Echo box project, input wanted

[separateness]

Gentlemen,
I have posted before about my oil can unit which I do very much love for some nice groovy slapback. However there are a few things about it which I simply have grown to find intolerable.  No, not the incessant noisiness of the thing.  Rather I really do not enjoy what it does to my clean signal. You see it routes the clean signal through a 7199 pentode with a huge plate resistor and although it can sound somewhat cool to overdrive the thing a little, I really just prefer the sound of my guitar going into my amp.  As such, I have begun the preparations to build a new circuit for it based on a later version of said oil can. I will use the motor assembly from the unit I have of course and rehouse it a new cabinet with a new chassis with new electronics.
The Echo Reverb III (I have the Echo Reverb II) uses two 12ax7's rather than one 7199 and I think it is a superior design.  My little innovation here is to take the III's circuit but make the dry path completely parallel to the effect path by using a couple of  cathode followers (sort of like how the 6g15 does).
My reason for posting here is to let some wiser men than I glance over what I am thinking and tell me if my idea has some merit or not.  I appreciate any and all thoughts.  Pictures should be attached. I hope they are legible.

[HotBluePlates]

... I really do not enjoy what it does to my clean signal. ... I really just prefer the sound of my guitar going into my amp.  ... make the dry path completely parallel to the effect path by using ...
... tell me if my idea has some merit or not. ...

Certainly there is merit in providing a parallel Dry-path if you cannot abide (or otherwise overcome) how the Echo alters your guitar-sound.

The question is whether rebuilding & modifying this Echo-Reverb II in this manner is the best choice.  What about:

• Buying an Echo-Reverb III rather than modifying/rebuilding this unit?  Are you sure the Echo-Reverb III is "better" than the Echo-Reverb II?
• What about buying an off-the-shelf solution for the parallel-path, like the Wet Box? Such products can be re-used with other pedals or in other applications if you decide it didn't do what you hoped with the Fender Echo (or if you happen to be using some other setup instead of the Fender Echo).

Last item to note:  have you played through an Echo-Reverb III?  I see a T-filter that will impose a significant mid-scoop to the echo (and multiplied in the feedback/reverb sound).

[separateness]

... I really do not enjoy what it does to my clean signal. ... I really just prefer the sound of my guitar going into my amp.  ... make the dry path completely parallel to the effect path by using ...
... tell me if my idea has some merit or not. ...

Certainly there is merit in providing a parallel Dry-path if you cannot abide (or otherwise overcome) how the Echo alters your guitar-sound.

The question is whether rebuilding & modifying this Echo-Reverb II in this manner is the best choice.  What about:

• Buying an Echo-Reverb III rather than modifying/rebuilding this unit?  Are you sure the Echo-Reverb III is "better" than the Echo-Reverb II?
• What about buying an off-the-shelf solution for the parallel-path, like the Wet Box? Such products can be re-used with other pedals or in other applications if you decide it didn't do what you hoped with the Fender Echo (or if you happen to be using some other setup instead of the Fender Echo).

Last item to note:  have you played through an Echo-Reverb III?  I see a T-filter that will impose a significant mid-scoop to the echo (and multiplied in the feedback/reverb sound).

I have been unable to find an ERIII for sale and do not anticipate this changing much. Oil cans do pup up but most often they seem rare as hen's teeth. I would like to have one one day though. 

As to whether it is better or not, I really cannot say but the story I have made up in my head from whole cloth is that the earlier versions were done cut rate for a less-proven product and the added expense of two (rather than one) tube is some indicator of a better quality circuit in the later versions. I understand old radios can be very roughly appraised this way.  There are a few things that look outright better on paper to me (no telling if reality is there to match) such as the 'reverb' (really more of a regen control) path looking much more capable of pushing long tails, using two cascaded gain stages to get the necessary ~30 volt signal into the can rather than one (better for S/N?).  Also I like the sound of a pushed 12ax7 if it comes to that whereas I have found that a pushed small signal pentode can sound interesting but often very unforgiving/harsh. Really getting the 7199 screen voltage set where you get good echo and good guitar sound and good noise is a bit of a trick.  The T filter is a little wacky but I thought maybe I'd try it and ditch it or modify it if it turns out nasty.

Your suggestion for a wet box is of course extremely prudent, but I fear prudence is rarely my strong suit. Of course I am here for such wise council and I may take your suggestion.
Do you think the circuit I have drawn has any glaring weaknesses?

