Biketronics was finally able to get some new stock assembled on the BT355 and I received my new part last Friday. While waiting on the new BT355 to arrive I had already disassembled everything and removed the old Metra LOC and last night had a chance to install the new BT355.

Since I was using a new LOC I figured I'd pull out the trusty TPI 440 Plus oscilloscope, start at the head unit and work my way back to the AMP again to make sure that my gains were properly set.

With HU volume set to 13 of 17 sine wave looked good from the HU to the BT355.

With the HU volume set to 13 of 17 and leaving the BT355 at the default gain and HPF settings (as delivered) sine wave coming out of the RCA jacks of the BT355 looked good as well. However, one thing I noticed was the voltage output on the BT355 RCA jacks seemed low to me. At the default gain and HPF settings of the BT355 the RCA out jacks were delivering 1.107V +/-

I'm wondering if that is the nominal designed / intended output voltage or if my BT355 is faulty? I turned both channel gain settings on the BT355 to the maximum setting and the voltage increased to just a bit over 2.0V

I was expecting the output voltage to be around 2.0V at nominal settings, and 3-4V at maximum settings.

Has anyone here measured the output voltage of the RCA jacks on your BT355 with the HU set at 13 of 17 and the gain settings on the BT355 at the factory setting? And if so what were your readings?

Other than that, the BT355 seems to function OK however the left channel RCA jack was SERIOUSLY out of alignment with the case and it was a real booger getting the RCA cable firmly attached on that side. The thing seems to get pretty warm as well when running the HU at volume 13.

 

Hi,

Sorry about the RCA connector, we should have caught that.

Is your radio flashed for no amps? If it is flashed for amp/s it will be funny until flashed.

If it is flashed properly that seems low, how are you sending the 1k into the radio? If using a MP3 what bitrate and gain setting is the file? We set the level to try and get as clean as sound as possible up to about 80% on the radio. If we set it higher you would more voltage out, but a less linear volume response.

And I guess the last question would be how does it sound with our part set to default? Normally you would leave our setting how we send it and set the gains on your amp like normal.

Bill

 

Hi Bill.

My radio is bone stock (no dealer flash ever) on 2015 Road Glide with standard 4.3 HU. I didn't want to ever risk the dealer tech screwing something up so my radio has been off limits. Not that I know if it matters I'm running software version 1.19.1

1kHz test tone is coming from USB MP3 plugged into the factory radio USB pig tail.

1kHz test tone is 0dB amplitude and downloaded from JLAudio. Sample bit rate is 1411 kbps.

Everything sounds fine at the default settings of the BT355. I did make some fine tune adjustments on the left and right gains to get the outputs equal to one another. Both RCA channels are now outputting 1.125V +/-

Please don't read me wrong, I'm not claiming or complaining. This topic was primarily a question. I just happen to work in the Electronics industry and happen to have some pretty cool tools at my disposal

And of course, whenever you see a visual defect on the outside of something, you have to get curious as to what is going on inside........ So that was another pause and cause for worry on my part.

 

I am the same way, constantly doing tests to see what I can see. That is a little lower than we saw at the default settings but we did so many tests I don't remember the exact numbers, will find out though. I believe it was right around 2 volts. It is a little low compared to an aftermarket head unit but anything higher meant we ran out of volume control sooner and it did not feel right. Seemed better to have it low and have a smooth linear volume control with good usable range. At anything higher the radio would distort at half volume or sooner and the volume would ramp up too fast.

Bill

 

Just installed my LLs and since I am not usually a fan of default settings on anything, as it just seems boring, I was wondering if any of you guys have found the sweet spot with the LL adjustments.
At this point the sound is much better but I don't think the BT4180 and LL install is providing the volume that I was expecting. Pretty much the volume settings and DBs on my previous amp are the same on the BT 4180.

Thank for any ideas on how I can push this set up a bit.

Thanks in advance!!!'

T.

 

That 4180 should be screaming with the LL on default.
The only time I turned it up to 3/4 was on the highway going 80. Going slow at that volume would be painful. You may want to start checking connections. Where do you have it grounded?

 

Have it grounded to the HU per the instructions, ironically disconnecting a previous ground that was run to the ground near the battery.

