Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: XYZGnomon on October 06, 2021, 05:07:55 pm
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I finished my 5F1 Champ kit, and everything works as it should. I would really like to use this as a headphone practice amp (with Sony MDR-7506 Studio Monitors), but it looks like there are no commercially available solutions for this that are appropriate for a Champ. Of all of the headphone taps (a short list!), the Weber HA-50 seems about right, but it appears to be built-to-order and I'm looking for something off-the-shelf if I'm going to buy something instead of make it.
On this site: https://robrobinette.com/Deluxe_Micro.htm I see a number of wiring diagrams that include headphone outputs using a 10 Ohm resistor, but this also outputs simultaneously to a speaker and I would like to silence the speaker.
I've also seen the Rolls PM52 Headphone Tap https://rolls.com/product/PM52 and ART HeadTap https://artproaudio.com/product/headtap-headphone-tap/ that would also require the speaker to be present and producing sound.
I feel like it might be a decent project to build something like this myself, that includes a dummy load and a switch to enable the headphones and disable the speaker (and the opposite). There's plenty of room on the floor of the Champ cabinet for a project box. Can someone please point me to resources for building such a device?
Alternatively, the Rolls and ART would be viable if I could find a dummy load for their speaker outputs. Is there a commercially available product that is just a big resistor with a 1/4" phone plug? FYI I replaced the phono jack on the Champ kit with a 1/4" phone jack so I don't need any funky adapters.
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> diagrams that include headphone outputs using a 10 Ohm resistor, but this also outputs simultaneously to a speaker and I would like to silence the speaker.
Read that jack. If nothing (speaker) is plugged in, a 10Ω resistor replaces the speaker. This IS what you want. It is semi-fool-proof.
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> product that is just a big resistor with a 1/4" phone plug?
Seems easy enough to DIY. For a Champ in the USA, you can wire a 1/4" plug to a lamp's cord and install a 100 Watt *incandescent* lamp. Up to a few Volts, a 100W 120V filament is nearly speaker impedance. Alternatively figure how to enclose a 10 Watt resistor against finger-burns yet ventilate it freely. For a home with no children or cats, just bang brass tacks in a board, solder the resistor, don't leave paper or finger on it.
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Valve guitar amps sound dire when fed into a flat response full range system, eg the headphones being proposed.
It’s the particular characteristics of guitar speakers that make the rig as a whole sound great.
But I suppose it’s one of those things you may need to prove to / for yourself.
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Valve guitar amps sound dire when fed into a flat response full range system, eg the headphones being proposed.
It’s the particular characteristics of guitar speakers that make the rig as a whole sound great.
But I suppose it’s one of those things you may need to prove to / for yourself.
Great! If I give you my neighbor's phone number, will you convince them that I'm an untouchable rock and roll God?
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> product that is just a big resistor with a 1/4" phone plug?
Seems easy enough to DIY. For a Champ in the USA, you can wire a 1/4" plug to a lamp's cord and install a 100 Watt *incandescent* lamp. Up to a few Volts, a 100W 120V filament is nearly speaker impedance. Alternatively figure how to enclose a 10 Watt resistor against finger-burns yet ventilate it freely. For a home with no children or cats, just bang brass tacks in a board, solder the resistor, don't leave paper or finger on it.
This is fine.
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> diagrams that include headphone outputs using a 10 Ohm resistor, but this also outputs simultaneously to a speaker and I would like to silence the speaker.
Read that jack. If nothing (speaker) is plugged in, a 10Ω resistor replaces the speaker. This IS what you want. It is semi-fool-proof.
I could make use of input #2 for this, then? If I plug in headphones, it applies a 10 Ohm load and cuts off the speaker? Is it really that easy?
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> diagrams that include headphone outputs using a 10 Ohm resistor, but this also outputs simultaneously to a speaker and I would like to silence the speaker.
Read that jack. If nothing (speaker) is plugged in, a 10Ω resistor replaces the speaker. This IS what you want. It is semi-fool-proof.
