My SSS completed!

[Drumslinger]

Nicely done Sergio! Congrats on the build!

[sergio]

Thanks Sergio! A few questions regarding the "accent" control. Any reason you went with a switch instead of a pot? I've seen various SSS builds that use either. Is it some sort of presense or cut control?

no , no particular reason , for the moment I use this switch for jump the filter section. I want to understand the purpose of the filters, if they are really useful!.

I think ,more forward , I will use as a true "accent"

Sergio

[dreric]

Hi , I haven't a program for drawing a layout or schematic , but I can say , I used the layout #0002 ,with some change.

omitted the bias pot
omitted the 470K res. to ground on the power tubes grids and changed grid res. from 1k5 to 2k2.
pay attention to the layout in the part of LNFB on V1b ,there is an error in ground wiring.
470Ohm screen res.
30uFx3 can cap.

Sergio

Sergio

Would you mind elaborating on the error in the ground wiring on V1b. I've spent hours looking at my build, I know enough to figure out that V1b is the problem but not enough to figure out what the problem is.

I'm stuck! any help would be much appreciated.

http://ampgarage.com/forum/viewtopic.ph ... hlight=sss

[sergio]

I hope this can help!

[sergio]

In this period I played my SSS, very nice and funny, made ​​a few small changes to the filter circuit, but nothing important.

I noticed one thing that I think it's very significant, the power transformer gets very hot, I think it comes at a temperature above average, this could be a warning of something wrong!

I will try to re-wire the bias circuit in different type , with classic pot and bias tap wire!

Sergio

[CHIP]

Let us know how you plan to do that and keep your cathode driver voltage high enough.

[sergio]

it's only a test! but work the same and seems to me that the PT don't gets hot!!

[ToneMerc]

it's only a test! but work the same and seems to me that the PT don't gets hot!!

While that might work, if you are using the stock Twin PT and the stock bias scheme it's impossible to put 135V or so on the driver.

TM

[sergio]

135V? ,I have about -45v on 2/7 pin and -46v on the 3/8 pin.

[sergio]

Talking with a friend of mine, he is much more experienced than me, and told me that taking the bias voltage from a single branch of the secondary can cause an imbalance and thus overheat the transformer!

Cathode follower driver has high current consumption!

I then tried to take the bias voltage from both branches of the secondary and it seems that the transformer remains in normal temperature! only the bias capacitor to 450V may be too low, because at the node "F" whereas before I had 370V , now I have 405V.

conclusions: bias circuit of the schematic would seem wrong!

I would expect some comments from the most 'experts forum! and those who have already built the SSS.

Sergio

[ToneMerc]

Talking with a friend of mine, he is much more experienced than me, and told me that taking the bias voltage from a single branch of the secondary can cause an imbalance and thus overheat the transformer!

Cathode follower driver has high current consumption!

I then tried to take the bias voltage from both branches of the secondary and it seems that the transformer remains in normal temperature! only the bias capacitor to 450V may be too low, because at the node "F" whereas before I had 370V , now I have 405V.

conclusions: bias circuit of the schematic would seem wrong!

I would expect some comments from the most 'experts forum! and those who have already built the SSS.

Sergio

http://ampgarage.com/forum/download/file.php?id=27243

TK

[sergio]

I had already seen this! Do you have any comment on the bias circuit? can bias circuit of this layout run correctly about you?

Sergio

[ToneMerc]

I had already seen this! Do you have any comment on the bias circuit? can bias circuit of this layout run correctly about you?

Sergio

Sergio, that raw bias scheme works. You can tweak the 130K value to set your bias. I used a resistor and 2W pot instead of the 130K.

FWIW, I had a heavier PT wound that included a dedicated HV/high current bias winding.

TM

[CHIP]

TM, Would a Mercury Magnetics Twin Reverb PT be able to handle this bias circuit? I have one I was hanging on for the purpose of a future SSS project.

[ToneMerc]

TM, Would a Mercury Magnetics Twin Reverb PT be able to handle this bias circuit? I have one I was hanging on for the purpose of a future SSS project.

Chip the stock units work, however there other ways to skin this bias cat that at least on the surface would appear to more robust than hanging it off one side of the HT winding.
Next, what is your end goal? If it's a 150W amp with 6550 or even a 100W EL34, you will be exceeding at least the filament rating of the stock unit. If you combine this with the CF PI scheme, my belief is that you will be really taxing that PT.

I'm not really interested in the amp perse', but I would like to build a 150 or 200W SSS because the circuity is intriguing. That would require a nice piece of iron on both ends.

TM