EL84 Amp with Reverb

[carausius]

Time for another amp build, I was considering a Princeton Reverb, but I've a spare Heyboer Trinity Amps TC15 / 18W transformer set & some 9 pin sockets so was considering a Vox Cambridge / Berkeley Reverb which by some online opinion is even supposed to sound like PR with EL84's. 

The Cambridge tone Stack, like a Fender 6G4 Super judging by the schematics, complete with Cathode Bias, 1/2 tube Bias Vibrato, but the PI is different compared to the PR, Vox style 1 tube. It does look like a Fender Vox hybrid!!!

The reverb section seems similar to the PR or maybe AB763 .

My PT is rated 290DC & the Vox schematic says 280DC, so should I try the Vox Cambridge schematic power rail / voltage dropping circuit values or use something more popular like Lightning / Spitfire / 18W power rail circuits for this? I'm thinking my PT might have too much juice to use the Cambridge power circuit values.

Any advice would be great! 

[tubenit]

Did you see Hoffman's 18w Stout reverb?  I'd probably copy that B+ rail and try it. You can adjust it after the build if you want.

http://www.el34world.com/projects/images/18WattStoutReverbSchematicNoSwitch.gif

With respect, Tubenit

[carausius]

Cheers Tubenit!

The 5Y3 is a better option than the EZ81 with my PT? I've noticed that the 18W schematics here have 5Y3's.

Is it possible to replace the choke with a 2.2K / 3W or similar value resistor like the 18 Lite Reverb schematic, I'll get a choke later on?

Thanks for the advice

[EL34]

The stout-reverb is a great choice.

I have also modified priceton reverbs to use EL84's and it was really cool.

[carausius]

The stout-reverb is a great choice.

I have also modified priceton reverbs to use EL84's and it was really cool.

I've got a spare JAN Phillips 5R4GA for the rectifier hopefully it will drop enough voltage, now I need a choke or replacement resistor!

A detailed look at the Vox Cambridge / Berkeley schematics , it's a AC15 PI / output stage with the AB763 reverb circuit, a Brownface Super 6G4 preamp & a Princeton Reverb Tremelo with very few component changes at all. 

[tubenit]

OK, I grabbed an old schematic and edited it to reflect your idea of an 18watt amp with reverb and vibrato.

Look at a Matchless Lighting  &  Vox Cambridge (vibrato) & Princeton Reverb (reverb).

I drew this up with values that I like to use in some places, so you might want to change them.

Anyway, it gives you an idea to work with and Hoffman carries the parts you need. You can even use his turret board materials and turrets to build a paralleled layout.

I personally would use different values in the tone stack closer to Marshall values (T-Lite-N version).

With respect, Tubenit

[carausius]

Thanks for going to all that trouble Tubenit! Especially the power rail.

I did start to edit a schematic for the Vox Cambridge / Berkeley but as mentioned above it was too similar to other circuits there wasn't much point, especially with the weird power rail! I'm attaching the preamp sections for reference, although they're a bit rough!!!!

The Super 6G4 is supposedly a good sounding preamp, I know a Amp company design guy who uses it. It's also mentioned in Jeffrey Falla's Hot Rod Fender amp book alongside various Vox, Marshall, Bandaxall & other circuits. I was going to make the normal channel of my 6G16 Brown Vibroverb build a 6G4 style pre but really like the that channel as it is, the same as a Blonde 6G6 Bassman.

I've got an 18watt so a Vox / Matchless Reverb style amp sounds cool!

Maybe I should put together a testing rig to try out all these various designs, the MatchVox Niteclub / Selmer Guy into a low powered EL84 power section was another circuit that I've been messing about with in the schematic program! There's so many choices here I'm going to go crazy LOL!  

A testing rig http://caseygipson.com/?p=136

[Blackface5f6]

OK, I grabbed an old schematic and edited it to reflect your idea of an 18watt amp with reverb and vibrato.

Look at a Matchless Lighting  &  Vox Cambridge (vibrato) & Princeton Reverb (reverb).

I drew this up with values that I like to use in some places, so you might want to change them.

Anyway, it gives you an idea to work with and Hoffman carries the parts you need. You can even use his turret board materials and turrets to build a paralleled layout.

I personally would use different values in the tone stack closer to Marshall values (T-Lite-N version).

With respect, Tubenit

I know it is old thread from 2011. Hopefully, I still have opprtunity to discuss about EL84 Puspull with reverb and Vibrato.

