review for Sheer Audio HA-006+ (DynaLo) ? - Page 7

Factory informed me that there's a delay on the transformers, and will have the transformer done this week. The pre-order special will remain in effect until we are ready to ship it out.


Thanks

David

Ahhhh!!! It's okay, good news if it really is this week though, wee. Thanks for keeping us updated Maniac.

I have a pair of K701's and am getting a pair of JH13 Pro's... what gain should I choose? Would 1x gain be way too weak for my AKG?

Hey Maniac I am definitely getting a hiss on my HA-006+ with JH-13. Even with volume knob at 0, turned all the way off, I still get very noticeable hiss in the right ear. If I turn the knob above 9 o'clock I can hear some hiss in the left side as well. I'm kind of bummed, since I have to turn the amp up a good amount to mask the hiss, and even then I feel like it is affecting SQ

Hello,

Is you gain set at 11x? From what I've gathered, JH13 Pro is extremely sensitive. One customer have also had the problem of too much gain for sensitive headphones, and I have provided the info that he need to set it back down to 1x by soldering two pieces of wire on. Is there any possibility that there are someone near you that can do the soldering for you (or if you can solder yourself), I can provide you with the information you need to set the gain to a lower value.


This is really making me think if I should sell it with a default gain of 3 or 5 instead of 11x... We test most of our headphone amps with ATH, Grado, AKG and ER-4p, it seems that they kept getting more and more sensitive models out as the time passes by.


Thanks

Davidi

Having a variable gain knob would be nice.

Indeed, but that would involve dragging out the feedback wire to a pot of some kind, while when it works, it would work fine, but the added length can cause instabilities in some amps. On the other hand, if the pot got old and worn, most produce some kind of scratching sound, but if you put a pot there and the contact goes bad, it instantly goes to max and then down. Which can be really distressing for the users. (I think some REALLY REALLY old MF amps does that, and from what I gathered, they didn't do that anymore and this kind of design seems to only happen in a couple of machines that they ever produced.)

Other than pots, there are a couple of ways of doing variable/selectable gain.

#1 Fake it: Build an attenuator circuit in somewhere and use it go lower input signal's strength. The amp sees a smaller signal, and the user perceives a smaller signal, and think that the gain is smaller, but it was actually the signal that had been attenuated. This method while would make the volume smaller, it will not really help if the noise is picked up somewhere after the attenuator.

#2 Switch it: build a additional parallel resistor to the gain resistor and put a switch on that, when the switch is on, a 2 resistor parallel circuit is presented to the circuit and an lower effective resistance results in higher feedback and thus lower gain.


I'm thinking about doing something about the method 2, but the current case and circuit board design des not allow it unless we drag the feedback wire out (which opens that can of worm described in the first paragraph).



BTW, the batch of transformer has arrived and the final build process will begin tomorrow. (Gotta check the transformers for any possible damage before the build starts.)


Thanks

David

Latest update on HA-006++:

All components are now in stock and updates to the original chassis are being done to accommodate the larger parts of the ++ version.

Chassis update should be done today or tomorrow, and first 10 units should be able to get out of the door by Thursday this week.


Thanks

David

Just finished hand deburring the enlarged RCA mounts on the chassis and the transformer mount. Now I'm cleaning them with 95% ethanol to remove any kind of smudge or whatever dust that got attached to the bare chassis, then use touch-up paint to seal up the bare metal exposed by the cuts to enlarge the mounting holes on the chassis.

Was planning to use the drill bit to deburr the cut, but the already formed chassis does restrict the angle that the bit can enter, so hand deburring it is. :P


Will update again when the first units are being powered up and tested.


Thanks

David

Any issues with loud popping noises when turning the stepped pot? Heard of some stepped attenuators exhibiting such a behaviour, would like to know. Very interested in this amp.

The popping is very minor with this stepper that I currently use, this pot appears to be much better designed than the ones I've used before.  Where most other steppers produce a loud "POP" or "BOOM", this one produce pop as well, but to a much lesser and easily ignorable degree.

 

I have used other steppers before and I would not for a second consider them due to the popping or the way that the steps are set so far apart.  For some reason, even tho this one have only 21 step, I find it quite easy to set it to something that is very very close to what I wanted in volume.  This is why I decided to incorporate it into the design, or else I would have never considered it. :)

 

 

One interesting bit of info with the production of HA-006++, the potted center of the pre-production transformer is measured and that a M6 bolt with 30mm of thread would work just fine and looked great.  Well, when the production ones were made and shipped to me, the potted center is just a little thicker than what 30mm bolts would handle.  Now I got to go and get the proper bolt before the unit can be fully assembled. :P  I believe I can have all the pre-production unit shipped by Monday, and there will be a few 1x gain, 3x gain units ready made, so that anyone who want custom gain would not need to wait for the custom setting to be done. (Of course, that is only valid while we have those ones in stock.)

 

 

Thanks

 

David

Sounds good. Very very interested in it, especially with the Gilmore Lite being out of production now.

Okay small update. I thought it was so weird since I know someone else who has this combination and it doesn't hiss at all (only at high volumes).

 

I'm certain now the problem is with the power in my house. Before I had it plugged into a surge protector and I just unplugged it... and voila problem solved... or so I thought. If I leave it on for 5 minutes then the noise comes back... damn you power!!!

 

I'll keep experimenting with different plugs though, hopefully one will give me something clean. It's definitely not the amp's fault.

I'm relieved to hear that HA-006++ wasn't exactly at fault here, but I'm thinking, could it be some switching power (either from appliances, computers or whatever) or switching wall warts that's generating and injecting noise into the power line?

 

The info on how to mod it to lower gain is in the mail, I don't feel I did a good enough job of explaining it, if you have any questions or doubts on the procedure, please let me know.

 

 

Thanks

 

David

Final assembly is going well, I should be able to post the photo up in a day or two.  Yay! :)