I'm curious if there is a measurable/audible difference besides the 'easy wire secondary' in the A series OPTs? Anyone with any experience or opinions (on this subject)?

Do you guys equalize your car audio systems to match an idealized frequency response graph?

Do you adjust it for driving speed and resulting road noise?

I saw this graph and wondered how car audio DIYers approach equalization in practical terms.

Usually we calculate junction temperature from collector dissipation (easy to measure) and Rth from datasheets. Once we have working prototype we can measure case temperature and infer the junction temperature.

Can we instead calculate Tj from difference in Vbe measured immediately after a cold start (when Tj is supposedly equal to the ambient temperature) and again when the thermal equilibrium is achieved?

This is the formula:

Tj = Tamb + (Vbe1 – Vbe2) / tc

Tj - operating junction temperature
Tamb – ambient temperature
Vbe1 – base emitter voltage measured immediately after a cold start
Vbe2 – base emitter voltage when operating temperature is reached
tc – temperature coefficient, ~ 2mV/C for silicon BJT

I suppose measuring the Vbe1 is the most challenging part. Allowed time to make the first measurement depends on the physical size of the device. For small devices thermal time constant might be too low for reliable measurement with common multimeter.

BTW the same method could be considered also for MOSFET devices.

Your comments are welcome.

Hi
I have a crossover to repair that requries a 3.3mH inductor. Can I put a 3.0mH plus a 0.3mH in series to make the 3.3mH total?


If yes, do they need to be arranged in any specific orientation to each other?


Can I mix an iron core and air core together?


Thanks.

I have Micro-Cap 9. It has a 6DJ8 tube in it. I'd like to change the parameters to a different tube, which isn't in it's database (6H30).

Those are the parameters for 6DJ8:

+PARAMS: LIP= 1.5 LIF= 10 RAF= 0.09 RAS= 0.2 CDO= 0
+ RAP= 0 ERP= 1.35
+ MU0= 33 MUR= 0.02 EMC= 0.0000795
+ GCO=-0.2 GCF= 0
+ CGA=1.40E-12 CGK=3.30E-12 CAK=1.80E-12

Out of those, I get what MU0, CGA, CGK and CAK are.
I have no clue what the other parameters mean.

Does anyone here know?

I have a PHD2 I bought new from a guy around a year ago. It was great and had way more power than I needed. One day at work the guys and I were bored and we wanted to smoke a speaker for fun. (yeah, I know STUPID ME) Anyways, we screwed this 6" woofer to my back deck, just to see how much bass it would produce before we smoked it. Well, as soon as the speaker burned, the coil must have shorted to the frame and then to ground through the back dash. The amp shut the entire car down it was drawing so much current. I had to go under the hood and disconnect its main fuse.
After sending it to Earthquake in Cali., and spending much dinero to repair it (I had attempted to repair it by replacing every power supply and output transistor with the original part numbers but it still wouldn't come on) I got it back almost two months later. They somehow kept forgetting to send it back to me. Now when I turn the volume up high enough to pound the 12" mtx 7500's it seems to automatically turn the volume down a little even though the car's voltage isn't dropping much and the subs are aok. It never did this before I fried it on the cheezy 6" woofer. The only thing I noticed different on the amp board is a diode soldered across two of the legs of the power supply pwm IC, or at least that's what it looks like. Of course the IC has the part number ground off so I couldn't change it when I attempted to repair it myself. (that was the only part they changed, besides replacing the ones I changed with the SAME part number transistors🙄 )
-Does anyone know why they soldered that diode across the top of the pwm ic? Is it some sort of power limiter to protect the amp from me running too low of a load?
-If so, can I just remove it? I never run lower than 2 ohms nominal load, I just made the mistake of having the amp ground to the car's body ground one time. I tried getting ahold of the techs at earthquake to ask about the IC and the diode but couldn't.
-The amp never did this before they repaired it and I want it back to normal. I told them about it and they said "It tested aok and made full power" I was like, yeah, whatever. Thanks🙄

A new company with a strong reputation in professional music has acquired the Hafler and Dynaco brands and intellectual property. I will not say who as that may be considered advertising.

Our question is:

For an ST-70 amplifier would the preference be for:

1. An amplifier as faithful to the original ST-70 but incorporating the improvements of that have been done to it by the audio community but using no New Old Stock parts. Sorry, no 7199 input. But following the original Pentode-Triode input circuit with feedback.

2. The best possible amplifier that will still use the EL34 output but where the input/driver uses new topologies for what we feel will be better sound quality. We have spoken with people who knew David Hafler and we would basically do what he would have done today if he were around. However, the signal path will still be through tubes.

Either of these made with all new parts will have an MSRP a little north of US$1200

We ask because there are so many old and rebuilt ST-70 amplifiers out there, that some here have felt that a person who wants the original 1950s sound quality will just buy one of the original or reproductions for a lower price. That a person buying a new unit wants something that is competitive with a current well rated tube amplifier.

Note that the lead engineer on this project received their basic electronics education in the 1960s on tubes and has been involved with the audiophile community for decades. This is not just some rebadging exercise.

Regardless, as a long time DIYer, I would appreciate the input of the DIY community on the approach to take. And your comments do not need to be limited to the ones I have given. For your suggestions, all I ask is that you only recommend tubes that are still in production.

Since the arrival of Corona Ive been bored and since planning my next DIY project for summer vacation, but due to uncertain financial future I scrapped my original plans for something cheaper: a small bookshelf based on some simple car-audio kits. It was fun to assemble this simple design and now I have something for the winter fireplace (as expected it sounds horrible). All jokes aside I will probably buy better drivers as I'm very happy with the wood work and definitely learned a lot in the process as preparation for next bigger projects.

Size outer: 30*20*18 cm

Cost:
Wood: 2pc of 300x2100x18mm pine = aprox 40 eur
Car audio kit 6,5" Biltema: aprox 55 eur

Glue and paint I had from before.

Looking for JA3882, original, in good condition. Need one woofer.

thanks,
Herman

I need to take an audio signal from the output of the terminals of a valve amplifier, to send to the input of a Bheringher power amplifier.
I currently have that configuration (I have no other possibility) with a DaytonSPA250 board amplifier that has high and low level inputs. But I don't have the circuit of it.

I know that it is feasible then, (I understand that I should build a resistive voltage divider) but I have my doubts if it applies exactly the same to a valve amplifier or there would be some specific inconvenience.
Could someone guide me about it? Any link? Thanks in advance !

HI Folks
I'm new here... if anyone would like to check out who I am - please visit my site Edward Powell - I'm a musician and instrument maker

I have an excellent old MARANTZ cassette recorder that needs some work in order to get it functioning properly --- I love cassettes and that's all I listen to in my 1981 VW bus...

