diyAudio

georgehifi · 2013-01-08 9:21 pm

I posted this by accident on another thread anyway here it should be.

Funny you should bring up the AD844 Jan.
I found this circuit of Pedja Rodic's (attached) and used it as is (NO FEEDBACK) and it worked a treat, best opamp based I/V so far by a long way, it blew the OPA627 completely away I though it would never be beaten except for a discrete I/V of some sort. (And I’ve tried just about every opamp out there)
I used it without feedback as per the diagram and was very very happy. Used with TZ as he has it 1.5K with 1000pf to ground, I think this gives a 1st order rolloff –3db @100khz.
Does the 1.5k resistor have a bearing on what input resistance the dac (PCM1704 in my case) sees?
Because I changed the resistor for 2.2k to get some more gain but this time with a 260pf cap –3db @ 270khz (still all nice and stable with a bit more gain) still very very good.
But I had the feeling it was puchier and more dynamic with the 1.5k resistor even though I had less gain. I feel that the input loading for the PCM1704 is better with the 1.5k than the 2.2k resistor or am I imagining things?.

Cheers and thanks for your input George

Added on the 15-09-2023: This should be gone to after reading all this about the AD844, as it gets very interesting when I start stackng them here on the 31-03-2013
https://www.diyaudio.com/community/threads/using-the-ad844-as-an-i-v.227677/post-3434718

Cheers George

bergy · 2025-01-03 9:22 am

Pass Labs biamp 6-24 Crossover assembled as per discussion thread and related BOM (230Vac) fully functional, for sale at 350€.
From Italy to EU per €350 + shipping.

I assumed people here already know this product, clearly discussed and explained in the discussion thread in the Pass Labs section:

https://www.diyaudio.com/community/threads/diy-biamp-6-24-crossover.357657/

Frequency and slopes are adjustable,

slope (from 6dB up to 24 dB) by dip switches,
frequency by capacitors inserted into their pin header female.

There are also four rotary potentiometers each way, to change frequency by a factor about 10.
Thank you,
Max

Chilli6565 · 2016-08-31 10:32 pm

Hi, I hope to get some help here.
I wanted to re bias my CREEK evo integrated amplifier after it had been dropped in transit

The dc mv drop over both .22ohm 5 watt emitter resistors was about 1mv each!. I re adjusted that to about 7.5mv. The right channel was adjusted to be the same .
The trim pots I used for this were the ones closer to the heatsink.

Dc offset was below 8mv for both channels after 20 minutes at idle

My question is about the two trimpots farther away from the heatsink,what do these do? I did give them a turn one rotation in both directions thinking they might be for the dc offset but it didn't seem to affect that measurement.
Can anyone tell me what these trimpots do and what I need to measure and adjust with them.

Cheers

Chilli

Bas Horneman · 2024-01-06 8:26 pm

What do you guys think? I usually put a small say 220R on grid of EL84. What about 6N3P?

Designed by Gerd Reinhöfer †
Found on this webpage: https://www.jogis-roehrenbude.de/Verstaerker/EL84.htm

Uses (Output) Plate/Anode to (driver) cathode feedback.
Lowers distortion.
Worsens PSRR. Ergo you need a very clean power supply.

Eric Stockman · 2025-01-03 8:22 am

Hello everyone , and my best wishes to you all for 2025!

Once again I experience the same problems with my Pioneer SA-8500 : the volume and balance potmeter...
The sound of 1 channel comes through very very poorly.

However I already cleaned this knob a few years ago, unfortunately the problem came back.
But perhaps the first time I didn’t clean it the correct way?

I don't remember exactly either.
What I do remember is that I cleaned the potmeter with IPA (ISOPROPANOL) and let the IPA ‘sit’ for about 5 minutes.
Afterwards I dryed the potentiometer with compressed air.
Then I probably treated the potentiometer with Griffon contact spray. (Cleaning and maintenance spray for cleaning and maintaining electrical contacts).

After this treatment the balance/volume knob worked ALMOST perfectly. (It's always the sound of the same channel that falters).

It was certainly much better afterwards.
But now it's gotten worse than it ever was...

So again I did some research on what is the correct way to clean a potentiometer and this is the way it should be done:

Spray Tuner 600 into the potentiometer and let it ‘work’ for 5 minutes.
(Spray Tuner 600 is a Precision cleaner for contacts. A mild cleaner for light contamination of potentiometers, sliders, etc. Because the composition is not aggressive, this cleaner is particularly suitable for vulnerable components for consumer electronics, computers and notification systems).

Inject Contact WL into the potentiometer.
(Kontakt WL is a rinse agent that removes dirt).

Dry spraying the potentiometer with compressed air

Apply a small amount of Kontakt 61.
(KONTAKT 61 is the moisture-displacing protective oil for all types of electrical contacts. It forms a wafer-thin, non-conductive oil film on the contact surface that displaces moisture, prevents short circuits and protects against corrosion. KONTAKT 61 increases the functional reliability of plugs, switches and controllers, especially under the influence of weather influences).

So this seems to be the way it SHOULD be done…

The best solution of course , would be to replace the potentiometer (ACV-407B), but unfortunately this ACV-407B is no longer available anywhere.
This potentiometer is also said to be located in the Pioneer SA-7500, but defective devices are rarely offered for sale and it remains to be seen whether this potentiometer is still in 'good' condition.

So the way I see it, cleaning appears to be the only solution.

Fortunately, I have 2 other SA-8500s and the potentiometers of these still work well. I also have an SA-7500 and this potentiometer also 'creaks' a bit. But that usually goes away by turning the sound up a bit.

Does anyone have any advice or comments on how to tackle this potentiometer problem?
Thank you.

PS : written via google translate : sorry for the mistakes

Luvchampagne · 2025-01-02 5:49 pm

Hi
I'm looking to replace the following drivers. Greatly appreciate your help in sourcing these. Came out of a diy that I picked up over the holidays. Would be great to find a relatively "close" replacement.
Thank you very much in advance.

vifa "M26WR-07 04
10.7" woofer.
I've searched and all I can find is the M26WR09 series. I'm pretty sure the 04 represents 4 ohm as the driver is marked that way.

Scanspeak PL18W006-08
7.1" midrange/woofer
According to Parts Express, here are the specs


Nominal Diameter	7"
Bolt Circle Diameter	6.5
Power Handling (RMS)	75 Watts
Power Handling (MAX)	150 Watts
Impedance	8Ω
Frequency Response	30 to 2,000Hz
Sensitivity	87.3dB 2.83V/1m
Voice Coil Diameter	1.5"

[th]

Product Specifications

[/th]


Resonant Frequency (Fs)	31Hz
DC Resistance (Re)	6.14Ω
Voice Coil Inductance (Le)	0.95mH
Mechanical Q (Qms)	2.09
Electromagnetic Q (Qes)	0.38
Total Q (Qts)	0.32
Compliance Equivalent Volume (Vas)	1.17ft³
Mechanical Compliance of Suspension (Cms)	1.33mm/N
BL Product (BL)	7.91T·m
Diaphragm Mass Inc. Airload (Mms)	19.9g
Maximum Linear Excursion (Xmax)	4mm
Surface Area of Cone (Sd)	132.7cm²

[th]

Thiele-Small Parameters

[/th]


Cone Material	Treated Paper
Surround Material	Rubber
Voice Coil Wire Material	Copper
Voice Coil Former	Aluminum
Basket / Frame Material	Cast Magnesium
Magnet Material	Ferrite

[th]

Materials of Construction

[/th]


Overall Outside Diameter	7.125"
Baffle Cutout Diameter	5.625"
Depth	3.125"
# Mounting Holes	6

[th]

Mounting Information

[/th]


Sealed Volume	0.18ft³
Sealed F3	81Hz
Vented Volume	0.5ft³
Vented F3	49Hz

[th]

Parts Express Staff Recommended Enclosure Volume

[/th]

norman bates · 2019-10-26 12:32 am

Anyone playing with these ?

