Crack + Speedball Working, Sound Affected by Solders/Voltage Margins?

[Pepper]

Dear Bottlehead community,

So I just finished my Bottlehead Crack and Speedball. To be honest, it looks nothing as neat as the pictures. In fact, I don't even know how everything looks so neat in the pictures, because I just found that there were always so many wires everywhere. I had to push wires out of the way (maybe it was because I cut the wires too long because I was paranoid they would be too short).

In any case, my soldering iron (old one) was really bad, and I did half of the soldering with that, and then switched to a good one. Needless to say, the amplifier + speedball work, and I can listen to music through it, and it certainly sounds good. However, I am not blown away by it (I'll be testing with a DAC tomorrow, and new RCA cables, because mine suck).

However, I have to ask: Can my sound quality be lowered a noticeable amount if my solders aren't perfect, or if my voltage readings are, let's say, always about 10-15% off? Or, if it works, then it should be working as best it can, and if it doesn't work, then it doesn't work?

I keep hearing that it should have a warm sound signature, but it doesn't sound particularly warm; it sounds neutral to my ears (but maybe that's because I'm used to Earsonics SM3s).

Please let me know your impressions,
Pepper

P.S: I'm using a pair of Sennheiser HD650s, and I've never heard them amped by anything else before, and so maybe I'm just hearing the airier "Sennheiser sound."

[adamct]

Basically, if its working and your voltage checks are within 10-15%, then you should be OK. If your solder joints are bad, that doesn't mean it will STAY working, but I wouldn't expect it to affect the sound as long as it is working and within tolerance. (BTW, as I understand it the 10-15% tolerance range isn't there because solder joints can affect the results (other than getting no results), but rather because your input voltage and tube strength can affect the voltages a bit. So being 10-15% off target voltages doesn't mean there is anything wrong with your Crack at all.

As for the sound, I don't find the Crack warm or tubey. I find it sounds crisp, clean, detailed and neutral, which is how I like it. I had a WA22 and a WA6 when I built my Crack. The Woo amps definitely sounded tubey, but then they were WOT, not OTL. As soon as I heard my Crack, the Woo amps were up for sale and I've never regretted it in the least.

Give the Crack a chance. Spend some time with it. I find the sound addictive...

[Pepper]

Thanks a lot for the response. I guess I was expecting a different sound signature.

I have another important question

How much should the volume knob be up? Maybe there is something wrong with the way I built my crack. I was expecting it to have a lot of power behind it, and really power my HD650s with only a little bit of volume. But I can comfortably turn it to like 50%, 65% way around the dial. I've gone as much as 75% but I'm scared to keep it there, or I start noticing more bass (I can feel it vibrating), but only at the expense of SQ (sound starts getting a little distorted).

I also noticed that the SQ goes up kind of like different gears of a car. I can move it about 10%-15% of the way around without any difference, and then suddenly I'll hear a big pickup in difference. And then another 10%-15% the way around, and I'll suddenly hear a big difference. It's not a smooth transition up. Is this normal?

Thanks,
Pepper

[STURMJ]

Sounds like you are using the stock volume pot.  Cheaper pots don't track very well in the low (volume) end. Once you convince yourself that the crack is working well, spend another $20 on a good pot. Also, it sounds like your headphones are new.  Give them a little break-in time. Break-in burn-in can be a controversial topic ( not around here) when it comes to caps, cables etc. But phones are mechanical devices, with moving parts (so to speak). Let them play for a day or so on another amp and you will probably notice a difference too.

[adamct]

What are you using as a source? Do you know what the output level of your source is? With my DAC, using HD600s (very similar to your HD650s), turning the volume up that high would be deafening. But a lot depends on the strength of your input signal. As long as the Crack has enough power to get you to a volume level you are satisfied with, I wouldn't worry about whether it is 25%, 40%, 50% or 65%, but you shouldn't be getting distortion or clipping.

The action of your volume pot doesn't sound entirely normal to me. While STURMJ is right that volume pots can have trouble tracking at low volumes, it sounds like you are well out of what I would consider low volume on your volume pot. I would try twisting your pot from minimum to maximum 25-30 times first to see if that helps solve the problem. Sometimes there is a bit of oxidation or grunge that can form within the pot, and exercising it a bit can help clean the contacts.

