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DECWARE 300B Amp development thread (Read 126279 times)
Steve Deckert
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Re: DECWARE 300B Amp development thread
Reply #800 - 01/08/23 at 02:44:31
 




(click to enlarge)


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Kamran
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Re: DECWARE 300B Amp development thread
Reply #801 - 01/08/23 at 02:46:39
 
Haha..Last week I had the pleasure of speaking to Sarah about Sarah and felt a little discombobulated trying to keep the amp and person differentiated as I figured out my options.

Steve, love love the laser engraving on the transformer!  Thanks for taking us through the inner build.  That was fascinating and educational at the same time.
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Steve Deckert
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Re: DECWARE 300B Amp development thread
Reply #802 - 01/08/23 at 03:19:20
 

Speaking of discombobulated, I stumbled across this picture and realized that you are actually looking at DECWARE over 20 years in the past.  From left to right is Sarah (customer service manager) Jake (shipping) Josh (parts) Myself and wife DeVon (General Mgr).






You can see that even back then you didn't tell these strong women what to do!  Not only did that women on the right take care of everyone in the picture and wrestle with Sarah but at the same time helped form and run Decware which she continues to do today but with the addition of seven grand kids!  There is not a person in this picture that Decware can run for more than two days without and that's even with the help of the other six people who work here.

Smiley
Anyway, I had absolutely no clue when this picture was taken that we would be having this conversation today about an amplifier deservedly named after Sarah!















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Same Old DD
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Re: DECWARE 300B Amp development thread
Reply #803 - 01/08/23 at 05:20:38
 
Absolutely amazing pic!!
So much history yet to see unfold.

I just wish that old Schofield looking break front revolver was not pointed so close to your ear.

Smiley

I can only bow with respect!
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Re: DECWARE 300B Amp development thread
Reply #804 - 01/08/23 at 12:49:05
 
Steve,

Simply amazing build, quality, care and details on the Sarah 300B amplifier. This is a true classic in the making thanks to you. I really like the last minute changes of the recessed meters and tube layout on top of the transformer. Looking forward to seeing the Decware colored meters when they are available.

I'm so glad I got in the pre-order que for this masterpiece.😊

HK
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Re: DECWARE 300B Amp development thread
Reply #805 - 01/08/23 at 14:06:44
 
This step by step built pictures reminds me of my FirstWatt F5 that I built, every single move need to be carefully thought, and is what I enjoyed in the building process, pause...think....not sure of yourself....read...ask....search, I did all this before starting anything, it took me a long time but then the built went smoothly and surprisingly fast.
If this Sarah was a kit, I would get into it right away!

-A side question : could these 274B tubes be used in a 84 UFO-2 ?
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Re: DECWARE 300B Amp development thread
Reply #806 - 01/08/23 at 14:19:25
 
The Sophia Electric Aqua 274B that I have been using for five years now in my amps certainly could.
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Re: DECWARE 300B Amp development thread
Reply #807 - 01/08/23 at 15:08:06
 
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Lon
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Re: DECWARE 300B Amp development thread
Reply #808 - 01/08/23 at 15:20:38
 
It will work.
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Tooppy
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Re: DECWARE 300B Amp development thread
Reply #809 - 01/08/23 at 16:03:40
 
Can you explain sonic differences from the original 5U4G....if any ?
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Re: DECWARE 300B Amp development thread
Reply #810 - 01/08/23 at 16:23:58
 
There are so many differences between the different types and brands of 5U4 that I really can't. I will say that the Sophia Aqua 274B that I have presents a big and bold soundstage and tonal presentation. . . feels more "powerful" than most of the other rectifier tubes I have used, and has a clarity, a resolution, better than most.
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Re: DECWARE 300B Amp development thread
Reply #811 - 01/08/23 at 18:22:03
 

I hope I am not muddying up the water, but...