I'm thinking 1 in a big .56 qtc sealed (when port stuffed anyway) as a center channel under my tv.

And yea, I've had 8" before and am well versed with their dispersion.

But couch wide, it should be fine for bringing out voices.

Looking here (post 25)
W8-1808 vs W8-2145
seems there is a lift in response past 1khz (above baffle step ?)

yet manufact freq response looks better than most 8's past 1khz (flatish).
W8-2145 - 8" Paper Full Range - TB SPEAKER CO., LTD.

Norman

phaze267 · 2024-10-03 10:09 pm

I propose a very simple mod to his amp which provides about 10X increase in output power at 2% distortion, and only requires adding 3 resistors to the stock circuit.

I recently purchased this amp knowing it would need to be modified in order to put out power anywhere close to the spec of 7 watts. My stock amp only put out 0.45 watts at 2% distortion and 1 watt at 3% distortion.

Stephe at Skunkie Design has done a wonderful job of testing and modifying this amp. Her many videos are on YouTube. She ended up with a cascode front end and replaced the rectifier tube with a 5AR4. This mod is called the Skunkie Mod. Her design apparently performs well, and involves totally rewiring the 6SN7 circuitry, and many new parts, although they are not expensive.

I have designed and built several tube amplifiers and was interested in finding out why the stock design performs so poorly. By looking at the 6SN7 characteristic curves, it was obvious that the second 6SN7 stage was biased incorrectly. The plate voltage is too close to the power supply voltage, which results in not enough positive voltage swing to drive the 300B tube. Therefore, this one stage limits the power output.

The mod involves adding a 39K 1/2 watt resistor in parallel with the existing 33K cathode resistor in the second 6SN7 stage. This increases the current through that stage, which lowers the plate voltage (see characteristic curves). A 10uf 250V capacitor can also be added in pararallel with the new resistor to slightly increase the bass response.

A 10K 3 watt resistor is also added in parallel with the two 20K resistors in the power supply circuit to increase the voltage to the 6SN7 stages. Finally, an optional mod is to change the rectifier tube to a 5AR4. This increases the power supply voltages and provides a softer power up, which will increase the life of the tubes.

The final output power result is shown below. 5.1 watts at 2% distortion with the stock rectifier tube and 6.2 watts at 2% distortion with a 5AR4 rectifier tube. This is as good as, or better than, the Skunkie cascode mod.

I have made this modification and it sounds really good. I have not heard the Skunkie Mod, so I can’t compare to that. I’m using Wharfedale Lintons, which are about 89db sensitivity, and the modified A50 drives them to satisfactory levels in my 14’ by 12’ listening room. I was pleasantly surprised by this. My listening position is about 8’ from the speakers.
I also have a Willsenton R8 amplifier which I really like, but I actually prefer the A50 on a lot of music. It’s not as analytical as the R8. I use a DIY switcher to switch between the two amps.

domtweaker · 2025-01-03 6:29 am

Looking for a 100 K TKD. Quad channel Volume Control Motorized pls .

cheers

Kyleag89 · 2025-01-03 2:23 am

I purchased an accuphase clone 3850 preamp kit based off of Micheal Beany's YouTube video. It requires a 15 0 15 power supply and has 7815 and 7915 regulators on it. Until I get a transformer with the right secondaries can I test it using 2 DC power supplies? I have 2 24v 1amp wall warts that are isolated, can I wire these to the power input before the bridge rectifier or should I solder directly to the input pin of the regulator?

Waboo · 2016-11-28 9:34 pm

Hi all,
My very first post here. I've been away from speaker building for some time now and I'm looking for something to build.

I'm somewhat intrigued by this newish woofer from Eton for use in a sealed floor-standing 2-way. In doing internet searches for others using it, I pretty much come up empty. It looks like it would make a nice 2-way with decent bass, considering.

Any help would be appreciated.

Eton Link:
https://www.madisoundspeakerstore.com/approx-8-woofers/eton-8-412/c8/32-hex-symphony-ii-8-woofer/

Terry

mordikai · 2025-01-03 5:20 am

From Monte Kay:
must be gone by Saturday.
montekay@gmail.com
Login to view embedded media

OllBoll · 2024-08-10 3:12 pm

I wish to sell a bunch of GRS planar drivers:

4x PT5010-8
4x PT6825-8
18x PT2522-4

All of the drivers are in the original packaging. None have been used long term in a speaker. They have, however, been used briefly in individual tests like polar plots and distortion sweeps in different speaker prototypes.

I want to sell them not due to any problems with the drivers but because I have fallen into the rabbit hole of building my own custom physically curved planar driver for my dipole CBT.

I prefer to ship within EU to avoid problems with tariffs. I wish to handle payment through paypal and all packages will be shipped with tracking. I will send a paypal request and when paid will create the shipping label. I have physical access to the drivers and are able to ship the packages Sunday, Saturday and Monday.

Price for the drivers including shipping within the EU:

GRS PT5010-8

2x 260 €
4x 500 €

GRS PT6825-8

2x 140 €
4x 250 €

GRS PT2522-4

2x 100 €
4x 170 €
6x 240 €
8x 310 €
10x 380 €
12x 450 €
14x 520 €
16x 590 €
18x 660 €

In the odd case that you happen to be close to Sollentuna, Stockholm in Sweden and want to pick them up then you can pick them up without having to pay for shipping.

pbilous · 2025-01-02 4:21 am

I have built myself Modulus anniversary edition so this one is for sale.

Measures and sounds amazing - very detailed yet “musical” mids; bass is tight and “recognizable”/better “pronounced” compared to other amps; clear highs.

Only good quality parts sourced from Mouser store were used.

Very nice aluminum chassis.
Anti vandal power switch with LED brightness adjustment.
Neutric XLR connectors.
Isolation sheet of plastic behind SMPS300 30V psu from Connex Electronics.
Measured to validate results and it gets 75Watt into 4 ohms with very low THD of 0.0006%

DM if interested.
Looking to get $500
Will ship USPS priority within US only.

slerner · 2024-12-18 10:22 pm

I'm getting frustrated, looking for D shaft knobs for 2 projects. They don't have to aesthetically match the OEM. They just need to fit, with indicator lines aligned as described below. Any suggestions, please?
I'm looking for eight unskirted D270 knobs for a 1990's Peavey XRD 680S powered mixer. The only exposed part of the pot is the D portion of the 6mm plastic shaft, which extends 8mm above the panel. Is that what they call 'hole-mount'?

And I need three 6mm D0 skirted knobs for a 2007 Peavey ValveKing Royal 8 combo-to-head mod, i.e., the chassis is bolted to a board upside down. It came with 6mm-shaft D180 skirted chickenhead knobs and I need Dzero knobs, so the pointers align correctly now that the amp is upside down. It's got panel mounted pots, so the knob has to skirt around a 12mm nut and the 6mm D shaft ends 12mm above the panel.

audiodreamer II · 2025-01-03 12:23 am

Hello all!
I am an electrician by trade. As with a lot of things that has to shell out money for, at least half of it is labor and overhead. So DIY it is.
I just hope I can make it worthwhile and enjoy the fruit of my labor.

baeijsman · 2024-05-28 12:51 pm

...or 'The Dual Mono ACA Mini Turbo' to be precise.

It's no secret that I am a huge fan of the ACA Mini for many reasons.
It sounds a lot better than you'd expect, it's loud enough for 95% of my needs, and it's power-consumption is low for a real class A power amp, just to mention a few.

Unfortunately I also happen to own some low impedance speakers, AND I have a need for total control of the low end of the frequency range.
So, a little while back I posted this schematic and asked the question:
'Would it be possible to build a turbo-edition of the ACA-Mini and perhaps get a small increase in DF?'
Fortunately Papa said 'Do it!' (or close), so I set out to build a Mini Turbo, and this is how it went down.

