Which basic mods do what?

megabigeye · 4555

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Offline megabigeye

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on: September 13, 2018, 04:21:56 AM
Hi there,
I've been happily using my Quickie and Quicksand as a headphone only amp since rolling new tubes into the Quickie and doing a minor mod to the Quicksand.  Of course, this got me wondering how else things could be improved.

I'm wondering what basic mods there are for the Quickie and what they achieve?
Specifically, I've seen people mention switching out the pot for either a new pot or an attenuator, but never any mention of what exactly is improved.  I've seen this pot and this attenuator recommended.  Is there a difference between them other than price?  What benefit does each offer over stock or each other?

I've also seen plenty of mention of swapping (output?) caps.  From the descriptions, it sounds like this is the miracle cure that fixes pretty much everything, but I can't quite imagine that's completely true.  What specifically do new caps do?  How do I determine which caps I want?  How do different values (or materials, I guess?) change things?

Are there other basic mods that people do?  What unique improvements do they achieve?  And how do you go about determining how to do them?
As is usual for me, if you could explain it in as basic language as possible it would be greatly appreciated!

Thanks!

PS-- I should also mention that my one gripe is a perceived veil when listening at lower volumes.  It's a loss of detail, dynamics, and soundstage.  Of course, I have no idea if it's me, my headphones (DT 1990), or either the Quickie or the Quicksand.  First intuition tells me that it's the Quickie pot, but of course, I have no way of confirming that.  I notice it on another amp, too, but it's actually worse on that one (or maybe I'm just not volume matching).
« Last Edit: September 13, 2018, 04:31:03 AM by megabigeye »

Ken


Offline Paul Birkeland

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Reply #1 on: September 13, 2018, 05:00:47 AM
I'm wondering what basic mods there are for the Quickie and what they achieve?
To some degree or another, the experience you gain by trying these mods on your own will outweigh what you read online. 
I've also seen plenty of mention of swapping (output?) caps.  From the descriptions, it sounds like this is the miracle cure that fixes pretty much everything, but I can't quite imagine that's completely true.  What specifically do new caps do?  How do I determine which caps I want?  How do different values (or materials, I guess?) change things?
These are a lot of questions that could each take on a lengthy answer.  For the Quickie, try to get at least 2uF for the coupling caps.  Voltage and tolerance aren't particularly important.  Again, just try a different brand of cap  and see what it does for you.

Are there other basic mods that people do?  What unique improvements do they achieve? 
The PJCCS is the obvious mod for the kit.  The improved loading for the 3S4 offered by the PJCCS will increase gain slightly and reduce distortion.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline cpaul

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Reply #2 on: September 13, 2018, 06:55:47 AM
I agree with PB.  The best mod by far will be the PJCCS (perhaps a choke instead of the PJCCS but I haven't tried that and it's more expensive).  Bang for the buck it's the best mod and it will be sonically the most noticeable.  And I'm pretty sure it will address the veil you mention (it did for me).  As for the output caps and volume pot/attenuator (they are the same thing) you may or may not hear a difference.  A lot depends on how good your ears are and how well you know how to listen for the differences.  Some claim night and day changes from different coupling or output caps.  I only notice quite small changes and nothing worth the hundreds some people spend on replacement caps.  Don't spend more than $30 or so per cap unless or until you've figured out that you CAN hear a big difference.  Even that is a HUGE amount to spend on caps IMHO.

I've replaced the attenuator and output caps and I did notice a difference with the attenuator but it was small.  The cap change accompanied other bigger changes so I can't say much about that.

All that said, I don't listen with headphones (well...not much) so it may be that what I've written doesn't apply in your case.  But I suspect it does.



Offline cpaul

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Reply #3 on: September 13, 2018, 07:09:05 AM
One more thing.  I suspect, though I haven't tried it with Quickie, an autoformer input attenuator might be a big improvement.  Of all the options autoformers are probably the best approach.  But they are costly! 

The basic volume control provided with Quickie is a simple carbon pot (at least that's what I got) and they tend to be a weak link.  In any case replacing it will likely give you SOME benefit.  But if you replace with a stepped attenuator, be sure to go with a ladder type stepped attenuator, not a series or shunt type.  Series will give you a long line of resistors at lower volumes, which will undermine the benefit where you need it most.  Shunt will present a variable impedance to your source, which may be a problem. 

The one you linked to (which may have been one I posted about) may be a series attenuator - they don't say and I haven't taken it apart.  While it will perform much better than a carbon pot, it won't be as good as a ladder stepped attenuator.  Again, though, you may or may not hear much of a difference.



Offline Bonzo

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Reply #4 on: September 13, 2018, 09:24:33 AM
There is also an old thread written by Earwaxxer (dunno if he’s still a member here) where he reports his sonic impressions for each Quickie mods, maybe it could help.

Ciao

Bisogna avere orecchio!


Offline megabigeye

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Reply #5 on: September 19, 2018, 09:54:07 AM
To some degree or another, the experience you gain by trying these mods on your own will outweigh what you read online.  These are a lot of questions that could each take on a lengthy answer.  For the Quickie, try to get at least 2uF for the coupling caps.  Voltage and tolerance aren't particularly important.  Again, just try a different brand of cap  and see what it does for you.
The PJCCS is the obvious mod for the kit.  The improved loading for the 3S4 offered by the PJCCS will increase gain slightly and reduce distortion.
Oops!  Almost forgot I'd posted this.
Yes, of course experience will teach me more than reading online, but I was hoping for a basic idea of what to expect for each mod.  I mean, I assume that there's some science and technical reason behind what happens when once cap or volume pot is changed for another and therefor there should be some predictability.  Right?
Of course, I'd forgotten I've already done the PJCCS.  Duh.  That's the sort of answer I was looking for.  "will increase gain slightly and reduce distortion."

