Re: 1 watt amp
Posted: Thu 05/06/21 3:21 pm
I have a NOS GE 5814A ... good tube for the 12AU7 purpose, no? Supposes to be great quality?
I have a NOS GE 5814A ... good tube for the 12AU7 purpose, no? Supposes to be great quality?
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?zaphod_phil wrote: ↑Thu 05/06/21 2:45 pmI 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 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.
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!
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!Bieworm wrote: ↑Thu 05/06/21 3:33 pmCorrect 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?zaphod_phil wrote: ↑Thu 05/06/21 2:45 pmI 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 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.
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?
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?zaphod_phil wrote: ↑Fri 05/07/21 11:45 amActually, 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!Bieworm wrote: ↑Thu 05/06/21 3:33 pmCorrect 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?zaphod_phil wrote: ↑Thu 05/06/21 2:45 pmI 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 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.
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?
The 125A was the one in mind yes...TriodeLuvr wrote: ↑Sun 05/09/21 11:13 amI'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
Let's start with the fact I use the 125A... wgat is the better alternative in output tube? Can I do better?TriodeLuvr wrote: ↑Sun 05/09/21 12:38 pmThe 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
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.Bieworm wrote: ↑Sun 05/09/21 1:42 pmLet's start with the fact I use the 125A... wgat is the better alternative in output tube? Can I do better?TriodeLuvr wrote: ↑Sun 05/09/21 12:38 pmThe 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-throughTriodeLuvr wrote: ↑Sun 05/09/21 12:38 pmThe 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
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.zaphod_phil wrote: ↑Sun 05/09/21 4:32 pmThe reduced low end response will probably give better cut-throughTriodeLuvr wrote: ↑Sun 05/09/21 12:38 pmThe 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
LOL!!! what are we trying to cut through here? The wife doing the dishes or noisy children?zaphod_phil wrote: ↑Sun 05/09/21 4:32 pmThe reduced low end response will probably give better cut-throughTriodeLuvr wrote: ↑Sun 05/09/21 12:38 pmThe 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
Are your kids baritones, and your wife a bass? Then it might help.Bieworm wrote: ↑Mon 05/10/21 1:43 amLOL!!! what are we trying to cut through here? The wife doing the dishes or noisy children?zaphod_phil wrote: ↑Sun 05/09/21 4:32 pmThe reduced low end response will probably give better cut-through
I've read people have used the hammond 125A with success. That ampmaker OT has to be ordered in the UK. I'm from Belgium, ok we're neighbors, but shipping UK-EU is not that great at the moment with all that Brexit thrash...geoff 1965 wrote: ↑Mon 05/10/21 6:48 amBieworm check out the output transformer Dd mentioned at www.ampmaker.com, 4W push/pull,bandwidth 85Hz-6K Hz,output impedance 22.5K ohms.