Kalart-Victor 70-15 Reel to Reel Audio Amp, Re-Opening the Case

[Platefire]

If any of you recall, we were having a good conversation several years back about this amp that I scored in the middle of my Plexi project. I had to get off of the Rabbit run after the Kalart Victor amp to finish my Plexi Project. Somehow I never got back around to the Kalart but I'm looking at opening this old case and considering my possibilities of best way to guitar amp it. Here is a link to that old conversation:
https://el34world.com/Forum/index.php?topic=20831.0
I was contacted in 2022 by strmusicman of this forum from Greece. He wanted me to check out his Kalart Victor70-25 (PP 6L6's) amp project that he converted. So I did and was impressed that he used the old board, the Active Baxandall Tone Circuit and basically transferred the old circuit into a new chassis. Also added an extra gain control and volume. I'm attaching strmusicman's pictures he sent me. I'm considering doing the same thing to minebut I want my input and controls on the left instead of the right kinda laid out like a fender. His is opposite. Please check it out and see or say what you think! Platefire




 

[sluckey]

His amp is laid out just like a Fender. Gotta remember, Fender liked to turn their amps upside down!   

[Platefire]

Then that will go right along with my up-side down thinking

I must say, it's great to have a project to be thinking about again.


sluckey I've been looking at that CAD/drawing program you use(can't remember the name) that you didthe Vibro King with and wondering how much expense and learning curve required to get into it. I got useto laying out my projects in full scale on the computer before I retired using Bently Micro Station but nowI haven't got access to that. If it's too big of a curve, I can always lay it out full scale on a large sheet of paperwith a scale, triangle and pencil. Platefire

[sluckey]

sluckey I've been looking at that CAD/drawing program you use(can't remember the name) that you didthe Vibro King with and wondering how much expense and learning curve required to get into it. I got useto laying out my projects in full scale on the computer before I retired using Bently Micro Station but nowI haven't got access to that. If it's too big of a curve, I can always lay it out full scale on a large sheet of paperwith a scale, triangle and pencil. Platefire

The program is Visio. My version is Visio Pro 2010. I've been using it since version 1.0, about 35 years. Back then all it could do was organizational charts and flow charts. Really come a long way since then. It can do much, much more than the electronic drawings on my website. I quit upgrading when I retired in 2012.

[bmccowan]

I love the optics of that skyscraper of a PT with the dinky open frame OT. The builder did a neat job. I am curious about the resulting voltages and the sound character?

Fender liked to turn their amps upside down!

Had to laugh thinking about a stupid thing I caught myself doing a few years ago. I had laid out a board, soldered the leads, placed the components, and then thought, "you dumb shit - you've got it all backwards." I started to redo it all when I remembered that it was to be turned over. I must have forgotten to eat my fruits and vegetables that day.
 

[Platefire]

I've built several 5E3's in the Hammond chassis, top cover(cage) and bottom plate as shown below. This requires you to install the board to the roof of the chassis. Talk about thinking upside down:>) Truly I'm thinking about doing the same thing on this one----because it bothers me having an amp with the tubes sticking out the top exposed without any protection---but maybe I can get over it or make a combo out of it.


Regarding strmusicman's amp, I sent him a PM because I wanted him to talk about his amp of how it works and sounds but I never got a response. He might chime in later

[bmccowan]

Beautiful work. I build most of my amps tubes up. I don't like those bear trap tube grippers. But I also don't like the cages that hide too much of the tubes (I know; grumpy old man.) I'd like to come up with some kind of unique tube cage, but so far no great ideas.

[Platefire]

  Thinking out loud. I'm still pondering a direction to go on this build. I am pretty impressed with the sound of existing circuit for use with guitar with the exception of the humm. i couldn't ever find it. Even tried to tag in some good filter caps to see if that helped, it didn't. I was rather impressed with the active Baxandall. It is very responsive and brings in or cuts good sounding treble and bass as I liked. As far as re-using the existing tone stack as is, it has a special component that is a multi-component built all in one piece. On attached schematic showing tone stack, the special component includes everything within the dashed lines. If this component ever went bad it would be impossible to replace as is plus the stacked tone and bass pots, another rarity. If you look at the attached picture the orange looking component on the back of the tone stack is that multi component right under the vol pot/power switch. Kinda been wanting to hear from strmusicman who used the existing circuit of the Kalart 70-25 but haven't heard from him even though I have sent two PM's.
 
