Melos SHA 1 Preamp help/advice HELP HELP
May 25, 2008 at 1:28 AM Thread Starter Post #1 of 16

sedan delivery

Mar 28, 2007
Okay,,after searching the threads for about 8 hours today,,I am now a beaten man. I want to take my SHA 1 to a higher level. I'm using it in a two channel system,mostly vinyl.I am sincerely seeking advice/help in which/what components on the board to upgrade/replace. I have identified 4 caps between the tubes,,and one on each side,and one on the left rear.I would greatly appreciate any advice,pic's or tutorials in taking this to a higher level as a preamp,,and headphone source as well. Thanks in advace--george

I tried to attach pic's of the board,but they are too large,,I'll keep working on that. BTW,, the unit has an IEC inlet/connector,, 3 inputs,,one pair of outputs,, and the color of the board is green,, at least to my old eyes..
May 25, 2008 at 9:38 AM Post #3 of 16

Originally Posted by nikongod /img/forum/go_quote.gif
any way to get a gold? much better preamp.

will write more tomorrow.

No gold for right now,,,I'm pretty good at soldering and following directions, I have rebuilt a few crossovers in Polk SDA speakers. I had heard so much about the Melos used as headamps,I picked up a nice one,, at the time I did not realize that I wanted/needed the gold. So,I thought that since I had it,, might as well recap/update it and see what it'll do,I,ve had too many pre's thru the house and it's time to slow down. I just think that if/when I get this done,,the Melos will be here for awhile. Thanks--george
May 25, 2008 at 3:23 PM Post #5 of 16

first the why: for both sha's the ORIGINAL design was as a headphone amp, with both preamp outputs added as an afterthought. in the sha-1, they *simply* divert the headphone output to the back of the case and send it on its merry way. on the gold there is a dedicated preamp driver circuit, which is entirely separate from the headphone circuit.

now, for the sha-1, heres what to do:
the caps between the tubes are important.

The REALLY small ****ty caps on the inputs of the tubes, also important. the sha-1 will require "creative mounting" to get anything worth having in the signal to fit. you MUST NOT jumper these caps, the circuit requires their presence.

The electrolytic caps in the LV supply (along the back of the board) after the regulator are important. the lone cap off on the back right of the board is also somewhat important.

For use as a preamp, the output caps should be upgraded.

After that I am of the opinion that things get smaller, but in the order of next things to do:

upgrade the caps in the HV supply. actual capacitance is not important, but quality is. As the caps get further from the tubes (tracing the circuit), they get less important.

Replace both rectifiers with ones made with (hex)fred diodes.

Upgrade resistors in signal path.

I replaced the first resistor in the HV filters with a smallish (5h/40ma/150ohm dc) inductor. Fans of active filtration will tell you it is soooo good it wont make a difference, but the hiss went away. Pwned.
May 25, 2008 at 3:36 PM Post #6 of 16
Thank you sir, for taking the time,I sincerely appreciate it.I'm going to price the caps and see if it would be worthwhile,,versus selling it and adding the cap cost in,and maybe aquiring a gold. Thanks again for your help---george
May 29, 2008 at 12:42 AM Post #10 of 16
Well,, finding the caps has been an adventure,, the film caps were easy,,, electrolytics,,, finally got em ordered,, three different vendors,, my how the time flys while searching/ordering online,,, enough for tonight.
Jun 11, 2008 at 7:59 AM Post #11 of 16
Just an update,, I've received the electrolytic's,,or at least most of them,, got some dynamicaps on the way as well,, I'll get started this friday and post some pic's as I go. Hopefully the end result will meet my expectations, as I'll be using it as a pre for my 2 channel as well as headphones.
Jun 14, 2008 at 7:02 PM Post #12 of 16
Well,, got everything back together,, sounds great EXCEPT nothing from the right channel. I've changed/swapped,tubes,interconnects,phones etc,,,I'll admit that I need help at this point,,any suggestions would be greatly appreciated.
Jun 14, 2008 at 11:14 PM Post #14 of 16

Originally Posted by sedan delivery /img/forum/go_quote.gif
Done,,, wire from the volume control,,if anyone is interested,I'll update later with pics.

I'm interested. Would you be nice enough to post a few pics of your work and a writeup of the sound difference? No rush, I'm sure you need a little time to enjoy your "new" toy!
Jun 15, 2008 at 4:29 AM Post #15 of 16
I'm definitely interested in any info and photos, as I have the same unit.

When you said "got everything back together,, sounds great EXCEPT nothing from the right channel", were you implying that you thought it sounded better then stock, even though you were only listening through one channel?


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