New amp schematic for feedback

[Ed_Chambley]

I have attached a new schematic I would like some of you guys to look over for me.  I want to make sure the circuit will work and input on ideas.

Also, I need to add a loop and was wondering where I might insert for the best outcome.  I would guess I have missed a few things since it is not a clone.  Once I get a solid circuit, I would like to add an overdrive using a EF86 if possible.

Any suggestions and especially corrections are welcome.

[sluckey]

Reverb driver will be much happier with 2.2K/25µF on the cathode. 410Ω will likely run the tube too hot.

Shared cathode resistor for V3 is usually 820Ω rather than 1.5K

V3-A grid is grounded. That will make for a very quiet amp.

Do you really want to kill the rectifier filament with your STBY switch?

I'd put the loop between the MSTR VOL and V2-2.

[Ed_Chambley]

Yea, but it is purdy tho.

Made some changes.  Are these correct.  I would have a quite amp with the grid grounded.  Missed that one.

Question: Why is the reverb driver tube bypassed?  I have seen an amp without, but I don't know how well it worked.  My R and C numbering is off badly now.  I will fix it after I remove the apparent problems.

[sluckey]

Question: Why is the reverb driver tube bypassed?

More gain for the driver. Surf music was popular back then. So was strong reverb.

An easy way to reduce reverb in a Fender amp is to clip that bypass cap. Another good thing to do is use a 100K log pot for the reverb control.

[Ed_Chambley]

The reverb I am speaking was in an amp I worked on a while back.  It did not have a bypass on the driver tube and each K had a 820ohm.  Sounded really nice.  That is a tweak thing so I will get it later.

For the loop insertion, do you mean to insert it between the 2 caps what are currently C11 and C8?

Does this look like a specific Fender you are aware of?  If so, which one.

I saw Dick Dale last thursday.  He is a wide open nut and still does a great show.  The strong reverb comment reminded me of the show.

[sluckey]

Does this look like a specific Fender you are aware of?  If so, which one.

All of 'em. But most of all, it looks like my TDR. Except for the cat bias, cathodyne PI and presence pot.

I was very specific about where to put the loop.

[Ed_Chambley]

Does this look like a specific Fender you are aware of?  If so, which one.

All of 'em. But most of all, it looks like my TDR. Except for the cat bias, cathodyne PI and presence pot.

I was very specific about where to put the loop.

Yes, you were very specific.  You wrote "I'd put the loop between the MSTR VOL and V2-2".

I probably did use some of your TDR schematic components.  I can draw all of it if you prefer me not to use any of your work.  Just let me know.

It does look like a lot like Fender, but most do.  Some more modded than others.

[sluckey]

There are no strings on any of my Visio work. Glad to see you playing with schematics.

[DummyLoad]

looks like a princeton reverb with 5881s instead of 6V6.... and of course an added MV, sans NFB and bypass cap for V4-A, and a choke, oh yeah, and cathode bias 5881's  (i'm calling the driver and SLPI connected to node "C" V4-A and V4-B respectively).


5881's should be V5 and V6. - you have V3 and V4 - man! good thing you're not laying out a PCB! <ducks a and runs.>


add NFB like PR and bypass V4-A - better still; a switchable bypass for V4-A.



--pete

[Ed_Chambley]

looks like a princeton reverb with 5881s instead of 6V6.... and of course an added MV, sans NFB and bypass cap for V4-A, and a choke, oh yeah, and cathode bias 5881's  (i'm calling the driver and SLPI connected to node "C" V4-A and V4-B respectively).


5881's should be V5 and V6. - you have V3 and V4 - man! good thing you're not laying out a PCB! <ducks a and runs.>


add NFB like PR and bypass V4-A - better still; a switchable bypass for V4-A.



--pete

Thanks Pete and Sluckey.  I will straighten out my numbering as soon as I get some other things done.  What it is is a Carr Rambler to be truthful.  Well sort of.  I had one on loan for a couple of months and really began liking the amp mostly.

I tried to reverse it and I know I am very close.  If you read the description on Carr's website it basically says what you guys are saying.

I have fallen in love with the EF86, but not running it hard.  The AC15 cascode is goooder n' snuff I am uh tellin you.  Anyway, work today so I need to do that.

Thanks for the input so far. AGAIN I WILL GET THE NUMBERS RIGHT!!! Isn't it awful to have to deal with a Dummy, Dummyload?