I could make use of input #2 for this, then? If I plug in headphones, it applies a 10 Ohm load and cuts off the speaker? Is it really that easy?
When you unplug #1 the resistor switches in...I think that on Rob's schematic you would have to add a pot to control the line out level. What pdf64 said, it gonna sound like ****
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> diagrams that include headphone outputs using a 10 Ohm resistor, but this also outputs simultaneously to a speaker and I would like to silence the speaker.
Read that jack. If nothing (speaker) is plugged in, a 10Ω resistor replaces the speaker. This IS what you want. It is semi-fool-proof.
I could make use of input #2 for this, then? If I plug in headphones, it applies a 10 Ohm load and cuts off the speaker? Is it really that easy?
When you unplug #1 the resistor switches in...I think that on Rob's schematic you would have to add a pot to control the line out level. What pdf64 said, it gonna sound like ****
It will sound better than silence, which is what the amp is outputting now.
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The ideal scenario is to utilize input #2 for a headphone output, and for the cut off of the speaker to be enabled when the headphones are plugged in. Is this feasible from a remote location like this, since it's not right next to the speaker output?
Also, doesn't the volume control continue to work? Why would I need a separate volume pot for the headphones?
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Using one of the input jacks for a headphone jack is asking for trouble. Big possibility of feedback squeals when you put the OT output next to the very low level guitar input. Best to locate the headphone jack right beside the speaker jack.
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I think what their trying to tell you is using just a resistor, for the load replacing the speaker will not sound like an amp through a speaker. You wont like it, it will sound very odd.
The speaker is a reactive load and a resistor is not reactive, it's passive. The reactive load is a large part of why tube amps sound the way they do. As the speakers voice coil is moving back and forth through the magnet gap it reflects a voltage back through the OT's secondary, into the OT's primary and back to the output tubes plates. A resistor can not do this.
So guys have worked on developing reactive loads to replace the speakers reactive load. They add caps, inductors and even speakers with the paper cone cut out. Webber sells a reactive load with this cone-less speaker, 'speaker motor'.
Search reactive load for guitar amps and read up on them.
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This might be helpful to you? This does not have a 'speaker motor', cone less speaker. From Akien amps web site;
https://www.aikenamps.com/index.php/designing-a-reactive-speaker-load-emulator (https://www.aikenamps.com/index.php/designing-a-reactive-speaker-load-emulator)
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The freq response and impedance response of a guitar speaker are different sets of characteristics, but they work together, and the latter interacts with the pentode output stages we use, to develop the tone and response we know and love.
To get it right, both will need to be mimicked.
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The freq response and impedance response of a guitar speaker are different sets of characteristics, but they work together, and the latter interacts with the pentode output stages we use, to develop the tone and response we know and love.
To get it right, both will need to be mimicked.
Did you read the link?
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https://www.marshallforum.com/threads/simple-attenuators-design-and-testing.98285/
This is an excellent attenuator. I recently built one for my (too loud) Bassman, and it works great.
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Another more expensive option is a Weber Mini-Mass attenuator with the headphone option. But it's a lot of money to solve the problem, unless you work on tube amps alot then the attenuator is very handy.
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This should be exactly what you asked for. Put it in a small enclosure box and attach to the side or bottom of your cab.
Plug box into your amp speaker jack. Plug your speaker into the box. With no headphones plugged in, your sound goes to the speaker. Plug in the headphones and the speaker is disconnected, the 8Ω dummy load is connected and the sound goes to the headphones.
Use a TRS to TS adapter if you want hear sound in left and right ears.
https://www.amazon.com/Hosa-GPP-290-TRS-TS-Adaptor/dp/B000068O4M/
EDIT... corrected speaker jack type in pic
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This should be exactly what you asked for. Put it in a small enclosure box and attach to the side or bottom of your cab.