Please if anyone has some experience with this I really could use some help - THANKS

Edward

So I got a pair of these last week and I'm wondering what to expect from them. Anyone have these? Comments would be highly appreciated since I won't be running them until the late fall due to the extra heat they make.

These have fantastic specs but I was told elsewhere they achieve those by using lots of feedback and some other tricks that make them sound bland. They came with a pair of QUAD ESL-57's which I was hoping would be a match made in heaven.

I wrote this white paper to encourage people to build a subwoofer in a closed box.

For sale whole package of tubes that I never use and I dont need this anymore.
2 x Sy227 Sylvania mesh plate matched pair mesured 1000 and 1050 ,buyed from tube depot Usa
2 x 6h30pi Electroharmonix matched pair New buyed by Hifi Collective UK
2 x 5u3s Russian rectifier grey plate Nos
1 x Az 11 Valvo mesh plate,glued base,Nos
1 x Ez81 Rft Germany rectifier Nos
For all tubes the price is 120euro plus shipping 8,90 euro inside EU,excludit UK.For all other countrys pkese ask for shipping cost.Payment thru paypal.For info or offer plese contact me.

I'm working on a faulty Gallien-Krueger '200Watt' bass amp that has an ICEPower 50ASX2 modular amp fitted.

PSU +- 25V Supplies OK, No audio output due to pin 1 (enable) of connector P102 being LOW and disabling amplifier, (should be +5V when NO connection to it). Nothing appears physically damaged on the board. (Pins 2 & 3 protection outputs of P102 are OK at +5V). Looks like it is fed from IC400.

Very occasionally when switching off the audio input signal will 'burst through' briefly, so I dont think its a 'big problem'.....

Anyone encountered this ...or solved it?!

THANKS

Hi everyone, this is my first time here.

I wish to ask if somebody has the Tannoy Sandringham crossover schema.

I'm trying to do them by myself starting from Tannoy 2062 loudspeakers, but I didn't really find any information about crossover.

Thank you in advance for any help about this, really appreciated!

HI all,

So Im currently in the process of designing a subwoofer using 2x DSA215 PR's and 1x SB23MFCL-4 although almost finished I had one last question:

Is the maximum power in WinISD only looking at Xmax without any filter?
Since due to exceeding Xmax I will have to use a High Pass filter at 26 Hz but turning this on and off does not reflect in a change of the maximum power graph. With the filter Im way below Xmax (both for the PRs as the driver) when the signal input is on 150 Watt.

I personally always push the supply near the limit of the 5532/34 op-amp which are maximum rating to +/- 44V to around +/- 42V which gives me a higher headroom of 3V peak compared to the standard +/-36V seen in so many design. I used this technique in my precision preamp of Douglas Self and everywhere possible when I use 5532/34 op-amp in audio field.🙂

Here is info on the tweeter I made. It has 4 5/16 inch long magnetic part and ribbon is 3/8 inch wide. .03 ohms for pleated ribbon. This is quite a project to make the parts. A lot of cutting, filing, drilling, and tapping. The 1/2 X 1/2 X 2 inch magnets are the N52 which is the strongest I could find. Since it is high current, the wires are large and soldered into deep holes in the brass part. Top part is thick so will press on ribbon evenly. One end is insulated from steel part. When done and has a good ribbon, will have an aluminum screen cover. So far testing things, I have destroyed 3 ribbons. One to measure the resistance, one when I hooked it to transformer at full volume, that was ear splitting! One jusr wasn't right, so rubbed. Hard to get one straight. I don't know if kitchen foil is really any good for this. Seems stuff a little tempered would work better.

Hello there,
I have an ICEPower 50ASX2 in a Fender bass amp that gave problems.
After a very close look I found two burned smd parts, FE100 and FE101.
I assume they are coils or the like.
After these "coils" we find the connector P103 (+/- 24V DC).
The fuses are ok.
I first tried the other pcb's with an external supply connected to the cable going into this P103 connector.
All worked as intended and no excess current is drawn.
So I replaced the FE100 and FE101 with a piece of wire and reconnected everything.
The amp works flawless now.
But still I want to replace FE100 and FE101 with the correct parts.

Here my question:
Is there anybody who can tell me what the correct parts could be?

ps:
IcePower and Fender can't tell me what parts are used?!
Schematic of the Ice module? No way!!!
I allready asked for it.

Hello

I am building the upgrade DC power supply for DAC in separate chassis. It consist of 2 set of power supply, one for digital and other for analog. they have separate ground.

The problem I concern is, how do I connect the chassis ground at the PSU chassis to avoid ground loop? I thing the ground of each set of power supply will be connected some where in the DAC, and if I connect the ground of each power supply together at the PSU chassis, may it cause the ground loop?

or I just put only one set of digital ground or analog ground to PSU chassis.
Which is the best way to go?

Thank you
Tanwa

NOW SOLD

I have for sale a pair of Fusion passive loudspeakers (level 1 kit) that I made 18 months ago. Price £1500. They are finished with Birds Eye Maple veneer and satin black paint on the front baffle. Here is a link to the TG website for these speakers:

Fusion

Lovely sound with deep bass with a lovely tone. I've attached frequency response graphs that I measured with REW and a calibrated mic, they are unfiltered. I offer them so you can see that they respond as expected; the low frequencies are probably affected by the room to some degree but the overall response is good. I guess all diy'ers know that the sound quality will be comparable to commercial speakers costing much, much, more. At the Ascot hifi show last November I listened to £20k speakers that I didn't think were as good, but that's just my opinion!

Collection only.

Auditions are fine with me if you are near Sandy, Beds.

So I have a Hifonics BRZ 1700 that has been repaired.

When I look at a sine wave on the output and I gently twist the output inductor it seems to shift 180 degrees out of phase. When i let go it pops back.

Took inductor off the board but cannot find a short. Re-installed and same thing.

Any ideas?

Amp is mono with 2 rca inputs. When I hook up one rca i have a distorted ouput. Hook up both inputs and the distortion goes away.

2 2068 IC's on the initial input stage, seem to be ok.

Hi everyone. I got a pair of home built speakers with vintage speaker drivers inside. At first they didn't sound so good but i made them open back and now they sound absolutely amazing. These are my favorite speakers to listen to music. They have so rich and clean sound.
In the boxes are DEW magnetfabrik Dortmund 6x9 speakers but they just lack high frequency. So my question is how do i go about adding a tweeter to vintage speaker. And what about a crossover, i don't want to spend a lot of money on the tweeters and crossover because i got speakers for next to nothing. I can provide videos and pictures for driver identification if needed.

hi all
I have this boss PF1800 class AB amplifier. Found no damage on outputs or power supply but just resistors across speaker terminals burnt. I think they are 4.7ohms. I have 5.6ohms in stock. Can I use this instead and what will be the reason they got burn in the first place. The 104j caps are good found no short. Is there anything that I need to focus on?

