Here is my take on the balanced input LM3886 implementation.

Edited on 6-5-2022 with many small improvements to the schematics.
Edited on 7-16-22.
Edited on 12-23-2022

The gain for the LM3886 was eventually set to 10.

Circuit topology is an instrumentation amplifier. Balanced signal is fed into high-pass filter (100R, 100pF). We then have LM4562 opamp to provide impedance matching to the inputs of the LM3886. LM3886 chip amp is then fed two differential signals to its inverting and noninverting inputs and acts as a difference amplifier.

The gain of the LM3886 is set to 10 and is defined by the relation of the feedback resistor Rf = 20K and the input resistor Ri = 2K. Because we are using the chip amp at its minimum stable gain of 10, the stability network of Cf and Rfs is modified to omit the resistor. Otherwise, the gain of the amp is divided in two at the frequency of Cf and would equal to 5 - potentially a source of instability (in my opinion).

To ensure the HF stability two 27pF capacitors are added.

Resistors R8, R9, R10, and R11 determine CMRR or the whole circuit and should be at least 0.1% tolerance - this will allow for theoretical 66 dB CMRR. Better tolerances will allow for better CMRR, but will be limited by CMRR rating of the LM3886 itself.



Just a side note: 10K resistor has Johnson noise that is -112 dBU (across 20KHz range, at 20 degrees C) - according to this online calculator: https://www.daycounter.com/Calculators/Thermal-Noise-Calculator.phtml.

Feedback resistor Rf and input resistor Ri are both connected to the inverted input of the chip amp. To balance that, we need to mirror the same values for non-inverted input, except we connect resistors to the input and to the ground. This arrangement created what is known as a difference amplifier.

Since both input resistors are 2K we need a buffer to interface to the outside world and to be able to present at least 10K of impedance to connected devices.

Differential input resistance is 2 * 47K = 94K.
Common mode resistance is 47K + 2 * 2.2M = 4.447Meg.

For the balanced inputs the level of the signal is usually 4Vrms per channel. Half of that is 2. After RMS conversion 2 * √2 = 2.8284 Vpk. With the minimum gain of 10, the output voltage chip amp has to be able to handle is therefore 2.8284 Vpk * 10 = 28.284 Vpk. This is possible because LM3886 can be powered +-28V max into 4 ohm loads.

Dissipated power is another factor that determines maximum allowable power output by the LM3886:
Pd = Vcc^2 / 2* Pi^2 *Rload
For 28V supply and 4 ohms load: Pd = 784 / 19.7292 = 39.7380W
For 30V supply and 4 ohms load: Pd = 900 / 19.7292 = 45.6407W

Note that non insulated LM3886 can dissipate 40W without the fan, and insulated LM3886 can only dissipate 30W.

In our case, power supply is +-28V. We also need to subtract up to 5V for 4 ohm loads and 2.7V for 8 ohm due to chip voltage drop. 28V - 5V = 23Vpk of max output voltage swing without the distortion.

In the schematics input buffers are configured with the gain of 1+ 2 * 1K / 20K = 1 + 0.1 = 1.1. The gain of the differential stage is 10. Total gain is 10 * 1.1 = 11.

New in the box -$250 ( $400 retail)
Got a deal on Black Friday sale and passing it on . I hardly ever listen through headphones but had to buy something, yer know....

I've had a pair of Mission 782 as part of my system for the past 14-15 years or so and I still really like them. They needed the mid drivers replacing when I bought them but thankfully Mission still held spares at the time.

Recently I've been thinking about upgrading the speakers to the final SE spec, which included upgraded components in the crossovers and some newer tweeters. I missed out on buying some crossovers on eBay, but the seller suggested just upgrading the original ones with better components. What are peoples thoughts about this? I know some will say it makes no difference, but looking at the current design and components there seem to be some improvements that can be made.

The original crossover looks like this:


Tweeter and Mid driver


Woofer

I've traced it all out to this circuit:



The crossover points are supposed to be 195Hz and 2.5kHz

It seems to me that for starters the resistors could all be changed to wire wound resistors of suitable wattage (Mills or Ohmite), and then the HF cap changed to a more modern poly film from someone like ClarityCap. The back to back electrolytics that are bypassing the woofer are an obvious thing to change too. They are a cheap way to get a bipolar capacitor, but a real no-no in some design circles - so replacing both of them with a single bipolar 470uF electrolytic seems sensible.

I guess replacing the inline MF caps would also help, three larger electrolytics and a smaller film cap. My guess is that it is a cheap way to produce 102uF with the quality of the poly cap handling the higher frequencies. The electrolytics are cheap enough to replace while I am there, and again the film caps could be changed to some nicer ones from ClarityCap.

It is interesting to note that Mission themselves used better poly caps in the SE crossover, and dispensed with the back to back capacitors configuration for the woofer. Although it seems they incorporated a higher order filter for the mid section. The polarity of the woofer seems to be swapped too, the HF cap is a higher value as well (6.8uF).

Here is a picture of the SE crossover (x2):



I'd be interested to hear people's thoughts before I order some parts.

Hello all. First post on the forum. Im hoping to get some help with a dream build for my home theater from others more knowledgable than myself. I am lucky enough to have access to 5-7 Radia Pro 1.9 75 inch planar drivers and 24 x Faital 6FE100 6.5" woofers. My plan is to build a baffle wall with angled corners behind an acoustically transparent false wall and screen, with a 75" planar and 8 x 6.5" for each of the LCR. Determining cabinet volume, amplifier power, xover settings, etc are a bit over my head at this point but I am learning. I was planning to buy a VTV 6ch amp with the Hypex NC502PM modules, but Im not 100% sure it its enough power for 8x6.5" on one channel. I should have enough DSP channels for a bi-amped LCR. The goal is to eventually add 2-4 rear channels using the 75" planars and possibly a single 10-12" woofer per speaker. Anyway, this will take some time to purchase the amplification, AT projection screen, and building materials. But I plan to share the process once the build gets started. Any advice anyone could give along the way with the details would be greatly appreciated. Thanks in advance!

​

I saw a thread on here that was close to what I am looking for but not close enough.

Should I expect distortion in the 2% range , out of the first stage of a preamp tube with a u of 17 (12AU7)or so, given a low voltage supply like 30V at most? I know there is a ton of factors in distortion causes but should I expect to see ~ 2% at best for that low of supply?

