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Old 27th February 2008, 06:55 AM   #1
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Question Electrolytic to film - Retain the bypass in coupling app?

Hi everyone,

I have a question that I know someone on the late night crew can probably help me with.

Say I have a certain commercial preamp that has a 50V 22uF bi-polar electrolytic bypassed with a .01uF poly film and I want to remove electrolytics in the signal path.
I have (5) 4.7uF WIMA M.polyester that I can parallel for about 23.5uf of film cap to get rid of the electrolytic.

My question is, do I need to retain the .01uF poly film.
I assume the polyesters are good to the higher frequencies that the electros are not - and bypassing is normally avoided when it is not necessary...

Any help or suggestions are greatly appreciated

Hafler
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Old 27th February 2008, 07:20 AM   #2
gootee is offline gootee  United States
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Default Re: Electrolytic to film - Retain the bypass in coupling app?

Quote:
Originally posted by HaflerFreak
Hi everyone,

I have a question that I know someone on the late night crew can probably help me with.

Say I have a certain commercial preamp that has a 50V 22uF bi-polar electrolytic bypassed with a .01uF poly film and I want to remove electrolytics in the signal path.
I have (5) 4.7uF WIMA M.polyester that I can parallel for about 23.5uf of film cap to get rid of the electrolytic.

My question is, do I need to retain the .01uF poly film.
I assume the polyesters are good to the higher frequencies that the electros are not - and bypassing is normally avoided when it is not necessary...

Any help or suggestions are greatly appreciated

Hafler
Just a guess, but you probably wouldn't want the frequencies that the .01uF would pass, anyway. I could see 0.22uF or even 0.1uF, maybe, but not 0.01uF. There should be a lowpass RF filter, for the input, anyway, which would probably remove whatever a 0.01uF would pass. I'd at least try it with no smaller bypass cap connected.
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Old 27th February 2008, 07:56 AM   #3
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Hi Tom. Always nice to meet other nocturnals

The input cap is a SEACOR 250V wound metallized .47uF polypropylene. It is stock, the only thing I have that I could swap is a Panasonic ECQ-P or a 1uF Radio Shack film that is highly recommended. I doubt I need to go to the trouble, the Seacor has always sounded fine and it is stock - that's usually good with a Hafler.

I suspected that the .01 was unnecessary with the change from electro to polyester. Film at any value works to higher frequencies than any electro.

Thanks!

I will post immediately if I hear any significant difference over the electrolytics. Cross your fingers...
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Old 27th February 2008, 08:31 AM   #4
gootee is offline gootee  United States
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Quote:
Originally posted by HaflerFreak
Hi Tom. Always nice to meet other nocturnals

The input cap is a SEACOR 250V wound metallized .47uF polypropylene. It is stock, the only thing I have that I could swap is a Panasonic ECQ-P or a 1uF Radio Shack film that is highly recommended. I doubt I need to go to the trouble, the Seacor has always sounded fine and it is stock - that's usually good with a Hafler.

I suspected that the .01 was unnecessary with the change from electro to polyester. Film at any value works to higher frequencies than any electro.

Thanks!

I will post immediately if I hear any significant difference over the electrolytics. Cross your fingers...
<grin!> Hi. Yes, I'm half-nocturnal, lately at least. It's probably an hour later, here, though (~3:30 now). So it's now officially past my bedtime. :-)

Fingers crossed.
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Old 27th February 2008, 12:32 PM   #5
AndrewT is offline AndrewT  Scotland
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Tripath Input Coupling Caps
Hi,
have a read of this.
They are finding that tiny multiple bypasses are beneficial.
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Old 27th February 2008, 09:13 PM   #6
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Hey AndrewT,
In fact, I have read and reread that thread with great interest. Thank you for adding the link to this thread (I found it researching EPCOS caps...).

The thing is, they are talking about input coupling caps.
The stock input cap on my unit is a 250V .47uF MPP that I do not have immediate plans to experiment with, but if I do, that thread has me very curious about the Radio Shack 1uF films.

What I am hoping to do is replace an output coupling cap arrangement that consists of a 22uF 50V BiPolar electrolytic bypassed with .01uF 100V MPP.

In case anyone would like to know, it is a DH110 preamp and I am talking about C21 and C22. Schematic at Hafler.com

Except for a couple huge 10uF MPP caps, the best alternative that I have found are little WIMA MKS2 50V 4.7uF with 5mm lead spacing. I can parallel 5 of these easy in the space that I have.
I should be doing this some time in the next 8 hours or so, I will post what I hear.
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Old 27th February 2008, 11:57 PM   #7
KP11520 is offline KP11520  United States
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Hi HF,

IMO, Input and Output caps basically do the same thing! They block unwanteds yet allow the wanteds in a balanced, pleasing sort of way at the handoff to/from another component!

