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Krell KSA 250

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Hi, I have a Krell KSA 250 that just started to take it's sweet time turning on, once it gets going, seems to operate just fine till you switch it off, then same thing all over again next time you turn on. any ideas?



Thanks Al

WTB 6AS7G

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Hi, i am looking to buy 20x 6AS7G for my new project
Preferably from EU to avoid customs

CAN SEPARATE AMP FROM CIRCUIT? amp rca inputs? 5687/45 single ended integrated amp:

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Hi.
Want use my analog setup preamp to my 5687/45 SET integrated amp skipping the 5687 preamp section adding rca amp inputs. That's possible?
If yes, where should be added the rca inputs ?


diagram bellow :
Thanks for your inputs.

Attached Images
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Head-head sonic battle among the top sounding DIY SS amplifiers :)

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hi all,

Please cast your votes and put your bets below for Battle 1-5. Please write a line or two to justify WHY or HOW ?

There is an ocean of ingenious minds out there who continuously and unconditionally striving to come close to the "ultimate nirvana". Who doesn't ? If you happen to read this post, you know you are too :) Don't deny it!

I figure it would be fun to do something extraordinary to stir up the crowd once in a while. I don’t think this kind of head-head sonic battle has been done before at least not that I am aware of. Of all the Top sounding SS amps, I pick out a few for this battle (Some that I built, some that I have heard for a while). The idea is to gather inputs of those who have built, experienced and A/B their amps. This post will server as good common ground for real life review/discussion and a good baseline for those who are planning to build one amp versus another.

These battles could be controversial since and no ideas are alike. I know , I know. All inputs are welcome. However, please refrain all the insults, condescending, harassment, or bullies to yourself please. I will delete all the posts that are negative to others and go against my original topic. Opinions are only opinions. They will be subjective and bias to the listeners which are totally okay. The beauty is always at the eyes of the beholders. So please be respectful to other opinions about their proudest DIY accomplishment.

Battle 1 : USSA-5 vs First Watt F5

Battle 2: Aksa Lender P-mos Hybrid Aleph (ALPHA) vs First Watt Aleph J

Battle 3: Babelfish J vs Aleph J

Battle 4: Babelfish M25 vs First Watt M2

Battle 5: SissySIT vs Sony VFET v2.0


Let’s the battle begin…..

1……2………….3………………………..

Click the image to open in full size.

Nice capacitor article

Help with Hood Class A board (mockup fail)

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Hi all

I bought a couple (actually 4) of Hood 1969 premade Class A amp boards from ebay. They are premade and have 6 screw terminals on them. They work at about 22-25v AC and I tried to mock up a mono amp with one of them. I should probably point out here the boards would be more than 10w.

This was kind of hard as I needed to heatsink the boards. The boards are no longer on ebay but they are very similar to these ones with different 2 black caps in the middle and pre-adjusted POTs. I used a large aluminium heatsink and a 22-0-22v toroid to try and mock up one channel (click for zoom):

Click the image to open in full size. Click the image to open in full size. Click the image to open in full size. Click the image to open in full size.

Please excuse the poor soldering - I have just got my station and it's not like a cheap iron. The speaker terminals are not shown used (I needed the wire). The mains block is from a Plasma TV and should provide some filtering as far as I know (I can remove this from the equation).

The result: bad. The amp board simply buzzed the speaker and did not amplify any input signal. I hope the method I used is clear from my pictures.

I have another 3 of these boards if the one I tried is now bad but I can't return it :( Any general advice or did I do something wrong? Experts unite!

FS: Toshiba MOSFETs - 2SJ618 / 2SK3497

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Hi guys,

I have to sell buffer stock parts genue Toshiba MOSFETs - 2SJ618 / 2SK3497.
qty: 8pcs N and 8pcs P ( only like pack )
ship: Worldwide
price: 240 EURO ( ex-work incl. shipping and paypal fees )
payment options: paypal

contact: milandks at pobox.sk / slovakia

milandks

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Monoblock ACA bridged mono parallel mono at the flick of a switch

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I have been playing with ACA's recently, swapping between bridged mono and parallel mono operation... and then I realised that instead of having to do a fair bit to go from one configuration to another, there was a pretty capable rating-wise switch at the back that can do both in no time at all.