Second question is how are most of you measuring distortion? And is anyone using LabVIEW for it? I have a Heathkit HD1 distortion meter that needs a restore but I got it working and it indicates my Sine wave generator has 1.8% THD @ 2KHz 200mv , LabVIEW shows it at 1.4% Pretty close considering the Heathkit is about 50 years old.


Alan

I have 2 power amps that I would like to bi-amp in my system. They have different gains.

So I took some measurements with my scope, and here is what I measured. Both amp inputs were fed with a 1 kHz sine wave, with an 8ohm dummy load across the speaker terminal.

Amp A:
Input impedence: 15kOhms
Input voltage: 330mV
Output voltage: 4.5v

Amp B:
Input impedence: 100kOhms
Input voltage: 330mV
Output voltage: 7.2v

If I use the following formula to calculate db,
Lv = 20 log10 V0/V1 db (see attached for better rendering)

Amp A:
Gain: 22.7db

Amp B:
Gain: 26.7db

So, does this mean I need to drop 4db to get the output level from both amps to be closer together?

Does the input impedence for each amp make any difference?
The output impedence of my preamp is 600ohm.

If so, would a 3db attenuator, like the Harrison product in the attachment be close enough?

I also watched a YouTube video from PSAudio, saying a voltage divider would work. I'm making assumptions that the attenuator is just that in a consumer friendly package.

Any help would be appreciated. Thanks.
Josh

I'm into seeing pictures of people's setups almost as much as doing stuff myself 🙂

I've seen only a few pics of Pensil's in the wild and would love to see more pics. I think the most famous ones are the one's from Grahams:



Post pics of your Pensil's or one's you've seen and post links if you have them 🙂

Scott

Selling linear power supply board that contains 4x6800uF 50V Nichicon Capacitors, Vishay 35A Rectifier Bridge with heatsink, LM317L / LM337L regulators for 15V out.

The board utilizes simple and straightforward design with two output voltages. PCB layout was optimized for high current flow for V+ and V- traces.

All components were sourced directly from the manufacturer or authorized distributors (TI, Mouser, Digi-Key).

Four 6,800uF Nichicon capacitors totaling in 27,200uF capacity
Up to 28V AC input voltage
Up to 40V DC output voltage
35A Vishay rectifier bridge with heatsink
16V regulated secondary voltage output based on LM317L and LM337L
Power LED connector with LED
Snubber capacitors for transformer secondary windings
Bourns 60V AC varistor for transformer secondary windings
Bleed resistor for main capacitors
Organic polymer capacitors for 16V regulated voltage output
High quality connectors accept 22 to 12 AWG wire
Board size 75mm x 100mm or 3’ x 4’

For LM3886 it is recommended to use an AC input voltage of 20V-22V to get 28V-30V out.
For TDA7293 it is recommended to use an AC input voltage of 25V to get 36V out.


I can ship anywhere in the USA.
Accept PayPal only.

What is the difference between fixed and non-polarized capacitors? I’m slowly learning things and can’t find it, other than how it’s represented on a schematic.

This amp is giving trouble booting up, even on an un-restricted PS. It boot/cycles about 2 dozen times before finally powering up 'fully', but its not right none-the-less.

I followed threads here: https://www.diyaudio.com/community/threads/arc-audio-arc2500-cxl.373647

The amp will only power up every time always if I lift R110/R181/R185/R128, and D23. I replaced U19 and didn't help.

Im getting little to no -17vDC regulated. Noticed both regulators run extremely hot, LM317, 337. I replaced both and put both into an insulated sync so that they won't overheat out of the sync.

Still not getting negative regulated voltage.

Rail voltage is OK at +-68vDC

What is P1 pot in the center of the audio side? its full CCW and doesn't seem to be changing anything atm.

Barely used pair of Faital 15PR400 (<10hr of home listening test with 5W ACP mini amp). I used knob 10-32 screws that leave no trace of mounting whatsoever. For all intents and purpose they are as new. Bought them in march 2022 at parts express for $280 each. Last I looked they were ~350 each.
Sold as pair for $500 + shipping (US only). Contact me if interested.
Thanks!

Sometime in the dim past I bought a pair of Audimation CPA 1 amps. Never heard of them? Not surprising, no one else has either, when you google them my own question on Reddit asking if anyone had heard of them comes up first. Anyway I bought these so long ago I forgot I had them until I had to move! These are monoblocks, sturdy little buggers at about 20 lbs each.

I've been using them on my bench doing speaker measurements for the last decade or so but they're getting kind of flaky, sometimes there's a big offset on the input, other times the bias is way off, typical stuff for old amps. So thinking I could repair them I took the cover off, and luckily for me there was a schematic inside. It turns out they're a pretty basic quasi complementary design, not really worth spending much to fix.

So then I thought I could use the chassis, heat sink and transformer to make something more up to date. The biggest problem I see is that the 2 output TO-3 transistors are on opposite sides of the chassis which means I'm looking at pretty long leads for at least one of the transistors.

Anybody got any ideas on a good use for these amps? I'm open to suggestion.

Looking to buy a pair or two pairs of strong 307a / VT-225 tubes

Going through my vinyl collection, I found this double LP that was a classic in my younger years. Poor Christ, every time people forget more about his sacrifice.... So I decided to listen to it one more time, but one of the sides (1 of 4) of the vinyl presents a noise that has been impossible to eliminate, it is a transversal scratch. (Yes, there are two kinds of fools, the one who lends vinyl and the one who returns it, in this case damaged) As always, the unbearable noise is in a silent passage - Murphy's Law does not fail! - . So, I wanted to listen to it on Tidal, humm, it's not there. On Spotify? humm, neither! And on You Tube? Wow, someone uploaded them and they sound great, no noise ! 😊 Eureka! But, the enthusiasm didn't last long, because I couldn't find side 4, at least in the original version, there is a Spanish version that is obviously not the same.😆 The lack of side 4 catches my attention, the guy got tired and didn't upload the last part? Is it a browser error? If someone finds it, I will be grateful if you provide the link.

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I'm pretty happy with mine two 3E audio running active two way digital all way with Purifi elements.
But I think maybe the weak point is the amp.
The HF could be better I think but don't know if I whant to put $1000 in
for example Purifi Eigentakt and don't hear any difference even if it's meassure better.
Whats your thoughts?

Most I can find seem fairly cheaply made, looking for a higher quality socket if someone has spares laying around

Have an Arcam Alpha 3 I'm no longer using. If anyone might have a use for it themselves or knows someone that would, it's yours. Pickup in Aurora, CO.

