[JoshK]

Thanks Mike.  What kind of epoxy would you use?  I might give this a shot. 

[mgalusha]

Thanks Mike.  What kind of epoxy would you use?  I might give this a shot. 

Something with a slower cure time so you can get it all aligned nicely before it sets up. You might check your local boat or woodworking store. I didn't like the Gorilla glue because of the expansion.

I cut the pieces a bit oversize and used masking tape to hold them together at the edges. This was of course only to keep them in alignment, they really want to slide around when coated with glue. I sandwiched them between two sheets of MDF and plastic wrap and piled every plate of my son's weights on the MDF plus anything else heavy I could find. I didn't have enough clamps at the time to do a proper job. To be really sure they don't move around you could drill holes through the MDF at the perimeter of the plates like a jig. Now that I think about it, those would help to clamp as well.

I picked up some plastic Bondo spreaders from PepBoys for a couple of bucks. These work great for spreading the glue and are cheap enough to toss when you are done.

After it was all cured I clamped the completed lamination to my workbench along with a hardwood straight edge and used a very fine tooth blade in my jig saw to cut it to size. It came out pretty smooth and a little work with a flat file produced quite a nice edge.

[andrewbee]

JB Weld is great stuff. Get the regular one and not the quick version.

[JoshK]

Like this one?



or maybe this is the better option?

[jeffdavison]

I'm still going back and forth on what to drive the KT88 / 6550 with.

I like the 6H30 I mentioned earlier, but I've come across some designs for drivers for some 300b and 2A3 amps that look to be alternatives as well. They probably could work directly for the KT88 in triode as is.

A respected 300b amp that uses the 6n7gt:
http://www.angela.com/catalog/how-to/300B.Schematic.gif

A translated (Bablefish) dutch amp called the “Centurion” uses a 6SL7gt's up front:
http://babelfish.altavista.com/babelfish/trurl_pagecontent?lp=nl_en&url=http%3A%2F%2Fwww.triodedick.com%2Fcenturion.htm


I have a plethora of RCA JAN 12SX7GT's that I can use in place of the 6SN7's (running 12.6 for the filaments) and I have a few pair of Mullard ECC35's, Tung-Sol 6SU7GT's, RCA 5691's and JAN VT229s, as well as the Rusky 6H30's.

Got some Mullards GZ34's, so I'll use one for a tube based power supply.

I just place an order for the output Iron for a set od SAC-Thailand Silk S325 transformers. The measure and spec nicely and have gone through the forums on their sound and build quality. They aren't the cheapest, a bit more than the James, but less than the Tangos, Tamuras and Hashimotos.  I built a TVC using their magnetics and couldn't be happier with them. I purchased them through DIY Supply in Honk Kong. Brian (the proprietor) has a forum in AA I believe.
Here;s the links to the output transformers:

http://www.sacthailand.com/Transformer_Output.html
http://www.sacthailand.com/Transformer_SilkS-325.html

As soon as I figer what the drivers will be, I'll get my power transformer.


JD

[Freo-1]

I'm still going back and forth on what to drive the KT88 / 6550 with.

I like the 6H30 I mentioned earlier, but I've come across some designs for drivers for some 300b and 2A3 amps that look to be alternatives as well. They probably could work directly for the KT88 in triode as is.

A respected 300b amp that uses the 6n7gt:
http://www.angela.com/catalog/how-to/300B.Schematic.gif

A translated (Bablefish) dutch amp called the “Centurion” uses a 6SL7gt's up front:
http://babelfish.altavista.com/babelfish/trurl_pagecontent?lp=nl_en&url=http%3A%2F%2Fwww.triodedick.com%2Fcenturion.htm


I have a plethora of RCA JAN 12SX7GT's that I can use in place of the 6SN7's (running 12.6 for the filaments) and I have a few pair of Mullard ECC35's, Tung-Sol 6SU7GT's, RCA 5691's and JAN VT229s, as well as the Rusky 6H30's.

Got some Mullards GZ34's, so I'll use one for a tube based power supply.

