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Messages - Jopyeweed

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The Newcomer's Forum / Re: CR112 guy here...again
« on: February 23, 2021, 10:00:45 PM »
Opps,,  :-[ Sorry I meant C4 which is .15 (150nF) This is just above the gain pot.
Then bass is wiped again at C11 .1 (100nF)

Small values there will wipe off a ton of Bass.

All 4 positions that I've noted need to be larger so rather than remove existing parts which might damage the PCB you can simply tack larger values on the track side of the PCB to test the outcome.
Maybe change one at a time so you know just where you are winning or losing mojo.

So that is C3,C4,C8,C11 can be larger.
C3 and C8 can be as large as 1nF.
As for C4 it's a tough one to guess as 470nF there might make the OD way too loud when S1 is closed. so suck it and see what happens.

As for C11 you may find that raising the value of R11 might help to wipe off extreme treble. Maybe try 4k7 or 10k.  you will have to lift at least one end of that resistor.

Just search for opamp design principles,  in this configuration the combination of R3 and R4 sets the gain and the value of C4 determines the bass roll off which of course raises the treble response of the circuit.
Same goes for the second stage;
This time R8, R10 and C10 set the gain and R11, C11 are switched which gives the treble boost.

If I remember,, in clean mode the first stage is lifted from ground Via S1 and that is likely not a very good idea,, others here might know more about that but to me it looks like it could be unstable. :-\
Phil.


Thanks Phil,

I'll experiment with adjusting those caps in the simulator. I use a mobile app called Circuit Safari. Then in a couple weeks I'm going to have some free time to tinker with the amp. Many thanks for your time and the detailed direction.

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The Newcomer's Forum / Re: CR112 guy here...again
« on: February 21, 2021, 11:11:39 PM »
As like any audio circuit, SS or Glass *Swapping actives is a mugs game*.
The issue is in the **Passives as they define the parameters of the actives.**

C15 is going to make it extremely bright ,,and then the bright switch C11 on top it will certainly annoy the poor Dog.
C3 and C8 can be much bigger to help but I believe I've suggested all this before. 8|
So until you change some or all of those it will remain ear shattering.
Phil.
Thanks Phil, I'm guessing you meant C13, the treble cap, rather than c15? The treble cap is the one I've never adjusted so far in my simulations.  :duh Thank you for the direction.

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The Newcomer's Forum / Re: CR112 guy here...again
« on: February 21, 2021, 11:05:46 PM »
What do you think these changes will do?  The original 50 watt part is plenty capable, the amp doesn't produce near that much.  Installing heavier duty parts will not increase the power output in the slightest.  Power comes from the power supply, not the output transistors.  Their 60v ratings are plenty for the 41v supply, of which neither part ever sees more than about 35v on peaks.  These amps are not known as transistor killers, so adding overkill ratings won't really improve reliability.

It won't be ANY louder, the parts ratings only tell you the maximum they can survive, not what will come out from them.  And as to preamp hitting downstream too hard, the signal is limited by the power supply.  The preamp runs on a single 24v rail, which the op amp has to center in so 12v either way from rest.  Minus a volt or so for limits and the signal cannot peak over about 11v.  NO stress on teh power amp.

To answer your question, yes the NTE guys will drop in place, though I consider it a waste of time.


I will say the power amp could be where your distortion lies, but not from being hit too hard.  You might have crossover distortion, and that is a matter of bias adjustment.  Yours is not adjustable other than by changing circuit part values around Q4.
Thank you Enzo. It was just a theory. I'll leave all that stuff alone.

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The Newcomer's Forum / Re: CR112 guy here...again
« on: February 21, 2021, 02:36:45 PM »
You might learn that a speaker can make or break how an amplifier sounds.

Think of it like this ..Say your car is riding a little rough  do you look at redesigning the suspension when all that is really needed is a set of tires?

nosaj
Thanks Nosaj,
I have tried an eminence swamp thang and the gold label eminence fender special design that I think they used to put in the hot rod deluxes. I was dead set on trying the cannabis rex next but am now leaning toward the Eminence Guit-Fiddle as it has a hemp cone but also reduced/flat mids in the 800hz -2k frequencies where the harshness seems to live. Maybe that'll be the one. Fingers crossed!

