1 watt amp

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Bieworm
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Re: 1 watt amp

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TriodeLuvr wrote:
Thu 05/06/21 3:02 pm
Good ideas, thanks. Wasn't aware of the Reignmaker.

Jack
I have a NOS GE 5814A ... good tube for the 12AU7 purpose, no? Supposes to be great quality?
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Re: 1 watt amp

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zaphod_phil wrote:
Thu 05/06/21 2:45 pm
I have yet to see a complete schematic for the JTM1. Has your friend heard one in real life? What is he actually looking for, just a 1W amp with a generic Marshall vibe?
On the subject of self-split power amps using pentodes, check out the Pentotron for an example- http://harmonicappliances.com/pentotron/pentotron.html

OK, I just found a JTM1 schematic - http://musiciansroadhouse.com/download/ ... 0b61774c60 :D Unfortunately, it uses a 12AU7 for the power stage, but could probably be modified to use 6AU6 pentodes to more closely approximate the EL34 sound
You could substitute in the SuperLite TMB's preamp to get you closer to a real Marshall vibe. :D
Correct me if I'm wrong, but the JTM1 is a full house of components compared to the superlite TMB. Caps and resitors and caps and caps... looks like a lot , maybe too much?
I'm also really interested in that what you suggested. The superlite TMB coupled to the 6AU6 power stage. Are there any examples of a +- 1W amp with that power stage? OT type or specs.. I was planning on using the Hammond 125A which has various primary options?
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Nothing here (nt)

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nada aqui
Last edited by TriodeLuvr on Thu 05/06/21 3:45 pm, edited 2 times in total.
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Re: 1 watt amp

Post by TriodeLuvr »

Bieworm wrote:
Thu 05/06/21 3:21 pm
TriodeLuvr wrote:
Thu 05/06/21 3:02 pm
Good ideas, thanks. Wasn't aware of the Reignmaker.

Jack
I have a NOS GE 5814A ... good tube for the 12AU7 purpose, no? Supposes to be great quality?
The 5814 is a "reliable version of type 12AU7." The 5814A is additionally "tested for military use." You should be aware that the heater-cathode rating of these tubes is 100V, half the rating of type 12AU7. That would be important to keep in mind if the tube is used as a cathode follower or cathodyne splitter. Other than that, it looks very good!

Jack
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Re: 1 watt amp

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Off topic.. but building a new tele. Got a thinline body on order. Here's the neck..well headstock with the gold logo.
20210506_225341.jpg
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Re: 1 watt amp

Post by zaphod_phil »

Bieworm wrote:
Thu 05/06/21 3:33 pm
zaphod_phil wrote:
Thu 05/06/21 2:45 pm
I have yet to see a complete schematic for the JTM1. Has your friend heard one in real life? What is he actually looking for, just a 1W amp with a generic Marshall vibe?
On the subject of self-split power amps using pentodes, check out the Pentotron for an example- http://harmonicappliances.com/pentotron/pentotron.html

OK, I just found a JTM1 schematic - http://musiciansroadhouse.com/download/ ... 0b61774c60 :D Unfortunately, it uses a 12AU7 for the power stage, but could probably be modified to use 6AU6 pentodes to more closely approximate the EL34 sound
You could substitute in the SuperLite TMB's preamp to get you closer to a real Marshall vibe. :D
Correct me if I'm wrong, but the JTM1 is a full house of components compared to the superlite TMB. Caps and resitors and caps and caps... looks like a lot , maybe too much?
I'm also really interested in that what you suggested. The superlite TMB coupled to the 6AU6 power stage. Are there any examples of a +- 1W amp with that power stage? OT type or specs.. I was planning on using the Hammond 125A which has various primary options?
Actually, the JTM1 looks pretty straight forward to me. For another good example, check out the Decimator ,which has a 12AU7 power stage with a Hammond 125A OT - http://www.harmonicappliances.com/decim ... mator.html Share & Enjoy!
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Re: 1 watt amp

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zaphod_phil wrote:
Fri 05/07/21 11:45 am
Bieworm wrote:
Thu 05/06/21 3:33 pm
zaphod_phil wrote:
Thu 05/06/21 2:45 pm
I have yet to see a complete schematic for the JTM1. Has your friend heard one in real life? What is he actually looking for, just a 1W amp with a generic Marshall vibe?
On the subject of self-split power amps using pentodes, check out the Pentotron for an example- http://harmonicappliances.com/pentotron/pentotron.html

OK, I just found a JTM1 schematic - http://musiciansroadhouse.com/download/ ... 0b61774c60 :D Unfortunately, it uses a 12AU7 for the power stage, but could probably be modified to use 6AU6 pentodes to more closely approximate the EL34 sound
You could substitute in the SuperLite TMB's preamp to get you closer to a real Marshall vibe. :D
Correct me if I'm wrong, but the JTM1 is a full house of components compared to the superlite TMB. Caps and resitors and caps and caps... looks like a lot , maybe too much?
I'm also really interested in that what you suggested. The superlite TMB coupled to the 6AU6 power stage. Are there any examples of a +- 1W amp with that power stage? OT type or specs.. I was planning on using the Hammond 125A which has various primary options?
Actually, the JTM1 looks pretty straight forward to me. For another good example, check out the Decimator ,which has a 12AU7 power stage with a Hammond 125A OT - http://www.harmonicappliances.com/decim ... mator.html Share & Enjoy!
In order to marry the superlite TMB preamp to this poweramp ... is it as simple as taking the signal from the vol pot to the grid of V3A? And suppose I want the 6au6 power stage.. are there examples to do this with the superlite TMB preamp? And reference voltages for that matter?
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Re: 1 watt amp

Post by TriodeLuvr »

I'm wondering if you've thought about which output transformer to use for this? The only thing I see in a quick search is the Hammond 125A Universal. I'm put off by the 150 Hz response, but no one else seems to make anything with a high primary impedance.