[Willabe]

No tubes, SS, but I love mine. No fuss, no muss, you can get them used for ~$140.
Catalinbread ADINEKO

i=ShhqM5YcJ0GMJA-l

[Willabe]

And they have a newer version, Adinecho Ghost.

i=n6wJhSeqie5nevi2

[HotBluePlates]

Do you think the circuit I have drawn has any glaring weaknesses?

U2B is duplicating the job already done by U3A.

I can't really articulate the difference, but an original 6G15 doesn't sound "uncolored" with respect to the Dry signal.  I have a 1965 original.   

I have been unable to find an ERIII for sale ...

There are 2 of them for sale on Reverb.com right now (plus a few Echo-Reverb II examples).  Kinda pricey though.

As to whether it is better or not, I really cannot say but the story I have made up in my head from whole cloth is that ... the added expense of two (rather than one) tube is some indicator of a better quality circuit in the later versions. ...

The 7199 is a relatively uncommon and expensive tube, and the 12AX7 is widely available from everyone.
Two 12AX7 triode sections replace the pentode-section of the 7199, and afford a spot to insert a T-filter for mid-scoop between sections.
One triode of the other 12AX7 replaces the triode-section of the 7199.
The other section of that tube seems to be used "because it is available" as a grounded-grid amplifier, in the same way the 7199's pentode-section was used in grounded-grid mode for the "Reverb" feedback.

If I were going to buy an Echo-Reverb, I would get the "III" version, only because I have plenty of 12AX7s and don't want to be locked in to more expensive 7199s.

[separateness]

I assumed any one wanting over a grand for these things was either lying or nuts.  They are noisy and finicky as hell.  I got mine for 450 some time back.  No way am I going to pay a grand for one.  Looking at the price of wet boxes, they seem to be about a hundred on the low end.  For about twice that I can waste a bunch of my time soldering some stuff and maybe accidentally learning something.

Do you think the 7199 was significantly more expensive back when the ERII was made?  Genuine question, as I have no idea.  One thing is you can swap in a 6BM8 with a little rewiring and they are still cheap.  My interpretation of that last triode on the ERIII was that it was working like a paraphase, buffering the Echo output but providing actual voltage gain for the Reverb feedback path. I am probably wrong though.

U2B is there mostly to mitigate possible tone suck that I have seen mentioned when people are talking about the 6g15. I don't use long cable runs though so it is probably not doing much for me. There was a later Fender Reverb box that was made in the 70s that I used as a sort of model for this idea (basically just boosting the signal in some way after mixing). I will say that I tend to prefer to plug into my amp without a buffer so it might very well be that I won't like this idea for a clean path much either, but I might like it as a better compromise. I don't know what it is but I just like the way the dynamics feel a little better going straight in.

[roarshock]

I'm seeing some smart folks suggest a pedal might be just as pleasing, if not more. You seem pretty excited to follow your dream here. If folks are selling those units for anything close to 1k, consider what value you may lose by tearing it up. That said, its yours. If you want to redo it, let the solder flow. I'd recommend a 6U8A or 6AN8 (iirc) for a 7199. A 6BM8 has a more powerful pentode than a 7199.

[HotBluePlates]

... Do you think the 7199 was significantly more expensive back when the ERII was made?  Genuine question, as I have no idea. ...

I was not yet a gleam in my dad's eye when the ERII was made.  But I did get lucky & obtain some old retail price lists in several tube caddies I bought over time.

The 1965 Tung Sol price list below shows a 7199 is about double the price of a 12AX7.
   - I have other price lists copied out of 1960s Allied catalogs that show lower prices for both tube types.  However, 7199 is still about 2x the cost of a 12AX7.

... One thing is you can swap in a 6BM8 with a little rewiring and they are still cheap. ...

The 6BM8's pentode is a "power tube" so it's like saying you'll use a 6V6 instead of a 12AX7.  The 7199 pentode's role in the ERII is a preamp voltage-amplifier.

... I can waste a bunch of my time soldering some stuff and maybe accidentally learning something. ... I will say that I tend to prefer to plug into my amp without a buffer so it might very well be that I won't like this idea for a clean path much either, but I might like it as a better compromise. ...

I'm seeing some smart folks suggest a pedal might be just as pleasing, if not more. ...

Some days I just get lazy about this stuff, and buying something that "does the thing right now" is an appealing option if the price is right.  That said, your circuit should work fine and you are right that it an excuse to try things out & learn something.