I have been using this Pioneer PL223 turntable for a few years, but last few months the speed has been fluctuating excessively. I have already tried re-lubricating the spindle shaft. Here is the schematic for the motor control.



It's a "DC Servo Control" system according the label on the turntable.

I am new to DIY audio and electronics, so although this turntable is not worth much I would like to fix it as a learning experience.

Will appreciate if anyone could point me to some information on this type of motor-control system and how it works (I noticed that unlike higher end turntables, there are no transistors or ICs involved, how is the servo control working here?) and any tips on how to go about troubleshooting this.

Ive made many mics but always used speakers or actual mic elements but I always wanted to build one completely from scratch. a thick paper cone is suspended by hair bands in the center two neodymium magnets are inside a xformer with the EI core removed,the output is good only 3 db less than an sm58 but poor response, flat to 1khz then drops off very rapidly over that. the cone doesn't matter I've tried many different materials and sizes and the response is the same I'm assuming its being limited by the coil.I havent used it so im curious how it sounds.

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Hi,
Are the STK series power amplifier ICs any good at all, maybe for a subwoofer amplifier.

It's a puzzle to me, but maybe it's obvious to some of you!?

Here is a situation: THD+N at ~ 4% before 10 kHz drops to below 0.1% shortly after 10 KHz.

Any chance any of you have the schematic for this amp? Gonna dive into it but would love to have a map.
Thx,
Jason

Does anyone know how expandable the expandable braided sleeving wire wrap is? I want to get some to dress up some cabling that is about 1/4 inch, so do I order the 1/4 inch sleeving and it will expand enough?

On Amazon

Hello everybody,

Is there someone who knows how to Crossover use to run this drivers?
I bought the Kit L15 of Seas but I don´t like it.
Thanks in advance,
Iñigo

I have a Tubes4HiFi ST120 Tube amplifier (Dynaco Copy) I built a couple years ago. I have a number sets of speakers that I like to audition from time to time. It is my understanding that you are not to disconnect speakers from a tube amplifier while it is running or for some time after you have disconnected power or damage will result?
Can I build a switch box of some type that would put 8ohm resistors on the outputs with the amplifier still on, while I switched speaker leads from one set of speakers to the other.
If "yes".....What type of switch or circuit would I build for such a device?

Thanks

Hello everyone,
I have at home a pair of new Altec_Peerless_NL-69176-1 transformers. Obviously this is vintage material.
They look like input transformers with 600 or 1200 ohms on the primary and 600 ohms on the secondary.
They are very nice, big and heavy.
But then I read "HYBRID TRANS". What does that mean?
The frequency is perfect for the audio band: 20-20,000Hz.
I also don't understand the other data on the transformers.

• Audio Level 1.5 watts
• 100mA D.C. max Zero Unbalance
• 500 V RMS test

Being (as they seem) signal transformers I don't think it is possible to run 500V and 100mA through them ...

Does anyone know these transformers, or even what they are used for, and where I could use them - if possible - in valve designs?
Thanks

If anyone has a spare floating around that's CONUS please let me know. trying to do some hands-on floorplanning before I invest in a case and/or machining.

Hi, I've received excellent help here before regarding replacing caps and transistors on vintage gear and would appreciate some more. I have a Technics by Panasonic SA-500 receiver that when switched to phono makes a constant, rapid popping sound that goes away when volume is turned down and increases when volume is turned up. I assume the capacitors and maybe transistors need to be replaced on the phono circuit board. Can anyone tell me which ones and good replacements for them? Found a tech schematic on hifiengine. Just need to know which components I need to replace and where to get them.

Thanks.

I have built 2 tube monoblocks PAs.

I wanted to listen to them and sonically decide what sounds better. I have about 4 variations to try out. One is with or without GLOBAL negative feedback etc. My issue is I'm having a hard time remembering and comparing what I'mhearing. Is there a way to record the output for later playback, making it easier to decide what sounds best?

I am looking for a current-production tweeter with high efficiency (95db+) with a frequency response flat between 5k and 20k erring on the side of "tilted up".
My budget is up to about $800 Canadian.

I am wondering if anybody can make suggestions I have not yet considered below.
Unfortunately I am one of those people who can tell when a tweeter is rolling off at 18khz... which rules out a lot of options such as the popular B&C compression drivers.

I am currently unhappy with the way my Beyma CP21/f sounds in my horn system, and I'd like to try some others. What I don't like about the CP21/f is that it seems to sound "sharp but rolled off..." despite extending to 20khz, it still lacks the shimmer I seek in most listening positions compared to other speakers i've experienced. I will be crossing over at 5.5khz

Here is the short list of the high sensitivity tweeters I have consider and their reason for not obtaining:

Hi And thanks for reading.
I am forever having to buy new soldering irons. The ones i buy last about 2-3 months then breakdown.
I use a soldering iron for about 2 hours a day everyday, they can't seem to handle the workload. Everyone else i know has irons that have lasted for many years.
My latest is a weller 40 watt which cost me 60 quid and lasted 2 months.
What can i do, which soldering iron can i buy that can handle the work load.
Thanks

Hi everyone!

Back in 1980, when I was designing and building my first “serious” stereo audio power amplifier, I found the safe operating area (SOA) protection circuit to be the most challenging part. After I was finally satisfied with the V-I limiter performance in stereo mode, I then discovered that it did not perform at all well when the two channels were bridged. When limiting was triggered, the voltage across the load would “snap” to ground producing nasty sounds from the speaker (please see the attached file for a simulation demonstrating the problem). I invested more time looking for a fix, but found none that were esthetically pleasing. As I never used this mode, I eventually lost interest in pursuing it.

Jump ahead 40+ years and this issue still nags me every now and then. There must be people on this forum who have come up with a good V-I limiter solution for bridged amplifiers. I know that most of you will say “easy, don’t use V-I limiting.” This response certainly has merit and may be the best way to go, but it does not really address the question. A well-designed V-I limiter extracts the most power from the output stage while providing reliable protection.

I know the this topic was discussed in the Amplifier based on 2N3055 thread but I didn’t see a solution if it was there. My searches may have missed other discussions. Does anyone have something to contribute?

Thanks in advance!

