[Build] CAPI BT50, 500 Series EQ (a la 550), Official Support Thread

[Thekahn]

Chris, send me an email thru the store.

Email sent. Thanks Jeff
Chris

 

[Riff0601]

Hi All
I did very well with the 2 vp28 and the Bt50, only that the Bt50 does not work for me as a line signal, I read that something has to be done with the jumpers, but I really do not understand what. Could you explain please, thank you very much

 

[jsteiger]

Hi All
I did very well with the 2 vp28 and the Bt50, only that the Bt50 does not work for me as a line signal, I read that something has to be done with the jumpers, but I really do not understand what. Could you explain please, thank you very much

The BT50 is line only. The recommended starting position for the two 3-pin option jumpers is shown in the below pic.
http://capi-gear.com/catalog/images/build/BT50/1_main_PCB/23.jpg

J4 is to select for a typical higher impedance load or a 600Ω load. There is appx 1.3dB more gain when set to 600Z.

Since the input of the BT50 is unbalanced, J5 will increase the BT50's level by 6dB so you can run it from an electronically balanced piece of gear and not loose 6dB.

 

[scotthundley]

Hey guys,

I built two BT50's  a few months ago and one works perfectly and the other has a few issues.  I've run tests tones through the BT50 have found that the  12.5k shelf doesn't boost or cut properly. It boosts/cuts starting from about 2k.  The 15k band in peak boost/cuts at 10k instead of 15k and then the 1.5k band actually boost/cuts at 10k.


Any ideas? Thanks!

-Scott

 

[RyanCat]

Hello guys,

i just finished a bt50. I think have a problem in the LF. In peak mod three of the five frequencies seemed to boost/cut not only the chosen frequency but the entire signal. In shelving mod i think everything works fine. I also think that the LPF does not work. In the other bands i have no problems.

Could you please give me some tips where i can look for troubleshooting?!

Thanks!

Jan 

 

[jsteiger]

Hello guys,

i just finished a bt50. I think have a problem in the LF. In peak mod three of the five frequencies seemed to boost/cut not only the chosen frequency but the entire signal. In shelving mod i think everything works fine. I also think that the LPF does not work. In the other bands i have no problems.

Could you please give me some tips where i can look for troubleshooting?!

Thanks!

Jan

Jan

Measure continuity between the LF Grayhill switch wipers and ground. Its possible that one of them is shorting. You will need to desolder that specific wiper and torque/push/slightly bend it a little to get some space above the PCB and resolder. It seems the width of the wiper pins are varying a little and some have rough edges on the bottom that are making contact to the top ground plane.

The HPF is at 50Hz so it might be hard to hear especially on smaller monitors. The only way to know for sure is to run a sweep or monitor level of a low frequency like 20Hz and compare with the pushbutton in/out.

 

[jsteiger]

Hey guys,

I built two BT50's  a few months ago and one works perfectly and the other has a few issues.  I've run tests tones through the BT50 have found that the  12.5k shelf doesn't boost or cut properly. It boosts/cuts starting from about 2k.  The 15k band in peak boost/cuts at 10k instead of 15k and then the 1.5k band actually boost/cuts at 10k.


Any ideas? Thanks!

-Scott

Sounds like you have mixed up some of the caps in the HF area.

 

[RyanCat]

Jan

Measure continuity between the LF Grayhill switch wipers and ground. Its possible that one of them is shorting. You will need to desolder that specific wiper and torque/push/slightly bend it a little to get some space above the PCB and resolder. It seems the width of the wiper pins are varying a little and some have rough edges on the bottom that are making contact to the top ground plane.

The HPF is at 50Hz so it might be hard to hear especially on smaller monitors. The only way to know for sure is to run a sweep or monitor level of a low frequency like 20Hz and compare with the pushbutton in/out.

Thank you very much for your advices. I try to fix it.

I meant LPF not the HPF. This one works as it should.

Jan

 

[jsteiger]

Thank you very much for your advices. I try to fix it.

I meant LPF not the HPF. This one works as it should.

Jan

Same situation applies. The LPF is @ 15kHz so it may be hard to hear. Its a 2 pole so down appx 12dB an octave which would mean -12dB @ 30kHz. so of course noticeably less than that in the audio band.

 

[scotthundley]

I did indeed switch some caps! I mixed up two .015uf caps with two .0015uf. All good now. Thanks Jeff!

 

[JeffTD]

Hey Jeff! Finished this one up last night and it sounds AWESOME, but I'm having one issue with the "bypass" I haven't seen mentioned by other folks. My "In' switch doesn't seem to do anything other than turn the red light on/off - the signal remains affected by the eq curves I've defined regardless of the position of the switch.

