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  Hammond Chassis covers
Posted by: Sam - 10-04-2020, 10:31 PM - Forum: Personal Projects - Replies (3)

Hi all,

Looking for advice from anyone who has used a Hammond perforated chassis cover and installed carry handles on it.
Having never used one of the perforated covers before, i'm not sure how much strength there is, or how much flex (if any) to expect.

The attached image shows my intent. I'm thinking 1mm thick plates sandwiching the cover to spread the load.
The chassis is 16" x 8". Matching cover is 20ga (0.91mm) thick. Amp is 5W single ended, so not a lot of weight in the transformers.



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  Old Electrolytic
Posted by: George A - 09-16-2020, 09:58 PM - Forum: Power Supplies - Replies (2)

Hi all - I have many, probably hundreds of "NOS" electrolytic caps left over from Polytone's inventory, probably dating from the mid to late 1980's. (They made an interesting tube amp called the Fusion to compete with Mesa Boogie - didn't really pan out for them).

They're nice looking caps - Mepco/Electa 310uf/300V - a couple in series would make a nice reservoir/smoothing leg.

My question - Is there any hope for using these, or am I asking for disaster if I do?  I've read about "reforming" capacitors - does anyone have thoughts or experiences related to this?

Thank you,


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  Hello Everyone
Posted by: Amptroll - 09-10-2020, 08:58 PM - Forum: New Member Introductions - Replies (1)

Hello fellow Forum Members,
    My name is Rob.  I love designing and building valve amplifiers as I assume that most everyone here does.
I have a small company that caters to a small group of musicians in NY, NJ, PA, and MD.  I have a degree in electrical 
engineering but my valve knowledge and experience does not come from my education but from investigating and using valve circuits since approximately 1970 as a HAM Radio operator and of course reading TUT (I own all of them) and for the past 18 months correspondence with KOC. 
     I worked in aerospace industry in the United States for 3 different DOD 
contractors, mainly embedded work for the last 20 years of my career, writing millions of lines of code, mainly in C and 
C++.  Before the embedded stuff, I was involved mainly in the early development of hybrids. Before I obtained my degree
I was an electronics tech so I have a fair amount of diagnosis and repair experience.  
   With all that said; this is a deep subject, which is not just tech but also has an element of an art form.  I look forward to
learning from everyone here and hopefully, I can contribute to other members knowledge and help out with projects, theory, 
construction etc.  One last thing, I was also a machinist for about 15 years, mainly building engines, but also jobber stuff.
One might say, how can you have done all this, well the simple answer is, I am in my 7th decade on this planet (and maybe
more on another).  Humor, is also a very important part of life, never take it to serious, as you won't enjoy it.

    One thing I noticed reading the forum before I joined was the civility practiced here.  I have left others because of the lack of
this aspect, so I thank everyone before hand for being considerate of other members, realizing we all have more in common that not.
Take care and peace,

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Posted by: Sam - 08-22-2020, 09:15 PM - Forum: New Member Introductions - Replies (2)

Hello TUT members,

I'm Sam from Australia. Designer of gravity processing plants for the sand mining industry by day, guitar amp entusiast by night.
I stumbled across the TUT books years ago whilst trying to find out how to mod my Marshall TSL60 online.
After reading some reviews, and having a favourable exchange rate AUD/CAD at the time, i ordered the full set of books.

After getting into TUT i got stuck into the TSL. Swapping the power tubes for 6L6's and taking the speakers out of the open back combo cabnet and making some detuned cabs for them. This was a marked improvement over the original tone, but rather than trying to mess around with the amp any further, i decided i had to build one from scratch. There were plenty of options from TUT3 & 5. I probably should have started with a Champ, or something from TOT, but went straight for the Doppelsonde.
It was a huge learning curve, but the amp turned out just fine. Since then it's had an SB PS kit, SUS kit, and RBX added. The front end now has a dual channel 'Plexi' with a BFX loop.
Awesome amp.

After a few more projects, and lots of tweaking, i got sidetracked with other things in life and haven't built anything new for a long time. Just enjoying the gear i had already made.
2020 saw me stuck at home for a while with time on my hands. Thought i'd start working on a new amp build. And now i discover there's a TUT forum.

Hope to have fun shooting the breeze with you guys, and learning something new, or remebering stuff i forgot.


