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MATT0404

New Dynakit ST-35 Build

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Thought I'd share this fun project here since I'm using this amp on my Cornwalls.  This was my first kit build and I have to say, this is a very well put together kit with quality parts. 

 

The build itself took around 10-12 hours in total.  I plugged away at it a couple/few hours at a time.  The only hiccup was my own fault.  I deviated from the manual and installed a CL-80 thermistor on the line in.  Problem was that I installed it in the wrong location and the amp blew the fuse when I first turned it on.  I removed the thermistor and it fired right up.  All voltages checked out and it's been making fine music now for 12+ hours.  Really great little amp and it was a lot of fun to build.  

 

Here are some pics from the build and a demo video.

 

Kit as it arrived

48395825292_7fdca231a4_b.jpgDynakit ST-35 by Audio Database, on Flickr

 

PCB's stuffed and installed

48395824967_c9199246e0_b.jpgDynakit ST-35 by Audio Database, on Flickr

 

48395684621_861f60bf6d_b.jpgDynakit ST-35 by Audio Database, on Flickr

 

48395823272_597d591637_b.jpgDynakit ST-35 by Audio Database, on Flickr

 

Transformers and can cap installed

48395822607_f92c4f3b1a_b.jpgDynakit ST-35 by Audio Database, on Flickr

 

48395821677_2471d228fb_b.jpgDynakit ST-35 by Audio Database, on Flickr

 

48395820672_97212e81f2_b.jpgDynakit ST-35 by Audio Database, on Flickr

 

WIring in process

48395681001_d25369e92a_b.jpgDynakit ST-35 by Audio Database, on Flickr

 

WIring complete

48395819092_95c0948cd3_b.jpgDynakit ST-35 by Audio Database, on Flickr

 

48395818677_18642db139_b.jpgDynakit ST-35 by Audio Database, on Flickr

 

Testing

48395703626_4697928de1_b.jpgDynakit ST-35 by Audio Database, on Flickr

 

DONE :D

48395831377_b34c9b2cb4_b.jpgDynakit ST-35 by Audio Database, on Flickr

 

48395831502_c2d47a57ea_b.jpgDynakit ST-35 by Audio Database, on Flickr

 

Demo video

 

 

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Awesome!!!

img.jpg

 

Still breaking in?

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Thanks for sharing this.  It looks great.

 

It warms the heart of this 70 year-old with many Dynakits and Heathkits under his belt.

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Thanks, guys!  It's still breaking in, but I've probably got 15 or so hours on it now.  Sounding pretty damn good if I don't say so myself.  The top end opened up quite a bit after the first few hours.  I haven't noticed too much of a change since they.

 

I'll incorporate the Gillespie power supply board and EFB mod at some point in the future, but I wanted to hear it in stock configuration first.  

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What tube selection are you using?

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Congrats :D Looks like a great job! Build an ST-70 about a year ago and was pretty pleased with it.  Haha; but went back to higher powered SS amps :D 

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23 minutes ago, Schu said:

What tube selection are you using?

Very closely matched quad of Sovtek el84m's and a pair of NOS RCA 12dw7's.

 

4 minutes ago, Emile said:

Congrats :D Looks like a great job! Build an ST-70 about a year ago and was pretty pleased with it.  Haha; but went back to higher powered SS amps :D 

Thanks!  👍

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Daves thinking on the subject is bar none... way smarter than me... that said.

I would suggest 2 simpler mods you might really like. 

1st, bypass C1. Its for DC blocking... you don't need with anything modern.

2nd and more interesting... replacing the 50ohm resister in the PS with a C354 choke will go a long way to reducing the noise floor... likely to improve the bass too. 

You'd drill 2 holes and mount it up too. I think Dynakitparts even has pictures of this done. 

The ST35 was called the poor mans Macintosh for good reason. Its sonics are lovely.

At 15watts, its likely more than enough power for your Cornwalls.

 

Congrats!

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17 hours ago, justinsweber said:

Daves thinking on the subject is bar none... way smarter than me... that said.

I would suggest 2 simpler mods you might really like. 

1st, bypass C1. Its for DC blocking... you don't need with anything modern.

2nd and more interesting... replacing the 50ohm resister in the PS with a C354 choke will go a long way to reducing the noise floor... likely to improve the bass too. 

You'd drill 2 holes and mount it up too. I think Dynakitparts even has pictures of this done. 

The ST35 was called the poor mans Macintosh for good reason. Its sonics are lovely.

At 15watts, its likely more than enough power for your Cornwalls.

 

Congrats!

The kit came with mounting hardware and instructions for the choke, but I needed to order it separately.  I'll order it now and report back my findings.  I'll also look into bypassing C1.  Thanks for the info!

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That's a good looking amp build. Great job! I built a VTA ST-70 about 2.5 years ago and it's still running strong and drives my Belle clones with authority and ran my CF-3's great, too.  Unlike @Emile, I kept mine. ;) Oh, and I do still have a 60wpc, 125wpc, and 460 wpc amps just in case for other speakers as Belles dont need it.

