Upgrade Item Numbers ?

[SteveH]

All,
When looking at the circuit, what items are best to 'upgrade' ? Granted, I know that the whole circuit is only as strong as its' weakest link, but I believe that for the most part, the mouser BOM isn't too bad.
So, from what I have read on here:

R9-R12 would benefit from some high quality 3w Metal Film resistors
C1 - C8 would be the place for the high quality PIO, etc caps
(I only see references to C1, C2, C5 and C6...But I am assuming that that is for the one side only...?!)
C18 and C19 would benefit from a close tolerance cap as well

Obviously the interconnects and tube sockets. Now, as far as the terminal blocks go, would it be any real upgrade to actually solder the wires into the PCB instead of using the terminal block ? I was actually surprised to see them on the PCB....

Thanks yet again,
Steve

[ashok]

Hi Steve,

I like the terminal blocks. This past week, I rewired my ST35, rerouted some of the wires, trimmed off excess wire from the transformers leads and so on, and having to not desolder wires from the PCB was most convenient.

As for the components themselves, I built the amp with the basic components and listened to it for a few months. After that, I changed the capacitors in the coupling positions C1, C2, C3 and C4 in the revision C to Auricaps. Did it make any difference? Honestly, I could not tell. In retrospect, I should have trained my ear some more to the sound of the amp in stock form.

As always, this is just one man's opinion.

Ashok

[leadtower]

I listened to the stock ST 35 with the terminal blocks and Orange Drop 715's as well as standard carbon resistors in my initial unit. I then changed out the bias resistors for tantalum 1% values. The 3W I used mills wirewounds. I swapped out the Orange drops for Angela oil caps as filter and couplers. I listened to that amp for about 8 months. Then I swapped out the board for a new board.
I substituted solder pins for the terminal blocks; tried Wimas as coupling and filter caps and went with Kiwames in all sensitive positions.
That board is the one I am using now. What I learned? The soldered pins went first and that seemed to make a little difference in terms of detail resolution. Music seemed a little more defined and the bass seemed a little tighter and punchier. Small change but I think very noticeable. The oil caps made a nicer; smoother presentation over the Orange Drops. The resistor changes I really could not say if that made a big difference to me.
I also tried hardwireing the speaker leads for a while. I really didn't listen for long to the amp that way so I can't comment with absolute certainty but it seemed to make a small difference.
If I did it all over? I would use the soldered pins; Orange Drop 716's and the kiwames. In fact; in my ST 70 driver board the 716's to my ears sound as nicely musical as the oils. A different sound but equally good.
I would like to try larger wattage resistors next. I bought a bunch of PRP's from Parts Connection at 2 and 5 watt ratings to try. BTW; I use EI's in the EL 84 spot.
I also borrowed a quad of EL 84's Mullards for a couple nights from a friend. That did make a difference! I would use Orange Drops and Kiwames and pay my money for better tubes next time around.
I used a single driver speaker and Altec Valencias for the listening end of the system. I really am impressed with the ST 35 on this SD speaker; it continues to amaze.

[mesherm]

I would second leadtower's suggestions. Use 1% metal films reistors and Orange Drop 716s (or 715Ps), and then tube roll.
I won't use Solen Fast Caps anymore for other than power supply bypass.
I found the biggest difference is with using different tubes.
I use NOS signal tubes exclusively having had bad experience with some new manufactured ones.
In my latest amp JJ KT77s sound the best, with 6CA7EHs a close second. The worst were a set of KT88EHs (which sounded great in a different amp).

[SteveH]

Thanks guys ! So I guess my question now, is which ones specifically ? Was I right about C1-C8, etc ?

On a side note, I received my board today; it is really impressive ! I plan on doing some nice macro photography on it before final assembly =)

Thanks !
Steve

[SteveH]

All,
Ok, so one last check here. On a new Rev. D board, I am looking for the parts which would benefit from an 'upgrade' over the stock BOM. So, after searching and reading, I have come up with this list:

Caps:
C1-C4
C18, C19
C22, C23

For C1-C4, I am thinking PIO. If nothing more, than the psycoacoustical benefits. As for 18 and 19, I believe just something with a tight tolerance would work ? C22 and C23 I have no idea; just saw a reference to them when I did a search.

