18Watt.com

I'm new to the 18 watt game (and this forum) although I've been repairing and modding amps for years (mostly Fender). Anyway, I'm about to build my first amp from scratch. It will be based on the Marshall 18 watt design. My customer is inquiring about adding reverb. Before I re-design the wheel, has anyone on this forum successfully added really good sounding reverb to their 18 watt clone?

Thanks,

Since I've been lurking it's come up a few times, but I don't think anyone has gone as far as to make a schem for it, nor had detailed implementation discussions.

Use the search term reverb here. I just tried it and there's a lot of chatter on the subject (127 hits). Mostly disscussion about trying it from what I saw. And it always seems to spin off into discussion about a stand-alone tank...

If you end up giving it a shot, I know many people would be interested in hearing about your efforts. It's been talked about enough...

Thanks and good luck,

Adam

Electroid...

I've found this schematic here in one of the earlier yahoogroups messages (not sure about the poster), it might help.
Also a shot of the board.

Gabi.

Thanks Adam. I'll post whatever happens. I'll have to check and see if the customere wants to spend the $$ to make reverb happen. I would probably use the standard Fender circuit. That is the one I know best.

Thanks very much Gabstero! This might be useful. Unfortunately, there is no info on the reverb transformer or reverb tank.

I'll look up the impedance specs on the ECL82 and compare it to that of the parallel pair of 12AT7's used in the Fender design. Then the step down ratio and reverb input inpedance might be deduced.

Or... I could just just Fender circuit.

Jeff

Fender would be interesting - Surfs up!

gabstero wrote:Electroid...

I've found this schematic here in one of the earlier yahoogroups messages (not sure about the poster), it might help.
Also a shot of the board.

Gabi.

That schematic looks a lot like Mark Durham's handwriting.

--mark

The reverb tubes are probably ECC82 not ECL82. ECC82 = 12AU7

I am strongly considering trying this one out.

Norm

EBE wrote:The reverb tubes are probably ECC82 not ECL82. ECC82 = 12AU7

I am strongly considering trying this one out.

Norm

Norm,

I would double check that. Mark Durham, who drew that schematic specified a tube which is a triode/pentode combined in one glass bottle. I think ECL82 is the correct designation. IIRC, that is basically half a 12AX7 and an EL84 in one tube. Look also at a 6BM8 for the same basic tube.

Mark told me that the reverb sound was quite good with this schematic so I wouldn't hesitate to try it if you really want spring reverb.

I found that schematic along with that chassis shot when I was browsing the 18 watt yahoogroups and I don't really remember who was the poster.
There was a whole discussion thread on it.

Is Mark Durham still around?

Gabi.

Mark is still around but he has been so busy at home, he has had to withdraw from daily activity involving the 18W project.

I mentioned this new portal to him the othe rday but I don't know if he'll have time to participate at all.

Mark was a tremendous help when we first started the Yahoo 18W group. He has an incredible collection of vintage amps (especially old obscure British amps) and he knows alot about the circuits.

Graydon wrote:

EBE wrote:The reverb tubes are probably ECC82 not ECL82. ECC82 = 12AU7

I am strongly considering trying this one out.

Norm

Norm,

I would double check that. Mark Durham, who drew that schematic specified a tube which is a triode/pentode combined in one glass bottle. I think ECL82 is the correct designation. IIRC, that is basically half a 12AX7 and an EL84 in one tube. Look also at a 6BM8 for the same basic tube.

Mark told me that the reverb sound was quite good with this schematic so I wouldn't hesitate to try it if you really want spring reverb.

Thanks, Graydon

I haven't closely studied the schematic at this point. I think I would rather try one with a 12AT7 driving the reverb. I have few NOS 12AT7s in my parts bin.

According to Doyle's book, the reverb tube was an 'ECC86', not sure if he meant that or ECL86. There is not mention of anything-82.

Mark D. certainly is an antique amp afficionado. I'd be very surprised if he didn't get the ECL82 idea from an amp in his collection.

--mark

I was review the schematic of the 18 watter with the reverb added, and I see there are a number of items with no label as to the value. They can be found on the circuit from the 1/2 of the ECL82 that feeds in the PI. I would like to add this amp to my fleet, I have the 18 watter with tremolo and I am in the process of building an 18 watter with the TBM circuit in the second channel. Any help would be great!
Thanks
Bob K.