blaise.brown.7967
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Does anyone know the range here(50-90)? I'm thinking 50 is too cold. Am I correct? 70-80 is where I think it should be.
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Biasing level for a MARSHALL DSL100H
- Thread starter blaise.brown.7967
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blaise.brown.7967
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Re: Biasing level for a MARSHALL DSL100H
I'll be using Tung Sol el34bs.
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I'll be using Tung Sol el34bs.
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blaise.brown.7967
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Re: Biasing level for a MARSHALL DSL100H
I need some feedback.Please!!
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I need some feedback.Please!!
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blaise.brown.7967
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Re: Biasing level for a MARSHALL DSL100H
I no longer need anyone to answer my question. The bias is set at 62mv.per side.
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I no longer need anyone to answer my question. The bias is set at 62mv.per side.
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blaise.brown.7967
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Re: Biasing level for a MARSHALL DSL100H
And thanks loads for nothing!!
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And thanks loads for nothing!!
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Fast.Eddie70
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Re: Biasing level for a MARSHALL DSL100H
I know this is an older thread but I wanted to share the data that I have, I find that 82 to 85 MV per side for the DSL100H is best in my opinion, this is a service bulletin that states 90MV for the DSL100H. Please see below for instructions and info,
How to bias a JCM2000 / DSL series amp.
Here's the Marshall Service Bulletin on biasing the JCM2000 series amps:
Procedure:
1. Make sure the amp is connected to a load with the proper impedance selected.
2. Power up amp on Standby, and let the circuit stabilize for a couple of minutes.
3. Locate the male three pin molex connector (CON2) with the two mini pots (PR1 and PR2) (located on each side of the molex connector) on both ends found at the bottom of tube bay.
4. Connect DMM (set to read mV) with alligator leads, reference common lead to center pin (pin2) on molex connector CON2 and positive lead to pin1 on CON2.
5. Take amp off Standby with no signal, adjust mini-pot (PR1) closest to pin that the positive lead from your DMM is connected to and set it to mV voltage that is listed below.
6. Repeat steps 4 & 5 for pin3 mV and until pin1 & pin3 mV readings are the same.
Bias Settings:
DSL50 45 mV
TSL 601&602 80 mV
DSL100 90 mV
DSL 401 1.375V
TSL100/122 90mV
DSL201 .675V
DSL201 0.675 V
DSL401 1.375 V
DSL50 45 mV
DSL100 90 mV
TSL60 80 mV
TSL100/122 90 mV
Here's a quick bias lesson:
What you want to do is measure the plate voltage (B+) from pin3 of one of the power tubes. It should measure between 450-500V. Now the max plate dissapation (Pa Max) for EL34s is about 25W. To calculate the correct bias, you want to:
(Pa Max/B+)(.7) = 38-45mA depending on the exact plate voltage of your amp. Check and adjust via the molex connector and pots from above.
Link: http://www.unclespot.com/JCM2000BIASing.html
I know this is an older thread but I wanted to share the data that I have, I find that 82 to 85 MV per side for the DSL100H is best in my opinion, this is a service bulletin that states 90MV for the DSL100H. Please see below for instructions and info,
How to bias a JCM2000 / DSL series amp.
Here's the Marshall Service Bulletin on biasing the JCM2000 series amps:
Procedure:
1. Make sure the amp is connected to a load with the proper impedance selected.
2. Power up amp on Standby, and let the circuit stabilize for a couple of minutes.
3. Locate the male three pin molex connector (CON2) with the two mini pots (PR1 and PR2) (located on each side of the molex connector) on both ends found at the bottom of tube bay.
4. Connect DMM (set to read mV) with alligator leads, reference common lead to center pin (pin2) on molex connector CON2 and positive lead to pin1 on CON2.
5. Take amp off Standby with no signal, adjust mini-pot (PR1) closest to pin that the positive lead from your DMM is connected to and set it to mV voltage that is listed below.
6. Repeat steps 4 & 5 for pin3 mV and until pin1 & pin3 mV readings are the same.
Bias Settings:
DSL50 45 mV
TSL 601&602 80 mV
DSL100 90 mV
DSL 401 1.375V
TSL100/122 90mV
DSL201 .675V
DSL201 0.675 V
DSL401 1.375 V
DSL50 45 mV
DSL100 90 mV
TSL60 80 mV
TSL100/122 90 mV
Here's a quick bias lesson:
What you want to do is measure the plate voltage (B+) from pin3 of one of the power tubes. It should measure between 450-500V. Now the max plate dissapation (Pa Max) for EL34s is about 25W. To calculate the correct bias, you want to:
(Pa Max/B+)(.7) = 38-45mA depending on the exact plate voltage of your amp. Check and adjust via the molex connector and pots from above.
