changing classic 18 watt to 18 watt modern classic

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Re: changing classic 18 watt to 18 watt modern classic

Post by JMPGuitars »

Bieworm wrote:
Fri 05/08/20 12:38 am
Nope, just delay and reverb. Tried the dirtortion too, but...no, no not that one ;-)
I'm building it in my tremolo TMB too. But I have only got the standard neutric jack inputs at hand, so they ground directly on the chassis. Am I looking for trouble this way? I'm using shielded wires and intend to connect the single grounding side at the input jack. The metal inputs make it more obvious which inputs are FX loop and what input is the guitar IN...since I have the loop inputs on the frontpanel.

Is it normal for the loop working in both ways. It doesn't matter which input goes to either side of the effects.. I thought the send and return should stand for something?
That's odd that you have less gain when using the loop. Maybe this is related to not paying attention to which jack is the send jack?

Yes, you're potentially looking for trouble not using isolated jacks. Did you know, that you can label things on the panel? ;)

Send and Receive does matter. If you reverse them, then you're relooping your loop. But yes, I would expect the loop to be audible regardless of which way you insert your effects.
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Re: changing classic 18 watt to 18 watt modern classic

Post by Bieworm »

JMPGuitars wrote:
Fri 05/08/20 7:09 am
Bieworm wrote:
Fri 05/08/20 12:38 am
Nope, just delay and reverb. Tried the dirtortion too, but...no, no not that one ;-)
I'm building it in my tremolo TMB too. But I have only got the standard neutric jack inputs at hand, so they ground directly on the chassis. Am I looking for trouble this way? I'm using shielded wires and intend to connect the single grounding side at the input jack. The metal inputs make it more obvious which inputs are FX loop and what input is the guitar IN...since I have the loop inputs on the frontpanel.

Is it normal for the loop working in both ways. It doesn't matter which input goes to either side of the effects.. I thought the send and return should stand for something?
That's odd that you have less gain when using the loop. Maybe this is related to not paying attention to which jack is the send jack?

Yes, you're potentially looking for trouble not using isolated jacks. Did you know, that you can label things on the panel? ;)

Send and Receive does matter. If you reverse them, then you're relooping your loop. But yes, I would expect the loop to be audible regardless of which way you insert your effects.
Dang! In that case I shall isolate the inputs with heatshrink and plastic washers for now..
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Re: changing classic 18 watt to 18 watt modern classic

Post by Bieworm »

https://www.dropbox.com/s/78nko8k9k85g3 ... p.m4a?dl=0

I think this one needs the ruby mod too...
And notice the gain of grind when the FX loop is unplugged
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Re: changing classic 18 watt to 18 watt modern classic

Post by JMPGuitars »

Bieworm wrote:
Sat 05/09/20 4:21 am
I think this one needs the ruby mod too...
And notice the gain of grind when the FX loop is unplugged
What's your cathode capacitor value in this one?
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Re: changing classic 18 watt to 18 watt modern classic

Post by Bieworm »

JMPGuitars wrote:
Sat 05/09/20 6:14 am
Bieworm wrote:
Sat 05/09/20 4:21 am
I think this one needs the ruby mod too...
And notice the gain of grind when the FX loop is unplugged
What's your cathode capacitor value in this one?
1000uf 63V
I have a 2200uf in stock, but it's not axial and looks weird if I stick it on the board... it has to look nice too huh

In the tremolo TMB it's 1500uf
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Re: changing classic 18 watt to 18 watt modern classic

Post by JMPGuitars »

Bieworm wrote:
Sat 05/09/20 7:32 am
1000uf 63V
I have a 2200uf in stock, but it's not axial and looks weird if I stick it on the board... it has to look nice too huh

In the tremolo TMB it's 1500uf
You should probably try the Ruby mod. But I would also increase the cathode cap. Maybe order some axial 2200uF when you order some proper jacks for your effects loops?

Your other amp sounds better than this one. Another difference is the power tube bias. The other amp is baised under 11W, and this one is almost maxed out nearing 12W. Maybe order yourself some 200R and 220R 5W resistors and see how it goes. Post some wide photos showing the guts of this build.
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Re: changing classic 18 watt to 18 watt modern classic

Post by Bieworm »

JMPGuitars wrote:
Sat 05/09/20 8:13 am
Bieworm wrote:
Sat 05/09/20 7:32 am
1000uf 63V
I have a 2200uf in stock, but it's not axial and looks weird if I stick it on the board... it has to look nice too huh

In the tremolo TMB it's 1500uf
You should probably try the Ruby mod. But I would also increase the cathode cap. Maybe order some axial 2200uF when you order some proper jacks for your effects loops?

