Caiman passive output mod revealed

[Ali Tait]

DiyHiFiSupply have Obbligatos at 47uF

[Clive]

DiyHiFiSupply have Obbligatos at 47uF

Am I right in thinking 0.47uF to 1uF would be ok for a preamp of 100k input impedance (actually 94.4k)?

[Puffin]

I am looking to do the passive mod to this particular 7520. Is there likely to be any problem if I attach the caps to the via's (where the orange wires are already attached)?
I intend to use the variable output to attach the passive caps so that I can swap between the two.

The op-amp board is attached by the two orange wires and I wonder if adding the 47uf caps (or whatever value I chose) will affect the active operation?

Any ideas?

[Ali Tait]

[QUOTE=Clive;138972]Am I right in thinking 0.47uF to 1uF would be ok for a preamp of 100k input impedance (actually 94.4k)?[/QUOT


Yes I think so Clive.Try it and see.Shouldn't do any harm anyway.

[Buggleskelly]

Thanks Ali, that's very useful info. As my preamp has a 100k input impedance it seems I can go the film route too, even paper in oil though I expect film to work out better. I have various 0.47uF and 1uF caps.

I've been doing the passive mod on my 7510 and I agree with Ali it's the biggest bang for buck mod

So far I've tried out 47uf : Silmic II's, Nichicon ES & FG & KZ, Fine Gold" MUSE, Black Gate FK's.

My fav's so far are the Black Gates which I'm still running on one 7510 and on the other I'm just plumbed in Claritycap SA Range 4.7uf jobbies and these are sounding really nice. I had them knocking around from one of my valve amp projects so I thought I'd give'em a go. They are soaking in so I'll have another listen tonight.

The outputs are strapped down with a 100K TAKMAN resistors and this feeding a Silk TVC, which a 12K load. So with the 4.7uf it'ss around 3hz cut off.

I've also replaced the 5V regulator with an LM317 as they lower noise but I really dunno if that's made any difference though. Need to swop back at some time.

Just take the plunge you won't regret it Have fun.

Cheers / Stevie

[HighFidelityGuy]

Hi Stan, I'm aware that technically they can be done in any order but what I'm wondering is whether, say doing the passive mod on an otherwise unmodified 7520 might for instance show up noise from the standard regs. There are times when too much resolution downstream shows up upstream components. I'm thinking about synergy, rather than whether it technically works.

I would also say that the passive output mod has given me the biggest improvement overall. That's using very cheap caps as well, so the bang for buck value is huge. You could of course use very expensive caps which may work even better but it's not essential. I see what you're saying about the possible issue with upgrading downstream components first. The passive output does allow more detail through as well as improve the dynamics, so you will be letting more noise through if you don't upgrade the regs. However, I think the improvements outway this, especially if you're going to be upgrading the regs later anyway.

Also, the Murata regs don't affect the sound signature as such, they just improve the signal to noise ratio. So seen as the passive output caps can affect the sound signature and can take quite a bit of running in, I'd personally do the passive mod first. That way the caps can be running in while you wait for the regs to arrive.

[Clive]

Any reason not to try Black Gate 220uF 6.3v non-polars aside from possible charge/discharge thumps on power on&down? I just happen to have a pair.

[HighFidelityGuy]

Any reason not to try Black Gate 220uF 6.3v non-polars aside from possible charge/discharge thumps on power on&down? I just happen to have a pair.

Based on what others have said, I think this will depend on your amp. The roll off frequency at that capacitance rating will be way below 1Hz, so your amp may go into protection if it thinks it's been given a DC input. This will be dependant on how your amp deals with that situation though. Some have very little protection. A good amp shouldn't allow DC through to the speakers though, so there shouldn't be a safety issue I wouldn't have thought. You'll just have to decide if it's a risk you're willing to take.

[NRG]

Am I right in thinking 0.47uF to 1uF would be ok for a preamp of 100k input impedance (actually 94.4k)?

Clive that's fine, I'm currently using 0.47uF into 100K and there is no loss of Bass...

I would also say forget 'lytics and stick with film type caps they have a much more even response.

[HighFidelityGuy]

I've just taken delivery of some Mungdorf MKP 15uF film caps. Unfortunately I ordered the 33uF version but got sent the worng ones due to an error on the diyhi-fi.co.uk website. So watch out for that one. I've emailed them about the issue. I might give the 15uF's a sneaky try seen as I don't have to solder them. That should give me an idea of what to expect after I get them exchanged.