Sonny JR (I / II) amps

[Morten Stenbaek]

Hi !
Since the Sonny JR I + II no longer are made and really hard to get (well sometimes they are on Ebay – but no one seems to be willing to send them to Europe), I was wondering if anybody had the schematics or concept of the amp. I’ve seen some pictures (not close enough though), and they look kind if simple (well less is often more) – just what I like.

Thanks
Morten

[Bruce / Mission Amps]

You mean this one?

http://home.earthlink.net/~kb0tj/PHOTOS/sj-8in-spkr.jpg

There is really nothing to them if you know what a tweed Super 5C4 type amp is.

[Morten Stenbaek]

Thank you Bruce !

Thank you Bruce !
I was actually in doubt if I was to bold to ask for this ! Well I know assume that it’s OK. A few questions though ! I’m a musician and not a technician. My amp work is done by looking at the layouts and having a little understanding for the different values (caps etc.). So I get confused when looking at this octal preamp layout (http://www.ampwares.com/ffg/schem/super_5c4_layout.gif )– sorry ! Also there is a few resistors over the OP tubes. Could you help me with these questions ?

Thanks !
Morten

[dl5mhk]

You mean this one?

http://home.earthlink.net/~kb0tj/PHOTOS/sj-8in-spkr.jpg

There is really nothing to them if you know what a tweed Super 5C4 type amp is.

The SJ 410 must be a Bassman clone, i compared the pics on Sonny's website with the Bassman layout, it fits 100 %. I'm in doubt wether the paper in oil caps would make such a big difference to other good quality caps, eventually it's a matter of the speakers. I've seen extremely good harp amps losing their mojo after a speaker swap.

cu,
Ralf

[MWJB]

The SJ has a cathode biased 9 pin preamp, not a grid leak, octal preamp set up. I could be wrong but it appears that V1 cathodes & plates are tied together, as the preamp coupling cap is connected to V1, 1, I might also assume that the V1 grids are also tied together? Try it wired like that, then try one triode only (double plate & cathode values) and see what sounds best to you.

Grid stoppers look like 1.5K, I would assume that the screen grid resistors would be 470ohms? There also appears to be a cap on each output socket, a grid to ground cap to bleed off highs? Look at a typical Silverface Fender socket, you'd have to try different values on the grid to ground cap (1000pf, 2000pf, 3000pf etc) and see what works.

Don't fit the 500pf cap on the tone control on the 5C4 schematic.

Use a 2 ohm output transformer and wire 4x8ohm speakers in parallel. I don't know if Sonny did this but don't go series parallel, it'll cut headroom.

[Bruce / Mission Amps]

"The SJ has a cathode biased 9 pin preamp, not a grid leak, octal preamp set up."

Right

"I could be wrong but it appears that V1 cathodes & plates are tied together, as the preamp coupling cap is connected to V1,
I might also assume that the V1 grids are also tied together?"

Right again, both triodes of the first preamp tube are in parallel. The phase inverter tube is a 12AU7 if I remember correctly.

Grid stoppers look like 1.5K, I would assume that the screen grid resistors would be 470ohms?

Correct

"There also appears to be a cap on each output socket, a grid to ground cap to bleed off highs?

No, the tubes that were plugged in had red bases. Your are seeing the base alignment pin of the actual tube.

"Look at a typical Silverface Fender socket, you'd have to try different values on the grid to ground cap (1000pf, 2000pf, 3000pf etc) and see what works."

Sure you can try that too.... not a problem.

"Don't fit the 500pf cap on the tone control on the 5C4 schematic."

Oops...I guess I was too vague there... it is more like slightly modified, single channel 5D4.
Correct there is no treble brightening cap. It is a simple .01uF cap across the wiper to the top of the pot. Both tone and volume pots are 500k by the way.

"Use a 2 ohm output transformer and wire 4x8ohm speakers in parallel. I don't know if Sonny did this but don't go series parallel, it'll cut headroom."

Hmm I can't remember 100% about that but I think you are right 2 ohms.
I'm thinking all four 8's were in parallel but the OT was a 2-4-8 ohm OT and you could pretty much do what you wanted.
I just remembered... there is a sliding switch on the bottom edge that allowed the 2-4 or 8 ohm tap to be used. It just steered the speaker jack to which tap you wanted to use

Personally I did not find this amp to the "Great Harp Amp" I expected based on the hype. I think it sounded way better in my 4x10 8 ohm. shop cabinet, which has two reissue C10Qs and two reissue P10Rs.
Don't get me wrong, it was going in the right direction and sounded very good but not worth the money, IMHO.
I think a decent DIY'r could build one for around $500-600 with new parts, a half way decent homebrew cabinet and inexpensive 8" speakers.

