Author Topic: New project alert! 3 Generations  (Read 14677 times)

Offline ed

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Re: New project alert! 3 Generations
« Reply #15 on: October 16, 2017, 09:21 »
Hi William Bro,

Noted.  I will check out the existing bearing.  I have quite a bit planned for the Lenco though.

Replace stock tonearm and if all goes well will likely do the following:

1. Respray
2. DIY a 6 layered plywood plinth with option for outboard tonearms
3. Tweaks along the way

The wife has been asking me why I got so many parcels lately.  I need a cover for now.  Also she has been questioning me why is there an amp on my DIY work desk and still there after 2 CNYs.  Early last year I DIYed another 300B, all wired up and no time to test voltage.  Sometimes there is just no urgency when you have amps which are already playing well.  But I better wrap this one up before the next CNY, which is about another 120 days from now, else...

Offline ed

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Re: New project alert! 3 Generations
« Reply #16 on: October 18, 2017, 12:29 »
Quite a bit of work done on the tonearm.  Filing off the black coat



First need to grind off the markings caused by molding and filing.  Next would be sanding from grit 320 all the way to 1500 followed by polishing.







Slow progress for now


Offline BTW

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Re: New project alert! 3 Generations
« Reply #17 on: October 18, 2017, 15:06 »
Wah Bro, You very hardcore.. What are you doing next to the tonearm... Drill holes ?

Offline ed

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Re: New project alert! 3 Generations
« Reply #18 on: October 18, 2017, 22:26 »
Wah Bro, You very hardcore.. What are you doing next to the tonearm... Drill holes ?
Yup drill holes



Followed by reinforcing the internal of the tonearm.  Motivated by a website that modded the rb250 beyond recognition.  But I am unable to reach that level due to limitation of resources.  This one is in for the long haul and that is why I bought 2 arms at one go.  1 stays original while I mod the other.  Placing order for a metal stub and counterweight soon.

I am still trying to see what I can improve on the other portion of the assembly.



This is my MM Phonostage.  Quite a performer and was given to me by a friend.  Dumped the stock power supply and worked on my own preferred PS.  I made 2, one was sold to a friend who claimed that it beat his Project Phonostage flat.

The L75 taken out of storage.  This one will take time.  The bearings need a change.



But this week need to wrap up this project.   It has been sitting on my work desk for too long.

jlow

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« Last Edit: May 23, 2019, 14:41 by ed »

Offline BTW

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Re: New project alert! 3 Generations
« Reply #19 on: October 18, 2017, 23:21 »
Great stuff.. Keep up the good work.... :)

Offline ed

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Re: New project alert! 3 Generations
« Reply #20 on: October 19, 2017, 09:46 »
Great stuff.. Keep up the good work.... :)

You bet Bro!  If the modded tonearm turns out good I may just invest in a MC cart.  Zoomed on the Denon DL-103R at the moment.  No fixed plans.  Phonostage wise the DACT CT100 looks awesome, complex and expensive.  Haven't got a chance to find out what MC Phonostages DIY people are making out there.  But I am just keeping this idea as part of future improvements if all turn out well.  Not losing sleep over it at this moment.  I have 3 or 4 amps waiting for me at my store room.

Offline ed

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Re: New project alert! 3 Generations
« Reply #21 on: October 25, 2017, 09:24 »
Trialing youtube video which I uploaded.  Can't seem to insert media, looks like can only use hyperlink.  I am trying to record the same track on different Turntable for comparison.  Recording from phonostage to phone likely the better way.  Anyone have any better way?

https://www.youtube.com/watch?v=ewD6C6kKaAY
« Last Edit: October 25, 2017, 09:33 by ed »

Offline ed

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Re: New project alert! 3 Generations
« Reply #22 on: November 02, 2017, 09:58 »
School exams finally over for my kid!  Slowly starting the DIY activities again.