Bruce

Is there any consensus about whether Linkwitz LX Mini Style absorber stuffed cylindrical diffusers mounted behind OB midranges do anything beneficial for sound? It seems they are quite well hidden in the "shadow" of the magnet structure, so I can't see much energy making it into the cylinder. I made a crude set and didn't measure much difference to frequency response. Obviously, FR is only part of the story, or maybe I didn't stuff the cylinder tightly enough. However, I haven't noticed any other designs using this configuration, have they been proven to be useless?

As I understand the CS4398 it needs to work in software mode to set the DSD format, it not possible in the stand alone mode. If that's the case, what is the easies way to set the software bits, is it with a uP the only way or can a EEProm do the trick?

I'm thinking of to use the CS4398 with the XMOS DSD USB receiver, if that is doable?

Hello All,

I didn’t see a post or sticky about it which is kind of surprising-forgive me if I missed it. Anyway, I’m seeking guidance on buying my first PS as I get into building. My primary focus will be (no surprise) power amplifiers. I’ve already determined I’d prefer linear power but that’s about it. Would multiple outputs be very useful? What voltage and amperage do you recommend? What features are make or break for you? As I said, I’m just starting out so I don’t need much but I would also prefer not to outgrow it in a year or two. I don’t have a ton of money to throw at this, but I feel I can go up to $300. Thank you for your help and patience.

-The New Guy

I'm a newbie here. First post. My goal in this post is to gather the attention of some knowledgable amplifier folks as in a coming/subsequent post I'll be asking for some advice in troubleshooting a Parasound HCA-2003. Now, on to my immediate goal.

Shown is my stretched, dual mono, heavily POOGE-2 inspired modified DH-200. What else can I say other than it's been performing nicely for the past fifteen or so years. I'm the original owner. I do possess a second completely stock DH-200 yet, in my laziness, have never directly A-B'd them. With lots of inputs and outputs to my 5.2 system, it's a rather time consuming exercise to do that. My bad.

The modded amp is used to feed the mid/tweeter housing of B&W 801-II's. (Two channels of the aforementioned Parasound amp are used to feed the B&W's woofers.)

I'd be happy to check back here to comments/questions. Maybe some folks here can guilt me into performing the A-B exercise (with the stock Hafler and/or the Parasound).

I recently bought a new power transformer with a winding rated for 6.3V @ 5A. The winding is oversized as the amplifier will only be drawing 3A max of heater current. After testing it with the actual tubes which draw about 2.8 amps the voltage is extremely high at over 9 volts. Unloaded I read over 12V on the winding. Throughout all tests the HV winding was left unloaded, but I don't think it should matter that much.
I understand transformers are not perfect devices and there can be some fluctuation in the voltage, but this is not acceptable in the long run.
Is this to be expected and my order was too oversized or the transformer was wound badly?
I'm reaching out here as I may be able to ask for a refund or at least a fix if the transformer isn't supposed to be behaving like this.

Side note: assuming I can't get a refund or get it fixed, would it be cheaper to build a regulator (considering the trafo itslef costs about 50EUR)?
Keep in mind the space under the chassis is tight and I'm not looking to bring in that much more heat to dissipate.
I'll say that I'm slightly skeptical about the regulator as the current being involved here is fairly high and I fear the power wasted to heat would be huge.

On another DIY audio forum I read about placing a un-connected power transformer on top of or right next to the power transformer of a amp, preamp or other audio equipment. It is said to make the equipment sound better. The exact reason is unknown, but thought to have to do with the radiated field of the power transformer being influenced by the in-active transformer’s core material. This is easy to do with EI core transformers, just set a spare EI core transformer right on top of it. I have tried this and it does make the equipment sound better, more open and dynamic to me. Has anyone here tried this simple experiment? Most tube equipment has EI core power transformers.

I am looking for some UTC MQL-5 coils, new or used.

I will no longer provide EnABL kits (Nov. 21, 2016)

Edited March 20, 2013 re: shipping charges The USPS rates changed in late January. I discovered this the hard way. International rates have ~ doubled.

I assemble and provide a "kit", intended for the installation of "EnABL" patterns on loudspeaker driver cones.

This kit will include the following:

1) Speedball type B nib holder
1) set, A-1 through A-5 Speedball pen nibs (5 nibs)
1) #99 Speedball pen nib
1 oz. Microscale MI-4 Gloss coat
1 oz. Model Master Acryl flat clear (stealth finish)

Mailed in a 6" x 9" bubble mailer. The liquids will be enclosed in their own zip-lock bag.

For the tidy sum of $30. Others (outside US) for $38 (this was $32 before the US Postal Service rate change in January, 2013)

Preferred payment method is by paypal. This has been underway since 2008.

You will need to source the brush of your choice to install the Gloss Coat & containers to dilute the finish to suitable viscosity for application.

Subject to change.

I've had these for a while and I've never gotten around to building something. These are open box, as I tested them once. Price is $50 obo.

Hello,

I am interested in modifying my Schiit Freya +. Before i pop it open i would like to have a schematic on hand to better understand its circuit.

There are other schematics of schiit gear ive seen floating around but no luck on the Freya. Does anyone have a schematic of the Freya + or happen to know where i might find one? I am assuming Schiit does not hand them out on request.

In the past couple of years, I've spent a lot of times reflecting on the measurements performed by Erin at erinsaudiocorner and Amir at AudioScienceReview. In particular, that the shape of an enclosure has a big impact on directivity. Basically, as sound diffracts around the baffle of an enclosure, it reduces how much sound is radiated to the top, bottom, left and right of the loudspeaker.

See: https://www.diyaudio.com/community/threads/what-do-roundovers-do.303155/ and https://www.diyaudio.com/community/threads/the-preference-for-direct-radiators.330741/

Inspired by that, I made an XPS foam "stand" for my bookshelf speakers in my office. Up until now, my speakers sat on a speaker stand similar to the attached pic.

The XPS foam "stand" is basically four foam cylinders, each cylinder measuring 10cm tall by 7.62cm in diameter.



I wasn't expecting it to make much of a difference, but I was curious if it would be worthwhile to eliminate the surface below the speaker. In the measurements performed by Erin and Amir, we can see that the space that surrounds the speaker makes a big difference on the speaker performance. And when you put speakers on a stand, that's not 100% ideal, because the stand itself impacts the sound.

Again, I wasn't expecting much of a difference, and I nearly gave up on this little project because it was time consuming and made a big mess. (I had to cut sixteen pieces of foam, creating an absolute mess of XPS foam dust.)

