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In Reply to: "Trash" it? My my, you two are being awfully tough on Pauly. Surely both of you understand that products... posted by jeffreybehr on April 24, 2007 at 09:11:47:
Hi.Read Paul's post again.
He gave me the impression of modifying the "passive RIAA section" by
avoiding "any couplers".Depending on the circuit design (hence the poster asked for Herron's schematic), removing any coupling capacitors (I assume) may affect the overall balance & accuracy of the RIAA EQ. This is not any tweaker should do without making very sure from the schematic if such coupling capactors should be removed.
Bob wanted to warn the poster such RIAA EQ modification may 'trash' the amp & he also suggested to consult the amp's designer first.
To this, I totally agree.This Herron phono pre-amp sounds superb when matching with other equally fine quality components. So why need to modify it?
My question is: is there anywhere along the audio chain that needs to be improved in the first place than modifying the phonostage?Nowhere in the post hinted replacing any coupling caps. Only :"to avoid" was clearly stated. It is Bob & your assumption only which may not even the case.
A question to you, if the coupling caps in the "passive RIAA section" were polypropylene PP, which are pretty commonly used in RIAA network coupling, what "other high quality" caps would you suggest?
Tweaking is the name of this forum. But it got to work out with logics & common sense. RIAA EQ is the last place of a phonostage I want to modify despite I built/upgrade a few.
Which would be a tougher experience? Screw up the fine phonostage or a word of caution to think twice?
c-J
Follow Ups:
How you make the assumptions you do I am not sure. To help you, let me repeat verbatim"I want to avoid any couplers in the passive RIAA section."
a·void /əˈvɔɪd/ Pronunciation Key –verb (used with object)
1. to keep away from; keep clear of; shun: to avoid a person; to avoid taxes; to avoid danger.
2. to prevent from happening: to avoid falling.
3. Law. to make void or of no effect; invalidate.
4. Obsolete. to empty; eject or expel.
Hi.To "avoid" in this situation means to me "to empty, to eject or expel". So from what you wrote would mean to me you don't want any coupling caps in the "passive RIAA section".
That would be a serious issue as coupling caps there got to have their function, e.g DC blocking, etc., that I can tell you once you find & post the schematic.
But you actually mean to 'replace' them with other type of caps instead of "to avoid" them. So the way you wrote misled me.
c-J
I clearly state in my heading I want to upgrade my coupling caps, and then state further I want to avoid the couplers in the RIAA stage.One has to be quite dim to interpret my statement as me wanting to remove the RIAA caps ...
Hi.We can void a contract, but we don't void a capacitor but we can "avoid" using one.
In fact my English is so bad that it actually seemed to me that you think I am your friend and you think I need to provide you with a justification for me wanting to modify one of my own amps!Wow, what a misunderstanding.
To expand on Jack's comments, from what I remember Keith held some pretty tight tolerances in the RIAA section. I believe he even recommends contacting him before key tubes are swapped because the circuit is built around a specific mu and gain. Now if the circuit is that precise, why muck around with success? Just so you can drop in a couple of special caps you've been itching to try??Besides, the layout of the circuit is very clean - this isn't a point to point wiring job where there may be space for physically larger parts. What deficencies are you trying to address?
I'm not saying that the piece is above reproach (it's pretty close) but just think about the whys and wherefores of what you are doing.
Hi BobI appreciate your concern. I have upgraded a number of amps before ... although I always had the circuit diagram available. I don't now and that's what I'm asking for.
I am not thinking of changing the RIAA caps. I honestly did I wasn't, so I am not sure how that came about.
From what I could see the couplers are 0.22uF caps and there is plenty room for a V-Cap/Dynamicap sized coupler. I would like a circuit diagram though to be 100% sure it is the coupler cap I am looking at.
The Herron is a good piece. I want a little better. I can spend $600 on high quality caps or $10,000 on an Aesthetix. I don't really have $10,000 to play with now ...
If I put in the new coupling caps and they sound bad/worse, I can always revert to OEM. As I told Jeffrey, I do one stereo pair at a time and audition. No biggie.
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