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Author Topic: newbie question about cranked amp overdrive  (Read 1097 times)

dmfp123

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newbie question about cranked amp overdrive
« on: December 23, 2021, 01:39:00 PM »
Hey guys! First post here. So I've always associated solid state amps cranked on the clean channel with this horrible raspy kind of overdrive, but... well I'm a guitar teacher, and I bought a cheap old guitar/bass/organ montgomery wards amp for kids to use at the studio, and cranked it sounds amazing

What gives? What's going on in the circuit that makes one cranked SS amp sound awful and another sound very musical?

Thanks!

dmfp123

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Re: newbie question about cranked amp overdrive
« Reply #1 on: December 23, 2021, 01:57:26 PM »
Oh, here's a gut shot--yes I've soldered that filter cap back in place since this was taken, haha


Enzo

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Re: newbie question about cranked amp overdrive
« Reply #2 on: December 23, 2021, 08:50:51 PM »
You are slinging the term solid state around as if it was the determining factor.  Solid state means it isn't based on vacuum tubes, nothing more.   Somehow I am reminded of my friend who has a little Volkswagen car with a diesel motor, yet I have another friend who drives a large dump truck, also with a diesel motor.   How can they be so different, they are both diesels?

SOlid state doesn't specify much.  Circuits in two amps can be VERY different.  Different circuit, different parts, different speakers (very important part of tone), different enclosures.

I can't see it well, but is the date code on that loose cap from 1975?  40 year old caps can surely make an amp sound crappy.  Just one possibility.

dmfp123

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Re: newbie question about cranked amp overdrive
« Reply #3 on: December 23, 2021, 11:00:39 PM »
that's fair... but this 1975 amp sounds great cranked, lol

which is the question... why does this one crank into a very musical distortion while others don't? Is there something one "usually does" when designing an amp they want to be able to crank into nice drive tones?

Tried it through another speaker and the drive still sounds good so I know that's not the determining factor at play

Enzo

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Re: newbie question about cranked amp overdrive
« Reply #4 on: December 23, 2021, 11:42:38 PM »
Is there some thing?  No.  One sets out with a gain structure in mind.  One then decides what sort of voice it wants to have.  Consider the tone stack.  I link below to Duncan Amps page.  They have this really cool "tone stack calculator", a bit of free software you can download.  It sets up several common tone circuits, and offers graphic frequency response in real time as you adjust the controls.  If you look further into it you will find you can even change component values.  And that is ONLY the tone circuit.  Amp designers have to balane MANY factors.

https://www.duncanamps.com/tsc/

dmfp123

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Re: newbie question about cranked amp overdrive
« Reply #5 on: December 23, 2021, 11:48:28 PM »
Is there some thing?  No.  One sets out with a gain structure in mind.  One then decides what sort of voice it wants to have.  Consider the tone stack.  I link below to Duncan Amps page.  They have this really cool "tone stack calculator", a bit of free software you can download.  It sets up several common tone circuits, and offers graphic frequency response in real time as you adjust the controls.  If you look further into it you will find you can even change component values.  And that is ONLY the tone circuit.  Amp designers have to balane MANY factors.

https://www.duncanamps.com/tsc/

I see. My best bet may be trying to clone this and then play with different parts/values to see how it changes things

Any source for the schematic? I know one in the same line was the 62-9133 but I'm not sure if it's the exact same one... this one had a 15" speaker if that helps

If not, should I ask in this room or in the schematic one?

Enzo

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Re: newbie question about cranked amp overdrive
« Reply #6 on: December 24, 2021, 12:59:01 AM »
Doesn't matter, we read them all.

I don't have any solid state Wards drawings.

galaxiex

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Re: newbie question about cranked amp overdrive
« Reply #7 on: December 24, 2021, 02:20:10 PM »
Trace the circuit.
Draw schematic from that.

It shouldn't be too difficult.

I've drawn quite a few schematics for old, cheap, SS amps where the schem is unobtainium.

Search my threads in "schematics and layouts".
If it ain’t broke I’ll fix it until it is.