Your other amp sounds better than this one. Another difference is the power tube bias. The other amp is baised under 11W, and this one is almost maxed out nearing 12W. Maybe order yourself some 200R and 220R 5W resistors and see how it goes. Post some wide photos showing the guts of this build.
The inputs are the proper ones..I found those among my stash

As for the biasing.. would a 2.2K between the 32uf caps help? It's so odd... with the same transformers, same tubes and components values that results in such a difference? But there are 10k gridstoppers on the powertubes instead of 8.2k. that shouldn't matter I guess?
15890314093244920558343641628731.jpg
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Re: changing classic 18 watt to 18 watt modern classic

Post by Bieworm »

Ok I tested the amp with a trial setup. 2x100R in series across a 2200uf cap.. it looks like sh*t but just serves as trial setup.
The new parts are ordered. I followed your advice and ordered some 180R, 200R and 220R 5W resistors along with some other stuff I need.
Also did the richie resistor mod on the trem (1M to 470k)
Something weird happened with the plates and cathodes on V2. Can't be that resistor mod when the trem is not engaged... trem sounds great nevertheless ...
I noticed that the intensity pot works counterclockwise.. so the ground must be swapped to the 3rd lug..
BUT overall think the amp sounds better, but cleaner again... I like that. Have the tremolo TMB for crunch anyway..
BUT suppose I wanted crunch earlier on the dial... is lowering the plate and cathode voltages going to take me there?
Tubes run at 10.1 watts now
Here is the chart
15891034454446016304693400614269.jpg
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Last edited by Bieworm on Sun 05/10/20 6:11 am, edited 1 time in total.
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Re: changing classic 18 watt to 18 watt modern classic

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Re: changing classic 18 watt to 18 watt modern classic

Post by JMPGuitars »

Your preamp plates are high. If you want more dirt, adjust those closer to the voltage chart.

Clean up your chassis. You've got bits of stuff stuck in a lot of spots. Looks like at least some of those bits are solder.
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Re: changing classic 18 watt to 18 watt modern classic

Post by Bieworm »

JMPGuitars wrote:
Sun 05/10/20 6:52 am
Your preamp plates are high. If you want more dirt, adjust those closer to the voltage chart.

Clean up your chassis. You've got bits of stuff stuck in a lot of spots. Looks like at least some of those bits are solder.
I scraped and vacuumed it. In the beginning I held down wires with tape. It's glue rests from that... it's safe , don't worry...
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Re: changing classic 18 watt to 18 watt modern classic

Post by Bieworm »

Got the plate voltage to spec. After trying some values I ended up adding a 56k resistor in series with the 100k from C to the plate of V2
1589121364759592339701857854629.jpg
This shows how important the voltages for the trem are... now it starts oscillating immediatly when switched...
Thnx Josh!! I am learning a lot here... where to adjust component values to reach the desired voltages. A great contribution is the logic in stage placement. This lay-out is much clearer to identify what's what...
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Re: changing classic 18 watt to 18 watt modern classic

Post by crgfrench »

JMPGuitars wrote:
Tue 05/05/20 12:51 pm
Here's a recent build of mine with the FX loop:
_JMP7608.jpg
Hi Josh, That amp sounds great in your youtube video. The demo didn't include the FX loop, and I was wondering if you have any demos made of the FX loop with different pedals? I'm asking because I'm planning to include one in my current 36W (4x EL84) build.

I have 7 options for the loop:
1) this passive design that you use,
2) the Phil Rowley passive design,
3) Rob Robinette's passive design,
4) the "Zero loss" Metropolous kit with a transistor,
5) the Mojotone board with a transistor.
6) the 6N17B "All Tube" module from Saul's,
7) Merlin's 12AX7 design.

If you don't have a demo of your fx loop recorded with some pedals (or even if you do), I'd appreciate your opinion of any (or all) of these options. I'm presently leaning away from the transistor boards, just on principle, and I'm kind of liking Saul's design, it has some cool features and Trinity uses these boards.

