Bugle and PowerSupply (almost done) - help with LED ?

erimille · « **on:** 22 Jun 2004, 03:56 am »

I'm in the (hopefully) final stretch of putting together the Bugle and Power Supply. It's been quite an enjoyable experience

One of the final touches I'd like to do is hook up the LED on the power supply as a power-on indicator.

The voltage I get across LED+, LED- however is approx. 30 volt dc. Is this correct? If so, anyone know where to find a 30 volt dc led? 15 volt dc is the greatest I've been able to find.

Thanks in advance,

--eric

hagtech · « **Reply #1 on:** 22 Jun 2004, 06:10 am »

The open circuit voltage on the LED outputs is indeed 30V. But it uses two 1k resistors in series to limit the current. The LED (use any regular type or color) is a diode with some forward voltage drop (2V for green, 3.5V for blue). Once connected, it draws current through the 1k resistors for about 14mA current. That should make it pretty bright.

In short, just connect a regular LED to the terminal on the PCB.

jh

erimille · « **Reply #2 on:** 22 Jun 2004, 11:50 am »

Excellent! I'm back on it

Thanks!

--eric

erimille · « **Reply #3 on:** 23 Jun 2004, 08:18 pm »

The amp and powersupply are now connected and all of the voltages look good! The little blue LED power indicator even helps make this amp look good naked

now... to build a chassis... Er, question to all Bugle builders out there, what are you using for chassis?

Oh, and thanks again Jim! Excellent kit(s)!

--eric

hagtech · « **Reply #4 on:** 24 Jun 2004, 05:10 am »

Erimille,

Turn the Bugle board around. Face the inputs to the outside, away from the power supply. Quieter that way.

jh

erimille · « **Reply #5 on:** 24 Jun 2004, 02:47 pm »

Quote from: hagtech

Erimille,

Turn the Bugle board around. Face the inputs to the outside, away from the power supply. Quieter that way.

jh

Thanks for the suggestion! Quick (couple) of questions if I may ...

1) I'm curious why would this be quieter? (note it's surprizingly quiet right now

)

2) While I'm indeed getting music out of my bugle its not as loud as I anticipated. I set the gain at 50db but I don't seem to be getting this. Is this something that will get louder as it breaks in? Or (more likely) does this sound like I did something wrong.

Straight out of the box, this sounds *great* I just want more!

Thanks again for all of your help,

--eric

hagtech · « **Reply #6 on:** 24 Jun 2004, 06:54 pm »

It's just best not to put the VERY sensitive inputs right next to the power supply and its transfomer. Nice sources of hum or buzz.

Are you using an active linestage? Don't be afraid to run the volume control way up. Remember, volume is not a gain setting, but an attenuation. Minimal attenuation is best for sonics and distortion. Now if you've cranked it up to 3 o'clock and it's still not loud enough, you may then need more gain from the Bugle. Depends on the cart.

jh

erimille · « **Reply #7 on:** 24 Jun 2004, 08:19 pm »

Quote from: hagtech

It's just best not to put the VERY sensitive inputs right next to the power supply and its transfomer. Nice sources of hum or buzz.

The input wire is shielded which probably helps. As soon as I figure out the problem with the gain, I expect to switch this around based on your suggestion. I hear no hissing at all, so if it gets even more quiet than this, I'm all for it

Quote from: hagtech

Are you using an active linestage? Don't be afraid to run the volume control way up. Remember, volume is not a gain setting, but an attenuation. Minimal attenuation is best for sonics and distortion. Now if you've cranked it up to 3 o'clock and it's still not loud enough, you may then need more gain from the Bugle. Depends on the cart.

jh

I'm not using an active linestage. I'm (at this point) using a temp turntable -> bugle -> Decware Select amp [1].

The cartridge I'm using on the temp turntable is a Grado GR-3 (which I think is at 5mv). The volume pot is on the amp and it is turned all the way up. This combination sounds *much* louder on my other cheepo preamp (which has I think 33db gain). It's for this reason I think I did something wrong.

I built the preamp for 50db gain to handle my new (in transit) turntable with a MC cartridge rated at 2.5mv.