Hi I'm building an audio mux with volume control using a couple of digital potentiometers.

The digi-pots require the signal through its pot connections to be between GND and VCC which is 5v so I decided I will raise the audio input ground to 2.5V with an op amp or maybe an LM317 regulator.

I will connect the digi-pot as a regular potentiometer, the input at one end, the ground at the other and take the output between the wiper and ground only that the input and output signal ground to this digi-pot will be the 2.5V reference line. The audio signal is AC coupled and dc-shifted to the same 2.5V line.


SWITCHING:
I have several options to try to switch the input audio,
1) use a whole 4066 for each audio channel, that is one 4066 for the left channel & another for the right, that's for each input channel. Each channel is a "T", two switches in series, and the connection between them is connected through another switch to the 2.5V line. Adv: When I disconnect this channel, it looks like 100M ohm in series with another 100M input to output and 125 ohms to 2.5V between them. Disadv. takes lots of board space (not a big problem), cost doesn't matter.

2) use 4052 for all 4 stereo inputs, Adv. small board space but I need HELP here, I want to achieve the same effect of connecting the input to be disconnected with the reference line instead, if VCC is at 5v and VSS at 0, can I connect the VEE to the 2.5V or does it have to be below VSS?

3) use 4053 and switch the audio input with its reference; L, R & Gnd but still may need to connect VEE to 2.5V

FRD2SPICE is a little tool that generates a spice model from frd / zma files that I wrote a couple of years a ago. (It generates a .SUBCKT netlist.)

I thought I'd share it here in the hope that might be useful to others as well ho like to do xover simulation in ltspice. (Or any spice variant that supports frequency tables really.)

The generated model is implemented using frequency tables and voltage / current sources. It's intended to be used for .ac analysis (frequency response).

The tool will ask for 5 files:
Spice file: name of the .lib file to be generated.
zma file: Impedance data.
3 frd files: Typically one on axis + two off axis files (the last two are optional. Just click cancel if you don't want to use off axis data.)

Files included:
FRD2SPICE.exe: The tool it self. An enormous 10Kb file... You may have to run it in compatibility mode on windows 8.1/10 because i originally wrote it for windows 7 32bit.

SpkrTbl.asy: Ltspice speaker symbol, it takes two parameters: driver name + DeltaX (acoustic centrer compensation in meters, usually = 0)

Dayton2way.asc: A simple example project to get you started.
Some .frd & .zma files: used in the above project.

Enjoy!





View attachment FRD2SPICE.zip

easy question, is there a standard iso fitting bearing/spindle turntable?
Like H7/f7, G7/h6, J8/h7?
Standard sintered bronze bearings are all H7 fitting and I think that's to big...

thanks

It’s a Rockford Fosgate punch 150 the problem is wont power on I hear a clicking sound in the transformer and the led has dim blink going on. I’ve already replaced the D44 power supply transistors and LM339 with a new one no luck.

I had the chance to measure above power supply.

First of all, I measured the rail voltages with a true RMS meter. They came out as +/- 63.1 V. I then loaded the negative rail with a 66 R power resistor. Voltage dropped to -62.3 V (forgot to measure the positive rail) within about 10 s. Loading with 33 R caused a drop to 61.7 V, but this was within about 1 s.

For comparison, the Hypex TR400 toroidal with 2x 10000 µF dropped from 61.7 V to 57.0 V with 66 R and to 54.05 with 33 R.


Ripple data to follow...

Hi, I am using the YEDS-18 test CD, standard for compact disc player alignment.
Signals like a 1000hz sine or 100hz sine at full scale heavily clip
on the Buffalo II. So will music.

Now one could say that overshoots in 0dB test signals
were unknown back then.
But any other player plays the YEDS-18 fine.

And, most important:

The clipping is not always there.

Switching off the Buffalo off and back on sometimes helps.

Then the test signal will me played fine.

So something erratic must happen,
when the Buffalo II/ES9018 initialises during powering up.

Input is tranformer-isolated SPDIF and the clipping is
definately in the digital realm.

Best,
Salar

A continuation of my previous thread, Rolecor RTA-650 receiver - revisited. But will bypass those details. I am failing to solve a problem or discoveed another, and I am hoping for additional, insightful advice.

Where I am at now is BD139 & BD140 driver transistors are installed. They are in place of KSA2690 & KSA1220 which themselves replaced original 2SC497 & 2SA497 as one of the latter was faulty.

Newly received output devices are in place as well, MJ21194.

After each transistor installation, I powered the receiver up with a DBT and each time, the bulb settled to a dull glow. Once all were installed, I tried listening to the receiver but still have a dead channel - the right one.

Before installing the BD139 & BD140 pairs, I was getting 53 Volts at each leg of the transistors preceeding them. And I am still getting that voltage now.

Looking to an "upstream" component, I checked a TO18 transistor in the affected channel and it reads as bad. It's counterpart in the other channel does not display the same fault.

The number is C727 - presumably 2SC727.

So far, my searching has not hit on any situation involving that transistor. I did find a data sheet (attached) but when entering specs on Digi Key's part finder, which is just guessing on my part, no results resemble what I think I'm looking for.

Since a C727 is NPN, I don't suppose BD139's that I ordered extras of would do?

I have a pair of 82 rectifiers that take 2.5V for the filaments. My OPT filament AC supply is 5V. So, I took a pair of matched resistors and dropped the 5V down to 2.5V (see schematic attached). The pair of resistors was done on both legs of the AC supply. Without the tube in the socket, this tested OK at the socket pins. 2.5V dead on. Then, I insert the 82 rectifier into the socket and there is no heater voltage. 0.0V measured again at the socket pins. the 82 rectifier does not heat up. I tried this on 2 tubes, but NOS, and neither is heating up. Both tubes have good continuity between the filament pins. Note, only the filament voltage is being applied. No B+, as the rectifiers need to warm up (mercury) prior to B+.

Thoughts?

I have a set of brand new in box SB drivers meant for the Jeff Bagby's Kairos speaker and the woofer module to let go.

USDXXX for the set. These are better suited to be sold in asia as they are in Singapore.

PM me for shipping.

