Hagerman Bugle2 DIY Kit Phono Preamp

[audiopile]

So - why the back Satan reaction to feedback ? Simply -history. Early SS amps n preamps used lots of negative feedback -and are only classics 'cause they are old and sorta rare. The remnants of the tube age were lots noisier and just a whole lot more pleasant to play your music thru . Let's look for a simple easily researched explanation : Since those early SS needed a fair amount of neagative feedback to avoid issues like small fires - it must be feedback that sounds bad . Really too bad it isn't that simple.

 

[Jake71]

It would be interesting to see a measurement of the input impedance and capacitance as those parameters can affect the upper frequency response of a phono cartridges quite a lot.

 

[SegaCD]

Hey folks, I was the one that sent this unit in. It was a kit that I assembled. I just received it back from Amir and due to the unusual results, I opened the unit up to make sure everything looked OK. I noticed cold soldering joints on a few of the electrolytic capacitors (namely C10, C14, C18, & C17). These capacitors are used for decoupling across the opamps so it is possible that the cold joints may have raised the noise floor in the circuit. The resistors looked OK but my soldering was messy. 4-layer PCB + 80's-era temperature-locked soldering iron + expired solder = unreliable connections! Surprise! How far I've come since those days...

Long story short, I sent the unit in since I used it for years for audio capture (Youtube/archival) and thought the sound quality was excellent for the $100 I paid for the complete, unassembled kit from Kickstarter back in 2013. Since I do not know whether the cold solder joints appeared before or after transit, I am concerned that the unit may not be indicative of the true performance of the product (as others have commented). The product does have an excellent, 4-layer PCB design and at $39 for the bare PCB using off-the-shelf parts, it makes for a great project that is quite useful in a system where portability, space, and/or maintainability is paramount. I really don't want what could purely be my mistake to hurt a company which made one of the most useful devices I've ever owned (and a generally fun kit to build if you have the right supplies).

I hope someone could send in a pre-built unit and eliminate the human variable.

It should be noted that even with these flaws, the unit's noise floor still falls below that of pretty much any LP's surface. That RIAA curve is unfortunate though.

 

[theglobalelite]

I noticed my new Denon X4700H has an input labelled "Phono" and now I'm a bit curious vinyl-curious. I've never owned any vinyl or turntables and it looks like it might be fun endeavour (I promise not to go crazy). Would this device or any other phono-preamp be a upgrade to the Denon's phono-in, or is it for systems that don't have an AVR with that input?

Bueller? Is a dedicated external phono-preamp something I want if my receiver has a phono input?

 

[audiopile]

Basically the phono section in surround sound receivers is a afterthought (-unless someone can point a specific example out to the contrary?) - they are not as capable as a dedicated outboard /external phono preamp CAN be. But assuming there's actually phono EQ as part of the input on the X4700H labeled phono- I'd start with a HOMC or MM/IM (magnetic) cart run into that and see how you like it ? Most likely the Denon uses some variant of the NE5532 chip -cheap.well understood and capable of letting the music thru. There are things about LP enjoyment that are simply noticeably different than digi sources (surface noise) -get a decent cart mounted on as good a tonearm/table as you can afford and listen. Most of us ol' fart analog fans have developed the ability to ignore a fair amount of LP racket and listen to the music. I call this analog ears. But if you can't ease into the enjoyment of the music on LP's and teach yourself to filter out the inevitable occasional ticks n pops - a possibly more capable external phono preamp won't do much about source noise.

 

[Neddy]

Hey folks, I was the one that sent this unit in.

Thanks for sending this in! I have the same one, built from the full parts included kit he sold.
I spent years doing 'professional' PCB assembly, so don't think I had any assembly issues. He did send me some replacement parts (resistors?) (after I'd assembled it) to fix a gain issue, I think?
I'd be fine with sending it in, but doubt it'd add much to the discussion??

I thought it sounded just great (at the time), compared say, to the pretty dang good phono section on my vintage Sony TA2000F preamp.
I just recently got it connected again, and have to say, having gotten used to my all digital W10+OktoDAC system, even with the SME arm and fairly new stylus....MEH. Noise, clicks, pops...all with brand new, recent, never been played 'a-phile' vinyl - no thank you.
Considering selling off the whole magilla....though it's kind of like a puppy I've had for 40 yrs

 

[scott wurcer]

I consider it engineering malpractice not to use it in phone preamps frankly.