Plug box into your amp speaker jack. Plug your speaker into the box. With no headphones plugged in, your sound goes to the speaker. Plug in the headphones and the speaker is disconnected, the 8Ω dummy load is connected and the sound goes to the headphones.
Use a TRS to TS adapter if you want hear sound in left and right ears.
https://www.amazon.com/Hosa-GPP-290-TRS-TS-Adaptor/dp/B000068O4M/
Does it matter if the speaker jack is normally closed (12A) or normally open (12B)?
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Does it matter if the speaker jack is normally closed (12A) or normally open (12B)?
All you need is a switchcraft 12. You can use a 12A but don't connect anything to the switch (shunt) lug. 12B is a stereo jack and has no switch functions. You can certainly use a 12B, but why? Heck, you could even just use an RCA phono jack and never risk plugging the speaker into the headphone jack (maybe the best idea!).
The important jack is that Switchcraft 13A transfer jack. My circuit will not work without it.
https://www.tubesandmore.com/products/jacks_plugs?filters=654a754c212a654c2341a2452
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The freq response and impedance response of a guitar speaker are different sets of characteristics, but they work together, and the latter interacts with the pentode output stages we use, to develop the tone and response we know and love.
To get it right, both will need to be mimicked.
Did you read the link?
Not on this occasion, though, as with all of Aiken’s articles, I’ve done so many times previously.
The Bode plots of a typical Champ speaker illustrate the point I was hoping to make https://www.jensentone.com/specification-sheet/22
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Does it matter if the speaker jack is normally closed (12A) or normally open (12B)?
All you need is a switchcraft 12. You can use a 12A but don't connect anything to the switch (shunt) lug. 12B is a stereo jack and has no switch functions. You can certainly use a 12B, but why? Heck, you could even just use an RCA phono jack and never risk plugging the speaker into the headphone jack (maybe the best idea!).
The important jack is that Switchcraft 13A transfer jack. My circuit will not work without it.
https://www.tubesandmore.com/products/jacks_plugs?filters=654a754c212a654c2341a2452
https://switchcraft.com/Category_Multi.aspx?Parent=952
There are only 12A and 12B. 12 does not exist.
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Does it matter if the speaker jack is normally closed (12A) or normally open (12B)?
All you need is a switchcraft 12. You can use a 12A but don't connect anything to the switch (shunt) lug. 12B is a stereo jack and has no switch functions. You can certainly use a 12B, but why? Heck, you could even just use an RCA phono jack and never risk plugging the speaker into the headphone jack (maybe the best idea!).
The important jack is that Switchcraft 13A transfer jack. My circuit will not work without it.
https://www.tubesandmore.com/products/jacks_plugs?filters=654a754c212a654c2341a2452
https://switchcraft.com/Category_Multi.aspx?Parent=952
There are only 12A and 12B. 12 does not exist.
Please excuse me. I spoke wrong When I said 12, I should have spoke 11.
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https://www.marshallforum.com/threads/simple-attenuators-design-and-testing.98285/
This is an excellent attenuator. I recently built one for my (too loud) Bassman, and it works great.
Could you share a schematic that worked for you? The thread is very long and you have to register to see the pictures.
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Here's the Switchcraft 13A https://www.tubesandmore.com/products/14-jack-switchcraft-mono-transfer-circuit
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Could you share a schematic that worked for you? The thread is very long and you have to register to see the pictures.
Here you go:
If you do register, the (up-to-date) "schematic" is right up front, with no scrolling.
The M2 works quite well to my ear by taming my "beast" Bassman.
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I'm not "registered" and I saw that scheme.. and almost all other pictures and graphics the OP posted. It was only some pics in replys to the OP that weren't able to be clicked on and enlarged.
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Does it matter if the speaker jack is normally closed (12A) or normally open (12B)?
All you need is a switchcraft 12. You can use a 12A but don't connect anything to the switch (shunt) lug. 12B is a stereo jack and has no switch functions. You can certainly use a 12B, but why? Heck, you could even just use an RCA phono jack and never risk plugging the speaker into the headphone jack (maybe the best idea!).
