SANO HI Fidelity Stereophonic 30W, help w/preamp mods

[sig]

Hi,

Paul here, back again with a new project on an old amp of mine. I attached a schematic which I got off the web, looks pretty accurate except my SANO 30W doesn't have reverb and currently has 2 6CA7 output tubes.

I'm not an amp tech, but you all have helped me in the past repair my old Musicmaster Bass Amp and I did the repairs on my own. I used two of the Musicmaster Bass Amps with my band www.myspace.com/thepaulsigmonband one of the amps I had modified by Winfield Thomas, he did a nice job and I really like that amp!

OK, back to the SANO. I just replace the stock 15" UTAH speaker, it was blown... The AMP sounds really clean... in fact.. too clean. I like headroom, but this amp will blow your head off before it distorts. It was the same even before I replaced the speaker.

I love the weight of the amp, I'm a gigging musician and I really believe this amps has serious potential to be a little Tweed Super/Pro/VibroVerb type of clone... I think is almost there, but I'm not getting any of that tweed tone from the tonestack or inputs.

As the attached schematic shows, the amp has 3 inputs, Guitar, Instrument & Stereophonic. The amp has tremelo, but only on the sterophonic channel.

I'd appreciate anyone who might be available to look over the schematic for some possible suggestions for mods, in particular, I'd like to heat up the input and tonestack, perhaps tweed mods. I just don't know what to do and I've asked two techs for help, neither seemed interested in the project.

Thanks for your consideration. If any chance of someone drawing the mod suggestions on the Schematic, that would be the ultimate. I have a close friend who will help me with the electronics, he's a retired EE and loves to work on my amps; however, he specializes in old TVs and HAM radios and likes to use cheapo caps. So, I have to buy the better parts and guide him through the process.

THANK YOU all in advance!

Paul

Paul

[Winnie Thomas]

Paul,

The schematic shows two 12AU7s although the tube placement diagram shows only one and a 6U10 (noisy tube). Swap the 12AU7s for 12AX7s and you should see a big difference in sound.

Winnie

[Fretts]

I had this amp once, grey, with a wraparound grille, big gold Utah 15 and a huge chrome refrigerator handle on top.
+1 on the 12AX7 in the first position, it should really gain up like he says.
Or you could use it as a Pedal Amp and just run a nice box in front of it like a Blackstone, OCD, Wampler Plextortion, etc. That's what I did, I just left it clean.

[Glenden]

Sano mods

Paul, I have an older Sano with different preamp tubes, but the same types of circuits. Mine was too clean also. I did several mods that gave this thing some serious crunch, without changing any of the front panel controls or having to add or replace parts. One problem is the location of the volume control, it is right at the input, so it works exactly like the volume control on your instrument. Fenders and Marshalls have a preamp stage ahead of the volume control. The other problem is that the "stereo input" divides the signal into two channels that are remixed further down the signal path, out of phase. Basically, I lifted one stage out of the bass side of the stereo input channel, restoring the phase relationship but losing a little gain in the bass side of that channel (it had way more than I needed anyway). I rewired this stage to the input of the Guitar/instrument channel, ahead of the volume control. Believe it or not, it was still too clean. They weren't kidding when they called this thing "HiFi". So, I took all that signal chain from the guitar/inst channel and lifted it from the point where it mixes with the stereo channel, and wired it to feed into the stereo input jack, at what used to be the grounding switch on the jack. You lose some ability to run multiple instuments, but who cares? Email me tglenden@earthlink.net with your particular schematic and I can set you up with details to do your amp.

[Glenden]

Sano mods

Well, now that I have taken a good look at your schematic, there are several differences between my old Sano and your newer one. Mine has no reverb, and the guit and inst channels share a common input stage. Nevertheless there is a way to do the same type of mods. I see that there are no level controls on the bass and treble sides of your stereo input channel, whereas I have controls at the input. Your treble half has a cathode output, which is noninverting, and an inverting input. The bass side has an inverting input stage and an inverting output stage, resulting in the same out-of-phase problem mine had. This is not really a problem when fed by two different transducers picking up different notes from an accordion, which these amps were originally designed for, but it is a problem when fed by an identical signal. The cathode output is probably there to provide a low impedance for the reverb driver. I wouldn't mess with that. But I would mess with the bass side. The noninverting cathode stage doesn't add much gain, and there are two nasty tone-killer caps to make the bass half "bassy".