In The 21st Century · 2025-01-01 3:31 am

Howdy folks! I’ve heard about Rose streaming products, and how bold and sublime they are when it comes to sound quality. I recently purchased an RS-150b. The only problem is recovering your password and email address if lost or forgotten. They give you a temporary password to recover it, but that turns everything into a nightmare, because for some reason it still doesn’t allow you to recover and access your account. It then says your account doesn’t exist, or this email address is unknown. There’s no customer service phone support which even adds to the onslaught. If there’s anyone who’s experienced this problem before with a Rose account, please help me. I’d be very grateful.
Thanks👍

rongon · 2024-12-30 5:01 pm

I don't know if this is a simple question or not, but...

In a classic tube guitar amp like a Fender Deluxe Reverb or Twin Reverb, when you dial in a 'clean' sound at moderate old-style country music or jazz combo volume, about what level of THD is there in the signal from the amplifier (not including the speaker here)?

1% THD?
3% THD?
5% THD?
10% THD?
More?

I'm playing around with designing a guitar preamp with pre-gain and post-gain controls. With the pre-gain down at '1' or '2', I'm wondering what level of harmonic distortion should be in the output signal at that point. I figure at least 3%, 2nd and 3rd harmonics dominating, but I don't actually know.

Anyone?

JohanLiw · 2025-01-02 10:01 am

My name is Johan, and I’m from Stockholm, Sweden.

My primary Hi-Fi setup consists of a pair of ZMF Verite Closed headphones and an RME ADI-dac DAC. I’m experimenting with RPI streamers and am also considering taking on a DIY amplifier project in the near future.

Great to be here and learn from all the shared wisdom!

/Johan

Ankim · 2025-01-02 8:10 pm

Hi everyone, I am new here and introducing myself to the group. I have a little experience with DIY audio - my first project was the C-Note kit from Parts Express. That was pretty straightforward and gave me the confidence to build my own speakers. I went on to build some 2-way Econowave inspired speakers with a 15" woofer and a 1" compression driver with a wave guide. I have gotten those to the point where I can listen to them and I am very happy with how they turned out. I still have to finish them by adding veneer and duratex. I have been a hobbyist woodworker for years so that part is not hard for me.

The next step in my journey is going to be tackling some DIY electronics. I would like to start with a preamp and am considering either a Tubes 4 Hifi Sp-14 or an Elekit TU-8550. I do prefer the SP-14 since it has a remote capability. Although, I am sure a remote controlled ALPS pot would be able to be added to the Elekit.

I have been lurking on this site for a long time and have decided it is time to join the discussions - talk you you all soon on the main boards!

-Ankim

Adelmo · 2024-12-22 11:33 pm

Hi

I was wandering if anyone has already attempted to DIY a tonearm with ferrofluid bearing .

Tks n rgds

Adelmo

SoundRight · 2015-01-25 12:10 pm

I have probably read more guff on the "failings" of this horn than virtually any other! Most are from those using the proprietary JBL compression drivers, which I accept I have no experience of and I am guessing many have tried to attach a passive crossover which of course is a disaster waiting to happen. This is a "short throw" horn, meaningless of course but does infer a wide dispersion (90x40) and like the similar DDS, EV, Beyma variants is entirely appropriate for studio monitor as it is for live application depending on your choice of compression driver.

For a relatively low cost you can obtain DATs software impedance measuring device from Parts Express...and be prepared for a shock!! The impedance of horn/driver combinations as many are aware are unique to that pairing and complex. You will need series shunts, zobels and response correction and if you do not have a X-over simulation programme your chances of getting it right tend to zero. Small mistakes will lead to substantial peaks and troughs in the response.

Now if you are active the story is very different. I am posting a few images here of what this horn is capable of. All are with the Beyma 750Ti driver. Only taken "in room", on axis and with ARTA and True RTA. Gated was taken but was so similar to the pink noise I haven't shown it here. Obviously it revealed more small peaks and troughs but in terms of trend the responses were very similar. I set a 24dB/Oct LR filter at 200Hz just for driver protection.

Clearly this horn/driver is not capable over 16Khz but at my age not so relevant! Anyway some will add a tweeter and I believe a good operating range for this combination is going to be around 800Hz to 8KhZ (Active....analogue or DSP!). It is just possible to see on the plots the small response anomaly at 800Hz which coincided with the resonance of this driver. I have designed a series notch filter just to notch out this impedance spike but in truth -6dB down at 800Hz with an active (DSP) LR crossover and the effects will probably be minimal.

An interesting alternative, particularly for those that like the simplicity of a "two unit" system (certainly advantages to be had) is to fit the BMS coaxial 2" compression driver. This has an Fs of 300Hz for the midrange diaphragm (well below the horn cut off) and the coaxial tweeter section extend to 35Khz. Although I am not a fan of using horns near their cut off, I would suggest this may provide superb performance down to 500/600Hz?

Anyway ..here they are for the Beyma 750Ti/2380A..first is uncorrected, second and third are ARTA and True RTA versions corrected with a final extra hf tweak applied to the True RTA version. Ignore the "levels" shown on the plots as this aspect is not calibrated.

mdlover · 2025-01-01 7:55 am

Up for sale is an used Acoustic Dimension 41-step attenuator at 10k ohm.

It is of early more sturdy production.

Asking $100 + shipping.

Mark Johnson · 2018-11-03 7:06 pm

I've got my First Watt M2x amplifier doing a Thermal Soak right now. M2x is a Class A amplifier that draws 160 watts from the AC mains. With USA voltage that means about 1.4 amps average mains current.

This amp has two Amphenol CL-60 inrush current limiters, connected in parallel for USA: each ICL feeds one of the two parallel primary windings on the power transformer. Thus each CL-60 sees about 0.7 amps average current. But, checking its datasheet, the CL-60 is designed to run at (1.2A <= Current <= 5.0A). Uh oh.

General Electric / Thermometrics / Amphenol don't specify the ICL body temperature on their datasheets, but other companies do. I've attached a representative one below. It runs at 149 degrees Celsius! wow.

I just measured the CL-60 ICLs in my M2x. After three hours of thermal soaking (power applied, inputs shorted), the body of the CL-60's measure 33.8 degrees Celsius using a Type-K thermocouple, and 32.9 degrees Celsius using an infrared no-contact thermometer. That's a far cry from 149 C. So I'm thinking the CL-60 may not be the best ICL for this particular amplifier.

Poking around on Mouser's website, I found the SL15-22102 Inrush Current Limiter from Antherm. Its cold resistance is 22X higher than the CL-60's cold resistance, so it gives a whole lot more protection against inrush. Its max energy rating is 40 Joules, slightly higher than the CL-60's rating of 36 Joules. Its resistance at 0.7 amps of average current is about 2.5 ohms, so the mains voltage "lost" to ICL is 1.75 volts, which is about 1.5% of the total mains voltage. I find this acceptable. I think I'll order a few of these and play around with them. Perhaps the best choice is something sort of in-between this one, and the CL-60 original.

_

limono · 2024-12-28 10:04 pm

I'm selling my spare pair. Very nice condition. I will snap some pictures soon. $400 (net) and I can post it to anywhere in the world

Tube Radio · 2025-01-02 10:44 pm

There any reasonably priced new or older small preamps where the volume can be controlled by a Dish Network remote?

Would prefer it have an optical input but that's not necessary as I can get an optical to RCA adapter box.