The important jack is that Switchcraft 13A transfer jack. My circuit will not work without it.
https://www.tubesandmore.com/products/jacks_plugs?filters=654a754c212a654c2341a2452
https://switchcraft.com/Category_Multi.aspx?Parent=952
There are only 12A and 12B. 12 does not exist.
Please excuse me. I spoke wrong When I said 12, I should have spoke 11.
Is there any reason I can't use a 13B (3 conductor, 4 contacts) https://www.digikey.com/en/products/detail/switchcraft-inc/13B/109553 in place of the 13A (2 conductor, 4 contacts) https://www.digikey.com/en/products/detail/switchcraft-inc/13A/109536 and tie the L&R lines together, instead of using the Hosa adapter? What does the 13A & Hosa adapter accomplish that I can't do with a stereo jack?
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13B will not work in my simple circuit.
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13B will not work in my simple circuit.
Can you elaborate?
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no
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13B will not work in my simple circuit.
Can you elaborate?
I ordered the components for your circuit. For tidiness, I decided not to direct wire it, and instead have three (WELL LABELED) jacks. I'll report back when it's done.
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13B will not work in my simple circuit.
Now that I have the components in my hands, I can see the special function of the 13A jack - it transfers the signal from one circuit to another.
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Works like a Champ! It sounds basically identical to the speaker, but it's definitely too loud, even in input #2.
Things I would change:
1) remote switch instead of the switching input
2) stereo
3) attenuation
It's kind of a mess with the project box I got, so I'm going to look around a little
(https://i.imgur.com/4FBT720.jpg)
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In V2, I think I am going to integrate an L-pad into the circuit, and a three-position chicken head switch instead of the switching mono headphone input.
Position 1 would be direct to speakers
Position 2 would be rerouted through the L-pad and then to the speakers
Position 3 would be rerouted first through the L-pad and then through sluckey's circuit (minus the switching jack)
I think it would make sense for the headphones to be off in positions 1 and 2.
If anybody reading this has already built such a thing, and/or knows this won't work, I'd like to hear from you. I have a lot to learn.
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I would just get one of the cheap headphone amps on Amazon
I have one of the Behringer HA400's and it works great
https://www.amazon.com/Behringer-HA400-Ultra-Compact-4-Channel-Headphone/dp/B000KIPT30/ref=sr_1_8?th=1
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I would just get one of the cheap headphone amps on Amazon
I have one of the Behringer HA400's and it works great
https://www.amazon.com/Behringer-HA400-Ultra-Compact-4-Channel-Headphone/dp/B000KIPT30/ref=sr_1_8?th=1
Thanks for the input. Are you saying to just plug it into my existing project box setup, or something else?
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Thanks for the input. Are you saying to just plug it into my existing project box setup, or something else?
You just have to feed it a pre amp level signal
The guys here can help with that
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> diagrams that include headphone outputs using a 10 Ohm resistor, but this also outputs simultaneously to a speaker and I would like to silence the speaker.
Read that jack. If nothing (speaker) is plugged in, a 10Ω resistor replaces the speaker. This IS what you want. It is semi-fool-proof.
I think I understand this now. It uses the same switching jack (Switchcraft 13A) as sluckey's circuit, but as the speaker output and defaults to the headphone output if the speaker isn't there. I like that!
Seems like this would be easy to wire, and there wouldn't be anything external to the chassis. If I had to I could drill a hole in the rear panel for the headphone jack, and it wouldn't necessarily look too out of place. Or is there a better way? I don't think there's much room on the bottom of the chassis for another phone jack, plus there's the heat of the tubes.
I still like the idea of using one of the input jacks for a headphone jack, but I get why that wouldn't be optimal. I have been looking at aircraft recessed jack housings, and I think I can pull this off by cutting out a window on the back panel. I could use the circuit you provided or even theoretically sluckey's or EL34's.
