The sound of my amp got thinner and brighter after I put the chasis into the combo!!!

[pdf64]

To eliminate some variables, connect the Pro Reverb speakers.
Then compare whether it sounds any different with the chassis in the cab or not.
Pete

[Alan0354]

What are the chances that the magnetic field of the power transformer (or even just the core iron) is interacting with the speaker's magnetics'? are they in close proximity? Just a thought

Not closer than a typical small combo. I would say the OT distance is normal from the speaker.

[Alan0354]

To eliminate some variables, connect the Pro Reverb speakers.
Then compare whether it sounds any different with the chassis in the cab or not.
Pete

I did not compare with the chassis in or or. But I did play with the Pro Reverb speakers while the chassis was inside and it sounded normal and thick. In fact it used to be thinner than the KMD cabinet when the chassis was out, but when the chassis was in, the Pro Reverb speaker sounded thicker. So I would say it does not matter whether the chassis is in or out, it's the acoustic problem that affect the sound, not electrical.

[Alan0354]

Well, the amp is back in the cabinet and all finished. The resonance circuit works wonder. Only there is a very slight pop or click when switching channel because I have a relay to switch the resonance circuit so I have separate resonance control for the clean and OD channel. The relay is in the power amp after the mute circuit. But it is so slight that you have to be completely quiet to hear it, no more than any foot switch of a pedal.

All in all, I call this a big success on my first build pretty much from ground up. Now I am going to concentrate on a Marshall build. Now I am going to have to slowly start shopping for a speaker that suit for Marshall, also an OT. This one is going to be with power scaling, EL34. But the front end will be the same as this one to start out as a starting point. Then cross my finger to improve it for Marshall sound.

[Alan0354]

I just completed my Marshall build, clean up the chassis, put it in the cabinet and test. It becomes very bassy and darker!!!! The amp have not change, I have A/B speaker switch, the amp sounds exactly the same as before in the other speaker, just when I put the chassis into the combo, the combo becomes bassy!!!!

This is just great, one amp I had to put in the resonance, and this one I have to work on it to remove bass!!! this is no win, you can't work on the amp and put it into the combo every time. You work on the amp on the table, then the sound changes when you put into the combo!!!

[frus]

you can't work on the amp and put it into the combo every time.

unless it's a tweed amp

[Chuck H]

I just completed my Marshall build, clean up the chassis, put it in the cabinet and test. It becomes very bassy and darker!!!! The amp have not change, I have A/B speaker switch, the amp sounds exactly the same as before in the other speaker, just when I put the chassis into the combo, the combo becomes bassy!!!!

This is just great, one amp I had to put in the resonance, and this one I have to work on it to remove bass!!! this is no win, you can't work on the amp and put it into the combo every time. You work on the amp on the table, then the sound changes when you put into the combo!!!

Perhaps when the amp went back into the combo it became bassier because the cabinet is now closed where it wasn't before (less phase cancellation in the room) and the internal dimensions are now concurrent with the speakers resonance. I'd call this a happy accident. Usually there's not enough bass in combos and you need to turn it up to the edge of farting to get all you can. If the amp sounded good OUT of the cabinet, but now has MORE bass that's a win Unless it's honking at only a specific frequency (somewhere between 60Hz and 90Hz). That would be a speaker/cabinet issue. You can't fix that with circuit tweaks. A speaker with a very different resonant peak could fix it. Possibly a port in the front baffle, a change to the size of the rear baffles or both.

This might be a topic for a new thread if it doesn't resolve quickly. This IS a different problem and a new thread offers members access to the information when searching. The forum has a ton of members that just lurk.

[g1]

I think you need to build a dummy chassis or baffle out of wood or something to take up the space where the chassis goes.
In your first post, you mentioned using phone books or something, and said it made a difference. Were you still doing that now?

[Jazz P Bass]

I just completed my Marshall build, clean up the chassis, put it in the cabinet and test. It becomes very bassy and darker!!!! The amp have not change, I have A/B speaker switch, the amp sounds exactly the same as before in the other speaker, just when I put the chassis into the combo, the combo becomes bassy!!!!

This is just great, one amp I had to put in the resonance, and this one I have to work on it to remove bass!!! this is no win, you can't work on the amp and put it into the combo every time. You work on the amp on the table, then the sound changes when you put into the combo!!!

Is this not the opposite of the original post?

[Alan0354]

Is this not the opposite of the original post?

Yes, that's the frustrating thing!!!

[Alan0354]

If the amp sounded good OUT of the cabinet, but now has MORE bass that's a win Unless it's honking at only a specific frequency (somewhere between 60Hz and 90Hz). That would be a speaker/cabinet issue. You can't fix that with circuit tweaks. A speaker with a very different resonant peak could fix it. Possibly a port in the front baffle, a change to the size of the rear baffles or both.

Ha ha, problem is with such a small cabinet, the bass really does not sound very good like the ones with big cabinet. It is almost boxy even though I really braced the cabinet up with 2 X 2 all around. Yes, it sure doesn't sound thin!!! I already have the WGS Veteran 30 which is very mid heavy already.

[Alan0354]

For the clean channel my amp is some what similar to 59 Bassman, I have to increase the treble tone cap from 250p to 390p and 0.47uF parallel with the 820 ohm on the second stage. I had to remove 10uF from the cathode in the last stage of the gain channel. Now it's much better. The heavy bass do make it sounds very good when playing the bridge pup. I do remember a lot of the amps I tested in GC were lack of bottom. So I guess I am happy. It no longer have the tubby sound. I still think the bracing of the cabinet improves the bottom. Man, did I braced up this cabinet!!!!

But it's just funny the more I improve the layout, the more bass I get. Maybe with bad layout in the test bed, the higher frequencies are more prone to coupling. I really work on the layout of this one, it gets even more bassier.