Above somewhere, re 274B,  CAJames said:

The key spec for a rectifier for Sarah (mesh or not) is it needs to deliver 200 mA DC current.


sales@sophiaelectric.com sent me the following:


"This means the rectifier tube can handle at least 200 ma. Our Aqua 274B only handles up to 160 ma. So you can’t use Aqua 274B in your amplifier.

We have a vintage rectifier tube (https://sophiaelectric.com/collections/274b-5u4g/products/nos-5z3pa-rectifier-t
ube) you can use with good sound at a much lower price."


I'm confused.

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Re: DECWARE 300B Amp development thread
Reply #812 - 01/08/23 at 18:33:15
 
Well, that is a wrinkle then. The manual does say that about the 200ma, and the Aqua specs do mention 160ma. Looks as if none of the Sophia Electric 274B will work in the SEWE300B. I ordered one of the NOS rectifiers they recommended from them.
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CAJames
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Re: DECWARE 300B Amp development thread
Reply #813 - 01/08/23 at 18:34:43
 
I found the reference to 200 mA, it is in the Rectifier section on page 4 of the SEWE300B manual:

https://www.decwareproducts.com/_files/ugd/f1f204_43e0fad1767b4d279e3e3b253a2efc...

Beyond that, YMMV.
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Re: DECWARE 300B Amp development thread
Reply #814 - 01/08/23 at 18:58:40
 
Note however that Steve also likes the GZ34/5AR4 rectifiers in the amp and they are rated for 160 mA too. So maybe 200 is more of a guideline than a rule....
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Re: DECWARE 300B Amp development thread
Reply #815 - 01/08/23 at 21:37:03
 
Quote:
Speaking of discombobulated, I stumbled across this picture and realized that you are actually looking at DECWARE over 20 years in the past.  From left to right is Sarah (customer service manager) Jake (shipping) Josh (parts) Myself and wife DeVon (General Mgr).


Aww..what a fantastic family picture Steve! This epitomizes how I feel about Decware.  A family, above everything else. Hope you had the ladies consent to post it!

Quote:
There are so many differences between the different types and brands of 5U4 that I really can't. I will say that the Sophia Aqua 274B that I have presents a big and bold soundstage and tonal presentation. . . feels more "powerful" than most of the other rectifier tubes I have used, and has a clarity, a resolution, better than most.


I second the Sophia.  Even though it’s not currently part of my rotation (the Mazda 5Y3 is supporting the Visseaux 6V6 right now), I love that rectifier tube and agree with how Lon described it with one more addition.  I think the Sophia also presents vocals a hair more  organically (naturally) compared to other rectifiers I have used (GE 5U4, Blackburn Mullard GZ 34, Mazda 5Y3).  If we can’t use it with Sarah, I’ll just find it a new home.
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Steve Deckert
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Re: DECWARE 300B Amp development thread
Reply #816 - 01/10/23 at 02:32:25
 

The amp draws between 160~175mA during operation.  200mA is giving a small safety margin so people don't have issues, especially with weaker used NOS or Chinese tubes.

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Re: DECWARE 300B Amp development thread
Reply #817 - 01/10/23 at 02:47:03
 

We have received the first 100 coupons from Western Electric.  These will be either included with the amplifier or mailed in advance per the customers request.  Not shown below but each coupon will have a unique code that can only be used once.







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Re: DECWARE 300B Amp development thread
Reply #818 - 01/10/23 at 02:51:08
 

Before I post more pictures of this build... This technique and parts are how we build all of our amplifiers.  There is no layout like you see on so many amplifiers, and the reason for that is the wires.  Lining up all the parts in a row on a board or terminal strip and then running wires to where those parts needed to connect is easier to build, looks nicer, but sounds worse.  We just try to keep everything happening in 3D space with the least number of solder nodes that would be practical.  Keeping wire lengths the same and channels symmetrical, parts close together that can be, distances between parts and orientation often has to do with magnetic fields, heat, vibration or all of the above.