So, I took a few photos that explain what I did. The switch contacts should be used in parallel to half the contact resistance;)

I considered the safety as well... and could not see any problem in using the switch for either mode.

Especially useful if you want to try monoblock ACA in both modes at your friends' place, for example, where each mode may sound different depending on individual tastes, rest of the system, speakers, room size/damping...

Also, why settle for one mode, when you can change the mode to suit your mood... don't forget to re-wire speaker connections when changing the modes.

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shallow subwoofer options

Suggestions for simple class AB with no global FB.

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Hi,

I've been thinking on building a class AB amp for my Full range speakers with the following criterion:

1) No global feedback. Apparently High efficiency full range speakers tend to dislike global feedback. probably because it results in a much higher damping factor.
2) High quiescent current for low power class A operation.
3) Low power (5 to 10W) is probably enough.
4 ) Reasonable distortion levels (< 0.2%)
5) Fixed supply voltage.
6) Minimum number of stages.
7) Single supply operation as I intend to power it from a power brick.

Of course the easiest starting point would be the traditional 3 transistor with 2 diode for biasing as in the attachment. To push the circuit deeper into class A territory I will use 3 diodes and additional resistor resistor at the emitter.

However a quick analysis will show it is not a very viable circuit.
1) The driver will not have enough current to drive the output transistor at high voltage swings.

There are many ways it can be solved:

1) darlington TIP120 for the output transistors
2) Sziklai Pair
3) or a beefier driver stage with higher bias current by using smaller value resistors. However that will result in very low input impedance, so might have to use a mosfet or Jfet to drive the transistors.
4) Use a voltage follower for the driver stage and an additional gain stage.

I would like you opinion which do you think is the best solution.

Other than that would appreciate any comments of how this can circuit can be improved?

1) Zener regulator for the driver stage?
2) resistor and large cap power supply bypass for the driver stage?

Thanking all in advance.

Oon

Attached Images
File Type: jpg Simple AB amplifier.JPG (29.7 KB)

Pam8403 class d module

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Hi all
Is anyone knows how is the pam8403 output waveform?
Can we get spwm wave of this module when we don't connect lc low pass filter?
My idea is get spwm from this module and send that wave to another half/full bridge to get high power.
What do you think about it?

I attached pam8403 datasheet.

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File Type: jpg 81jNyK-cuaL._SL1490_.jpg (301.6 KB)
Attached Files
File Type: pdf PAM8403.pdf (375.2 KB)

Looking for a great MM phono stage

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I have sold my MC cartridges and Rega Aria and bought a few vintage MM carts. I do have an old BHL Jfet phono to use until I build/buy something better.

So I'm looking for opinions on good phono stages to compliment an SP10 EPA-100 and EPC-100 and 205, I also have a Stanton 881s

The ones I am considering ATM are:

Emerald
Pass Pear 2
Xono
Bugle



Anyone have experience with this one.
6 Platinen XOno komplett bestuckt Nelson Pass, MC/MM, Phonovorverstarker DIY | eBay

FD61 - Modular Full Range driver with 3D Printed Components - Complete!

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Hello everyone

I have decided to make a new thread for information around the specific models being launched which will start on Kickstarter to try and gauge the level of interest. For anyone with questions around the development and challenges, please post or see the thread below:

https://www.diyaudio.com/forums/full...velopment.html

Click the image to open in full size.

This is a KIT driver, meaning you will get all the individual components that make up a loudspeaker driver, and you can assemble at home. I can't think of another driver that allows you to do this, especially at this size.

A single driver will be coming in at £40 each, but there will also be some early bird pricing at launch, so if you are interested, it will be better to get in quickly!