I found this which I can put in a box with jacks and use a DAC with optical input.

https://www.parts-express.com/Line-...oard-with-Remote-6-12-VDC-320-6012?quantity=1

I don't know if it can be controlled by a dish network remote though.

capslock · 2025-01-01 6:37 pm

This is from the car radio / sat nav unit of a 2014 Ford Galaxy / S-Max. Those units were introduced after the 2010 face lift and were made by Blaupunkt (Bosch). The units emit a high pitched noise from the screen and through the CD slot (7.9, 9.9 and 15.8 kHz). Apparently, the power supply for the CCLD does this. There is no good way to power the PCB when it is disassembled, so I am not sure how the guy who posted the picture below identified the components. His guess was it came from the electrolytics or the large MLCC cap that he misidentified as a coil.

My guess it is the MLCC or the transformer (the windings are not secured by tape or lacquer.

Anyway, I desoldered the large cap without doing a prior in circuit measurement. The contact plates started gliding on the cap when I did this. Afterwards I measured 8.5 nF which seems way to small. I tried floating the plates back i place but that resulted in even lower readings.

So what could the case size be? It is about 7 mm long, 6.4 mm wide and 4.8 mm high. This is a little off from the 2924 case often used for solid tantalum caps (7 .3 mm x 6 mm).

Once I know what the size is, I will have to find out what capacitances were available in that case back in or before 2010. I am guessing the operating voltage will be 12 or 5 V.

Mouser's selection guide tells me there are Kyocera 10 µF 25 and 50 V X7R caps in a metric 7361 case, but my case is a little too short and too wide for that (just confirmed with digital calipers)
(edit: that case also looks quite different https://www.mouser.de/datasheet/2/40/MH_CeramicCapacitor-3165541.pdf)

The large cap connects the large contacts of the two transistors (?) sitting right next to the transformer. They are marked 435ZDG. The other transistor like thing seems to be a voltage regulator and is marked RAV117AV.

https://www.motor-talk.de/forum/navi-nerviges-fiepen-t4268623.html
https://www.motor-talk.de/bilder/navi-nerviges-fiepen-g77078414/004-i208918361.html

Beamer1707 · 2025-01-02 3:04 pm

I have a Kenwood Excelon x802-5 5 channel amplifier running 4 JL audio coaxials at 50 RMS. There is two gain controls, one for channel A and another for channel B. Each gain controls two channels. To set the gain, I used a multimeter and a 1000hz test tone at 0db. Target voltage was about 14.1. Issue is I can get close to that voltage (about 13) but if I go past a certain point on the gain, the amp starts to buzz, and the next channel jumps to about double the voltage. Is this normal? Is the amp clipping, or should I call Kenwood?

wrenchone · 2011-07-11 9:13 pm

Attached is a photo of the first proto of an SE amplifier( the "SiC Puppy") using the Semisouth 085 silicon carbide JFET in the output stage. The front end uses the Supertex DN2540N5 depletion mode mosfet. I choose the Semisouth part over the IXYS depletion mode parts due to the extra headroom afforded by the 1200V rating, allowing me to choose B+ voltages with a bit more freedom. The circuit (to follow) is set up just as if the two parts were pentodes, with partial feedback from the output drain to the input drain, plus a limited amount of global feedback (disconnected at firtst. I used the One Electron UBT-1 1.6k transformer because I had a pair on hand. The output stage bias is set for the maximum primary current rating of the UBT-1 (150 ma). Next is a power-up with a DC supply to chcek stability of the output bias.
The heat sink is one of Papa Zen's giveaways from the very first Burning Amp in October 2007. I'm thinking of running the amp in a dual mono configuration using a pair of ~150VA step-up/isolation tansformers, which when configured for 230V output and rectified will give me ~320VDC B+. There is an on-board capacitance multiplier for ripple reduction, feeding a 270uF bulk capacitor.

More to come - this is just the first heads-up.

mnhiphop101 · 2025-01-02 8:37 pm

If it's so important that the audio signal ground be tied to the input ground, why aren't they just connected internally?

Jonwb1 · 2024-12-22 5:34 pm

Hi and Happy Holidays. My best and favorite amplifier is a Denon PMA-737 I bought new in 1985. It still sounds great. However, on all inputs (FM tuner, DAD and Monitor), it has an issue where upon turning the Volume control up from 0, the speaker sound is first heard on the left side, and then gradually, the right side comes up and balances dead center once the Volume control is at the 2-3 position. The same thing happens using Headphones via the headphone input, and with other sets of speakers on both A and B speaker terminals.

I've De-Oxidated the Volume pot and Balance control several times but the issue remains. I've also re-soldered the eight connections that hold the volume potentiometer in place. My expertise stops about there so I'm wondering if any of you could suggest another solution or maybe point to the next possible cause?

Thanks

dromichet · 2023-01-27 4:57 pm

Hi Guys,

I've been using the Lampizator circuit attached to a TDA1541A DAC for about a year now. I'm very happy with the deep sound it produces and it suits my music taste which is mainly vocals and strings. Therefore I've never really tested it with a VTVM or oscilloscope to see how the FR is, I was just happy with the sound.

Out of boredom, the other day I've measured the FR and it looks way out of specs. I have 2 of these units built and both of them have the same lazy specs. Basically the curve is not flat at all with about -5db at 10KHz and -11db at 20KHz. The sound it produces doesn't really seem to reflect these number though unless my ears are getting really bad. The same numbers are shown on the VTVM and osc.

The TDA1541 has flat FR. The coupling cap is a ClarityCap.

Just looking at this circuit, does it scream crappy FR? Is there something I can do to improve the top end or that's just how this circuit works? I guess I have a case of FOMO.

Lampizator has a couple of circuits, one with 6N1P and another with 6N2P. I'm attaching both of them as well as the power supply schematic used, I've tried both and they both have the same FR.

Thanks

BHTX · 2024-12-31 11:52 pm

Would it even be possible to use these in an automotive application? I figure a small enclosure mounted at the pillars might essentially ruin the output, but I'd like to be shown otherwise.

Thoughts: Maybe 1.6 KHz 1st order, or 800 Hz 2nd order to an 8" widerange midbass/full range without highpass, crossed to a sub around 100 Hz with shallow slope for a very musical/non-fatiguing system. Possible?

I remember TC Sounds offering a similar product at a high price under their Audio Pulse name shortly before they went out of business. Never heard anyone talk about them who actually had experience with them though.

Beamer1707 · 2025-01-01 3:57 pm

I currently just installed a Kenwood Excelon x802-5 five channel amplifier in my car. I have 4 JL audio coaxial speakers running at 50 RMS and a Kicker sub at 500 RMS. The bass is good... but the vocals do not get as loud as the factory system did before I replaced it.
Don't get me wrong, it still gets loud. But it never gets to the point where you have to turn it down because your ears are ringing. The old system had four 20 RMS tweeters. I set all the gains with a multimeter, I have the gains set at 3/4 of the aftermarket head unit's max volume, and it is delivering the correct voltage to all speakers.
Should four 50 watt speakers be louder than this? Or do I just need more tweeters/midrange to make it louder. This is my first time installing a car audio system, so I'm not familiar with how loud these speakers should be. Any help would be greatly appreciated!

Klaus983 · 2025-01-02 5:36 pm

Hello everyone,

My name is Klaus and I am pleased to introduce myself here in the HiFi forum.

I have been active in the hi-fi field for many years. During this time I have tried out a lot of different components - from turntables and amplifiers to different loudspeakers. Each new component has improved the music experience and increased my enthusiasm for good music.

My favorite way to listen to music is with active speakers. I appreciate the clear and direct sound reproduction that these speakers offer. They fit perfectly into my setup and let me enjoy my favorite music to the fullest.

Two years ago, I tackled my first DIY project: I built my own speaker cabinet. It was a great experience and showed me how much fun building hi-fi components myself can be. It also expanded my technical understanding and my craftsmanship skills. Since then, I've been even more motivated to tackle other projects.

Now I want to take the next step and work with horns and PA chassis. I find the combination of these technologies exciting and am looking forward to discovering new sound possibilities and implementing them in my own projects. I'm looking forward to the challenges and to finding creative solutions.

