Help with noise in tube amp EL34A
- By carlthess40
- Tubes / Valves
- 7 Replies
Hello
I need some help with a Chinese tube amp that I’m using for one of my turntable setups
It’s a el34A type amp
When nothing is playing, I hear soMe noise in my speakers, it does not sound like a 60hz buzz, or I don’t think it is. I just tried some other tubes in it and still has the same noise
I have meters and a scope, not very handy with my scope, have it for setups input gain for car amps.
What steps and how do I accomplish these steps to track down the source of this noise.
Also one other problem I’m having is that the left speaker channel is not as loud as the right channel. And it’s the same no matter if I’m playing the turntable or cd inputs.
Here’s a photo of the amp, later today I’ll flip it over and remove the bottom plate and take photos of the inside
Thanks for any and all help
P.S. I’m a newbie with doing this type of stuff so please try to dump it down for me lol
I need some help with a Chinese tube amp that I’m using for one of my turntable setups
It’s a el34A type amp
When nothing is playing, I hear soMe noise in my speakers, it does not sound like a 60hz buzz, or I don’t think it is. I just tried some other tubes in it and still has the same noise
I have meters and a scope, not very handy with my scope, have it for setups input gain for car amps.
What steps and how do I accomplish these steps to track down the source of this noise.
Also one other problem I’m having is that the left speaker channel is not as loud as the right channel. And it’s the same no matter if I’m playing the turntable or cd inputs.
Here’s a photo of the amp, later today I’ll flip it over and remove the bottom plate and take photos of the inside
Thanks for any and all help
P.S. I’m a newbie with doing this type of stuff so please try to dump it down for me lol
A newbie guide into cheap Class D boards
I decided to start this after I bought a cheap tda7492 board that sounds not so good, and the info on modding it and component selection was scattered all around, so I picked it up and compiled the usefull knowledge here.
Please, read all before doing anything to your board, and specially go trough step 4 before changing components at the output.
All that info apply to Class D without feedback, please refer to the datasheet of your module and make sure you dont change anything out of specs. The most relevant references are here:
Trevor's blog little class D tuto
Texas Instruments notes
Texas's output filter calculator
EETimes article
Maxim Itegrated aaplication note on types of caps for audio
Your module/chip datasheet (this one is your job, go find it)
First, there may be 4 probable fonts of unwanted hum, hiss or noise in your board
1 bad quality components
2 bad signal input
3 bad ground connections
4 bad output filter
1 Lets start by the most common, the nightmare of audiophiles, bad quality capacitors!
These little guys can mess with everything you want, on the maxim note they explain that. TL/DR chinese use cheap X7R ceramic caps, cheap and small, but they act like a piezo element, when voltage is applied they deform, change capacitance, and resonate with the circuit, you don't want nothing resonating, you just want you audio signal.
If you see small light brown smd caps they're probably X7R, if they are on audio paths, it'd be good to change for some multilayer polymer dieletric (polyester, mylar, polycarbonate, polyestirene) or to NP0 caps, since they dont give a **** about voltage, temperature or current variation, and they have reasonably low esr. DON'T use electrolitic caps here, they have HIGH esr, so they are most suited for storing energy than signal conitioning.
2 Second, if you have bad audio input, you'll have bad audio output, amps don't do magic. Make sure you have a matching input, if your amp is single ended, use single ended signal, and so on.
Make sure you have good coupling caps at your input. Coupling caps are in series with the input conector and the chip input, if they are X7R, make sure to change them, the datasheet of the board or the chip can suggest good values to use.
If you have a buffer(little amp with no gain, in level=out level, used to match impedance) make sure that it's a good one by reading the chip datasheet, if you're not sure, ask for help at the forum on if its ok to leave and if not how to mod it.
When you can, use differential input, it will sound better since it dont have ground connection, gnd usually carry heavy noise caused by the fast switching output.
3 Here we are, this one is a bit complicated, please do some research on "ground plane pcb desing" and "star connected ground".
Since everything that's referenced to ground have to be connected to it, including the output supply, they will probably share the same noise, and output stage on Class D cause a hell of a noise, so watch your connections carefully, this can be mitigated by some clever path designing, but I'm not the most suited to teach ou this.
4 The baddest of all, poorly designed output filter.
The output filter work by getting rid of the switching carrier frequency, so you get only the audio that was superimposed at the modulation stage. A filter is an association of capacitors and inductors/coils, and think what also have a coil inside? Yes, your speaker. So an output filter need to be designed to match the speaker you will use. It can be done with some room for change, like design it for 5 ohms, so it work with both 4 ohms and 6 ohms.
But, chinese manufacturers usually use what they want, and usually they want you to use 8 ohms or higher.
Output filters have a quality factor, that tells you how good it is filtering. For a given filter, you'll have a linear response till the cut frequency, that for class D is usually 22-40 KHz, and then a sudden step down in response. If you change the speaker, you change a bit of the filter inductance, so you change your filter caracteristics. Usually, by increasing speaker impedance you increase qualitiy factor, good right?
