Small Special with Merlin effects loop

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telentubes
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Small Special with Merlin effects loop

Post by telentubes »

Started this about a week ago. It has 50 watt MC transformers and will have an effects loop (Merlin's book, page 219) as implemented by xtian a while back.
I'm leaving out the bright switch, as well as the deep switch as I have never used (liked ) them on any of the D style amps. 'Nuther couple of weeks and it should be up and running, providing the effects loop works as planned. Will cross the speaker bridge after it's finished, and plan on putting it in a combo cab. Watts Audio 17.5 X 8 X 2.5" chassis blank. Stained curly maple face plate sealed with True-Oil.

There is a 47uf/500V filter cap in the first position that I will trade out for two 100uf/350V (or 450V) when I place another order for caps. That's what the extra space on the board is for.

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M Fowler
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Re: Small Special with Merlin effects loop

Post by M Fowler »

That looks great very nice layout.

The Small Special is very much an amp I want to build sometime because I believe it will be a large sounding tone machine effect pedal pushing platform.
telentubes
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Re: Small Special with Merlin effects loop

Post by telentubes »

I could have switched the placement of the V2 plates and the V1B cathode on the board.

I would recommend building this amp to you. It's like the Dumble version of the Rocket. Simple, good with pedals, and rich tone right out of the box.
Last edited by telentubes on Sun Oct 01, 2017 6:28 pm, edited 1 time in total.
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stelligan
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Re: Small Special with Merlin effects loop

Post by stelligan »

Sweet looking build! I must build one someday.
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jelle
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Re: Small Special with Merlin effects loop

Post by jelle »

These are sweet amps. :-)
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Colossal
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Re: Small Special with Merlin effects loop

Post by Colossal »

Looks great!

How would you describe or compare the tone of these amps?
telentubes
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Re: Small Special with Merlin effects loop

Post by telentubes »

It is similar to the 124 clean channel. Maybe a little more mid range (correction: than a Fender), and maybe a little more string definition. I find that it's much easier to dial in a balanced tone than on my 124.
I imagine that it has Bassman-like qualities. Full meaty satisfying tone. I don't know what the breakup point is per se, because I'm more interested in clean amps than over-driven, and it is too loud when cranked, for what I do these days. I don't play in rock bands anymore so don't have the drummer comparison to make, although I think it would be fine in a band that played at moderate club volumes.
It is definitely less mid scooped than the JM Signature.
I have a 124, the new Champ (which is great by the way) and a JM signature on hand, which I can ABCD when the Small Special is done. I will report back. Of course, speakers make a difference.
My Rocket is out on loan so not available for comparison.
Last edited by telentubes on Mon Oct 02, 2017 9:11 pm, edited 1 time in total.
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Colossal
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Re: Small Special with Merlin effects loop

Post by Colossal »

telentubes wrote: Mon Oct 02, 2017 2:46 am It is similar to the 124 clean channel. Maybe a little more mid range, and maybe a little more string definition. I find that it's much easier to dial in a balanced tone than on my 124.
I imagine that it has Bassman-like qualities. Full meaty satisfying tone. I don't know what the breakup point is per say, because I'm more interested in clean amps than over-driven, and it is too loud when cranked, for what I do these days. I don't play in rock bands anymore so don't have the drummer comparison to make, although I think it would be fine in a band that played at moderate club volumes.
It is definitely less mid scooped than the JM Signature.
I have a 124, the new Champ (which is great by the way) and a JM signature on hand, which I can ABCD when the Small Special is done. I will report back. Of course, speakers make a difference.
My Rocket is out on loan so not available for comparison.
Thanks! This is very helpful and descriptive. Sounds like a great amp!
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jelle
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Re: Small Special with Merlin effects loop

Post by jelle »

Less mid scooped than a #124? What schematic did you work off?
mabruk
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Re: Small Special with Merlin effects loop

Post by mabruk »

Does anyone have an schematic?
10thTx
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Re: Small Special with Merlin effects loop

Post by 10thTx »

Does anyone have an schematic?
I don't know if these schematics are correct? These are some that I saved sometime ago. They may not be accurate?

with respect, 10thtx
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mabruk
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Re: Small Special with Merlin effects loop

Post by mabruk »

10thTx wrote: Mon Oct 02, 2017 10:18 am

I don't know if these schematics are correct? These are some that I saved sometime ago. They may not be accurate?
with respect, 10thtx
Both ones can work. C3 cap in the FXLoop circuit should be of much lower value. I would use a 2,2uF non electrolytic and low voltage one where the low freq. corner at that point could be at about 15hz, which is enough. The other one at the second triode cathode neither need to be 100uF. 4.7uF or 10uF could be ok.

The amp schematic lacks mid control and mid scup consequently. But the power stage design denotes an intention for it to be rather clean and with good Headroom which apparently contradict the idea seen in the preamp design. Unless the "deep" option is used since it can compensate for the other. I will also try to reduce the bright cap to 250p and try to hear if it make any improvement. Anyway I wouldn't ignore the mid control at all and forever. IMO this good design deserves to have it, even if it was optional. This amp is just an ODS without the Lead Channel. Why such a mutilation?
Last edited by mabruk on Mon Oct 02, 2017 12:01 pm, edited 1 time in total.
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M Fowler
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Re: Small Special with Merlin effects loop

Post by M Fowler »

All the schematics and layouts for 50w and 100w are in the Dumble Files section. There is also a Morgan PW50 layout too.
telentubes
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Re: Small Special with Merlin effects loop

Post by telentubes »

Sorry Jelle. Nice catch. I meant to say less scooped than a Fender. And this is just my ears talking when A/Bing amps at my house.
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