Strange old Tube compressor questions?

[hereforever]

I went ahead and changed C1, C2, and C3 to Does the last remaining coupling cap .005uf C5, between the 12AX7 and the output tube, not affect the bandwidth in the same way? Would I be better off swapping that one out as well?

It's hard to read the schematic but C2 looks like a treble cut?

C1, C3, and C5 are all coupling caps and, yes, lower values for these will increase the low rolloff frequency

 

[abbey road d enfer]

It's hard to read the schematic but C2 looks like a treble cut?

Yes, it's a RF/ultrasonics low-pass filter at 50kHz. The capacitor is probably good for another century of service.

 

[mjrippe]

Yes, had to go back and check but I did say C1, C3, C5.

 

[emrr]

You will find thump to be an deal-breaker. Don't remove those coupling caps, parallel others across them until you find the limits first.

 

[AardvarkBry]

Yes, had to go back and check but I did say C1, C3, C5.

Yes you’re correct. I misspoke, or miss analyzed the schematic.

 

[AardvarkBry]

You will find thump to be an deal-breaker. Don't remove those coupling caps, parallel others across them until you find the limits first.

I replaced the caps Sunday, and have been recording with it. The thump is nasty, but as long as I keep it from over compressing it doesn’t come into play. The only time it thumps is when the magic eye fully closes. I have this Arturia Audiofuse 8Pre, that has surprisingly great preamps. They blow my Apollo pres clean out of the water. There is a send and return, so I hook up the send to the comp, followed by my White Instruments 4220, then to the return. I have found I can have a lot of control over the thump by manipulating the gain of the pre, or even engaging the pad if need be, and also by cutting frequencies on the passive eq. My favorite way of using it so far, is to have minimal gain on the pre, and turn up the comp dial until only medium to hard spikes are compressing, but well before it thumps. I’ll hit it as hard as possible, just to make sure it’s not going to thump. Then I crank the hell out of the output, and I can get anything from a nice vintage vibe to super grimy mayhem.

the HPF was just untenable, and it still thumped regardless. Swapping those coupling caps and adding the input transformer made a monumental difference! Before, the bass sounded pretty nice, but when I recorded vocals and drums, it just sounded so thin and wimpy, no matter how I set it. My best hope was to just set it for nuclear, and go for a trash can vibe. After changing those caps it’s got a nice, full, robust punch that I was looking for.

 

[AardvarkBry]

Yes you’re correct. I misspoke, or miss analyzed the schematic.

But it did indeed swap C1, C3, and C5

 

[Stacey Plays Bass]

I have one of these arriving tomorrow, this was such an awesome thread to discover! I'm also primarily a bassist, very stoked!

I was wondering if you'd done any further mods, or have any suggestions for my tech.

This one with multiple time settings looks like a cool mod:
https://reverb.com/item/37040140-central-electronics-gc-1-valve-compressor

Thanks very much!