SE Z5600 a

[RoadrunnerOZ]

That valve is a lower gain than the one you’re replacing - it’s not going to sound the same either as the correct one new. The old one may be down in performance and gain due to age - they gradually lose response as the cathode wears out from erosion of the metal surface resulting in uneven firing of electrons.

 

[spottydog10]

Any suggestion on a replacement valve?

 

[RoadrunnerOZ]

Bugera ECC83A
https://www.bugera-amps.com/product.html?modelCode=0710-ACL

 

[spottydog10]

Bugera ECC83A
https://www.bugera-amps.com/product.html?modelCode=0710-ACL

I can see the 83s but not the 83a - will it do the same job? Thanks.

 

[RoadrunnerOZ]

Maybe contact SE

 

[RoadrunnerOZ]

http://store.drawmer.com/index.php?route=product/product&product_id=164

 

[RoadrunnerOZ]

Would pay to check that it is indeed the A version they are selling. From what I can make out this has a better bottom end compared to the standard ECC83/12AX7 but these may be hard to get.
The main thing is to get the best tube for low noise, microphonics and frequency response - the Mullard 12AX7 Reissue or the Preferred Series 7025 seem to be top performers:

https://www.thetubestore.com/12ax7-tube-reviews-chart

https://www.evatco.com.au/12ax7-comparisons/

 

[kingkorg]

Blindly shifting tubes without knowing what's going on in the circuit is IMHO waste of time. What if the mic is cathode out? What would 12ax7 vs 12ay7 do to affect the gain in that case? What if the mic is specifically designed around 12ax7? Anyway, I digress, this is not the case with this mic.

Those capsules have weaker low end than Røde NT1 to begin with. How much low end loss are you experiencing? What kind? Is it cut, or just attenuated. You can make a vocal take, side by side with SE and your Røde, and post them here. One take, simultaneously, same source, distance... It could easily be that mic just sounds that way.

 

[Khron]

What if the mic is cathode out?

Oh, it definitely IS.

https://groupdiy.com/threads/se-electronics.70694/post-901366

 

[RoadrunnerOZ]

If it’s been dropped while going the tube has likely suffered anyway and it looks like it had a heavy one from that crack in the capsule base.
Edit: SE only specify 12AX7 on their specs for this mic with no addendum.

 

[kingkorg]

Oh, it definitely IS.

https://groupdiy.com/threads/se-electronics.70694/post-901366

My fault, i meant one stage voltage follower where gain of specific tube wouldn't make a world of difference...

Also with this specific SE topology swapping tubes between different types can create all kinds of frequency response quirks, weird interactions with the transformer, boosts, cuts, resonances...

Off course one might like the results going by ear, but certain issues could appear under different conditions not accounted for initially.

 

[RoadrunnerOZ]

Every 12AX7 sounds different from manufacturer to manufacturer and even from tube to tube. I’ve heard dramatic differences in guitar amps and tube pedals with a change to superior tubes. Had one amp in where the microphonics were so bad the owner couldn’t play it loud - he’d got tubes cheap from eBay and they were really bad.

 

[Voyager10]

This is a multi-pattern mic, yes?

Does it sound the same in omni or figure-8 modes, talking into the 'back' of it? This will test the rear half of the capsule.

If it sounds good, a quick "fix" is to turn the capsule round, change the wires over, and use it just as a cardioid mic. If it's no different, it suggests the capsule is OK and the fault is elsewhere.

Looking at the circuit (it's the -ii variant) the most obvious single cause of low bass would be C5 going open circuit. How are your soldering skills?

 

[Khron]

Looking at the circuit (it's the -ii variant) the most obvious single cause of low bass would be C5 going open circuit. How are your soldering skills?

"Replacing the electrolytics" is well over my head I'm afraid

Ehrm...

 

[SoundBlaster]

I'm betting on a mechanical issue. That crack could be associated with something that inhibits diaphragm movement. No free movement, no bass..

 

[Khron]

That crack could be associated with something that inhibits diaphragm movement. No free movement, no bass..

That would make oh-so-much-more sense if this was a dynamic mic. Where there's actually meaningful diaphragm displacement.

Here, where said displacement is measured in microns(!!!), it's a teensy bit less likely. And since there's no notable accumulation of dirt mass visible on the diaphragm, that's quite unlikely to be the issue. If that was the case, you'd get noticeable amounts of extra noise, before you lost bass (imho).

 

[RoadrunnerOZ]

If the capsule metal frame is distorted in any way there would be uneven tension on the diaphragm - as I noted before in #19 & #30 the mic looks like it took a heavy hit enough to cause that crack. The plastic cracked at the midpoint between the mounting bolts indicates the capsule has tilted either backward or forward enough to distend and crack the mount which in turn could make the ring frame integrity suspect (as well as the tube and possibly the pcb which could have cracked) but it would be likely the plastic mount bore the full brunt of the impact. Really need to release the capsule from the frame and check the ring edge surfaces for true flat - any out of true deformation will unevenly tension the diaphragm and may reduce low frequency performance but it would take a lot of force and leverage against something immobile to do that. You would notice a sonic difference between front and rear in fig 8 setting if that were the case.

 

[RoadrunnerOZ]

You’d also see bulges or dips where the mounting bolts go into the ring frame if it were damaged. Looks pretty flat from the photo.

 

[spottydog10]

As kingkorg suggested here is a raw vocal take recorded simultaneously to compare the two mics.
Distance to mic was about 8 inches.

Rode NT1a


SE Z5600

 

[kingkorg]

Every 12AX7 sounds different from manufacturer to manufacturer and even from tube to tube. I’ve heard dramatic differences in guitar amps and tube pedals with a change to superior tubes. Had one amp in where the microphonics were so bad the owner couldn’t play it loud - he’d got tubes cheap from eBay and they were really bad.

I believe you, but these are microphones, and there's a diference between simple cathode voltage follower impedance converter and multiple gain stage guitar amp. Can't really be compared other that both use tubes. And even then the tone diference comes from tube's interaction with other components, rather than inherent specific tube sound.