But, lo and behold, the imaging of the speaker is noticeably better. I really wasn't expecting much, in fact I didn't even listen to it after I finished the project, because I didn't think that improving things on one side of the speaker would do much. But I turned on my usual podcasts this morning, and the sound of the center channel sounds:

1) more solid.

2) It's bizarre how the speakers don't even sound like they're there. It's really strange, it's like the sound isn't coming from the speakers.

3) The soundstage is deeper.

And I didn't move the speakers at all (except that they're 4" higher now, because of the foam stand.)

Of course, this begs the question:

Does it sound better because it's elevated above the stand, creating more "space" around the speaker?

Or does it sound better because the XPS foam is damping vibrations that would normally get transmitted into the stand?

Or both?

I've rarely used spikes on my subwoofers or speakers because I don't want to screw up my floors. Plus, spikes always seemed a little "tweaky" to me and I figured they were probably about as important as fancy loudspeaker interconnects.

But I have a hunch that the improvement in the imaging is probably due to combination of creating more space around the speaker and isolating it.

Back in the day, Geddes mentioned off hand that one way to isolate subwoofers is to suspend them. Basically put some hooks in the top of the sub and hang them from bungie cords, so that they don't radiate energy into the floor.



This little experiment definitely has me thinking that might be a good idea. Since the speakers are in my office, I don't really need to worry about WAF. Perhaps figure out where the studs are located in the ceiling, and then suspend the speakers from the ceiling itself, similar to how you'd hang a plant.

I got an incomplete overnight sensations MT kit.
Some components are missing. Resistors, capacitors and woofers.

I found parts that are missing.

They use hivi b4n 8ohm midbass.

https://www.parts-express.com/HiVi-...zMlouQP7fe8nNGgaNVLjoCqM67wWMWcBoCSH4QAvD_BwE


What will be an upgrade to this driver that will work with cross overs (need to find diagram for overnight sensations). 4-5" midbass.
What thiel parameters do they use when designing a cross over. Is matching 8ohm impedance and sensitivity values sufficient to search for a compatible driver?

Resistors are 6 and 10 ohm. But they use white ceramic resistors.. will wire wound mills be an improvement?

This is what's supposed to be in a kit
https://www.parts-express.com/Dayto...recision-Audio-Grade-Resisto-004-6?quantity=1


Also capacitors are Dayton audio but 5% accuracy.

I think Dayton has polypropylene 1% accurate capacitors

i tried a lot times in this code but i am so confuessed to write this code...can anyone write this arduino code.....

Troels has two 861 2.5way designs on his website with kits or just crossovers available from Jantzen.
These are much lower priced compared to Troels's regular builds, particularly the SBA kit.
In the UK, I can get parts for the Discovery 861 ( with standard XO) for £650 + some shipping
The SBA -861-PFCR with Superior XO can be put together for £430 + some shipping.
These prices exclude wood, stuffing, etc.

http://www.troelsgravesen.dk/Discovery-861.htm
http://www.troelsgravesen.dk/SBA-861-PFCR.htm

I would appreciate some thoughts on these designs, and whether the Discovery kit is worth the extra.

which OEM drivers are these? Looks like from EU.

I have a set of Corel Beta 8 that has not been used. I'm thinking of using it in a rear loaded horn cabinet. I have also considered a taped TL. However, I have read that TL puts a lot of pressure on the cone and it is therefore good if it is a fairly rigid cone. Since the cone is quite light, I think it is not suitable for that.

But what is really my question is that I would like to take the hard top end off (peak at about 10K). There is a diagram for a nocth filter, but I would probably rather make it as a 2-way. The obvious thing would be to supplement with a super tweeter, but after what I've seen that GR Research does, I'm more inclined to make it as a traditional 2-way and let an ordinary tweeter work down to maybe 2K Hz (Corel 8 also has af big dip at 2,3K). According to GR Researsh, cutting at very high frequencies is very, very critical in terms of placement in order not to get counterface. Danny shows an example with his own full tone unit. What is your experience, should you look at the fact that it is a full tone and then just use it as a normal mid-woofer or should you rather do like the Horning Hybrid speakers, they have a super tweeter from a very high frequency together with a Lowther. Is it because he tests with 1st order that placement is more critical since the overlap is greater.

But do I ruin the whole idea with that driver if I don't take advantage of the fact that it plays over the entire spectrum.

Regards
Henrik

Sorry in advance if this opens a can of worms but a side topic in another thread peaked my curiosity on this question.

I read in multiple threads (as far back as the search function goes) that some people suggest using a regulated supply on the "gainclone" is just waisted effort and others both here and on other sites claiming good supply regulation can actually improve sound, even going so far as swearing by it sounding superior.

I'm curious of peoples opinion who have tried both and actually compared by ear both at low and high volume levels.

My guess is that far many more factors play into this than just regulated vs. unregulated voltage, but I am sure there must be some unbiased opinions here that have actually heard amplifiers employing both types that were based on the LM3886/3875/1875, etc..

Look forward to reading the replies 😎

Hi, I have a tr200 on the bench these days with some serious noise issues, due to the behaviour of the noise I strongly suspect it to be a clear error somewhere, I just cannot see it.

If loudness is on everything is fine, except if I hit the Tape/monitor switch, then noise comes back.

If volume pot is all the way to max everything is fine, turn it 1/20 back down, noise is back, no gradual change, On/Off.

Character of noise is low frequency buzz, like ground loop I believe. Level of it is very high, around moderate listening level through the speakers, and the tone controls seems to do their thing with the noise, so it happens “before” that stage.

Probably worth to mention, “crosstalk” between inputs and output stage is very high. With no input selected I can still hear the music relatively loud and clear considering it should be quiet, this follows volume pot and can be turned up and down to some extent.

Amp has been more or less fully recaped, including those ,33uf in loudness loop.

All switches and pots have been given some contact spray without any effect.

Any ideas?

The following is from the website for Coherent Audio speakers:

The Coherent “XD crossover” is exclusive to our line. This unique system uses no resistors to pad down the compression driver to match the woofer section output. The woofer has one inductor in the signal path, and the compression driver has one capacitor and optional bypass caps on it. “Impedance Matching" is then used to make the two drivers act as one in the critical midrange 800hz to 2500hz frequency range.

Click to expand...