  So even though I haven't decided, my experience and better judgement tells me to build something with mostly  new or NOS parts. That way if there is a issue, it will be easier to track down and fix. I'm a tight wadd, so always looking for ways to save money but hay! this could be my last build. That's what I thought on the Plexi and here I am still. Long as the Lord holds me up--I'll keep Pushing on and Amping

BTW--Those red markings on the schematic is PRR's Estimated Gain at different points. You would have to
get him to explain it, I can't

[strmusicman]

mr platefire happy new year.sorry for not responding your messages.i just saw them.also forgive me for my english........you can ask me whatever you want about taz project.since then i already build 2 more with enclosure .i will give you a link to hear the sound one of my friend.

.as you can see in the link before play the video the name of the second mod is nteloss......and i made one more by the name mojo...here is the link

.both of my friends uses only the amp without pedals in universal audio ox box. i would be very happy to help you with sir.

[Platefire]

Hello strmusicman
    Happy New Year to you! I would say your doing a lot better with English than I'm doing with Greek because I know "0" Greek. It appears  that you have been very busy building amps. As I remember you had acquired two Kalart 70-25's and now have a RCA you've Converted. So the first 70-25 was the Taz, the second 70-25 is NteLoss and the RCA is MoJo. Am I right on that?? I listened to your friend playing on the amps and all I can say is Great Playing and Great sound. There must be a good source of all tube amps to convert around there. I don't even hunt for them around here because they just don't exist to be had around my local area. They seem all to be on ebay at very high prices.
   I was very impressed when I seen your pictures of the Taz because if I understood you right, that was your first amp and you learned all you did by researching and reading on your own. That's a pretty complicated project for your first. I thought it was laid out in the new chassis really well to help prevent unwanted noises/oscillation. You also repurposed most of the old circuit and parts from the old reel to reel audio chassis to the new one. So great job on your excursion into tube amps. It looks like your having fun        I've had my Kalart 70-15 several years now and haven't done anything with it. So now I think I'm ready to make a usable amp out of it. So I'm trying to decide what direction to go with it. I liked the sound of the old Kalart70-15 circuit plugged into my guitar speaker cabs. I've hooked it up to my speaker cabs with delay and reverb pedals several times and got a very agreeable tone and response out of it. So I'm trying to decide rather I want to re-purpose that old circuit, as you did or build something completely new. So if you don't mind and you would like to, please elaborate on the Taz's sound and operation, problems you had or anything good or bad after you installed it inthe new chassis.   
    So it's good to hear from you again and glad your enjoying your new hobby that can turn into a profession if you don't watch. Platefire   
       

[bmccowan]

As you said Platefire, great sound and playing. I hear a lot of Bill Frisell in the second vid. Bill is one of my favorites.
Although your friend made use of that "special grouped component." That would be a likely hum suspect in my book if the grounds and filters in the amp have checked out.

[strmusicman]

hello again from greece.1)all those that i modified for me and my friends are victor -kalart 70-25 projectors and i have another one in my home disassembled ready to fix it like the others.2)the rca logo i made it for myself and my other friend wanted to make him also.mine is from alpaka material(metal that make fake jewels )and my friend was made from brush.i just print rca logo ,print it,glue it on the metal and cut it with tiny saw .3)70-25 projectors except from 6l6 tubes also have inside a nuvistor tube.is a litlle metal tube.thats why there is an extra input and a extra drive potentiometer on the chassis.if you can find a photo from google of 70-25 you can see that has two inputs.the second input says microphone.so the input on the right its like a return and the left input its like a drive channel 4)i have change all the components from 1)board 2)all the cables (except the cables from potentiometers) 3)the pt screws 4) all the caps and 5) i  added a fuse holder with fuse inside as the manufacture says inside the manual.
first i change the electrolytic caps but i found that the sound even then was kind of muddy.i know that some people say that the resistors made of carbon component have "mojo" but mr platefire trust me changing all the components from the board made this amp much much better than it was before.

as for the baxandall i have to say this:i think that works like a presense of base and treble.i think that this weird tone stack is like taking the best and most wanted and effective eq parametres from the sound.The idea to make a chassis with specific length and depth came from here:https://www.tdpri.com/threads/blackvibe-6v6-build.1053259/.
but i didt buy the chassis i made it from aluminium.i dont have any program to design where to put the wholes for the components i just copy the idea from the link above.i also buy wood from pine and tolex and i made the enclosure.As for the chassis the taz and nteloss project was made according the link above but the mojo i kind experiment and made it shorter in depth about 4 cm to be more lighter that the others.also i didnt have any problems with oscillations it worked right away.The only buzz i had was on my first project, because i dress in the same cap the wires from 6l6s and the wire from the first board that works with the first preamp tube.when i change the first board with the second that works with the inverter tube(the second 12ax7)everything was dead quiet.