Not so much of polishing tonearm for the last 2 weeks as I have been trying to clear my tube amp projects.  The 300B is more or less completed but I realized that I do not have the 300Bs for testing to ensure that the current and B+ are the desired values.  Can't seem to find them but I am quite certain I have a pair lying around somewhere in the house.  Well too bad!  Lets move on to another amp.  This one is a Factor FA150, 12AT7 driver with 6414 phase splitter and 6550s in push pull.  It has a burnt output trans on one side when I bought the dodgy amp.  I swopped in a pair of Danbury OPTs which where taken out from my retired EL34 pushpull project.  The Avantic Beam Echos, Maplin and Mullard 5-20s use them and I have no doubts about them sounding good in any EL34/KT88 amps.  Sad to know that Danbury has closed last year due to retirement by the owner.  Well I guess this is life and the old good brands will start to disappear given time.  Swopped in the Opts but still no sound on the dodgy channel and I can't seem to trace where the fault lies after numerous parts replacement no the PCB.  Last straw!  I ripped out the PCB and traced the entire pcb on paper.  My intention is to hard wire instead of relying on the PCB.  I can fix a fault on the PCB but I can't guarantee when the tracks will fail else where on another day as the PCB really looked old and battered.  The circuit looked very similar to the VTL Stereo 75 from Manley Labs less a few parts with different values.  Hard wiring is hard work.  Some pic below on the slow progress...




« Last Edit: November 02, 2017, 12:37 by ed »

Offline wizardofoz

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Re: New project alert! 3 Generations
« Reply #23 on: November 02, 2017, 10:49 »
Power to ya bro...p2p wiring the best but very time consuming. I think I give up on my 2 kt88 integrateds as no time to play and all my setups pretty much active crossovers now to ob speakers.


Better twist all those heater wires...or you using dc for them?
« Last Edit: November 02, 2017, 10:51 by wizardofoz »
I have a pile of stuff that pushes out squiggly waveforms from smaller squiggly waveforms that sometimes come from 1's and 0's.
It's wonderful to behold as long as you don't let the magic smoke out.

Life is short! Enjoy the music while it plays, when it stops, there might be a chair for you...or  maybe not.

Offline ed

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Re: New project alert! 3 Generations
« Reply #24 on: November 02, 2017, 11:15 »
I used to turn the heater wires in other amps but strangely the straight tracks on the PCB is also quiet.  I am trying to go with the same for this amp and see how it work out. DC heaters is always a last resort for me when AC fails.

I have "A few good amps" to round up before I call it a day!

jlow

Better twist all those heater wires...or you using dc for them?
[/quote]

Offline ed

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Re: New project alert! 3 Generations
« Reply #25 on: November 02, 2017, 12:21 »
By the way it took me a long time to trace the circuit so I figured  I will share it with fellow DIYers since Factor has long been defunct.  Just in case you have a Factor amp sitting in some corner of your house.



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« Last Edit: November 06, 2017, 10:00 by ed »

Offline ed

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Re: New project alert! 3 Generations
« Reply #26 on: November 16, 2017, 23:40 »
Someone actually ask me why no updates for so long.  Sorry to keep all waiting ya.  Finally I found my 300Bs and I am just done with voltage check .  It is playing alright.  I will let the parts soak for a good 50 hours before checking the voltages again.  Also this will bring out all the faulty parts if there are any.  Pics below.  Next need to work on the Factor FA150.  Gonna be a busy weekend...

jlow


« Last Edit: May 23, 2019, 14:36 by ed »

Offline ed

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Re: New project alert! 3 Generations
« Reply #27 on: November 20, 2017, 15:02 »
After a good weekend of continuous play everything is good on the 300B.  Voltage has been stable.  I shall leave this amp alone while I focus on others.  But a bit about this amp and design for those who are curious.  It is a 300B Single-Ended, direct coupled, DC Heaters on the power tube and driven by Mullard EF37As.

I found this design years back and made an amp with this design.  Schematics as below:



After I made this amp someone came to listen to it and decided to buy it from me.  I am happy to let it go as I have other amps during that period of time.  All these days I have kept the EF37As in the hope of building this amp again.  In fact I have better looking EF37As in my collection.  But certainly you won't use the best looking tubes in your stable when you are testing/running in your newly built amp right?

I have purposely fixed the 24 step attenuator on top of the chassis just like the tubes and opts because the grid input of the EF37As is on the top cap.  Anyway I must say the Allen Bradley resistors and Mullard EF37As made the amp extremely warm sounding.

