Tone Circuit question

[pbman1953]

After living for while with my Traynor YBA3, I notice that the Bass, Bass Expander and presence controls don't do much until 1:00 on the dial.
Do you know if this is normal? Would it matter a few parts were changed to make this happen?


Parts changed were-


R13- from 22k to 15k


R15- form 150ohm to 130ohm


R17 & 18- from 1ook to 220 k


C12- from.001 to .002


On a side note-


Recently I bought a set of Aero Jazz pickups for a Jazz bass. The company suggests that the 2 volume pots should be 250k Audio and the tone to be 250k linear instead of audio. He said that Fletcher & Munson made the study years ago and human hearing with a linear pot works better. On Talk Bass it's still 75/25 in favor of Audio. I have an audio in there now and it's nice and gradual , which makes sense to me.


What do you all think?

[Willabe]

After living for while with my Traynor YBA3, I notice that the Bass, Bass Expander and presence controls don't do much until 1:00 on the dial.
..... Would it matter a few parts were changed to make this happen?

Maybe. Did the bass, bass expander and presence controls work better before you change parts values?


You changed R17 & 18- from 100k to 220k in the bass expander, why? The bass expander and presence controls are tied together, so changing R17/18 effected both controls.
 

Parts changed were-   R13- from 22k to 15k

Changing R13 down to 15K will give you less bass. Did the bass control work better before you changed R13's value?

If you changed those part values because you thought the low end was a little muddy or loose, might have been better to change C9 and if you still needed more than C1 also to smaller values.   

[pbman1953]

It's been a while since I made the changes and hard to remember how they were. I think I was told that the changes would be more Bassman like. I can change them back if you feel I'd get better performance. 


Other changes were-


c1- 250mf to  220mf


c2-  .022 to a .01


c9- 250 to a 220mf


R3- 470k to 1meg


R4- 68k to 1.5k



r12- 100k to  82k


c34- 10mf to 16mf


r43 - 82k to 8.2- unless I'm reading it wrong and it's really a 8.2 on paper

[Willabe]

It's been a while since I made the changes and hard to remember how they were. I think I was told that the changes would be more Bassman like. I can change them back if you feel I'd get better performance.

Why did you want that amp to sound more like a bassman? Bassman's aren't great bass amps, they're only so-so for bass.   

That amp is probably a much better bass amp.

If it were my amp, I'd put it back stock and play it for a little bit. Then see if I wanted to change anything.

Is it a combo or head and cab? What speaker(s) do you use with it?

[pbman1953]

One of the goals for the changes were to calm the middy tone nature of the amp. Would any of those changes have done that?

[Willabe]

I take it you are a bass player, you ask about pot tapers?

I worked a music store years ago as a tech. They got Traynor bass amp in on trade, don't remember which model. It was a head with 4 x EL34's and a 2 x 15" closed back speaker cab. I changed the tubes, owner of the store wouldn't let me do a cap job.

We plugged a couple different guitars into it after I changed the tubes, sounded very good. I was very surprised at the time. Sounded a little/more like a Marshall. Definitely did not sound like a Fender.     

[Willabe]

One of the goals for the changes were to calm the middy tone nature of the amp. Would any of those changes have done that?

You changed a lot of things. 

So you wanted to scoop the mids for bass playing? 

[pbman1953]

This amp is a head only. I use it with either 1 or 2 cabs with JBL 15's.
The amp was always a bit on the middy side. Like an SVT. I like a softer smoother midrange more than a pronounced one.

[Willabe]

Well, all that you did seems to have made your bass, bass expander and presence controls not work very well. 

Did you make all the changes at once and then play through it or did you do them 1 at a time and listen for any change?

R13 that you changed from 22K to 15K, I think that's the mid resister? Smaller, which you did, should lessen the mids? Fender used a 6.8K there.

There is also R11-  100K, looks like a slope R?

(Edit; That's a James tone stack.)

I'd put it back stock and try to tweak a little at a time. You changed a LOT of parts values.

Some of the other guys will know how to scoop the mids.

Here's your schematic again.

https://el34world.com/Forum/index.php?action=dlattach;topic=27926.0;attach=93893   

[pbman1953]

I changed them in one shot

[Willabe]

Unless you know for sure that it's a proven 'mass mod' that was a LOT to change all at once.