High quality factor will give you a stepper response at the cut out frequency, but will give a huge spike right below it, so if your filter has a high Q, and cut frequency at 22KHz, you will see harsh threbble cause of the huge spike near cut out frequency.
Lower Q will give you a smooth roll off, that happen by reducing speaker's impedance, so youl get poor performance at high frequencies.
Texas Instrument has given us an excel sheet that do all the heavy calculation, just look at you board and insert the values here, then see what happens, and play with them a bit.
Here's mine stock components calculations:
Interesting to note: Even if these boards should perform poorly with treble at lower impedances, the effects of X7R caps give it a nasty harsh sound.
After some tweaking for my 4ohm speaker:
Besides all that, they tend to use the cheapest coils and caps they have. The caps where already adressed, but the inductors play a key role here.
The inductor have a max current at wich they still work as an inductor, after it the losses increase at an incredible rate. So if you want to dry out every single watt of your amp, take in consideration the DC current that can pass trough the coil, so use a coil that can endure that. A rule of thumb is that more current = denser magnetic field, and core material have a limited capacity of magnetic fiel for a given core area(pls dont correct me on these terms, they're for sake of understanding, not for technical specs), so if you want a bigger current, use a coil with bigger core area, and the same value of inductance.
Core material should be ferrite/ceramic, since we're talking abou high frequency, 250-400Khz.
After you've checked all that above, you can look at your board and try to extract the schematic of the amp, principally the filter, and compare it to the seggested topology of the datasheet, if you see some diversion, it'd be good to correct it, like, some boards lack a snubber, a device that supresses transients and prevent your amp from being a radio antenna, it is a resistor in series with a little cap, conected between the amp outputs, before the filter.
I, like most of you, dont have a setup for complex measurements here, but if you've done it right, now you should have a good sound board, some people, like Trevor, even use those on HiFi setups.
Please, read all before doing anything to your board, and specially go trough step 4 before changing components at the output.
All that info apply to Class D without feedback, please refer to the datasheet of your module and make sure you dont change anything out of specs. The most relevant references are here:
Trevor's blog little class D tuto
Texas Instruments notes
Texas's output filter calculator
EETimes article
Maxim Itegrated aaplication note on types of caps for audio
Your module/chip datasheet (this one is your job, go find it)
First, there may be 4 probable fonts of unwanted hum, hiss or noise in your board
1 bad quality components
2 bad signal input
3 bad ground connections
4 bad output filter
1 Lets start by the most common, the nightmare of audiophiles, bad quality capacitors!
These little guys can mess with everything you want, on the maxim note they explain that. TL/DR chinese use cheap X7R ceramic caps, cheap and small, but they act like a piezo element, when voltage is applied they deform, change capacitance, and resonate with the circuit, you don't want nothing resonating, you just want you audio signal.
If you see small light brown smd caps they're probably X7R, if they are on audio paths, it'd be good to change for some multilayer polymer dieletric (polyester, mylar, polycarbonate, polyestirene) or to NP0 caps, since they dont give a **** about voltage, temperature or current variation, and they have reasonably low esr. DON'T use electrolitic caps here, they have HIGH esr, so they are most suited for storing energy than signal conitioning.
2 Second, if you have bad audio input, you'll have bad audio output, amps don't do magic. Make sure you have a matching input, if your amp is single ended, use single ended signal, and so on.
Make sure you have good coupling caps at your input. Coupling caps are in series with the input conector and the chip input, if they are X7R, make sure to change them, the datasheet of the board or the chip can suggest good values to use.
If you have a buffer(little amp with no gain, in level=out level, used to match impedance) make sure that it's a good one by reading the chip datasheet, if you're not sure, ask for help at the forum on if its ok to leave and if not how to mod it.
When you can, use differential input, it will sound better since it dont have ground connection, gnd usually carry heavy noise caused by the fast switching output.
3 Here we are, this one is a bit complicated, please do some research on "ground plane pcb desing" and "star connected ground".
Since everything that's referenced to ground have to be connected to it, including the output supply, they will probably share the same noise, and output stage on Class D cause a hell of a noise, so watch your connections carefully, this can be mitigated by some clever path designing, but I'm not the most suited to teach ou this.
4 The baddest of all, poorly designed output filter.
The output filter work by getting rid of the switching carrier frequency, so you get only the audio that was superimposed at the modulation stage. A filter is an association of capacitors and inductors/coils, and think what also have a coil inside? Yes, your speaker. So an output filter need to be designed to match the speaker you will use. It can be done with some room for change, like design it for 5 ohms, so it work with both 4 ohms and 6 ohms.
But, chinese manufacturers usually use what they want, and usually they want you to use 8 ohms or higher.
Output filters have a quality factor, that tells you how good it is filtering. For a given filter, you'll have a linear response till the cut frequency, that for class D is usually 22-40 KHz, and then a sudden step down in response. If you change the speaker, you change a bit of the filter inductance, so you change your filter caracteristics. Usually, by increasing speaker impedance you increase qualitiy factor, good right?