Does anyone know how this would work? To my (limited) knowledge, one could move the crossover point by varying the values of the inductor and capacitor in such a first order arrangement and in so doing find a point where the summed frequency response of the two drivers is closest to flat. But how would one overcome the differing sensitivities? Coherent uses Radian coaxial drivers and, for instance, the LF of the 5212B has a sensitivity of 96dB, while the HF is 107dB. How does one balance that out without using resistors?

Hi, I have some of those speakers:



They are not Hi-Fi, but electric bass and electric guitar speakers and I would like to know if there are some typical hi-fi cabinet configurations that can be adapted to those speakers to help in reproducing deeper lows.

Please consider that most guitar amps reduce their feedback in low (and high) frequencies to use the resonance of the speaker/cabinet to increase the reproduced lows.

I know that it isn't an hi-fi question, but the knowledged people about how to design speaker cabinets are here.
Thanks for any possible suggestion,

Kind Regards
Roberto

Hello to all. I recently bought an HSU powered sub to connect to my VTL IT-85 integrated amp. The IT-85 has a pair of pre-out L and R jacks. When I hooked up the low level inputs of the sub to the pre-out of the IT-85 I get no sound. I use an Audioengine B-1 Bluetooth Dac which is connected to an audio input on the IT-85. I tried an RCA splitter from the AE B-1 output and connected to the HSU sub and it works fine. The only problem is the sub is at a fixed level when using the IT-85 volume control. I want to have the pre-out connection working so I have a variable volume level. Any ideas why the pre-out isn't allowing the signal to go from the IT-85 to the sub?

I get some transformer from my friends when he clean the warehouse. The transformer seem like output transformer with siemens logo. I can't find any data from google. Maybe someone can help me figure it out? The code was 71/1514, 71/1811 and 71/1516. Thanks for any help.

I have a pair of Axi 2050 for sale. 2" compression drivers. Based in UK so prefer UK sale.
They were bought fromm Nigel at Lean Business and have only ever been used in a home hifi situation. No PA use at all.
All original packing and will be double boxed.
Pictures are available on request.
After £1200 plus postage.
Keith.

Anyone got some 3a5 valves for sale in the EU preferably? Looking for 4 or 6.....

Greetings,
I have an Holfi integra amplifier, ver.1.1, I bought it thinking it would be an easy fix, but I didn´t expect to find every transistor on the power amp circuit replaced.
Can´t find any documentation online, I drawn a schematic to help me repair it. The output transistors were shorted so I replaced them, still it had full DC on the ouput, then noticed the first transistor (T1) was a 2sc2240GR and it needed more gain to get the proper bias, so I got a 2sc2240BL and solved the problem.


Now the only problem I have is no bias current on the output transistors and I find it weird to see a darlington BC879 as vbe multiplier (T6) that measures as a PNP instead of a NPN, and the pinout doesn´t seem to match the circuit board.


Does anyone know which is the original transistor? Is it viable to replace the base resistors and the transistor to a single npn instead?



Thanks.

Thanks to Planet10 for his design for my ff85wk/Blanda bowls. A friend with a vertical mill helped me machine the surface of one flat to mount the driver. Although I plan to cross them to my RS225-8 in 42 liter BR, I gave them a listen today running full range and was very impressed. The inner sandwich vent is a little tricky but do-able. I'll report back with my results on the 2-way version. Thanks again Dave.

Hello everyone,

I’m new on this forum and a novice regarding DIY audio stuff.

I recently bought a Polk R700 and a MiniDSP flex TRS which I love but then had not enough money for the amplifier. I started to look for cheap amplifier with clean output and around 200w@8R.

I came across Hypex NCore, IcePower and Pascal but even those where to costly to afford in kit. I started to look in old amps and by chance read about the Monacor IMG stageline STA800D (dual mono hypex UcD400OEM) and was able to buy one for 350€ new.

I would say that I’m 80% satisfied with the sound but that I would prefer to have a little more of “air” and resolution from the amplifier. I also want to keep THD and noise as low as possible until fed to the UcD400 module. I immediately thought of replacing the TL072 on the hypex integrated input buffer by the OPA1612 which has this slightly “airy” presentation as well as a lower THD than what the MiniDSP output is capable of.

But I don’t know anything related electronic schematics and choice of components. This is why I would be grateful if someone could look at UcD400OEM and tell if replacing TL072 with OPA1612 would work ?

I have 4 x BB1704, slightly used. $300 + pp at cost obo.

I’m located in Norway.

Pictures tomorrow.

Regards
RMalmin

Hi Guys,

I have had this project in the pipeline for a long time and finally getting some progress made on it. It will still take a while for the project to be completed but I thought I would start to post some information as a build log.

I really like the tall and thin format and think that it will fit in very well as a living room system. Inspiration came from Wesayso’s Two Towers build and the feedback on that design has given me new motivation to get going with mine. Other designs from OPC, Koldby, Halair and one I found on a Scandinavian site have all provided a wealth of information and different strategies to use.

Parts Express had a sale on TC9 drivers and after somewhat of an impulse purchase I had more than fifty of them so I had no choice but to build a line array!

I weighed up all the pros and cons and decided to keep it simple because my other speaker projects have had a habit of dragging on for years. The design I have gone for is most closely related to OPC’s in that it is a rectangular box with five separate sealed enclosures to keep the possibility of pipe resonances down and to allow the series and parallel speakers to have separate volumes.

To make my life easier I designed a cabinet in MDF that could be cut by CNC and would enable me to assemble it fairly easily. I settled on MDF because it is cheap and relatively stable after it has been cut. Plywood would need to have been assembled almost straight away to avoid warping. Birch ply is almost unobtainium in Western Australia, the only place that has it is AUD$300 per 8x4 sheet. I have used Hoop pine ply before which is also very high quality but still $200 a sheet and because it is a softer wood it warps even more unless weighed down.

I also live in a more remote part of WA almost 1200KM from the capital city so transporting sheets of wood is either difficult or costly sometimes both.

I was in Perth for the birth of my son so I was able to get the CAD design done and I had my car to take the cabinet pieces back in so the plan started to come together.

The CNC Company wanted a 2D DXF so the plans were drawn up in AutoCAD, I later created a 3D model from the 2D sketches to verify that it all fitted together and luckily it did. This is the basic design and some shots and animations from Fusion 360.