I would consider specifying MM phono input noise with the input shorted worse. I use MC or low inductance MI myself so it doesn't really matter to me, but I assume the difficulty of specifying noise for each cartridge as a load has not made the "cold" resistor technique that popular in phono pre-amps. Tape recorders are a complete system with the tape heads not a user choice.

Digital EQ works fine especially with a decent field recorder battery isolated from everything else. It would be nice to be able to easily compare different playings of an LP but as Heraclitus said, "You can not step in the same river twice".

 

[audiopile]

As far as phono noise goes - I admit there is something seductive about really quiet phono stages, BUT -realistically a whole lot of phono preamps are as quiet as they need to be given the inherent limitations of even a new ,unplayed LP. A much tougher issue to spec/test for is immunity to AC hum field(s) and RFI from the crazy variety of electrical devices that " leak " into our environment. Spent decades living and repairing audio equipment in our local antenna alley -random RF noise levels led to conversations with designers where they'd have me double check what my meter or scope's settings were. I have come to relie on reputation for avoiding enviromental/RFI problems. Has the manufactorer sold at least a few hundrerd copies of this product ? If the internet is pretty silent about noise issues (other than plain ol' hum -often my old buddy the ground loop.) -that might be worth listening thru ?

 

[carlmart]

Here's a simulation I made from the Hagerman Bugle 2. The program doesn't allow to upload .asc files, so anyone could try it.

 

[rongon]

Hey folks, I was the one that sent this unit in. It was a kit that I assembled. I just received it back from Amir and due to the unusual results, I opened the unit up to make sure everything looked OK. I noticed cold soldering joints on a few of the electrolytic capacitors (namely C10, C14, C18, & C17). These capacitors are used for decoupling across the opamps so it is possible that the cold joints may have raised the noise floor in the circuit. The resistors looked OK but my soldering was messy. 4-layer PCB + 80's-era temperature-locked soldering iron + expired solder = unreliable connections! Surprise! How far I've come since those days...

Long story short, I sent the unit in since I used it for years for audio capture (Youtube/archival) and thought the sound quality was excellent for the $100 I paid for the complete, unassembled kit from Kickstarter back in 2013. Since I do not know whether the cold solder joints appeared before or after transit, I am concerned that the unit may not be indicative of the true performance of the product (as others have commented). The product does have an excellent, 4-layer PCB design and at $39 for the bare PCB using off-the-shelf parts, it makes for a great project that is quite useful in a system where portability, space, and/or maintainability is paramount. I really don't want what could purely be my mistake to hurt a company which made one of the most useful devices I've ever owned (and a generally fun kit to build if you have the right supplies).

I hope someone could send in a pre-built unit and eliminate the human variable.

It should be noted that even with these flaws, the unit's noise floor still falls below that of pretty much any LP's surface. That RIAA curve is unfortunate though.

I was wondering about the power supply noise issues in the review. Thanks for bringing this up, and for the update.

I built my Bugle back around 2005 or so. It's an original Bugle, not a 2 or a 3. I originally ran it from a pair of 9V batteries, but pretty soon I splurged for the +/-15V DC linear regulated power supply pcb. It's quite simple, using just a pair of LM7815M 15V voltage regulator ICs. I have the audio PCB and the PSU PCB with power transformer housed in separate steel enclosures, connected by a short umbilical. They stack on top of each other, separated by stick-on rubber feet. Hum from the transformer or rectifiers shouldn't couple through the enclosures.

Doesn't the Bugle2 use a switched-mode power supply? It could be that the SMPS allows more noise through than the linear supply, especially if the power supply is not housed in a separate shielded enclosure. Also, an SMPS would supply a single positive DC voltage, not a positive supply and a negative supply like the old Bugle linear PSU. I wonder if that makes much of a difference.

I am not a professional-grade solder-slinger, so I doubt my kit was made to the high standards this group demands. Also, I used a few 'magic parts' that don't fit on the audio board very well, namely Nichicon MUSE electrolytic capacitors for local decoupling from the power supply, a couple of polystyrene film capacitors in the RIAA EQ, and a couple of 0.68uF 250V rated polypropylene film caps before the last op-amp (sized up from the 0.22uF 50V stacked polyethylene film caps specified in the kit). I don't know if people will savage me for using those boutique parts or for changing the coupling cap value. Otherwise, all the parts are standard-issue metal film resistors and even a couple of carbon film resistors.

