hpa input impedance

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ed
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#1 hpa input impedance

Post by ed »

I was recently having doubts about my ultra simple hpa and started looking at more complicated circuits.

I noticed quite a few circuits where there was an input pair of phonos and an output pair. In these circuits many of the input and output pairs were connected. In these instances does the input resistor of the hpa affect the operation of the power amp connected to the output pair of phonos to any great extent.

I mention this because I went the extra mile with my hpa to install an input relay to switch the input pair of phonos between the hpa and any power amp to isolate any effect. In practice was I wasting my time as there is rarely going to be a precise balance between source and load unless the knowledgable specifically make it happen.

when I said 'doubts about my hpa' I was experiencing distortion on certain tracks(unfamiliar radio tracks) and in my paranoia I couldn't work out whether it was my equipment or studio introduced.

I'm thinking of trying Wayne Colburns 'whammy'. Anybody got any experience of it?
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#2 Re: hpa input impedance

Post by Ray P »

ed wrote: Mon Mar 29, 2021 10:09 am I'm thinking of trying Wayne Colburns 'whammy'. Anybody got any experience of it?
Ed, no experience of the Whammy but I built and use the 'Noir' , also available from the DIY Audio store - it really is very good.

https://www.audio-talk.co.uk/phpBB3/vie ... 20#p170120

Maybe these JLH HPA modules might be of interest and they're in the UK at a good price. The Xen derivative of the JLH HPA is well regarded. Pretty sure there's a thread somewhere on DIY Audio. Not sure what else you would need to complete a functioning HPA, obviously a power supply, but I've dealt with the guy before and he's straight up and helpful.

https://www.diyaudio.com/forums/swap-me ... o-kit.html
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#3 Re: hpa input impedance

Post by ed »

Thanks Ray

I had been comparing the two..decisions decisions...I had favoured the whammy for no other reason than it seemed more elegant..but you've caused me to re-think.

I'm still not sure if there's anything wrong with my simple attempt. Because the times I've been concerned have all been with stuff on the radio that I've no way of comparing with other set-ups.

I have noticed there is more and more modern stuff that has distortion applied to instruments other than guitar...even voices....I'm really concerned with that grundgy, grainy type of distortion. I can readily identify the source when it's applied to guitar, but not so easily when on vocals.

I think I need to borrow a higher end hpa before I condemn mine, or commit to spending money.
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#4 Re: hpa input impedance

Post by Ray P »

It's a shame you live 'up North' Ed, otherwise I would have happily given you a listen to the Noir.
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#5 Re: hpa input impedance

Post by Ray P »

Here's another option Ed, occasionally tempted to try one myself.

http://www.pmillett.com/nuhybrid.html

https://www.ebay.co.uk/itm/DIY-PCB-plus ... SwTM5YxaUY

You didn't comment on the JLH HPA I linked to, in case it's of interest here's a link to the thread.

https://www.diyaudio.com/forums/headpho ... ifier.html
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#6 Re: hpa input impedance

Post by ed »

thanks again Ray

I can't dig up any enthusiasm for the JLH variants.
As I said, I'm going to hang out until I can borrow a well-established amp for comparison. I think the most important word in my first post was paranoia as I've tried it on everything I've got in my library and all my stuff from the studio....and I can't catch it out. It's just the odd, unknown on the radio that causes this niggle.

I don't really want to spend time and money on something that might end up being the same as I've already got, give or take.

On the other hand, I won't know if it's generally deficient in other areas until I've heard an accepted alternative....for once I'm going to try patience.