Did those changes scoop the mids like you wanted?

[Willabe]

That's a James tone stack. The treble/bass controls work different than a Fender/Marshall/Vox TS. With the James TS, the mids never move as you turn up/down the treble/bass controls. Set the treble/bass full cut, you get a mid hump, set them both full up you get a mid cut.

Here play with Duncans TS calculator, set the controls like I just described and you'll see the mid hump/scoop;

http://www.duncanamps.com/tsc/index.html

I put in a 10K for R13 and it did scoop the mids some more. I didn't play with the 100K/R11 slope R.

I think you have to put R17/18 back to 100K to get the bass expander pot to work better again.

Here's the tone controls and bass expander circuits.

[pbman1953]

The changes helped the mids

[Willabe]

Ok.

Read my edits in reply #11.

[pbman1953]

I have the amp on the bench and it seems that I brought R's 17 & 18 back to 100k. already


By accident I came across something interesting. I wired both a 10k and 22k to the supply wire. I clipped a alligator to ground so I could flip back and forth to see the difference between the two values. The 22k was more alive than that 10k . Then by accident the clip fell off and with no connection the amp was more lively and more volume. Any resistor sems to rob output. Yes, the there were a bit more mids and the enhancer and presence seem to work better. Until I hear from you I may try a higher value just to experiment.



Just to recap , should I still go back and revert to all stock values?

[Willabe]

I have the amp on the bench and it seems that I brought R's 17 & 18 back to 100k. already.

Ok.

By accident I came across something interesting. I wired both a 10k and 22k to the supply wire. I clipped a alligator to ground so I could flip back and forth to see the difference between the two values. The 22k was more alive than that 10k . Then by accident the clip fell off and with no connection the amp was more lively and more volume.  Until I hear from you I may try a higher value just to experiment.

That's interesting. The 22K bass control tail R, R13, gives more mids, but you liked it.

Any resistor seems to rob output. Yes, the there were a bit more mids and the enhancer and presence seem to work better.

Yes, R13 is a path to ground for the mids. The larger you make it, the more mids you keep. All TS's have insertion losses, if you disconnect R13, you remove any loss from the bass/mid side of the James TS. But I don't think the bass control will work then or very little.     

Just to recap , should I still go back and revert to all stock values?

Yes, I would start all over.

Some of the changes you made effect the gain structure and some effect the tone structure of that amp and that could be/are messing with the effect of the controls.

That's a more complicated amp than your basic BF Fender AB763 or tweed. Traynor knew what he was doing. He voiced/balanced that amp and with all the changes you made, you've thrown that (way?) off.

I would restore it back to stock and if needed tweak the mids a little to your liking. It will be easier to go from stock.

[Willabe]

Play around with this it's easy. 

That's a James tone stack. The treble/bass controls work different than a Fender/Marshall/Vox TS. With the James TS, the mids never move as you turn up/down the treble/bass controls. Set the treble/bass full cut, you get a mid hump, set them both full up you get a mid cut.

Here play with Duncans TS calculator, set the controls like I just described and you'll see the mid hump/scoop;

http://www.duncanamps.com/tsc/index.html

I put in a 10K for R13 and it did scoop the mids some more. I didn't play with the 100K/R11 slope R.

[Willabe]

I read some last night in a book I have, TUT 3 KOC, and he's talking about you amp.

(In reference to a couple R values you posted;)

After reading it, I believe R43 IS 82K. He said Traynor set that gain stage up as a split load but only tapped the signal from the plate. Said it was to give a light load to the next stage.

EDIT: R43 is not 82K. Traynor used 82K in the Bass Master amp. I was looking at the wrong Traynor. You are correct, in TUT3 he shows the YBA-3 as R43 is 8.2K (8K2). Sorry for the confusion.   

And R4 can't be 68K. 

Does your amp have the schematic in side the head on the top plate? 

[Willabe]

How where you setting your bass/treble controls?

You can get a pretty good mid scoop with that TS.