@cpaul: Thanks.  I guess somewhere in my brain I knew there were different types of attenuators, but it hadn't really donned on me that I should be looking for one rather than another.  I'm thinking I'll get this 100k stepped ladder type from valab.  I read somewhere on the forums that it works well.  I just have to buy my wife a birthday present before I can get myself a present.  I wonder what she'd think of a couple of capacitors??
Also, I'll try to set my expectations realistically.  I know there's a lot of variance between what two people can hear, and also what they claim to hear.

@Bonzo, thanks.  I'll look into that thread.  I haven't stumbled across it yet.  Seems like some of the really old threads were lost at some point (broken links), I hope that one wasn't a casualty to time.

Ken


Offline cpaul

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Reply #6 on: September 19, 2018, 03:04:53 PM
Ken,
I can't tell from that link if the pot you linked to is a true ladder type or not.  I does look like a ladder type but the description is a bit confusing.  Anyway, the price is right.  Only other thing is a 23-step attenuator is the bare minimum to me.  Even 23 steps results in some big changes in volume at each position so it's hard to find the sweet spot for volume.  In the end there may not be that much difference in ladder vs series or even shunt if the source can handle it.  All will be a step up from the stock pot.

Carl




Offline cpaul

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Reply #7 on: September 19, 2018, 03:12:18 PM
BTW, that veil at low volumes may just be a consequence of low volume listening.  Every system I have heard loses a lot of sound quality at lower volumes (lower seeming resolution, reduction in bass and in treble detail, etc.).  For some reason it seems like my cathode follower version of Quickie may not suffer this effect as much as other gear, but that may just be the honeymoon phase of post construction bliss...



Offline megabigeye

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Reply #8 on: September 19, 2018, 05:11:10 PM
Thanks for the response!
It seems from the description that it's a ladder?  Anyway, the seller is pretty reputable, I believe, and it's only ~$30 with shipping, so no huge loss either way.
I was wondering about whether or not 23 steps would be enough, especially since I'm using it for headphones.  Do you have any recommendations for a relatively inexpensive ladder attenuator?  I could also try that Audio Note pot or look a little deeper for something else.
And about the veil...  well, I'll say that I noticed it the first few times I listened to the Q+Q setup after I'd modded it and it was pretty distracting.  I don't notice it so much anymore, at least partially because I listen louder than I should.  In fact, right before I made that first post I tested it against my "main" Peachtree amp and couldn't really discern much of a difference.  I wasn't being the least bit scientific about it and I also wouldn't be surprised if the Peachtree suffers from the same "problem."  I do recall having seen some thread here where it was discussed that systems don't really gel until they've reached a certain volume (at least I think it was here).  But to be clear, when I experienced the veil it wasn't low volume, it was not-too-loud volume, and it only disappeared when it was louder than I'd have liked.  And I don't recall ever having heard something quite similar with other systems.
Anyway, I'll listen to it more and see if it bothers me again.  I might end up doing mods anyway, because why not.

Thanks again!

Ken


Offline Paul Joppa

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Reply #9 on: September 20, 2018, 07:42:42 PM
... I mean, I assume that there's some science and technical reason behind what happens when once cap or volume pot is changed for another and therefor there should be some predictability.  Right?...

Haha! No, that's not an accurate assumption, IMHO. Most things like that are based originally on things people hear subjectively; the science and technology are still in the speculative phase - plausible but unproven. Only a few things (such as current-source plate loads) are directly measurable, and even then the connection between measured distortion and perceived sound quality is poorly understood. That's why it's important to listen to thins yourself and make your own judgements - and keep an open mind!

Paul Joppa


Offline brucef

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Reply #10 on: October 15, 2018, 12:06:14 PM
I finally got around to installing an Audio Note 100k pot in my Q ( It had been on the shelf for 10 months) and I have to say that there is a notable difference. The soundstage, depth and clarity is really nice. And I don't seem to get as much in the way microphonics. Overall happy with the upgrade.

Bruce F


Offline megabigeye

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Reply #11 on: November 14, 2018, 04:45:14 AM
I finally got around to installing an Audio Note 100k pot in my Q ( It had been on the shelf for 10 months) and I have to say that there is a notable difference. The soundstage, depth and clarity is really nice. And I don't seem to get as much in the way microphonics. Overall happy with the upgrade.
Great to hear!  I just got the same pot in the mail yesterday!
Does it wire up the same was as the stock pot?

Thanks,
Ken

Ken


Offline brucef

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Reply #12 on: November 16, 2018, 12:13:47 PM
Great to hear!  I just got the same pot in the mail yesterday!
Does it wire up the same was as the stock pot?


Yes it does. Very happy with the Audio Note

Bruce F


Offline megabigeye

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Reply #13 on: November 16, 2018, 02:16:58 PM
Awesome!  Thanks, Bruce!

Ken


Offline aragorn723

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Reply #14 on: November 22, 2018, 02:11:57 AM
Great to hear!  I just got the same pot in the mail yesterday!
Does it wire up the same was as the stock pot?


Yes it does. Very happy with the Audio Note

Which Audio Note pot did you get, can you send a link?  I saw the link above is to a balance pot, isn't that for left and right fade?

Dave