Edit....
I've just heard a perfect example of the distortion I'm referring to:

Calexico - sinner in the sea

is anybody familiar with this...and if so, is it really distorted/grundgy/grainy?
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#7 Re: hpa input impedance

Post by Max N »

Hi Ed
Not sure if this is relevant, but when you say radio do you mean a tuner or internet? I do most of my headphone listening on bbc sounds these days, and I think occasionally it drops to a lower bit rate.
For sure some music these days has huge amounts of compression/distortion. I find the replay chain itself has to be very low distortion to untangle these tracks and make them listenable. Are you able to make any objective measurements of your hpa / amp distortion? I’ll have a listen to the track you mentioned.
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#8 Re: hpa input impedance

Post by ed »

thanks Max

the distortion in question is always with tracks on internet streamed radio, and only rarely. It's not anything to do with compression...it's grain and grunge.

the full description of the hpa is here:

https://www.audio-talk.co.uk/phpBB2/vie ... =13&t=8003

I have only noticed it with Paradise at 320kps(I rarely listen to other internet streams at the mo) and I've never noticed on the main amp/speakers, at least not consciously.
Last edited by ed on Fri Apr 02, 2021 10:01 am, edited 1 time in total.
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#9 Re: hpa input impedance

Post by Nick »

The guitar has light amp clipping thats about it after a quick listen

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#10 Re: hpa input impedance

Post by ed »

thanks Nick...

that's nailed it...We will have to disagree with what constitutes light clipping.

I've just listened on Sandrine's laptop and I get the same effect I described. initially to me it sounds like fuzz on the rhythm guitar behind, which bleeds into the toms and blurs their edges. as an aside I remember getting exactly that sound on stage when our front mans electro/acoustic batteries went flat. Either way it sounds like an artifact the engineer deliberately wanted.

I will download that link and get more anal with it on the other systems....

So far that has very much brought in a not guilty verdict on the hpa.
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#11 Re: hpa input impedance

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ed wrote: Thu Apr 01, 2021 9:09 am
Edit....
I've just heard a perfect example of the distortion I'm referring to:

Calexico - sinner in the sea

is anybody familiar with this...and if so, is it really distorted/grungy/grainy?
I'm not a Spotify user, but on digging I find I have passwords for the free version. I'm listening on my laptop with half tidy headphones that make most YouTube videos sound OK.

As a control I've just listened to a few Spotify Dire Straights recordings.

Verdict

A) Spotify free on my laptop with my headphones is not brilliant.

B) That Calexico recording is as you describe.
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#12 Re: hpa input impedance

Post by Nick »

We will have to disagree with what constitutes light clipping.
Well, its such that its clearly an intentional choice. Sounds like the same sort of thing as a fuzz face on the edge of clipping as in little wing.
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#13 Re: hpa input impedance

Post by ed »

No response to the original question about impedance?

I’ve down loaded the track and compared a standard download and a normalised download and the outcome is much the same. There is a lot of distortion processing on more than one track, but not all of them. The overall impression I get is one of grundge.

At first I wasn’t won over but after a few listens I’ve come to like it, a lot.

It would seem I’m not as confident in musical terms as I used to be, but then, I used to have a different set of ears.

The bottom line is psychological. The fact that I listened to a fleeting piece of music on the radio(which I couldn’t immediately reproduce) and immediately questioned a piece of equipment, speaks volumes to me. I’ve been listening to the hpa for 4 or 5 months now, so I should know it’s capabilities....why would I suddenly question it’s abilities....I have demons.
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#14 Re: hpa input impedance

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ed wrote: Fri Apr 02, 2021 11:21 am No response to the original question about impedance?

I’ve down loaded the track and compared a standard download and a normalised download and the outcome is much the same. There is a lot of distortion processing on more than one track, but not all of them. The overall impression I get is one of grundge.

At first I wasn’t won over but after a few listens I’ve come to like it, a lot.

It would seem I’m not as confident in musical terms as I used to be, but then, I used to have a different set of ears.

The bottom line is psychological. The fact that I listened to a fleeting piece of music on the radio(which I couldn’t immediately reproduce) and immediately questioned a piece of equipment, speaks volumes to me. I’ve been listening to the hpa for 4 or 5 months now, so I should know it’s capabilities....why would I suddenly question it’s abilities....I have demons.
In case it's of interest Ed

https://www.diyaudio.com/forums/swap-me ... o-kit.html
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#15 Re: hpa input impedance

Post by Michael L »

I'm very happy with my Whammy Ed. It works very well with my Sennheiser 580.
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