Resistors
Use 1% metal film in all locations. For R9-R12, use 3w IRC metal films.

Misc
High Quality Interconnects

I *think* that is about right. Hopefully I will get my BOM together and order all of the parts tomorrow. I am still not sure what output transformers I will be going with; however as I will be doing tube rectification, a Hammond 272HX will be supplying power.
Oh, one more question: what gauge/type of wire should I get for hookups ? (I will be placing the sockets and coupling caps off the PCB)

Well, that should about do it. Hopefully this will get your blessings !

Thanks,
Steve

[TomMcNally]

Hi Steve ...

I personally don't think mounting the sockets off the board is a good idea. Extending the lead lengths could cause problems with crosstalk and oscillation. You might want to discuss this with Shannon.

... tom

[SteveH]

Tom,
The reason why I wanted to mount the sockets off of the PCB is because I want to have 'mount on top' type of socket. I am assuming that the leads from these sockets will not be long enough to reach the board...

Does everything else look correct though ?


-Steve

[TomMcNally]

The top mounted sockets could have bare wires attached, and threaded down through the board, but once you soldered the leads in place, you could never remove the board to work on it. I like the PCB mount sockets myself, and with the barrier strips, the board can be removed in 5 minutes. Building it any other way takes away the advantage of the PC board. You may as well hand wire point to point otherwise.

I don't see any advantage in upgrading the components, so I won't comment.

Just my opinions here, based on lots of experience.

... tom

[SteveH]

Just my opinions here, based on lots of experience.

... tom

So I have seen !

The reason for the whole socket thing. Like I said before, I wanted to use a brass top-plate for my amp. Due to this, we discussed using the brass plate as an over-lay atop a regular steel plate onto which I would mount the trannys, etc.....So, if I mounted the sockets surface mount on the steel plate, they would be nearly flush with the brass top plate.

Thanks again.

[TomMcNally]

If you use the ceramic PC mounted sockets, and large holes in the brass plate (say 1") you can do the same thing. The advantage of the brass plate will be the ability NOT to have any screws showing, you could mount the PC board to the steel plate with countersunk screws (assuming it's thick enough) and you could have a nice looking top plate. If you use wired sockets, the board and sockets will become one big permanent sandwich. You can vary the spacers between the ST-35 board and the chassis and have the tubes higher or lower as desired. If you want a nicer look, go with a deep chassis and hide the ugly transformers underneath, or if you want them on top, get the cool nickel plated covers from Ned Carlson - they are sweet !

[SteveH]

Tom,
Ah, thanks for the solution. I just wasn't sure how far the PCB needed to be mounted from it's plate.
As for the transformers, I am planning on making a wooden cover for them as part of my enclosure (The brass plate will stop at this point as well).

Thanks again.
Steve

[rhing]

I substituted solder pins for the terminal blocks...
If I did it all over? I would use the soldered pins; Orange Drop 716's and the kiwames. In fact; in my ST 70 driver board the 716's to my ears sound as nicely musical as the oils. A different sound but equally good.
I would like to try larger wattage resistors next. I bought a bunch of PRP's from Parts Connection at 2 and 5 watt ratings to try. BTW; I use EI's in the EL 84 spot.

I am considering building this amp with soldering pins as well. Can you steer me toward the soldering pins that mount on the PCB?

Thanks,

Rich

[Shannon Parks]

Rich, do you mean like this? Those are Mouser part numbers.

Terminals:
534-1502-2
0.17

Stake punch:
534-TL-2
11.01

Anvil kit:
534-1721
25.27

[rhing]

Those look like soldering pins that would work on the ST-35 PCB. Thanks a lot Shannon.