[MWJB]

Thanks for the clarification Bruce.

There's SJ1 on Ebay at the mo', speakers are not parallel on that one. Looks like a series-parallel or parallel-series arrangement (I can never remember which is which), I'm guessing a 4ohm load, which would work with the impedance selector. Even so, parallel 2 ohms would work better.

Ralf, yes you're right the SJ410 is a bassman, with Sonny's choice of caps & speakers tubes. A very different amp to the SJ1 & 2.

[dl5mhk]

Even so, parallel 2 ohms would work better.

What would be different with an all parallel load?

Background is, i constructed an harp amp with 2x12AT7 (first stage at very low plate voltage, but switchable to 150 volts for more headroom), Peavey Classic 30 tone stack, Master vol. pot, a Bassman style phase inverter, and 4x 6BQ5/EL84 as in the Vox AC30, driving a 6x8" speaker array, arranged as 2 in series, 3 of those rows parallel. Would the sound change be very different then?
Btw. we have 2 sound samples on youtube - just look for "alligator harp amp"

Ralf, yes you're right the SJ410 is a bassman, with Sonny's choice of caps & speakers tubes. A very different amp to the SJ1 & 2.

Yes, ít's very different. I also have a Bassman RI, with Eminence Blueframe Alnico speakers, it's really not bad, but sometimes it can be a bit harsh - and i'm not shure wether i should begin to change caps or not, i don't think caps are SO important for the results. I believe, the OT and the speakers have much more influence on the sound than the type of some caps in the signal path, as long as they (the caps) are of good quality, not cheapo ceramic caps.
But since i have the Alligator, i didn't play the Bassman any longer...that crocodile has - despite the 8"ers - a huge bass response and it really sings.

cu,
Ralf

[MWJB]

You don't say what impedance your speakers are, unless they are 16ohms each I don't know if you would find an OT that would run them in parallel (2.66 ohms for 6x16ohm speakers), I've never tried running 1.33ohms (6x8ohms), sounds a bit close to a dead short to me. So your options might be limited.

Parallel speakers (for a given load) are easier for the signal to push, more sound out. Series & series parallel eat up efficiency, headroom and feedback more. Not so much of an issue for guitar players who rarely have to worry so much about acoustic feedback.

Changing coupling and tone caps in your bassman is not going to make a big, or even an audible difference. We back to back tested a whole bunch of amps with Astrons, Mallorys (vintage), Mallory metallised polyester, Euro generic metallised poly, foil & oil Astrons & Gudemans. No conclusive biases or preferences, that could be attributed to the caps, were felt by the 4 players present. Sonny uses them as part of his "synergistic" approach.

[dl5mhk]

You don't say what impedance your speakers are, unless they are 16ohms each I don't know if you would find an OT that would run them in parallel (2.66 ohms for 6x16ohm speakers), I've never tried running 1.33ohms (6x8ohms), sounds a bit close to a dead short to me. So your options might be limited.

I don't worry about beeing nearly short there, as long as no additional DC resistance would limit the output power. Tube amps can handle shorts easily, so they can handle a "near short" situation as well. (hopefully)

Ummm....sorry, we have it vice versa: 2 parallel rows of 3 series speakers, each one has 4 Ohms:


|--- 4 --- 4 --- 4 ---|

|--- 4 --- 4 --- 4 ---|

Parallel speakers (for a given load) are easier for the signal to push, more sound out. Series & series parallel eat up efficiency, headroom and feedback more. Not so much of an issue for guitar players who rarely have to worry so much about acoustic feedback.

Ahh! So i could try at least 3 parallel columns of 2 series wired speakers without buying new speakers...

Changing coupling and tone caps in your bassman is not going to make a big, or even an audible difference. We back to back tested a whole bunch of amps with Astrons, Mallorys (vintage), Mallory metallised polyester, Euro generic metallised poly, foil & oil Astrons & Gudemans. No conclusive biases or preferences, that could be attributed to the caps, were felt by the 4 players present.

Well, that confirms my presumptions pretty nicely. We don't talk about RF applications (where we have big differences between different types of caps, especially regarding Q and the current handling abilities (for power amps - 1 kW into 50 Ohms is a whole lot of current!).

Sonny uses them as part of his "synergistic" approach.

You US guys are always so gently...

cu,
Ralf

[MWJB]

Aha! I know I talk about tubes rather than valves, grounds rather than earth...but that's in deference to our hosts and presumably the majority of readers.

I'm actually English (see... that proves it, the English do say "actually" rather a lot) :-)

TTFN

[dl5mhk]

Aha! I know I talk about tubes rather than valves, grounds rather than earth...but that's in deference to our hosts and presumably the majority of readers.