Once I get the loop placed I will number correctly and then you guys can communicate with me correctly.  BTW, the amp's voltage is low for 5881.

[Ed_Chambley]

There are no strings on any of my Visio work. Glad to see you playing with schematics.

I like Visio.  It is intuitive.  I am working on learning proper layer placement.  Locking finished layers really makes it nice to add new elements.  Then when worked out you can either add it to an existing layer or lock then new one.

Good stuff.  I have also made a few new stencils.  The new Mouser program is comparable and makes it so easy to get an exact part and size for a layout.

[kagliostro]

I received some libraries for Visio from Steve, Barry and Pete

and with the adequates libraries Visio is really great for Layout design, also if my version is an old 2007

every day I go on in using it I think why I didn't used it before

K

[Ed_Chambley]

I received some libraries for Visio from Steve, Barry and Pete

and with the adequates libraries Visio is really great for Layout design, also if my version is an old 2007

every day I go on in using it I think why I didn't used it before

K

I have some I have added.  The file size is too large to upload here, but if you want to PM me you email address I will send you some more of the stencils.  Maybe some you don't have.

I only made a couple of changes.

Question of Dummyload Princeton NFB suggestion.  What benefit would that bring and can I still use a presence?

[sluckey]

Why don't you post your drawing in a format that doesn't blur the image. Then we can actually read the tiny print. PDF is great. Just print your file to a pdf printer driver and upload. Or... You know Doug allows vsd file attachments now?

[DummyLoad]

ed, don't use jpeg. use PDF, PNG or GIF formats for graphics. jpeg is for photo's and you loose resolution when you save graphics as a jpeg.


respectfully,


--pete

[kagliostro]

To me a good system for posting  a schematic is to upload the image at Imgur (http://imgur.com), copy the link, use the image tag on the forum and paste the link

this way the software automatically shrink the image to the windows measures and, more, the image can be more big without waste space on Doug's server

the use of other hosting image services isn't so simple in results as with Imgur from where is very simple the download of images in full format if you want to save it on your PC (I really don't like service like Imageshack - https://imageshack.com)

Of course you can, at the same time, save a pdf file containing your image, attached to your post if you are afraid about the linked image persistance on the image host

This is an example, I uploaded your schematic to Imgur and here I used the image tag



the software automatically adapt it to the window and there is no occupation of space on Doug's server

This way you can use images with a better resolution that saved on your PC from the tread page, will appear in their full resolution

more, you can menage the width of the image (that is shown on the forum) editing your post and modify the tag changing the width parameter that is on the tag, in this case you must eliminate the height parameter on the image tag, the software will set the proper height by itself

this is haw apper an image tag if the image is larger than that is (by the software) allowed on the window (the * were added as to permit you can see the Tag)

[*img width=1024 height=591]http://i.imgur.com/0ONKxWb.jpg[/img*]

if you change the tag in this way [*img width=500]http://i.imgur.com/0ONKxWb.jpg[/img*] (remember the * are only as to permit you to see the tag)

what you'll see is this, but the image is always in full format and if you save it you can see it in full format
(with Opera, that is the browser I use, I can see the full format also simply cliking on the image)




Franco

[DummyLoad]

this is what i was thinking...see attached. 


--pete

[Ed_Chambley]

this is what i was thinking...see attached. 


--pete

Like it!  I have made some revisions since so I will add to the drawing I have.  Enlarging the fonts and a couple of other things.

Question: It is definitely similar to a princeton, will the 5K pot kill the NFB if rotated full CCW?  That looks like what you have in mind?  I just copied the 5E5a NFB.  What will be the tonal difference?  Similar to putting a pot on a 1987 Marshall NFB?

[kagliostro]

Some time ago I've find this on the web and it was indicated as the best tube FXLoop, I didn't tried it, but if you are interested ...



Franco

[DummyLoad]

there is a 1k in series. so with pot at zero there's at least 1k in the nfb loop.

--pete

[Ed_Chambley]

there is a 1k in series. so with pot at zero there's at least 1k in the nfb loop.

--pete

I see that now.  Thanks.  That is one of those things it takes me a long time to get happy with.  Most of the time I find myself playing with the nfb switched off.

[jojokeo]

There are no strings on any of my Visio work. Glad to see you playing with schematics.

  Nice one, likes to read them just not build with them. (some of us know you too well Ed) I was instantly thinking cathode biased deluxe reverb w/ cathodyne & no trem when I first saw the schem a few minutes ago. (a bit late to party as usual)

[Ed_Chambley]

New stuff.  Needing confirmation and a Raw pot.

