Electrohome Mono Hifi into 5F11 Vibrolux

[Toxophilite]

Hello all
I'm relatively new here
In the past i've done a few mono hifi amps to guitar amp conversions, mostly rewiring the audio path of the preamps and adding better tone controls. Also some messing around with negative feedback adjusters.

Recently I decided to build an entire amp based on a vintage fender schematic. I acquired what appeared to be somebodies 1950s homebuilt PA/instrument amp, A bare bones unit with beautiful Hammond transformers, 2, 6V6, 5Y3gt and 2 12AX7..perfect!. The output trasformer had 3 impedance taps! Yay. I decided to build a tweed deluxe, and did so, removing most of the old innards and rebuilding anew. It sounded good but too dark and middy for my tastes, also the 2nd 'channel' was much too dark. So I changed it into a 5F11 Vibrolux.I had to do some jiggery pokery to get the voltage for the tremelo as there was no bias tap but it works! . I like having the tremelo and it sounds good in my recycled cab with a JBL D130
I do have more hum at high volumes now though so some troubleshooting will still go into that.
I'll do another thread about that

I've since acquired an electrohome hifi and I wanted to make another 5F11..what could be better than two in stereo!
My new chassis is 2 6V6, 5Y3 ,12aT7(phase splitter/driver) 12AX7 and a 6AV6, the other 4 or so are all 7 pin radio tubes (6ab6 6eb6 etc)(though I could add another 6AV6 using one of the sockets).
It has a nice power transformer and an under chassis , pretty big 8ohm output transformer.

Soooo..my long story gets to some questions!

-Since a 6AV6 is essentially half a 12AX7 ss there any reason it can use it to run the tremelo and use the 12AX7 to have 2 inputs in classic fender style?

-I also want to do a standard 3 pot fender tone stack as clean with some mid scoop is more my thing
though I like the tremelo and the general ease of the build. I'm not worried about getting the exact Vibrolux sound,just the sound I wanmt..what do you think?

Also this unit has some neat features. A separate filiment tap for the 12AX7 with a hum balance pot
As well as what looks like a bias adjustment pot for the 6V6s
I can nuke and pave but these features seem kind of neat

-The latter seems like it would be impossible to use with the tremelo setup on the 5F11
What say those in the know?

i have another Electrohome conversion, done with a PA300 that has the same features, On that one i just rewired the inputs and put 2 channels and a fender tone stack in. presto guitar amp!
Checking the schematic it actually has the exact same power section and hum control on the 12AX7 though a slightly different tube compliment otherwise (6Sl7 driver and a 6Sf5 preamp too)so I'm going to try and post the schematic as well as pictures of the present build, and the other two amps for fun.

The current build, somewhat gutted

the Electrohome PA300 schematic with the same power amp section and 12AX7 preamp hum balance setup

The Previous vibrolux build

The PA300 amp

I'm thinking these pictures might not work..flickr has changed...again!, and my computer is almost as old as some of my amps! IThough I'm familiar with the process and have used the exact same on the wooden boat forum..grr

Thanks

[Toxophilite]

Vibrolux 5F11 Build from Electrohome Hifi (hopefully this post works!)

Hello all
I'm not sure what happened to my previous attempt at this post, it's a source of some frustration and I apologize to those who tried to read it.

I'm building a vibrolux 5F11 using and existing Electrohome Hifi chassis as a bassis
It has a good power transformer with a seperate filiment tap for the 12AX7 (hum control..neat)
An 8 ohm nice sized under the chassis mounted output transformer
And a usable tube compliment of 2 6V6GT 5Y3GT 12AT7(driver) 12AX7 preamp and 6AV6 (preamp)

It also has an interesting feature of what looks like an adjustable bias for the 6V6 run off the 2 220k resistors on the grids to separate leads of a trim pot ..I believe their run to ground through the pot. The cathodes also hooks to the 220K resistors via 470 ohm resistors

It shares the exact same power amp section and 12AX7 hum balance control of a similar vintage Electrohome PA300 that I previously converted to a guitar amp by rewiring the inputs and preamp section. I will attempt to put the schematic of that up and a picture of the current amp but it was my attempts to do that on my ancient computer which seems to have foiled my earlier posting attempts.)

Anywho
i have a couple of questions
I mostly like 5F11 over the deluxe because of the nice tremelo and the negatice feedback with flatter response, more clean headroom and brighter sound. I am however not concerned with keeping it stock..I mostly want a cool amp that suits my needs and sound (mostly clean)

-I've read that the 6AV6 is basically half a 12AX7. Can I use it to run the tremelo, thus freeing up one side of the 12AX7 for potentially another channel, or gain stage.

-Is there a problem with leaving the hum balance control on the 12AX7 preamp?

-I guess if I want to have the neat vibrolux tremelo I likely can't keep the kind of neat adjustable 6V6 bias feature, Yes or No ?

- I wanted to put the standard fender tone stack (bass mid treble) in hooked the way it usually is with the 1 meg volume control
I know this has more insertion loss. I don't mind losing some potential distortion but will this make my amp too quiet?

I've built another vibrolux, and it sounds nice though it hums some at maximum volume..THis increased when I did the jiggery pokery to create the proper negative voltage for the tremelo as there is no bias tap. I used a tried and true formula I found on this site and the tremelo works great
i might post about it too

Thanks in advance

[Toxophilite]

Here's the schematic of the Electrohome PA300 which shares the same power amp section and 12ax7 preamp hum balance setup

[Toxophilite]

Okay I've tried many attempts to put up pictures
I have pictures of the build etc etc
I have the pictures on flickr
I've used this same system successfully elsewhere yet I don't seem to getting results
Can anyone else see the schematic I posted?