Satori TW29R x2
Satori MW16P-8 x2
SB9NRX75-6 x2

Hi all,
I have 2 TB w4-1320 laying around and I want to build 2 floor standing speakers for my tv.
I have 97cm in height, (make it 40 inches for the US folks), and I'd like to try the BIB.
I downloaded the sheets from Godzilla(thanks man!) And I need a 2.25m line, with an output surface of 310cm2, with the speaker placed at 50cm from the start of the line.
Now, don't have enough height for the standard bib.
So I need to fold twice, but I also want the speaker to be as high as possible, ideally at the top of the cabinet.
So I came up with this solution in the picture.

15971313270311342493500824927051 — ImgBB


As an idea, is it correct?
Any drawbacks of I maintain the original shape of the "tall" bib?
Thanks in advance!

I have been watching the forum for years and recently unloaded all of my audio equipment in hopes of doing something more interesting in the DIY space.
I am most interested to build the following first:

1. Near field monitors from a single full-range driver for my computer, est. distance from my ear would be 30" and positioned on top of my monitor. I have no desk space for them so they will be mounted pointed slightly downward towards me.
2. Limited volumes due to it being for use during my workday and in a small room, about 9x9'. Thus, I want to have the 'loudness' effect at low volumes whereby bass is present without increasing the power input.
3. Thus far focusing the efforts on using a MarkAudio 7ms.
4. The box cannot be any bigger than about 5L due to the mounting requirements about the monitor which is about 12(w)x4(h)x8-10"(d). I am expecting them to be longer horizontally and rectangular.

I have run through some simulations but have limited experience. Thus far they seem to be telling me its going to be hard to get a low bass frequency in that size. The best seems to work out with a tune around 70-80hz.

I have been considering a transmission line design and would be very interesting to hear the difference they may make vs a standard port.

I would appreciate any opinions on the possibilities of the objectives and perhaps some help on design options that fit or someone to tell me that there is a better driver fit or that I am out of my mind, at which point I will want to try even harder to be creative with this need.

Picked these up somewhere along the way and haven't used them yet so it's time to let them back in the wild.
When I got them I drilled the 1" side to accommodate the 2 hole Altec bolt pattern. This was professionally done on a Bridgeport mill by a tool maker (Me).

Flange Dia on the 1" side is 3.9" with the Altec 2 hole bolt pattern and another bolt pattern with 3X 1/4" holes drilled on a 2-1/4" bolt circle.

Flange Dia. on the 2" side is 4.7" with 4X tapped holes on a 4" bolt circle. Holes are tapped either 1/4" fine thread or 6mm. To lazy to check at the moment but can do if it's important. There is a lot of room to add your own bolt pattern if your so inclined.

Overall length is 3" so the expansion rate (cone angle) is not as abrupt as most adapters I've seen. Heavy cast aluminum construction but there is no indication of the manufacture on them. Probably had stickers at one point.

Asking 50 bucks plus shipping from NJ. Shipping to US only. Pictures upon request.

BillWojo

I have a 1,200w/38,000lm sylvania bulb, now I need help building a nice projector around it. Here are the details to work with:

1. I'm in Africa, with a few box stores, but no RadioShack-type outlets. I can order stuff from ebay...and I can have small items (fresnels/front lens/etc) FedEx'd in time for the project to be completed by its deadline (Sept 14th). I have $1,000 to work with.

2. I also have a Chuwi Hi9 tablet with 2560x1600 screen. Could this be used with a set of fresnels? Or would it be best to get a flat panel lcd monitor from the local big box store? (Note: I'm in Africa, and there aren't RadioShack type stores.)

3. Size is not a worry, a long as the finished product can fit on or in a small car. Also, the project will only last a few days, at most. In fact, this might only be used for less than an hour. But it needs to be the BEST it can be for that hour. 🙂

4. I'll be projecting onto a med/large building, maybe 200'x200'.

Finally, I can probably find an old slide projector and/or overhead projector for lenses and fresnels . . . but if something ordered from eBay can outperform those, great. I'm looking to make the projection sharp and colorful, and if some items need to be sent from the states, ok.

I've already checked into used projectors. Some are great, like the stackable NEC stuff..but anything 10,000lm+ just weighs too much (50lbs-ish) and the shipping would probably break the budget. If I'm wrong, I would gladly have a 10,000lm+ projector sent here, and avoid the DIY'ing.

Look forward to any helpful tips! Innovative ideas very welcome!!

-jc

I'm doing a repair on my Forte 4a, would appreciate any schematic that anyone out there can provide.

Hello everyone!

I currently own a Sanyo DCX6000K with a problem in the main power amplifier section. This stereo receiver has two amplifiers (one per channel), one of which is giving random high volume noise spikes on the correspondent speaker while the other channel works perfectly.
Some tests/repairs I've done:
- This happens even without any volume on the receiver.
- I've tested the faulty amplifier outside the receiver powered with a dual power supply (with the input grounded): same thing happens on the speaker.
- I've replaced all caps with new ones.
- I've already tuned the amplifier bias with the help of the same dual power supply current measurement. Any time a noise spike occurs there is a current spike as well (which is obvious), and the current bias stabilizes when no noise occurs.
- I've replaced the output transistors 2SA764 and 2SC1444 with original ones (found from eBay).

I'm looking forward to replace the remaining transistors of the board, but I need advice on replacements for them:
- 2SA733 PNP
- 2SC875 NPN
- 2SC1175 NPN
- 2SA659 PNP
- 2SA532 PNP

The schematics may be found after login in the HiFi Engine site, for example. The faulty board reference shown on the schematics is 131-0-4001-33001.

Any help is welcomed!

João

Hi fellow builders

I'm after nice, practicable, affordable connectors for my amp- and preamp-projects... that is, signal-connections as in "wire-board" as well as "board-board".
There are plenty at the usual suppliers, but I'm a bit lost because of the many variables to look for, and a lack of relevant experience?

obviously important are
- connection-quality
- signal-integrity
- ease of use
- price & availability

of course, if there was something that is looking good it'd be all the better.

thank you!
david

I am repairing a ground zero 10000spl.
It was initially using IRFP360LC, but I decided to use FDA24N40F.
Usual problems, output mosfet in short (only in one of the 4 stages) broken driver board and perfect power supply.
I did the usual tests:
1) perfectly fixed the driver board
2) checked all gate (33r) and pulldown (100k) resistors, all perfect, but for safety I changed them.
3) checked the 4 resistors of VB (4,7r) all perfect, then I left them in their place.
4) to the eye there do not seem to be short circuits or shorted turns in any of the 4 inductors.
5) I detect all the low sides and with the help of an auxiliary 12v source (small battery) I also detect all the high sides, so everything is fantastic.
6) after fixing everything, I mounted only 1 IRFP360LC for each side (of each stage) using different production mosfets (but it was only a test) and the amplifier immediately started regularly showing a correct switching frequency on all four the stages, only that some mosfets warmed slightly (which could be normal, since I only used one per side and in addition, the mosfets were not all identical).
7) I remove the test IRFP360LC and install 1 brand new FDA24N40F per side (for each stage), I turn on the amplifier, but unfortunately I see that the amplifier does not start, that is, the frequency of RAIL TO RAIL, appears and disappears intermittently , as if it started and stopped all the time.
8) I remove the FDA24N40F to do some tests, but nothing has changed, everything is like in point 5, only now, I have reinstalled FDA24N40F but this time some output mosfets are shorted, so now I am forced to rework the driver board, what a great waste of time.
Anyone have any advice for me?

