Author Topic: F-2B: Ch1 hotter than Ch2 (Read 257 times)

pace · « **on:** January 07, 2014, 01:54:41 PM »

Ok, this is bearable, but just noticeable to drive me nuts.

I've A-B'ed both channels, swapping out everything~ cables, tubes, power amp channels, stereo, mono, etc etc? and it's something in the actual circuit. Ch1 is always about 1.5db louder than Ch2. I have yet to take a meter to it, so any help as to where to start, and maybe what voltages I should be seeing would be great!!!!

P.S., the only components that look like they're from two different batches are the Midrange 10K pots.

slawie · « **Reply #1 on:** January 09, 2014, 01:19:14 PM »

Have you tried raising or lowering the pickup height?

pace · « **Reply #2 on:** January 09, 2014, 01:39:11 PM »

Thanks Slawie, because the end result that I'm hoping for is to run my series instruments through the rig w/out any differentiation between the two channels..... but I haven't gotten there yet..... For now I'm running all my mono guitars into an A/B box going to each channel of the F-2B. Even if I jumper a mono instrument from ch1 to ch2 , ch1 is still louder.

So in a nutshell, no, I haven't adjusted p/up height, because my series instruments haven't factored into the equation yet....

edwin · « **Reply #3 on:** May 28, 2014, 01:29:41 PM »

Any luck figuring this out? I've noticed that my channel 2 is louder and cleaner sounding that channel 1. Channel 1 has a kind of blanket over the sound. I've swapped tubes, cables, etc. I'm thinking maybe the aging caps in the signal path (it's one of the ones made in SF with red capped knobs).

pace · « **Reply #4 on:** June 21, 2014, 06:12:55 AM »

I still can't figure it out, and I've had no time to really check into it....I'm thinking either the padding resistors, or the summing resistors may have deviated from their values....

hieronymous · « **Reply #5 on:** June 23, 2014, 09:14:07 AM »

Not sure if I knew this before, but according to the manual, Channel 2 has a 6 db pad.

Actually, the grammar in the old manual is terrible - it says Inputs # 2 provide 6 db pads. Both inputs # 1 and # 2 on a channel may be used simultaneously, too. In this case both signals are resistively mixed in equal proportions. Does that mean if you use both channels at the same time then the 6 db pad is defeated? Anyway, hope this helps!

edwin · « **Reply #6 on:** June 23, 2014, 10:27:33 AM »

I finally hooked up my F2B to Metric Halo Spectrafoo via a ULN-8 to see how it matched up and it turns out that my F2B is actually pretty much right on. After further investigation, I discovered that my power amp has a channel which seems off. The manufacturer seems to think it's the LP/HP/full range filter switch.

David Houck · « **Reply #7 on:** June 23, 2014, 11:07:33 AM »

Harry; you're mixing up the terms channel and input. There are two channels, A & B. Each channel has two inputs, 1 & 2.

It is the input number 2 on each channel that has the 6db pad. If you plug two instruments in inputs 1 & 2 on channel A, then the inputs are summed so that the 6db difference in input gain is eliminated.

If you plug two instruments into inputs 1 of both channels A and B, then nothing is padded.

If you plug two instruments into inputs 2 of both channels A and B, then the signals from both instruments meet a 6db pad.

hieronymous · « **Reply #8 on:** June 23, 2014, 12:30:33 PM »

Thanks Dave - I got confused! That's why they were using the plural for inputs and pads - it all makes sense now! Should have looked at the manual while I had my F-2B in front of me!

David Houck · « **Reply #9 on:** June 23, 2014, 01:17:23 PM »

pace · « **Reply #10 on:** June 23, 2014, 04:00:28 PM »

Reading the thread on the main page, and Dave's response is what made me go to the PDF, and also this thread... But ch B is lower regardless of tubes, power amp channels, patch cords, etc etc