High quality factor will give you a stepper response at the cut out frequency, but will give a huge spike right below it, so if your filter has a high Q, and cut frequency at 22KHz, you will see harsh threbble cause of the huge spike near cut out frequency.
Lower Q will give you a smooth roll off, that happen by reducing speaker's impedance, so youl get poor performance at high frequencies.
Texas Instrument has given us an excel sheet that do all the heavy calculation, just look at you board and insert the values here, then see what happens, and play with them a bit.
Here's mine stock components calculations:
After some tweaking for my 4ohm speaker:
Besides all that, they tend to use the cheapest coils and caps they have. The caps where already adressed, but the inductors play a key role here.
The inductor have a max current at wich they still work as an inductor, after it the losses increase at an incredible rate. So if you want to dry out every single watt of your amp, take in consideration the DC current that can pass trough the coil, so use a coil that can endure that. A rule of thumb is that more current = denser magnetic field, and core material have a limited capacity of magnetic fiel for a given core area(pls dont correct me on these terms, they're for sake of understanding, not for technical specs), so if you want a bigger current, use a coil with bigger core area, and the same value of inductance.
Core material should be ferrite/ceramic, since we're talking abou high frequency, 250-400Khz.
After you've checked all that above, you can look at your board and try to extract the schematic of the amp, principally the filter, and compare it to the seggested topology of the datasheet, if you see some diversion, it'd be good to correct it, like, some boards lack a snubber, a device that supresses transients and prevent your amp from being a radio antenna, it is a resistor in series with a little cap, conected between the amp outputs, before the filter.
I, like most of you, dont have a setup for complex measurements here, but if you've done it right, now you should have a good sound board, some people, like Trevor, even use those on HiFi setups.
Attachments
Plate Resistor?
- By WntrMute2
- Tubes / Valves
- 27 Replies
I am building a pre-amp that I want to allow changing between two different B+ voltages with the change of the 2 VR tubes. I need to also change the 4 plate resistors from 47K to 33K and I'd like to do that without opening the chassis. Can I switch in a parallel resistor, as illustrated, without loss of fidelity?
I believe my calculation is correct but I'll double check before building.
[/IMG]
I believe my calculation is correct but I'll double check before building.
Dibya’s TDA7293 Xmas amp by Jhofland - Giveaway
This thread is to organize the logistics of the subject amplifier PCB giveaway. Technical details of the amp can be found here:
Xmas Amp - Dibya's TDA7293 by Jhofland
For technical discussions please use the other thread (above link).
Schematics here:
https://www.diyaudio.com/forums/att...7293-jhofland-tda7293_-schematic_12_06_20-pdf
Photo of actual PCB:
The amp has been fully tested and verified by Vunce and myself. We have a few minor edits for Jhofland to include in the final layout. The full amp schematics, BOM, and Gerber files are freely available for anyone to make their own boards. But this thread is for those who signed up in the other thread to get a free board for the cost of shipping.
Vunce’s verification build:
My verification build:
Closeup of the assembled boards:
Edit Jan 18, 2021: Latest measurements show that this amp has excellent performance with low THD and a natural non-fatiguing harmonic distortion proifile. Here is a loud playing 6.4Wrms into 10ohms:
Very loud 40Wrms into 10ohms:
It’s a great sounding amp! Easy to build and works very well. I recommend either 200VA to 250VA 25v trafo (either dual secondaries or center tap) or dual mono 100VA to 200VA 25v trafos. Nominal voltage is +/-35v and as high as +/-37v for design as presented with LM317/337L regulators. For 50v rails, use the zener diode mod in the other thread and big heatsink. The +/-15v voltages are needed for the DC servo.
To keep things simple, folks who are on the current list will send the shipping funds via PayPal and please include your DIYA screen name and your shipping address name and address in the PayPal payment. To keep things simple I will use a fixed shipping costs as follows.
Amounts are in USD and covers cost of PayPal fees, bubble padded mailer envelopes, and shipping labels. Cost for shipping will be $5 in USA, $8 in Canada, and $15 everywhere else. Boards will be sent via USPS First Class mail. No tracking and no insurance to keep costs low. As I have mentioned, you can also download the Gerbers linked in other thread and have your own boards made for not much money if you don’t want to participate in the giveaway.
I will compare your DIYA screen name in the PayPal payment to the list below to track the number of people. I am giving away 25 sets of two boards, they will be 1.6mm thick with 2oz copper and green solder mask.
Please send your PayPal funds to my address at xrk971 “at” rfasystems “dot” com.
Don’t forget to include your screen name and address.
Thanks, and happy belated Xmas and New Year!
A big thanks to Dibya for the inspiration and original design features and thanks to Jhofland for the final design and layout. Big thanks to Vunce for verifying the build.
Here is the current giveaway list:
Xmas Amp - Dibya's TDA7293 by Jhofland
For technical discussions please use the other thread (above link).