Exchanging ideas with other hi-fi enthusiasts is very important to me. I believe that we can learn from each other and achieve great results together. That's why I'm particularly looking forward to exchanging ideas with you here in the forum, benefiting from your experiences and perhaps passing on a few tips myself.

In my free time, I like to listen to different types of music, from new artists to classical pieces. This diversity motivates me to constantly look for new ways to improve the sound quality of my system.

I look forward to many interesting discussions and exchanges with you all. Have a good time in the forum!

Best regards
Klaus

golfr123 · 2025-01-01 7:14 pm

Better to put car midwoofers under front seats in pre-made amplified set-up or put in 6 1/2 inch space(no box) in lower front doors and connect to Helix M SIX DSP amplifier?
Does being under seat muffle sound?

bohrok2610 · 2024-11-14 3:09 pm

Over the years I've built a few ADCs first with AK5394A and later with ES9822PRO. I've used them mostly in my measurement setup together with my DAC boards and USB-I2S boards. I never got to making a chassis for them so they have been laying naked on my desktop gathering dust and especially cat hair. Sometime ago another member asked if I had an AKM ADC for him to evaluate. This inspired me to finally put both my AK5394A and ES9822PRO ADCs in a box.

I've had good experience with Hammond 1455 series aluminium project boxes so I decided to use Hammond 1455K1201 box (120x78x43mm). My ADC boards are 100x50mm so using them together with an I2SUSB board and PSU (new SilentSwitcher) was a tight fit. I also had to make front and back panels for the box.

Here is a picture of both ADCs front and back. ES9822PRO on top and AK5394A below.

ES9822PRO version has more functionality so both front and back panels are slightly different.

Here is a picture of the PCBs inside the boxes.

From top: AK5394A ADC, ES9822PRO ADC, I2SUSB, SilentSwitcher. I2SUSB board and SilentSwitcher work with both ADC boards. ADC and I2SUSB boards are sandwiched together with a pin header.

Both ADC boards have similar circuits: AC coupled (DC coupling also possible), input stage buffer opamps followed by a differential opamp, low noise regulators for critical analog & digital supplies, buffered NZ2520SDA clocks with clock output for dac synchronization. External clock input is also possible. ES9822PRO version has also a mono switch and clipping indicators. On the bottom side of ADC boards are jumpers that short input capacitors for DC coupling.

Here are key specs:

Input impedance 10kOhms
Input voltage 0dBFS level is 4Vrms (fixed).
AC or DC coupling.
Full digital isolation (I2S, I2C, GPIO). No USB isolator.

I decided to have fixed input level as I have other devices for input scaling (Autoranger and Pete Millett's soundcard interface).

ADCs boards require +/-15V for opamps and 5.5V for analog & digital circuits. I2SUSB board needs 5.5V but it can also be jumpered to use 5V from USB. So SilentSwitcher is a perfect fit for powering both boards. Both ADCs can be powered from a 5-12V DC source (e.g. USB PD powerbanks). To show how well the digital isolation (and SilentSwitcher) works in all following measurements ADC has been powered from a noisy computer USB port.

In the next posts I'll discuss the ADCs in more detail and also provide board schematics, gerbers, boms and FW for I2SUSB if someone wants to DIY these (not SilentSwitcher). BOMs have Mouser product codes with the exception to AK5394A (obsolete) and clocks that can be sourced from Digikey.

johnmarkp · 2025-01-02 7:26 pm

My old DIYINHK 9018 board gave up the ghost. Does anyone have a 9018 board they want to get rid off?

Thanks

marcomariutto · 2025-01-02 6:58 pm

The USB input of my Octave II DAC stopped working today, and their website seems to be down so I suspect they might be out of business.

Does anyone happen to have the schematic by any chance?

Thanks in advance for reading this

Audio>X · 2025-01-02 7:02 am

Hello everyone, Happy New Year 🙂
If you were to use cheap (current modern type) Chinese power transistors at half their rated VCE, what other concerns would you have?

veeblefetzer eddy · 2025-01-02 7:29 am

...a hardware question: I'm in the second half of building a simple 12AU7 line stage designed for SS amps, a variation of Matt Renaud's well-known "Tube Color" arrangement.

My 12AU7 collection is extremely random. Not a matched pair in the bunch. Being OCD-afflicted about symmetry, I'm thinking of rewiring (not redesigning) so that instead of stringing the plate follower in the same tube with the cathode follower, the first gain stage would occupy one tube; the second in the other. IOW, V1's plate follower would drive V2's cathode follower. Ditto for both channels, bearing in mind that a fair amount of crosstalk would be somewhat desirable for my hearing-impaired purposes. Apart from arranging the four triodes side-by-side instead of in tandem, it should be exactly the same circuit as printed.

Might there any hideous consequences to this scheme?

ranshdow · 2024-12-28 7:53 pm

For sale is a fully functional Iron Pre Single Ended with an RJM Emerald phono stage hardwired to input #5. This was the original version featuring matched Toshiba JFETs and Cinemag CMOQ-4HPCs. The chassis baseplate was modified to accommodate the dual mono Emerald phono stage, which receives power downstream of the Iron Pre's regulators.

The on-switch is at the back. The power LED is bright and is powered by AC off of the unrectified transformer secondaries.

Asking $600 obo, or trade for an Iron Pre Balanced chassis and completion kit. Thanks for looking.

nyekike · 2025-01-02 5:15 pm

Dear Forum,

I am an IT guy from Hungary, getting deeper and deeper into audio listening. My system is based on Heed Audion devices, made here in Hungary: I have an Obelisk DA dac, and Elixir amplifier,and a pair of Dorn Herald speakers. I recently acquired an Ian Canada streamer, which brought me here. The streamer is already powered by a linear PSU built by me, and I am planning to build a few more audio electronics also. The next very much might be a clone of the Heed Canamp headphone amplifier.

I am sure I can learn a lot from this community, and hope I can also add a few of my experiences to the common knowledge base.

Gergő

lineup · 2024-12-28 4:34 pm

This headphone amplifier has a typical FET spectrum.
That is most 2nd harmonics.
The distortion is rather low for being only 3 transistor amplifier.

Lekek · 2025-01-02 4:30 pm

Hello DiyAudio members,
I recently saw a local listing for 2 Saf214.50 8 ohms subwoofers and thought about buying them. I wanted to use a monoblock amp and let them run parallel on 4 ohms. They have an rms of 2x2000w and since i dont want to spend a fortune on an amp i thought about running them on 500-1000w max per sub. What amps would you suggest that are not more then 400€? Or is it more wise to go for the cheaper 2 b2 riot 12 v2 dual 4 ohm and 750w rms and buy a better amp?
Thanks in advance!

bonesbiggis · 2025-01-02 9:49 am

I have a power amplifier that blowing the main fuse sometimes at startup ?

And some times it start like normal. 🙂

hbtaudio · 2024-12-16 5:57 pm

Ursuppe

Since I don't want to further contaminate @jxdking s nice thread, I hereby start a container for all new thoughts on the Quad-405 dinosaur.

0.001% THD horizontal without TMC, only current dumping!

Dear reader,
please see the Ursuppe thread. We still have to find a way to hopefully get 50 real watts out of the amplifier core.

Q9 is MPSA43.

HBt.

w5jag · 2024-09-16 3:40 am

After a few years of solid state RF diversion, I found myself missing the difficulty and inconvenience of vacuum tubes.

As a get back into it warm up, I thought a small utility amplifier similar to the one in this thread ( that also generated the DHT SSE ):

https://www.diyaudio.com/community/threads/tubelab-se-removing-mosfets.291593/

but built on a 3D printed chassis, instead of a cake pan, could be useful to me. It won’t need to be much of an amplifier - it will join the kitchen table lineup at my lake house and provide some tube audio sound for the second generation of RF stuff, while also providing a low current, tube voltage, power supply if / when needed.