 
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Re: DECWARE 300B Amp development thread
Reply #819 - 01/10/23 at 02:58:33
 
The Output transformer secondary wiring is done next.  These transformers are made with heavy gauge silver-plated wire in a Teflon jacket.  The switches are Mountain brand with silver contacts, same as used in all of our stuff.  It is a DPDT switch where both sides are wired in parallel to double the contact area.  Why trust your audio signal to one switch when you can have two. The same is done for the input jacks where the switch located between them selects your source.  Having only 1.5 inches of heavy silver Teflon wire between the RCA and silver switch done in this way is transparent like it wasn't even there.






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Re: DECWARE 300B Amp development thread
Reply #820 - 01/10/23 at 03:09:40
 

Now it's time to finish the audio ground.  The copper buss is the trunk of the tree.  Now we have to construct the branches. Remember, ground current is like water flowing in a hose. The black wire that connects to the end of the copper buss on each side is the remainder of the main audio ground for the amp.







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Re: DECWARE 300B Amp development thread
Reply #821 - 01/10/23 at 03:20:31
 

We use dual ganged volume pots (one shown below) because of the feel.  Having the friction from two wipers gives the volume control a nice quality feel when it rotates.

In the case here where we set the amp up with a separate volume control for each channel we still use dual pots but only one half is used so the 100K impedance is maintained.

These are ALPHA pots which have proven to be a favorite over the years with a taper that nicely compliments the input sensitivity of the amplifier.




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Re: DECWARE 300B Amp development thread
Reply #822 - 01/10/23 at 03:27:50
 

The amp uses a novel hum balance circuit of which this is the capacitor used in it.  It is mounted here on the meter to eliminate a connecting wire and isolate it from the metal chassis that will will be very warm.  The less heat an electrolytic cap sees the longer it is likely the last.  






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Re: DECWARE 300B Amp development thread
Reply #823 - 01/10/23 at 03:33:10
 

Now we can hook up the last two dangling wires on the output transformers...  and things will stop feeling so chaotic.  Next will be building the filter network.  The yellow wire with black stripe is the center tap from the 5V secondary that is connected to the rectifier.  This is where we tap the high voltage so it all starts here at that node.  That said I will be building it backwards from left to right, I'm not sure why.





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Re: DECWARE 300B Amp development thread
Reply #824 - 01/10/23 at 03:46:41
 

We will start with the last node here, which is what will power the the input and driver tubes.  Couple things; the large copper foil cap is the bypass cap for the black electrolytic cap.  The white one is MIFLEX made in Poland, and the black is F&T made in Germany.  In my experience it is the best electrolytic of its type available.  All of these caps are axial-lead caps because they often sound better than radial caps that connect to circuit boards.  

We like the caps to float in air so that they have the same temperature around the circumference of the cap. If it were glued to a board or the hot steel chassis -- part of the cap would be at a different temperature.  In a signal cap, the burn-in process is about the foil and dielectric film between the foil layers moving around until they seat and stop moving.  That is when your amp is broke in.  However, if the cap is a different temperate at one end than the other -- or one side vs the other, the dielectric film is being pulled which is going to smear certain things in the sound not unlike a cap that isn't fully burned-in.







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Steve Deckert
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Re: DECWARE 300B Amp development thread
Reply #825 - 01/10/23 at 03:50:26
 

Moving right along, this is the next node that will be supplying the output tubes.  Same size bypass cap to match the speed and timing of the input and driver tubes.  More electrolytic to handle the higher current of the output stage.





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Re: DECWARE 300B Amp development thread
Reply #826 - 01/10/23 at 03:55:51
 

And one to get my ears ringing when the techs have to fashion this... the input cap, which I wanted to be rated at 800 volts and be 4uf without being a large film cap.  Loosing the speed signature of the electrolytic at this point would be a mistake, so we have to make our own cap, and bypass it as well.  This cap is separated from the others by the choke and a series resistor.  It's a pain in the ass to make, the resistors are to balance the caps during the initial charge and act as a bleed down resistor to discharge all of the capacitors over time.