Have you ever heard of this kind of problem? Do you have any ideas for places I can begin to troubleshoot? It's a funny kind of issue in that I'm still going to use the unit even if I can't bypass it, but it'd be great to have for quick A/B comparisons.

 

[jsteiger]

Hey Jeff! Finished this one up last night and it sounds AWESOME, but I'm having one issue with the "bypass" I haven't seen mentioned by other folks. My "In' switch doesn't seem to do anything other than turn the red light on/off - the signal remains affected by the eq curves I've defined regardless of the position of the switch.

Have you ever heard of this kind of problem? Do you have any ideas for places I can begin to troubleshoot? It's a funny kind of issue in that I'm still going to use the unit even if I can't bypass it, but it'd be great to have for quick A/B comparisons.

I would look for a bad solder joint on the 90˚ header and/or the switch on the switch PCB. The FET circuit needs to be grounded to put the filters in their off state. Sounds like that is not happening.

 

[JeffTD]

I would look for a bad solder joint on the 90˚ header and/or the switch on the switch PCB. The FET circuit needs to be grounded to put the filters in their off state. Sounds like that is not happening.

Thanks Jeff! One other question - I could be overthinking this... upon further testing with some pink noise, the "In" button bypasses/enables the filters themselves, but doesn't bypass the 3 EQ bands controlled by the concentric pots. Is the "in" only supposed to toggle both filters on/off?

 

[jsteiger]

Thanks Jeff! One other question - I could be overthinking this... upon further testing with some pink noise, the "In" button bypasses/enables the filters themselves, but doesn't bypass the 3 EQ bands controlled by the concentric pots. Is the "in" only supposed to toggle both filters on/off?

No, "IN" removes the filters and the 3 EQ bands from being active.

 

[JeffTD]

No, "IN" removes the filters and the 3 EQ bands from being active.

Interesting, I've got some digging to do then. I've just re-flowed all the solder points on the board (switches, resistor, capacitor, 90º bracket), and am getting the same results; "in" only bypasses the HPF and LPF.  I can't see any extra bridging between other points on the main board that could be causing a connection that should be toggled by the switch instead. Both filters toggle on/off individually, and I can toggle both of them off via the "In" switch, but not the EQ bands.

 

[jsteiger]

Interesting, I've got some digging to do then. I've just re-flowed all the solder points on the board (switches, resistor, capacitor, 90º bracket), and am getting the same results; "in" only bypasses the HPF and LPF.  I can't see any extra bridging between other points on the main board that could be causing a connection that should be toggled by the switch instead. Both filters toggle on/off individually, and I can toggle both of them off via the "In" switch, but not the EQ bands.

Check the orientation of the 3 small package 1N914's. There are 2 on the main PCB and one on the mid PCB. Also the orientation of the 3 FETs. J111's IIRC.

 

[jona]

Hi,

i just finished 2 bt50 and both are working and  but both add a  good amount of hum to the signal..and when i press  the in/ bypass switch it produces a loud click... the hum is still there in bypass... i have two capi 511 vpr racks full of capi modules 312/vp26/vp28/vc528/LC53 and all have no problem with hum... what could be the problem? can you help ?

thank you,

jona

 

[Barklay]

Hello, Jeff and everyone here!

I'm building two of BT50's, one works fine, and second works on high and mid frequencies, but there is some troubles with LF.
For the frist time i’ve tried it - in 0db it's ok, signal flows, in all other gain boosts or cuts signal dissapears. i've tried to look at ground shrots, re-soldered. now in gain cuts signal still dissapears, and in gain boosts it is distorted and slightly boosted.

 

[jsteiger]

Hi,

i just finished 2 bt50 and both are working and  but both add a  good amount of hum to the signal..and when i press  the in/ bypass switch it produces a loud click... the hum is still there in bypass... i have two capi 511 vpr racks full of capi modules 312/vp26/vp28/vc528/LC53 and all have no problem with hum... what could be the problem? can you help ?

thank you,

jona

Might be opamp related or cabling outside of the rack?

 

[jsteiger]

Hello, Jeff and everyone here!

I'm building two of BT50's, one works fine, and second works on high and mid frequencies, but there is some troubles with LF.
For the frist time i’ve tried it - in 0db it's ok, signal flows, in all other gain boosts or cuts signal dissapears. i've tried to look at ground shrots, re-soldered. now in gain cuts signal still dissapears, and in gain boosts it is distorted and slightly boosted.

Check continuity from each of the LF Grayhill wipers (the metal tabs that stick out of the switch body) to ground. You are looking for a short or very low Ω reading.