Jack
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Re: 1 watt amp

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TriodeLuvr wrote:
Sun 05/09/21 11:13 am
I'm wondering if you've thought about which output transformer to use for this? The only thing I see in a quick search is the Hammond 125A Universal. I'm put off by the 150 Hz response, but no one else seems to make anything with a high primary impedance.

Jack
The 125A was the one in mind yes...
It has a variety of primary connections.. so obviously that's the best choice.
Still wondering if I'd better build the superlite TMB 1W first before I will build the clients JTM1...and maybe convince him that's the one he wants
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Re: 1 watt amp

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The thing is, if the 125A is down 1 dB at 150 Hz, it's probably about half power (-3 dB) at the bottom of a 6 string. It would be interesting to know whether the Marshall OEM transformer is available at a reasonable price, or at least how it performs in this regard for comparison.

Jack
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Re: 1 watt amp

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TriodeLuvr wrote:
Sun 05/09/21 12:38 pm
The thing is, if the 125A is down 1 dB at 150 Hz, it's probably about half power (-3 dB) at the bottom of a 6 string. It would be interesting to know whether the Marshall OEM transformer is available at a reasonable price, or at least how it performs in this regard for comparison.

Jack
Let's start with the fact I use the 125A... wgat is the better alternative in output tube? Can I do better?
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Re: 1 watt amp

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Off topic again: this is the result of the neck.. strung up:
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Re: 1 watt amp

Post by TriodeLuvr »

Bieworm wrote:
Sun 05/09/21 1:42 pm
TriodeLuvr wrote:
Sun 05/09/21 12:38 pm
The thing is, if the 125A is down 1 dB at 150 Hz, it's probably about half power (-3 dB) at the bottom of a 6 string. It would be interesting to know whether the Marshall OEM transformer is available at a reasonable price, or at least how it performs in this regard for comparison.

Jack
Let's start with the fact I use the 125A... wgat is the better alternative in output tube? Can I do better?
Low frequency response is limited by the transformer's primary inductance, as well as core size, number of turns and voltage across the winding(s). The last three each create a finite limitation regarding core flux (saturation) at low frequencies, but which of them is the most significant is something only Hammond knows. In other words, it might be possible to achieve better low end response with a certain input impedance (dependent on tube type) and output tap, or some combination of ratios vs. output power, but knowing the best combination would require access to Hammond's internal engineering data.

Hammond does provide graphs showing response of the single-ended 125ESE at various impedance ratios. Generally, the low end is extended at lower primary impedances. Output impedance (4-8-16) appears to affect only high end rolloff. If the 125A behaves similarly, and if its published response specifications are worst case (presumably the highest primary impedance), then a different tube type or other technique for using a lower Z tap might be of benefit. The problem is, triodes with lower Rp generally have larger anode structures, therefore also higher dissipation and output power. So, we're no longer dealing with a 1W amplifier. It might be possible to manage this using a resistive divider or other than optimum biasing, but that would need to be worked out as a separate issue.

All things considered, locating a transformer with better performance is a much more satisfactory (and less experimental) solution. This is a niche market though, and small transformers don't entail the profit levels of their larger cousins. Nothing seems to be available as far as I can determine, the sole exception being the Hammond single-ended design. In the end, the main question in my mind is whether the sound of the Marshall can truly be duplicated without the OEM transformer. I do know the Hammond 125 push-pull series has been used in many low power amplifiers. Unfortunately, I haven't heard any of them live, and I have no direct experience with them that might be helpful in your project.

Jack
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Re: 1 watt amp

Post by zaphod_phil »

TriodeLuvr wrote:
Sun 05/09/21 12:38 pm
The thing is, if the 125A is down 1 dB at 150 Hz, it's probably about half power (-3 dB) at the bottom of a 6 string. It would be interesting to know whether the Marshall OEM transformer is available at a reasonable price, or at least how it performs in this regard for comparison.

Jack
The reduced low end response will probably give better cut-through
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Re: 1 watt amp

Post by TriodeLuvr »

zaphod_phil wrote:
Sun 05/09/21 4:32 pm
TriodeLuvr wrote:
Sun 05/09/21 12:38 pm
The thing is, if the 125A is down 1 dB at 150 Hz, it's probably about half power (-3 dB) at the bottom of a 6 string. It would be interesting to know whether the Marshall OEM transformer is available at a reasonable price, or at least how it performs in this regard for comparison.

Jack
The reduced low end response will probably give better cut-through
Maybe not. This isn't like turning down the bass control. The electronics driving the transformer won't benefit by not having to reproduce bass notes. The loss is occurring after the active electronics, so there's no corresponding increase in mid/treble headroom. Anyway, a bigger issue here as I understand it is that this project is for someone else. They want it to sound like the Marshall.

Jack
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