On top of the ability to make the driver yourself being very unique, the drivetrain is also interchangeable. This means as I develop more variants, you can swap out the material, cone profiles, level of compliance etc. This takes 8 screws so not very much time. The build itself has been made to be as easy as possible. It is no more complex than assembling a airfix plane kit. If anything it is easier

The 2 starting models are FD61-4PW, and FD61-4CF.

4PW is built with a rolled up high end to try and replicate older drivers with high inductance levels, but this roll off is from the material and cone profile, not inductance, so the driver is still easy to drive from your amplifier.

4CF is built to be a more modern style driver and be working to extend the frequency range. Current revisions are at 16,000Hz, but both drive trains between now and the end of the year will be revised to make sure I extract as much as possible.

I have not released Thiele & Small parameters yet due to the revisions to happen. The main goals in these revisions are the extended frequency of 4CF, and improve compliance further than I already have.

Other features include interchangeable phase plug & even the magnet motor itself. Plan to use it for midrange? You can change the layout of the motor to lower xmax and improve BL. Xmax levels can vary from +/- 0.5mm to +-2.5mm. The underhung voice coil design has been used to help with unclean winding within the magnetic gap, and a fill ratio of 55% enabled crossing of the winding wires without rubbing in the gap occuring.

Any questions or queries, please post and ask. I will post an update regardless when the campaign goes live. If any moderators feel the thread needs to be taken down, please do so.

Thanks, and keep building!

Paul

(flat) Voxel under cabinet

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Hi all,


In addition to the Overnight Sensation's (TM) I'm currently building, I am planning on adding a variation to Paul Carmody's Voxel to support LFE (30~60 Hz).

As I'm planning to make the OS's look nice, they will be allowed a spot on top of the tv cabinet. A subwoofer however, is very unlikely to score a high WAF...
That's why I would like to modify the Voxel design, so it can be completely hidden from sight, under the cabinet.

I had the idea of making a triangular enclosure in MDF (1/2"), with the w5-1138 being angled towards the floor. The width I can choose freely, to achieve the internal volume of the standard Voxel design.
See some dimensions on the attached picture.
For the port, I would run a length of PVC pipe outside of the actual enclosure.

Does all of this make any sense? :)


- With the subwoofer being located under the tv-cabinet, against the rear wall & very close to the floor, should I expect fantastic or rather terrible "corner loading"?

- Does the external port behave any different from a regular internal port?
Is it ok to have the port placed along the corner between the rear wall & the underside of the tv-cabinet?

- Can I add a grill over the subwoofer driver without impacting sound quality? (we have two toddlers, who might have some pokey fingers...)


Best regards,
Stefaan


Imgur: The magic of the Internet


Click the image to open in full size.

UY-224 or 24 etc

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Really for anyone in the U.S who may have found a use for this early tetrode. The spec sheet advises (RC coupled amp) a 250v ht supply with RL around 150K, bias at -1v with 25v on the S.G (which appears rather low compared with more common 90v in other applications) I am aware that tetrodes of this type are not usually recommended for audio but,anyone used them please?

David W (UK)

Capital Audio Fest 2019

What is the difference between pre-amplifier and input attenuator?

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It seems people confuse input attenuators in amplifiers with preamplifiers.
I think pre-amplifier is already in DAC.

Tektronix 465

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Caros Senhores.

Gostaria de deixar uma colaboração para manutenção do Osciloscópio Tektronix 465, que utilizo na minha bancada.

1 - Osciloscópio inoperante, sem traço: C1549, capacitor de tântalo em curto.

2 - Traço com muito brilho, sem controle de intensidade: CR1488, diodo com
pequena fuga reversa.

3 - Fonte com tensões especificadas, tela só com ponto central, sem traço: L#, indutor interrompido, alimenta +5V em U870.

Grato.

Abraço.

Soundlab A3-PX

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Hi, What make's a Soundlab A3px click or tic about every 10 mins? other than that it sounds fine.

Thanks Al

Mcintosh MC240 Hum on one channel, need help

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Hum sound from left channel, could anyone advise likely cause and faulty component(s), thanks
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