Steel String Singer #001/#002/#004 Layout/Schematics

[Colossal]

Pretty sure that 1k is a known error and it should be 100R

[rccolgan]

Pretty sure that 1k is a known error and it should be 100R

Really? Hopefully we had two different approaches and came to the same conclusion I literally spent half a day searching through forum posts on the subject and came up with nothing. I gave it an honest shot sifting through before posting this past entry.

I think you are right about the V1b cathode resistor... it would match what is going on with V1a. I would think that the NFB will different with a 100R in there. Also the gain of V1b would change.

&

Since the supply voltage and plate voltages are the same I would think the cathode resistors should be the same (true if the triodes match exactly, which is the unknown here). I think it’s likely that the 1k is a mistake, since plate voltage for a nominal 12AX7 with 100k and 1k6 is 198, and with 100k and 2k5 it’s 220; just about 20V higher. 1k would result in 10x the feedback as 100R.

Good stuff here, Martin and dorrisant! I feel like I'm close with confidence after this peer review of a hunch.

Luckily I ordered a few extra 100 Ohm precision resistors so I'll pop one in place tomorrow and report back! Thanks!

[Colossal]

Pretty sure that 1k is a known error and it should be 100R

Really? Hopefully we had two different approaches and came to the same conclusion I literally spent half a day searching through forum posts on the subject and came up with nothing. I gave it an honest shot sifting through before posting this past entry.

I am 95% confident I read that on this forum some years back, while researching the SSS. One of those factoids that I took note of specifically and wrote it down on my own schematic to not overlook.

Kudos to you for arriving at that conclusion empirically.

[rccolgan]

Reporting back after I made the change from 1k to 100 ohm on v1b cathode. Significantly louder preamp gain now and tone shifts to the brighter side of the spectrum, but not horribly bright. I had to relearn what step filter positions I like with my strat. Bypassing the high filter used to be a great tone but now I set the high cut to the third to last position and low filter cut is one notch more than bypass.

I can barely crack the master level now past the second notch without shaking the house which is exactly what I thought the SSS's were supposed to be like. My SSS #004 style build is similar output when I bypass the internal dry signal trim pot. The reverb controls feel right now also. Reverb send/return is around 2 o'clock whereas they used to be at 10 o'clock. @Erwin - We may want to consider leaving the 1m dry signal trim pot in on your PCB now that I have experience with the correct cathode resistor to give some dry signal control.

Using the AmpRX Brown Box to dip voltages down to 104v (as low as it can go with 122v line voltage), my SSS voltages with a 5751 in v1 match the Japanese schematic pretty much 1:1 at 187v on both v1a and v1b. The rest of the amp measures fairly close as well to the schematic as well. I'm feeling confident about this and that there must have been a 5751 in v1 when the tech took readings on the original SSS #002.

Next up for my build is I need to swap out the 4x 100k RN65D resistors around v2 and v3 with higher wattage ratings since those are handling quite a bit of current through them and get warm. I already swapped out the 1.8k and 4.7k supply droppers with a 5w wirewound, 350 degree Celsius operating temp rated, Ohmite resistors. Those get hot! I can't imagine the original Piher 4.7k could stand that sort of load throughout all the years.

[martin manning]

Are your filters as shown in the Japanese schematic? If so, the improved version I posted might be something to try. https://ampgarage.com/forum/viewtopic.php?f=5&t=30118

[rccolgan]

Are your filters as shown in the Japanese schematic? If so, the improved version I posted might be something to try. https://ampgarage.com/forum/viewtopic.php?f=5&t=30118

Hi Martin - Right now, the filters are indeed the stock Japanese schematic type. I've been looking at your step filters and I'd agree it's a better approach and something I'm considering. I wanted to get to know the amp as intended before I poke around but the filters is indeed a place of interest.

[rccolgan]

I can't take credit for this one but one of folks who is building the SSS #002 using my project files, reached out to me and I think he is correct finding something that has not been found before with #002. (I tried searching again but no luck with these findings previously)

We believe the 270k circled in yellow should actually be 100k. I can see where the tech could have confused brown/black/yellow with red/purple/yellow after I looked at SSS #001 gutshot. What do ya'll think?

100k resistor 002.jpg

[Matt J]

Thank you so much Ryan for sharing all of your info and insights on this amp while you put it together! I can't wait to get started on my own.

I don't have an AmpRX Brown Box to lower the VAC down to 104, but I may pick up a small variac soon. Since I plan on using the normal 120v wall voltage at my house would you recommend increasing some of the dropping resistors to lower down the voltages, or do you think the amp would still work fine on the normal 120v?