All I know is I want to use the Champ as a headphone amp and not have a lot of external devices and cables hanging out or have to plug headphones into a weird contraption somewhere deep in the base of the machine while dodging hot tubes.
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It uses the same switching jack (Switchcraft 13A) as sluckey's circuit, but as the speaker output and defaults to the headphone output if the speaker isn't there.
You don't want to drive either your headphones or a headphone amp with your speaker output! You'll likely damage your gear if you try this . . .
Usually the signal for a headphone amp is taken from the pre-amp via a voltage divider or a switch.
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It uses the same switching jack (Switchcraft 13A) as sluckey's circuit, but as the speaker output and defaults to the headphone output if the speaker isn't there.
You don't want to drive either your headphones or a headphone amp with your speaker output! You'll likely damage your gear if you try this . . .
Usually the signal for a headphone amp is taken from the pre-amp via a voltage divider or a switch.
I have said already that I have a lot to learn. Please educate me with a wiring alternative.
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I’m trying super hard not to beg, but I really just want to build this already. How would YOU (out there in TV Land) modify YOUR Champ to output to headphones?
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How would YOU (out there in TV Land) modify YOUR Champ to output to headphones?
I just wouldn't.
Instead, I'd purchase one of the many "micro-amps" out there designed for use with headphones. Fender makes a nice one, but there are lots and they are tailored to a specific sound. I've listened to a Vox voiced one, and the Fender Mustang, both sounded quite good to my admittedly sound damaged ears.
You certainly can alter the circuit of your amp to accomplish your goal, but it is not trivial. You would have a lot of learning to do, a lot of experimenting, and it would take a fair amount of time. In addition, unless you invest in some serious gear to mimic your Champs output tube -- this is what the voiced micro amps actually do -- it can't sound like your Champ.
For me, not worth the time and effort for the stated goal.
IF you are more interested in learning, spending time and bucks working on amps, and that is the goal, then definitely proceed.
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How would YOU (out there in TV Land) modify YOUR Champ to output to headphones?
I just wouldn't.
Instead, I'd purchase one of the many "micro-amps" out there designed for use with headphones. Fender makes a nice one, but there are lots and they are tailored to a specific sound. I've listened to a Vox voiced one, and the Fender Mustang, both sounded quite good to my admittedly sound damaged ears.
You certainly can alter the circuit of your amp to accomplish your goal, but it is not trivial. You would have a lot of learning to do, a lot of experimenting, and it would take a fair amount of time. In addition, unless you invest in some serious gear to mimic your Champs output tube -- this is what the voiced micro amps actually do -- it can't sound like your Champ.
For me, not worth the time and effort for the stated goal.
IF you are more interested in learning, spending time and bucks working on amps, and that is the goal, then definitely proceed.
It's worth it to me. Building the entire amp took a few hours, even with the strange directions from StewMac, and an even weirder video with a ton of out of sequence instructions.
I was just hoping that I could find a good circuit for this headphone adaptation sooner than I have. I admit that I don't know much about amp building, and it's just this kind of modification that will help me learn more about how they work.
I'm literally sitting here with wire, jacks, solder and a can-do attitude. I just need directions.
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Dear XYZ,
Without being unkind, the info presented by our friends (in their labs/mansheds/etc and NOT TV land :icon_biggrin:) is very valuable.
From acheld as outlined in your previous post, asking for directions, this is gold. From pdf, PRR and others, this is REAL life experience.
...and from Sluckey, the exact info you asked for, no beating round the bush :laugh:.