If 3D printing a chassis proves to be a viable means of constructing a tube amplifier, then I might go further forward with the DHT SSE project that started the original thread (now time locked) on this subject, but a more likely end point would be a 3D printed chassis for my existing DHT SSE.

Since this is the TubeLab forum, the objective is a low power / low heat SSE monoblock, while also exploring what will, or what won’t, work in terms of construction on a 3D printed chassis.

I already have a chassis printed up, and a working power supply completed. The power transformer is a $1 hamfest scrounge, that on the line voltage here at the lake outputs 230-0-230 and 7.2 volts on the filament winding. It is mounted above the chassis by the width of a #8 nut and a second 3D printed washer so that air can flow around it for cooling and minimize heat transfer to the plastic. The chassis is beefed up a bit in this area to support the weight of the transformer.

The rectifier tube is a 6X5. This tube was selected because, AFAIK, it has the lowest voltage drop ( 22 volts ) of any of the common 6 volt rectifier tubes; despite its somewhat poor reputation, this type has worked flawlessly in the utility amplifier in the ham shack.

The power supply is a generic CLC circuit, with a 150K bleeder, and a Hammond 154M 2H choke. The input cap is 4.7 uF and the out cap is 100 uF. The secondary of the power transformer has pretty high resistance - about 190R / leg, so I did not add any series resistance between the transformer and the tube.

Each filament line has a 0R5 resistor in series to drop the filament voltage to an acceptable level. The string is elevated to 1/6th the B+ voltage by a 150K/27K voltage divider.

All power supply voltages are available at the rear panel octal socket. The output voltage ( loaded by the bleeder and the elevator divider ) is 300 VDC. The filament voltage under the 6X5 load is 6.4 volts. The 6X5 data sheet indicates I should get 250 volts up to about 55 mils. Based on prior experience, that will be pretty marginal for the CCS loaded 12AT7 front end, so some improvisation may be needed here. PSUD, which takes into account some of the resistances, is less optimistic.

(Most of ) the wiring is some stiff teflon insulated stuff that I got at a hamfest. The other parts are cheap generic AliExpress stuff. The metal frames / socket parts are daisy chain grounded to the safety ground for (some) shock protection.

The chassis is surprisingly rigid, much more so than most of the inexpensive aluminum chassis. Better than a cake pan for sure. The .stl is attached.

So far, so good. It has been burning in for a few days, but without any load, no real heat is being generated.

Win W5JAG

edit: the original thread on this subject: https://www.diyaudio.com/community/threads/3d-printed-sse-parts-and-another-dh-sse.361798/

vinay · 2024-05-18 9:53 pm

I have 12 of the Aleph-X and 6 of the Aleph-Mini, don't think I will get around to building these.

UncleBernie · 2024-12-31 6:07 pm

Hello everybody,
I wonder if somebody could give me a source (Europe preferably) for the pins you can see on this Quad 303 board ?
By the way the picture is from Dada electronics and the site is out. Anybody has any info ?
Thank a lot and have a good new year night !

rawex · 2025-01-01 3:46 pm

Hi to all,
Rogier from the Netherlands here.
I'm interested in soundstream car amplifiers from the "handcrafted in the USA" era. I currently own 3 of them. Now in the process of building a system again after I had them stored in the attic for some years
Embarking on a mission to restore and recap a Rubicon 604, Rubicon Lil' Wonder and a Reference 404s. Love fixing stuff to give it a second life, tinkering my car Honda Civic VIII hatchback. Little knowledge of electronic circuits but eager to learn.
I hope to find some advice and information here.

poler · 2010-05-13 9:29 am

I wanted to start a thread so members can show off their DAC creations. 🙂

gaborbela · 2012-10-04 1:01 am

Hello

I open these thread for these all Hitachi Lateral & Jfet amplifier.
Here is the circuit & website.
A Paul Kemble web page - Hitachi Fet designs.
Now for these amplifier the mosfets are still available but the JFet must be replaced because they are no longer on the market.
We started a conversation about these amp on the Naim 140 clon from Ebay thread.
We think it is time to keep that threat to Naim clone and open a new for these.
AndrewT advised to dedicate these amp to Borbely...He was famous using fets in his own high-end amplifiers etc.
There is two amplifier circuit. You all welcome if you interested to comment, redesign etc these amplifier.
To the all Hitachi fet I have all the mosfets at hand just need the JFet.
I really would like to give a try (at least test these amp)but not without modifying the front end since those JFet are past now.

Greetings Gabor🙂

Shortpeoplearmy · 2025-01-02 1:25 am

Hey guys and gals, amateur audio enthusiast trying to get educated 😂 I enjoy beefing up car audio mostly subs but I will replace a door speaker if necessary I've also been researching home audio so eventually I can fabricate my own home audio for a theatre room! I've constantly got questions so I'll more than likely be a frequent flyer. Thanks for having me!

altec9440 · 2024-12-31 3:46 pm

I am rebuilding some speakers from a modified/damaged Altec cabinets by a previous owner.

My idea is to reinstall boomer and tweeters in a new enclosure maintaining the dimensions of the original.

However, a few particular points concern me because I wouldn't want to change the "sound" of the speaker.
I would like to have your advice on assessing the degre of impact of modifications:

- Currently the original Altec enclosure is made of plywood for the back and sides and chipboard for the top and bottom. What would be the consequences of a single choice of materials?

- There are edges of around 2cm in which a protective strip was inserted like for formica furniture from the 60s. The removal of these edges does not affect the internal volume of the enclosure, but does it have consequences on the cabinet resonance?

- One of the diffractor cones on the tweeter is missing. Is it possible to reconstruct it using a 3D printer? What are the key points to watch out for?

thanks for help.

Geluidloopt · 2024-01-15 9:44 pm

Selling 2 x Tamura VL-SS inductors, NIB

These were built/developed by Tamura for Susumu Sakuma (hence the name) to be used in his phono/EQ amplifiers as a replacement for the VL-208, VL-209 and VL-210 he had been previously using. Taps for 1.1H, 3H and 7H, permalloy core

Asking 500€/each or 800€/pair, will ship worldwide

Geluidloopt · 2024-12-03 12:07 pm

Selling a PEL Audio DAC

Great sounding DAC, built by Cees Pel in a beautiful wooden Musical Affairs enclosure.
This is the last model he built, and it is capable of 24/96khz (compared to 16/44 of all the other models) on spdif.

Inside, it has big Western Electric output capacitors and wiring, Audio Note Tantalum resistors and Elna Silmic capacitors. Connectors are Furutech.

Asking 1000€, incl worldwide shipping

goodguys · 2025-01-02 8:58 am

New. Dali Rubicon 2 in walnut. Excellent speaker. Excellent reviews. Pick up welcome from west yorkshire, or i can ship. Please contact for insured shipping. UK only. £850
I have no demo facilities but you can pay by paypal to protect your purchase

RM · 2024-12-31 10:32 am

I have 50 pairs of these high voltage transistors. Wonderful for repairing high power amps.

Due to age constraints I’m not doing much repair work, I’m focusing on building my own stuff.

Minimum 10pairs, although I prefer to sell all at once.

€13/pair. Shipping at cost.

R

lene · 2024-12-26 7:30 am

Hello there.

I've read in a few different posts how by adding a resistance to oppose a driver movement it can be used as a PR.

When I simulate a box with a PR I can add grams.

Is there a formula to get the equivalent in grams that I would get by adding a resistance to a driver?