Also, do you know the Mouser part # for the rotary switches you use for the high and low filters? I looked at your BOM on your GitHub page, but those switches seem to be Ayan Smooth and Slim pedal you've built.

-Matt J.

[rccolgan]

Thank you so much Ryan for sharing all of your info and insights on this amp while you put it together! I can't wait to get started on my own.

I don't have an AmpRX Brown Box to lower the VAC down to 104, but I may pick up a small variac soon. Since I plan on using the normal 120v wall voltage at my house would you recommend increasing some of the dropping resistors to lower down the voltages, or do you think the amp would still work fine on the normal 120v?

Also, do you know the Mouser part # for the rotary switches you use for the high and low filters? I looked at your BOM on your GitHub page, but those switches seem to be Ayan Smooth and Slim pedal you've built.

-Matt J.

Oh no!! I think I did miss a few things. Here is the Rotary I used. They are out of stock on Mouser so you might need to look somewhere else if you're ordering soon. I suggest going with one deck because the filters get tight against the preamp boards
105-SR2511F-17S SR2511F-0107-19R0B-E9-S-W-159 Alpha (Taiwan) Rotary Switches ROTARY 1 POLE 7 POS RoHS Compliant 2 $4.24 $8.48

120v wall outlet is fine because the transformers are wound for 120 and not lower like back when wall outlets were lower. Having the AmpRX is not a deal breaker but it's a net piece of kit to own. I'm happy to chime in on a new build thread once you start yours if the topics conflict with the intention of this original topic.

[Matt J]

Thanks Ryan!

Mouser has those switches on back order until at least September. I went ahead and place an order for them but it looks like it is going to be a wait. I couldn't find any other retailers with them in stock online.
If anyone has two of those rotary switches and is open to selling them, please PM me!

- Matt J.

[M Fowler]

Ryan,

I spent most of yesterday being lazy and going through your youtube videos, so much going on and it was fun to view.

Regarding the Two Rock John Mayer Signature Reverb being dark. I built one based of the first schematic posted on TAG and that amp is incredible not dark at all.

Mark

Two Rock JM Signature final schematic.jpg

John Mayer Signature clone 006.jpg

[rccolgan]

Ryan,

I spent most of yesterday being lazy and going through your youtube videos, so much going on and it was fun to view.

Regarding the Two Rock John Mayer Signature Reverb being dark. I built one based of the first schematic posted on TAG and that amp is incredible not dark at all.

Mark

Two Rock JM Signature final schematic.jpgJohn Mayer Signature clone 006.jpg

Beautiful amp, Mark! Thanks for you for watching. My videos are "brain-dumps" for the most part and hoping I can get to clear explanations like Uncle Doug!

Thanks for attaching your schematic. It does look a little bit different than the one I built which may account for the differences in tone, and that's ok. The treb/mid/bass pots on mine is 260k/100k/250k and 330pf mid cap. I am supposed to have a date with a real JM sig (one of the 25) soon to reverse engineer a bit more to uncover any additional secrets. I'm sure yours is glorious and a bit more rounded than mine so far. Mine is very much "in the pocket" sort of tone that lends itself great with blues but I'm digging this SSS #002 more for well-rounded tone

[Matt J]

I was just re-reading some of the descriptions of the various SSS known to exist and noticed for the first time that SSS #004 does not have a cathode follower in the PI. Anyone have any information on why HAD decided to build #004 that way?

I'm curious as to how this might affect the tone and feel of a big clean amp like this. Has anyone who build an amp based off of #004 omitted the CF too? If so, what were your thoughts on it?

- Matt J.

[norburybrook]

IN reply to the last two posts.

I built a JM sig amp a couple of years ago and used vintage Peavey Iron, it's running around 500vDC on the plates.

A friend of mine tested it against one of the original JM amps owned by racing driver Jackie Stewarts son. ( i think he paid £20K for the amp)

My amp has two dirty switches to remove the local and Global NFB and I changed the voltage divider to give slightly more gain.

My friend said he thought the original JM was nice but nothing special. My JM with the higher voltage and bypassed NFB sounds like a SSS and he loved it, much preferred it to the original.

SSS# 004 I think is similar to this , no cathode follower and perhaps no NFB.

so with the switches and the cut control the amp is very versatile going form a great clean Jazz amp to out and out balls to wall SRV


M

[Aaron]

I’ve built both. SSS #004 has more LNFB loops that give the amp a different feel to the JM model.
I usually have the preamp volume on 10 on the #004 build, almost sounds like a compressor is on, with very little preamp break up. The amp has a warmer/spongier sound compared to my SSS #002 build, if that makes sense.

The JM does beautiful cleans and can break up a little when cranked.

Thanks,
Aaron