I made those for fun only.it took me about 3 months to understand how amps works.but i started read and made those due to the covid......
Also i am not thinking to do it as a profession cause i have 3 profession already.i am a pro session  guitar player here in my country,i have also a guitar diploma as a electric guitar teacher and last i have a company with 10 shops here in greece.if you like check my video mr platefire. hope you like it icon_biggrin::

Feel free to ask whatever else you want.hope that i help you a bit for your project.good luck mr platefire

{edit- added space before URL to make it clickable - PRR}

[strmusicman]

edit:I use dremel and a small cooper brush to give the aluminium that 3d look and i search for fonts on the internet printed ,and then using film carbon i copy the letters on the chassis and then i re write them with permanent pen

[Platefire]

strmusicman
All I can say is WOW! and my Jaw is dropped to the floor. Amazing Playing! It will take me a while to process thisbut I will eventually respond. 
Platefire

[strmusicman]

thank you very much mr platefire for your kind words.happy to help you

[Platefire]

Hello strmusicman

I live in central Louisiana, retired. Most people think of swamps and Cajuns when they hear that name but all that is down South on the Gulf coast. Mostly pine forest and some clay hills here. Sounds like you are very busy with guitar teaching, studio work and managing your shops. I was mostly joking about making a profession out of amp building but one thing for sure though, once you get it in your blood you seem to do it rather your making money at it or not:>) I like the work you did on the NteLoss amp. The cab, expanded metal front and RCA logo. The script identifying the controls is really nice. Is that done by hand or machine? Anyway, that's a Great Job!


I got a few questions as follows:

1-Is the "Return" on the right a Preamp-out. I'm not fully understanding what the return is or does. My 70-15 don't have a nuvistor'


2-So as I understand it, you re-used the PCB boards in both amps but changed all the components. So did you keepthe same values as the existing components for the new ones or change any values of resistors or capacitors?

3-On the Baxandall Tone Stack you made the statement, "I think that this weird tone stack is like taking the best and most wanted and effective eq parameters from the sound"-----I'm not sure how to interpret this butI think you are saying it is very good at extracting the best EQ for guitar tones. In other words, you like it very much?

Well that's all for now. It's a good result when you can say the end results is Dead Quiet. You made the right decisions. You have made a lot of progress in the time you've been building tube amps. Just wondering if youhave attempted to make schematics or layout of your amps. On this forum, that is kind of the way we communicate with each other about our amps. It really helps because once you learn to read a schematic and layout you can instantly see all the details of your amp or someone else amp. We generally us the program ExpressSCH that isa free download. Here is a Link:
https://www.download82.com/download/windows/expresssch/

Thanks for taking time explaining all about your amps. Just wondering what amp you used to do the video. I seen off to the side what looked like a red knob Fender Twin Reverb but I couldn't tell it that was what you were playing over. Great playing and sound! I may have more questions as they occur to me  

[Platefire]

Last week when it was raining every day I had an idea on a possibility for this project I began to develop called the 1482 Stray Cat. I have a lot of El84's, 5Y3's and even found a newish Fender Excelsior Output Transformer I think would work with this. So I strayed from the original 1482 format with EL84's and 5Y3 Rectifier. Got no trem, one channel bare bone stock 1482 and the other cleanish and brighter. It was a passing thought to keep me entertained so here is the schematic and I welcome you to chew it up, spit it out and tell me what's Hay Wire

[sluckey]

Must add 470K grid leak resistors to EL84 grids. 8.2K grid stoppers would be a good idea too. Cathode resistor should be 130Ω or 150Ω. Adding a cut control to an EL84 amp is a nice feature. Look at my Dual Lite for reference.

[strmusicman]

Hello again mr platefire.everything about the mod was by hand.except the aluminium chassis which was folded by machine.the letters also was by hand,film carbon paper and permanent pen.                                                                   The return input is an input that it does not have gain.I named it return cause it’s like the send-return inputs that all amps have.I use metal film resistors and orange drop coupling caps with same values as the manufacture suggest.I think that baxandall tone stack is not that versatile but it’s right to the point.I just love it.I consider that this is a fender circuit so I am not trying to play every kind of music with it.but I think with proper pedals you can get close enough.as for the schematics I will be honest.it was a pain to read it.I am not as good as you are but I am trying…….I think the song Manhattan was played with my vht gp3 valvulator pream through my 2x50w vht power amp .I think the cab was a 1x12 open back with Alnico inside.                                 Overall I’ve came to this conclusion.I believe that the power transformers has to do with the quality of the amp sound .that victor projector sounds like a 50watt amp.so warm so much headroom so many harmonics and a 3d like sound.      Before I bought them from my friend he told me to listen to another amp.I think it was a 100watt cornford.I said ok . It was a nice amp .but then he switch to victor amp and I was what the earth is this?day vs night.what can I say it was mind blowing the comparison.

