stereo SE kt88 build ... abdellah diyaudioprojects design

[jmillerdoc]

Ok, I say Uncle.....you win the look like a Chevy V8 contest....

 

[jmillerdoc]

It is ugly isn't it though???

 

[Nikon1975]

Jeff, the switches come from one of the trillion shops in Akihabara. Living in Tokyo, to stops from the electronic town has the advantages that you can find many things, but you have to dig yourself, and sometime is preety difficult to understand what you are buying, if, like me, you are not experienced and don't speak Japanese. They are rated 250 V 3 A.

I bought all the component there, but I think for the next build, I will put an order at mouser or digikey, at least I know what I am buying.

Only now I noticed that my power supply comes up like in the first picture, what do you think ? No good ? I could add a 100 uF at the second cap, and this should make it more smooth. It's too bad if I just put a 100uF unicom in parallel with the 47 uF film ?

A 100 uF film, first will cost me other 50 $, while I have the electrolitic, second is 12 * 4.5 cm, not sure I can stick it inside.

There is nothing to be done, if you make a mistake in the initial phase, you struggle all the way to correct it.

BR,

Davide

 

[88man]

Hi Jeff, construction on my amp has been on hold for the past 3 weeks. I hope to finally assemble the SE KT88 by the New Year as I have 2 long weekends in a row.

If all goes well, then I'll start on the Derrick Walton 300B SE amp in January - I've bought most of the parts except for the trannies. I can't find a good Mullard GZ37 for that amp. Are you planning on using the Universal Angela PTX or Plitron? I'll need another pair of James 6123HS OPT for the 300B too, if the SE KT88 turns out well. If not, I'll use the James OPT on the 300B project. When are you placing the order for vt4c.com?

As I am getting more familiar with tubes over the past 4 months, I am tempted to get a cheap Mingda amp someday and do modifications change to filtered DC filament supply, Elna Cerafine PSU caps, Blackgate bypass caps, Audiocap coupling caps, tube roll, PRP resistors, etc.

 

[jmillerdoc]

I have settled on the JEL SE300b Deluxe monoblocks as the next build. For those interested I am going to pay the $120 design fees in total to have Edcor develop the chokes and power transformers for this amp. I am having them develop an identical power transformer to the Angela Universal. I don't know the cost yet but it will likely be around 95-105 USD. I imagine the chokes will run around 30-40 too. They have not yet made these but their design fee is $40 per item designed. Once the design is made, subsequent purchasers will get to buy the items at cost (no design fee). I love Edcor iron, it has performed flawlessly for me to date, I have used their iron in just about every project I have done. The SE KT88 here is simply perfect with their OPTs, a bargain at $83 a piece.

It will be about 45-60 days before the transformers will be built, I will ask when others may order after I have paid the design fee. I have spoken with a couple of you via email about building this amp, if you want a great deal on the iron from Edocr, let me know and I will tell you when they will take subsequent orders.

My next order to VT4C will be about mid january so just let me know what you want about 1 week in advance.




Jeff

 

[jmillerdoc]

Only now I noticed that my power supply comes up like in the first picture, what do you think ? No good ? I could add a 100 uF at the second cap, and this should make it more smooth. It's too bad if I just put a 100uF unicom in parallel with the 47 uF film ?

A 100 uF film, first will cost me other 50 $, while I have the electrolitic, second is 12 * 4.5 cm, not sure I can stick it inside.

There is nothing to be done, if you make a mistake in the initial phase, you struggle all the way to correct it.

BR,

Davide

I think you modeled it wrong, you need to place the current tap before the 5H for the KT88's, you have it after the 5H choke in the model, this is not correct. Make this change, it will fix everything you see. It is a mofdeling proble, not a construction problem.
Jeff

 

[jmillerdoc]

If all goes well, then I'll start on the Derrick Walton 300B SE amp in January - I've bought most of the parts except for the trannies. I can't find a good Mullard GZ37 for that amp. Are you planning on using the Universal Angela PTX or Plitron? I'll need another pair of James 6123HS OPT for the 300B too, if the SE KT88 turns out well. If not, I'll use the James OPT on the 300B project. When are you placing the order for vt4c.com?