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The Newcomer's Forum / CR112 guy here...again
« on: February 21, 2021, 12:27:33 PM »
Hey everyone,
 I found a review online for my old Crate CR 112 that suggested upgrading the power amp transistors from TIP110/TIP115 to  nte2343/nte2344 and the preamp opamps to OPA 2134.  No other instructions beyond that. It looks like the nte2343/nte2344 combo is just a little more robust overall, and 80 watts vs 50 with the TIP's. Would these NTE's work as a drop in replacement in this circuit and if so what/ if any improvement would they really offer? I'm assuming it wouldn't really be much louder? (The watts vs db's ratio)

The main problem I'm having is what I believe is harmonic distortion coming from the boosting circuit in the feedback loop of the 2nd half of the 4558 opamp. Ear stabbing sound pressure harshness unless the mids and bright switch are off.
It actually sounds like piercing, whistling overtones. What I dont know is if the harshness is coming from the boosting within the opamp itself, or if the boosting from the op amp is hitting the transistors too hard downstream in the power amp causing harmonic distortion there. Hence maybe beefier transistors would help? Anyone have any ideas?

I've already had some good suggestions for mods to the first op amp loop in this circuit from forum members in the past, and after tinkering alot with the preamp circuit in a simulator, and learning to use a simulator in general, I have some plans for that section.  Many thanks for the help in the past. I'm using this amp circuit to learn about electronics. Thinking about this amp gives my mind something to do other than be anxious.   :-\  Of course, a hemp cone speaker might be all I really need, but then what would I learn?  ;) Schematic is in the manual attached.



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Amplifier Discussion / Re: Help with Crate CR112 Tonestack
« on: October 03, 2020, 12:47:07 PM »
Having found time,,,I just simulated the preamp up to C15 tone output,,
A couple of observations.
On Clean the bass response at the output of U1 starts with a hump at 2 hZ which is kinda silly.
But when drive is used the bass rolls off at a more sane 50~60hZ.
I can only assume this would create an obvious imbalance between clean and drive mode.
Maybe too much bass on clean and next to none on drive. In combination with the diodes D1,2&3 would likely be kinda harsh.

The mid control does little to create a mid cut at the classic 400hZ. so yeah proly not nice to play if you want a more fender tone. xP

I would first remove the diodes and use an OD pedal for dirt and just use the drive mode.
This will give the Amp a lot more clean headroom,, And leave the OD tricks for pedals which do a far better job.

If you need more bottom end up the value of C4.
As for the tone ,, you would have to rebuild it or I as mentioned easier to build an external tone pedal. 8|

Sorry  to say but if you try to turn your hamburger into a lobster you may only end up with a bad smell. ;)
Phil.

Hey Thanks for taking the time to look at this circuit! I'm sorry I just now saw this reply. I thought the thread was dead. Since my last post I've done some experimentation with an eq pedal to try to sus out the harshness. With the bright switch on, and the mids all the way off, bass on 2-3, treble on 6, the harshness is around 800 to 1k hz on the pedal. If I cut those frequencies a bit, leave everything else on the pedal flat, and boost the signal overall the bring back the volume lost by killing the mids...I can get pretty good results. Turns out the singing chiming sound I like lives in the mids not really the highs, around 2k maybe just above or below. I was always thinking I needed more high end, but what I really needed was less harshness. There really does seem to be some high frequency, piercing, almost artifact like content present in the mids between probably 700- 1.5 k or so in this circuit. It WILL stab you in the eardrum. A parametric eq pedal would probably be really helpful so I could sweep the mid scoop up or down to find the sweet spot. In addition I think maybe the Cannibas Rex speaker would be a better choice than the Swamp Thang I went with. As the Rex is known to tame harshness quite well. So it goes...
Thanks again!

7
Amplifier Discussion / Re: Help with Crate CR112 Tonestack
« on: September 03, 2020, 04:25:55 PM »
Thanks Enzo, now if I could only convince my spouse of this same logic. Try as she might to change me, I'm just a hamburger, I will never be...a lobster. :lmao:

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Amplifier Discussion / Re: Help with Crate CR112 Tonestack
« on: September 03, 2020, 09:24:09 AM »
Thanks Phil,

I may try to build your pedal in the future. In case you didn't see it I want to thank you for your detailed reply to my previous post about this amp. I didn't respond until some time later so you might not have seen it.  :dbtu:

I still would like to be able to plug into this amp though and have it sound good straight away. I did put an eminence Swamp Thang speaker in it which does help but of course, doesn't really change the essential character of the tone. Maybe a Cannibas Rex would tame the harshness. Sigh, this amp...I've had better amps, a hot rod deluxe, a 66 bassman, both of which I was forced to sell in leaner times. This one stays with me because it has no resale value so... I keep finding myself playing through it again and again and hating it.  :grr

Thanks again,
-Shawn

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Amplifier Discussion / Help with Crate CR112 Tonestack
« on: August 31, 2020, 01:48:54 PM »
Hello everyone,

I am wondering if anyone can help me with this tonestack.
 
I basically want to convert to a standard fender tonestack with the component values adjusted for SS. As I understand I can divide by 10 for the resistors eg. 250k for tube = 25 k for SS. Is that true? I read it somewhere and cannot find the original source now. What about the caps though... how does one convert the values for those?