Best regards.

locky_z · 2012-02-01 7:44 am

This version use USB or RS232 interface communication with PC.
It can measure BJT's Ic->Hfe curve

Can measure Vce-Ic curve

measure some semiconductor transmission curve,such as Vbe-Ic / Vgs-Id

also FET’s Vds-Id curve measure,Even can study Vgs & Rds relationship

Upper is six IRF630 Vds-Id curves,their Vgs is 5V 6V 7V 8V 9V 10V.
The Vds-Id curve only show Vds=0~1V range,so you can use system’s calculate function get the slope value,
The window in the central show six curve’s slope, Measurement unit is V/mA, multiplicate 1000 is Rds,
So under Vgs=10V,Rds is 0.000334649870637804*1000=0.334ohm

Some diode V->I curve

fllower is TL431 in all current range V-I curve

if you plug TL431 into socket B and E,and change the measure condition,you can see less current VI curve. The following figure , Y-axis is only 0~0.38mA

the Intelligent Curve Tracer is more powerful,It can measure 3 terminal voltage regulator’s Vi-Vo / Io->Vo Curve

eldarvanyar · 2024-12-25 9:21 pm

Hi All, I have bought some Kemet C878BF35460SA0J motor run capacitors for use in my RH84 V2 psu. It has four connectors and I am not sure how to connect it.

Can you tell me how to wire this capacitor? Is their a connector that I can order to make it easier or do I just soldier the connectors?
Also do I have to connect the bolt at the end to earth as it has an earth symbol.

Thanks

valvemaniacuk · 2021-04-18 1:20 pm

Hi All,

Some of you may have been following an interesting thread in which Ralph Karsten of Atma-sphere fame graciously offered the schematic of an early version of the M-60 amplifier, which a number of forum members have built and are happily using. See thread link below -

What tubes for a OTL tube amp?

Thoughts have now turned to a matching pre-amp. As Ralph himself has stated, as the power amp is a differential design, it would make sense to use that advantage with a differential pre-amp. It would, of course, be unreasonable of us to ask Ralph if he would be willing to share a schematic of an early MP-3, (although we have, of course asked, 😀) but he has explained the concept behind the MP-3 circuitry, and with a little thought and input from forum members we should hopefully be able to put together something very close to the real thing.

Ralph's comments are below -

The circuit is very similar to the M-60 but uses a straight differential amplifier driving the grids of the output tube which is a 6SN7 rather than a power tube. Because its easier to drive no driver tube is needed. We usually run the Circlotron supplies at about 120V at their outputs. A servo is used to detect DC Offset at the output XLRs. One of the grids of the 6SN7 is tied thru a 1M resistor to a simple divider network so that the tube is biased at about -1.7V. The output of the servo ties to the other grid thru another 1M resistor and there is a bit of capacitance at the point where that ties to the divider network or output of the servo, to prevent modulation of the network by actual audio.
This is probably a topic for another thread. But this circuit is arguably as transparent as you'll ever get using tubes, with extreme bandwidth too. The main advantage is that no enormous output coupling cap; instead the Circlotron acts as a buffer so the actual coupling caps can be much smaller. The smaller you make the cap the less inductance and other problems it has so it can be more neutral.

So, the gauntlet has been laid down and the proverbial carrot well and truly dangled.

The problem I personally have is that whilst I can use a soldering iron, and can happily read a schematic, I do not have the design skills to interpret Ralph's comments into a workable design. Hopefully however, there are plenty of forum members who can, and so the plan is to develop the design into a workable solution that can be built by forum members who are interested in this type of circuit topology. If there is sufficient interest, then hopefully a group buy of pcb's could be organised.

As a starting point, I have added below the circuit diagram for the DIY Audio version of the M-60 that I am currently building, plus a concept schematic of a pre-amp based on Ralph's comments above.

I fully accept that the schematic is almost certainly not workable in its current form, but hopefully this can be developed into a suitable design. Please feel free to comment and adjust as required. One of the great benefits of this hobby for me is that it gives me the opportunity to learn. So happy to co-ordinate reply's and modify the design to suit.

So. . .
V1 is a 12AU7
V2 is a 6SN7
This will only be the line stage at the moment.
Although the MP-3 is a fully differential design, have only spec'd a single ended input, (as most people will probably not be able to make use of a fully balanced input) but this can of course easily be modified by adding the second input into V1B
R5 could be changed for a CCS, although I don't think Ralph uses one.
R6 and R7 are the voltage divider that Ralph mentions for the -1.7V bias voltage on the output tubes.

So thoughts please. Hopefully Ralph will also add in a few comments as we go.

Cheers,

Steve.

thebestofall007 · 2024-12-13 11:28 pm

Hi all in this awesome forum. I was wondering if anyone has a schematic or service manual for a Memphis Audio prx700.5 5-channel amplifier? I am trying to repair the subwoofer output channel that is outputting 41v DC (!) at the speaker out. I suspect that it could be a shorted subwoofer output transistor that is allowing the full rail voltage (either positive or negative) through. I have no idea what ones are the subwoofer's transistors, though. The four remaining front/rear channels are labelled on the pcb, but not the sub's.

chrisg4 · 2025-01-01 11:51 am

Hi all,

I have previously repaired this amplifier. The output inductors are running extremely hot to the point the amp shuts down. Does anyone know the spec of the inductors.
I have measured the inductors with my LCR.

Inductor 1 : 1.6ohm ; 0.07mH (70uH)
Inductor 2 : 1.4ohm ; 0.07mH(70uH)

are these values correct or out of spec.

NagysAudio · 2009-11-06 8:40 pm

Fellow diyAudio Members,

I know there are many users out there who have broken Goldmund equipment and need the A1 modules to complete the repairs. Goldmund no longer sells these modules and they are virtually impossible to find on the market. I'm planning to run a batch and would like to see if any of you would be interested before I invest in this project.

These modules will use all ORIGINAL Goldmund parts and schematic and will fit in the existing sockets. The only difference is the potting. Goldmund potted their modules to keep the input stage a top secret, I will not pot them.

I am planning on selling them at $150 each.

Here are some Goldmund products that use the A1 modules:

Mimesis 6
Mimesis 6.2
Mimesis 3
Mimesis 2
Mimesis 7
Mimesis 7.1
Mimesis 9
SRI

Thanks!

tt8 · 2025-01-01 1:36 pm

I'm trying to make an A1 module myself to repair my phono stage PH-01.

chipper · 2025-01-02 3:11 am

Hey guys I am trying to troubleshoot a punch 801S the issue is no audio output powers up but has no sound on either channel. What are the four TL07C’s duty? Could a defective one be responsible for no audio output. I’ve used a similar RF amp to compare readings everything looks similar…

JamfiTX · 2025-01-01 8:49 pm

Hello.
I'm Jani. I live in Slovakia. I speak Hungarian, Slovak and Czech. And a little English. I'm 38 years old. I'm a truck and bus driver. I'm interested in every little part of hi-fi. I have a Creek and a Nuforce amplifier, and Magnat and Jamo speakers. I like all genres of music, especially if it's good.
Apart from that, I'm a fun, funny guy, and mostly calm.
My only drugs are music and hi-fi.
That's about it. 👍😏😀🙃

erikovsky · 2017-03-05 1:37 am

Hi all,

It's 2017 now. I am trying to make a Goldmund wiki that collects information I got from the internet. I hope this will be a great review for new builders.

***2017/09/07***
Reference schematic available!
http://www.diyaudio.com/forums/attachment.php?attachmentid=633063&d=1504260890

*****Kept updating*******
2017/3/17 Google site ON AIR!
Goldmund 2017

VAS:

2n5564/NPD5564 no significant difference

Output:

10N20/10P20 from Exicon is far more better than 2SK1058/J162, more punchy bass.

**********

"The Telos basically same as Mimesis, except some points:
- LTP Iq is higher, same 4.3mA. The 6V zener of Mimesis instead by LM329 precision low noise 6.9V zener.
- VAS Iq a bit smaller, same 7.8mA for both sides. VAS devices are Zetex transistors, FZT957/FZT857 SOT 223 SMD.
- Individual driver (MJE340/MJE350, but they're KSC2690A/KSA1220A for Telos 5000) for each MOSFET output pair(Exicon ECX10N20/10P20). There are six pairs output per channel.*
Based on this info, you can transform Mimesis to Telos."