88man,

Have you seen this schematic yet? SE300B classic and DX

It is the schematic the Walton came from originally. The SE 300B Deluxe has a bit more flexibility. The 76 can be subbed with a 27 or 56, and a few others. These tubes are fairly easy to come by and I have bought a pair of 76 and 27 tubes recently for about $16-18 a tube for used or NOS American glass.

I recently put a request in to Edcor for a replica for the Angela Universal. If all goes well they will be able to produce this transformer Edcor style and for likely $10-30 less than the Angela iron sells for. I will know in a week or so.

If We put together an order to VT4C for a couple of pairs of James 6123HS, the shipping alone will bring the cost up to the same as TCTUBES.com price before shipping but there will be room for extra stuff from their site which is very well priced (Blue Velvets for $8, etc...) I have not yet used James but soon will have a 2A3 Clarion Hagtech design put together with these OPTs. After this I will decide between the James and Edcor for the OPTs on the 300B.

I have been having a problem sourcing 47uF Motor run caps, anybody know of a place to get these around 440 to 500VAC. Angela has 15, 30, 40, and 50's but no 47uF's.......

Jeff

 

[seel34]

because my b+ is a bit low [328 on the plate ] i was thinking to get a other transformer , now i found 1 second hand on the internet ,wich is very suitable
only it doesnot have 5 volt for the 5u4 ,it has 6,3 volt with 5 ampere
is it posible with a resistor to lower it for the 5u4 to 5 volts while the others tubes keep 6,3 v ? grtz ko

 

[88man]

Jeff, since you are ready to build the 300B SE, start a new thread and I'll chime in as catch up to building it.

Questions:
1. Which JEL 300B SE amp are you going to build exactly?...
2. Monoblock or Stereo?...
3. What will be the Edcor TX and choke design values because I might still go with Walton's 300B because I only have matched NOS Sylvania 6SN7GTB's?...

Pending on the values, I am in for the Edcor design PTX and chokes - better choice than Hammond!

I have the Hammond iron for the SE KT88, and for me, it looks like junk - very thin and frail wiring. I've heard it's also prone to buzzing, noise in refined applications - so I am mounting them to the chassis plate with rubber washers and grommets for electromechanical isolation. However, there are those who are perfectly happy with Hammond. I'll see how it turns out...

I should have gone with Edcor in the first place even with their blue color and all, it's better spec'd too with 200ma instead of 175ma, which doesn't leave much for dynamics or headroom. Sensing that Hammond doesn't have a 200ma 375V PTX in their line up, all of a sudden, they've listed the 273BX as 201ma (1 ma better than Edcor) without any without any design change to the transformer. I emailed the HQ in Canada to be sure. Even their OPT are not spec'd 20-20khz, and bass is where it's at with OPT. I am with you, Jeff - EDCOR!

This is where I got my ASC motor run caps - inexpensive and they sell mounts too. I think the 47uF for the PSU is for an arbitrary value for polypropylene or electrolytic caps. I am using the 50uF ASC motor run caps as they are well within the 10% tolerance anyway. Here is the link:

ASC Capacitors - X386S-50-10-440 - Allied Electronics

They even have the 7.5uF ASC that Derrick was trying to find, and ended up using two 15uF...

 

[jmillerdoc]

Here is the new thread started for the 300B build for those of you interested.....

http://www.diyaudio.com/forums/tube...b-jel-walton-builders-thread.html#post2023826

Jeff

 

[Nikon1975]

Models

Jeff,

Actually the model is exactly how I wired it? The two LC filters are before the KT88s.

D.

 

[Nikon1975]

Jeff, did you try the current regulators ? How do they sound ?

D.

 

[Nikon1975]

I noticed that many people prefer the EL34 over the KT88, so let's give them a try. Any reccomandation for particular brands ?
I heard the EH are good, but Tungsol EL34B could be better.
BR,

Davide

 

[jmillerdoc]

Jeff,

Actually the model is exactly how I wired it? The two LC filters are before the KT88s.

D.