I would like to load this tonestack into the Duncan tonestack calculator but it is not a perfect match in its layout. The .22 cap is located on a vertical line between the bass pot and the mid resistor, rather than on the horizontal lines, and there is only one cap instead of two. My limited knowledge doesn't know how to interpret this. How could I plug this into the fender format in the Duncan calculator so I can see the frequency response? As the calculator wants a cap on each horizontal line in the tonestack. Are both the Bass pot and "mid" resistor to ground below that sharing that .22 cap?

As I understand it the mids in this amp are active as they run back through the feedback loop in IC1. My idea was to just jumper the mid pot or introduce a fixed resistor to negate this active section...and then hook the leftover unused mid pot up for a passive mid at the bottom of the tone stack proper, for a more traditional mid section ala Fender. Attached is the full tone section of the schematic, as well as just the tonestack for reference.

Many thanks to anyone who would like to help

-Shawn

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Amplifier Discussion / Re: Crate CR112 tone stack
« on: January 30, 2020, 01:16:00 PM »
Hey Phil, I dont know if you'll see this but I just wanted for the record to thank you for your reply and efforts to help. I tried some more recently with the amp to see if the tone stack responded differently while in the OD channel. It seemed about the same but as I recall you said you would need to lower C3 in order to notice any effect anyway. I haven't opened it up to see if its grounded despite what the schematic says. As I keep playing through it I think I am getting a good enough sound and a speaker upgrade will probably make the most difference. I should probably relax and try that when I can afford it, and let it be what it is. Many thanks again!

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Amplifier Discussion / Re: Crate CR112 tone stack
« on: January 08, 2020, 04:38:16 PM »
Disregard my last post, I realize thats probably kind of alot to explain.

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Amplifier Discussion / Re: Crate CR112 tone stack
« on: January 08, 2020, 11:19:18 AM »
Would anyone be willing to tell me what kind of tone stack is in this amp? It doesn't really correspond well to any of the paradigms it seems. Is it just a modified Fender/vox/marshall? Active or passive? I'm trying to learn about electronics by modifying pedals and studying schematics. I'm in no hurry to hack into my amp unless absolutely necessary for safety reasons. I want to stay in the 9v world as much as possible. But I enjoy studying and thinking about it, reading tutorials and things online, etc. Apologies for the download requirement on the manual/schematic above, I couldn't figure out a way to do it otherwise on mobile.
Thanks again.

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Amplifier Discussion / Re: Crate CR112 tone stack
« on: January 06, 2020, 12:08:37 AM »
Thanks for the replies!
 To Enzo:
I will try to close the back a bit and see what that does. I never considered that. The amp has a Eminence designed fender speaker that probably came out of a deluxe reverb or a hot rod deluxe. I believe it is supposed to be a version of their legend model speaker. Overall the amp has always had kind of limited dynamics and a harsh, piercing mid range. Bass and treble are sort of weak. Not enough of either, although I'm using less bass these days anyway. I am going to get a long decay reverb tank at some point too as a big part of the sound I like I am starting to think comes from the frequencies the reverb accentuates and sustains. I am getting very close now that I am setting the dials the way I mentioned, but loosing alot of volume in trade. From what I can tell from the manual the tone stack is boost only and that all happens around 3-4 on each pot. Unfortunately to get the necessary DB's it seems you need to dime everything and that is not a balanced tone for me. Maybe a more efficient speaker will render those boosts more pleasantly.

To jazz p bass:
Will lowering that bright cap shift the brightness upward frequency wise for more presence and sparkle?

Many thanks!

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Amplifier Discussion / Crate CR112 tone stack
« on: January 05, 2020, 01:11:09 PM »
Hello all. I have a Crate Cr112 that I have been entertaining modding in the tone stack section. Overall the clean tone is sort of lower mid focused, I think. To get the sound I want I have to set the treble around 5-6, mids completely off or just a tiny bit. Bass around 3. I'm losing a ton of volume this way but it gets unpleasantly punchy anywhere north of that. My ideal clean sound is Jerry Garcia like, which is basically a twin reverb. I know, buy a twin reverb. Not an option unfortunately. The bright switch adds alot of character and the amp seems to come to life with it on but it is wayyy to harsh sounding. Sounds like a mid boost fat switch more than a bright switch.
Maybe just an efficient speaker like the swamp thang to counteract the volume loss and possibly audio taper pots would do the trick?

I once had an oxford speaker from a late sixties bassman cab that made the bright cap more usable.
Schematic and manual is here. Many thanks for your time if you want to look at it. The tone stack doesnt seem to really match anything in the duncan tone stack generator.

https://supportloudtech.netx.net/loud-public/#/asset/2383

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