Here is a link to where the impedance comparisons started as that was useful information

Full Range TC9 Line Array CNC Cabinet

Hi every body.and thanks members of diyaudio.
I love amplifier .all of them but class D special for me.l try for 3 month work irs2092 amplifier and result equal waste time and money .
First l build schematic in datasheet .i. Use exactly same part in schematic and supply and mosfet but never work.l use +-35 regulate voltage for supply.the problem is one of. The mosfet is all time On and DC voltage -37 volt in terminal speaker.
This schematic

Professor is describing several experimental inventions....

THE BOTTLE THEORY OF SOUND

I expressed my cheerful readiness to be banker to genius.

"Thanks," said the professor, pocketing the scrip and resuming his position at the camera. "When I have pictorially captured smell, the most palpable of the senses, the next thing will be to imprison sound--vulgarly speaking, to bottle it. Just think a moment. Force is as imperishable as matter; indeed, as I have been somewhat successful in showing, it is matter. Now, when a sound wave is once started, it is only lost through an indefinite extension of its circumference. Catch that sound wave, sir! Catch it in a bottle, then its circumference cannot extend. You may keep the sound wave forever if you will only keep it corked up tight. The only difficulty is in bottling it in the first place. I shall attend to the details of that operation just as soon as I have managed to photograph the confounded rotten-egg smell of sulphydric acid."

The professor stirred up the offensive mixture with a glass rod, and continued:

"While my object in bottling sound is mainly scientific, I must confess that I see in success in that direction a prospect of considerable pecuniary profit. I shall be prepared at no distant day to put operas in quart bottles, labeled and assorted, and contemplate a series of light and popular airs in ounce vials at prices to suit the times. You know very well that it costs a ten-dollar bill now to take a lady to hear Martha or Mignon, rendered in first-class style. By the bottle system, the same notes may be heard in one's own parlor at a comparatively trifling expense. I could put the operas into the market at from eighty cents to a dollar a bottle. For oratorios and symphonies I should use demijohns, and the cost would of course be greater. I don't think that ordinary bottles would hold Wagner's music. It might be necessary to employ carboys. Sir, if I were of the sanguine habit of you Americans, I should say that there were millions in it. Being a phlegmatic Teuton, accustomed to the precision and moderation of scientific language, I will merely say that in the success of my experiments with sound I see a comfortable income, as well as great renown.

Edward Page Mitchell, December 1875
(The phonograph was conceived in 1877, perhaps July, by Thomas Edison; working by December 1877.)

Hello

I am using a P-1a and P-3a (modwright II) which both have the option of using an I2s input and ouput. The stock cable is not that good but no one seems to make a sensible priced replacement.

I have been able to source some 999 silver teflon coated wire and deicided to make my own replacement but I do not have any details of the pin conifguration. I think that only four pins were used and one is not but not certain.

I do remember that this may have been information already on the site and I have tried a number of searches using different words and names but have not been able to find anything.

If someone could either send me a link to the thread that has this or provide me with the details I would be very grateful .

I recently acquired an all original Technics SL-6 at a bargain price. It performs well but not flawlessly, and a quick check of the electrolytics suggests their replacement might be a good idea. Considering those caps are now pushing 40 years old (the plastic cover has a 1983 date code), it's probable that they're now at the ends of their operational lives.

Ordinarily this would be a piece of cake, but there are two 47 uF 16 V non-polar electrolytic caps across the stator coils as shown in the attached files. There's no exact replacement available at the usual suspects (Mouser, Digi-Key, etc.), so as I see it, I'm faced with executing the least worst of several unsavory options. They are (listed in no particular order):

1. Do nothing. Pros: Cheap, Easy Lazy; Readily available (as laziness tends to be). Cons: Failure in the near future likely; Subsequent destruction of motor driver IC likely (used AN6636 ICs are difficult to source at best).
2. Replace each with two 100 uF @ 16 V polar electrolytics bodged "+ to +" or "- to -". Pros: Cheap; Easy to source; Likely to fit. Cons: Ugly; Lots of conflicting advice regarding advisability and long-term reliability.
3. Replace each with one 47 uF @ 50 V film. Pros: Readily available; Permanent fix. Cons: Minimum voltage of 50 V is 3X over spec; Off board mounting required (no space); Relatively expensive; Mechanically less robust.
4. Replace each with one 47 uF @ 16 V dipped ceramic. Pros: Cheap; Easy; Likely to fit well. Cons: Possible issues regarding differences in ESR between the types; Lots of conflicting advice regarding advisability of the practice.
5. Replace each with one 47 uF @ 16 V bipolar/nonpolar Electrolytic (Surface Mount). Pros: Cheap; Readily available; Electronically mirrors existing installation. Cons: Ugly; Will need to bodge wires to solder pads; Mechanically less robust.
6. Replace each with one 47 uF @ 100 V bipolar/nonpolar Electrolytic (crossover type). Pros: Cheap; Readily available; More or less electronically mirrors existing installation. Cons: Off board mounting required (no space); Mechanically less robust; Lifetime and temperature rating unknown.

So what I'd like to know is if any of you have faced a similar circumstance or had any wisdom you could share on the subject. What did you do? How did it work out? And are there other options I might have overlooked? Enquiring minds want to know!

BTW, I understand there are some who take the "if it ain't broke, don't fix it" approach, and I respect that. But that's another topic for another thread.

Thanks!

*****SOLD*****
This is a I2S to simultaneous mode TDA1541 dac board designed by Miro. I have built two sets with two TDA1541 chips that i bought.

The 14 decoupling caps for the TDA1541 chip are CDE 0.1uf orange drops. Decoupling caps for the psu are Wima mks, and electrolytics are mainly Elna Silmic II. Resistors used consist of TAMA electric , Vishay and the IV resistors is non-inductive, non-magnetic, copper leaded Nikkohm. Logic chips are decoupled with high quality Kemet SMD x7r capacitors. The electrolytic caps may have some minor burn marks on the plastic sleeves due to my own carelessness during various desoldering to test different caps for sound. But i assure you that they are really minor.

This dac is designed by Miro and more info can be found here :
https://www.diyaudio.com/community/...s-input-nos-r-2r.354078/page-268#post-7159210

Miro also designed the PSU for this dac (not included in this sale):
https://www.diyaudio.com/community/...s-input-nos-r-2r.354078/page-268#post-7159234
Please study the power supply requirement carefully if you intend to use your own psu.

