[guest3264]

Hi folks,
I picked up my bugle boards today - so expect a flurry of posts. Enthusiastic diy builder combined with a sorry lack of knowledge.

Question 1.  - I am currently using a BenzMicro Silver High output moving coil. The stats are - Output 2.0mv and the information suggests a loading range of >1000 ohms. As I look at page 8 of the manual - paragraph 3 suggests adjusting R16&R34 to "solder in whatever load resistance you need".

Is this telling me to add 2 extra Resistors at R16&R34 as 1KOhms?

The next issue is one that I probably can answer myself. I have 4 extra 0.1uf Auricaps (630V) which I would be happy to use. It may be tough to squeeze them into C8 & C11- they have long leads to make it easier. But would the use of a 630V vs a 50V cap be an issue?  Ofcourse the same question goes for the other pp caps - while for the pennies I'lll pick up some BlackGate std's for the C7,c10 positions.

Next any use in bypassing the 25V 4700uf & 470uf caps in the PS?

thanks - steve aka sapdog.

[hagtech]

For the 2mV cart, I'd go with about 44dB.  Use gain resistors of 1.0k.  And I wouldn't put any extra loading on it.  Leave at 47k, I think you'll like it that way.  You'll get a bit more shimmer and air on top.  If it's too much, you can then bring it down.  

I don't recommend wasting auricaps for supply bypassing (not in this particular case).  The idea is to have low RF impedance - the lead length alone creates enough inductance to make the cap worthless.  Needs a cap to fit tight with no leads.

Doesn't help to bypass electrolytics in the PS.  In fact, it can cause instability (oscillations) with some linear regulators.  Not this one, but most LDOs.  Best place for bypassing is right where the signal is (keep current paths short), and that's C8 and C11.

Really, there's not much you can do with the standard Bugle to improve it.  Aside from a chassis and better connectors, the only improvement would be with C3, C2, C1 locations, and the recommended parta are really quite good.  Or you can change opamps.  Some people like the OPA2604.  You could lose the sockets too.  

jh

[guest3264]

Jim - thanks for all the advice, it is much appreciated.

[guest3264]

Hi - well I 've got it almost built both the bugle and PS boards.
I am putting them both into a simple Hammond Chassis which is quite tight. (I would post a photo, but my digital camera is on vacation).

Anyway I am wondering about heat inside the chassis and think I should put some holes under the PS board directly below the heat sinks and also immediately above the heat sinks to allow airflow through the chassis.

My question is - is this necessary - or does the ps run relatively cool?
My other question is when putting the opamps into the bugle board I take it that orientation isn't an issue.

Finally on PS-Bugle hookup - talked about in the other thread - but just to be clear (+15V goes to B1+) and (-15V goes to B2-).

Grounding- a floating-earth conundrum:
  - the PS ground connections between +15V and -15V  I should connect to the "earth" ground - from the power cord.
 - The Ground screw on the bugle is for the TT ground but is also ground for the board. Should I float this or also connect it to earth ground? And if connected to the earth ground is a small resistor advisable (eg 10Ohm).

sorry for such basic questions.

[hagtech]

No need for ventilation holes, the power supply run quite cool.  Opamps are directional, pin 1 should be towards the outputs.  B1 is positive supply.

You can run circuit board ground from near inputs to GND post on chassis.  Then also run Earth ground to same GND post on chassis.  Nowhere else, or you get a loop.

jh

[guest3264]

Jim - thanks for the info. I went ahead to complete the  build  before I got a chance to see the message anyway.

So I should say that the bugle+ps are sounding great - no hum, and I've got a big smile on my face.

The bit about the direction of the opamps is something I must have got lucky on - if you got them the wrong way around would it still work? It didn't look to me like there was a different pin shape to force a direction so I checked a couple of the bugle photo's from this board and determined the direction from the writing on the top of the opamp.

So far I've only run the PS ground to earth from the gnd next to the -15V. The Bugle circuit board is floating. I may test out some other options.

I rewired my old rega 3/Rb250 with cardas tonearm wire but haven't attached a ground wire to the tonearm base so I currently don't have a TT ground wire.  Interestingly I get a slight hum when I hold the head shell - earthing through my bones i guess - but it is quiet otherwire.

thanks again for a great little kit. Nice enough that it will probably be a while before I consider upgrading to a tube phone preamp.

steve small - Vancouver, BC

[hagtech]

The bit about the direction of the opamps is something I must have got lucky on - if you got them the wrong way around would it still work?

If put in backwards the opamps would likely smoke.  Or if you used the small 9V batteries, they would smoke.  Hazard of the trade.

Interestingly I get a slight hum when I hold the head shell - earthing through my bones i guess.

Yeah, people are not earthed, but act as large electron reservoir / antennae.  Your finger does a great job conducting stray power fields into the headshell.  Try doing the same thing with your other hand touching the ground terminal on the Bugle, hum will go away.

jh