[johnjen]

So along with everything else that is changing with all of these mods and builds, I am re-discovering just how persnickity getting and keeping horns aligned and aimed can be.
Moving the horn by 1/2in (or less) in either the x or y direction let alone the z axis and in a near field setting where these kinds of small changes have less impact on directionality etc. is very revealing.

It reminds me of the days way back in the 70's when we aligned horn speakers in a large 'auditorium' and how we could make such small alignment changes and make up to 10dB (or more) acoustic changes to what the audience heard.
And that was with throws of 30-40-50 ft. or more.

Yeah horns can be amazingly sensitive to setup.

JJ

 

[gefski]

So along with everything else that is changing with all of these mods and builds, I am re-discovering just how persnickity getting and keeping horns aligned and aimed can be.
Moving the horn by 1/2in (or less) in either the x or y direction let alone the z axis and in a near field setting where these kinds of small changes have less impact on directionality etc. is very revealing.

It reminds me of the days way back in the 70's when we aligned horn speakers in a large 'auditorium' and how we could make such small alignment changes and make up to 10dB (or more) acoustic changes to what the audience heard.
And that was with throws of 30-40-50 ft. or more.

Yeah horns can be amazingly sensitive to setup.

JJ

Yep, low frequency wavelengths can be longer than the listening rooms most of us have!

 

[johnjen]

Say there gefski.
Yeah and with the extended low end I look to achieve, MUCH longer wavelengths, as in 20Hz is ≈15M meters or over 9300 miles and my goal is to reach 15Hz which is over 12K miles long.
I don't think I'll have ANY problems with standing waves at those frequencies.
hahahahahahahah..

And in other news…

I was THIS close to getting my Hpre-amp which I have now nicknamed the Purp-Amp back online and operational.



Now I have to wait for more repair parts to arrive since one of the solder tabs on the 9pin tube socket just sheared clean off.
And I need to track down why it's slowly popping fuses.

And I was this close to listening to tubes again.

Such is the way of tube circuit development.

Happy 4th everyone, I sense it will be a celebration to remember.

JJ

 

[johnjen]

A couple of additional 'glamor' shots.
Now with mockup labels.







Next up is the back panel.

JJ

 

[johnjen]

And 2 shots of the rear…







Right now I'm fussing with the knobs, fixing the nicks and chips in the paint so they look all purdy and just make ya wanna grab and twist em…
hahahahahahaha

JJ

 

[johnjen]

So a status report…

The Purp-Amp is up and running, and new 71A and 6BQ7 tubes have arrived, which should provide considerable improvements over the development tubes.
It has been 'strapped' into HP-Amp mode since the 'Mode Switch' just didn't work out very well.
But converting it into a Pre-Amp is very easy to do, so the functionality remains, it's just the click of a switch, has been replaced with a bit of fussing with a few wires etc.

And in other news we have been working on the 45 amp and have found a combination of design approaches that work quite well together, which translated means it's performance has now exceeded what prototype #2 delivered.

And we are now working on the wood boxes for the cases for the CBB-26 Pre-Amp and the 45 Amp.
The CBB-26 will use Tennessee Cedar with beautiful red/pink/purple color accents in the grain.
The 45 amp will be Douglas Fir with tight delicate grain.

And the CBB-26 circuit development continues as we try different design approaches, to ensure we reduce the noise floor as much as possible, keep the circuit as simple as possible, yet keep the SQ maximal and the usability flexible for future uses.

I'll post some pictures of the woodwork after we reach a suitable 'look' for a glamor shot or 2 or 3 etc.

JJ

 

[johnjen]

We currently are working on the 45 amp and have reached a new plateau.

Of course it looks a bit 'rough' around the edges and is not ready for 'prime time', but SQ wise, is revealing new levels of performance, and we're not done yet.



And today we added walnut as a 3rd type of wood to use for these cases, and all the wood for the cases is trued and rabbited and ready for the final assembly and finishing.

JJ

 

[johnjen]

So the cedar base for the CBB-26 Pre-Amp has received it's 1st coat of Tung Oil and is looking good.






Which means soon we will be able to start to build the circuit itself.

JJ

 

[johnjen]

This will be a short update message, and I'll post pictures of the boxes and prototype amps mentioned below, later.

We have applied the final finish coats to the cedar box and the 2 walnut boxes.

The 45 amp is still undergoing design and layout considerations.
Currently it looks like the 45 amp will be 2 monoblocks using the 2 walnut boxes, instead of a PSU box and an analog box.

And we are looking to build a 'hold over' 4th prototype 45 amp before the 2 monoblocks.