Schematics here:
https://www.diyaudio.com/forums/att...7293-jhofland-tda7293_-schematic_12_06_20-pdf
Photo of actual PCB:
The amp has been fully tested and verified by Vunce and myself. We have a few minor edits for Jhofland to include in the final layout. The full amp schematics, BOM, and Gerber files are freely available for anyone to make their own boards. But this thread is for those who signed up in the other thread to get a free board for the cost of shipping.
Vunce’s verification build:
My verification build:
Closeup of the assembled boards:
Edit Jan 18, 2021: Latest measurements show that this amp has excellent performance with low THD and a natural non-fatiguing harmonic distortion proifile. Here is a loud playing 6.4Wrms into 10ohms:
Very loud 40Wrms into 10ohms:
It’s a great sounding amp! Easy to build and works very well. I recommend either 200VA to 250VA 25v trafo (either dual secondaries or center tap) or dual mono 100VA to 200VA 25v trafos. Nominal voltage is +/-35v and as high as +/-37v for design as presented with LM317/337L regulators. For 50v rails, use the zener diode mod in the other thread and big heatsink. The +/-15v voltages are needed for the DC servo.
To keep things simple, folks who are on the current list will send the shipping funds via PayPal and please include your DIYA screen name and your shipping address name and address in the PayPal payment. To keep things simple I will use a fixed shipping costs as follows.
Amounts are in USD and covers cost of PayPal fees, bubble padded mailer envelopes, and shipping labels. Cost for shipping will be $5 in USA, $8 in Canada, and $15 everywhere else. Boards will be sent via USPS First Class mail. No tracking and no insurance to keep costs low. As I have mentioned, you can also download the Gerbers linked in other thread and have your own boards made for not much money if you don’t want to participate in the giveaway.
I will compare your DIYA screen name in the PayPal payment to the list below to track the number of people. I am giving away 25 sets of two boards, they will be 1.6mm thick with 2oz copper and green solder mask.
Please send your PayPal funds to my address at xrk971 “at” rfasystems “dot” com.
Don’t forget to include your screen name and address.
Thanks, and happy belated Xmas and New Year!
A big thanks to Dibya for the inspiration and original design features and thanks to Jhofland for the final design and layout. Big thanks to Vunce for verifying the build.
Here is the current giveaway list:
Attachments
AT2380v2 2Ch Digitally controlled Stepped Attenuator
- By Frex
- Group Buys
- 62 Replies
Frex The 26/11/2017
AT2380v2 Dual Channel Digitally controlled stepped attenuator Group-Buy
The dedicated thread of the project on DIYaudio is here :
AT2380v1 // 2 Channels digitally controlled stepped attenuator
Project description :
----------------------------
The AT2380 is a dual channels digitally controlled passive stepped attenuator.
It can be used to reduce the signal level in order to fit with the range of the target device.
It has been designed to doesn’t introduce any significant distortion and noise by using fully
passive attenuation network with high performance resistors.
There is NO active parts in the signal path.
To avoid any noise contamination from all on-board digital control circuitry,
all clocks can be disable keeping the attenuator to it’s current state (frizzed value).
One of the main purpose of this attenuator is to help performing signals measurements
(when testing audio devices for example) with analysis hardware such an audio sound-card.
Anyway, it can be of course used for any purpose where signal level control is needed.
For ease of use, the attenuation setting is made by a single rotary encoder
and it’s value is displayed directly on a four digits seven-segment LEDs display.
In addition, if some optional parts are mounted, an auto-track mode is available.
The auto track mode allow user to select directly in dBV the desired
output voltage level wanted at the output of the attenuator. (servo control loop).
The entire design fit in an small aluminium enclosure and the PCB panel include the main
board and also front and rear panel already drilled and engraved.
So, there is no need to make any drilling to get a very clean and beautiful DIY instruments !
The key specs are :
----------------------------
Below, some pictures of the unit (the v1 prototype !) :
You can also show the attenator in situation in these two presentation videos :
AT2380 DIY 2 channels digitally controlled stepped attenuator- Introduction video Part 1/2
AT2380 DIY 2 channels digitally controlled stepped attenuator- Introduction video Part 2/2
Some documents are available below for download (30/11/2017 update) :
--------------------------------------------------------------------------
Group-buy organization :
------------------------------------
I open now a group buy for the BARE PCB of the AT2380v2 project.
It's a PCB panel including the 2 layers 100x160 main PCB and
the front and rear panels for the 1455 Hammond enclosure.
Panels are drilled with all holes and marking, they are also
part of shielding.
Bare PCB(v1) picture:
The minimum number of order required is 10.
If this quantity is reached, the price would be 30€ all included.
(Bare PCB, worldwide shipping in priority letter without insurance, and Paypal fees).
The price could be lowered if pre-order quantity is much higher(>20).
I provide two bom files, with and without tracking mode enabled.
These bom file can be imported directly in Mouser for fast and convenient
parts ordering.
All parts list are coming from Mouser, so ordering is easy and fast.
The total Mouser bom cost are (this day):
---------------------------------------------------------
AT2380v2 without track mode : 114€
AT2380v2 with track mode : 135€
This include all parts, enclosure and button.
