HRM on #183 OD--What Pot Values Work?

[David Root]

Thinking of trying this. I used T 250K, B 250K and M 20K/100R on my Bloozman (HRM Bluesmaster), worked very well. I understand you don't want too much mids in OD, especially if you have Mid Boost on a FSW.

Still wondering about that 20K though.

Also, why 100R to ground rather than 500R or 1K or so? Is it just to leave a minimum resistance so the gain doesn't completely disappear when the Mids pot is cranked right up? Higher R would start interfering with the 20K pot function?

[Fischerman]

Thinking of trying this. I used T 250K, B 250K and M 20K/100R on my Bloozman (HRM Bluesmaster), worked very well. I understand you don't want too much mids in OD, especially if you have Mid Boost on a FSW.

Still wondering about that 20K though.

Also, why 100R to ground rather than 500R or 1K or so? Is it just to leave a minimum resistance so the gain doesn't completely disappear when the Mids pot is cranked right up? Higher R would start interfering with the 20K pot function?

Do you mean; "turned all the way down"? Turning up the mid pot should increase gain a little. I see what you mean though, seems that 100R is small enough to be negligible (ha, NOTHING is negligible ).

The HRM schematic I have shows a 20k HRM mid-pot, is that not correct? My schemo also shows a 1M bass pot. I have the HRM controls mounted on the front panel of mine and used a 500k HRM bass pot. I don't like the typical ON/OFF behavior you can get with 1M (usually somewhere between 2 and 4) and since I never crank the bass I figured I didn't need the full 1M. Do you have the run the HRM bass pot high with only 250k in there?

EDIT: higher values than 100R will only affect the function in that you can only turn the mids down to 0.01 and you can turn it up to...10.01 (on the knob). Both the HRM mid and bass pots are just variable resistors so it doesn't really matter how you get each resistance. 250k on full or 1M on 25%, same thing.

[ToneMerc]

Also, why 100R to ground rather than 500R or 1K or so? Is it just to leave a minimum resistance so the gain doesn't completely disappear

IMHO, I always thought that he desired a small value to keep the signal just above ground potential regardless of how the pot was adjusted and he just used a value that he already had on hand.

TM

[David Root]

I get plenty o'bass with a 250K pot on my Bloozman. I made that change after reading a thread here about the 1M being too bassy. Maybe it will need to be different with the 183 circuit. I hope not, I just bought a bunch of 20K and 250K Piher 15mm pots to go with Jason's HRM board.

The 20K mid pot is correct. The 100 ohm resistor could just have been "what HAD had (!)" He knew where exactness mattered and where it didn't.

[Fischerman]

Yeah, I can see it being easier to dial in. The 1M pot is only too bassy if you turn it up too much. But there's that ON/OFF thing that can make it difficult to dial in.

The 20K mid pot is correct. The 100 ohm resistor could just have been "what HAD had (!)" He knew where exactness mattered and where it didn't.

I recently read something regarding 'master' carpenters vs novice carpenters that applies. The novice spends a lot of time trying to figure out what to do because he knows a mistake now may be unfixable later. The master just keeps going because he knows which 'small mistakes' he can afford to make because he knows he can cover them up later or they won't matter.

[David Root]

That's likely why Stradivarius violins are so good, even though much of each one was done by apprentices. No mistakes anywhere that mattered!

Or the great Dumbles either I think, although HAD would never have made it in the Italian system, too much of a diva.

[bluesfendermanblues]

.......but there's that ON/OFF thing that can make it difficult to dial in.

I done a lot of trial an error on my Bluesmaster in order to dial the bass in, in the amounts that I like.

Both in the tonestack and on the HRM board.

I've found that a 100k log pot (and trimmer on the board) is 'better' because it allows you to 'zoom' in on the on/off sweet spot.

just my 2 cent.

[Fischerman]

Is the 100k in series with the trimmer? And is that a 1M trimmer?

Now that I think about it, I don't think I've ever had my 500k-A HRM bass control as high as 5. Next time I'm in there I might try a 470k-1M in parallel with it.

[Tonegeek]

Thinking of trying this. I used T 250K, B 250K and M 20K/100R on my Bloozman (HRM Bluesmaster), worked very well. I understand you don't want too much mids in OD, especially if you have Mid Boost on a FSW.

Still wondering about that 20K though.

Also, why 100R to ground rather than 500R or 1K or so? Is it just to leave a minimum resistance so the gain doesn't completely disappear when the Mids pot is cranked right up? Higher R would start interfering with the 20K pot function?

Those values will work well, especially the bass trimmer. If you need more mids than the 20k can give (most likely you won't) you can up that 100R resistor to 3k3 or more.

[David Root]

Thanx Tonegeek. Maybe I'll tack in a trimpot to get it where I like it then replace w/fixed resistor.

[Tonegeek]

Thanx Tonegeek. Maybe I'll tack in a trimpot to get it where I like it then replace w/fixed resistor.

If you are referring to subbing a resistor for the mid trimmer, i wouldn't. Its funny how a month can go by and you will want to tweak it some other way. If you meant the 100r, all I can say is I leave the 100r out completely. I have never had to crank the mids more than 13k above ground on any of my amps. YMMV

[talbany]

HRM board on 192- or 185 can't remember..

Tony

[David Root]

Tonegeek, no I meant put a trimpot in place of the 100R, then replace with the value that sounds best.

Tony, what are you trying to convey with the pic? I'm on vacation this week so maybe I'm not focusing too well.....?

[jelle]

Some early HRM amps have fixed networks for the HRM settings.

Jelle

[David Root]

OK, I didn't know that!