Why so bright?

[distorto]

I'm building a one channel 5e3. I've got one input with one tone and one volume. I currently have it hooked up like the tweed Harvard (5F10) I'm using 2 12ax7's but only 1/2 of the first one.

I have the wiper of the volume going to pin 2 of V2 and the wiper of the tone pot going to the coupling cap (0.1) and into pin 1 of V1 Basically just like the Harvard schem with 1/2 a 12ax7 instead of the 6at6.

My tone caps are standard .00047/.0047 and are hooked up correctly. My pots are both 1 meg. I've got an ungodly amount of treble. anything over 9:00 on the treble knob is too much. It sounds good with the tone rolled all the way down though. Also, It's still too bright with the tone disconnected. I noticed that on the Deluxe schem the volume and tone wipers seem to be reversed from that of the Harvard. I couldn't get it to work this way (the tone control added gain) which is why I tried the Harvard way.

Anyone have any ideas of what to look for to loose some of the high end?

[black_labb]

what type of speaker do you have it hooked up to? is it a speaker that you have used with other amps?

you sure you got the right coupling caps and cathode bypass caps? remember the cathode bypass is uf, not nf or pf

[distorto]

Thanks for the reply. I'm testing it through the Jensen 10 inch speaker in my 1964 Princeton which is fine. Also through a vintage Vox 2X10 cab. The coupling caps and bypass are correct. The caps are cheap though so I ordered Orange drops and I'll go over everything again and see if I've missed something.

It sounds pretty good at lower volumes but with the tone control above 9:00 it doesn't sound like it should. It seems to be most lacking in the midrange. The bass is there for the most part but as the tone control is rolled up it gets real bright on top and the middle vanishes and it starts to sound like a bad 60's solid state amp.

Thanks again for your reply.

[black_labb]

keep in mind those tone controls bypass the volume controls, so you get the same amount of high frequency passing through at very low volumes and high volumes, so when it is low, you need to adjust the tone pot accordingly, and when you turn up, the treble through the tone pot stays the same as on the lower volume. is it ok at high volumes?

[tubeswell]

That 5F10 lacks the usual fender 68k/68k hi-lo pas filter input arrangement with a 1M to ground etc. I wonder whether that might be having an effect on your all-round tone?

[distorto]

Hey thanks guys.

I think I may there. I had a slight wiring issue on the pots that I corrected and it sounds great. It now has that throaty midrange I knew was there somewhere. It's still a little "top endy" with a Tele but I can dime the tone knob with my LP Standard and Junior and the treble stays very musical. I'm going to swap the crappy coupling caps for orange drops and take a listen and see if it needs any more tweaking.

Tubeswell, I thought about that input arrangement as well. right now I have one 68k with a 1 meg across the jack. Am I correct in thinking this will be like the HI input on a Fender?

Thanks again for taking time to offer your input!

[Bruce / Mission Amps]

Now that you think you have the pots wired right, if you are only using one input jack then your 68K resistor should be 34K or equiv.
The 12AX7 in the first stage has much more gain so the amp will be brighter with respect to the position of the volume control.
You need to use a 12AY7 or lessen the gain of the first stage 12AX7.
Also, if you wired the pot like a standard two channel tweed 5E3, then the signal from the .1uf cap (anode of the first stage triode)... is going to the middle lug (the wiper) of the volume pot, and the attenuated signal from the volume pot leaves the pot from the outside lug to grid#2 of the second preamp tube.
If you wire like other tweed amps with only one channel, the signal goes to the outside lug first and the attenuated signal comes from the middle lug... going to the grid of your second 12AX7.
However, when played at a lower volumes, the tone will be a tiny bit brighter then the stock 5E3 configuration.
This actually can be a good thing as the single vol pot is not so sensitive and twitchy to level setting when wired like that.

[distorto]

Thanks for that. I'll stick a 34k on the input. I do want to get a 12AY7 in V1 eventually. I don't have one here. I do have a 12AT7 though so maybe I'll se what that does.

I settled on wiring it like the other Tweeds (Princeton, Harvard) This seemed to be the smoothest. The other way seems to add to much gain on the high end of tone control.

The amp seems to be really close to what it should sound like now. With my miss-wire it was really apparent that there was something wrong. It now has that classic, almost horn-like quality with humbuckers and P-90s. I think that changing the input resistor, putting a 12AY7 in V1 and the cap change ( I have a mish mash of cheap used/old coupling caps in there now) should take me the rest of the way.

Thanks again
Chris