Dumbleland Silver Alligator Inspired Build

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Aaron
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Re: Dumbleland Silver Alligator Inspired Build

Post by Aaron »

grtamp wrote:Hi Aaron , compliments for the incredible work!!

sorry for stupid questions, but the Twin transformer doesn't get hot?

you have to heat filament for about 7.3A or I'm wrong?

R.
At the moment I'm only running 6L6's. The schematic is labelled 6550's, but at this point I don't have the funds for bigger iron so I just used was I had.
crbowman wrote:I see what Tom is talking about.
The two 6247's listed on the schematic are actually 6267's which are EF86's.
I think it's just a typo.
Sorry Tom, yes, a typo.

Aaron
Max
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Re: Dumbleland Silver Alligator Inspired Build

Post by Max »

Aaron wrote: If anybody has any ideas I would be glad to hear some suggestions.
jay wrote:" … the feed back on the second tube is taken off the cathode of a third tube."

Source: http://ampgarage.com/forum/viewtopic.php?p=4567#4567
Cheers,

Max
Bombacaototal
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Re: Dumbleland Silver Alligator Inspired Build

Post by Bombacaototal »

Just for future reference a link to a comment which has a pdf of the original Alligator tremolo

http://ampgarage.com/forum/viewtopic.ph ... 1&start=45

The only difference between this and Aaron's is the 56k vs 100k cathode resistor on V5B
Last edited by Bombacaototal on Tue Feb 28, 2017 9:35 am, edited 1 time in total.
Bombacaototal
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Re: Dumbleland Silver Alligator Inspired Build

Post by Bombacaototal »

Here the pdf..the tremolo looks almost identical to the AA763 Tremolux (attached)

Here a comment and sound sampe of the alligator tremolo
http://ampgarage.com/forum/viewtopic.ph ... 2&start=15
AFAIK Feelin Bad Blues Blues was played on the Alligator Pentode (EF-86) Music Man amp high voltage output section..I love that tone..Deep on.. :D
Both Boarderline and Alligator SSS were origionally built for Ry
Sound reference http://www.youtube.com/watch?v=Ko8GvPZA ... re=related
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Bombacaototal
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Re: Dumbleland Silver Alligator Inspired Build

Post by Bombacaototal »

Aaron wrote: Sun Dec 01, 2013 1:53 pm Thought I would share with you my latest build. It been on and (mostly) off for the last 18 months but have really got into it over the last couple of weeks and am glad to say that I'm almost there!

Thought I would have a go at building an amp inspired by the EF86 Silver Alligator. I got most of the info from this thread, http://ampgarage.com/forum/viewtopic.ph ... sc&start=0 and the rest is guess work!

The mixer circuit has got me stumped, a lot of guessing but fingers crossed :D If anybody has any ideas I would be glad to hear some suggestions.

At the moment I'm using Twin Reverb trannies until I find some thing close to the MM trannies. So voltage will be closer to a SSS.

Thanks,
Aaron
Hi Aaron, i just went through your schematic and some older posts about this amp and marked in green discrepancies and also added additional info discussed for future reference as I know yours was not a clone but just inspired by

I think the 47uF might be 4.7uF on V1 and V2

Is the NFB connected to 4ohms? Which OT did you use?

One thing I could not understand/ verify is this comment. Is it supposed to be like V1b+V2a on SSS#001
Electron
You have the first tube right,but the feed back on the second tube is taken off the cathode of a third tube .
Lastly I am curious on your approach to mix the dry/wet signals which is a bit different from the Overdrive Reverb

Are there any pictures of this amp?
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Bombacaototal
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Re: Dumbleland Silver Alligator Inspired Build

Post by Bombacaototal »

Some interesting description of the amp

http://ampgarage.com/forum/viewtopic.ph ... ues#p69682

To complete the picture I'll add some remarks concerning the "Pentode Amp".

This amp is in many aspects a "very special" variant of a Dumbleland for guitar:

It had (when I met it) a wonderful clean sound but one very different from the DL/SSS sounds you are familar with from (e.g.) SRV live-recordings. The really "clean" sounds had much of the mellow but silvery highs of a good steel string acoustic. This "clean" sound was very elegant with a less pronounced attack. It was in no way spectacular or flashy like a SSS can sound, but more of an airy, refined and cultivated kind.