I can hit 3/4 volume and not really even flinch.
HU zeros on bass and treble and one click to the rear on fade.

Thanks.

 

My previous amp was grounded directly to the battery and I used that same wire to ground the BT amp. I asked Bill and he said that was fine. I'm not saying this is the problem one thing to check. You should give Bill a call and explain the problem.

 

Hey TW. This may go back to the BT355 default gain settings on this latest batch of parts that Bill has built up. I've spent about five hours on this now and here is what I know (using TPI 440 Plus to obtain measurements).

My BT355 RCA output voltage measures 1.107V at default gain settings. Head unit volume at 13 clicks. Battery voltage 12.6V (fully charged +/-). Gain settings on BT355 at default (arrow pointing straight at the little round dot in the middle). By turning the BT355 gain to maximum I observed right around 2.0V RCA output voltage when I ran these tests Tuesday night. I re-ran the tests last night and the highest output voltage I could achieve was 1.56V. I can't explain the difference unless it was in the battery voltage between Tuesday night and last night (even though I've kept the starting battery topped off with my charging tender.

On my BT355 the output voltage stops increasing well before I reach the maximum dial setting on the LOC itself. Increasing the output voltage from the LOC will increase the resulting output volume from your AMP. My sine wave is clean at maximum head unit volume i.e. 17 clicks and maximum gain setting on the BT355. Perfectly clean.

My BT355 gets really warm - almost hot when running the head unit at 13 clicks and the gain setting on the LOC at default settings. The unit feels like it cools down if I increase the gain settings on the LOC to maximum, but I don't have an IR thermometer to confirm so I wouldn't call this a scientifically conclusive test. I am assuming that this heat is being caused by the input voltage coming from the stock HU versus the conversion / reduction taking place inside of the BT355. The energy coming in from the HU is higher than the energy being output by the BT355 (hence line out converter ) and that energy has to go somewhere. In electronics that energy usually dissipates in the form of heat.

I did notice that there seems to be more bass pass through when the BT355 is at maximum gain settings, versus default gain settings. And I think that observation is confirmed by Bill's statement above;

"At anything higher the radio would distort at half volume or sooner and the volume would ramp up too fast."

I haven't played around with the frequency settings on the BT355 at all, but I know that when using a HPF on a regular car audio AMP, your AMP output voltage will decrease (using 400Hz and 1kHz test tones) as you increase the HPF frequency.

All of this leads me to believe that the three stage filtering / circuitry inside of the BT355 is tied together somehow and that is how BT is removing, conditioning or lowering some of the more unpleasant frequencies that come from the stock HU on our bikes at higher volume.

If my AMP wasn't so over-powered for my speakers, I'd just adjust everything by ear and call it a day. But the maximum / proper gain setting for my combination of components results in way too much voltage going into my Kappas even though they sound good doing it Just not sure how long they would last like that and I tend to have a heavy hand on the volume ****.

I'm a little concerned that BT mentioned in a previous post that he had to order a bunch of new components from a new supplier in order to keep up with demand and I'm wondering if something changed in the component specification or quality of the components when that happened. I work in the electronics industry (OEM, re-manufacturing and factory service) and I've seen this type of stuff happen before.

I know that this is a long post so I'll get to the point. If your volume seems lower than it was before, you have two choices. Increase the gain settings on the BT355 or increase your AMP gain to compensate for the lower input signal. Although option #2 might not work for you if your AMP doesn't have gain setting adjustments. One thing that might be worth trying is to increase the gain settings on the BT355 to maximum and then try and dial in the BT355 HPF frequency in order to remove the distortion causing frequencies.

On my setup, my volume seems louder and clearer than when I was using the Metra or PAC LOCs as long as I properly match the AMP gain.

My full specs;
2015 Road Glide
Stock Head Unit
Cerwin-Vega B2
BT355
Infinity Kappa 62.11i

 

I think I might have broken the code, as I was a bit underwhelmed by this install of the BT 4180, the brackets, and the LLs.

Let me know what you think. Have to run this work around by my Audio consultants before I get too far down the road as I don't want to fry everything audio on the bike.