Display posts from previous
Sort by

Re: Balls Effects / Balls Amplification

681 by Dr Tony Balls
Nate Dort wrote: Sun Nov 30, 2025 11:03 am Did you try connecting R111 and C21 to ground like the original schematic? Connecting them 9V isn't going to do anything, as any DC would be blocked by the capacitors. It makes much more sense to connect them to ground, like a Twin T notch filter.

BTW, there are some good shots of the front and back of the PCB over in this thread on TGP: https://www.thegearpage.net/board/index ... r.2591523/
Yeah I know R111and C21 should be connected to ground, but just for grins I tried both B+ and Ground and there was no real noticeable difference. I'll try later to make some changes and catalog what makes differences in terms of noise.

I'll also take a look at that TGP thread and see what I can glean. Also on Wednesday i'm supposed to be receiving a Freedom amp for repair so if its the right one I can trace and take measurements.
Website: http://ballseffects.com/
Instagram: https://www.instagram.com/thetonyballs/

Re: Balls Effects / Balls Amplification

682 by Dr Tony Balls
So I cant glean much from the TGP pics other than to say I cant find any obvious mistakes from the schematic.

Otherwise i'm pinpointing the power supply rail as that seems to make the most noise difference. That R-C network is weird for a pedal circuit with DC supply, but common for an amp where you're rectifying and smoothing AC. It shouldnt be needed for a DC supply application. BUT it also shouldnt hurt anything I dont think. Removing C108 hushes most of the noise but also makes the circuit sound dark and lowers gain. Removing C111 does the same but to a lesser extent. Its almost reminiscent of adding/subtracting a cathode bypass cap.

It should be noted that for testing i'm using 2N3904/2N3906 transistors instead of 2N5133/2N5138, but that should be fine.
Website: http://ballseffects.com/
Instagram: https://www.instagram.com/thetonyballs/

Re: Balls Effects / Balls Amplification

683 by Nate Dort
C111 and C108 are just bulk filter caps. They should have no impact to sound unless the power supply is really noisy.

If it's squealing, it's probably oscillation, likely just from it being on a breadboard. A proper layout without a bunch of antennas (i.e. breadboard connections) hanging off of the high gain nodes should quiet it down.

Kinda tempted to build one myself. May sim it in LTSpice first.

Re: Balls Effects / Balls Amplification

684 by Dr Tony Balls
Nate Dort wrote: Mon Dec 01, 2025 6:19 pm C111 and C108 are just bulk filter caps. They should have no impact to sound unless the power supply is really noisy.
Right, but that's what's driving me crazy. They shouldnt need to be there with a decent DC source and they certainly shouldnt impact the sound other than to kill some hum. But they're actively adding a lot of gain and noise when I put them in (especially C108), which I cant figure out. I can quiet *most* of the noise by adding a filter cap on the supply, but not entirely and its still sounds awfully ragged like its too high gain.

I'm using a pretty standard Boss PSA-120 supply, but i've tried others and they dont change anything. I want to chalk it up to breadboard gremlins but its too wild for that. I'll record a sample in a bit.
Website: http://ballseffects.com/
Instagram: https://www.instagram.com/thetonyballs/

Re: Balls Effects / Balls Amplification

685 by Dr Tony Balls
Quick recording with four parts:

1. C108 and C111 removed
2. C108 inserted
3. C108 and C11 inserted
4. Added a 220µF across the DC source

https://drive.google.com/file/d/1pEV3nN ... sp=sharing

The tone control is set kinda bright which accentuates the squeal. The bite control is set high which accentuates and also changes the pitch of the squeal (I think changing the notch of the twin T). Still it makes no sense to me why inserting C108 (and C111) adds so much gain and output.
Website: http://ballseffects.com/
Instagram: https://www.instagram.com/thetonyballs/

Re: Balls Effects / Balls Amplification

686 by Dr Tony Balls
Well to add some resolution here I *did* get a Freedom Amp on the bench and traced the preamp and its almost the same as the KiCad version that Nate posted. The only real differences are the bypass caps (C4 and C11 below) are 100uF instead of 50uF AND that there is 1000uF of filter cap hanging off of the DC supply. Adding this (or something like it) to my breadboard version shut the thing up pretty decently. I'm still not entirely sure why all that bulk capacitance is needed for this but it seems it is.

Image



I'll layout a prototype before long.
Last edited by Dr Tony Balls on Wed Jan 14, 2026 2:06 pm, edited 1 time in total.
Website: http://ballseffects.com/
Instagram: https://www.instagram.com/thetonyballs/

Re: Balls Effects / Balls Amplification

689 by llllllllllllllllllll
Hi Tony, I had some mains hum in my ~10 year old Balls 30 head and ai traced it down to the preamp section as it went away when all 12ax7s were out - I was changing out different preamp tubes to see if it would go away - I think the 2nd preamp tube slot is microphonic because any tube in there responded to a chopstick tap, and less so in the 3rd preamp slot, closest to the power tubes.

Apparently I have no spare 12ax7s, or the ones I have are suspect, but I tried a 5751 in what I assume is V1 - its the preamp tube furthest away from the power tubes. Is that even used in the top boost section? The amp is sounding really good, still a bit noisy, I think I should probably clean the tube sockets and see if it magically gets better. Any issues using that tube in that spot?

Would you still happen to have a schematic for this thing? I think you’ve sent it to me before, but it was lost in the old PM system and I’m not seeing it in any of my files.

Re: Balls Effects / Balls Amplification

690 by Dr Tony Balls
llllllllllllllllllll wrote: Tue Dec 30, 2025 11:40 pm Hi Tony, I had some mains hum in my ~10 year old Balls 30 head and ai traced it down to the preamp section as it went away when all 12ax7s were out - I was changing out different preamp tubes to see if it would go away - I think the 2nd preamp tube slot is microphonic because any tube in there responded to a chopstick tap, and less so in the 3rd preamp slot, closest to the power tubes.

Apparently I have no spare 12ax7s, or the ones I have are suspect, but I tried a 5751 in what I assume is V1 - its the preamp tube furthest away from the power tubes. Is that even used in the top boost section? The amp is sounding really good, still a bit noisy, I think I should probably clean the tube sockets and see if it magically gets better. Any issues using that tube in that spot?

Would you still happen to have a schematic for this thing? I think you’ve sent it to me before, but it was lost in the old PM system and I’m not seeing it in any of my files.
Hey!

It's possible that a connection to the V2 socket has gone bad and that's why youre getting microphonics. Hard to say if that is related to the hum you're getting though. And a 5751 is fine in any position. It's just a lower gain 12AX7 (but a bit higher than a 12AT7).

Here's a schematic. V1 is the furthest away from the power tubes. Here's what they're doing:

V1 - first gain stage for both the normal channel AND the top-boost channel
V2 - cathode follower gain stage for top-boost channel
V3 - phase inverter used for both channels

Removing V2 will put a break in the top-boost channel, so if you pull that tube and things change, there's an issue in the top-boost channel.

Also I thought I had no photos of this build (somehow) but I found them and they're all here. Almost 10 years old!

Image
Website: http://ballseffects.com/
Instagram: https://www.instagram.com/thetonyballs/
Post Reply

Return to “Tech Room”

Who is online

Users browsing this forum: No registered users and 1 guest