The output trans are bought second hand from someone who upgraded his TS Audio (nOrh) 300B OPTs.  The main trans was bought from someone in the forum who wanted to make an Audio Note Kit One but did not managed to start.  The 300Bs are well known for sweet mids and churns out 8 watts which is more than enough for me.  All in all the parts cost me around $800 plus a Hammond Box which I salvaged from previous projects.  This amp was on my work desk for at least 2 years and I am glad I turn it up.  It is never too late. 

For those who are into DIYing your own 300B SE I would dare say this design won't disappoint and the EF37As are relatively affordable and available on fleebay any day.  AC heaters are fine for these tubes as they are not noisy at all.  These tubes pack great value and were manufactured in the 1940s.  As for the 300Bs the sky is the limit.  There are just too many currently manufactured 300Bs in the market and they are all good, with better ones if you have a deeper pocket.  DC heaters for the 300Bs if you wanna get it right the first time round.  For this amp I got to use DC because the heater tappings are 7v AC.  The main and output trans would make bulk of the cost, plus a choke if you have spare cash.  I used a C-core choke which I have kept since god knows when...

I would go for tube rectifier if possible and loved the 274Bs.  But go for SS rectifier if you are cost conscious.  As for the B+ I use Duncan Amp tube PSU designer to model.  Sometimes the actual B+ voltage is spot on.  But if it stray off just workout the current drawn by measuring the voltage drop across the resistor on the PS.  You can then swop in a resistor with the right value to achieve the desired voltage.  This works for me all the time.  The PS on the schematic is dead, you cannot achieve the same readings on the schematic by just following.

Played some familiar tracks last night and the wife commented that it sounded great.  Thats my green light to keep the soldering iron fired up  ;D

Alright that's all for this 300B SE, do look out for my next post on the next tube amp which I am working on.  Also some pics for your appreciation

jlow
« Last Edit: May 23, 2019, 14:36 by ed »

Offline ed

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Re: New project alert! 3 Generations
« Reply #28 on: December 27, 2017, 09:19 »
Back again.  Did I say school vacation is detrimental to DIY?  It really is detrimental and progress is painfully slow.  While working on my Factor FA150 my replacement OPT for my Headphone Amp came.  I built a 1626 Headphone Amp WOT sometime back but one of the OPT is dodgy. The Plate tab fell out with a broken copper wire and I am not sure if it is due to excessive soldering or manufacturing fault.  But I am happy that I can just buy 1 piece for replacement.  This is the risk of buying online.  You don't get to check what you buy and disputes are dreaded, at lease by yours truly.  Soldered the OPT in and fire it up.  Hmm, audible hum noticed on the headphones.  Guess I need to mod the filament supply of the 8532s to DC in this case.  I will always start with AC heaters on the input stage tube and if all ok will let it stay that way.  Else just mod to DC and usually that will do the trick.  Lets hope this one works the same as well.  B+ when loaded is at 253 VDC on the plates of the 1626s which is the optimal operating voltage.  Listening impression wise not very involving to me, I need to plug in a proper source as my current source is a pocket size FLAC player.  Yeah I know, I am a cheapo  ;)  Anyway some pics on how this 12kg headphone amp looks on the underside and top.  Separate left and right channel volume control is a must in my opinion.  If you are using a single pot you will have issues if the volume is not well balanced.

Anyway I hope I have time to quickly whip up a DC heater supply for the 8532s, this is has been sitting that for too long and has to be completed.  In the mean time I will let it run and get the components soaked in.  This one does not draw too much power in any case. 

If anyone is keen to look at the schematics of the amp just search for 1626 Headphone Amp by Bill Howland



After I get it fix will have to continue on the amp below, need to get it settled before CNY.

This wiring looks messy as more components are added.  Easily 200 solders more before I can fire it up for testing.

jlow
« Last Edit: May 23, 2019, 14:40 by ed »

Offline wizardofoz

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Re: New project alert! 3 Generations
« Reply #29 on: December 27, 2017, 12:54 »
Keep at it....part of the enjoyment of the journey :P
I have a pile of stuff that pushes out squiggly waveforms from smaller squiggly waveforms that sometimes come from 1's and 0's.
It's wonderful to behold as long as you don't let the magic smoke out.

Life is short! Enjoy the music while it plays, when it stops, there might be a chair for you...or  maybe not.