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  fx loops
Posted by: Adam - 08-19-2020, 11:15 AM - Forum: Preamp Mods & Design - Replies (2)

no one seems to have posted about this so I thought id ask a few questions!

Firstly if I add a ‘Best all-tube loop’ (BATL) in TUT (fig 7-16) if I want to bypass it do I do it a) Completely with relays or b) can i just mute send/return portion?
Secondly, If I have two preamps with their own loops, each channel can have their own send but share a recovery ( like the example in TUT 4 fig. 6-45)

Where would the two signals mix? I’m guessing at the “0” virtual earth point in the BATL? I can mute each loop when each channel is switched in/out?


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  Hi all!
Posted by: Champ81 - 08-11-2020, 11:01 PM - Forum: New Member Introductions - Replies (2)

Hi everyone.  I am from Ontario Canada and just found and joined this forum and glad I found it. Just wish it was sooner.  I have been a big fan of Kevin's stuff for years and used his power scaling and many other amp improvement kits to great success. I am still relatively a real novice at this but managed to build two "ultimate" amps through the kits.  Hats off to you Kevin for the books and which i reference quite often for my builds as well as sharing of important knowledge.

Where is everyone from?

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  Bass Master and compressor
Posted by: sinusoids - 07-17-2020, 06:36 PM - Forum: TUT Q&A - Replies (7)

I'd like to build a TUT3 Bass Master with compression.  Would the TUT2 fig 6-54 Simple Transformerless Compressor work for this application?  Following the tonestack ?

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  Tremolo... a Project To Be! Or not..
Posted by: Strelok - 07-08-2020, 08:59 AM - Forum: Personal Projects - Replies (8)

Hi all!!

Did any of you build the Fender Tremolo in TUT2?

I like the idea of frequency changing with the sweep a lot.
But the LFO made of tubes may not be very efficient, an OpAmp would be much cheaper and smaller.

I have no idea what voltage or current the tube produce to create the sweep.
Maybe I will build it on my prototype board.

Is it worth building thios thing or is the sound just "average"?


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  Distorting reverb tube
Posted by: Tomislaw - 06-26-2020, 03:28 PM - Forum: Preamp Mods & Design - Replies (24)


I'm having a bit of a problem troubleshooting a Fender type reverb - the 12AT7 driver tube output has a tendency to distort the signal. Originally with a bypassed 1K cathode resistor the tube was oscillating wildly. I increased the Rk value to 2,2K bypassed which stopped the oscillation but the top of the signal was still distorted. Removing the bypass cap obviously reduces the gain in the triode and I can make up for that by lowering the Rk value to 470R. At maximum V1 output volume I'm getting 154Vpp signal swing whereas with a bypassed 2,2K Rk it was around 195Vpp. At 154Vpp reverb sounds OK. Voltage drop at Rk is now 4,7V and plate voltage measured cathode to plate is 340V, so the plate dissipation is still within spec.
The signal at the grid is clean and undistorted. There's a 430K grid stopper and a 680K grid leak. Reverb transformer sees 360V.

Is there any other way of fixing the problem with the reverb driver?


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  Dopplesonde fixed bias
Posted by: sinusoids - 06-06-2020, 10:55 PM - Forum: TUT Q&A - Replies (17)

A. I built a pair of Dopplesondes with 5F6 preamps.  All is operational except the fixed bias.  As built, it had -20V B-.  With Cathode bias switched in, B- was -340V.  After trying lower R for the Bias supply I found with only 56k R, the bias was -94V with one set fixed and-56V with both sets fixed.  I now have one 56k R and 22uF C dedicated per tube set.  Both tube sets now have -56V max bias each.  They still interact quite a bit.  I can set bias for both V3+4 and V5+6 but if I have both in fixed bias the idle current for both increases quite a bit.  Any guidance here?  These current values include a switch to the grey 115VAC PT input tap – originally had used the black 125V tap.

B. Is my TUT bio editable?  I did not know that info would be included with every post – can I delete the bio for new posts?

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Come in where it's warm!
A warm welcome to tube amp modding fans and those interested in hi-fi audio! Readers of Kevin O'Connor's The Ultimate Tone (TUT) book series form a part of our population. Kevin O'Connor is the creator of the popular Power Scaling methodology for amplifiers.
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