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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Thu May 18, 2017 8:13 pm
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The Telefunken is a great tube if its a genuine West German vintage tube. The originals have a diamond impression in the glass between the pins. Sometimes it will have a few numbers there too.. Its better than the JJ.

The taper of the Master has always been an issue. The lll does have the same volume as earlier versions, but less bass in the drive channel. The audio taper replacement does give finer resolution, but wouldn't change the tone. I don't know what the tapers of the new pots are, but your issue is not enough gain at a certain tone.

Changing the guitar's volume control is cheap and easy. If the tone imalance is in the guitar, no amount of amp mods will remedy that problem, only compensate. That's not a good path to high performance. Just try one guitar and see what kind of difference it makes.

Rebalancing the guitar is also important because you have to get more gain out of the amp and that will accentuate the ice-pick effect of the guitar. If you want to eliminate the boost pedal, you need more gain out of the amp..
So lets back up and.ask, is this a drive channel problem or clean, or both?
There is plenty of gain to be had here.Lowering R18 130K will raise the clean gain. Changing the Master R26 to a 250K audio taper will give free gain to the drive channel.. Its the same part as the volume pots.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Fri May 19, 2017 9:14 am
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TimsAudio wrote:
The Telefunken is a great tube if its a genuine West German vintage tube. The originals have a diamond impression in the glass between the pins. Sometimes it will have a few numbers there too.. Its better than the JJ.

The taper of the Master has always been an issue. The lll does have the same volume as earlier versions, but less bass in the drive channel. The audio taper replacement does give finer resolution, but wouldn't change the tone. I don't know what the tapers of the new pots are, but your issue is not enough gain at a certain tone.

Changing the guitar's volume control is cheap and easy. If the tone imalance is in the guitar, no amount of amp mods will remedy that problem, only compensate. That's not a good path to high performance. Just try one guitar and see what kind of difference it makes.

Rebalancing the guitar is also important because you have to get more gain out of the amp and that will accentuate the ice-pick effect of the guitar. If you want to eliminate the boost pedal, you need more gain out of the amp..
So lets back up and.ask, is this a drive channel problem or clean, or both?
There is plenty of gain to be had here.Lowering R18 130K will raise the clean gain. Changing the Master R26 to a 250K audio taper will give free gain to the drive channel.. Its the same part as the volume pots.


Yes, for your explanation I think is a real telefunken.



I use only the clean mode, never use the drive or more drive (I think are cheap sounding). Is a clean mode problem.

My amp after the Formel mod is like this:

Volume (R6) A100k
Drive (R7) 15A250k
Treble (R13) 30A250k
Bass (R14) 15A250k
Mid (R15) B25k
Master (R26) B100k

My stratocaster has a Volume pot of 250k (gets harsh when amps's volume goes up 4)
My telecaster has a volume pot of 500k (is a thinline and has humbuckers, the previous owner has modified to get rid of the muddy tone) but for me is harsh when the amp's volume goes up 4.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Fri May 19, 2017 1:22 pm
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algajgg wrote:
TimsAudio wrote:
The Telefunken is a great tube if its a genuine West German vintage tube. The originals have a diamond impression in the glass between the pins. Sometimes it will have a few numbers there too.. Its better than the JJ.

The taper of the Master has always been an issue. The lll does have the same volume as earlier versions, but less bass in the drive channel. The audio taper replacement does give finer resolution, but wouldn't change the tone. I don't know what the tapers of the new pots are, but your issue is not enough gain at a certain tone.

Changing the guitar's volume control is cheap and easy. If the tone imalance is in the guitar, no amount of amp mods will remedy that problem, only compensate. That's not a good path to high performance. Just try one guitar and see what kind of difference it makes.

Rebalancing the guitar is also important because you have to get more gain out of the amp and that will accentuate the ice-pick effect of the guitar. If you want to eliminate the boost pedal, you need more gain out of the amp..
So lets back up and.ask, is this a drive channel problem or clean, or both?
There is plenty of gain to be had here.Lowering R18 130K will raise the clean gain. Changing the Master R26 to a 250K audio taper will give free gain to the drive channel.. Its the same part as the volume pots.