[pbman1953]

While I was waiting I was experimenting with the R 13 value. I tried a 10k, 22k and back to the 15k. After listening the 10 was too dull then I volleyed between the 22 and the 15. At one point I made a 32k. But that didn't last long. I settled on an 18.3k with adding together a 15 K & 3.3k. So far I like that.


I have plenty of gain but I was impressed how the amp seemed to clear up with R13 not connected. You say that the r4 shouldn't be 68k? But that's what the original is. If not what should it be? There's 1.5k now.


Tone usage- All up full then back off until it sounds good to me


"Does your amp have the schematic in side the head on the top plate? "-  no. I have the one that I sent at the start of this. Just lie the one you sent me.

[pbman1953]

Putting a 82k at r43 killed my gain

[Willabe]

Putting a 82k at r43 killed my gain.

Yes, but you have a lot of other changes you made that throws off the gain in that amp from what it was. Can't just change that 1 R.   

Edit; See reply #17's edit. Sorry, my mistake.

[pbman1953]

Ok, I'll keep working on it thanks!


Did you see my r4 68k question on a couple posts back?

[Willabe]

While I was waiting I was experimenting with the R 13 value. I tried a 10k, 22k and back to the 15k. After listening the 10 was too dull then I volleyed between the 22 and the 15. At one point I made a 32k. But that didn't last long. I settled on an 18.3k with adding together a 15 K & 3.3k. So far I like that.

Ok.

I have plenty of gain but I was impressed how the amp seemed to clear up with R13 not connected. You say that the r4 shouldn't be 68k? But that's what the original is. If not what should it be? There's 1.5k now.

R4 is V1A cathode (K) resistor, pin 8. Looks like 820 ohm to me on the schematic. It's 820 ohm in the TUT book too for the YBA-3. If you have 68K at pin 8, that's killing all the gain for that input stage. This is part of why I said to put everything back to stock and tweak from their if still needed.

You changed so many R/C values you changed the gain and frequency voicing of that amp. Your working backwards now, piece meal. That amps circuitry is more complicated than a classic Fender/Marshall. I keep saying this, but I think it's very true, It will be much easier to restore it to stock than tweak if needed.

Tone usage- All up full then back off until it sounds good to me

Are they both still past 12:00? They will only scoop the mids if their past 12:00. James TS with both treble/bass set at 12:00 is flat frequency response. The more you turn up the treble/bass the more the mids get scooped.

"Does your amp have the schematic in side the head on the top plate? "-  no. I have the one that I sent at the start of this. Just like the one you sent me.

Ok.

[Willabe]

Did you see my r4 68k question on a couple posts back?

Yes, see reply #23.

[pbman1953]

Ok, ill get back to stock, then report back on gain, usage and tone settings
Thanks!

[Willabe]

Sluckey, anybody, is this a slightly modified James TS?

It doesn't have a R in series between the bass/treble pots, unless the schematic is drawn wrong?

[sluckey]

Putting a 82k at r43 killed my gain

Zoom in and look closely at the schematic. I see 8.2K. 82K is way too much and cannot be correct. The YBA3A even shows a 4.7K in that position (same circuit for V1).

[sluckey]

Sluckey, anybody, is this a slightly modified James TS?

yes

[Willabe]

Putting a 82k at r43 killed my gain

Zoom in and look closely at the schematic. I see 8.2K. 82K is way too much and cannot be correct. The YBA3A even shows a 4.7K in that position (same circuit for V1).

Thank you Sluckey.

 Yes, you are correct, see my edit in reply #17.

I was looking at the wrong Traynor bass amp.

[Willabe]

Sluckey, anybody, is this a slightly modified James TS?

yes

Thank you. 

[Willabe]

Putting a 82k at r43 killed my gain.

Yes, sorry, my mistake, see edit in reply #17.

[Willabe]

You can leave the K bypass caps as they are for C1 and C9.

Really won't make much if any difference changing them back to 250uF from 220uF.

[pbman1953]

I have1 item left


R4- Looking at the schematic I see 68k and you see a 82k? If so you may be looking at the YBA-3A Super. Check the tubes, if you see 6kg6 then you have the wring schematic

[sluckey]

I have1 item left


R4- Looking at the schematic I see 68k and you see a 82k? If so you may be looking at the YBA-3A Super. Check the tubes, if you see 6kg6 then you have the wring schematic

I'm looking at the schematic you posted in your original post and R4 is 820Ω.