To get an idea, how the cleansounds of this amps are with tremolo and a bit of reverb listen to Ry Cooders "Crossroads" track 8, "Feelin' Bad Blues". This kind of "acoustic" sound I could easily get with the Pentode amp using a maple neck strat with usual strat single coils, jazz on, bright switch on, deep switch on (? not sure, maybe off) volume around 4 or 5, treble 9, middle 7, bass around 7 (not sure, maybe around 4), presence around 7, bit of reverb, slow tremolo.

And if you turned the input "volume" past 6 (Humbucker) or 9 (single coil) and engaged the PB you had great crunch and blues sounds with just the right amount of distortion for many kinds of blues styles.

But this is for sure not the amp for someone who is a fan of the signature SRV DL/SSS sounds. But if you like the guitar sound of this "Crossroads" take, you will not find an amp better suited. Great, great blues amp it was/is.

From a technical point of view I can add that the "Pentode Dumbleland" did not have those giant PTs and OTs you find in other Dumblelands but smaller ones that look far more usual.

Tubes and their function after what I remember what this tech told me concerning this: 2xEF (input, recovery after EQ), 7247 (reverb mix), 7025 (reverb return), 12AX7 (tremolo), 5751 (reverb send), 7025 (phase inverter), 7025 (driver), 4 x 6550A.

It did put out around 140 Watts without any distortion and had an unusual high plate voltage (output tubes) for a Dumbleland.
Aaron
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Re: Dumbleland Silver Alligator Inspired Build

Post by Aaron »

From memory, the values on the schematic is probably what I settled with in the amp. I would have started with what was posted and what was in the pics, but then re-voiced the amp for me.

NFB is on the 4 ohm. I just used Twin Reverb transformers with 6L6's.

I'm still hesitant with the LNFB V1b+V2a, actually it's V2+V3a. If V2 is a pentode, there isn't enough parts in the circuit to make it work.

This amp is exactly as Max described. With PAB and volume up, beautiful blues/rock sound.
Bombacaototal
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Re: Dumbleland Silver Alligator Inspired Build

Post by Bombacaototal »

Aaron wrote: Wed Mar 01, 2017 10:51 pm From memory, the values on the schematic is probably what I settled with in the amp. I would have started with what was posted and what was in the pics, but then re-voiced the amp for me.

NFB is on the 4 ohm. I just used Twin Reverb transformers with 6L6's.

I'm still hesitant with the LNFB V1b+V2a, actually it's V2+V3a. If V2 is a pentode, there isn't enough parts in the circuit to make it work.

This amp is exactly as Max described. With PAB and volume up, beautiful blues/rock sound.
Thanks a lot for the reply.

Ah yes, of course V2+V3a! Noted with thanks

As far as the tube layout I saw some comments on the long thread about this amp which indicated it would be 12BH7 (source below) for the cathode follower PI driver, but I understand you went with the the tube layout indicated by Max, correct?

http://ampgarage.com/forum/viewtopic.ph ... de#p277606

I'm using a 12AX7 PI with 12BH7 in the cathode driver section on my bastardized attempt at a 50 watt version of the pentode amp. It's got a little over 400v on the plates which scares me a little. However, I've been using it for a couple of months now and have had to crank it up pretty loud a few times for outdoor shows and it seems to be holding up just fine. Don't know how it would fare in a 100 watt build, but I have it from a reliable source that HAD used the 12BH7 in PI CF of the pentode amp.
I will say that the amp sounds really amazing with very tight, detailed, silky low end and absolutely no noise at all, even at high levels.
As far as the wet/dry mix circuit you probably also did on that style rather than the Overdrive Reverb style because of the 7247 tube indicated?