Yes, for your explanation I think is a real telefunken.



I use only the clean mode, never use the drive or more drive (I think are cheap sounding). Is a clean mode problem.

My amp after the Formel mod is like this:

Volume (R6) A100k
Drive (R7) 15A250k
Treble (R13) 30A250k
Bass (R14) 15A250k
Mid (R15) B25k
Master (R26) B100k

My stratocaster has a Volume pot of 250k (gets harsh when amps's volume goes up 4)
My telecaster has a volume pot of 500k (is a thinline and has humbuckers, the previous owner has modified to get rid of the muddy tone) but for me is harsh when the amp's volume goes up 4.


It's important to quote that i'm using the Input 2 of my Hot Rod Deville.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Fri May 19, 2017 7:15 pm
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My schematics show a 250K for the volume pot. The same as the drive pot.
That could be where your gain went. The 100K will drain more signal to ground. Is that a change you made?
Also, I would try the Number 1 jack. I think it increases the gain by 10dB

You're right, there's not much room to mod the guitar volume controls. Its got to be the amp. The volume control is suspect to me.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Sat May 20, 2017 6:29 pm
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TimsAudio wrote:
My schematics show a 250K for the volume pot. The same as the drive pot.
That could be where your gain went. The 100K will drain more signal to ground. Is that a change you made?
Also, I would try the Number 1 jack. I think it increases the gain by 10dB

You're right, there's not much room to mod the guitar volume controls. Its got to be the amp. The volume control is suspect to me.


Hello Tim

It seems that Fender used different volume and master pots on the Hot Rods versions, independently of what a diagram would show up.

Originally my Hot Rod Deville came with B100k volume pot, but the Fromel mod change it to A100k. The master came with a 15A250k pot and the Fromel mod used the B100k extracted from volume to replace it. So i ended up with a 15A250k left over.

So Tim my question is: changing the current value of my volume pot from A100k to a A250 will help to achieve the same tone or voicing of the clean mode I'm after at a higher volume? in case of positive, what A250k pot should I use, 15A250k or 30A250k?

I'm not after gain or decibels alone, I mean my amp sounds really loud at 8, 9 or 10 (with that volume I can rehearse with our loud drummer perfectly, but my tone is not good, as I pointet out before is too harsh and sometimes ice picky.) My tone is good at 4 but my drummer drowns my sound.

In a forum a guy besides recommending to change the volume pot from linear to audio, he also recommends to change R9 and R44 values. What do you think?

Once more Tim very very grateful with you for following me up till this point which I believe you narrowed down the problem. When in the previous post you said the volume drives the pre and change the voicing as the volume goes up. Now I believe is there a interaction between R6 (volume) R9 and R44. This is maybe the final puzzle for me.

Thanks in advance


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Sat May 20, 2017 9:24 pm
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I've never seen 100Ks in R6 from the factory. I've been in a number of them. Perhaps Shimmilou can comment on that.
Regardless, I would go with the value on the print. The V1a already has a lot of load on it. It has to run the loading from both the normal and drive pots.
Dropping the value to 100K makes your little Telefunken have to work all that much harder.
Go with the 250kn15A audio taper.
I would leave R9 and R41 alone. Lowering R9 would also load the tube more.
R41 could lower volume somewhat, but you would have to go up to like, 220K to make much difference. This would choke off the tone.
Changing R18 maintains the gain structure of the preamps and makes the gain change further downstream, where its less critical.

