Gates M5215 questions

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Antique Electronic Supply in the US carries CE brand capacitors. They bought all of Mallory's old machinery and manufacture multi-cap cans in the original values and dimensions. Pricey, but it's your best bet for fit to original holes.

https://www.tubesandmore.com/products/capacitors?filters=2341a2356

Another option that I've used often is to cut the can open and stuff it with modern, individual capacitors. Not hard to do, but time-consuming. However, if you're going for original look, it's a way to do it.

As far as values go, you don't necessarily need 30+30 uF - electrolytic caps have wide tolerances (usually +20%/-10%). 33uF will work fine.
 
The fact that you mentioned that the JJ's were "too wide for a clean replacement" made me think you're looking to preserve the original look. But to EMRR's point above, you definitely don't have to go that route if looks aren't the priority. You can just get individual 33uF caps and install them internally. Then just cover the old can cap hole. Wait - these are 5215s - so you dont even have to cover a hole! Just solder the caps directly to the boards! I've got a dozen of these and that's all I ever did with them.

Brain fart there for a sec.
 
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Hi Doug, Do you mean leave them out entirely? I thought they were for power supply decoupling & filtering. -Mike
Of course not, just that one seldom needs to retrofit exact mechanical designs, especially on little naked PCB's like this. I have almost never bought a new multi-section cap for 5x - 10x the money, it's rarely required.
 
Ok, just the wording was vague and I thought I was wasting time and money ;) With a modern supply the filtering is probably not needed, but decoupling would still be.

As most multi-sections are four or fewer, I save the mounting phenolic and retrofit it with modern caps and hot glue.
 

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Thanks for your answers. I was also wondering if I could skip them completely and have a super clean main PSU for all the modules.
i am not looking for the original look, I want to restore them properly and I am more interested in their sound :)

EDIT : TAD Gold Cap 33+33uF @ 450V axial capacitor
this one is cheaper, I think I will go with it.. it seems quite convenient / compact.
 
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Hi all

I will soon rack the preamps. I will use variable T Pads on the output, and I am trying to figure out what to do with the input. I thought a simple H pad with 10 and 20 dB att would do. But then I realized it may be interesting to be able to switch between 50 and 150 ohms primary,... and then the H pad wiring becomes a nightmare with the impedance change :)
I may have to go with a Lorlin rotary switch : 150 no att, 150 10dB pad, 150 20dB pad, 50 no att, 50 10dB pad, 50 20dB pad.

Any thoughts ? I don't have much mics with a 50 ohms impedance... but maybe it's still interesting tone wise. Or is it overkill ?
 
I realized it may be interesting to be able to switch between 50 and 150 ohms primary,...
You may want to try that before committing to a complicated wiring.
In my experience loading any source with too low an impedance never results in anything good.
I don't have much mics with a 50 ohms impedance... but maybe it's still interesting tone wise.
Remember that 50-ohm mics have never been meant to be loaded with ohms.
 
You don't need 50 unless you want a special effect or have 50 ohm mics.

You don't need output T pads unless you are feeding things that can't take +18. I suspect they are fully into overdrive well before that.

The output load will not be all that sensitive to exact loading with all the feedback. It's probably fine into 10K.

You should experiment for awhile before committing to extravagant switching options, you will find you only ever use 1-2 settings, ever. If you really need an output pad, probably a simple -6 switch (or similar) would be more than sufficient. Save yourself a bunch of wiring work and cost you won't ever use.
 
Thanks Doug, that's exactly why I asked here, haha !
What do you mean by "fine into 10K" ? modern 10K load ?
I intend to use them straight to converters, or sometimes to EQs, dynamics, etc...
I guess I need an input pad in case I use condenser mics, or dynamics on loud sources... so maybe a 2pos 10 - 20dB pad is enough.

I have no 50 ohms mics, but thought maybe as an effect it could be useful. If I am not mistaking it will very dark with a 200 to 600 ohms mic ?
 
You may want to try that before committing to a complicated wiring.
In my experience loading any source with too low an impedance never results in anything good.

Remember that 50-ohm mics have never been meant to be loaded with ohms.
thanks Abbey, I missed your answer for some reason...

You guys are probably right about the 50 ohms input... Maybe I should focus on mic selection and placement instead of fiddling with impedance haha.

I think the best is 0 / 10 / 20dB input pad, and 0 / 6dB output pad. I'll start with this !
 
Yes most pre like this are fine into modern 10k load. Higher gain too. Sometimes a more traditional load flattens response in a positive manner, but rarely needs to be as low as 600.

The gain trick here is varying the feedback resistor, maybe changing the feedback coupling cap to a larger value for settings with more feedback. You’d have to explore the practical limits.

50 ohm usually is all midrange.
 
At this point, I guess I am happy with the idea of fixed 40dB gain. Maybe in practical use I'll be tempted to play with the circuit, but right now I'd like to use it stock. If the 10dB pad is weird I'll go with 20 > the wiring is even simpler. Thanks for your input (haha)

I am recording a jazz quartet mid December and would love to use these 6 pres. It's a bebop style quartet, I'll use 6 mics tops, no headphones, nice room etc. I believe these pres might be suited for this type of recording :)
 
Why can't I wire a 600 ohm resistor all the time ? I understand it helps reducing ringing. Something I have noticed with my Siemens W295 EQs, depending on what they drive they can sound a bit harsh... But when correctly hooked up... just butter !
 
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