Important things to note :
1. If you intend to have no capacitor at the output, it is advisable to have a dc protection board as explained in the post:
https://www.diyaudio.com/community/...s-input-nos-r-2r.354078/page-285#post-7187720

2. Since i do not have the intention to add a DC protection board, i simply add output caps at the output and i did not further explore the dc offset trimming. But please be aware that DC will be present in the absence of the input signal as mentioned in the thread.
Please follow the instructions by Miro on the trimming of the offsets. You will need to explore this on your own, with your i2s source connected.

3. The only item not provided on this board is the two single Op amp for IV. The rest of the components are completely populated, including the new TDA1541A chip, which is only used for the testing of this DAC.

Of course, the board has been tested and playing well. Price for the board is 185USD, including shipping worldwide registered and paypal fees absorbed by me. And as usual i will buy coffee for Miro.

Hello,

I am trying to build my first tube preamp prototype based on RCA 12AU7 line amplifier drawing in the Tube Receiving manual.

I am trying to figure out how to handle the grounding for the HV/LV linear regulator supplied 12AU7 preamp. Anyone know best practice? Are the grounds referenced to Chassis earth ground or am I to keep them isolated?

Hi everyone,

I'm new to speaker design and I just started learning some theory and trying to design a set of bass-reflex speakers. However, I stumbled upon some information about transmission lines and now I have some questions that I can't really find answers to online.
First and most important question I have: I don't really understand where ports end and transmission lines begin. I've prepared a drawing with ports of different lengths and shapes (in the attachment). Can you tell me at which point on my picture the port becomes a transmission line?
Second question: if I decide that my port is so long that it qualifies as a transmission line does this mean that I have to stuff it with damping material?
Final question: Why do all the transmission line designs that I see use a full-range driver? I really haven't seen many tweeters on those designs.
Thanks in advance!

For sale: Philips OM931 hybrid power amplifier module as sold in the late 70s and begin 80s. High specs and good sound. In total 3; 1 is new and unused, the other 2 are taken from an working amplifier as used by me (these sare ideal for a repair job or for some amplifier project). Price is 20 euros for the 3. Payement by PayPal or IBAN/BIC.

Hello there.

Are someone here using icepower 500a? I have 1 unit and its break, blown up something like thst. The main issue is the thick resistor LTO 30 5ohms the t220 package resistor. The problem is the thick resistor blown. I replace wirewound resistor 50w 5omhs. And Its working great sound i think its back to normal ( i wish 🙂 ) but after 20 to 30mins the thick resistor is too hot you can cook egg on the top of it 🙂 i try to search in electronics store here in PH , but sadly no available 🙁 ..... is there anyone here replace or bypass this resistor? Thank you

Adcom 5300 a match for Spendor SP100 speakers and Audio Research SP9 Mark III preamplifier?

I found a box of 50 of them for near nothing and they have not been opened. I've never heard of them used in audio tube gear.

What do you guys think?

Attached is the schematics and gerber files for anyone who wants to build this.

Rectifier bridge heatsink - HSS08-B18-CP
Heat sink clip for H SS08-B18-CP - HSC-06
Heatsinks for LM338 - FA-T220-64E

Any suggestions on layout improvements or schematics are welcome and appreciated!

I’m having a hard time finding a in-line fuse holder for 4/0 gauge wire .

If I make a fuse holder myself what should I use to the blocks brass,copper,aluminum ?

Since the fuse holder will be under the hood I don’t want it to corrode and give me issue down the road

Hello dear people and dear usual suspects. . . . . ,

does anyone here on the forum have any idea for which Fb the Pensil 12. 2p or the Triton TML
and the Classic GR Mar-Ken12 ov8 have been constructed???

Merry Christmas to all global DIY people, dear crossover free disputants and a good Fullrange 2023

Regards Stefan

Aleph J builder from Wisconsin, USA

Hi all,

First post to the group. I’ve loved reading through so many posts, here and in the Planet10 speaker forums.

A friend turned me onto the Pass designs and I’ve been doing a ton of research and decided that I’ll build an Aleph J. The rave reviews of it make it irresistible. So I ordered a board set and the semis from the DIY store. As I peruse the BoM on this, there are several options for devices. Are they ordered by preference, class, or any other criteria? Or no particular order?

My current stable includes a pair of Klipsch Heresy IIs, JBL L-20Ts, Technics SE-A70 Class A-ish (so it says on the label) amp and SU-A80 preamp, a Denon DP-47F turntable, and a couple of Proton cassette decks, all of which I bought while stationed in Japan in the 80s on the USS Midway . I never have been able to keep a CD transport alive for some reason! I must admit that I love my “vintage” equipment (tough to hear myself say when I remember buying them new) and the collection sounds great in my own ears. But I don’t know what I don’t know. I recently bought a Schiit Modi DAC for streaming to get a feel for what better digital is supposed to act like. It’s a starter DAC before moving up the food chain. Looking forward to seeing what true high-end audio sounds like in my own house. I did work in a hifi shop in Memphis for a while so have experienced higher end solid state and tube amps along with similar speakers from the likes of Totem, Energy, and others. So ready to step up my game.

I was an avionics tech in the Navy, working on F/A-18s during the Gulf War and taught discreet electronics, digital, and radar as well. So I know my way around schematics and soldering irons. This is going to be great fun!

~Chris

NEED 2, Thanks

I was asked about power resistor inductance and whether it's an issue in spaker crossovers or not. I ran the MLSSA through its paces on some items in my parts box in the past, I think the attached tells the tale.

Thought I'd share it here.

Dave

I am attempting to use a Shure Beta 56A to mic a sousaphone for live performance. Because the performer will be moving around the stage quite a bit, I am attempting to design a wireless transmitter rig that can mount to the bell. So far, I have used a GoPro mount attached to the bell with threading adapters to allow the microphone to sit comfortably at the sound source without shifting or excess body noise. See photo below for reference



Samson makes a wireless transmitter unit that is specifically designed to mount on horn bells. Because this is the ideal form factor, I want to connect the Shure Beta 56A to the Samson ATX transmitter. See picture below for setup.



The main problem with this approach is that the mic's rated output impedance is 150 Ohms (290 Ohms actual) whereas the transmitter's input impedance is 3k Ohms. For reference, the transmitter has an input gain range of 20 dB. The output from the mic is standard XLR and the input on the transmitter is mini XLR.

Is there any battery powered mic preamp that would work in this setup to change the mic level output to the line level input needed by the transmitter? As long as it has small form factor, there are plenty of places to tuck such a device. Am I totally barking up the wrong tree? Is there another way to approach this entirely? Thanks in advance for any advice!