(You just need to find a small translucent red Plexiglas for the 7 segments display).
(The bom cost doesn't include the PCB)
It is a pre-order list, i will ask for payment as soon minimum order is reached
If there is no sufficient pre-order, i will cancel the group-buy.
The group-buy is opened until 16 December 2017.
At this time, i will ask for payment to order PCB to manufacturer (PCBcart).
I provide to all PCB buyers a very complete design folder,
including many documents and the full CPLD code source (writed in VHDL).
(it can be tweaked if needed).
IMPORTANT NOTE : You need an USB-Blaster to load the CPLD firmware in the CPLD.
(You can find it for few €/$ on ebay or Aliexpress)
If you are interested to join the group-buy :
Send me a PM with your location (country) and the number of PCB required
or post a message and then i will edit the buyers list below :
Pre-order list for the AT2380v2 bare PCB's:
-----------------------------------------------------------
Pseudo--Qty-----Location (country) ---- Payment received -------------Letter sent ------------ Receipt acknowledge
Frex--------------------------1--------France-----------------Payment DONE
Jcga--------------------------1--------France-----------------Payment DONE---------------------------Shipped----------------Confirmed
jhenderson01075 -------1--------USA--------------------Payment DONE-----------------------------Shipped
CeeVee---------------------1--------Portugal---------------Payment DONE----------------------------Shipped----------------Confirmed
Duster1---------------------2--------Estonia-----------------Payment DONE---------------------------Shipped
hallodeletue---------------2--------Germany--------------Payment DONE----------------------------Shipped----------------Confirmed
_jan_ -----------------------2--------Germany---------------Payment DONE---------------------------Shipped
markus22ch --------------2--------Switzerland-----------Payment DONE----------------------------Shipped
diyaudnut------------------1-------USA----------------------Payment DONE---------------------------Shipped-------------------Confirmed
bk856er--------------------1--------USA---------------------Payment DONE---------------------------Shipped-------------------Confirmed
mkc--------------------------1--------Danemark-------------Payment DONE--------------------------Shipped
Emynet---------------------1------- Italy----------------------Payment DONE--------------------------Shipped
Demian---------------------2-------USA---------------------Payment DONE---------------------------Shipped
gazzagazza---------------1-------New Zealand---------Payment DONE----------------------------Shipped-------------------Confirmed
mlloyd1 --------------------2-------USA-----------------------Payment DONE-------------------------Shipped-------------------Confirmed
Techland-------------------2------ Germany-----------------Payment DONE--------------------------Shipped
BDL--------------------------1-------Romania----------------Payment DONE--------------------------Shipped-------------------Confirmed
Zigi---------------------------2-------Poland-------------------Payment DONE--------------------------Shipped
------------------------------------------------------
TOTAL Pre-order = 26
Good news, on 30/11, the minimum order is reached !
NOTE : because of a more bigger per-orders than expected,
the panel price goes down and will be 25€ instead of 30€.
(including shipping and Paypal fees).
The 16/12/2017 -- GROUP BUY IS NOW CLOSED.
All Paypal invoices has been been sent.
PCB manufacturing will be send as soon all payment done.
Payment status can be show on the above table.
UPDATE The 22/12/2017
All payments has been received, thanks to all.
The PCB order has been sent for manufacturing and will arrive in about 10 days.
I will post pictures as soon they are in my hands.
All letters will be send to all in stride.
Update the 30/12/2017
The four design files linked above has been updateded
according to first reales of design folder.
Update the 04/01/2018
Bare PCB are arrived this day.
Letters will be prepared for shipping
in next days.
Update the 08/01/2018
All letters has been shipped.
Please, inform me when it's in your hands 🙂
Frex
I hope that enjoy some DIYers 🙂
Frex
AT2380v2 Dual Channel Digitally controlled stepped attenuator Group-Buy
The dedicated thread of the project on DIYaudio is here :
AT2380v1 // 2 Channels digitally controlled stepped attenuator
Project description :
----------------------------
The AT2380 is a dual channels digitally controlled passive stepped attenuator.
It can be used to reduce the signal level in order to fit with the range of the target device.
It has been designed to doesn’t introduce any significant distortion and noise by using fully
passive attenuation network with high performance resistors.
There is NO active parts in the signal path.
To avoid any noise contamination from all on-board digital control circuitry,
all clocks can be disable keeping the attenuator to it’s current state (frizzed value).
One of the main purpose of this attenuator is to help performing signals measurements
(when testing audio devices for example) with analysis hardware such an audio sound-card.
Anyway, it can be of course used for any purpose where signal level control is needed.
For ease of use, the attenuation setting is made by a single rotary encoder
and it’s value is displayed directly on a four digits seven-segment LEDs display.
In addition, if some optional parts are mounted, an auto-track mode is available.
The auto track mode allow user to select directly in dBV the desired
output voltage level wanted at the output of the attenuator. (servo control loop).
The entire design fit in an small aluminium enclosure and the PCB panel include the main
board and also front and rear panel already drilled and engraved.