Forget the 5mm spacing... that precludes 99% of your possibilities. We don't do this for convenience but rather to improve our listening enjoyment. You should see what AndrewT suggested I do with my CD Player's analog output stage. It doesn't look anything like the PCB and it is a great way to handle my oversized caps and some other improvements.

Also, look at some of Extreme_Boky's work he has posted with pictures. That will show the level of creativity some of these guys have to go through to get the most rewarding results.

Research what qualities different caps bring forward (there is a lot of info about this here) and narrow down to a few choices for what you are looking for. Then set up a controlled trial/listening/comparison test (don't forget to burn in the caps first or you won't be able to compare fairly). This is how you will find the best choice or choices if you choose to bypass. Unfortunayely there is no way around it. This is a very personal matter and things have changed quite a bit since that Hafler was manufactured. Now, there are more modding choices than you can imagine!

I hope you will actually enjoy it! Nothing is more satisfying than listening to your system bloom right before your ears as you make great mods and choices! But to get there, you have to do your Due Diligence!

Also, if you find a place to get Dweekie's Epcos 4.7uf caps, please let me know. I want in, I need four!

I have a DH500 that I used from 1984 until last Spring! Maybe I will mod it someday. I hear it has potential!

BTW, my kitten/cat is Nocturnal, would you guys mind if she posts on your threads late at night? It just may keep her out of trouble! Well at home anyway, who knows what she will stir up around here! LOL

Good luck! Keep us informed!

Regards//Keith
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Old 28th February 2008, 01:48 AM   #8
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Thank you for your generous reply, Keith, great to hear from another Haffie owner. Very cool of you to recommend some of the other posters' projects. I will be checking into those after this post.

Nocturnal cat... Hilarious!

I have not performed my mod yet, but I was just about to sit down and solder my MKS2 caps together so I thought I had better check this thread.

From what I have already read on the board, I know just about anything beats an electrolytic in the signal path so polyester or propylene is not such a big deal. I know polypropylene is ideal, but I figured I would give the MKS2's a try because: 1. They're film and 2. They're small (5mm like I had mentioned.)

If I parallel 5 of them and stack them on their sides, vertically, they will sit right on the stock circuit board using the space and original holes for the electrolytic.

One thing I have been wondering about is whether I could go with a smaller uF value when switching the electro to film. To tell the truth, I am looking to pick up a little in the bass floor, so I thought the 5 4.7uF caps at about 23.5uF would be a good replacement for the 22uF electro.
My two 5 cap groups have been selected with a precision cap meter to have matched sums of 24.22 and 24.19 uF - closest I could get.
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Old 28th February 2008, 04:49 AM   #9
KP11520 is offline KP11520  United States
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When you finish installing these, leave the Preamp on with a FM tuner hooked up to it with a strong station for the weekend (no amp required).Those caps will take at least 50 hours to get closer to sounding what they will settle to. No judgements before will be valid and they may continue to change up to 250 hours of use!

Not just about anything beats a Electrolytic. The Blackgate N and even better NX series have some following for a reason. They are worthy competition and some times can out perform a film cap, especially when bypassed properly. But the only way to find out is to try different caps and combos (bypassing). See what Dave is doing in the Tripath thread!

If you post the schematic of the output stage of the Hafler, the guys might be able to suggest different values (lower hopefully)for the Caps and (maybe higher) resistors (metal film) and tune up that output stage. Things are different since the early 80s. Also knowing what you are hooking it up to (Amp) might help to tune it for your situation!

Luna will be logging on sometime in the middle of the night. She always gets a burst of energy after midnight that lasts for several hours. Then she is up before us! How does she do it? Must be the cat food.... I'll have to try some!

Regards//Keith
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Old 28th February 2008, 07:17 AM   #10
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RATS! Oh life, what am I going to do with you....

As usual this project has run late (1 AM by me) because of unscheduled interruptions and humbug.

I have finished my 'supercaps' and am attaching a pic. For anyone that noticed, I did match the caps closer by flipping a couple -- 24.2 and 24.21.

Once finished they tested 23.3 each on a lower resolution scale.

I will attach the schematic soon enough as I would love advice concerning the muting JFETs. There are also (2) 4.7uF bipolar electros in that circuit that could use these WIMAs.

Concerning Blackgates:
Where the heck do you guys get these things? I have looked everywhere and cannot find a source for Blackgate caps - or many other high end caps.
Digi-key carries ELNA SILMICs but those are polarized electros for PS use.

To be honest, this is already a bit of an ongoing experiment. The original 22uF electros were IC caps. They sounded great and I still have them if I need to solder them back in one day.
The caps I am listening to right now are XICON non-polar electros and, to be honest, they sound quite good except that I would like a little more presence in the bass and mid bass. The XICONs have surprised me, though.

I read somewhere that electros can pass bass better than films - is this true? Anyone have an opinion?

Say 'Hey' to Luna, I really miss all of the cats and dogs I have had or lived with through the years. The best cat I ever knew was a runt born with one eye. She was awesome beyond words - her name was 'Kitty'.
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