[Platefire]

strmusicman
I forgot to ask you, could you give me the depth, length and width dimensions on you Taz chassis? Thanks!

[Platefire]

OK sluckey, thanks for the check up! Please tell me what the cut control does and how that 250KA pot is hookedup?
 

[sluckey]

The cut control is a tone control that cuts treble. Look at my schematic/layout. You can figure this out.   

[Platefire]

Well on your cut control I hate to plead ignorant but I can't really say for sure. It looks kinda like a simple tone control.I think the symbol you used for the pot with a slash through it is a Rheostat that would be connected to the input term and wiper only and from the wiper to the .005uf cap. So I know I use 500nf a lot in tone stacks but the cap used here is 5000nf(10 times more). With this placed between the two PP sides instead of just a single line of flow as on a single grid, it's hard for me to understand how it works to cut treble not unless you were playing with the pot fully open(no resistance) through the cap and then increased the resistance cut off any flow through the cap? Bumfuzzeled
Kinda like Festus when someone ask him to read a note, and he would say, oh I forgot my glasses, you'll haveto read it for me! Knowing he couldn't read a lick

[sluckey]

OK Bumfuzzel. Look at page 2 if you can't figure out the schematic.

And BTW, a .005µF cap is the same as a 5nF cap. Don't know where you're getting these crazy numbers. I'd be willing to bet you have never used a 500nF cap in a tone stack. Probably never used a 500nF in any tube amp.

Try this...

https://www.convert-measurement-units.com/conversion-calculator.php?type=kapazitaet

[Platefire]

Well I was looking at my hard copy cap conversion chart and was looking at nf and should have been pf. Yes I see your new high fangled computer converter translates .005uf to 5pf as even my hard copy does if you look in the right place. So yeah sheet 2 layout spells out hookup. Thanks! Going to Bed

[sluckey]

Yes I see your new high fangled computer converter translates .005uf to 5pf as even my hard copy does if you look in the right place. So yeah sheet 2 layout spells out hookup. Thanks! Going to Bed

     sigh!

Sweet dreams.  

[strmusicman]

Its 40cmx21cmx6cm the chassis.

[Platefire]

strmuaicman
Thanks for the chassis dimensions. Hammond has one very close to that size in inches is 2" deep x 8" wide x 16" Long.

[DummyLoad]

Last week when it was raining every day I had an idea on a possibility for this project I began to develop called the 1482 Stray Cat. I have a lot of El84's, 5Y3's and even found a newish Fender Excelsior Output Transformer I think would work with this. So I strayed from the original 1482 format with EL84's and 5Y3 Rectifier. Got no trem, one channel bare bone stock 1482 and the other cleanish and brighter. It was a passing thought to keep me entertained so here is the schematic and I welcome you to chew it up, spit it out and tell me what's Hay Wire

Small error on that schema. Attached correction - V3 control grid drive was attached on wrong end of 68K cathodyne plate resistor (connected to B+ node C). Also, missing grid leak resistors for the EL84 pair. 


--Pete

[sluckey]

The AC coupled cathodyne is also missing the bias resistor (R_b) on the cathode. I realize the 1482 schematic is also missing the bias resistor but I believe this is a drawing mistake? Here's a properly biased ac-cathodyne...

[Platefire]

Hay DummyLoad---Yeah I normally wouldn't put the grid on the wrong side of the plate resistor. You was lookingat an old schematic and the grid leak resistors have been added. I sure appreciate you looking!


sluckey---you got me wondering about the 1482 what's actually under the hood? What kind of cathode resistoris actually there? I have made the corrections and the revised drawing is attached. See if I got it right

Thanks a Bunch

[PRR]

..The AC coupled cathodyne is also missing the bias resistor..

I have seen that so many times, I suspect that in smaller guitar amplifiers it works OK. You can get several tenths of a volt positive grid without huge grid current. That may be several volts at the cathode and power tube grid. If signal gets larger the cathodyne grid cap charges, clips a couple peaks, but holds that bias for many seconds.