JeffPNW · 2024-12-27 11:26 pm

I have been spending quite a bit of time trying to understand transmission lines, and have really been trying to come to grips with the prevailing thought of cross sectional area doesn't matter. I absolutely am raising this question not to troll or try to poke holes, because clearly folks are designing good systems using the suite of available tools (akabad, spicytl, etc.). Of course there is Comsol, but for most of us, this is way too expensive.

My son sent me a book on the physics of musical instruments (Fletcher and Rossling), and there is a section describing the harmonics of pipes and cones. According to them, there are cutoff dimensions for the various harmonic modes (they highlight 4 in a cylindrical world), the cutoff for these ranges from 1.84 c/a to about 3.5 c/a. (c=speed of sound, a=area). My gut analysis says that we are above these cutoff regions in most TLs for most frequencies.

Additionally, whilst I see discussion on tapering vs straight lines in terms of the length of the line, I don't see explicitly this being used to target the various impedance ranges. (Or at least how I understand it). (see attached screenshots)

It has taken me a while to understand this whole impedance matching thing, or at least telling myself that I understood things.

I am limited in my options since I am on a mac, but I have redusted off spicytl, and have been trying to have responses match what is predicted by theory (and some very complicated math), and I don't see these happening. In fact, @planet10 , who knows more on this than I ever will on this, specifically told me Sd doesn't matter. And he has real world experience.

And, I notice that a "typical" approach is to stuff the line until it "sounds" good. And, some results are truly amazing. Others (such as I would probably design) might look good on paper (aka., modeling), but maybe not so good in real life.

I am curious about the tweaking, since I do see a gap between the physics and the model, and do not know enough to know the limits. But when I look at the graphs I see how area and taper rate should very much affect impedance. In fact, tapered lines should have more impedance peaks than straight?

So to my question:

When modifying the TLs, are people also measuring the driver impedance response across the frequency range in the TL, and using this to tune, or are people using the acoustic response, which also includes the baffle?

Patrick Bateman · 2019-10-10 12:54 am

Last Saturday, Joe Rogan did an interesting podcast about a Navy flyer who filmed a UFO over San Diego. (YouTube)

As you've seen with some of my posts, my idea of fun is reading Tom Danley's patents and trying to figure out how to reverse engineer them. (https://www.diyaudio.com/forums/multi-way/217298-square-pegs.html)

Danley used to be on the Art Bell show occasionally, and I was a big fan. (The Great Pyramid Tunnel Mistery)

The Danley Unity Horn was inspired by some of those discussions. (https://www.diyaudio.com/forums/pa-systems/197713-disappointing-stadium-sound-post2790598.html)

Probably my favorite guest on the Art Bell show was Bob Lazar. (YouTube)

It appears that the U.S. Navy has declassified the technology that Lazar described thirty years ago, so I thought I'd take a crack at deciphering the patent.

So here we go... Gravitational Waveguides.

Here's the illustration from the Navy patent

Using said illustration, I made a 3D model, so I could better visualize how the craft works

Here's the craft in flight, as discussed on the Rogan show last Saturday

2024-02-29 4:41 am

I am just a starter in guitar amp design and need to know what are the requirements. To say the truth I am not any musician. I looked on youtube and most serious study of the subject is this.
Login to view embedded media It shows all the myths developed about the guitar tone but I remain with more questions than answers. What I think for sure, the sound of the paper of the speaker plays the major importance, as the harmonic table of an acoustic guitar or of violin does. How really the sound of an amp plays any role?

Patrick Bateman · 2025-01-01 10:11 pm

I've read the manual, I've read the tutorial at HTGuide, I've tried to find an answer here.

How do I get VituixCad to plot from zero to 180 degrees in stead of 0-45 or 0-90?

I have attached an example of what I mean, from a post by @tmuikku
He helped me out last night but I don't want to keep bugging the same person so I thought I'd ask the forum 🙂

The second attachment shows what I see on my installation of VituixCad.

The thing that's strange is that my FRD files definitely go out to a full 180 degrees. So, I have the DATA, I just can't figure out how to convince VituixCad to plot the data out to 180 degrees.

Beamer1707 · 2025-01-01 3:29 pm

2002 Mustang GT that I just put a system in and I'm looking for some insight.

cafemax · 2025-01-01 8:14 am

Hello,

I’m from Taiwan and a DIY audio enthusiast... though I haven’t been building much lately.

However, to finally complete a few projects that have been sitting in storage for ages, I’ve decided to put in some effort.

This is my New Year’s resolution for 2025. 😛

blewa · 2024-12-31 7:35 pm

Hi all,
Just introducing myself. I've recently gotten into speaker building and home audio again after being interested in car audio my late teens and early 20s. My first full range project is going to be a center channel based around the Satori MT19CP-8 Coaxial driver, with full range front stage towers to follow. I'll start a build thread for these in the future once I start building the cabinets.

Cheers!

robthomp · 2021-02-15 6:20 pm

I'm building a stereo ACA, one chassis, two amp boards, one for each channel, with a linear power supply. I have a 300VA 2x20 toroidal transformer from Antek, and I'm planning to use a CRC filter. It seems to me that there are two options and I'm wondering if one is preferable to the other, what the pros and cons might be, or whether it makes any difference:

Option One: build a single power supply with one bridge rectifier and CRC filter, fed by the two secondaries in parallel, and feed both channels from this power supply.

Option Two: build two power supplies, each with a bridge rectifier + CRC filter, and feed one with one pair of secondary wires, feed the other with the other pair. One power supply would be for left channel, one for right. The two power supplies would be side by side on the same pcb.

It appears to me that option Two is used by the FirstWatt F1 amp, which has a single rail supply like the ACA. Other FirstWatt amps have one supply shared by both channels as in option One, but it isn't a good comparison because they have dual rail supplies, hence use two bridge rectifiers and two CRC filters, each fed by one pair of secondaries.

Also, some toroidal transformer manufacturers specify that the two pairs of secondaries are only to be used in series or parallel, and not independently, although Antek doesn't seem to give that warning. I read some posts about this issue, I guess it has to do with the amount of insulation separating the two secondary pairs, but I'm still unclear on just when that would be okay to do. Evidently it's not an issue for the F1.

Randy Bassinga · 2024-12-10 11:10 am

This is the racetrack 8" driver that I introduced in the Bass Shelter thread. It is an unbranded driver sold as a replacement for a name brand boombox. It's 130mm slim across the narrow, and I can think of some fun applications if the driver is good. Build quality is visually superior to Dayton Reference passive radiators on hand. The driver is sold on Ali and is fairly expensive at $104 AUD for a no name. It's proportions and the promise of a decent 40hz low end as touted by the name brand makes it interesting enough to take a punt on. It will also suit the intended beach environment

Comes very well-packed

On the Datsv3, driver not yet broken in

Will stick to plan and take power from the sub section of the current Logitech z623 for breaking in and initial listening. The driver doesn't come with radius info for the cutout, so I will have to do some trial and error to get it right. It does come with a template so I can hack out a cutout for breaking in purpose

Will use the laser cutter CNC router thingy to get the cutout and recess just right for a proper cab in due time. The driver also appears to require a dress trim. The screw holes are very close to the edge of the rubber roll surround glue line. I hate the idea of screw heads crushing this. What do you guys do in this situation? The best I can think of is an alloy plate dress ring in CNC and with matching screw holes to clamp down over the driver's folded up edge. Mounting from behind the baffle will solve this too and have the same clamping effect. Actually, this may not be a bad thing and the material thickness can contain the excursion and just allow a simple grill over the driver

Welcome your thoughts on this unit

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