... Thanks in advance for any advice.OT and PT Change for tone?
Moderators: pompeiisneaks, Colossal
OT and PT Change for tone?
I have a H&K Tubemeister 18 that i want to upgrade ie not so gainy and more clarity.... Just asking if a changing the ot and pt would help... The tubes have been changed to mesa tubes just wondering what i can do... Saving for a dumble clone 
... Thanks in advance for any advice.
... Thanks in advance for any advice.-
Stevem
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Re: OT and PT Change for tone?
If the graininess you want to get away from is there all the the time then that does not come from the Pt or the Ot, but, however a loss of clarity when the amp gets pushed hard may come from the Ot and if the graininess is only there when the amp is pushed hard then that likely comes from the circuit,
When an amp whose wattage output is pushing a under sized OT too hard then the first thing tone wise that changes is the lows get rolled off and the lows that are left sound blurred.
Is this what you are hearing?
Also a big mistake that a lot of players make is they leave the bass still turned up where it sounds fat and rich for clean playing and chord work when they are playing distorted leads, and there is not a amp on the planet that will sound good at those times!!!
Most times if you playing thru a amp with the bass up to 7 or 8 and smiling about the clean tones then that bass will need to get rolled back to no more then 4 when your pushing the amp hard.
This is why in my book even a 2 channel amp that has only 1 set of tone controls is a complete waste of money and its owner 95% of the time will never get the range of great tones there looking for because the amp needs two sets of tone controls, as in Bass and Treble and hopefully a mid control that can add a mid boost and not just a mid cut.
There’s another part of the circuit after the amps phase inverter that can a long these same lines make for a grainy sound when pushed hard, and the two parts that can cause this are cheap and most times easy to change out .
I don’t know if your amp has the value of these two parts that may help your tone to change them out to a smaller value without first seeing a schematic of the amp.
Also your 18 watt amp may just not have enough clean head room for you to play out live with if it has only one 12” speaker.
It’s been my findings that if your playing live with a 4 member or more band and your amp has only one 12” speaker then your going to need more like a 35 watt amp, and if you are playing thru 2-12” speakers ( which I consider minimum for live) then you can get away with a amp of some 25 watts.
By the way to my ear and secondly Wallet, Dumbles are very over rated!!
When an amp whose wattage output is pushing a under sized OT too hard then the first thing tone wise that changes is the lows get rolled off and the lows that are left sound blurred.
Is this what you are hearing?
Also a big mistake that a lot of players make is they leave the bass still turned up where it sounds fat and rich for clean playing and chord work when they are playing distorted leads, and there is not a amp on the planet that will sound good at those times!!!
Most times if you playing thru a amp with the bass up to 7 or 8 and smiling about the clean tones then that bass will need to get rolled back to no more then 4 when your pushing the amp hard.
This is why in my book even a 2 channel amp that has only 1 set of tone controls is a complete waste of money and its owner 95% of the time will never get the range of great tones there looking for because the amp needs two sets of tone controls, as in Bass and Treble and hopefully a mid control that can add a mid boost and not just a mid cut.
There’s another part of the circuit after the amps phase inverter that can a long these same lines make for a grainy sound when pushed hard, and the two parts that can cause this are cheap and most times easy to change out .
I don’t know if your amp has the value of these two parts that may help your tone to change them out to a smaller value without first seeing a schematic of the amp.
Also your 18 watt amp may just not have enough clean head room for you to play out live with if it has only one 12” speaker.
It’s been my findings that if your playing live with a 4 member or more band and your amp has only one 12” speaker then your going to need more like a 35 watt amp, and if you are playing thru 2-12” speakers ( which I consider minimum for live) then you can get away with a amp of some 25 watts.
By the way to my ear and secondly Wallet, Dumbles are very over rated!!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: OT and PT Change for tone?
That seems very unlikely.
Got a schematic?
Tried swapping a 12AY7 into one then the other 12AX7 socket? Or a 5751?
Even without that, the clean channel looks to have overdrive capability, with a gain, master and output attenuator controls; have you tried all permutations of control settings? Or a dumble type pedal?
With respect to guitar sound quality, what do you mean by 'graininess'? Are there any examples of a grainy guitar sound?
All I can relate it to is a grainy TV picture, which means that it has a poor picture quality with low resolution and lots of fuzz, and is caused by a poor signal level ie low signal to noise ratio.
That would translate into audio terms as a guitar sound with lots of hiss.
Dunno, I just wish people would use accepted, defined terminology; how can technical discussion be feasible otherwise?
Are there any examples of such a mid control, that don't require an inductor or gyrator?a mid control that can add a mid boost and not just a mid cut
https://www.justgiving.com/page/5-in-5-for-charlie This is my step son and his family. He is running 5 marathons in 5 days to support the research into STXBP1, the genetic condition my grandson Charlie has. Please consider supporting him!
Re: OT and PT Change for tone?