Please read and consider the following links (my thoughts on the matter):
https://www.musicradar.com/news/fender-releases-the-mustang-micro-a-headphones-guitar-amplifier-that-fits-inside-your-pocket (https://www.musicradar.com/news/fender-releases-the-mustang-micro-a-headphones-guitar-amplifier-that-fits-inside-your-pocket)
http://www.generalguitargadgets.com/how-to-build-it/technical-help/articles/practice-amp-designs/ (http://www.generalguitargadgets.com/how-to-build-it/technical-help/articles/practice-amp-designs/)
Yes, solid state BUT handy and you will learn something, especially if you go down the DIY. On the hand a neat little pocket sized travel amp is very valuable and don't forget limitations of using HIFI heaphones for electric guitar monitoring.
Your Champ will do a great job when you use it for the purpose it was built.
Kind regards
Mirek
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Dear XYZ,
Without being unkind, the info presented by our friends (in their labs/mansheds/etc and NOT TV land :icon_biggrin:) is very valuable.
From acheld as outlined in your previous post, asking for directions, this is gold. From pdf, PRR and others, this is REAL life experience.
...and from Sluckey, the exact info you asked for, no beating round the bush :laugh:.
Please read and consider the following links (my thoughts on the matter):
https://www.musicradar.com/news/fender-releases-the-mustang-micro-a-headphones-guitar-amplifier-that-fits-inside-your-pocket (https://www.musicradar.com/news/fender-releases-the-mustang-micro-a-headphones-guitar-amplifier-that-fits-inside-your-pocket)
http://www.generalguitargadgets.com/how-to-build-it/technical-help/articles/practice-amp-designs/ (http://www.generalguitargadgets.com/how-to-build-it/technical-help/articles/practice-amp-designs/)
Yes, solid state BUT handy and you will learn something, especially if you go down the DIY. On the hand a neat little pocket sized travel amp is very valuable and don't forget limitations of using HIFI heaphones for electric guitar monitoring.
Your Champ will do a great job when you use it for the purpose it was built.
Kind regards
Mirek
So... no.
Since my last post I did the mod. In the end I used Rob Robinette's circuit but I put the headphone jack in place of input #2, like I mentioned earlier. My only gripes are the hum and that the volume is too high, but I think they are both solvable. I would like advice on how to deal with that if you're down.
Sluckey was helpful, sort of. It's the thought that counts!
Either way, I can now practice in peace.
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Since my last post I did the mod. In the end I used Rob Robinette's circuit but I put the headphone jack in place of input #2, like I mentioned earlier. My only gripes are the hum....
Did the box you built from Sluckey's layout drawing hum?
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It hums because a headphone is a thousand times more sensitive than a speaker so the usual Champ hum is a thousand times more prominent.
Also we have given you every which way to go and confused you.
While I understand you are invested in this Champ, it really may be better to buy or build a micro-amp.
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Since my last post I did the mod. In the end I used Rob Robinette's circuit but I put the headphone jack in place of input #2, like I mentioned earlier. My only gripes are the hum....
Did the box you built from Sluckey's layout drawing hum?
Yes.
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For those interested, here is a photo of the work. I have disconnected channel 2, and replaced its mono jack with a shunted stereo jack. Same for the speaker output jack, which I had previously built using a 1/4" phone jack instead of RCA.
When a speaker is connected, the circuit is normal and the headphone circuit is disconnected. When a speaker is not connected, the headphone circuit is active and the 8 Ohm 25W resistor is between the tip and sleeve, like Rob Robinette's circuit.
What would happen if I connected the resistor inline with the headphone signal instead? Would that affect the volume? Or something bad?
(https://i.imgur.com/UgAdrQe.jpg)
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What would happen if I connected the resistor inline with the headphone signal instead? Would that affect the volume? Or something bad?
You should leave the 8Ω/25W resistor as is (like Rob's schematic). But you do need a series resistor (between the speaker jack and the headphone jack) to drop the volume and also protect those headphones. I see the Sony MDR7506 is 63Ω impedance and since you probably have the headphone jack jumpered for sound in each ear, the total impedance would be 31.5Ω. I would start with a 100Ω series resistor and experiment to find the value that drops the volume to a pleasing level. May have to increase or decrease the 100Ω.