Hi

Just bought a second hand RX-V3800, that is working OK, just can not change any settings, because the GUI is not showing, on any of the Monitor Out sockets, does anyone know how to solve that, I am using the Receiver in 8 ch, multiple input mode, in an active set up, like I said that works very good, just curious why no GUI,

Cheers, Tom.

Finishing up my parts list and cutout diagram for a 6 channel Hypex build. Need thoughts/input on the following:


1) To keep things simple, I was thinking of using an IEC socket with a built-in On/Off switch and Fuse. I found one on Parts Express but it says it can only handle a 6A @ 250v fuse. I will be on 110v and wanted to plan on the combined continuous rating of the Hypex's which would be 900w. So I thought a 10A fuse would be best. Any other recommendations to look at? Or is my math wrong and this socket would be fine?


2) What is the easiest way to add an LED to the Front Panel for when power is on? I will be using a 12V trigger assembly so my pre/pro will turn the amp on/off. I would assume I could splice 12v power off the trigger?



Thanks!

link to product page of this driver: BLAUPUNKT: Subwoofers

There's a place that sells these for under $30. I'm thinking of buying 8 of these for an infinite baffle build. To me it seems like this would be the best sound-for-the-buck build you've ever seen. Please disprove me because I can not hold off from buying these now.

Are the specs on this sub good? Are the specs good for an infinite baffle build?

Can a 4 ohm resistor be used to increase a 4 ohm subwoofer to make it 8 ohms? I heard that it would lead to boominess. Can someone help?

Hi All,
I've been itching to build a Nelson Pass amp for a couple of years now, but I'm hesitant to pull the trigger on any particular kit since I'm new to this and have limited time and budget to try them all (though am not all that new to electronics). I also may need a reality check to know if any of the current offerings will even meet my needs. I've never heard any of these in person, nor any low watt class A amps. So, not exactly sure what to expect. I'm hoping you could help me pick an amp that'll fit my needs, or maybe even dissuade me if in fact none of them will meet my needs. I just really like the idea of building a world-class type amp with my own hands.

A little background. I currently have a home theater setup with Elac towers (~87db sensitivity, 6-ohm nominal) that I'm looking to pre-out the front channels to a higher fidelity amplifier. My primary music source is through Raspberry Pi -> USB DAC. This setup would be temporary, as I hope to build a dedicated 2-channel system in another room of the house in a couple of years, using the newly built amp and high-sensitivity DIY speakers that I also hope to build in the future. The HT receiver does have an SVS sealed sub, in case that matters.

Music and preferences
My primary listening habits include classic rock (Pink Floyd, Rush, Led Zep, Police, Dire Straits), and electronic/post rock/alternative/indie (Kraftwerk, Foster the People, Mutemath). I sometimes listen to other acoustic stuff like folk and jazz.

Preferred sound signatures: airy, detailed, wide soundstage, clear instrument separation, black backgrounds, great imaging. Somewhat forward and fun without being fatiguing, forward vocals and midrange, with slam and presence. Warmth, but not muddy - just a little bit lush.

I don't listen at extreme loud levels, but maybe a "comfortable" loud that will fill a 17x17 open room with sound - comfortable loud as in too loud to carry on a conversation with someone in the room, but not so loud that it is uncomfortable to sustain for more than a couple of songs. Are the Pass builds the way to go for me? If so, which one would you suggest, given my music choices and listening preferences?

Thanks!
Thad

I am building a preamp and I'm wondering about the benefit of including internal aluminum panels to separate the audio circuits from the power supply and digital circuits.

The preamp will have two toroidal transformers with steel covers, regulated power supplies, and also an OLED display board.

There is only an inch or so (~30mm) of space between the power supply boards and the audio circuitry. Maybe 6 inches (150mm) between the OLED board and audio boards.

Is there any benefit adding aluminum panels in between these circuits. I'd obviously have to fish some wires/cables through/under the panels, but otherwise the spaces could be completely separated.

Thanks.

I hope that this is not too ridiculous of a post. I’m just getting to the stage of thinking I know enough to be dangerous.

I’ve just built an F5 amp and am now starting to upgrade the upstream components. First on the agenda is a Raspberry Pi based streamer with a separate DAC HAT, most likely an Allo Boss. I currently trying to decide how to power this setup. There are obviously a lot of power supplies available, but since I’ve got some time on my hands, I thought I would try to build one.

I’ve gone through a lot of threads regarding DAC power supplies and tried to distill the data / opinions as much as possible. With regards to power supply noise, it seems like “low noise” is good, but “ultra-low noise” may not make much of a difference practically. This seems reasonable given that the DAC has filters to further reduce power supply noise and the RPi creates enough noise internally to overwhelm any from the power supply.

In the thread on the Shanti Power Supply, there was a lot of discussion on load transients and having a significant amount of capacitance at the output to deal with these transients. The prevailing opinion seemed to be that this had an impact on both measurements and perceived audio quality.
Putting that together, I’m thinking about building the attached circuit. The basic design ideas were:

• Single Rectifier into a reasonable capacitor bank (3000uF) to drop ripple somewhat and keep supply voltage above the dropout of the succeeding regulators.
• Separated regulator / filter circuits for RPi and DAC fed by the single unregulated supply.
• 7805 regulator with the datasheet implementation of the high current regulator with overload protection. This should provide more than enough power for the device and the overload protection will limit the inrush current when charging the succeeding capacitor bank.
• A lot of capacitance on the output of the regulator, both for bulk storage and decoupling. The capacitor bank will include one 1F supercapacitor (581-SCMR22G105SRBA0), 2000uF of Electrolytics and 10uF, 1uF, and 0.1uF decoupling caps.

I’ve got a couple of questions before I tackle the build and was hoping to get some input.

• I realize that over 1F of capacitance at the output is crazy, but has it passed crazy and transitioned into stupid? The supercapacitor costs ~$5, so it’s not going to impact cost too much as long as it won’t have any negative effects on power quality.
• Is the balance / amount of electrolytics about right?
• Is there something else that I’m completely missing?