Jazz P Bass

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Re: newbie question about cranked amp overdrive
« Reply #8 on: December 24, 2021, 04:12:53 PM »
I found 2 Ward Airline SS schematics in my files.
Here they are.

Loudthud

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Re: newbie question about cranked amp overdrive
« Reply #9 on: December 24, 2021, 04:40:44 PM »
Huh ? Those schematics look like wireless transmitters.

phatt

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Re: newbie question about cranked amp overdrive
« Reply #10 on: December 25, 2021, 02:47:06 AM »
As Enzo has noted MANY things come into design and tone control is only part of what some call *System Tone*
By the looks of the picture posted it's and old style SS power section using an inter-stage Tx with a simple preamp front end.

The secret tone sauce you are hearing will likely be due to what looks like an "inter-stage transformer" which was widely used in those early designs.

Transformers are a big cost factor even for low quality units and as will be observed from later SState designs where they are mostly direct coupled to save cost.
You can still find some Tx coupled SS amps but co$t a lot more.

By design Tx coupling can have a magical effect on the outcome.
Now I'm not tecky enough to ez-plain every last detail but in simple terms they limit the bandwidth of the signal passing through them.
A lot of amps from early SS era (like yours) and most of the big name famous valve OTx's of years past used medium/low quality Tx's.
In fact the more power that runs through them the more the bandwidth is limited, delivering a sweet distortion.

So by design all the harsh hi freq crud is simply not able to be transferred from primary to secondary  (Bass is also limited somewhat) which leaves you with a much sweeter smoother Overdriven tone.
You can design an audio Tx to pass full bandwidth (i.e. High Quality HiFi spec) but cost will rise dramatically.

Older designs tend to use less Neg Feedback which might have some effect.
There may well be some sag in the power supply as well which can help with the feel of the OD sound.

Now that does not mean you can't make great amp tone without a Tx,, you just need to approach the design stage with other tricks.
I use a Cab sim circuit and a few other tone shaping gizmos to attain a smoother Odrive tone.
Yes you could back engineer the circuit but the Tx will likely be hard to source.
----
As I've said many times after 30~40 years of building amps, pedals and many odd ball circuits I still have a lot to learn but the one thing that stands out from my experience is this;
If all you do is strum a few chords and play clean then bandwidth will not be much of a problem BUT the moment you want screaming od/distortion then wide bandwidth will just destroy any sense of magic mojo.
This goes for ALL types of Electric guitar styles, from Country to Metal they all require some tweaking to the tone shape and bandwidth when a lot of distortion is required.
----
Others here are for more teck savvy and maybe able to expand on the magic of transformers for you.
Merry Chrissy to everyone, Phil.
« Last Edit: December 25, 2021, 02:58:43 AM by phatt »

willpirkle

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Re: newbie question about cranked amp overdrive
« Reply #11 on: December 25, 2021, 09:45:42 AM »
All great points Phil!

If anyone wants to study this concept further, check out the Peavey super-distortion patent (see Fig 3)

https://patentimages.storage.googleapis.com/66/73/f3/f482d05a548730/US4811401.pdf

You can legally build stuff from patents for your personal education/edification. If you pull out the distortion circuit, it makes a killer distortion pedal. Add pre and/or post distortion filtering of your own design for a personalized distortion box that no one else has!

Happy holidays, and thanks for an awesome website Joe and for all the great contributions from the power-posters. Here’s to a rockin 2022!

Will

dmfp123

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Re: newbie question about cranked amp overdrive
« Reply #12 on: December 25, 2021, 02:57:48 PM »
YES! An answer at long last... but of course it involved unobtainium :/

dmfp123

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Re: newbie question about cranked amp overdrive
« Reply #13 on: December 25, 2021, 03:01:42 PM »
Would this work? 20 watts is about perfect...

https://www.ampmaker.com/shop/0-190-275v-20w-power-transformer/

Enzo

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Re: newbie question about cranked amp overdrive
« Reply #14 on: December 25, 2021, 05:56:04 PM »
Did I miss something?  The transformer you link is for a tube amp.  It has a 6v winding for heaters, and a high voltage winding for the B+.   Not suited to a solid state amp.