Add reverb to a 5f10 Harvard

[Edgar Sterling]

I built an amp recently in nearly exact accordance to the Fender Harvard 5f10 schematic and layout. I'm wondering how one might add reverb to this circuit. I've studied some other Fender reverb circuits, particularly the Princeton. I don't wish to imply that the process could be a simple "cut-and-paste" kind of thing, but the Princeton reverb circuit does look like it could, with a couple of tweaks, exist happily in the Harvard. Anyone ever done this? I would want to preserve as much as possible the basic tone of the Harvard, which is very nice.

[Tubenit]

Adding reverb

This reverb works just fine for my purposes. And it uses a single 12AX7. The design came from the D'Lite (sort of a Dumble clone) reverb.

I have 3 amps with this installed and I'm very happy with it. It has waaaayy more reverb than I will ever use, but would not be a good choice if you do Dick Dale surf stuff.

I have owned a Princeton Reverb and played the reverb on about "2.5" most of the time. With this reverb I dial it to "3".

It verbs more mids than the Fender type and I prefer it. If for some reason you need more reverb, simply change the reverb pot to 2.2M.

I use a dwell pot because a 1M dwell resistor was too much reverb for me.

With respect, Tubenit

[Tubenit]

adding reverb

While there are some differences between the Carolina Blues Special and the Harvard ...... there are similarities. I have built the CBS amps into tweed chassis.

I place the dwell on the bottom of the chassis, set it and leave it alone.

I add a terminal strip near the V2 socket for the reverb insertion.

Besides the numerous D'Lite builders who use this reverb and report being happy with it, you can see another example of a one tube reverb in the Gibson Scout.

If this was a vintage Fender amp instead of a clone, it would really mess up it's collectors value. I would use a reverb pedal for a vintage amp. Verbzilla or Holy Grail reverb would be reasonable considerations & you can hear examples of those on U-toob.

With respect, Tubenit

[Tubenit]

Adding reverb

Take a look at how the Gibson Scout does the one tube reverb.


I have added reverb as I am showing on option #2 here. It does work & it's oK if you tend to set your reverb and amp volume and leave them alone (adjusting volume with guitar vol). However, it is interactive with the volume and also adds some gain to the reverb (which you may or may not like?).

I have done this using the typical 5E3 tone stack and vol topology.

With respect, Tubenit

[Tubenit]

Adding reverb to Harvard

I prefer this "option 1" because it is not interactive with the volume or tone and does not add additional gain to the reverb.

Again, an effects pedal is an easier solution. Although, adding a tube to the chassis and using terminal strips around it for the component parts should work.

With this type of reverb I use typical fender replacement reverb trannies and tanks like you'd get for a Princeton Reverb.

With respect, Tubenit

[Edgar Sterling]

Thanks for your feedback, I am just getting home and will study this. I've built 4 amplifiers now (and tinkered with them alot) but haven't gotten into reverb yet. I do like a little, to add to a good clean tone. I would like to build the Fender standalone unit too, but for now, just add it to the Harvard.

[Edgar Sterling]

Awesome!

This is very valuable information and exactly what I was looking for, thank you. I want to mention, one of the subtle substitutions I made with the Harvard was the 6at6 triode. I didn't have one, but 1/2 of a 6sl7 had the same gain and I really like those tubes so that is what is in there. The other half is unused. So in addition to adding a 12ax7, could that other half of the 6sl7 be of any benefit to a reverb circuit? I've noticed in Fender circuits they run a 12AT7 in parallel as a reverb driver. Why is this done, and would it be desirable/possible to have that configuration in the Harvard (paralleled 12at7 reverb driver+transformer+tank+6sl7 recovery stage). Just curious. Either way, this mod now appears to be quite plausible. I too think I would prefer option #1 you suggested that is non-interactive with volume control.

[Edgar Sterling]

With a Champ?

Have you tried this with a Champ type circuit?

[Tubenit]

adding reverb

I have not tried this with a Champ circuit. However, I have a schematic and layout already available to attempt it but have never gotten around to it. I know on the Hoffman amp forum, that a member did successfully build a Champ with reverb. You'll need the free ExpressSCH program to view the editable schematic.

5F2-A with Reverb and 6V6, 6L6 or EL34

I am not familiar with the 6SL7 tube. I don't know why the paralleled 12AT7 for sure? Perhaps something connected to current draw and voltages. However, I prefer the one tube reverb sound which reverbs more mids, so I don't envision using a Fender type reverb ever again.

With respect, Tubenit

[pontiacpete]

Tubenit,
Is there any way you could post it here, I can't download expressSCH, I've got a mac? I'm Really interested in seeing this.
pete

[Tubenit]

reverb 5F2

Here is the GIF version of the SCH file for your viewing. This is reportedly a proven schematic built as a working amp.


There is a Jschem program for FREE on the Hoffman forum for you Mac guys that will open any SCH program.

http://www.el34world.com/Forum/index.php?topic=763.0

Also if you look on the Hoffman forum there is an entire download of maybe 150 editable schematics and layouts ........ all of which can be opened and viewed with Jschem on a Mac (from what I've been told).

http://www.el34world.com/Forum/index.php?topic=6977.0

With respect, Tubenit

[Tubenit]

Verb O Champ

If I were building a Champ type amp this is what I would do. I like paralleled V1 tubes for 30% gain and no increased idle noise.

I am not a fan of Fender tone stacks and prefer a James tone stack if just using two tone pots. The James tone stacks allow more mids than the tradition FTS.

With respect, Tubenit

[pontiacpete]

thanks Tubenit!
can't wait to hear the verb o champ!
would a princeton size verb tank work with this?

[Edgar Sterling]

Thank you, Tubenit. I'm quite new to this forum. Are you like an oracle or something? The Champ o verb is very cool. Where did you find this stuff, or do you draw them up yourself? Either way, thanks for providing them. My project goals are clear to me now.

[Tubenit]

Adding reverb

I do draw up the schematics and layouts. The reality is I just look at other people's ideas and successes and "steal" ideas from them. It's just a hobby for me.

All my experiments have worked somewhere between OK to great ..........but usually I build it and tweak it until it's what I want. I've never built a pure clone of anything and strongly prefer taking a basic concept and experimenting with it.

Regarding reverb. I've used a one tube reverb on maybe 15 + different amps. I've used various 3 different one tube reverb topologies and am sharing with you what has worked best for me.

Even when I thought I had originated a new idea........ I find out later someone had already thought of it.

There's hundreds of guys that know stuff alot better than I do. I just observe and use ideas I see. And I am willing to experiment alot to see how something sounds or impacts a tone since I lack a strong electrical engineering background.

With respect, Tubenit