[Paul Birkeland]

]
How much should the volume knob be up? Maybe there is something wrong with the way I built my crack. I was expecting it to have a lot of power behind it, and really power my HD650s with only a little bit of volume. But I can comfortably turn it to like 50%, 65% way around the dial. I've gone as much as 75% but I'm scared to keep it there, or I start noticing more bass (I can feel it vibrating), but only at the expense of SQ (sound starts getting a little distorted).

This is incredibly dependent on your source level.  Most users report the opposite problem, which requires a few additional resistors be added to the circuit.  With a low-output source, you could have the volume control all the way up and never come even close to reaching maximum power.

-PB

[2wo]

As long as you are not running out room to go, just a bit louder. You are good to go.

I think, all equal, volume pots sound better close to 100% than they do at 10% ...John

[Paul Joppa]

Breakin is always surprising. Almost everything I've built has sounded disappointing to me at first. Give it all something like 50 hours of music before making judgements - you don't have to listen to it during that time if you don't want!

Is not the Earsonics SM3 an in-ear module? That will be a different experience from the Sennheisers or other over-the-ear phones. I'm not a headphone guy, but it may be interesting to try the Earsonics in spite of their low impedance. Perhaps someone more knowledgeable will know whether the impedance function is flat with frequency?

[Pepper]

Thanks a lot for the replies, guys. Here are some clarifications:

1. I am using a Schiit Modi as the DAC.
2. I agree that the headphones need some breaking in .

With that in mind, I will describe my experience with the Crack/speed + HD650s, and maybe you guys can identify if there's something fishy:

a) I am finding my listening experience very pronounced in the treble. The lows seem to be lacking, and there is a lot of treble. It is very revealing, but the sound isn't very solid. Bass and lows are weak, so it makes everything sound really bright.

b) The highs are not sibilant, but they sound a little tinny (they are on the very cusp of being sibilant)

c) The small tube isn't glowing very orange (compared to the big one). Is this a connection problem? It also doesn't seem to get nearly as hot. I mean, it's still hot and you wouldn't be able to comfortably leave your finger on it for 20 seconds or anything, but the big tube is searing hot after an hour or more of use.

d) I wasn't very confident in my solders for the small tube's socket and I feel like this is creating suboptimal connections for my small tube.  Does this make sense at all with my experiences of the sound? (i.e. lacking in the lows, and very treble oriented sound)? I'm not very educated when it comes to this stuff, so I am not sure how either tube affects the sound.

e) Sounds more analytical and bright rather than smooth and warm. I was expecting smooth and warm with some mids bump with the HD650s and the Crack + Speedball, but I'm just not getting it. I'm really starting to be convinced it's that the headphones aren't burnt in (they are quite new), but mostly that my soldering was bad for the octal sockets, and this is somehow affecting the sound.

If you can see anything that gets your attention from what I've stated, please mention so. Also, if you are running the HD650 + Crack/Speed setup, please let me know what your sound is like. I really feel that my sound is too neutral/analytical/bright in treble to be normal (i.e. lacking in lower mids and lows).

Thanks,
Pepper!

P.S., I will check the volume knob to see what's up. This whole thing is confusing because I'm not sure if it's actually a problem with the circuitry itself (because of crappy soldering)! I'm planning to go over my solders and snip excess wires better with proper snippers.

[Grainger49]

First, I'll address your questions in the first post only:

If the voltages are not within +/- 15% it could be the tube needs to break in.  If after 100 hours, run 4 days with or without music, the tubes still don't give +/- 15% then there is a problem.  It could be your incoming voltage.  If it is high your voltages run high, if it is low just the opposite.  If you are within the 15% the amp will run well.

Cables with less than solid connections will give you noise, and of course, sources affect the sound.

You ask if the solder joints can affect the sound, the answer is of course!  A first time builder almost never makes a crimped joint with the wires and component leads before soldering.  I didn't either.  So you are using the solder as glue to attach the components within the circuit.  Bad solder joints are resistive and often intermittent connections.  So even if the Crack works, it may not be working right. 

