Crack around the world !

[Guy 13]

Hi all.
I was wondering what would happen
if I try for just a few minutes to run my Sennheiser HD-570 (60 Ohms) headphones on my Crack.
I want to compare the sound of my HD-650 vs HD-570.
This is just a test; therefore I don’t want to make any resistor(s) set up.
Just plug and play.
Thanks.

Guy 13
 

[galyons]

You won't hurt anything.  At 60 ohms they are a poor match for the Crack.  Most likely you will notice a poor bass response.  I listened to my AKG K702's, (62 ohms).  Not terrible, just not at their best. 

It is not a Crack "thing".  It is the same for most any high impedance amp.  I also have an Elekit TU882As, with WE396A's, (5670, 2C51). It is transformer based with switchable  impedance.  It is a pretty dramatic testimony to the mismatch switching from low to medium to high impedance while listening to the 702's. 

Cheers,
Geary

[Guy 13]

Hi all.
I did some more listening and burn-in of my Bottlehead Crack and Sennheiser HD-650 combo.
I think I already mentioned that my listening room could also be called an oven with 33C/92F in it and that the Crack runs pretty hot, even in a cooler ambiance.
Therefore, I did the following set up.
I have two fans in parallel blowing cold air 33C/92F under the hood or more correctly called the chassis.
It does make a big difference on the top plate, it’s hardly hot and what I like about the Crack compared to my Decware SE84C+ is that the transformer runs almost cold.
I had it running for about two hours with my iPod (Far from a hi-end source, but that’s what I had near by and easy to set up.)
I still find the sound to be… I am using the word dark, because I don’t know any other word to describe the sound from my combo.
After two hours of listening, maybe it was a little less dark, maybe my imagination, maybe I am getting use to the dark sound or maybe it’s getting more broken-in ? ? ?
Sorry about my limited English audio vocabulary.
Even if I use the French language, which is my native language, I am still at loss when it comes to find the right words to describe the characteristics of the sound.
Maybe other members can help me with my limited vocabulary, if they have experience with the same combo as mine.
Don’t get me wrong, the sound is good, but it looks as if the top layer of harmonics has been shaved off.
It’s missing the ambiance of my Omega 7F extended range driver
And I am not talking about the sound stage; it’s the ambiance, the reverberation, the micro details, the harmonics…
Let’s see who agrees or disagree with me.

Guy 13
 

[Grainger49]

Guy,

I now know how that is pronounced.

I think you have a good handle on dark, balanced and bright. 

When I suggested the fan I forgot to say to use a hole saw and open a round hole in the back of the base, attach the fan with a series of small O rings so it doesn't make noise.  This moves more air into the under chassis blowing across the bottom of the transformer and the power supply and cathode resistors.  Those are the primary heat generators there.  Keeping all the components cool lengthens their life.

All the capacitors are breaking in.  The cathode is forming on the 12AU7.  So give them 50-100 hours of run in and see if the sound brightens up.  Or you might be like me and have lost some high frequency response in your ears over the years. 

If you are not picking up any noise from the iPod, good.  If you hear some odd sounds try moving it a meter away.

Good luck!

[Guy 13]

Guy,

I now know how that is pronounced.

I think you have a good handle on dark, balanced and bright. 

When I suggested the fan I forgot to say to use a hole saw and open a round hole in the back of the base, attach the fan with a series of small O rings so it doesn't make noise.  This moves more air into the under chassis blowing across the bottom of the transformer and the power supply and cathode resistors.  Those are the primary heat generators there.  Keeping all the components cool lengthens their life.

All the capacitors are breaking in.  The cathode is forming on the 12AU7.  So give them 50-100 hours of run in and see if the sound brightens up.  Or you might be like me and have lost some high frequency response in your ears over the years. 

If you are not picking up any noise from the iPod, good.  If you hear some odd sounds try moving it a meter away.

Good luck!

Hi Grainger49.
Good to know that you know how to pronounce my name,
because I hate when people pronounce my name the English way
like in:
I saw that guy or how are you guys doing?
Glad to see that some people agree with my use of the word " Dark"
for the HD-650.
About the fan, the picture shows a temporary set up.
I just wanted to see how much cooling it would do to the Crack.
I've used my work bench because all the electrical outlets
are within an arm reach and there is plenty of room
around so I don't kick things and don't hurt my toes knocking it on something.
Later on, I will find a small DC fan as you recommended
and get it installed (Wood work) by the cabinet maker
that I know and trust.
I don't want to spoil the nice looking base by doing it myself
with my hands full thumbs. (If you see what I mean?)
I do some daily listening to get to that magical 100 hours.
I am sure that my 66 years old ears have a 14KHz ceiling.
No noise from the iPod.
However, I did hear a very faint 60 Hz hum,
it' always very low and inaudible when music is playing
and it stays at the same level regardless of the setting of the main volume control.
I think it's a problem with the house's earth ground.
I can also feel a very small tickle at the tip of my fingers when I touch the top plate of the Crack.
When the Crack will rest at his final destination,
I will have a good ground connection.
I don't really worry about it right now.
Next week I will go with my Crack at the store from whom I bought the HD-650 and try a pair of HD-800 and other hi-impedance headphones.
Just for fun,
because I cannot afford anything now or in the next 10 years to come,
unless of course, I win the lottery's jack pot.
The salesman of the headphone shop agree to ear what my Crack
can do with his Sennheiser headphones.
That should be fun.
I will let you know (Hopefully with some pictures) how that  party went on.

Guy 13