A Champ amp is inherently hummy due to the cheap design. It was a student practice amp and the cheap 8" speaker did not reproduce the low frequency hum very well, so no need to spend money to improve. Fender wanted you to buy a bigger, hum free amp. There's an easy way to upgrade a Champ to lower the hum. Just add another filter cap and a choke. Cost should be under $25.
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Last post by PRR is TOTALLY CORRECT. All of us were trying to guide you to get the best Headphone monitoring (and possibly most convenient) for your guitar and there is a lot of real life experience.
I personally have decades of experience with high end studios and engineering for Broadcast, so let me assure you that clean audio in headphone monitoring can really have its challenges, especially across multiple platforms.
All that aside, if you can achieve a headphone feed with attenuator and possibly Volume control go for it. Experiment, see what you come up with and enjoy your Champ. Let us know how you go as this forum is all about encouraging one another and leaning new things :laugh:
Kind regards
Mirek
Just noticed the post from Sluckey, this is what I meant by "achieving an attenuator"
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You should leave the 8Ω/25W resistor as is (like Rob's schematic). But you do need a series resistor (between the speaker jack and the headphone jack) to drop the volume and also protect those headphones. I see the Sony MDR7506 is 63Ω impedance and since you probably have the headphone jack jumpered for sound in each ear, the total impedance would be 31.5Ω. I would start with a 100Ω series resistor and experiment to find the value that drops the volume to a pleasing level. May have to increase or decrease the 100Ω.
A Champ amp is inherently hummy due to the cheap design. It was a student practice amp and the cheap 8" speaker did not reproduce the low frequency hum very well, so no need to spend money to improve. Fender wanted you to buy a bigger, hum free amp. There's an easy way to upgrade a Champ to lower the hum. Just add another filter cap and a choke. Cost should be under $25.
Thanks! I'll probably do all of those things, plus maybe use shielded wire to the headphone jack or maybe even the entire signal path. It was a kit, so it's not like I'd be ruining a vintage masterpiece. I might even change my mind someday and put it all back to stock and build a specialized headphone-only amp. For now, I OBVIOUSLY am not an expert and I appreciate all the advice you fellows have given - even if I don't always sound like it.
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IF you ever make the time;
you'll need a Marshall 4 X 12 cab
lots of space
Gibson guitar
your amp set on 10
start the guitar at 7
then play anything from 90's grunge to 70's hard rock, until your ears bleed
now go back and adjust for headphones :icon_biggrin:
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IF you ever make the time;
you'll need a Marshall 4 X 12 cab
lots of space
Gibson guitar
your amp set on 10
start the guitar at 7
then play anything from 90's grunge to 70's hard rock, until your ears bleed
now go back and adjust for headphones :icon_biggrin:
I have an LP Special DC and the Champ goes to 12! :m17
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I replaced the signal wire from the speaker output to the headphone output with a 10 watt 100 ohm resistor, and it's a more manageable volume and the hum has disappeared. It's almost perfect! I would be happy to leave it alone, except for that I'm not that kind of guy.
The only thing I would change is the volume range, but as it is now it gets too loud after about 3-1/2 on the dial - just like the speaker. Would it make sense to put another resistor before the speaker jack? If so, what value would make sense?
Or should I remove the resistor from the input jack, so that instead of a "high" input, a la input #1, it would be a "low" input, a la input #2?
Or something else?
(https://i.imgur.com/h7uS8IA.jpg)
Again, thanks for all the help on here!
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Try an L-Pad attenuator.
Don't need 10W resistors, 1 Watt will do.
10R in series with your 100R and put your headphones across the 10R resistor.
Note I said TRY :laugh:
You may have to experiment with the 10R value to suit your comfort level.
see for hints https://www.electronics-tutorials.ws/attenuators/l-pad-attenuator.html (https://www.electronics-tutorials.ws/attenuators/l-pad-attenuator.html)
Regards
Mirek
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I say again...