Debugging this a bit, I notice in the Bugle manual it states...

"Performance testing is possible if you have access to laboratory test equipment, but is typically unnecessary. You can do a basic test with a DVM by checking supply voltages on the opamps and insuring there is no dc offset at the outputs."

I have a DC volt reading of 0.04 on my right out and 0.0 on all the rest. Is this something I should be concerned about?

Regarding opamp measurements, I'm not exactly sure how to measure the supply voltages on the opamps, nor do I know what the correct voltages should be. If however, you don't recoil from ascii art and accept the opamps might look something like the following with numbers assocaited with pins...


1  -______-  2
3  -|  U |-  4
5  -|    |-  6
7  -|____|-  8

the measurements are

opamp #1 from 1->2 is 14.81 vdc, 7->8 is 15.06 vdc
opamp #2 from 1->2 is 14.81 vdc, 7->8 is 15.12 vdc
opamp #3 from 1->2 is 14.81 vdc, 7->8 is 15.06 vdc

measurements from 3->4 and 5->6 on these are 0.

Do these seem ok?

Err... and thanks in advance for the hand-holding ...

--eric

[1] http://www.decware.com/Select/select.htm

erimille · « **Reply #8 on:** 25 Jun 2004, 01:38 am »

Jim,

Another question if I may (and just to cover as many bases as possible)... I'm just wondering if I perhaps misinterpreted your email when you explained how to modify the bugle for 50db gain.

In order to switch to the 50db, one would change the 1.30K resistors found in R3, R5, R21, R23 to the 6.81K [1] resistors - correct?

The reason I ask this is I recently found your AnyEQ tool [2] (very nice!) and after plugging in 50db I see R3, R5, R23, R21 set with 0.707K resistors. Now I'm no longer sure...

I'm thinking that perhaps my misinterpretation of your email is what may be my problem.

--eric

[1]
http://digikey.com/
Part number: 6.81KXBK-ND
RES 6.81K OHM 1/4W 1% METAL FILM

[2]
http://www.hagtech.com/equalization.html

erimille · « **Reply #9 on:** 25 Jun 2004, 03:20 am »

Quote from: erimille

Jim,

Another question if I may (and just to cover as many bases as possible)... I'm just wondering if I perhaps misinterpreted your email when you explained how to modify the bugle for 50db gain.

Yep... a bit more investigation indicates this is probably the case.

It looks like I need the following...

http://digikey.com/
680W-1-ND
RES 680 OHM 1W 5% METAL OXIDE

not the 6.81K ... arrggg

(you hear the distant sound of a head pounding rhythmically against a desk)

--eric

hagtech · « **Reply #10 on:** 25 Jun 2004, 04:25 am »

Ok,

680 ohm is a nice round number. Get the 1/4W resistor size (681XBK-ND). The calculator may say 707 ohms, but hey, what's the difference between 50dB and 51dB?

Small dc voltages at the output are ok. You may get readings about +/-5mV. It's not perfect, but eliminates a sonically troublesome coupling capacitor.

jh

erimille · « **Reply #11 on:** 2 Jul 2004, 07:24 pm »

Quote from: hagtech

Ok,

680 ohm is a nice round number. Get the 1/4W resistor size (681XBK-ND). The calculator may say 707 ohms, but hey, what's the difference between 50dB and 51dB?

Not sure about the difference is but I know its *significantly* more than the 5db gain I was getting using the wrong reisitors.

Regardless, with the correct resistors in place this is now sounding *extremely* good driving my MC cartridge.

I am hearing (barely) an almost negligible hum now, so as soon as I can pull myself away from listening to this amp, I'll look into your advise and switch the amp around so the input isn't so close to the power-supply to help minimize this. I did try swapping in batteries for a while, but there seemed to be more 'there there' when using the power-supply. In the end, I suspect the dedicated power-supply with the reoriented amp will be the thing that works best for me.

Quote from: hagtech

Small dc voltages at the output are ok. You may get readings about +/-5mV. It's not perfect, but eliminates a sonically troublesome coupling capacitor.