Now as to the position of the volume control.  All of the turn is there for a reason.  Use it.  The more power your headset needs the higher you will crank it to get a satisfying volume.  As long as it gets as loud as you want and the volume is not all the way up, you are fine. 

Other headsets that need less power will probably play well in the first 1/3 of a turn. 

I don't follow your reference to "SQ" I don't know the abbreviation.  But it sounds like you are referring to the volume control again.  The volume pot is an audio taper, the curve is logarithm.  But that is the way our ears hear.  I have been using stock Bottlehead volume pots on my preamp for more than 10 years.  I run them near the high end most of the time but have never had a problem with the sound jumping.

If this is not the reference to SQ, ignore the above comment.

My recommendation would be to allow 100 hours of break in.  Then if the problems persist you should start touching up your solder joints.

Good luck.

[Doc B.]

Solders joints are not likely to affect bass like you are describing if the amp is measuring properly. I agree that you need to let the headphones break in for a while. I am not familiar with the sound of the Modi, but a source component can influence the tonal balance too. Cables can also have a very big influence on tonal balance. What is your point of reference for the tonal balance you hear. Is it another headphone rig, a speaker setup, or?

[Mike B]

I bought a new set of Senn 600's for the Crack and they have been here 4 weeks now.

They were sort of like you mentioned right out of the box, light on bass and the treble was a little stiff.

A guy who had then reccomended 100 hrs of break in and I have been running them 12 hours / day for 4 weekends now.

They did loosen up.  Treble is smoother and bass is better. 

[Pepper]

I don't follow your reference to "SQ" I don't know the abbreviation.  But it sounds like you are referring to the volume control again.  The volume pot is an audio taper, the curve is logarithm.  But that is the way our ears hear.  I have been using stock Bottlehead volume pots on my preamp for more than 10 years.  I run them near the high end most of the time but have never had a problem with the sound jumping.

Thanks a lot for the recommendations. SQ is just short for "sound quality." I should have specified that. I think I exaggerated the volume jumping effect, and I think it is okay now (at least there's nothing seriously wrong with it). Since you mentioned the logarithmic scale, I think that can put my concerns to rest: I was expecting a very linear increase in volume because I'm used to that from crappy volume controls (ones that are all digital and just on your laptop, for example).

I agree that you need to let the headphones break in for a while. I am not familiar with the sound of the Modi, but a source component can influence the tonal balance too. Cables can also have a very big influence on tonal balance. What is your point of reference for the tonal balance you hear. Is it another headphone rig, a speaker setup, or?

I think they need break-in too. I think a lot of the sound I'm getting is symptomatic of a new pair of headphones (I just wasn't sure). A lot of people seem to be pointing to this as well, so it looks like a big source of the problem.

My reference point, also, are just my experience with a bunch of very mid forward "warm" IEMs (like the Earsonics SM3), and a warmer studio monitor set I have (JBL LSR2325p). To me, the HD650s are sounding like the Westone UM3Xs (more analytical and not very fun) but with floppier bass (instead of punchy like on the UM3Xs) and a little more tinniness in the treble.

A guy who had then reccomended 100 hrs of break in and I have been running them 12 hours / day for 4 weekends now.

They did loosen up.  Treble is smoother and bass is better.

That is very comforting to know.

What I will do until further notice.

I will be letting the headphones and amplifier burn in. I am just scared of how long I can leave tubes running for, so I tend to turn everything off after 4 hours of continuous running. What is an acceptable duration to keep the amp on (for burn-in purposes)? And is it recommended that I try to burn in the HD650s to another amplifier, or just keep it with the Crack?

I will be going over and re-soldering some things (or just making sure that things are soldered tightly, and try to clean up some wires.

Thanks so much for the help, everyone. It has been immensely helpful and reassuring.

[Mike B]

The phones will break-in fine with any source, just need the drivers excercised.

Might as well break-in the amp too though, tubes and caps need to cook too.

[Doc B.]

I would probably not leave the amp on for more than 5000 hours at a stretch. Any longer could start to wear the tubes out.