I put a longer time constant in the interstage RC so the preamp responds lower in frequency. I don't have low frequency rumble or oscillation problems from record warps, and I believe the preamp sounds better with the response going lower in the bass. The preamp is subjectively quiet, but again, I don't know if it would pass muster with this very critical group here.

I only have a Schiit Mani to compare right now. I find the Bugle sounds subjectively cleaner than the Mani, even though the Mani uses a similar circuit with op-amps and passive RIAA EQ sections in between them. Does the Mani use only two op-amps with an all-in-one-go EQ section in between them? Or does it use three like the Bugle does, with the EQ split up into two sections (75uS and 2122uS)?

Anyhow, I hope you can clean up those solder joints and continue to enjoy your Bugle2.

 

[carlmart]

This time I zipped two LTSpice sims of the Buggle 2.

See if you can run it and what do you think of them. The load is to simulate a Shure V15 III, as well as anti-RIAA.

 

[rongon]

I opened up the Bugle2 AC sim.
Does the Bugle2 use that circuit with the RIAA equalization implemented in the feedback loops of the op-amps? I could have sworn I've seen a schematic for the Bugle2 showing that it's made of three op-amps, each with a *passive* EQ section in between.

Nice model for the V15 Type III cartridge. How did you arrive at that?

 

[carlmart]

I'm not sure where I did get that schematic. It was here in the web, of course. The 3 opamps veersion sim gave quite poor results.

The model was suggested by two members of the DYAudio forum, in a recent RIAA thread:

https://www.diyaudio.com/forums/analogue-source/361600-riaa-preamps-versus-real-loads.html

If you are interested in RIAA, some interesting ideas came up there.

 

[Jim Hagerman]

The opamp selection is not optimal and one should always use an active 47k ohm load to minimize noise.

I don't understand this comment. Why is the 47k loading resistance so important regarding noise floor?

Once turntable is connected, then source resistance (and hence noise) is primarily defined by the cartridge. For example, if cartridge coil has 500 Ohm ESR, then we have 500 in parallel with 47k, or roughly 495 Ohms. THAT is the source of "hiss"! We're talking about a 20dB difference here...

The LM4562 opamps provide excellent fidelity and very low noise. Especially for the money! What else out there is significantly better? Keep in mind this is a bang-for-buck product, not a cost-no-object-state-of-the-art reference.

 

[LTig]

I don't understand this comment. Why is the 47k loading resistance so important regarding noise floor?

You might have missed the word "active". There is a technique to use an opamp to emulate the loading which creates less noise than a simple resistor.

 

[pma]

I don't understand this comment. Why is the 47k loading resistance so important regarding noise floor?

Once turntable is connected, then source resistance (and hence noise) is primarily defined by the cartridge. For example, if cartridge coil has 500 Ohm ESR, then we have 500 in parallel with 47k, or roughly 495 Ohms. THAT is the source of "hiss"! We're talking about a 20dB difference here...

The LM4562 opamps provide excellent fidelity and very low noise. Especially for the money! What else out there is significantly better? Keep in mind this is a bang-for-buck product, not a cost-no-object-state-of-the-art reference.

Inductance, inductance ……
and opamp input current noise, in case of BJT input opamp. Important in case of MM cartridge.

 

[pma]

You might have missed the word "active". There is a technique to use an opamp to emulate the loading which creates less noise than a simple resistor.

Active damping works to get pure numbers, but once the needle is in the groove, there is no difference as everything is masked by groove noise. As almost always, these parameters have no practical value.

 

[Jim Hagerman]

You might have missed the word "active"

Didn't. Active or not, noise is dominated by cartridge, not 47k.

everything is masked by groove noise.

Yup.

in case of BJT input opamp.

That is exactly why I chose JFET input opamp. Do not want any dc bias current going through coil.

 

[carlmart]

That is exactly why I chose JFET input opamp. Do not want any dc bias current going through coil.

And you were absolutely right.

 

[carlmart]

This time I zipped two LTSpice sims of the Buggle 2.

See if you can run it and what do you think of them. The load is to simulate a Shure V15 III, as well as anti-RIAA.

I just checked the sims I had uploaded, and they both the same: simulate psrr. Nos I enclosed AC simulation and noise. Check them