I just place an order for the output Iron for a set od SAC-Thailand Silk S325 transformers. The measure and spec nicely and have gone through the forums on their sound and build quality. They aren't the cheapest, a bit more than the James, but less than the Tangos, Tamuras and Hashimotos.  I built a TVC using their magnetics and couldn't be happier with them. I purchased them through DIY Supply in Honk Kong. Brian (the proprietor) has a forum in AA I believe.
Here;s the links to the output transformers:

http://www.sacthailand.com/Transformer_Output.html
http://www.sacthailand.com/Transformer_SilkS-325.html

As soon as I figer what the drivers will be, I'll get my power transformer.


JD

What about 5687?

I'm using them with great success. They are plentiful, and drive 6550's just fine.

In fact, they may be one of the best driver tubes for 6550 out there  aa

[jeffdavison]

I have about 20 of the SX's and the same of the 'sl derivitives and 6 6h30's.. would rather not buy more tubes. Plus Iv'e heard good things of these for triode drivers. I'd rather put new money in new iron.

JD

[JoshK]

The 6H30 is somewhat similar to the 5687 anyway.

[JoshK]

So I ordered a thin sheet of copper for the top plate.  I was going to use my copper shingles but then I would have had to piece a few together to be big enough to cover the top plate, so I'll save them for another project.   

I had done some research earlier on creating an oil rubbed bronze look out of copper.  Its a patina process and uses "Liver of Sulphur" to chemically blacken the copper. I ordered some of the LOS and some wax meant for creating a hardened clear finish over the top.  I've just always thought an oil rubbed bronze look would be killer for a tube amp and I've never seen it done before.

This project left small budget territory for me a while back.  Oh well, its a fun learning experience.  Hopefully, I will develop some artistic skills for making aesthetically pleasing amps.  I have a small copper plate for my Squeezebox power supply to practice on, so I don't botch the expensive larger piece. 

No matter how many times I've made an order to mouser and other suppliers for the last few missing pieces I always forget something.    That is what happened and this weekend I wasn't able to finish the last few hole punches for the plate layout. 

[andrewbee]

The JB weld in the bottom picture is the one you want, the one in the tubes.

Andrew

[jeffdavison]

Finalized the output stage I'll be using, Basicaly the TubeLab's Simple SE with a little twist....
I'll be putting in a switch for Triode – Ultralinear – (like Alex Gendrano's http://diyaudioprojects.com/Tubes/KT88/ version of Mikael Abdellah's KT88 SE Tube Amplifier )
The switch will be a 3 way switch to afford a Pentode position as well. I've seen a schematic of it on the web but can't seem to find it to paste here, but anyhow... the pentode connection on that schematic is taken from the B+ of the output transformer. Instead of taking the tap from there I'll be providing B+ from it's own filtered tap from the power supply. (lifted from Audionotes KIT2).

Speaking of Audionotes KIT2, I will also be lifting their use of a seperate input and driver stage.

For the driver stage, I'll use the 6H30 that I was thinking of previously that's a darned good driver for the KT88. It'll sport the 10M45 CC. (The KIT2 specs a 12ax7 – since I don't need the gain I'll go for the 6H30)

For the input stage, the KIT2 specs a 6SN7 but with the volume pot between the input and driver stage. I have a spare 100K Goldpoint stepped attenuator laying around to use. I'm going to put a 12sx7gt  for the input ( as I have a sh*t load on hand ) and get 12 vdc there (probably with a voltage doubler from a 6.3 vac tap or I just may go DC on all the low level tubes (both the the SX and 6H) -, maybe a separate transformer and a couple of rectifers.) I'll raise the ground also. The 12sxygt will also sport 10M45's. I was thinking of putting 6SU7GTY's or ECC35's in the input, but I don't need that much gain. I like the sound of the ECC35, the 6SU7GTY's have matched section, and it's also a fine sounding tube, but the 12SX7 is no slouch when it comes to sonics.

Here's the PDF's of Audionotes KIT2 circuit and power supply....