Any ideas how to get this to 0? I'm only seeing 0.4 on the right outputs.

--eric

hagtech · « **Reply #12 on:** 3 Jul 2004, 06:09 am »

You could add offset nulling pot & resistor networks to the input of the final stage. But it would likely just add noise.

jh

erimille · « **Reply #13 on:** 24 Jul 2004, 03:01 am »

Quote from: erimille

I am hearing (barely) an almost negligible hum now, so as soon as I can pull myself away from listening to this amp, I'll look into your advise and switch the amp around so the input isn't so close to the power-supply to help minimize this. I did try swapping in batteries for a while, but there seemed to be more 'there there' when using the power-supply. In the end, I suspect the dedicated power-supply with the reoriented amp will be the thing that works best for me.
--eric

I finally got around to reoriented the preamp and the power supply. Further I decided to stack these boards (to save space) on either side of a http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=276-1499">radio shack copper pc board in an attempt to help cut down on any interference. This pre-amp is now much more quiet! Thanks for the reorienting suggestion as this as indeed paid off.

--eric

erimille · « **Reply #14 on:** 26 Jul 2004, 08:50 pm »

ok... so perhaps i'm not as done as i hoped

I'm experimenting with a Sumiko Blue Point special (high output MC: 2.5 mV, Load Impedance: 47k Ohms) and a Goldring 1042 (MM output: 6mV). I'm leaning toward the Blue Point Special (err.. today at least!

) and would like to tune this preamp to this cartridge.

I currently have the bugle at 50db gain. I noticed however, on a previous post you mentioning...

"... For the 2mV cart, I'd go with about 44dB ..." http://www.audiocircle.com/index.php?topic=11621&highlight=gain">(cite)

I'm wondering if 50db is an overkill for either of these cartridges and if it's worth trying and bring this down to 40db (or whatever)? Is the bugle *better* at lower gains or does it matter much?

thanks in advance (again!) for all of your advice,

--eric

hagtech · « **Reply #15 on:** 27 Jul 2004, 03:47 am »

I'd say 50dB is overkill for the Goldring. You'll be clipping the second gain stage. The drawback of a passive EQ topology is that you don't get a lot of headroom. The high frequencies can overload intermediate stages. This will result in a harsh and strident sound.

The +/-15V supplies greatly help in this area, but only by about 5dB. Minimum gain is always best for sonics and distortion.

The classic feedback style (one opamp stage) phono has inherently very high headroom and low noise. So if all you care about is the numbers, that's what you build. If you care about sonics and musicality, go with a Bugle.

Did you know the Bugle uses the same topology as the Cornet? Just with opamps.

jh

erimille · « **Reply #16 on:** 5 Aug 2004, 03:25 am »

Quote from: hagtech

I'd say 50dB is overkill for the Goldring. You'll be clipping the second gain stage. The drawback of a passive EQ topology is that you don't get a lot of headroom. The high frequencies can overload intermediate stages. This will result in a harsh and strident sound.

The +/-15V supplies greatly help in this area, but only by about 5dB. Minimum gain is always best for sonics and distortion.

The classic feedback style (one opamp stage) phono has inherently very high headroom and low noise. So if ...

I agree 50db is an overkill for the Goldring, but for the 2.5mV sumiko my calculations indicated 50db gain produced somewhere close to 2V output which I thought was about right...

That being said, I dropped this back to 40db which I've found to be more than fine for the Sumiko and I'm sure the Goldring as well. I haven't tried the Goldring yet, as I'm really enjoying what I'm hearing at the moment.

I didn't realize the Bugle and the Cornet were indeed the same design with opamps rather than tubes. Thanks for the info! I'm expecting (in the future) to swap out the Bugle for something tube'ish to complement my Decware SET amp... that being said, I'm surprisingly happy with what I'm hearing out of the Bugle, a few $$ and a bit of soldering is giving me. The Bugle has far exceeded my expectations. Thank you very much.

I'm curious, are there other opamps you recommend for the Bugle? Also, any recommendations / suggestions for break-in?

--eric