[pbman1953]

You're right, there's an R4  off  pin 3 of tube 1B,


There's a second r4 (68k) off pin 1 of 1B, connected to c33(.1)


Question-


For r22 I have a 82k, schematic askes for a 52k, change it?  If changed , do I need to re-bias?


Also, these may have been a forum suggestions years ago
R52 & R51 are 4.6K
R's 24 & 25, 26 & 27 are 100k
change back to 1.5k or leave? 
r28 & 29- was 47 ohm, now 1k/5w and there's one for all 4 tubes

[sluckey]

There's a second r4 (68k) off pin 1 of 1B, connected to c33(.1)

How 'bout that! But it's not connected to V1B pin 1. It's connected between C33 and V2A pin 7.

For r22 I have a 82k, schematic askes for a 52k, change it?

That draftsman sure has poor penmanship! R22 should be 82K. That's a very common value for the resistor in that circuit. Besides, 52K is a non-standard value for that time period.

R52 & R51 are 4.6K

Are you sure? 4.6K is a non-standard value. No matter. Change both to 1.5K IAW the schematic.

R's 24 & 25, 26 & 27 are 100k
change back to 1.5k or leave?

R24 and R25 should be 220K. Change 'em. R26 and R27 should be 1.5K. Change 'em.

r28 & 29- was 47 ohm, now 1k/5w and there's one for all 4 tubes

I actually like this change. However, in keeping with "make it stock IAW the schematic", I have to say change 'em to 47Ω and only two resistors.

[pbman1953]

I should of mentioned that I use 4 6550 tubes, that why the changes for 24-29 were made.


Does that change your last instruction?

[sluckey]

Yes it does. Replace the 6550s with EL34s IAW the original schematic. Anything else you been holding out?   

[pbman1953]

I'd rather stay with 6550's and here's your suggestion 6 years go-




QuoteRemoved the two 47Ω screen resistors, installed four 1kΩ 5W screen resistors...
...Above step two is to remove the 2- 47 ohm resistors. The install 4- 1k 5W , but doesn't explain what connection type.

This is probably a good idea. If pin 6 is not used this is how I would do it...First remove all wires and or resistors from pin 4 of all four tubes. Now connect all pin 6s together and also connect a wire from one pin 6 to R30 (If R30 had been connected directly to pin 4 of a socket just reconnect it to pin 6 of that same socket). Finally, mount a 1K/5W resistor between pin 4 and 6 of each power tube socket. (Leave the leads a little long so the resistor will sit high above the socket.)

[tubeswell]

Sluckey, anybody, is this a slightly modified James TS?

yes

The treble expander and bass expander (with presence) are both 'active' tone control circuits based on local negative feedback loops hooked around the gain stages that they work off

[Willabe]

Thanks Pete. 

[pbman1953]

I get the message.


I'm done and it seems to working fine, thanks for everyone's input

[sluckey]

Just refreshed my memory on this project. You've created quite a tar-baby here. Sorry I slapped it. Again! 

[pbman1953]

No worries, I'm in good shape.

[sluckey]

It was my fault for getting tangled up. I just jumped in the middle of this discussion mistakenly thinking you had an amp that 'someone' had messed up with some weird component values and you were trying to return it back to stock but having difficulty reading the correct values from the poorly annotated schematic. If I had started reading this thread at the beginning (like I should have) I would have realized what was going on and probably would not have commented. Sorry for my confusion.

We're all good.   

[Willabe]

I take it when you switched to 6550's you removed the -bias voltage from pin 1 (suppressor grid/G3), on the power tube sockets?

[pbman1953]

Both 1 and 8 are grounded

[pbman1953]

It was my fault for getting tangled up. I just jumped in the middle of this discussion mistakenly thinking you had an amp that 'someone' had messed up with some weird component values and you were trying to return it back to stock but having difficulty reading the correct values from the poorly annotated schematic. If I had started reading this thread at the beginning (like I should have) I would have realized what was going on and probably would not have commented. Sorry for my confusion.

We're all good.   

No worries, you and all your A team buddies are helping the rest of us


Thank you!