Circuit schematic: http://www.audionotekits.com/PDF/Schematics/Kit2_AudioCircuit.pdf

Power supply schematic: http://www.audionotekits.com/PDF/Schematics/Kit2_PowerSupplies.pdf

Now I can start designing the power supply, finally..

JD

[JoshK]

The JB weld in the bottom picture is the one you want, the one in the tubes.

Andrew

Thanks.  I picked some of that kinda up at the Home Depot yesterday.  I'll give it a shot.

[jeffdavison]

Some very nice work in this German SE.
Interesting the constant current source for the power tube.
Wonder how to use this for a switchable pentode/ultrlinear/triode mode. The IXYS 10M90's look like they can take the voltage.

http://www.jogis-roehrenbude.de/Leserbriefe/Michael-Dieckmann-KT88-Amp/KT88.htm

Guys.... doing some modeling to finalize my power supply on PSUD...  what are you all using for rectifiers?
flip flopping from an indirect heated GZ34/5AR4 to a direct heated 5U4G.

I think I'm going to "Hybridize" a rectifier tube:.. schemo is a bit down on the page.

http://www.audiodesignguide.com/my/se.html


Jeff

[JoshK]

It's what some of us call a hybrid Graetz bridge.  Its a good thing from what I can gather.  Best of, or most of, both worlds. 

[JoshK]

Well I spent a good deal of time working on patinas today.  I am hoping them come out.  The Potassium Sulfide came out like steel blue instead of the bronze-brown-black color.  I tried a couple other patina formulas, including Ferric Nitrate & Pot. Sulf. iirc, and that one didn't look so hot either (purplish and uneven).  I am hoping the Florence Brown formula, Ferric Nitrate & Ferric Chloride, turns out good...it takes a few days.

Its a bit harder in my experience than it is made to sound.  That is so far.  I cut up a bunch of smaller pieces so I can experiment with different formulas.  The neighbor is an artist and he loaned me a book on patinas, but it doesn't explain much more than I found on the internet, but does offer quite a few more formulas. 

[nodiak]

How can I not add...In college metal sculpture classes we were told that urine makes a green patina. Works great and was a good laugh when the instructor asked my friend how he got the great patina while he was holding the sculpture...

[JoshK]

yeah, ammonia is a key part of the green patinas. 

[jeffdavison]

Initial layout.

hope they post here....

http://www.audiocircle.com/index.php?action=gallerylastup&cat=0&pos=1
http://www.audiocircle.com/index.php?action=gallerylastup&cat=0&pos=0

etching my power supply boards. still have a couple more of the B+ cap boards to etch.

there are two rectifiers ... going a rectifier per channel... Hybrid with Cree Shottkys and each with it's own 5v x former (both sharing the 360  - 360 from the toroid)

JD

[jeffdavison]

A little more progress..

got my power supply and hybrid rectifier pcbs etched and stuffed... laid out using AutoCad and etched using the laser toner transfer system. This makes for very easy DIY boards. Finished up the 12v and 6v regulators for the12SX7 and 6H30 filaments. Waiting for the potting epoxy in the cover for the toroid power traffo to cure - takes a couple of days. Made up a module that holds the 12sx7 and 6H30 tube sockets on a subassmebly so I can hard-wire the audio signal circuit from input to output. This will bolt up to the underside of the top plate and let the tubes poke trough.

Bolivian Rosewood on the way for the chassis and in about a week I'll have the top plate I designed from Front Panel Express.  This weekend I'll bench test the power supplies and see if they match up to PSUDII's predictions.. Also for the CCS's for the input and driver filiments, I'll be using cascoded IXYS 10M45s's, thats 2 per each triodes B+. Made up some very neat little CCS's boards for this.


JD

[aerius]

It's what some of us call a hybrid Graetz bridge.  Its a good thing from what I can gather.  Best of, or most of, both worlds. 

I'm using them in my headphone amplifiers, except with TV damper diodes instead of the usual 5XX4 rectifier tubes.  I'm very happy with them, quiet, solid, works great, and they have a nice gradual turn-on so the audio tubes don't get whacked with high voltage jolts when they're cold.