Link: http://www.unclespot.com/JCM2000BIASing.html
Last edited:
Lake Placid Blues
New member
Re: Biasing level for a MARSHALL DSL100H
For 50 watters it's one tube per side and for 100 watters it two tubes per side. Such is the case for DSL 50s (40s) and DSL100s. Each tube is biased at 45ma in both cases. which is fairly hot for EL34s depending on the plate voltage. But some of these has figures have me scratching my head. The TSL60 at 80mv? This must be for both tubes each from one side. That could be 40ma per tube which makes sense.
In most cases there is a 1 ohm resistor between the cathode(s) and ground. The voltage measurement is across the resistor. This way mv = ma. If there is no 1 ohm resistor the a voltage measurement could be a very different number to yield the correct range of current measured in miliamps.
For 50 watters it's one tube per side and for 100 watters it two tubes per side. Such is the case for DSL 50s (40s) and DSL100s. Each tube is biased at 45ma in both cases. which is fairly hot for EL34s depending on the plate voltage. But some of these has figures have me scratching my head. The TSL60 at 80mv? This must be for both tubes each from one side. That could be 40ma per tube which makes sense.
In most cases there is a 1 ohm resistor between the cathode(s) and ground. The voltage measurement is across the resistor. This way mv = ma. If there is no 1 ohm resistor the a voltage measurement could be a very different number to yield the correct range of current measured in miliamps.
JeffB
Let it B
Re: Biasing level for a MARSHALL DSL100H
Generally the 40c plate voltage is around 450mv and most folks online that I have seen discuss it are biasing in the 35-38 range each side. I biased mine at 38 last time but may drop it a touch to see how it sounds.
Great tool here..
http://www.tedweber.com/webervst/tubes1/calcbias.htm
Generally the 40c plate voltage is around 450mv and most folks online that I have seen discuss it are biasing in the 35-38 range each side. I biased mine at 38 last time but may drop it a touch to see how it sounds.
Great tool here..
http://www.tedweber.com/webervst/tubes1/calcbias.htm
Last edited:
dystrust
New member
Re: Biasing level for a MARSHALL DSL100H
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I'm not sure if it'll react the same, but my Jube gets brittle bright if biased too cold. I'm honestly shocked that it sounds pretty good @ 33ma; I typically don't like it colder than 35.
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JeffB
Let it B
Re: Biasing level for a MARSHALL DSL100H
I guess I will find out
I only have hands on experience biasing this one amp, but I am amazed (and not terribly thrilled about) how little of a window there is before the amp sounds like absolute @$$. And the amount/frequency of bias drift (again, don't know if other tube amps are as finnicky- I used to have a tech do it, BITD).
I guess I will find out
I only have hands on experience biasing this one amp, but I am amazed (and not terribly thrilled about) how little of a window there is before the amp sounds like absolute @$$. And the amount/frequency of bias drift (again, don't know if other tube amps are as finnicky- I used to have a tech do it, BITD).
dystrust
New member
Re: Biasing level for a MARSHALL DSL100H
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The range I like is typically pretty narrow. Below about 35 gets really bright, while higher than 38 is too bassy / fat.I guess I will find out
I only have hands on experience biasing this one amp, but I am amazed (and not terribly thrilled about) how little of a window there is before the amp sounds like absolute @$$. And the amount/frequency of bias drift (again, don't know if other tube amps are as finnicky- I used to have a tech do it, BITD).
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ken361
New member
Re: Biasing level for a MARSHALL DSL100H
Just got my 40c back from my tech, he's one of the best and highly recommend in south east MI. says the dsl and some high gain amps should be set low because the preamp is were the distortion coming from. True we know that power tubes break up enough so it wont cause cross over distortion at 30! I was keeping the bias set around 35ma. I did put a new WSG ET 65 speaker in the day I got it back.