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Re: DECWARE 300B Amp development thread
Reply #827 - 01/10/23 at 04:01:59
 

And one more electrolytic and film cap to handle the other side of the choke that we will install towards the end of the build.  This completes the capacitors for the power supply of the amplifier.










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Re: DECWARE 300B Amp development thread
Reply #828 - 01/10/23 at 21:08:42
 
I love seeing your craftsmanship, Steve. Most of this technical stuff is lost on me, but your transparency is a breath of fresh air in our current market. It's rare to even know where a product is built these days, let alone to hear about the the nuances and idiosyncrasies of its innards! Keep it up, brother!
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Re: DECWARE 300B Amp development thread
Reply #829 - 01/10/23 at 22:43:31
 
Bluemage,

+1. I need another amp like I need another pair of speakers, which is to say not at all, but I do really enjoy following the build threads for Steve's various masterpieces. If there is another audio manufacturer who opens up his process the way Steve does, I haven't heard about it. Big thanks to Steve, Randy and all the posters here for a major upgrade of my audio education.

Randy
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Re: DECWARE 300B Amp development thread
Reply #830 - 01/11/23 at 03:30:25
 

Thank you for all the kind words. The truth is that the magic of much of the sound of these amp comes from this part of the process so it is in reality the most telling aspect of the design I would say.  By now, with circuit boards I could have easily had four amps done.  It's not going to hurt people to see the inside of the process because it will only help them appreciate the result that comes from it.






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Re: DECWARE 300B Amp development thread
Reply #831 - 01/12/23 at 14:39:31
 
Update: concerned about the 200ma warning Steve wrote about rectifiers I ordered one of the rectifiers that Sophia Electric recommended to use, from this page:

https://sophiaelectric.com/collections/274b-5u4g/products/nos-5z3pa-rectifier-tu...
be

I received the NOS 5Z3PA and it's a very well-made substantial seeming NOS Chinese tube. As I only had one I couldn't use this in the Monoblocks but did run it a few hours in my CSP3 with the Anniversary mods. Not as much to my liking as the Sophia Electric Aqua 274B by a long shot, but I'll put it aside to try in the SEWE300B.

Speaking of the SEWE300B sometimes I feel I must be insane for going into financial straits ordering one and paying for it. My system sounds so amazing. Recent tube-rolling and attention to noise in the system has me just gob-smacked and in a trance sometimes. Do I need another amp? NO! But I do want to hear the SEWE300B in my home.
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Re: DECWARE 300B Amp development thread
Reply #832 - 01/12/23 at 15:01:26
 
Quote:
Speaking of the SEWE300B sometimes I feel I must be insane for going into financial straits ordering one and paying for it. My system sounds so amazing. Recent tube-rolling and attention to noise in the system has me just gob-smacked and in a trance sometimes.

LOL, Lon, I hear you. The past 17 months on the waiting list have provided me the opportunity to attend to every other aspect of my system so that my room sounds perfect right now.

The honest appraisals of Decware owners like you are one of the biggest factors that convinced me to place my order (even though the original order has been changed twice now). This kind of transparency makes the decision a no-brainer...I know exactly what I'm getting, and I am completely confident this amp will easily meet and exceed my expectations.

So, thanks not just to Steve and his team, but to you and forum members like you.

Michael
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Re: DECWARE 300B Amp development thread
Reply #833 - 01/12/23 at 15:36:45
 
From the Sofia Electric site:
Quote:
Sophia Electric Princess mesh plate 274B and rigid plate 274B tubes have been widely praised as the best sounding rectifier tubes ever made. However there is a catch - the first capacitor after the rectifier tube needs to be small. The max value allowed for the Princess 274B mesh plate is 4uf, or 8uf for the Princess 274B rigid plate. But for a typical 300B single ended amplifier, it is usually larger than 8uf. To overcome this limitation, Sophia Electric came out with a newly designed Aqua 274B rectifier tube to raise the limitation from 8uf to 47uf. This Aqua 274B can directly replace 5U4G in most amplifiers with great sonic improvement.

