Help on upgrading my Tube Preamp

[audioboy69]

Hi,

A friend of mine pass to me a tube preamp ( also passed to him by an old friend ). It is named VAA-L1 Stereo Tube preamp.... anybody familiar with this preamp?? I've search the web and could not find any information on this preamp and who is the manufacturer. I was able to read a thread at audio asylum stating that this is a Kit from China. It is working fine and based on the looks if it, it is a Marantz 7 clone . It uses 12AX7 (3pcs) for the input stage and 5U4 (1pc) for the Rectification. Currently, it is using 12AX7 tubes pulled form a VTL tube preamp and a NOS Svetlana 5U4.

I'm planning to upgrade the components and hopefully it would yield good results. It is my first tube upgrade so i need your opinions/suggestions on how can i improve the sound quality. I am using a Cayin KT88 tube amp and Consonance Ref 2.2 Tube CD player. I listen mostly on vocals, intstruments (guitar / piano ) and a bit of pop. I want the outcome to be more dynamic and more transparent since i'm using all tubes.

Here are my plans:
1. Replace the RCAs to a better quality
2. Simplify the circuit .. remove balance control and bypass SELECTOR switch since i only use 1 source ( connect direct from RCA to Vol pot ).
3. Upgrade Vol pot to ALPS .
4. Upgrade coupling caps to higher quality ones.
5. Upgrade resistors to higher quality ones.
6. Change internal wirings to silver plated wires

Questions:
1. For item number 4, what cap do you recommend . Auricap, hovland, Jensen .. Mundorf ??
2. For item number 5, what resistors do you recommend .. Holco, Riken , Kiwame ??

Here are some pictures of the preamp.

VAA-L1 Top


PCB Lay-out:


Preamp & PSU PCB:


Preamp PCB:


Marantz 7 Clone Schematic:

[Giaime]

I think that the most serious upgrade you can make (forget about those silly resistors, capacitor and wiring upgrades) is to remove the PCB and save only sockets, transformers, chassis and the power supply, and make a nicer and more modern preamp out of it.

Do a search for the Aikido linestage, or SY's Heretical. Also some pretty preamps on my website, if you want to take a look.

[poobah]

Yes,

Save your money... The 12ax7 in the 3rd stage is a poor choice for a CF circuit in this application.

What is your 1 source for music? If it is the CD player... you may need no preamp at all... this is the best possible sound.

[Giaime]

Originally posted by poobah

What is your 1 source for music? If it is the CD player... you may need no preamp at all... this is the best possible sound.

Dear Poobah,

I totally agree with you. All a CD player needs is a volume pot. Then, if you wish, integrate this volume control in a phono preamp and you're done. That's pretty much what I'm doing those days

Why did Marantz design such a bad preamp? I believe that hi-fi was something different than now...

[poobah]

Well the design is not poor. But it has high input impedance; invites noise of many types. The output impedance is also high.

The idea of "passive preamps" is nuts; an oxymoron.

And if you have a high level source, like a CD player, the BEST preamp will be a piece of wire (copper).

Now, if you want tone controls... and I think those are good... that is a different story.

[audioboy69]

Giame , Poobah :

Thank you for your response . I am using a Tube CD player as a source feeding an Integrated tube amp. This amp can be used as a power amp alone and it utilizes 2X 6SL7 and 2X 6SN7 on its preamp stage and 4X KT88 as power tubes. Do i really need a preamp based on my current setup ? What can i gain in using a preamp ... better detail/clarity, wider soundstage


I also have the same understanding as you guys that the simplier the better....shorter signal path. But i'm just wondering other audiophiles use CDP>>DAC>>PREAMP>>POWER AMP combo and yet they get superb sound.

If don't need a preamp, appreciate if you can share some tweaks on how to improve my current setup.

cheers

[poobah]

If you are running now without a preamp... a preamp will not gain you anything... it will only hurt. Every time you process a signal you damage it a bit.

For other upgrades... to your amp... post a schematic. Keep in mind , "upgrades" does not mean expensive tubes, silver wire, and silly capacitors...

The best place to improve ANY system will usually be the speakers. They usually are the weakest link.

[audioboy69]

Poobah,

That's great!!. Would appreciate if you let me know your email address, will send you the schematcis ... thanks. I also want to know more stuffs in upgrading my amp.

As for the speaker upgrade , I'm a bit reluctant to do it since some audiophiles say it will just worsen the sound. I am using a Sonus Faber Concertino home bookshelf speaker. So what upgrades can be done ? Is it on the cross-over ? .. caps/resistors/internal wires ? Will open my speaker and see what stuffs inside that can be upgraded.

[poobah]

I cannot comment on your speakers. A far as your amp is concerned, post your schematic on the forum where all can see it.

I you trouble posting ask and people will direct you to various non-forum "image servers" that help you post large files.

[Giaime]

Yours are very good speakers, leave them stock or just change them. Please don't modify a fine italian design

For the preamp question, in a "technical" way I could say that a preamp is a redundant gainstage that obviously could only damage the sound.

From the "audiophile" point of view, I MUST say that if you don't like the sound of CD>>Power amp, there are chances that you like better the CD>>Preamp>>Power amp combination. That's for the COLORATIONS that a pre makes on the sound. Your ears can, in some cases, feel that those colorations sounds better. You'll be the judge.

Tweaking a preamp when you have got iron and chassis is not expensive, so why don't give it a try? I'm always suggesting an Aikido, or the SY's Heretical that is one of the best engineered preamps that I've seen in my whole life.