack volume pot a chance. I made a passive volume control with it using el cheapo interconnects and really liked the sound. I really considered doing a DIY passive, but couldn't find any good plans or info on the selector side. Had I found a very clear wiring diagram for a source selector, I probably would have gone DIY. As far as the cables and the capacitance, as short as yours are, I don't think it is really too relevant.
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RPA-1 man
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Post by RPA-1 man on Mar 20, 2010 16:53:44 GMT -5
My only problem with the Radio shack pot is the 100k rating. Goldpoint info states that the attenuator should have a rating that matches the input Z of the unit it is driving. It can be lower but should not be higher. In this case the RPA-1 has an input Z of 47K. The impedance of the pot I'm using is 25k. With the Balance control being in parallel it actually measures about 10K according to my VOM. My understanding is that a 100k attenuator works great with tube gear due the their higher input Z.
Please correct me if I'm wrong because I'm new to passives as well.
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jlafrenz
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Post by jlafrenz on Mar 20, 2010 17:22:23 GMT -5
My only problem with the Radio shack pot is the 100k rating. Goldpoint info states that the attenuator should have a rating that matches the input Z of the unit it is driving. It can be lower but should not be higher. In this case the RPA-1 has an input Z of 47K. The impedance of the pot I'm using is 25k. With the Balance control being in parallel it actually measures about 10K according to my VOM. My understanding is that a 100k attenuator works great with tube gear due the their higher input Z. Please correct me if I'm wrong because I'm new to passives as well. I did some reading on what resistance the volume pot should be as well. I think you are correct in stating that it is supposed to be lower. However, I would assume that the X series has a similar input impedance. It seemed to work for me. The Goldpoint is a bit more open on the top end. It just seems strange because I read a lot about it and my setup isn't ideal for a passive or that high of a resistor, but for what ever reason, it did work and my ears liked it. The Goldpoint unit I have is a 25K though. Thought the Rat Shack might be a good option for only a few bucks.
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RPA-1 man
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Post by RPA-1 man on Mar 20, 2010 17:30:14 GMT -5
The Rat Shack pot is an option but I can't imagine, from what you and I have read that there would be any advantage jumping up from 20K to 100K.
My other amp, an NAD 2200PE, has an input Z of 25K so I think going to 100K would not be such a good move.
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jlafrenz
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Post by jlafrenz on Mar 20, 2010 20:46:34 GMT -5
The Rat Shack pot is an option but I can't imagine, from what you and I have read that there would be any advantage jumping up from 20K to 100K. My other amp, an NAD 2200PE, has an input Z of 25K so I think going to 100K would not be such a good move. The only advantage is that it is less than $4 compared to the others that go into the mid hundred range.
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RPA-1 man
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Post by RPA-1 man on Mar 20, 2010 20:59:02 GMT -5
I've been listening for a good part of the day now and I have to say that I'm singing the praises of passive pre's. I've read about people stating they lost dynamics in their systems with a passive pre. I have not experienced this at all. In fact, the dynamics are noticeably improved. I'm very excited about what I'm hearing. I have a feeling I'll be in my listening chair most of the day tomorrow. Is that a bad thing? Right now I don't think so.
I see that you have a Music Hall turntable. What are you using for a phono pre? I'm also curious what the sensitivity rating of your speakers are?
I just checked the owners manual for the input Z of the XPA series and they range from 20k to 23.5k for unbalanced connections and 18k to 20K for balanced connections.
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