Is the HRM a lossy tone stack?

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norburybrook
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Is the HRM a lossy tone stack?

Post by norburybrook »

Just doing some tweaking with mu 50w HRM and was wondering what effect the HRM tonestack had on the OD. I presume like most if not all guitar tone stacks it's a lossy one, ie.e it only cuts frequencies. If so I would presume then it would cut the gain on the OD channel. Can the HRM be put on a switch so it can be taken in/out without popping?


Marcus
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martin manning
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Re: Is the HRM a lossy tone stack?

Post by martin manning »

You could lift it from ground, similar to the PAB. Replace the 100R at the bottom with a 1M (more or less, to taste), and then arrange a switch to parallel the 100R back in.
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ToneMerc
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Re: Is the HRM a lossy tone stack?

Post by ToneMerc »

norburybrook wrote: Sun Jul 02, 2017 10:09 am Just doing some tweaking with mu 50w HRM and was wondering what effect the HRM tonestack had on the OD. I presume like most if not all guitar tone stacks it's a lossy one, ie.e it only cuts frequencies. If so I would presume then it would cut the gain on the OD channel. Can the HRM be put on a switch so it can be taken in/out without popping?


Marcus
It loads down the path and that OD entrance has more loss as well. I believe this is one of the reasons why it appears that HAD was not fond of using the LNFB circuit on HRM's.

Here's, an HRM build that I did that has a TS lift type PAB. When you pull the mid control, it lifts the HRM TS. If I had known that I would have liked it so much I would have put it on a relay.

http://ampgarage.com/forum/download/fil ... &mode=view


TM
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norburybrook
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Re: Is the HRM a lossy tone stack?

Post by norburybrook »

martin manning wrote: Sun Jul 02, 2017 2:12 pm You could lift it from ground, similar to the PAB. Replace the 100R at the bottom with a 1M (more or less, to taste), and then arrange a switch to parallel the 100R back in.
Martin , I'm not 100% sure of what you mean by paralleling the 100r back in on a switch.

Are you saying that by lifting the 100r from ground that will bypass the HRM? so I replace the current 100R with a 1M (which goes to ground) and then wire a switch to flip between the 1M and 100R?


what would that look like?


Marcus
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martin manning
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Re: Is the HRM a lossy tone stack?

Post by martin manning »

I think you've got it, but it's like this:
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rogb
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Re: Is the HRM a lossy tone stack?

Post by rogb »

I just put a switch to lift the ground from the 20K Mid trimmer on mine, it worked fine ISTR.
I had the HRM off for most of the time after that. I found the extra EQ was too focussed and less lively than without HRM.
Try it :)
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norburybrook
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Re: Is the HRM a lossy tone stack?

Post by norburybrook »

thanks guys.

I'm going to get the amp back out of its cab today and do some experimenting with this and different value cathode caps too.

all good stuff :D

obviously all this is guitar /speaker dependent so I can see how HAD could 'tune' a particular amp/speaker/guitar combination for someone.

Because of the small volume cabinet I'm making tonal decisions that perhaps wouldn't be relevant on a large 2x12 for example.

Marcus
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rogb
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Re: Is the HRM a lossy tone stack?

Post by rogb »

Don't forget to experiment with snubbers too. No snubbers, one or other sides of the dual triode etc
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ToneMerc
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Re: Is the HRM a lossy tone stack?

Post by ToneMerc »

norburybrook wrote: Mon Jul 03, 2017 9:59 am thanks guys.

I'm going to get the amp back out of its cab today and do some experimenting with this and different value cathode caps too.

all good stuff :D

obviously all this is guitar /speaker dependent so I can see how HAD could 'tune' a particular amp/speaker/guitar combination for someone.

Because of the small volume cabinet I'm making tonal decisions that perhaps wouldn't be relevant on a large 2x12 for example.

Marcus
Roll tubes and look at the V2 plates voltages, I have found that HRM's have a tighter window.

TM
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norburybrook
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Re: Is the HRM a lossy tone stack?

Post by norburybrook »

ToneMerc wrote: Mon Jul 03, 2017 3:19 pm
norburybrook wrote: Mon Jul 03, 2017 9:59 am thanks guys.

I'm going to get the amp back out of its cab today and do some experimenting with this and different value cathode caps too.

all good stuff :D

obviously all this is guitar /speaker dependent so I can see how HAD could 'tune' a particular amp/speaker/guitar combination for someone.

Because of the small volume cabinet I'm making tonal decisions that perhaps wouldn't be relevant on a large 2x12 for example.

Marcus
Roll tubes and look at the V2 plates voltages, I have found that HRM's have a tighter window.

TM
what's the window for V2? I'm seeing 181 and 184vDC I would say that's in the normal window for a regular ODS.

V1 is 189

Marcus
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ToneMerc
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Re: Is the HRM a lossy tone stack?

Post by ToneMerc »

norburybrook wrote: Tue Jul 04, 2017 10:53 am

what's the window for V2? I'm seeing 181 and 184vDC



Marcus
I personally like V2 10 volts higher, around 190-95 for an HRM. The trimmer settings and V2 voltage makes a big difference IMHO.

TM
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norburybrook
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Re: Is the HRM a lossy tone stack?

Post by norburybrook »

Can I achieve that with valve swapping or do I need to adjust the dropping string 22k resistor?

M
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ToneMerc
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Re: Is the HRM a lossy tone stack?

Post by ToneMerc »

norburybrook wrote: Tue Jul 04, 2017 1:04 pm Can I achieve that with valve swapping or do I need to adjust the dropping string 22k resistor?

M
Marcus, that is a very good question and I wish I could answer it in just one sentence. The most obvious least laborious method for is to just swap tubes, but then again what if you like the tube that's currently installed or what about down the road with further tube replacement. In the perfect world, every 12AX7 would be exactly the same which would impart some baseline consistency.

Try rolling a few tubes, while documenting the voltages and see if there's any tangible differences in what you hear.

TM
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norburybrook
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Re: Is the HRM a lossy tone stack?

Post by norburybrook »

ToneMerc wrote: Tue Jul 04, 2017 2:22 pm
norburybrook wrote: Tue Jul 04, 2017 1:04 pm Can I achieve that with valve swapping or do I need to adjust the dropping string 22k resistor?

M
Marcus, that is a very good question and I wish I could answer it in just one sentence. The most obvious least laborious method for is to just swap tubes, but then again what if you like the tube that's currently installed or what about down the road with further tube replacement. In the perfect world, every 12AX7 would be exactly the same which would impart some baseline consistency.

Try rolling a few tubes, while documenting the voltages and see if there's any tangible differences in what you hear.

TM
I had a feeling it wouldn't be so simple. It's what makes all of this so interesting :D Personally I haven't really heard much difference if any between a 12AX7 at 200v vs 185v so it's all a big experiment and in some cases stab in the dark as to why amp A sounds better than amp B made with the same parts :D

It's back in it's cab now so i'm leaving things as they are for now. It's an interesting amp for sure. Classic fender cleans, HRM overdrive, boost, then take out the HRM and it's a high gain fire breathing monster with the boost on :D

M
Mark
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Re: Is the HRM a lossy tone stack?

Post by Mark »

I found if the bass/mid controls are set to low this isn't good for tone. It takes a lot of time to set the TBM controls so they sound good with all guitars.
Yours Sincerely

Mark Abbott
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