I’ve attached a schematic of my idea. Any input is appreciated.

Hi all, I'm generally a speaker builder so have come over here for some advice. I need to replace the volume pot in my Proton-520 integrated amplifier.

I bought it a while back and it looked as if it had been dropped at some stage as the volume knob had a chunk missing out of it. I tried replacing it with a standard log pot but then realised that the pot has an extra tap (so it has four legs). I'm guessing this is for the loudness button or something. Anyway, the volume is far too sensitive as it is at the moment with a regular three pin pot and the other lead left taped up so I was hoping someone could direct me to a replacement part for the volume pot. Unfortunately I can’t find the original pot so I have no way of determining what the extra leg was connected to at the pot end.

You can see the pot in the bottom right hand corner of the picture. There are two white wires run to it which correspond to each of the channels as the silkscreen on the PCB says x and y next to the pot and also where these wires are connected to the pcb.

I've attached a couple of pics of the amp (not my unit) and the service manual.

Please help me out!

Cheers.

I have a couple of these, which I'll let go for competitive (China seller) ebay pricing. I'm in the US. PM me if interested.

NI now has the free LabVIEW "Community edition" which I assume will work with this product. Unfortunately for me, my only GPIB instrument no longer responds to its GPIB interface, so, no need for the GPIB interface anymore.

I'll give it a couple week, then put them up on ebay. Thought I'd give folks here first dibs, if anyone;s still interested (last time was 2016)

Hi everyone,


I have a bunch of music from cd's stored on a USB flash drive that I want to listen to on my Bosch PB360C Jobsite Stereo. The Bosch has a 3.5mm AUX input jack and can also be paired with a Bluetooth enabled playback device. My question is, what is the simplest way to connect the flash drive to the Bosch so I can access and listen to the music files on the flash drive? What hardware and/or cabling options would work best for this application?


Thanks for any and all suggestions!

hello,
does anyone have pile of 800c parts or an 800c in a pile?
I have an 800c in the UK that is a lovely thing but has been a) bodged and b) dropped. We are working through it but need the speaker selector knob, 3 sliders, but mainly an output transformer... T991-116-1C
I'm in the UK but happy to sort out a way of getting it here from the US...
thanks!
alex

I have to replace 2 different zeners on an amp board and, replacements are hard to find. The originals were: WZ-280 and WZ-197
Found NTE5034A and NTE5029A but even those are hard to find!.
I always get stuff from Digikey Canada but, they have nothing like these in stock.
Any ideas???

I'm building my first preamp and I'm just coming to the output stage. I'm new to this, so I'm trying to work out the best approach. The end goal is to have balanced end-to-end, but currently my power amps are single-ended so I need the flexibility to have both outputs.

Is it better to use a simple XLR>RCA convertor (that connects pin 3 to pin 1), or would it be better to integrate a balanced>SE stage at the end of the preamp that allows for both balanced and SE output? I've seen very conflicting information, but most of that comes when conversion isn't possible (i.e., someone is buying pre-built components)

I'm assuming that I could simply put the balanced output to the XLR connectors then tap into those connections (on a PCB) as the inputs for a conversion stage, maybe something like the Project 87 opamp-based balanced>SE stage.



I'm just wondering if I'm over-engineering this due to my enthusiasm 🙂

I got Samson SR950 they sound fine , no issue with quality but the problem is the output is low from my PC motherboard. How can I make them sound louder? I don't want to spend more then $50-60. I just listen to music and play games I am not into any studio stuff.

I saw some amps but they are tiny portable rechargeable but I will be using headphones on my desk so I can get proper amp with wall adapter. I assume full size amp will be better then those small portable ones and you don't have to recharge them.

I don't know what will be better an Amp or PCIe sound card or DAC/amp combo or something else.

Hello,

First post here so hello to all.

My Marantz CD-63SE was skipping quite a bit, so I bought and have installed a replacement VAM1202. Tested with three CDs all of which would not play well before, and all three played through perfectly. I was very happy.

But - the fourth CD - the player could not detect. Nor a few others. In fact only about 50%.

So, I tried adjusting the pot on the laser assy. Some improvement but still not perfect. Then I tried adjusting the two tiny torx screws as suggested on the CD63-67 thread on here. Again, some improvement, but still only about a 75% success rate. The "old" laser assembly never had this problem, it read any CD I tried, just often skipped during playback.

The seller of the replacement laser suggested "adjusting the servo" but has not explained what that means. Also he says that there is no chance the VAM1202 is faulty, which contradicts what I have read on here that some boards are duff on arrival!

So, can anyone please give me any advice on what to try next?

Many thanks,

Richard

When fixing one of the bass speaker surrounds, as described here, I also had a closer look at the crossovers and the internal wiring - and I was not too happy with what I found. (Shifting from 'repair' to 'modification', I considered it's better to start a new thread.)


A bit of history: I had bought those speakers around 2002 / 2003 from a small dealer who claimed to have modified the original crossovers and had used those speakers for demo in his shop for a while. The price was reasonable, sound was great.

Now, more than 15 years later, they still sounded great. This is true for use with a pair of Quad II (early 1960s), which I used until January this year, and even more now with my newly restored Quad 303 in combination with a Rotel 1570 preamp.

But looking at the internal wiring I could not resist to think: there must be more in store, soundwise!

What I found were 'van den Hul M.C. CS18' halogen free cable. van den Hul website states that these are 0.56 sqmm 7-strand silver coated copper, and they recommend these cables for tweeter use. These cables were used for all internal connections between crossover and speakers.

Looking closer, the silver coating seemed to be corroded where the cables meet the cable shoes.

Next, the crossovers. Just look for yourselves! In my early years, as an apprentice, my boss would have thrown me out of the lab if I had delivered something like this, even as a prototype.

What to do next? I can see a Mundorf capacitor, and an air core inductor, which add to my confidence. I decided to leave the crossovers unchanged for the moment and focus on the wiring. 0.56 sqmm for bass and mid range - I doubt that this is appropriate.

Due to the combination of parts I have on hand and on order, I'm considering using a hybrid bridge rectifier using SS diodes and the uncommon 12Z3 tubes. (12Z3 data sheet)

The PT is rated for 325mA@243Vrms (no CT available). I'm only going to be pulling a constant 140mA, so I expect my loaded voltage to be at least in the 260-270 range.

The datasheet says PIV is 700, but max plate voltage is 235Vrms (330Vpk). It also says max steady-state current is 330mA, but max output current is 55mA. Oh, and it gives a rating for max voltage drop at 110mA. And then the drop curves go up to 185mA.

So which of these maximums actually apply in my situation? I'd like to feed them around 260-270V, pulling about 140mA through a hybrid bridge to a capacitor input. Am I abusing them? If so, am I asking for fun fireworks, or just shorter tube life?