You will indeed have problems with this arrangement. The B+ tap for the KT88 should come before the second LC filter. The second LC filter is for the driver tubes only. Does it work like this? I would be surprised it sounds well at all with both LC filters before the KT88s. I haven't looked closely at the voltages but they should be off the way you have it wired. If you look back at the DIYaudioprojects.com version of this schematic you will see that the second LC is shown only on the circuit and not the power supply indicating actually 2 separate second LC filters, one for each driver (although I don't think that is how he built the circuit as I recall). Try pulling the B+ for the drivers before the second LC filter and see how it sounds, I think you will find a much better sounding amp.

No, I have not yet tried the CCS, I got carried away with Christmas shopping and completing some music boxes I was building for my 2 nieces. I won't be home until Monday, I will try them probably on Tuesday morning. I am anxious too to see how they sound.

Can anybody tell me if the ASC 50uF 440VAC motor run caps at Allied are the oblong oval kind or are they round? I just bought 3 of these with free shipping new on eBay for $29 but they are all the oval kind. I realized this after I bought them. I am not even sure if they make a 50uF 440VAC that is round in the ASC line of caps.

Jeff

 

[jmillerdoc]

Nikon,
I would also change the cap values around too if you pull the B+ before the 5H, swap the two cap values before and after the 5H. This will be much closer to the connection I have made. Good luck.

 

[Nikon1975]

Jeff, no problem for the switches, how many do you need ? I think they costed around 4 $ each, they are 3 position one way, so you need one per channel.

Why you think that the double LC filter does not work ? My goal is to reduce the ripple on both the taps. With the simulations I figured out that having CLCLC was much more effective than CLCRC. I get 397 V as my B+.
I don't really like the voltage to oscillate anytime there is a current request. but If I understood how the system works the current demand should not exceed +10mA for both channels, and a cap configuration as 10uF-47uF-147uF instead of 10uF-47uF-47uF should fix it. It makes sense, but maybe there is some effect that I am ignoring.

I have the constrain that I have 3.5 cm holes on the plate, so it means that I can fit either 100uF Electrolitic caps or 47uF film caps. I thought that adding the second choke I could fix the problem using tha caps I have.

D.

 

[jmillerdoc]

Adding chokes does more than just reducing the ripple, it changes the power supply entirely. Changing the power supply entirely changes the amp entirely.

How does the amp sound in the current configuration?

What is the current rating of the second choke you have added to the filter?

If you went with 247uF (10u/10H/247u/B1+/......)
you would get a ripple of around 0.06v, should be enough. I am just concerned with the final result you will have by adding the second choke before the B1+. If it works than you can't argue with results.

Jeff

 

[seel34]

I noticed that many people prefer the EL34 over the KT88, so let's give them a try. Any reccomandation for particular brands ?
I heard the EH are good, but Tungsol EL34B could be better.
BR,

Davide

hi davide
if you can get your hands on a pair of old brown based tesla,s techoslowakia produced not modern jj,s it about the best you can get except metal based philips but there price is of the scale
from the newer produced tubes i like winged c produced in sint peterburg the best [this is the former "real SVETLANA " factory ,nowadays the svetlana brand is produced in the refector factory in saratof and the quality is absolutly n ot as the origenal svetlana out of sint petersburg ,nowadays produced under de brand winged c it sal a bit confusing ,it started when the american new sensor compagnie ,bought the names svetlana,mulard ,eh etc ] and started to produce them in the refelector factory in rusia and sel them under the names of tubebrands with a good reputation
grtz ko

 

[88man]

Jeff, the 440VAC 50uF ASC motor run caps are ROUND. That's what I am using.

 

[88man]

Just to be sure, I had a few questions:

1. Is it better to use a shield instrument cable for the input signal wires from the RCA jack to the 100k Alps as shown?...
2. Should I use a separate shielded cable or wire for the neg RCA input terminal?
3. Where should I connect the shield around the cable to - RCA neg terminal, nothing, or RCA terminal star ground?...

Length from RCA to 100k Alps is 2.5in. and the PSU is about 1ft away on chassis.

Thanks