I believe it is Stevem who wrote "graininess." Looking at the OP, it says, "gaininess" without the r. I think the OP asked about more gain. FWIW, I think you answered well and then recommended a pedal. I don't have much pedal experience, but it seems to me that would be a much more effective and cost effective direction. I can't see spending money on transformers. I'm doubtful that will address the OP's goal.
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CraigGa
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Re: OT and PT Change for tone?
I had a TM36 and could never get a good drive sound out of it.
I replaced V1 with a 5751 and it improved matters but not enough to stop me selling it.
I replaced V1 with a 5751 and it improved matters but not enough to stop me selling it.
Thinking about my second build.
Re: OT and PT Change for tone?
Yes, I asked the question after the quote from Stevem's post, so I hoped it was apparent it was directed it to him, rather than at Alshaheen
https://www.justgiving.com/page/5-in-5-for-charlie This is my step son and his family. He is running 5 marathons in 5 days to support the research into STXBP1, the genetic condition my grandson Charlie has. Please consider supporting him!
Re: OT and PT Change for tone?
Thanks for the replys maybe a good dumble pedal may be the answer.... I just think that on clean it gets into overdrive to early and thats why i said too gainy... Sorry for terminology failure 
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Stevem
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Re: OT and PT Change for tone?
Well in that case it would be very worth while to order up a set of Groovetubes for the amp in a number 10 rating even if you have to wait out a order back log before you toss in the towel and put the amp up for sale!
Does anyone know if the output stage in this H&K amp is Cathode biased?
Does anyone know if the output stage in this H&K amp is Cathode biased?
Last edited by Stevem on Mon Apr 12, 2021 10:30 am, edited 1 time in total.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
-
Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: OT and PT Change for tone?
Well in that case it would be very worth while to order up a set of Groovetubes for the amp in a number 10 rating even if you have to wait out a order back log before you toss in the towel and put the amp up for sale!
Does anyone know if the output stage in this amp is Cathode biased?
Does anyone know if the output stage in this amp is Cathode biased?
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: OT and PT Change for tone?
They appear to be fixed bias but they have mosfets in the EL84 cathodes.
They have a weird mechanism wherby you stick a plectrum in a hole and it tells you what bias the they're running.
The input stage is actually an op-amp, reducing the 10K feedback resistor should reduce the overall gain.
Thinking about my second build.
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pompeiisneaks
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Re: OT and PT Change for tone?
Yeah he's right, here's the schematic:
https://music-electronics-forum.com/fil ... ?id=836613
it seems like they have some mosfets at the cathode that can turn on/off the path to the 1.5 ohm resistors with some test points. They seem to have some hardware dedicated to measuring that for you, and maybe setting it, but didn't dig too deeply. Definitely fixed bias not cathode.
~Phil
https://music-electronics-forum.com/fil ... ?id=836613
it seems like they have some mosfets at the cathode that can turn on/off the path to the 1.5 ohm resistors with some test points. They seem to have some hardware dedicated to measuring that for you, and maybe setting it, but didn't dig too deeply. Definitely fixed bias not cathode.
~Phil
tUber Nerd!
Re: OT and PT Change for tone?
I think the mosfets are used for standby and on the TM36 they can turn off two tubes to reduce the power to half.
The whole thing is controlled by a microcontroller.
The whole thing is controlled by a microcontroller.
Thinking about my second build.
Re: OT and PT Change for tone?
Keep it coming.... You lads really llt know what your talking about i take my hat off to you thanks for all your input
Re: OT and PT Change for tone?
Hats off to HK, the use of a microcontroller and mosfet controllers seems like a big step towards RG Keen’s vision for ‘the proper way to do things’. ie by monitoring and comparing idle cathode current to ensure an appropriate bias voltage, keeping the valves operating in their sweet spot to extend their useful life. But then, with the use of current limiters for the screen and anode supplies, protecting the amp from risk of being damaged by their catastrophic failure when they’ve given all they’ve got. Just look which led is showing the bad valve, replace it, and carry on. No replacing fuses, blown resistors or transformers ever again.
It looks like the control system is just doing the bias so far, but perhaps the next generation will include current monitoring and limiting for the HT supplies too?
The use of valves whose characteristics are too far from their type nominal, eg GT grade 1 or 10 (if they’re available anymore), may confuse the controller, by being out of the range of the expected bias voltage. Resulting in them being rejected as faulty.
It looks like the control system is just doing the bias so far, but perhaps the next generation will include current monitoring and limiting for the HT supplies too?
The use of valves whose characteristics are too far from their type nominal, eg GT grade 1 or 10 (if they’re available anymore), may confuse the controller, by being out of the range of the expected bias voltage. Resulting in them being rejected as faulty.
https://www.justgiving.com/page/5-in-5-for-charlie This is my step son and his family. He is running 5 marathons in 5 days to support the research into STXBP1, the genetic condition my grandson Charlie has. Please consider supporting him!