After digging through my parts stock, I realised that I have 2 unused units of the said tweeter, probably purchased more than 10 yrs ago. I intend to use these in a 2 way system. However, the tweeters do not come with any documentation, other than in a cardbox box.

Is there anyone who can assist me to get the specs for these tweeters? I have searched the internet for the specs, but it was fruitless.

Thank you very much in advance.

VK Wong

Due to a project chance, I am herewith selling 3pcs empty PCBs for the well regarded BPPBP - Bruno Putzey's Purist Balanced Preamp:

BPPBP - Bruno Putzey's Purist Balanced Preamp (well a balanced volume control really)

12 euro each + expenses.

Long-time reader and only recent poster, which isn't great for selling stuff, so I'll try to establish some credibility here with the project that's made me sell this stuff: first pic is an in-process of my Korg B1 preamp and 3e TPA3251. More pics coming soon in the Korg B1 thread now that the front panel is done. Y'all are costing me a fortune ;-)

For sale:
* 2x 100microliter Ferrotec ferrfluid, suitable for a pair of 1" voice coils. I did a few sets of Kef 104/2 tweeters with this stuff, seems to work well. This is enough for 2 tweeters. $20 shipped in the US.

* 2x generic 2-channel UPC1237 speaker protection boards. Meant for an Adcom 555 and Bryston 2b that I sold once I heard the 3251. Nice, with dual Omron relays. $10/ea shipped or $18/both. Sold

* NOS Sanyo & Toshiba transistors, from B+D Enterprises circa 2014 so they're probably legit, with receipt, bought for rebuilding the Adcom that went away:
20 x Sanyo 2SC2362K-AA
20 x Sanyo 2SA1016K
4 x Sanyo 2SA1207
2 x Sanyo 2SA1210
4 x Toshiba 2SA970BL
The 2SA1210s are out of stock now at BD, and the price of this order would be $74.68 if they had everything. I'll ship it to you for the same $48 I paid.Sold

PM here and I'll get right back to you. Thanks!

Two Passive Radiators – theory – Instead of placing two PR’s on the outside of the box where space is a premium for a small speaker, would they work if inside the box? For instance, in the picture, there are two possibilities: 1. have the PRs exit at the bottom or 2. Remove the top bar and have the PRs exit out both ends. Or don’t do it because it doesn’t work well.

What are the advantages and disadvantages of both? I would assume if out both ends, then there might be a null of bass sound at 90 degrees but not sure. Maybe not, as two normal PR’s at opposite exterior ends of an normal enclosure, seem like a norm.
Thanks

Hi. Have some active monitors that are too loud at Odbfs. I have no analog attenuation. I would like to reduce decibels by about 20 % the input gain is as low as it can go. Can I change the value of the input trim?

I wanted to ask if anyone has downloaded any Acoustat manuals from the site HiFi Manuals. I go to the screen where it says type in the "Capcha" two words appear. I have tried typing them using a space or running both words together. The next screen shows "404 error occurred". Can anyone advise me how to download these brochures or owner's manuals successfully? Thanks in advance.

Hello,

I made the subwoofer last summer.
Here is a link with some info and two construction pictures (no final pictures yet, sorry). If you are interested, feel free to have a look at:

Link removed by moderation

Works quite well allthough my T-Amp 1400 is underpowered (only 2x700W to 4 ohms).

Best Regards,
Karoliina Salminen

Not possible before DSL crossovers became available, but....

1. present-day sub-woofer systems have drivers which have their resonance inside the passband which is idiotic,

2. whatever charm some may find in full-range or wide-range drivers, the direction of progress has been with division-of-labour into frequency bands a specialized driver can handle well.

Which leads me to a recent discussion of car audio drivers, which aren't always taken any too seriously by folks seeking sound quality outside of cars.

Perhaps an approach that merits some discussion would be to use one of the car audio monster drivers as a sub-sub-woofer in the band below, say, 35 Hz (chosen for relevance for playing that 32 Hz organ pedal note). There may be no reason to buy the best quality car audio driver, just good enough with low driver resonance.

That means then that the familiar subs discussed on this forum could at last properly handle, say 35 to 110 Hz, and so on up.

When we freed mid-range drivers from having to handle woofer frequencies decades ago, we started using small wonderful ear-height mid-range boxes, with many advantages. Likewise, once we free subs from needing to handle that lowest octave, they can be a lot better and smaller even for sealed cabs.

DSL and amps are cheap but floor space for subs is expensive.

Thoughts anybody?

B.

So I decided I've started a few threads on here, but never really got anywhere. Here's a thread where I'll keep track of everything. It'll probably end up a bit like a blog, but discussion is more than welcome.

So far, I have a pair of old EV 15" Deltamax tops with EV DH1a HF units on HP64 horns, with Beyma 15P1200Nd subwoofer drivers as midbass units. Active crossover at ~1.1kHz. I also have a spare set of those Beyma drivers. Having read through Art Welter's compression driver shootout, I'm keen to use the DH1as, as they perform very well. They're stuck on a 2" exit, though - no way of converting them to 1.4" exit.

Below is a thread on what I've been doing so far.
http://www.diyaudio.com/forums/pa-systems/261892-compression-driver-help-please.html

I'd like to widen the dispersion on the HF units, build some subs, and figure out some top speakers that I can actually lift on to stands.


I think I'll go for a set of four (eventually) THAM15s for subs, as they appear to dig low enough for most stuff, while being fairly compact.

For tops, I think a 12" two-way will be okay, provided efficiency is good. My current cabinets are limited at SPL: I'm running a Behringer NU6000DSP (~1200w/ch) for the Beyma 15"s, and hit the limiters during anything bigger than a smallish gig. I suspect I'm simply asking too much of a 2-way system - the free-field low-frequency rolloff comes in around 45Hz, so efficiency is rather low. Groundplane subs would be a much better solution.

After a bit of looking around, I've found these:
RCF - MB12N251
They're available at a reasonable price, and allow the use of a ~40L cabinet tuned to around 80Hz for considerable SPL in the kick region. If anyone has suggestions for a different 12" driver, I'd be interested to find out - those RCFs are the top-end of what I'd want to spend (£100/driver).


I might go for a modular top design, with the mids and HF units in seperate stackable cabinets, for MTM/TMM/TM tops, depending on the SPL needed. A modular design would also make it easy to expand the system later, and, of course make it easy to get those DH1as up high, possibly on a different horn.

I have lots of amplifiers on-hand, and a couple of active crossover/EQ units, so this will be active crossovers and measurements all the way. Preliminary crossover points would be ~1kHz between the DH1a and 12", and ~120Hz from subs to mids.