So, there is no need to make any drilling to get a very clean and beautiful DIY instruments !
The key specs are :
----------------------------
- full digital control (5M570 CPLD, VHDL coded).
- 2 pseudo isolated attenuators Channels
- Zin= 600 Ohms , Zout = ~ 0 to 300 Ohms (Can be modified if needed)
- Flat frequency response (± 0,05dB) from DC..1MHz
- 0 to 127,5 dB attenuation in 0,5 dB step (8 bits / 256 steps)
- Direct dB attenuation setting displayed on 4 digits seven segments LEDs.
- Five selectable dB steps : 0.5 ,1 , 3, 6 and 10 dB by encoder increment.
- Optional output level auto-tracking mode from +10 dBV to – 85 dBV (attenuation only) .
- Full internal clock enable switch, for ultra quiet operation mode (no spurious).
- Shielded design to improve RF performance and noise immunity .
- Low cost design and easy to find parts.
- 100x160mm PCB size, fit in Hammond 1455 series extruded aluminium enclosure.
- Front and rear panels are made in PCB with all holes drilled and with gold silkscreen.
- Through holes axial or SMD (1206) ladder attenuator resistors types.
Below, some pictures of the unit (the v1 prototype !) :
You can also show the attenator in situation in these two presentation videos :
AT2380 DIY 2 channels digitally controlled stepped attenuator- Introduction video Part 1/2
AT2380 DIY 2 channels digitally controlled stepped attenuator- Introduction video Part 2/2
Some documents are available below for download (30/11/2017 update) :
--------------------------------------------------------------------------
Group-buy organization :
------------------------------------
I open now a group buy for the BARE PCB of the AT2380v2 project.
It's a PCB panel including the 2 layers 100x160 main PCB and
the front and rear panels for the 1455 Hammond enclosure.
Panels are drilled with all holes and marking, they are also
part of shielding.
Bare PCB(v1) picture:
The minimum number of order required is 10.
If this quantity is reached, the price would be 30€ all included.
(Bare PCB, worldwide shipping in priority letter without insurance, and Paypal fees).
The price could be lowered if pre-order quantity is much higher(>20).
I provide two bom files, with and without tracking mode enabled.
These bom file can be imported directly in Mouser for fast and convenient
parts ordering.
All parts list are coming from Mouser, so ordering is easy and fast.
The total Mouser bom cost are (this day):
---------------------------------------------------------
AT2380v2 without track mode : 114€
AT2380v2 with track mode : 135€
This include all parts, enclosure and button.
(You just need to find a small translucent red Plexiglas for the 7 segments display).
(The bom cost doesn't include the PCB)
It is a pre-order list, i will ask for payment as soon minimum order is reached
If there is no sufficient pre-order, i will cancel the group-buy.
The group-buy is opened until 16 December 2017.
At this time, i will ask for payment to order PCB to manufacturer (PCBcart).
I provide to all PCB buyers a very complete design folder,
including many documents and the full CPLD code source (writed in VHDL).
(it can be tweaked if needed).
IMPORTANT NOTE : You need an USB-Blaster to load the CPLD firmware in the CPLD.
(You can find it for few €/$ on ebay or Aliexpress)
If you are interested to join the group-buy :
Send me a PM with your location (country) and the number of PCB required
or post a message and then i will edit the buyers list below :
Pre-order list for the AT2380v2 bare PCB's:
-----------------------------------------------------------
Pseudo--Qty-----Location (country) ---- Payment received -------------Letter sent ------------ Receipt acknowledge
Frex--------------------------1--------France-----------------Payment DONE
Jcga--------------------------1--------France-----------------Payment DONE---------------------------Shipped----------------Confirmed
jhenderson01075 -------1--------USA--------------------Payment DONE-----------------------------Shipped
CeeVee---------------------1--------Portugal---------------Payment DONE----------------------------Shipped----------------Confirmed
Duster1---------------------2--------Estonia-----------------Payment DONE---------------------------Shipped
hallodeletue---------------2--------Germany--------------Payment DONE----------------------------Shipped----------------Confirmed
_jan_ -----------------------2--------Germany---------------Payment DONE---------------------------Shipped
markus22ch --------------2--------Switzerland-----------Payment DONE----------------------------Shipped
diyaudnut------------------1-------USA----------------------Payment DONE---------------------------Shipped-------------------Confirmed
bk856er--------------------1--------USA---------------------Payment DONE---------------------------Shipped-------------------Confirmed
mkc--------------------------1--------Danemark-------------Payment DONE--------------------------Shipped
Emynet---------------------1------- Italy----------------------Payment DONE--------------------------Shipped
Demian---------------------2-------USA---------------------Payment DONE---------------------------Shipped
gazzagazza---------------1-------New Zealand---------Payment DONE----------------------------Shipped-------------------Confirmed
mlloyd1 --------------------2-------USA-----------------------Payment DONE-------------------------Shipped-------------------Confirmed
Techland-------------------2------ Germany-----------------Payment DONE--------------------------Shipped
BDL--------------------------1-------Romania----------------Payment DONE--------------------------Shipped-------------------Confirmed
Zigi---------------------------2-------Poland-------------------Payment DONE--------------------------Shipped
------------------------------------------------------
TOTAL Pre-order = 26
Good news, on 30/11, the minimum order is reached !
