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Cambridge Audio Alva Duo  Moving Coil & Moving Magnet Phono Preamplifier information
Cambridge Audio Alva Duo  Moving Coil & Moving Magnet Phono Preamplifier information
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Old 11th February 2019, 05:55 AM   #1
keilau is offline keilau  United States
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Default Cambridge Audio Alva Duo Moving Coil & Moving Magnet Phono Preamplifier information

I am looking to purchase a moving coil phono preamplifier. The prime candidate is:

Alva Duo - Moving Coil & Moving Magnet Phono Preamplifier | Cambridge Audio

Its predecessor the CP-2 has a good reputation for entry level phono preamp. The Duo is the first Cambridge Audio model with integrated PS. But I only know that the PS is a switching PS and cannot find any other essential technical information such as
  1. Is the input stage discrete or IC?
  2. Is the RIAA curve active or passive?
  3. Any information on the circuit topology?
These questions are important to me. I had the Parasound Zphono for 2 years after I read very positive report on Stereophile. But I never like it much. Same for the NAD PP2.

On the other hand, I like the MC phono stage on Harman Kardon AP2500 and Kenwood C-2. The cartridge is a Dynavector Karat Ruby on a Thorens TD-125II.
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Old 13th February 2019, 09:51 PM   #2
keilau is offline keilau  United States
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Default Vincent PHO-8 MM/MC phono preamp

I am disappointed, but not surprised to see no response to my questions on the Cambridge Audio DUO preamp. After more reading on reviews and user feedback, I am more inclined to the Vincent PHO-8 MM/MC phono preamp. Many users praised its natural, non-analytical sound. The construction quality and a separated PS box are also pluses.

The one drawback of Vincent PHO-8 is that it used no socket for the IC's, making upgrade substitution non-trivia. Hopefully, it is not necessary.

Another option is used Rotel RQ-970BX. The MC stage input is a pair of symmetrical 2SD786R/S followed by a AD744. The output stage is NE5534. All IC are on socket. The AD744 is a very high speed JFET opamp, but has higher noise than OPA627 which is a drop in upgrade. The NE5534 can be replaced by LME49710. An used Rotel is easy to find at very good price.

I have put the Cambridge Audio DUO idea on the shelf. I may get both the Vincent and the Rotel so that I can compare and choose myself.
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Old 14th February 2019, 12:23 PM   #3
craigtone is offline craigtone  United States
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FWIW, I have a modified Rotel RQ-970BX as my backup unit. It is a GREAT sounding phono preamp! I built one for my brother using Burson discrete v5 op-amps and it is 98% of the sound quality of my Pass Pearl 2. If you go the Rotel route, I posted a PDF of the mod article in another thread about the RQ-9780BX.
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Old 15th February 2019, 04:49 PM   #4
keilau is offline keilau  United States
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Quote:
Originally Posted by craigtone View Post
FWIW, I have a modified Rotel RQ-970BX as my backup unit. It is a GREAT sounding phono preamp! I built one for my brother using Burson discrete v5 op-amps and it is 98% of the sound quality of my Pass Pearl 2. If you go the Rotel route, I posted a PDF of the mod article in another thread about the RQ-9780BX.
Thank you for the suggestion. I was mistaken that the RQ-970BX does not use IC socket and I would need to take out the soldering iron.

The original AD744 is a very capable opamp. The OPA627 is very expensive and hard to find. The Burson DOA is even more so. The LME49710 is also out of the market for a while. Need to go back to the drawing board for a practical, cost effective upgrade. One worthwhile upgrade will be changing the power transformer to an toroidal unit. I buy opamp IC from established US parts house only.

Last week, I found a very clean Rotel phono on sale at Audiogon, but did not act fast enough. There are a few on the bay, but the cosmetic condition are not very good.
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Old 15th February 2019, 05:21 PM   #5
craigtone is offline craigtone  United States
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Quote:
Originally Posted by keilau View Post
Thank you for the suggestion. I was mistaken that the RQ-970BX does not use IC socket and I would need to take out the soldering iron.

The original AD744 is a very capable opamp. The OPA627 is very expensive and hard to find. The Burson DOA is even more so. The LME49710 is also out of the market for a while. Need to go back to the drawing board for a practical, cost effective upgrade. One worthwhile upgrade will be changing the power transformer to an toroidal unit. I buy opamp IC from established US parts house only.

Last week, I found a very clean Rotel phono on sale at Audiogon, but did not act fast enough. There are a few on the bay, but the cosmetic condition are not very good.

I have had good luck with the OPA134 in these also. Check out the Burson v5 as the prices have dropped now that the v6 is out. Stay away from the v5i! I tried that and NOT on the same level at all!

I wouldn't bother messing with the power transformer. The preamp uses a regulated supply so nothing to really gain plus the OEM transformer has a shield around it.
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