Anderton '64 reissue JTM145 - any info?

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roberto
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Anderton '64 reissue JTM145 - any info?

Post by roberto »

Hi, I was looking at this amp and I would like to know if someone has some information about it:
http://m.youtube.com/watch?v=w71tBeuLn2Y

Thanks in advance
Last edited by roberto on Sun Jul 27, 2014 10:47 pm, edited 1 time in total.
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M Fowler
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Re: Anderton '64 reissue JTM145 - any info?

Post by M Fowler »

http://www.andertons.co.uk/electric-gui ... w-head.asp

A lot like the Ax84 Swampthing SE amp 6L6/EL34 tube. Single input jack you can mix the hi and lo knobs to blend or internally jumper the two input channels.

Black Star has a nice little head with 12Ax7 and 12BH7 tubes that sounds like this Marshall. Also, Ace Pepper has a layout Heavy Watter on line showing his amp similar to this Marshall uses same tube compliment.
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Re: Anderton '64 reissue JTM145 - any info?

Post by Smokebreak »

Wow that sounds really good. I've been wanting to do a 1W for a while. Thanks for sharing.
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Re: Anderton '64 reissue JTM145 - any info?

Post by Smokebreak »

The JTM1 schematic is here : http://www.handmades.com.br/forum/index ... pic=5841.0
It came out in 2012 and has fixed values in tone stack . JTM145 has parallel input stage that is jumpered and full tone stack. I would guess the core design is very similar though. Of course I can verify none of this, including the scheme;)[/url]

More good info on the JTM1 from the deigner http://www.ax84.com/bbs/dm.php?thread=460389
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roberto
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Re: Anderton '64 reissue JTM145 - any info?

Post by roberto »

Thank you very much!
I attach the schematic here, it could be helpful in the future.
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ampgeek
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Re: Anderton '64 reissue JTM145 - any info?

Post by ampgeek »

Looks like a cute little bugger! Thank you for sharing that schematic.

Any idea of the purpose/location of the two "floating schematic" bodies in the upper left (R35,R36 and C23) and lower right (D5, D6 and C2)? They both have signal and earth ground connection points.

TIA,
Dave O.
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Re: Anderton '64 reissue JTM145 - any info?

Post by Smokebreak »

At the end of that 5 page thread, there is an updated scheme from just a couple of weeks ago with some changes. also in that thread is a link to a much larger thread. I'm working my way through both with google translate :D

I've wondered about the floaties too but can make no sense of it yet. There not on this current scheme.

Can someone help me understand the .1W/1W switch. I just can't make sense of what the switch is doing mechanically. Looks like dpdt that breaks the short across the 47r and 82r for each secondary tap, but then what is going on with the 18r from ground, only to the 16ohm tap??

I just ordered a chassis from Watts and Hammond 269EX and 125A. I'm gonna do an eyelet layout.

Oh another thing that doesn't make sense, straight from Marshall/Anderton's, is that the channels are "internally jumpered" in the JTM145, but it also only has 2 12ax7s, like this JTM1. There's no way.They'd need another triode. I then came across a post by the designer on ax84, where he said he was simulating the frequency responses of the jumpered channels with the JTM1 design(note 1st stage cathode). To me, this seems obvious that they did the same thing with the JTM145, and it's all hype. I figure the JTM145 is like a VERY similar circuit, with full tonestack, in a nicer box.

Here's the current
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Re: Anderton '64 reissue JTM145 - any info?

Post by Smokebreak »

I came up with a board layout for the JTM1 1W, based on the schematic from the forum above.
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mhartman
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Re: Anderton '64 reissue JTM145 - any info?

Post by mhartman »

Looks like fun. Where are you guys getting your transformers for this build?
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Re: Anderton '64 reissue JTM145 - any info?

Post by Smokebreak »

I wanted to get some stuff from Matt at Musical Power Supplies but he was in the process of building some of his 2 watt PP OTs, and I couldn't wait to get started, so I just ordered 2 hammonds from AES. If I wasn't so impatient I would've gone with MPS.
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Re: Anderton '64 reissue JTM145 - any info?

Post by Smokebreak »

Can anyone help me understand the 1W/.1W switch? To me it's drawn a little strange, but it looks like ultimately you would introduce series resistance between each tap and the speaker via dpdt . What I don't get is why there is a voltage divider (R18/R14) only for the 16ohm tap.
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roberto
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Re: Anderton '64 reissue JTM145 - any info?

Post by roberto »

ampgeek wrote:Any idea of the purpose/location of the two "floating schematic" bodies in the upper left (R35,R36 and C23) and lower right (D5, D6 and C2)?
yes, it's something quite common in Marshall amps. Connects plug's earth connection with star ground point of the amp.

http://www.amparchives.com/Amp%20Archiv ... 0-02-1.gif
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roberto
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Re: Anderton '64 reissue JTM145 - any info?

Post by roberto »

Smokebreak wrote:Can someone help me understand the .1W/1W switch. I just can't make sense of what the switch is doing mechanically. Looks like dpdt that breaks the short across the 47r and 82r for each secondary tap, but then what is going on with the 18r from ground, only to the 16 ohm tap?
it's just a voltage divider: if in 1W mode it goes straight to the speaker, otherwise you have:
- for the 8ohm tap: 47ohm in series with 8ohm, and 39ohm load on the 16ohm tap
- for the 16 ohm tap: 82ohm in series with 16, plus 39ohm in parallel with both
Smokebreak wrote:Oh another thing that doesn't make sense, straight from Marshall/Anderton's, is that the channels are "internally jumpered" in the JTM145, but it also only has 2 12ax7s, like this JTM1. There's no way.They'd need another triode.
no, the don't need it. It's done by the 2k7//1uF and 10k+330uF on V1b's cathode.
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Re: Anderton '64 reissue JTM145 - any info?

Post by Smokebreak »

Thanks Roberto.
Just to clarify, we're each referencing a different schematic. The one I posted in this thread is the latest revision. The shunt(parallel) resistor in that one is 18r, and the one you are referencing is 39r.

When you say : (I'm going to change 39r to 18r, for discussion)

"it's just a voltage divider: if in 1W mode it goes straight to the speaker, otherwise you have:
- for the 8ohm tap: 47ohm in series with 8ohm, and 18ohn load on the 16ohm tap
- for the 16 ohm tap: 82ohm in series with 16, plus 18ohm in parallel with both "

Why are there 2 sets of scenarios?
To me it seems , When the .1W switch is engaged:
8ohm tap : Only 47r series resistance
16ohm tap : Lpad circuit with 82r series and 18r parallel

What am I missing here?
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roberto
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Re: Anderton '64 reissue JTM145 - any info?

Post by roberto »

Well the voltage divider is done taking into account the speaker. When I talk about 8 ohm and 16 ohm in series (for the 8 ohm and 16 ohm), I'm talking about the impedance of the speaker.
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