NOTE : because of a more bigger per-orders than expected,
the panel price goes down and will be 25€ instead of 30€.
(including shipping and Paypal fees).
The 16/12/2017 -- GROUP BUY IS NOW CLOSED.
All Paypal invoices has been been sent.
PCB manufacturing will be send as soon all payment done.
Payment status can be show on the above table.
UPDATE The 22/12/2017
All payments has been received, thanks to all.
The PCB order has been sent for manufacturing and will arrive in about 10 days.
I will post pictures as soon they are in my hands.
All letters will be send to all in stride.
Update the 30/12/2017
The four design files linked above has been updateded
according to first reales of design folder.
Update the 04/01/2018
Bare PCB are arrived this day.
Letters will be prepared for shipping
in next days.
Update the 08/01/2018
All letters has been shipped.
Please, inform me when it's in your hands 🙂
Frex
I hope that enjoy some DIYers 🙂
Frex
Better living room acoustic systems surpassed by headphones
- By academia50
- Room Acoustics & Mods
- 13 Replies
Attachments
Auna Linie 300 fix tweeter
I have recently acquired Auna Linie 300 5.1 speakers...
Central speaker came with a bad tweeter and they are bad quality anyway... But at first I thought it could be the way they were soldered and maybe bad cap, so today I desoldered it and tested directly however the tweeter was playing at much lower volume than the other speakers with the same exact tweeters, so I increased a bit more the volume and puff, it burned as I was testing without the cap however I was testing treble only sounds...
Central Speaker:
Bookshelf speakers: Same specs as central speakers above...
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
I want to buy the Dayton Audio TD20F Tweeter which is a cheap but pretty good tweeter
TD20F specs:
4 Ohms;
90.0 dB @ 2.83V/1m;
Frequency: 3Khz to 20Khz;
Resonant Frequency (Fs) 1696 Hz;
20W RMS, 40max with proper crossover;
Full Specs: Dayton Audio - TD20F-4 3/4" Soft Dome Neodymium Tweeter 4 Ohm
My questions:
♪-I would like to know what's the best frequency for the crossover between the woofer playing almost full range with the tweeter I mentioned above from Dayton Audio (Woofers with only low frequency cut on the amp at my chosen level and redirected to my subwoofer but no high frequency cut-off, direct connection);
♪- I'm planing to upgrade the center\front speakers all with Dayton Audio tweeters and continue with the original woofer directly connected to +- and just add a cap for the tweeter.
♪- original caps are 2.2uF 50V, what caps should I use for the Dayton Audio tweeter (will it be any good with the original caps?)?
Extra info (not important):
● And no, I don't plan to buy an actual good crossover for now because those are cheap speakers, maybe later if I also change the woofer I would be willing to apply proper crossover electronics with actual woofer max frequency cuttoff, for now just want to upgrade the tweeters the cheapest way as those are terrible while the rear speaker big towers are actually decent because they have better actual silk dome tweeters, so when playing games rear audio is much clear than front audio (also the big rear towers are ported and the front+center speakers are SEALED) so the rear also has better bass, but that will be fixed with higher frequency crossover for the woofers from the amp so that they lose a bit more bass.
● I'm still waiting for the receiver to arrive and for now I have those speakers connected to my Logitech Z5500 integrated amp with it's nice 10 inch subwoofer and I'm using 80hz crossover via software direct 5.1 from a kinda good old Auzentech sound card, but this amp has an internal non adjustable crossover which I don't known the frequency, but anyway when I get the receiver maybe I will put 90hz crossover for front+center and maybe 100 or 120hz for rear big tower speakers (and if they are still not much clear I could increase as I need mostly sound clarity for gaming and let the big subwoofer do all the huge kicks, explosions, rumble and shake all my windows😀).
Central speaker came with a bad tweeter and they are bad quality anyway... But at first I thought it could be the way they were soldered and maybe bad cap, so today I desoldered it and tested directly however the tweeter was playing at much lower volume than the other speakers with the same exact tweeters, so I increased a bit more the volume and puff, it burned as I was testing without the cap however I was testing treble only sounds...
Central Speaker:
- frequency range: 92Hz - 20kHz
- sensitivity: 87dB +-3dB
- 8 ohm
- max: 76 watts - 35W RMS
- speakers are sealed 2-way. The Woofer is directly connected to +- (No Crossover) and the tweeters only have a small 2.2 uF 50V cap and the crap tweeters are 4 ohms (3watt) and the woofers are 8ohms and all 5 speakers are 8 ohms at the end...
An externally hosted image should be here but it was not working when we last tested it.
Bookshelf speakers: Same specs as central speakers above...