I think this is the pic of the original
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Last edited by Bombacaototal on Sun Mar 12, 2017 6:49 pm, edited 1 time in total.
Bombacaototal
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Re: Dumbleland Silver Alligator Inspired Build

Post by Bombacaototal »

Aaron, I found the pic of the back of this amp and now it makes sanse why you used a 12ax7 as cathode follower. The 12BH7 would mean a taller bottle which does not seem to be the case

Also found this http://ampgarage.com/forum/viewtopic.ph ... de#p174498
The "Pentode Amp" was a very different beast: 2x EF86 to replace the two systems of the usual input tube embedded in a very complex structure (to do as well some special tricks, like "sustain", I suppose), 12AX7 oscillator, 5751 reverb driver, 7025 reverb recover, 12DW7 mixer, 7025 phase inverter , 7025 driver, more "normal looking" OT and PT.
Silver-Aligator" "Pentode-Dumbleland" (the one that came back to US from Japan and was sold at Overland Express) was the "sustain master" (After hitting a chord you always looked around and asked yourself "where is the compressor"?)
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Bombacaototal
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Re: Dumbleland Silver Alligator Inspired Build

Post by Bombacaototal »

This seems to be a blurry pic of the gut of this amp

One thing I wonder is why this amp was never on Ry Cooder's live rig. At least I've never seen it. Maybe he didn't like the sound?

Also intrigued by all these comments relating to the "normal" smaller size OT and PT whick can clearly be seen on the pic of the back.The iron is Music Man but the OT is the question mark. There are comments of either Triad or Sunn?
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Last edited by Bombacaototal on Thu Mar 23, 2017 4:39 pm, edited 1 time in total.
Bombacaototal
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Re: Dumbleland Silver Alligator Inspired Build

Post by Bombacaototal »

Aaron, I came across the circuit of Ampeg V4 (with reverb) which uses 12DW7 mixing tube. I wonder if this might have been what the Silver Alligator had? I find these old schematics so confusing, still trying to understand what is going on there. 6k11 tube looks unique
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pompeiisneaks
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Re: Dumbleland Silver Alligator Inspired Build

Post by pompeiisneaks »

I actually spent a TON of time preparing to build this amp, and decided against it at the last minute hearing they were prone to a lot of failures. the 6K11 is a compactron 12 pin tube, seems really cool, but also not made anymore, so I was going to replace it with the unused triode of the 12AX7 in the reverb circuit and another 12DW7 like is used right after it (that whole part of the circuit is just to manage the adjustable mid through the inductor chain etc. pretty cool but most people that had one couldn't figure out how to even use it :P

~Phil
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Bombacaototal
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Re: Dumbleland Silver Alligator Inspired Build

Post by Bombacaototal »

pompeiisneaks wrote: Thu Mar 23, 2017 5:25 pm I actually spent a TON of time preparing to build this amp, and decided against it at the last minute hearing they were prone to a lot of failures. the 6K11 is a compactron 12 pin tube, seems really cool, but also not made anymore, so I was going to replace it with the unused triode of the 12AX7 in the reverb circuit and another 12DW7 like is used right after it (that whole part of the circuit is just to manage the adjustable mid through the inductor chain etc. pretty cool but most people that had one couldn't figure out how to even use it :P

~Phil
Thanks for the comment Phil. I heard this amp and thought it sounded good so went to check the circuit

Based on your comments probably not similar to the Silver Alligator then as far as the 12DW7 goes
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Mr. dB
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Re: Dumbleland Silver Alligator Inspired Build

Post by Mr. dB »

Bombacaototal wrote: Thu Mar 23, 2017 4:18 pm Aaron, I came across the circuit of Ampeg V4 (with reverb) which uses 12DW7 mixing tube. I wonder if this might have been what the Silver Alligator had? I find these old schematics so confusing, still trying to understand what is going on there. 6k11 tube looks unique
6K11 is a triple-triode compactron, 1 section is like a 12AU7 and the other two like a 12AX7.
Bombacaototal
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Re: Dumbleland Silver Alligator Inspired Build

Post by Bombacaototal »

Aaron wrote: Wed Mar 01, 2017 10:51 pm I'm still hesitant with the LNFB V1b+V2a, actually it's V2+V3a. If V2 is a pentode, there isn't enough parts in the circuit to make it work.
Based on the comment from
Electron: You have the first tube right,but the feed back on the second tube is taken off the cathode of a third tube .
And after reading this: http://www.valvewizard.co.uk/pentode.html

I am wondering if maybe the LNFB is not like attached in the SSS #002 style with the values from the handsketch (10M, .05uF)?

Pure guessing so take it with a pinch of salt
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