Aqua and WE 274B tubes would deliver 150ma-160ma of current at 430vDC per 274B tube.

Stereo 300B tube amplifier needs to have one 274B rectifier tube per channel, two 274B rectifier tubes for two channels.  If the amp was designed to have only one rectifier tube for both channels, then 5U4G is more suitable.


FWIW - Michael
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Re: DECWARE 300B Amp development thread
Reply #834 - 01/12/23 at 15:46:29
 
Ghostship wrote on 01/12/23 at 15:36:45:
From the Sofia Electric site:

FWIW - Michael

Yes. . . I admit to being a bit confused about the whole rectifier thang in this SEWE300B amp. I had been assuming the Sophia Electric Aqua 274B which I love so much would be fine in that amp, as it is electrically, as I understood it, similar to the 5U4G. I have been using one in my Monoblocks and in the audio visual system in my CSP3+ and as I have a spare I know I will risk trying it in the SEWE300B when that day comes. If there's an issue, then I'll try this one from Sophia Electric that they recommend. . . and I have others as well.
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Re: DECWARE 300B Amp development thread
Reply #835 - 01/12/23 at 16:29:30
 
Quote:
Posted by: Lon      Posted on: Today at 15:46:29

Yes. . . I admit to being a bit confused about the whole rectifier thang in this SEWE300B amp. I had been assuming the Sophia Electric Aqua 274B which I love so much would be fine in that amp, as it is electrically, as I understood it, similar to the 5U4G...


I think at least part of the confusion is that for so long, esp. for the UFO type amps, all the discussion was about the maximum size of the first power supply capacitor, whether (or how close) it was for 47 uF. The actual DC current requirements for the UFO are low, so the only thing we needed to worry about was the cap.

The 300B amp turns that on its head. Now with first PS cap is very small, so pretty much any rectifier checks that box. But the DC current requirement is much more significant, and perhaps too much for many rectifiers.

So when people say e.g. the Aqua 274B is similar electrically to the 5U4G, they were talking about the capacitor rating. There is and has always been a real difference in the rated DC current output, with 5U4G rated for 225 mA. It didn't matter when we were talking about UFOs, it does matter for Sarah.

But note also, that just as the first capacitor rating is more of a guideline than a rule, so is the current rating. I'll never tell anyone to ignore it, but I expect that lots of rectifiers rated for 160 mA would work fine. For example Steve likes the GZ34/5AR4 and it rated for 160 mA.
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Re: DECWARE 300B Amp development thread
Reply #836 - 01/12/23 at 16:49:30
 
Yes, and Steve liking those rectifiers and using them was what was most confusing to me.

This is one case where having a few dozen different rectifiers is a nice thing to have on hand. . . and I'm never averse to adding to my tube collection, more's the pity. . . . If it comes down to using 5U4G I have four pairs of those, two different construction RCA, one branded Zenith, and one branded DuMont.
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Re: DECWARE 300B Amp development thread
Reply #837 - 01/14/23 at 00:37:50
 

The Sarah 300B amp draws 160mA with both WE300B and the selected Chinese 300B tubes.   I haven't had issues with good rectifiers rated at 160mA but if you get a tired one or one that has been thrown around a lot, then expect it to fail and blow the external fuse. Still a favorite is the 5AR4, but I will be shipping the amp with 5U4G because it is rated higher and will therefor be likely to last longer.







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Re: DECWARE 300B Amp development thread
Reply #838 - 01/14/23 at 00:58:04
 

Let's build the preamp stage.  Remember it wasn't needed for gain, but for voicing and to create a gain structure, which is voicing. Huh   So here is the 12Au7 input tube.  It is fed directly off the voltage regulator tube that is 1/2 inch away so no need for wires and extra solder nodes.