That's all for now, I'm gonna go make stir-fry.

Chris

Recently finished rereading Linearaudio Volume 2 where Jan Didden published Samuel Groner's article "A New Amplifier Topology with Push-Pull Transimpedance Stage".

This wonderfully written article explains how to implement folded cascodes in both the Transconductance VI converter and Transimpedance IV converter.

I am impressed with the possibilities of folded cascodes since I built Salas Folded simplistic phono.

With proper implementation, the folded cascode tech can increase circuit PSRR by referencing the input of the transimpedance stage to GND instead to one of the voltage rails.

So following Gronner's design I implemented the topology into a high power lateral mosfet power amp.

Please have a look at the simulation below...

Now I will explain the circuit so everyone can follow my reasoning....

IPS - transconductance stage:
J1 and J2 form the typical long tailed pair
Q4 Q6 R23 D17 and D18 form the CCS that sets 4mA in each R26 R27 degeneration resistors. (These are set to 100ohm for improving input stage distortion and slew rate)
Q11 Q12 form the IPS folded cascode
To increase gain, the folded cascode is loaded by twin CCS formed by Q9 Q10.
This CCS must provide 8.5mA so the folded cascode Q11 Q12 works with 4.3mA (slightly higher than the LTP current)(If the folded cascode current is lower than what is used in the LTP, additional distortion at high freq might result because at peak output currents of the IPS diff pair, the folded cascode transistors will switch fully off)
Emitter resistors of the current mirror R54 R55 should have a large value to minimise the noise contribution of the current mirror.... As large emitter resistors will introduce a pole in the open loop gain of the amplifier, two capacitors C14 C29 are placed in parallel with the emitter resistors.
Q13 is a common base transistor used to keep the folded cascode transistors Q11 Q12 at approximately the same collector emitter voltage minimizing offset due to early effect. The base current of Q13 also cancels the base current errors in the current mirror also reducing offset.
Finally the differential signal is converted into single ended by the works of the current mirror formed by Q14 and Q32.

Transimpedance stage:
It is arranged as complementary push-pull configuration so to have a better slew rate response.
Voltage from Q22 emitter to Q23 emitter provides bias for the common emitters Q25 Q26.
R48 R51 emitter resistors are needed to reduce sensitivity to transistor tolerances and thermal effects. Minimizing the value of these resistors is preferable as this lowers the sensitivity to loading of the second stage output node so we should choose their value for a vdrop of < 100mV.
Once these are determined, bias voltage for Q25 Q26 is found through the choice of R25 R39.
Current on the emitter followers Q22 Q23 is set with R46 R47.
The collector current of the folded cascodes Q28 Q29 is set both by the emitter resistors R52 R56 and the base reference voltages set by D3 D7.
Capacitor C38 linking the emitters of the folded cascode is useful to increase transient output currents.

Current limiting:
Q24 Q27 limit the collector current of the common emitters Q25 Q26 to six times the quiescent current.
Simulation predicts that in overload conditions the collector current of Q25 Q26 might increase beyond the maximum ratings of these transistors.

I'm currently building a M2X which will be finished in a few weeks, and I have started thinking about a preamplifer.

I have the following requirements:

1. At least four inputs
2. Remote control
3. Motor volume control
4. Line outputs for headphone amp and tape recorder (in addition to output to the M2X power amplifier)

I already have the BA 2018 PCB and a solution for the power supply. I'm going to use a Muffsy Relay Input Selector (New Product: The Muffsy Relay Input Selector - Muffsy Phono Kits) and an ALPS motor controlled potentiometer for requirement 1, 2 and 3. The Muffsy input selector doesn't support a motor controlled potentiometer out of the box, but should be easy to add (I have some basic experience programming Arduino boards.)

But I'm unsure about the line outputs. Can it be as simple as wiring them directly from the inputs? That is split the signal from the Muffsy input selector to the BA 2018 linestage and two line outputs?

Thanks,
Trond

Hi All,

Does anyone have a spare unloaded tapped horn cab for a 15" driver kicking about? SS15 or Apache 15 etc. It be interested to load one of my drivers in and see how it compares with my current compact ported boxes.

My drivers are faital pro 15hp1060

It appears that I have found a site I have great love for. It makes me wonder... Where have I been? It seems that this is a very well established site and I must thank all you great minds for having me.
I only hope that I might contribute something but am certain I have much to learn here.
It's a great evening here in San Clemente, California and a moment I will remember.
My name is Pete and I truly am thrilled to be here.
Again, I thank you for having me.

I've read on somewhere long time ago, the idea was presented that, by closely look at the imepedance equalization circuit, it is simply related to a 'low-pass' filter where Rz is the attenuation rate for the desired impedance and can be calculated by a simple formula: Rz = Re x 1.25 and Cz is the filter that is established at the starting point of the rising impedance. Unfortunately, I cannot remember the suggested method to calculate Cz from the frequency point where impedance starts to rise. By electrical circuit analysis, could anybody perform this to find the value of Cz without using formula involving Le, but using frequency point of rising impedance instead?

Hi
If someone has FRD & ZMA files for beryllium SB29BAC-C000-4, I will be glad if you share it.

OSH Park has a 3 board minimum, and I'm only building 2 of miro1386's AD1862 DAC, so have one to spare. Bare board only, I don't have any parts to spare.

Design/build thread here: https://www.diyaudio.com/forums/digital-line-level/354078-dac-ad1862-tht-i2s-input-nos-2r.html

OSH board specs: OSH Park Docs ~ Services ~ 2 Layer Prototype Service

Boards were $17.33 each, so how about $19 shipped in the US?

Hi


This amp had its rectifier tube 5AR4 shorted. I replaced it with a new JJ,GZ34S tube. I wanted to measure it tube dissipation, 4 EL84 power tubes. I set the bias setting at "warm". One side DC resistance is 76 ohms and the other is 75.8 ohms. The voltage drop on each side is about 5.1V and the cathode to plate voltage is approx 341V. This means each side dissipates 67mA which is approx 22.9 Watts. Total of 45.8 Watts. I read that this amp is rated 30W. This amp is fixed bias, either at "warm" or "hot". Do you think that something is wrong with the bias circuitry or is it set as such. I could not upload the schematic as it 1.94MB



Thanks

Hi good people.
I am building a 2.1 speakersystem to be powered from batteries, an Xbox supply and the electric system of a tuktuk - Depending on different uses.

Therefore it has to run well on 12-14v All speakers are 8 ohm minimum. Fullranges says 12w rms, so I would like something like 2x30w + 60w 8ohm, but more or less is ok.

Any suggestions will be appresiated.

Cheers!