[withnail]

You shouldn't post your questions on this site.. you can watch your hair and fingernails grow before you get a reply. Go to Doug Hoffmans' site .. EL34 world. This forum is a dead letter office.

[DrGonz78]

I don't see a schematic posted...

[Toxophilite]

uhhh

Thanks for the tip..However it begs the question,
What are you doing here ?

[withnail]

Uhhh. sometimes I look at this forum to see if somethings' changed, or if time is standing still as usual.

[Steve A.]

Toxophilite:

Uploading pictures here has been problematic from time to time. Best bet is to click on picture icon (to the left of the video icon) and select "from URL." Paste in the address of the picture and then unclick the box that says "retrieve remote file..."



When you do that the picture is inserted in-line into your post. Try to keep the resolution down- if you post something like 2048 x 1600 the window will expand to fit the image making it difficult to follow the thread.

If you click on the "retrieve remote..." it will attach the image to your post and display a miniature version of the image. (If you click on it you will get the full-size image which you can download through the right-click menu.)


Steve Ahola

P.S. To upload a file from your computer as an attachment you need to click on "Go to Advanced" and then scroll down until you find "Manage Attachments." Click on "Add Files" and then browse to appropriate folder and select the image. Click on "Upload" and when it is displayed in the window at the bottom you click on "Done."
If you still can't get it to work send me a PM with the URL's for the schematics and I can post them here.

P.P.S.

You shouldn't post your questions on this site.. you can watch your hair and fingernails grow before you get a reply. Go to Doug Hoffmans' site .. EL34 world. This forum is a dead letter office.

If you check the forum listings here you will see all sorts of threads with multiple replies- even multiple pages. Sometimes it is better to post to the general "Guitar Amps" area rather than something very specific like "Build Your Amp!/Tweed Builders." I just captured this image from the Guitar Amps area.

[Jazz P Bass]

Here is the PA 300 schematic.

Man, I hope this was a fast enough response.

Huff, huff.

Pant, pant.

[Jazz P Bass]

That cathode circuit on the output tubes certainly is interesting!

[ron vogel]

Personally, I would use the 6AV6 for the preamp. Use a dedicated valve for the PI and tremolo. I started a 5F11 myself, that turned into more of a 6G2, and had major trouble getting the PI and tremolo to play nice with higher voltage and gain. I had to bias the PI with an LED to not freak out with higher gain, and make major mods to the trem to stay strong at the highest and lowest settings. If I get time over the weekend I'll post up an updated schematic on how I got mine to work right. I was able to bias the trem with an LED also (which looked really cool as it flashed), but it plain worked better with a cap/resistor.

[ron vogel]

Also...You could use the 12at7 position as your preamp stages, and run the 6av6 in parallel to one of the stages to get some extra umph...or graft in a bassman style tone stack. This is what may eventually happen to mine.

[Toxophilite]

Thanks all and sundry for the input
I appreciate it!

I was contemplating keeping the 12AT7 for the Phase Inverter, just an idea right now
Good if I was doing a AB763 type of circuit...i wonder how it would work in a vibrolux or BF princeton

As I already have a mostly straightforward 5F11 I think I'll be monkeying with this one more

I thought the lonely little 6AV6 would be good for the 5F11 style tremelo, No? It is right up mext to the phas inverter and there is another wired up 7 pin socket there
(I actually have another 6AV6 kicking around too)

Then I was thinking of using the 12AX7 as the preamp. Going in one side, out into a fender style tone and volume stack, and then back in the other side, and out again into another volume control prior to hitting the phase inverter and power amp

How does that sound?


What do you folks think of the Princeton AA964 vs the 5F11?

I mostly like cleans, some distortion for recording is fun
I've also had suggested a AB763 deluxe minus the reverb and ususing the vibrolux and or the tremeloux tremelo circuit

Steve A.
I've tried the exact process you outlined and I'm familiar with it from the exact same system at the wooden boat forum, However Flickr no longer likes my computer and It doesn't seem to let me view the exact picture, so I can't get the proper URL anymore.. I went to my account at photobucket as well but it's just as unhappy with my computer.
Then I tried the manage attachments in the advanced section and the 'working' whirly unit woudn't stop on the pop up page and non of the browse or upload buttons work.
The fault is clearly with my aged internet computer.
I was contemplating printing off some images, cracking my computer like a nut and shoving them inside before reason reasserted itself.
I really appreciate your thorough explanation regardless

At the same time as I was applying to this forum I was also applying to the Hoffman one.
Both forums were reccomended by a third party.
I got on there and was able to post some pictures. The title of the thread is similiar to this one if any of you are interested in looking.

THe inside of the chassis is interesting. The preamp 12AX7 (old phono stage) is down in the bottom right hand corner, whilst most of the tube compliment is across the top, with the driver being in the top left hand corner with the 6AV6 . with the power tunes and rectifier below
The transformers are basically atthe Bottom left and bottom middle

If used AS IS I guess the 12AX7's position would suggest it make be ideal for a tremelo circuit...but it does have that neat extra filament tap and hum control circuit

[ron vogel]

You'll probably have an easier time with a BF Princeton over the 5F11 or 6G2, neither like a lot of gain going through the PI (which I still can't figure out why), so it's a bit difficult to get good power tube saturation...especially because you need to bias it pretty cold to get a good depth from the trem in the stock circuit (but there are a few things you can mod to enhance). I have a variable NFB to scoop the mids a bit, but have come to the conclusion it's just not as effective as I'd like to cut the mids. So at least to save you going down that road the BF tone stack with a mid control would be nice on it...but you will need an extra gain stage as the gain is already a touch weak. Don't get me wrong, the 6G2 is a killer amp; but it does have some things in the circuit that limit it's flexibility. And again, I know you are asking 5F11, but the 6G2 and the BF princeton are essentially the same circuit just more voltage and tweaks