HRM VS Non HRM

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stevek66
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HRM VS Non HRM

Post by stevek66 »

I built a 102 and 183 quite awhile ago.I prefered the 102 to the 183 so I decided to HRM the 183 about 6 months ago.The 183 has the dual master,skyliner eq and pi.
I always thought that both amps were rather tame volume wise for 100 watters.However since I coverted the 183 to an HRM circiut the OD channel
is paint peeling loud.Both amps are similar volume wise on the clean channel.
So I have been trying to figure out why.Is it the lack of a level control in a HRM circuit when changing from a global master to a dual master?I have been researching how to add a level control on the hrm board to compensate so to speak.However is this common between the non HRM and HRM circuits?
Or is it my 102?I have checked every connection,value,voltage ect in the OD circuit and all seems to check out.Again both amps originally where very close volume wise.Its made me scratch my head for sure.
Thanks in advance for any input.
Steve
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briane
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Re: HRM VS Non HRM

Post by briane »

nope - not common - Id say somethings wrong with the non-HRM

possibly the trimpot input to v2 is down too low?

these amps work better with dual masters
it really is a journey, and you just cant farm out the battle wounds
groovtubin
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Re: HRM VS Non HRM

Post by groovtubin »

stevek66 wrote:I built a 102 and 183 quite awhile ago.I prefered the 102 to the 183 so I decided to HRM the 183 about 6 months ago.The 183 has the dual master,skyliner eq and pi.
I always thought that both amps were rather tame volume wise for 100 watters.However since I coverted the 183 to an HRM circiut the OD channel
is paint peeling loud.Both amps are similar volume wise on the clean channel.
So I have been trying to figure out why.Is it the lack of a level control in a HRM circuit when changing from a global master to a dual master?I have been researching how to add a level control on the hrm board to compensate so to speak.However is this common between the non HRM and HRM circuits?
Or is it my 102?I have checked every connection,value,voltage ect in the OD circuit and all seems to check out.Again both amps originally where very close volume wise.Its made me scratch my head for sure.
Thanks in advance for any input.
Steve
My HRM will make your EARS BLEED at (1.5 -2 ) on OD volume....it`s in TOTAL control with the Dator....if you look at the early literature of a Dumble ( 70`s) he flat WARNS that the amps will get loud and can cause hearing loss,,

respectfully,

jim@Omegaamps
stevek66
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Re: HRM VS Non HRM

Post by stevek66 »

Briane,thanks for the reply.I have adjusted the trimmer on the od entrance to the amount of gain I like but will look at it again.I have both amps set about the same in that respect.
Thanks again
Steve
stevek66
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Re: HRM VS Non HRM

Post by stevek66 »

Jim,My HRM is exactly as you describe yours.Blistering loud at 2.
I am ok with that,I'm just trying to understand the why compared to the
102 version.Again before I HRM'd the 183 it was about the same as my 102 in overall volume in OD.I also think both amps sound great.
Thanks
Steve
groovtubin
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Re: HRM VS Non HRM

Post by groovtubin »

stevek66 wrote:Jim,My HRM is exactly as you describe yours.Blistering loud at 2.
I am ok with that,I'm just trying to understand the why compared to the
102 version.Again before I HRM'd the 183 it was about the same as my 102 in overall volume in OD.I also think both amps sound great.
Thanks
Steve
Steve i`d say its in the secret sauce heh? :lol:
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Structo
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Re: HRM VS Non HRM

Post by Structo »

When I built my ODS amp I couldn't figure out why it was so loud when the preamp volume was set low.

As I investigated, I found out the NOS Allen Bradley pot I had installed was defective.
The sweep was screwed up and jumped in volume very early in the rotation.
Once I replaced it the amp works a lot better.

From that point on I made a effort to test and measure all components before installation.
Tom

Don't let that smoke out!
groovtubin
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Re: HRM VS Non HRM

Post by groovtubin »

stevek66 wrote:Jim,My HRM is exactly as you describe yours.Blistering loud at 2.
I am ok with that,I'm just trying to understand the why compared to the
102 version.Again before I HRM'd the 183 it was about the same as my 102 in overall volume in OD.I also think both amps sound great.
Thanks
Steve
so are the pots bad?

jp
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briane
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Re: HRM VS Non HRM

Post by briane »

Once I replaced it the amp works a lot better.
haha - I once had a HRM that was way too loud - turned out the master (dual master) pot was toast - had 3 settings when I measured it - on, more - and everything!

My HRM volume is about same as non-HRM - I can tell cause I have a switch to go between non and hrm.

HRM is just a whole lot more crunchy mainly - more OD.

If you think about it - HRM should be quieter- cause of all the loss and signal drop from an additional EQ controls - those things always dump volume.

But most turn the amp up to compensate - usually with a bigger signal on the internal trim to v1b.
it really is a journey, and you just cant farm out the battle wounds
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ToneMerc
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Re: HRM VS Non HRM

Post by ToneMerc »

briane wrote:
If you think about it - HRM should be quieter- cause of all the loss and signal drop from an additional EQ controls - those things always dump volume.
.
HRM OD entrance network robs gain as well.

TM
stevek66
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Re: HRM VS Non HRM

Post by stevek66 »

No the pot isn't bad.I could play out with it set at 2ish and just gets louder as you go up through the dial.At noon on the dial I believe it would be considered a lethal weapon,it's that loud.It isn't an issue of all the volume being full on instantly on the dial.This is what I'm trying to understand between the 2 amps.Both 100 watters,both skyliners,both with almost identical voltages on the power tubes and the differences be one has a twin ot and the other has a Plexi ot with HRM board.Again before I changed it to a
Hrm circuit they were close in volume.Crazy
Thanks
Steve
groovtubin
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Re: HRM VS Non HRM

Post by groovtubin »

stevek66 wrote:No the pot isn't bad.I could play out with it set at 2ish and just gets louder as you go up through the dial.At noon on the dial I believe it would be considered a lethal weapon,it's that loud.It isn't an issue of all the volume being full on instantly on the dial.This is what I'm trying to understand between the 2 amps.Both 100 watters,both skyliners,both with almost identical voltages on the power tubes and the differences be one has a twin ot and the other has a Plexi ot with HRM board.Again before I changed it to a
Hrm circuit they were close in volume.Crazy
Thanks
Steve
I`d put a one meg in series with the OD vol pot, maybe bypass with a PF cap.......that MIGHT get it a tad more easy on you! I`ve done that w/great success on other amps..

jim
Chris333
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Re: HRM VS Non HRM

Post by Chris333 »

Might be interesting to put a sine wave on the input and start measuring AC signal voltages at various points between the input jack and the output of the PI. If you do that to both amps, it should be possible to pinpoint where the extra volume in the HRM amp is coming from.
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