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
I want to buy the Dayton Audio TD20F Tweeter which is a cheap but pretty good tweeter
TD20F specs:
4 Ohms;
90.0 dB @ 2.83V/1m;
Frequency: 3Khz to 20Khz;
Resonant Frequency (Fs) 1696 Hz;
20W RMS, 40max with proper crossover;
Full Specs: Dayton Audio - TD20F-4 3/4" Soft Dome Neodymium Tweeter 4 Ohm
My questions:
♪-I would like to know what's the best frequency for the crossover between the woofer playing almost full range with the tweeter I mentioned above from Dayton Audio (Woofers with only low frequency cut on the amp at my chosen level and redirected to my subwoofer but no high frequency cut-off, direct connection);
♪- I'm planing to upgrade the center\front speakers all with Dayton Audio tweeters and continue with the original woofer directly connected to +- and just add a cap for the tweeter.
♪- original caps are 2.2uF 50V, what caps should I use for the Dayton Audio tweeter (will it be any good with the original caps?)?
Extra info (not important):
● And no, I don't plan to buy an actual good crossover for now because those are cheap speakers, maybe later if I also change the woofer I would be willing to apply proper crossover electronics with actual woofer max frequency cuttoff, for now just want to upgrade the tweeters the cheapest way as those are terrible while the rear speaker big towers are actually decent because they have better actual silk dome tweeters, so when playing games rear audio is much clear than front audio (also the big rear towers are ported and the front+center speakers are SEALED) so the rear also has better bass, but that will be fixed with higher frequency crossover for the woofers from the amp so that they lose a bit more bass.
● I'm still waiting for the receiver to arrive and for now I have those speakers connected to my Logitech Z5500 integrated amp with it's nice 10 inch subwoofer and I'm using 80hz crossover via software direct 5.1 from a kinda good old Auzentech sound card, but this amp has an internal non adjustable crossover which I don't known the frequency, but anyway when I get the receiver maybe I will put 90hz crossover for front+center and maybe 100 or 120hz for rear big tower speakers (and if they are still not much clear I could increase as I need mostly sound clarity for gaming and let the big subwoofer do all the huge kicks, explosions, rumble and shake all my windows😀).
The tale of a single rail.. Is it possible?
- By zerokelvin99
- Class D
- 12 Replies
Hi all,
After many hours of internet searching and increasingly complex solutions being dreamed up, how would you achieve:
600w+ @4R powered by a 42v li-ion battery
The TPA3255 would be the logical choice upto 50V through a boost converter, as its an efficient & single rail device. Whilst also being simple to implement and cheap.
But, what is the best way to go higher power? I am currently looking at a pair of isolated (£££) boost converters to a +/- 70v supply to a (relatively) high idling IRS2092 based board. Alternatively, I would buck down to 12v, then allow a car amplifier to boost to whatever it needs. Aside from being an ugly solution, this is also painfully lossy.
Please, ideas on a postcard below
After many hours of internet searching and increasingly complex solutions being dreamed up, how would you achieve:
600w+ @4R powered by a 42v li-ion battery
The TPA3255 would be the logical choice upto 50V through a boost converter, as its an efficient & single rail device. Whilst also being simple to implement and cheap.
But, what is the best way to go higher power? I am currently looking at a pair of isolated (£££) boost converters to a +/- 70v supply to a (relatively) high idling IRS2092 based board. Alternatively, I would buck down to 12v, then allow a car amplifier to boost to whatever it needs. Aside from being an ugly solution, this is also painfully lossy.
Please, ideas on a postcard below
Optimising the optimised headwize 6n1p otl
- By adamus
- Tubes / Valves
- 20 Replies
Firstly, i wouldnt build this for myself. My personal headphone amps are parafeed / single end.
I am building a parts bin amp for my bro (senn 650s).
So, looking to crowdsource some improvements to this:
My ideas:
The input stage looks badly optimised (The triode curves for the 6n1p arent pretty at low currents). I was thinking ccs load, 8 to 10ma, at the same plate voltage (probably SIC diode bias at 1.6v?)
Possibly put some nfb from output to input? Will help lower the unecessary amount of gain and lower imp?
Bias the heaters at 75v ish. The article leaves them floating floating...
Constraints:
6n1p input and output. I have a load of them, they will cost me nothing.
OTL - he wont spend on txs
350v ish B+, i have an old TX.
£20 limit on new parts to enhance!
thoughts welcome!
I am building a parts bin amp for my bro (senn 650s).
So, looking to crowdsource some improvements to this:
My ideas:
The input stage looks badly optimised (The triode curves for the 6n1p arent pretty at low currents). I was thinking ccs load, 8 to 10ma, at the same plate voltage (probably SIC diode bias at 1.6v?)
Possibly put some nfb from output to input? Will help lower the unecessary amount of gain and lower imp?
Bias the heaters at 75v ish. The article leaves them floating floating...
Constraints:
6n1p input and output. I have a load of them, they will cost me nothing.
OTL - he wont spend on txs
350v ish B+, i have an old TX.
£20 limit on new parts to enhance!
thoughts welcome!