If all is close, I will be looking to get a pentode in the preamp next.

And yes, I am terrible about schematics.

[Ed_Chambley]

There are no strings on any of my Visio work. Glad to see you playing with schematics.

  Nice one, likes to read them just not build with them. (some of us know you too well Ed) I was instantly thinking cathode biased deluxe reverb w/ cathodyne & no trem when I first saw the schem a few minutes ago. (a bit late to party as usual)

Yep, but when I add an EF86 I may have a game changer.  Seems most of us look at schematics and when we see that tone stack, we think Fender.  Lease I do.

Jojo, while you are here, what do you think about a Tone Stack Bypass and how would you do it?  Question is for everyone as well.

[John]

what do you think about a Tone Stack Bypass and how would you do it?  Question is for everyone as well.

Simplest way (I think) is a bypass switch similar to what you've got on the reverb tank. If you wanted to, use a DP switch and lift the ground to the TS as well. BUT, I also think you should have a coupling cap coming off V1-A into your TS.

[kagliostro]

About TS bypass give a look here, you can have a progressive bypass lifting the TS from ground with a pot

https://taweber.powweb.com/store/pprc_schem.jpg

Franco

[kagliostro]

If the FXLoop don't satisfy you after you give it a try, here is one other (from Engl Fireball) that was tried (with positive result)



Franco

[Ed_Chambley]

Here is a revised version.  Please check for errors.

The loop K posted that I have redrawn has a non-grounding connector on the "send", but I have it as a grounding connection.  Which should it be?

I plan to add relay switching, but I would like to get errors fixed.  I am not sure of the best location for the EF86.

Also, I am sure I will have to tweak a lot of values.  Please point out the obvious.  Thanks, the .zip is the Visio file for anyone interested.

[kagliostro]

Ciao Ed

To me the use of a TS after a pentode isn't a good choice, pentode seems don't like much TS, if you want to use a pentode as V2

my 2¢ council is to use a CF or a Source Follower between the pentode and the TS

EDIT: The way you used the splitted plate resistor, on the ef86 plate, is odd to me, are you sure about it ? I think to the coupling capacitor connected to the junction of the 180k with the 56k and the 2.2M resistor connected to B+ node

Franco

[Ed_Chambley]

Ciao Ed

To me the use of a TS after a pentode isn't a good choice, pentode seems don't like much TS, if you want to use a pentode as V2

my 2¢ council is to use a CF or a Source Follower between the pentode and the TS

EDIT: The way you used the splitted plate resistor, on the ef86 plate, is odd to me, are you sure about it ? I think to the coupling capacitor connected to the junction of the 180k with the 56k and the 2.2M resistor connected to B+ node

Franco

That is what I have been reading and I appreciate the input.  Originally, I had planned to place it last in the preamp, but had concerns with reverb.

Think the EF86 is best before or after the Reverb?  Does it matter?

I will read up some more and rearrange a couple of things. 

[Ed_Chambley]

Here is a newer version with the EF86 after the tone stack.  The values of the EF86 in use in the Matchless and Vox amps according to Merlin's preamp book are microphonic because they are adding too much gain.  I had a mixture of component values from reading his book and looking at schematics.

BUT

There is nothing like experience and I have none in using an EF86 anywhere other than V1.  I plan for cap switching, but I am trying to get proper tube order.

Also, he mentions with a Cathodyne it is very easy to get UGLY distortion.  A lot of things I will simply tweak till I get what I want.

I thank you for taking the time to share your experience with me.

[kagliostro]

To me seems you have a lot of gain .... may be too much


Franco

[Ed_Chambley]

To me seems you have a lot of gain .... may be too much


Franco

I agree, i am learning and reading.  Mostly what is surprising is how clean the ef86 is.  Anyway, thank you for your input on this so far. 

[GeorgeA]

Did you ever build this?

[tubenit]

I built this one which has differences but some similarities.   Reverb, passive effects loop (which works great), 5879 instead of EF86 overdrive, and 3 gain stages for the clean preamp.

with respect,  Tubenit

[Matt R.]

Rumble Seat - your ode to Carr Rambler? Fairly similar, Rambler has no NFB, MV or choke. You dropped the trem.

[shooter]

Rambler has no NFB, MV or choke.

Neither does ED