HRM tweaking and the octave below

[heisthl]

I've been doing some Major tweaking on the SuperReverb Conversion I did a few weeks ago. This amp is 50 watt bassman PT and OT w/2 6L6 output. I had been playing with alternate PI styles, plate voltages and internal tone trimmer settings. Right now I'm running the normal PI with .1 coupling caps, the old style dropping values and no FET compensation resistor. V1 plates are 198,209 and V2 plates are around 200,211 both are using the 220/3k3 150/2k2 values. PI plates at 289 and 287 with 56.6 on the cathodes. This amp is doing the most amazing thing in OD mode(esp.w/boost and mid boost on too) - It plays an octave below when ever you play 2 notes on adjacent strings. It is the fattest most amazing thing I've ever heard. When you play single notes it has plenty of character, sustain and overtones but as soon as you play 2 notes you get the octave below at the correct proportional volume and equally up and down the neck on every note(s) think EW Frankenstien tone. Is this normal for a properly tweaked HRM? Me likey

[ayan]

I've been doing some Major tweaking on the SuperReverb Conversion I did a few weeks ago. This amp is 50 watt bassman PT and OT w/2 6L6 output. I had been playing with alternate PI styles, plate voltages and internal tone trimmer settings. Right now I'm running the normal PI with .1 coupling caps, the old style dropping values and no FET compensation resistor. V1 plates are 198,209 and V2 plates are around 200,211 both are using the 220/3k3 150/2k2 values. PI plates at 289 and 287 with 56.6 on the cathodes. This amp is doing the most amazing thing in OD mode(esp.w/boost and mid boost on too) - It plays an octave below when ever you play 2 notes on adjacent strings. It is the fattest most amazing thing I've ever heard. When you play single notes it has plenty of character, sustain and overtones but as soon as you play 2 notes you get the octave below at the correct proportional volume and equally up and down the neck on every note(s) think EW Frankenstien tone. Is this normal for a properly tweaked HRM? Me likey

I've never heard of anything like that happening before, so I will follow the thread closely to see if I can learn somethng new!

Gil

[heisthl]

In spite of my poor playing abilities I'll try to post a clip this weekend. I may do it on video because when you hear this you'll swear I'm using a harmonizer or MXR "blue box". Needless to say I'm not doing any more tweaks in this amp.

[bluefireamps]

Sounds like intermodulation distortion. If you play the two notes and bend one up while the other is at its' original pitch, does that octave change as you bend? Intermodulation distortion is present in pretty much all overdriven amps and pedals to varying degrees. It's "normal" as far as that goes. It can drive me crazy sometimes depending on how bad it is and what I'm playing.
Dave

[heisthl]

It's definitly a varaiation of the normal " ghost pitch goes downward as bend goes upward" but I've never had it manifest itself in such a musical way when playing 4ths and 5ths on adjacent strings without bending. One of the first things I noticed when I started making non-HRM clones was their almost complete lack of the undesirable ghosting during the typical blues bends (bending the G string while holding a 4th above on the B string). This particular amp is the first(and only) HRM I've done so far and I'm wondering if this tendency for ghost notes is part of the charm of the HRM style lead tone.

[heisthl]

I think any good HRM will do this - You have to run the amp "full range" and get the presence completely out of the output circuit. I have a switch on the presence pot that takes the presence leg out of the circuit at 0. I was so enamored with the sonic novelty it took me a while to catch this.
Would be another nice thing to have on your footswitch because after playing with it awhile you learn what to play and not play and can actually get some nice counterpoint going with ghost notes as well as the octave effects. With the presence connected the ghosting is almost completely gone (less than a typical old Fender).

[tonelab2]

I always thought that was a sign of not enough filtering or filter section not keeping up with supply demands.

[ayan]

I think any good HRM will do this - You have to run the amp "full range" and get the presence completely out of the output circuit. I have a switch on the presence pot that takes the presence leg out of the circuit at 0. I was so enamored with the sonic novelty it took me a while to catch this.
Would be another nice thing to have on your footswitch because after playing with it awhile you learn what to play and not play and can actually get some nice counterpoint going with ghost notes as well as the octave effects. With the presence connected the ghosting is almost completely gone (less than a typical old Fender).

OK, with this and the previous posts, I understand what you're referring to. I have never run my amps open loop, so perhaps that's why I've never had that happen to me. Interesting that in your case the sound is musical, because now that I know what you're talking about, my past experiences with that issue were actually very annoying (especially with pedals).

I do love the fact that with my amps I can play double stops with bends without the intermodulation getting too much in the way. The amps behave like they were being played clean in that respect, with makes the string to string separation great. I attribute that to the fact that there are few stages in the ODS design.

Gil

['67_Plexi]

With PAB enabled and mid boost enabled, the mid boost will become a bass boost. Remember the PAB changes the R-C network. Capacitive Reactance.

Alan Phillips

[heisthl]

I played around with no presence on a non-HRM today with similiar but not as good results. I encourage anyone with a HRM to try this as it's a usable freebee efffect if you make it switchable. I have been putting the presence off switch on most of my builds but the purpose was for full range clean (like amplifying an acoustic) to extend the versatility of the amps. It was never intended for lead tones but it makes for a nice option.

[mdroberts1243]

I think any good HRM will do this - You have to run the amp "full range" and get the presence completely out of the output circuit. I have a switch on the presence pot that takes the presence leg out of the circuit at 0. I was so enamored with the sonic novelty it took me a while to catch this.
Would be another nice thing to have on your footswitch because after playing with it awhile you learn what to play and not play and can actually get some nice counterpoint going with ghost notes as well as the octave effects. With the presence connected the ghosting is almost completely gone (less than a typical old Fender).

I think my bluesmaster build does this in spades. It does it with the presence engaged. Is that perhaps because the NFB is less in the BM Power Stage?

One player that tried the amp out liked the effect but asked if it could be selective/optional... is there a way to dial this out?

[Structo]

Hmm, doesn't sound like something very desirable in an amp.
But I guess if you can control it it would be alright.
Sounds like something someone would post about saying, help my amp sounds like frankenstein!

[heisthl]

One player that tried the amp out liked the effect but asked if it could be selective/optional... is there a way to dial this out?

It is low freq so just increase the P cap and if that's not enough decrease the P Resistor.

[Bob-I]

The first thing I noticed when I read this post is that you're using .1uF couplers on the power tubes. The HRM typically uses .022uF.

I had an hybrid I converted to HRM and didn't change these caps. Scott pointed this out to me and after I changed them the amp was dramatically better. Still plenty of bottom but tighter and more dynamic.

As for your IM problem, I'll be watching, listening and learning. Please post clips, no one will judge your playing, it's prolly much better than you think anyway