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"Matisse" preamp - 12AX7 12AT7

115.131.195.151
Posted on October 31, 2009 at 20:46:25
lordearl
Audiophile

Posts: 10
Location: Australia
Joined: May 29, 2007
 I'm using a Xindak XA3250, which is basically a clone of the Matisse circuit, with two 12AX7 tubes and two 12AT7 tubes. Problem is, the gain is so high that I can hardly turn the volume pot without the system being too loud for some late night listening.

Anyone know the best way to reduce the gain? I figure changing the 12AX7 tubes for another set of 12AT7 tubes would be a possibility....

RE: "Matisse" preamp - 12AX7 12AT7, posted on November 2, 2009 at 08:44:02
lordearl
Audiophile

Posts: 10
Location: Australia
Joined: May 29, 2007
 Okay well, to report back, I tried some preamp combinations for the heck of it and it did not really change much at all!!
Slightly less gain was apparent on the following combination;
Brimar CV4004, GE JAN 12AT7WC
This also sounds great (except for the first time I turned it on there was good deal of buzzing whilst turning the volume dial on low levels - although it went away after a while, any idea what could cause this?).

I will now head down the in-line attenuator path I think....

RE: "Matisse" preamp - 12AX7 12AT7, posted on November 1, 2009 at 13:11:20
JimL
Audiophile

Posts: 3349
Location: New Mexico
Joined: November 24, 2002
 The problem with the Matisse, and I assume the Xindak, is that the designed gain is 30 dB which is about 10 dB higher than the most common line stage gain, which runs about 20 dB. In fact since many audiophiles get away with using a passive "preamp" which essentially has 0 dB gain with the volume control all the way up, even 20 dB is on the high side. 30 dB generally means you have to have your volume control at 9 o'clock or below, where most controls suffer from volume tracking problems, not to mention rapid volume changes with only slight rotations.

As others have pointed out, changing tubes will get you very little in gain reduction, probably only a few dB, and the substitute tube may not be operated at its best which worsens the problem. For example, changing to a 5751 tube (mu of 70) will only get you 3 dB at most. If the design uses overall feedback to set the gain, the gain will not change.

An in-line attenuator is probably a much better solution. The best solution of course is a design with a better gain structure but that is beyond the scope of your question. :-)

RE: "Matisse" preamp - 12AX7 12AT7, posted on November 1, 2009 at 03:12:13
Neff
 You could try 5751 for 12AX7 & 12AU7 for 12AT7. Also carefully remove any cathode bypass capacitors. The sound will be altered of course. If the gain is more reasonable, exchange the 12AU7s for E80CC. The 12AU7 is not very good sounding, but are cheap for test purposes.

The E80CC does draw higher heater current. I doubt the power transformer will be stressed as long as 6 volts or higher is still available at tube sockets with the E80CC.

RE: "Matisse" preamp - ?E80CC, posted on November 1, 2009 at 03:43:10
andy evans
Audiophile

Posts: 998
Joined: October 20, 2000
 I agree the E80CC is a much better choice, but it's taller! Found that out when subbing it in a CJ Preamp. The sound was much improved but the top wouldn't go on! Don't know the Matisse - tubes may be out in the open. The ECC99 is another option. Higher heater current.

andy

RE: "Matisse" preamp - ?E80CC, posted on November 2, 2009 at 08:13:32
Cleantimestream
Audiophile

Posts: 1516
Location: Kentucky
Joined: June 30, 2005
 Yes I found out the hard way .................sounded so good with those Mullard 6072's [E180CC] I toyed with the idea of drilling holes to accommodate.................I did powder coat the PV 5 chassis. Try 12ay7's.......that was the compromise I ended up with for 5965 position.........also, seems the 5965's turn south rather quickly despite testing fine............. I will never figure this hobby out. [smile]
"The Sound of One Hand Clapping is Crashing by Design" HKM
It takes more, posted on November 1, 2009 at 01:00:56
Frihed89
Audiophile

Posts: 8441
Location: Copenhagen
Joined: March 21, 2005
 Your amps may also be very sensitive, which is often the heart of the problem, which could be compounded by high gain from your CD player. In the "old" days, I think CD players put out around a volt. Now 3V is not uncommon. Connect your CDP direct to your amp. How's the gain?

Attenuation kills the sound and robs it of dynamics. It sounds like inverse compression (if there is such a thing). Ultimately, you have to go into the gain circuit and change that. Some mfrs. make it easier than others (for example deHavilland makes it easier on their UV2).

Can a tube change it? It's never worked for me. Be sure you know the electrical differences in the tubes and how they match up with the voltage and current your preamp delivers.
"What did the Romans ever do for us?"
RE: It takes more, posted on November 1, 2009 at 02:51:41
lordearl
Audiophile

Posts: 10
Location: Australia
Joined: May 29, 2007
 yeah my cdp is 2vrms, i think rca attenuation is the better option of a poor set of alternatives! looking through previous posts on many different forums, it seems like a problem that arises far too often -- why are cd players being produced with such high volume output levels?

I think I'll get some Rothwell rca in-line attenuators and then upgrade the stock tubes -- hopefully the improved tube sound + sonic degradation of the attenuators will cancel one another out, but the ability to listen at reasonable volume levels will remain!

Good choice I think........., posted on November 1, 2009 at 11:20:37
Chuck Y
Audiophile

Posts: 3880
Joined: August 31, 2001
 By adding the attenuators you will effectively ruduce the gain and hardly notice any degredation in sound. By pursuing alternative tubes to get the same gain reduction AND get a satisfactory sound would probably consume a lot of time, expense, and frustration. Good luck..........

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