I would start with a 100Ω series resistor and experiment to find the value that drops the volume to a pleasing level. May have to increase or decrease the 100Ω.
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As sluckey said, even simpler.
Sorry Sluckey, missed your detail in Reply 50 "You should leave the 8Ω/25W resistor as is (like Rob's schematic)"
No need for L-Pad, save that idea for another project :laugh: But I repeat, save some money as you don't need a 10W resistor in this location.
Regards
Mirek
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I say again...
I would start with a 100Ω series resistor and experiment to find the value that drops the volume to a pleasing level. May have to increase or decrease the 100Ω.
And you were right! Let me rephrase my question:
With the new 100 Ohm resistor, the perceived volume I hear in the headphones matches the perceived volume coming out of the speaker at any given number on the dial, which was the goal. Does it make any sense to also reduce the signal before it gets to the speaker jack, so that I'm not using just the very bottom range of the dial in both the headphones and the speaker?
Frankly, I am happy as is, but I think it's weird that I'm only playing at 3 when the dial goes to 12. It's like only exploring the first ten feet of a cave. I want to get a flashlight and go deeper. Maybe there are some bear teeth I can dig up!
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If you want to set the volume knob to 12 and play through your headphones, you need to use a bigger series resistor. Or maybe you just need to use an L-Pad if you have room.
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If you want to set the volume knob to 12 and play through your headphones, you need to use a bigger series resistor. Or maybe you just need to use an L-Pad if you have room.
I bought two of the 10 watt 100 ohm resistors. Would it damage anything if I put it in series right after the output transformer?
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If you want to set the volume knob to 12 and play through your headphones, you need to use a bigger series resistor. Or maybe you just need to use an L-Pad if you have room.
I bought two of the 10 watt 100 ohm resistors. Would it damage anything if I put it in series right after the output transformer?
Probably not.
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you need your big resistor across the output transformer secondary as that is what is providing the proper load to your output stage
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It's been a couple of years since I've done this mod, and I added the L-pad shortly after the last pic was taken. It now looks like this:
(https://i.imgur.com/Gd9uwjC.jpg)
(https://i.imgur.com/VbCfJ8I.jpg)
I have decided that the headphone idea was worth trying but I'm over it. The L-pad works exactly like I wanted it to, though :smiley: - however it's just flopping around the cabinet. I don't currently work in a machine shop (I used to! :d2:), so I can't fashion a bracket to mount it and I don't want to drill unnecessary holes for experiments. There really isn't any place on this chassis for it to casually live.
I think I have a couple of options:
1) Return the kit to stock and build or buy a separate attenuator box, or
2) Return the kit to ALMOST stock, but replace the second input jack with a switch that engages or disengages a simple attenuation circuit to drop the volume to bedroom levels at noon (6-1/2) on the dial.
I found this at https://www.emprizeamps.com/post_attenuators.html (https://www.emprizeamps.com/post_attenuators.html):
(https://www.emprizeamps.com/images/post_pi_basic.png)
I think this would easily fit into the tiny Champ chassis. Do you see any red flags? Have you tried something like this yourself? Bad idea? Good idea?
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I want to follow up with my last post, in case I have made my case unclear.
My goal is to lower the output, not any specific mod. If there is a better way to lower the output, whether it be by changing certain components or some other way, I would be happy to explore that too.
I am leaning toward returning the Champ to its stock configuration, and lowering the output some way other than making a pile of spaghetti inside this tiny chassis. I'd love to hear your suggestions.
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It's a bad idea to run the speaker output near the input circuit. In fact, those two power resistors are located in the worst possible place in that chassis.
Since you like the L-pad consider moving it. If that's a steel chassis just solder the back of the L-pad to the chassis (requires a big soldering iron/gun). Or, put a liberal blob of silicone rubber on the chassis and set the L-pad in that.
Or move the L-pad to the speaker cab. It's rare to see one mounted on the amp.