I'm actually English (see... that proves it, the English do say "actually" rather a lot) :-)

TTFN

Yep...i just saw it in the Harp King and AFB+ Thread.

Well, you folks from the UK are in no way less gently and polite than the stateside guys. :-))

Well, regarding the Alligator amp - i'll keep it untouched, concerning the speakers configuration. Months ago i played a Peavey Classic 30 and haven't been able to compete with the guitarists, but with the Alligator it's not a problem to show two of them what Rod Piazza was talking about, when he said "The harp is the loudest instrument in the band!". And i had some guys really make big eyes, when i held the mic in front of the amp, half a meter away, and there was no feedback at all...
I also had guitar players using that amp, and they've been impressed about it beeing what we call "druckvoll" in german - "lots of pressure", ooomph, or anything else in english...although it doesn't really distort in the preamp section when used with a guitar, it's more of a power amp compression and roughness because it doesn't have neg. loopback in the final stage.

The feedback resistance depends on the plate voltage of the 1st triode section - when used with 40...50 Volts there is a lot of sweet distortion and huge bass response, but nearly no feedback. Increased to 150 Volts the bass response is much weaker, less harmonics (more headroom), and it feeds back easier.
On the other hand the lower plate voltage also adds pretty harmonics - then it has a good part of bite (harmonics!) even with the treble pot in the 11 o'clock position, whithout overemphasizing bass or treble.
For sure the gain is a bit reduced then - but that's not an issue, since the high Z harp mics deliver so much output, and the EL84's don't need much signal...

cu,
Ralf

[Morten Stenbaek]

SJ II picture

I found a SJ II picture ! where everything is seen from another angel.
Still the same thoughts about the design (modified - 5D4) / any other thoughts ? >> http://www.lightningmoe.dk/Sonny%20Jr2.jpg <<

My reason for being interested in these amps are that they should have been design for a dirty sound - right ! I like the Little Walter sound on Rocker. I do expect that you all now tell me that this has been done by using a small SE amp – but hey no crime in trying to get that sound on stage right ?

[dl5mhk]

My reason for being interested in these amps are that they should have been design for a dirty sound - right ! I like the Little Walter sound on Rocker. I do expect that you all now tell me that this has been done by using a small SE amp – but hey no crime in trying to get that sound on stage right ?

Morten, it's been said probably hundreds of times, that the sound comes from the player, but the very most impressive provement of that are the 2 video clips in youtube.com, LW together with Hounddog Taylor. He plays acoustically, but with a really HUGE tone, unbelievable. For sure the amp is part of the sound chain, and i'm also looking for the Holy Grail of amps and mics, but there is no such thing. I realized that definitely when i saw those 2 videos.
Nevertheless i like the sound of Kim Wilson too, especially that from the "Ludella" album together with Jimmy Rogers - not really distorted, but not clean, very breathy, no heavy bass, rather trebly, it sounds sooo great! I have no idea, how he did that!

cu,
Ralf

[MWJB]

There's not really any point in guesstimating what amp LW used on what recording, sure there are amps he is pictured with, some tracks even suggest a specific character that could be attributed to some of them, but there are too many variables to be sure (studio tape delay, studio echo chamber, or both, what restrictions were placed on LW in the studio by Bill Puttnam, would LW have sounded the same the next day or next even the next track in the same studio after a change in mic placement - there's a whole bunch of tracks that were recorded on the same day that sound remarkably different, check out the Toddle - sounds totally unique.)

As Ralph points out, and I'm sure you're also aware, LW sounded like himself (check out "A Quarter to 12"...no amp) - if you don't sound like LW anyway, any amp that does make you, isn't going to sound like his amp - I guess what I'm saying is you have as much chance of sounding like him by using totally different gear as you would by using the same gear.

Back in those days no amps were designed for a dirty sound, everyone was trying to get clean.

From what I've heard of the SJ1 it's better at capturing a later 50's style LW tone (Temperature, Nobody But You) than something like Rocker.

However, there is some logic in what you're assuming - many of the amps that he would have played through would have been cathode biased, paraphase phase inverter, may or may not have had preamp cathode bypass caps (some manufacturers such as Premier & Danelectro/Wards/Silvertone) did without them for reasons of cost), relatively low plate voltages, at the time of Rocker many amps were grid leak biased like the 5C4, probably not any negative feedback in many cases. SE? Possibly, possibly not?

Also be aware that many amps that fit these perameters are not going to be loud enough to gig with in a band with 50W fixed bias guitar amps, LW wouldn't even allow an acoustic sax on stage, according to one report, in case he was drowned out.