The things I'm concerned about with the passive designs is, while they are simple and cheap, passive loops don't attenuate the send signal to a level compatible with effects; they don't provide a low impedance send which would prevent signal/tone loss; nor do they include a return gain stage to bring the attenuated signal back to where it was. However, the active options all do these things. I was curious how you and others have found the performance of these passive loops, and specifically whether anyone has compared them vs. the active type?
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Re: changing classic 18 watt to 18 watt modern classic

Post by Bieworm »

crgfrench wrote:
Fri 05/22/20 11:00 pm
JMPGuitars wrote:
Tue 05/05/20 12:51 pm
Here's a recent build of mine with the FX loop:
_JMP7608.jpg
Hi Josh, That amp sounds great in your youtube video. The demo didn't include the FX loop, and I was wondering if you have any demos made of the FX loop with different pedals? I'm asking because I'm planning to include one in my current 36W (4x EL84) build.

I have 7 options for the loop:
1) this passive design that you use,
2) the Phil Rowley passive design,
3) Rob Robinette's passive design,
4) the "Zero loss" Metropolous kit with a transistor,
5) the Mojotone board with a transistor.
6) the 6N17B "All Tube" module from Saul's,
7) Merlin's 12AX7 design.

If you don't have a demo of your fx loop recorded with some pedals (or even if you do), I'd appreciate your opinion of any (or all) of these options. I'm presently leaning away from the transistor boards, just on principle, and I'm kind of liking Saul's design, it has some cool features and Trinity uses these boards.

The things I'm concerned about with the passive designs is, while they are simple and cheap, passive loops don't attenuate the send signal to a level compatible with effects; they don't provide a low impedance send which would prevent signal/tone loss; nor do they include a return gain stage to bring the attenuated signal back to where it was. However, the active options all do these things. I was curious how you and others have found the performance of these passive loops, and specifically whether anyone has compared them vs. the active type?
Craigh, I have the one from Josh in both my 18 watts... they just simply work. No tonal change, no signal loss.. I can't imagine wanting another type of FX loop.
My 2cts
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Re: changing classic 18 watt to 18 watt modern classic

Post by JMPGuitars »

crgfrench wrote:
Fri 05/22/20 11:00 pm
Hi Josh, That amp sounds great in your youtube video. The demo didn't include the FX loop, and I was wondering if you have any demos made of the FX loop with different pedals? I'm asking because I'm planning to include one in my current 36W (4x EL84) build.

I have 7 options for the loop:
1) this passive design that you use,
2) the Phil Rowley passive design,
3) Rob Robinette's passive design,
4) the "Zero loss" Metropolous kit with a transistor,
5) the Mojotone board with a transistor.
6) the 6N17B "All Tube" module from Saul's,
7) Merlin's 12AX7 design.

If you don't have a demo of your fx loop recorded with some pedals (or even if you do), I'd appreciate your opinion of any (or all) of these options. I'm presently leaning away from the transistor boards, just on principle, and I'm kind of liking Saul's design, it has some cool features and Trinity uses these boards.
Thanks! I don't have a demo recorded, but I could record one (eventually). As Bieworm said, it does simply just work. There are very few situations where an active loop is required. For most stuff a good passive loop is all you need.

Post or link to #2, #6, and #7. I'd like to see them. Especially #2, Zaphod_Phil is Phil Rowley, so obviously I would be curious about that one if not using the one I already use.

crgfrench wrote:
Fri 05/22/20 11:00 pm
The things I'm concerned about with the passive designs is, while they are simple and cheap, passive loops don't attenuate the send signal to a level compatible with effects; they don't provide a low impedance send which would prevent signal/tone loss; nor do they include a return gain stage to bring the attenuated signal back to where it was. However, the active options all do these things. I was curious how you and others have found the performance of these passive loops, and specifically whether anyone has compared them vs. the active type?
I don't agree with your statement. As I stated above, most situations work fine with a passive loop. If I was going to do an active loop, I would go with a tube implementation, and Merlin does generally know what he's talking about. I wouldn't use a kit if I was going to go transistor route. What's the point when you can find a good schematic and order the parts yourself?

Consider this. My loop is 5 inexpensive parts. You can experiment with it for yourself, and if it's not sufficient, try a different one. You'll need the fx jacks mounted either way.

Thanks,
Josh
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