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Nice work. I used some Dynakitparts.com components in restoring an original Stereo 35. I went further and purchased Dave Gillespie’s Enhanced Fixed Bias (EFB) circuit board to improve the performance of the amp. The EFB modification reduces distortion, increases headroom and extends power tube life. I highly recommend this modification of an already fine amp. 

 

http://tronola.com/html/daves_store.html

 

You will be rewarded with cleaner and smoother mids and highs, and a better defined bass. It sounds like the amp is weightier and more powerful, but still maintains that rich EL84/6BQ5 tone. 

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On 7/28/2019 at 9:41 AM, MATT0404 said:

 

 

 

Nice system!

 

Who makes the sub? Specs?

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I would also recommend using the Dueland DCA16GA or DCA12GA Cotton-insulated, Tin-plated Copper wire for speaker wire. It’s not terribly expensive, and you’ll be amazed at how this wire will enhance your listening pleasure. 

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10 hours ago, rhing said:

Nice work. I used some Dynakitparts.com components in restoring an original Stereo 35. I went further and purchased Dave Gillespie’s Enhanced Fixed Bias (EFB) circuit board to improve the performance of the amp. The EFB modification reduces distortion, increases headroom and extends power tube life. I highly recommend this modification of an already fine amp. 

 

http://tronola.com/html/daves_store.html

 

You will be rewarded with cleaner and smoother mids and highs, and a better defined bass. It sounds like the amp is weightier and more powerful, but still maintains that rich EL84/6BQ5 tone. 

Thanks, I  have read up on the EFB mod and would like to incorporate it into this amp at some point.  I even went as far as ordering the board/parts, stuffing the board, then, when I realized how big the heatsink was, I noticed I ordered the board for the SCA-35!  It won't work with the ST-35 obviously, so I'll have to do the power supply board to incorporate the EFB mod.  

 

9 hours ago, Blackbird said:

 

Nice system!

 

Who makes the sub? Specs?

Thanks!  The sub is a Power Sound Audio S-1800.  

 

Specs:

  • Sealed 22x20x20.5" enclosure
  • USA built, proprietary 18" driver with powerful motor strength and efficiency.
  • Patented digital ICEpower® 725W amplifier with DSP control
  • CNC precision cut cabinets that are finished in our industry exclusive satin black texture
  • 17Hz-200Hz +/-3dB (7Hz-11Hz typical in-room extension)

 

2 hours ago, rhing said:

I would also recommend using the Dueland DCA16GA or DCA12GA Cotton-insulated, Tin-plated Copper wire for speaker wire. It’s not terribly expensive, and you’ll be amazed at how this wire will enhance your listening pleasure. 

I'll take a look.  Thanks!

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On 7/28/2019 at 9:22 PM, Emile said:

Congrats :D Looks like a great job! Build an ST-70 about a year ago and was pretty pleased with it.  Haha; but went back to higher powered SS amps :D 

How about a low powered class A amp? Try a JLH 1969 10 watt per channel, or one of its variations.It sounds much more powerful than 10 watts and is a wonderful sounding ,simple amplifier.

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Love my Mullard powered ST35.  Hate that the RCA's are on the opposite side of the chassis though.

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On 7/28/2019 at 10:29 PM, justinsweber said:

Daves thinking on the subject is bar none... way smarter than me... that said.

I would suggest 2 simpler mods you might really like. 

1st, bypass C1. Its for DC blocking... you don't need with anything modern.

2nd and more interesting... replacing the 50ohm resister in the PS with a C354 choke will go a long way to reducing the noise floor... likely to improve the bass too. 

You'd drill 2 holes and mount it up too. I think Dynakitparts even has pictures of this done. 

The ST35 was called the poor mans Macintosh for good reason. Its sonics are lovely.

At 15watts, its likely more than enough power for your Cornwalls.

 

Congrats!

Just thinking that mods are always a possibility.  It's freshly built (awesome, by the way!!), and I guess I would recommend becoming familiar with its in-born sound signature first -- which I'm sure you were also implying.    As you indicated above, Justin, "Its sonics are lovely."  Always in agreement with using a choke in the PSU, the requirement of course being adequate chassis space.  Thanks for sharing this Matt0404!  The lighting on the new chrome and transformers is elegant looking; really nice!

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On 9/3/2019 at 3:57 PM, erik2A3 said:

The lighting on the new chrome and transformers is elegant looking; really nice!

 

It does look beautiful! I was looking at the site and those chassis are polished stainless. Should look great for a long time.

 

How's the Moth rebuild going? I hope you will post some pics of the work.

 

Bruce

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Hi Bruce,

On my bench, on hold until after my back surgery tomorrow.  I should be able to start getting into it 'lightly' in a week or so.  Happy to share a "Kodak Moment" right now if interested.  Being a stereo SET, it's a heavy amp, so can't turn it upside down to work on it until I heal up a bit.

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