[Platefire]

This is the schematic that came in the 1482 user manual

[sluckey]

See if I got it right

Almost. That 47K needs to be 68K, same as the plate resistor.

[strmusicman]

i know.in my previous messages i put a link from tdpri that the person who used it says about the chassis dimensions.i attach the schematics of ur projector.

[strmusicman]

more

[strmusicman]

and more...

[Platefire]

OK Thanks sluckey, Corrected copy attached

Also is that 25uf/50 correct cathode bypass cap for those EL84's?

[Platefire]

strmusicman

  I have a link attached on the first post of this thread that will take you back to the original thread on this Kalart Victor 70-15 discussion information(several years back) but this brings it forward more easy to access. Thanks
 

[sluckey]

Also is that 25uf/50 correct cathode bypass cap for those EL84's?

I've used 50µF and 250µF. Both sound good to me.

[Platefire]

 

[Platefire]

On this Kalart Victor amp, I think I will start to remove all the parts out of the R to R chassis with the idea of salvage while considering the idea of making an amp out of it like strmusicman did. That's a task I need to do to proceed on this one anyway. That may help me decide how I want to proceed 

[PRR]

I thought it already was an amp? The only funny bits are the optical preamp and maybe add NFB to the speaker side.

[Platefire]

PRR
Every time I look at that original Kalart Victor schematic I get confused and I decided I would draw a schematic in my own style to help me get a handle on it. It's attached. I took all the tape recorder stuff off the inputs and just left the Phono type. Also the power supply to me was kind of squirrely especially around V1a so I changed it to what seemed right in my eyes,but may not be? To me my schematic is a lot more easier to read now, at least for me.

I did try to keep 90% same as the original, only changed what I thought needed to be changed in the input and power supply. I will attach the original schematic also for convenience. I welcome you or anybody to check me out to see if it's compatible with original. That always a good place to start. Platefire   

btw---got a question on the KV original schematic. In the tone stack there is a slashed rectangle
to indicate the parts inside the multi-component tone stack special part. What are the circled numbers in reference to?

[PRR]

> What are the circled numbers

The legs of the PEC module, isn't it?

[Platefire]

Yes, that thought occurred to me, those are the leads for hookup. I just can't find in KV materialwhere they have it written down. No matter, if that part ever went bad, no replacement for sure

[PRR]

The Baxandall network is not lost. The PEC is a dollar's worth of R and C, bundled for 97 cents. Read the resistances of the pots, look around for another Bax using those pots, -or- transpose a found plan to your pot values (shift everything the same ratio). Build on terminals or just twist parts together on pot lugs.

Oh, wait, The part values are on the plan you posted. Blurry, will need interpretation.

There IS a master list of "PEC module" internals, somewhere. And the Bax tone was a popular part, not a one-off custom.

[Platefire]

I played around with it last night and learned a lot more about it. I mean I looked it over goodcomparing the layout with what's in the schematic. Played some guitar through a good speaker cab. It sounds very guitarish as is. It gets pretty loud IMHO. Comparable to a ST 1482. Problem with it at low volume is a "hum" and the louder you turn the volume, the louder the hum gets.I Alligator clipped  some filter caps in but that didn't help. Moved wires around with a chop stick for more clearance. Checked resistors in place, read pretty close to what it should be. Checked grounds. I'm beginning to think all the noise is in the board components. That what strmusicman said, when he changed all the board parts in his 70-25, all the noise went away.



PRR, I did take a closer look at the PEC module and all the connection leads are on one side numbed 1 thru 7. So just what we suspected is true. I did do some research on the net for more info where I could fine KV info, but nothing else.


All the coupling caps on the board are ceramic disk type. Tonight I might check for DC leakage.If I could get the noise stopped, I might just leave it in it's present form? Still pondering it but good fun

[Platefire]

   Well I had a little success. I found the noise(buzz) maker. Got to checking the coupling caps with the amp live and on V1b,  the .02 Ceramic cap blocking DC to the grid was leaking 39VDC. Got to looking and couldn't find a .02 any where, used them all on the Pro Reverb. Got tolooking and found another ceramic .02 in the part of the amp was supplying 50V to a tape recorder RCA input I had abandoned, so I used it. It worked and running quite as a mouse right now. So I'm going to bask in success and hook a delay up to it and jam a while, after I clean up my mess. Platefire

[sluckey]

Got to checking the coupling caps with the amp live and on V1b,  the .02 Ceramic cap blocking DC to the grid was leaking 39VDC.

Huh??? I don't see a .02 cap anywhere near V1. What are you really talking about?