Hi there... I recently purchased a used Rachael for my system, which replaced a 300b integrated amp (10 watts per channel).  I jumped at the chance to buy the Rachael because I have long wanted a Decware amp.  I have it hooked up to my Rega Planar 6 with Ania cartridge, a Darlington Labs MP-7 and SU-7 phono preamp and step up transformer, and use Zu DW6 speakers.

I have a relatively small listening space that is about 12X12, though part of a larger room.  

I have been very impressed with the level of detail from the Rachael compared to my prior amp.

The only issue -- to the extent it is one -- is the difference in power.  I pretty much have to max the volume out (from 3 o'clock to max) on the dial to get it to the volume I like to listen at.  I still need to sit with it some more but I was wondering what people would recommend in terms of being able to boost out a little bit more power -- I imagine a preamp like the CSP3 would solve that "issue."  Can anyone recommend another preamp for this setup?

Thanks!

Alan,

In my experience unless your phono pre is putting out less than the Rachel's optimal input voltage, you will not get more "power" from a preamp. I don't know your phono pre setup, and maybe you are not getting enough voltage to the Rachel, being able to turn the Rachel up to full power, guessing without distortion at all up on the volume pot??? The current version of the Rachel is listed as reaching full output power with a 1.2 volt input.

"Circuit type Single ended Class A Triode

Power output 5.8 watts RMS into 8 ohms

Input voltage 1.2 volts for full output"

So, if your setup provides that voltage or more, adding a CSP3 will give your its sonic flavor, and with gain tuning between the Rachel and CSP3 you can tune the tonal balance, density, weight, dynamics, lucidity, etc... This can give the impression of the little more power, but I am thinking the Rachel's output power will not increase if you are already feeding it 1.2 volts or more...that is unless this spec has changed since your Rachel model???

Hi Alan. The previous generation of Rachael or the SE34I.5 requires 2.5V for maximum output.

Your phone pre and step up dip switches should be adjusted depending on the output of your MC cartridge. I'd check the manufacturer website for instructions on how to best set the gain for your specific cartridge output.

For example, if the switches are set for a moving magnet cartridge your volume will be very limited.

HK

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Yes. I did some quick googling and it looks like both the MP-7 and SU-7 have adjustable gain. I would do some research on the dip switches and how to increase the gain.

Good points TD.

Alternately, if you find out about adjusting the dip switches anyway, and at the same time find out what voltage the phono pre setup is putting out stock, this could help answer it. If it is say, 2 volts, and you can open your Rachel volume to full without any subtle distortions on hot transients, guessing your Rachel is likely optimal at the 2.5 input voltage. In which case, you may be close to full volume now and not know it. As CAJames suggested, full volume on the pots is not necessarily an issue, but in this case it does not tell the whole story necessarily either.

So in one sense... if you can get to listening levels that are high enough volume as-is, without distortions, then you are probably fine as-is. But if you want to find out for sure what is the max volume available in your setup, this is why I suggested that if you can increase voltage from the phono-pre setup without issues to a point where you can hear subtle distortions at higher Rachel volume pot levels, you will know the amp is putting out all it can. Though specs can definitely be useful, I always find that finally experiments make it real and teach me more.

Quote:


This is point I missed. A 72 dB phono stage (which is typically the max) would give you an output of about 1.4V, which would max out the 1.5V Racheal but leave you wanting more if you had the 2.5V version. I don't know for sure how much gain you can squeeze out of your SUT and phono pre, but if you have the 2.5V Racheal you may need an actual preamp.

Alan,

I owned an SE34i.2+, which was a forerunner of the Rachael, and ran it into ZU Druids, which are very similar to your DW6s. Even with a preamp, I found the 6W/channel wasn't really enough to get those 10" FRDs moving. I got a Torii MK IV (25W/ch) which was a much better match and drove them well, still with a preamp.

All the above posters are correct about making sure you're feeding the Rachael enough voltage, but I guess my advice would be to borrow a preamp if you can and see whether the Rachael will drive the DW6s to your satisfaction under any circumstances. You may be more satisfied finding an amp with more power.

Thanks for all the insights.

In emailing with the owner of Darlington Labs, he believes that the Rachael has a very low input sensitivity at 2.5 v and that a line preamp (of +12 db) is needed.  Alternatively, he said that I might be able to turn the gain up on the step up transformer beyond what is needed for the cartridge and make up the gain that way.  

A few questions, as this is somewhat new territory for me:

1. Is a line preamp the same as a regular preamp?  The ones I have seen seem more limited -- i.e. like the ZSTAGE.  If I need to add one to my system, I'd like it to be as transparent as possible.  

2. Other than the ZSTAGE, can anyone recommend another one?  I've seen some recommendations for the Mapletree Line 2CRM.

3. Would switching my phono stage to something like the ZP3 zen triode phono stage provide the right amount of power for the Rachael?

In the end, I may just keep it as is but I want to understand my options.  Thanks!

Alan,

A line preamp simply does not have a built in phono preamp. So you need a separate phone preamp, which you have.

The ZStage is not a preamp. I suggest if you consider a new or used preamp, check out the Decware CSP3. It's a great match for Rachael and provides a lot of flexibility and plenty of adjustable  gain.

Switching your phono preamp is not the best solution in your case, given the Rachael output voltage. At best you'll marginally get modest gain and likely will introduce some noise/distortion by boosting the the MC gain too much.

The Decware ZP3 is designed for high output moving magnet (MM) cartridges so swapping this for your current phone preamp will not solve your volume issue.

Best course IMHO add a good tube line preamp like the CSP3. There are a lot of upgrade options available as well. The 25th Anniversary modifications are highly recommended.

HK

Alan, did you look into the dip switches on the SU-7? Before adding any other components, I would play with the settings first.

From the Darlington FAQ https://www.darlingtonlabs.com/support:
Currently we ship units set to 220 ohms and 23dB gain (for the SU-7).

Onto the Aria page: https://www.rega.co.uk/products/ania
LOAD SETTINGS FOR ADJUSTABLE MC STAGES
Impedance
100 Ω
Capacitance
1000 pF
Gain Setting
High (‘On’ position for Rega phono stages)

I would open the SU-7 up and switch from 220 to 100 for loading. Set the gain to 23db. Take a test drive and see if you hear an improvement. You can play with the loading/gain to find a sweet spot.