AND we just built another power amp for speakers using 6L6GC or 350C output tubes with a 6GQ7 driver, out of our 'spare parts bin'.
It sounds WAY better than we had anticipated so we'll dial it in and use the 2nd cedar box we just made.

Of course all of these plans are subject to change at a moments notice, as new designs and components are tried and refined.

JJ

 

[Tjj226 Angel]

This will be a short update message, and I'll post pictures of the boxes and prototype amps mentioned below, later.

We have applied the final finish coats to the cedar box and the 2 walnut boxes.

The 45 amp is still undergoing design and layout considerations.
Currently it looks like the 45 amp will be 2 monoblocks using the 2 walnut boxes, instead of a PSU box and an analog box.

And we are looking to build a 'hold over' 4th prototype 45 amp before the 2 monoblocks.

AND we just built another power amp for speakers using 6L6GC or 350C output tubes with a 6GQ7 driver, out of our 'spare parts bin'.
It sounds WAY better than we had anticipated so we'll dial it in and use the 2nd cedar box we just made.

Of course all of these plans are subject to change at a moments notice, as new designs and components are tried and refined.

JJ

Its a 6CG7 tube input. A 6GQ7 tube does not exist as far as I know.

 

[johnjen]

D'oh, yeah well, that one…

And we hit another lick on the 6L6GC amp tonight using my HD800-Jmod's even though it's really a speaker amp.

MOAR later

JJ

 

[johnjen]

So I'm in the re-build/stabilizing the circuit and its parts for the 6L6 speaker amp, so that it can be housed in a cedar box and look and sound all purdy.

Here is a before and during, set of pictures.
Today I installed the gold colored, panel mount 25w resistors, which just about completes the power supply portion of the re-build.

I have 5.25" of height and that choke stack uses it all with ≈ 1/8" to spare.
Next I have to drill holes and mount the input xfmrs, the xlr connectors, and speaker cable binding posts.
These will all go right in front of the tube sockets, with the grey square input xfmrs mounted on top.

Here is a shot of the amp running and several parts 'hanging out' during the initial prototype phase.



Here is the amp today with the choke stack and the big non-polar located more or less where they will be mounted.
Also the input components are placed where they will fit, but the input xfmrs will mount on top.





And here is a shot of the top.
It's kinda a poor shot but this puppy is heavy and until I get it in its case it is a bit awkward so it only rests in a few positions.



It has 4 tubes, 1) 5AR4 rectifier, 1) 6CG7 dual triode driver tube, and 2) 6L6GC output tubes, running in a direct coupled, choke loaded, LED biased, ultralinear Set configuration, at 375Vdc and 60ma.
It's a What Amp design, and we're using 'parts bin' components and it supposedly makes ≈ 5watts/ch or perhaps more.
And after 'tightening' up the wiring as well as stabilizing the thermal load shedding, which is still in process of being tweaked, this 'new and improved amp' should exceed what I heard previously, on my 800's, not to mention our very efficient horn speakers.
Which also have a tweak just waiting to get installed as does the purp-amp.

But 1st I mean to finish this speaker/headphone amp.
And when the box is ready and when the amp is fitted, I'll post more 'glamor' shots.
This 2nd box looks equally as good as the 1st one we did.

JJ

 

[johnjen]

So today I spent all day installing the input section and finishing the wiring.

The amp is now ready for a final inspection and test power up.
But I'll do that tomorrow when I'm fresh etc.

In the mean time here are a few more pics of the build.

This is the analog section.




Here is a top view



Tomorrow I'll see if I can fit the amp to the cedar base and of course take some pics..

JJ

 

[johnjen]

It's ALIVE, Alive I tell you…

After checking the circuitry and running a few voltage tests it's up and playing music.




Some of the circuit is running hot besides the tubes themselves, as in there are a couple of voltage drop resistors on the cathode of the 6L6's that are in the 270ºF range.

And today I applied the 2nd coat of shellac to the cedar box, so tomorrow I might get a chance to mate up the base to the top plate for a more finished look.
And right now I've got my 800's wired into this amp and it sounds very nice indeed.

JJ

 

[johnjen]

So I have tweaked the 6L6 amp with a few refinements, such as loading the output xfmrs with 8Ω resistors (for use with my 800-Jmods), added an 'on' light, rewired a few of the circuits to help lower the s/n and have continued to fuss with the finish of the box.

The latest glamor shot.


And this, like the CBB-26 pre-amp, started out as parts bin, slap dash, throw the prototype together in a day, project.

But both turned into keepers all in their own right.

JJ