The notes are clearer sounding then the british lead speaker, I noticed the neck pickup on the strat now is more smoother and clearer now with low bias!!Hendrix,Trower tones! bending notes and even when boosted is a lot better it holds the note better then before. The crunch is less bassy with nicer crunch and cleans.Lower bias did not effect the breakup at all some think higher is better I dont think so now. It breaths and performs better now. Power tubes wouldnt last very long on my amp 8 months on the stock was best. I know people are going to say you cant run a cold bias blau blau blau what ever I trust dean over these guys on the internet lol. He said if you listen to people on the net your just going to keep guys like me in business! He ran a scope on my amp so you can see whats going on with the distortion
Just got my 40c back from my tech, he's one of the best and highly recommend in south east MI. says the dsl and some high gain amps should be set low because the preamp is were the distortion coming from. True we know that
power tubes break up enough so it wont cause cross over distortion at 30! I was keeping the bias set around 35ma. I did put a new WSG ET 65 speaker in the day I got it back.The notes are clearer sounding then the british lead speaker, I noticed the neck pickup on the strat now is more smoother and clearer now with low bias!!Hendrix,Trower tones! bending notes and even when boosted is a lot better it holds the note better then before. The crunch is less bassy with nicer crunch and cleans.Lower bias did not effect the breakup at all some think higher is better I dont think so now. It breaths and performs better now. Power tubes wouldnt last very long on my amp 8 months on the stock was best. I know people are going to say you cant run a cold bias blau blau blau what ever I trust dean over these guys on the internet lol. He said if you listen to people on the net your just going to keep guys like me in business! He ran a scope on my amp so you can see whats going on with the distortion
JeffB
Let it B
Re: Biasing level for a MARSHALL DSL100H
Well, I finally got around to re-biasing mine. The drift is crazy. I had measured it a couple weeks back at 42/45 (set at 38 several months back). Today is was 42 and 48. Nuts.
I decided to bias back to 37.5 to , see what happens since that is where I had it before and.got used to the.tone. With the idea of experimenting a bit more, I left the chassis out of the cab. Of course the amp sounds a whole lot better now, and preamp tube changes are far more noticable. I will check it again in a few days.. But I do think it could go a bit colder and clear up a tad bit more.
Well, I finally got around to re-biasing mine. The drift is crazy. I had measured it a couple weeks back at 42/45 (set at 38 several months back). Today is was 42 and 48. Nuts.
I decided to bias back to 37.5 to , see what happens since that is where I had it before and.got used to the.tone. With the idea of experimenting a bit more, I left the chassis out of the cab. Of course the amp sounds a whole lot better now, and preamp tube changes are far more noticable. I will check it again in a few days.. But I do think it could go a bit colder and clear up a tad bit more.
Lake Placid Blues
New member
Re: Biasing level for a MARSHALL DSL100H
The plate voltage will determine what ma is within range for a given tube type. The calculation is plate dissipation in watts/plate voltage= max current flow. Then it would be times the %. For example, if the plate voltage is 450 and the tubes are EL34, then max current flow will be 55ma. 70% would be 39ma. But the % is just a ball park figure. You may like it a little hotter or colder than that.
I checked a used DSL15, and it runs 6V6 tubes at ~425 volts. When I got it, it was biased at 33ma for one side and 29ma for the other. Max current flow for 6V6s is 14/425 = 33ma. So one tube was running 100%! The amp sounded boomy. Although the bass was boomy the treble was also piercing. The bias was reset to 21ma and the amp sounded much more well balanced and musical.
The plate voltage will determine what ma is within range for a given tube type. The calculation is plate dissipation in watts/plate voltage= max current flow. Then it would be times the %. For example, if the plate voltage is 450 and the tubes are EL34, then max current flow will be 55ma. 70% would be 39ma. But the % is just a ball park figure. You may like it a little hotter or colder than that.
I checked a used DSL15, and it runs 6V6 tubes at ~425 volts. When I got it, it was biased at 33ma for one side and 29ma for the other. Max current flow for 6V6s is 14/425 = 33ma. So one tube was running 100%! The amp sounded boomy. Although the bass was boomy the treble was also piercing. The bias was reset to 21ma and the amp sounded much more well balanced and musical.
Lake Placid Blues
New member
Re: Biasing level for a MARSHALL DSL100H
Didn't you change to KT-77? Remember the KT-77 is rated at max plate dissipation of 30 watts, instead of 25 watts.
Didn't you change to KT-77? Remember the KT-77 is rated at max plate dissipation of 30 watts, instead of 25 watts.