I just want to built an Amp with reverb and vibrato based on my Marshall 18 watt Clone. Has someone tried to built the amp based on the schematic from Tubenit, posted here?

Thanks

[sluckey]

Hoffman's Stout with reverb is based on the Marshall 18W.

     https://el34world.com/Hoffman/files/Hoffman_StoutReverb.pdf

This is a great sounding tremolo that would be easy to connect to the stout. Just connect the intensity pot between C4 and C5.

     http://sluckeyamps.com/trem/trem.htm

[Blackface5f6]

I have 3 questions:

My PT on secondary side has:
290-0-290 VAC
5 VAC
6,5 VAC

1. It is okay with 290-0-290 VAC?
2. To which point should I connect the tremolo "to signal path"?   http://sluckeyamps.com/trem/trem.htm
3. Can I just add Reverb Part into Marshall 18 Watt Tremolo Version?

[sluckey]

1. yes
2. see reply #8
3. yes. You may be interested in tubenits one tube reverb. Search the forum.

[tubenit]

Steve,

What about something like this topology?   IF the topology makes sense ………. what values would you change on anything?

With respect, Tubenit

*  DELETED and schematic reposted.

[sluckey]

Looks workable to me. I would probably replace R14 with a 250K INT pot. Maybe experiment with the trem before and after the reverb mixing resistor.

[TIMBO]

Hey T, Your reverb insertion points are round the wrong way on the mix resistor.

[tubenit]

How's this?

Tubenit

[alathIN]

Joining this thread to follow - one of my possible next projects is redoing my Vox AC4 C12 to the older EF86 preamp'd circuit - and I am tempted to try to put a short tank reverb in it.
Will be interested to see how yours turns out.

[Blackface5f6]

My idea of using Marshall 18 Watt PT and OT brings me to two options:
1. Just use PT (290-0-290 VAC, 5 VAC and 6,3 VAC/Heater) on original PR Schematic (1st Attachment: Original PR Schematic)
      or
2. Modify the Power stage using EL84. I made the schematic yesterday (2nd See attachment)

My question: does Option 1 work? This will be my first choice

[tubenit]

The original PR schematic had a PT with 340-0-340.  So, IF you use a PT with 290-0-290, you may want to experiment with using lower value dropping resistors in the B+ rail to get the voltages up closer to PR specs for the preamp.

with respect, Tubenit

[Blackface5f6]

How about +A (Power Stage)  and +D (Reverb Stage)? are they not critical?

[tubenit]

I think a reasonable goal would be to have the EL84 plates reasonably under 350v. 

Then have nodes C & D as close to PR voltages as you are able to get. So, you'd try to get node D to be 240v which hopefully would give about 160v on the plates for V1 & V2.  That's what I would personally shoot for.  So, I'd lower the dropping resistors between B & C and between C & D.

I don't know what changes you'd need to make on the dropping resistors between B &C and C&D?  I might experiment with 10k/3w and 4.7k/3w and see what I ended up with?

I've seen reverb work well with a pretty wide range of voltages.  IF you needed more voltage for the recovery stage for the reverb, you can use node C instead of node D.

With respect, Tubenit

[Blackface5f6]

I think a reasonable goal would be to have the EL84 plates reasonably under 350v. 

Then have nodes C & D as close to PR voltages as you are able to get. So, you'd try to get node D to be 240v which hopefully would give about 160v on the plates for V1 & V2.  That's what I would personally shoot for.  So, I'd lower the dropping resistors between B & C and between C & D.

I don't know what changes you'd need to make on the dropping resistors between B &C and C&D?  I might experiment with 10k/3w and 4.7k/3w and see what I ended up with?

I've seen reverb work well with a pretty wide range of voltages.  IF you needed more voltage for the recovery stage for the reverb, you can use node C instead of node D.

With respect, Tubenit

Thanks a lot Tubenit. I'll try using EL84.
I have read the Voltage on my current Marshall 18 Watt (green text) (See Attachment)

One more question, would be alright to use EZ81 instead 5UA4GB?

[sluckey]

One more question, would be alright to use EZ81 instead 5UA4GB?

yes

[Blackface5f6]

One more question, would be alright to use EZ81 instead 5UA4GB?

yes

Theoretically, the PT should give me :
+A 340 VDC
+B 338 VDC
+C 320 VDC
+D 287 VDC

Hopefully, it is correct and if it is correct, would that OK for Princeton Reverb with EL84 (I guess so  )
(see attachment)