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Re: DECWARE 300B Amp development thread
Reply #839 - 01/14/23 at 01:06:02
 

This nearly completes the input stage.  The black ground wire from the input tube (a dual triode used for both channels) is connected to the exact center of the audio ground buss.  This keeps the current from the input stage from mixing with the current from either channels.  This stage has full output at all times.  It feeds the volume controls which in turn feed the 6N6P driver stages.





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Re: DECWARE 300B Amp development thread
Reply #840 - 01/14/23 at 01:10:53
 

The distance between the volume control and the driver tube is the length of the resistor so that no wire is needed and additional nodes are not being created.  The less nodes the better the sound.





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Re: DECWARE 300B Amp development thread
Reply #841 - 01/14/23 at 01:13:19
 

Here it is getting close to finished.  Ready for the large choke that goes in the middle.






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Re: DECWARE 300B Amp development thread
Reply #842 - 01/14/23 at 01:20:10
 

Time to wire the inputs.  We use both channels of MOGAMI wire after years of testing different internal wires and this is our favorite.  So we have two conductors soldered into one and connected to two switch contacts soldered together.  The cable is shielded all the way to the input tube.




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Re: DECWARE 300B Amp development thread
Reply #843 - 01/14/23 at 01:28:24
 

This is where the input cables go.  This is the custom filter I developed as part of the voicing for the amplifier.  Despite all the parts you see, there is only one resistor (the blue one) in the signal path of each channel.  The input and output are 1/4 inch apart.  Everything else is simply going to ground.  The switches turn it on and off.





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Re: DECWARE 300B Amp development thread
Reply #844 - 01/14/23 at 01:34:43
 

And here is what it looks like when it's done.




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Re: DECWARE 300B Amp development thread
Reply #845 - 01/14/23 at 01:52:49
 

And here it is being tested with the good sounding Chinese tubes.  I recently found some that looked like these that were completely unacceptable. The bass was bloated and ugly -- Something easily missed in China because they don't listen to bass heavy music.  Anyway after testing over 10 different 300B tubes in this amp those were the first ones I didn't like.




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Re: DECWARE 300B Amp development thread
Reply #846 - 01/14/23 at 02:15:46
 

So this amplifier has about an hour on it so far configured with the good sounding Chinese 300B tubes, and I'm already into it.  Is it as good as the Western Electric or Cyrotone? No it's not as good but you would never know that unless you hear them side by side.  To get into a groove with an amp after only one hour is a really good sign and frankly if you are on a tight budget these tubes won't disappoint.  If they however sounded like the other ones I tried, you would have thought there was something wrong with your speakers or the amplifier...   This is why we are offering the amp with this lesser expensive option, so that the tubes can be tested in the amplifier and are known to sound right.

We don't have to worry about this with Western Electric 300B tubes which is why we let you save money and buy the tubes directly from them.






 
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Re: DECWARE 300B Amp development thread
Reply #847 - 01/14/23 at 02:17:43
 
Steve Deckert wrote on 01/14/23 at 00:37:50:

The Sarah 300B amp draws 160mA with both WE300B and the selected Chinese 300B tubes.   I haven't had issues with good rectifiers rated at 160mA but if you get a tired one or one that has been thrown around a lot, then expect it to fail and blow the external fuse. Still a favorite is the 5AR4, but I will be shipping the amp with 5U4G because it is rated higher and will therefor be likely to last longer.








Thanks Steve.
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Re: DECWARE 300B Amp development thread
Reply #848 - 01/14/23 at 02:44:26
 
Just as an aside: I can see why Steve really likes the 6N6P in the SEWE300B. I'm using a pair of red tip gold-grid ones right now in my Monoblocks that I hadn't put to use before. I moved to a different 12AU7 in my ZROCK2 and the sound is great--really balanced and "alive." I'll certainly be trying these in my SEWE300B when it arrives months from now.

Looks just like these:

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Re: DECWARE 300B Amp development thread
Reply #849 - 01/14/23 at 12:23:42
 
All in a day's work? Wink

Nice work Steve Smiley

John
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