Earlier in your post, you described turning down the Bass control. This loads the delicate signals in the tone stack and dumps them to ground. If you need less bass, the best place to do it is the V1 cathode capacitor. I would change the C1 47uF electrolytic to a 2.2uF poly /50volt. This will help reduce bass response and focus the amps power toward the midrange.
If your midrange tone is riding on a big bass harmonic, it phase shifts the mids, causing them to distort, so cutting bass improves the quality of the mids.
It may not seem like much, but it makes a big difference.
I would also change C7 to a silver-mica if it hasn't been changed already. This cleans up the treble


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Sun May 21, 2017 1:01 pm
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TimsAudio wrote:
I've never seen 100Ks in R6 from the factory. I've been in a number of them. Perhaps Shimmilou can comment on that.
Regardless, I would go with the value on the print. The V1a already has a lot of load on it. It has to run the loading from both the normal and drive pots.
Dropping the value to 100K makes your little Telefunken have to work all that much harder.
Go with the 250kn15A audio taper.
I would leave R9 and R41 alone. Lowering R9 would also load the tube more.
R41 could lower volume somewhat, but you would have to go up to like, 220K to make much difference. This would choke off the tone.
Changing R18 maintains the gain structure of the preamps and makes the gain change further downstream, where its less critical.

Earlier in your post, you described turning down the Bass control. This loads the delicate signals in the tone stack and dumps them to ground. If you need less bass, the best place to do it is the V1 cathode capacitor. I would change the C1 47uF electrolytic to a 2.2uF poly /50volt. This will help reduce bass response and focus the amps power toward the midrange.
If your midrange tone is riding on a big bass harmonic, it phase shifts the mids, causing them to distort, so cutting bass improves the quality of the mids.
It may not seem like much, but it makes a big difference.
I would also change C7 to a silver-mica if it hasn't been changed already. This cleans up the treble


Tim

Thank you again. This next weekend I'll do the following:

- Change the good quality alpha A100k volume pot to the original fender 15A250k
- Change C1 47 uf to 22 uf (you write 2.2 uf, but I dont understand if it is .22 .022 or .0022?) poly (when I learn to load pics in this forum I’ll post pics of some caps that may suit for this).
- Put a on/off switch to have both tone stacks (twin and hot rod)
- And to play at room levels I’ll try what you said in a previous post: To lower the gain in a more stable way than tube substitution, I Mount a small switch between the tubes and wire in a 10K resistor to parallel with R69 47K on the tube board. This drops the gain of the power stage for Club level dynamics and studio use. Question: what kind of resistor to the 10k?

Thanks


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Sun May 21, 2017 1:57 pm
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Yes, I meant 2.2 uF. It takes that big of a change to drop the bass levels by 50%
The 10K should be carbon or metal film.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Mon May 22, 2017 8:38 am
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TimsAudio wrote:
Yes, I meant 2.2 uF. It takes that big of a change to drop the bass levels by 50%
The 10K should be carbon or metal film.


Ok, I understand. If I want to put a 3 position switch for change between the stock 47uF value (bassier), the 2.2uF (treblier) and a midway value between this two, which will be this?

I would like this weekend to try another tubes in the V2 and V3 (phase inverter). Right now V2 is a 5157 RCA black plate and V3 a 12AT7 mullard. Do you think I can do it best? Maybe another Telefuenken in V2? I read a 12DW7 in V2 will help to take the pedals better, is that true? also lot of people say that the V3 has to be a balanced tube for obtaining the bes clean possible? My goal is to put the best 3 tubes JUST for clean mode. dont care about drive mode.

Thanks bro thanks and 1000 times thanks


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Mon May 22, 2017 7:36 pm
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A 4.7uF will give a little more bass, but if you have a 3 position switch, I'd try a .68/ 50 volt Poly. This cuts the bass further and is stock in many Marshalls.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Tue May 23, 2017 8:56 am
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TimsAudio wrote:
A 4.7uF will give a little more bass, but if you have a 3 position switch, I'd try a .68/ 50 volt Poly. This cuts the bass further and is stock in many Marshalls.


When you say Poly, you mean Polyester, polyprophylene or both?


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Wed May 24, 2017 8:08 am
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TimsAudio wrote:
I've never seen 100Ks in R6 from the factory. I've been in a number of them. Perhaps Shimmilou can comment on that.
Regardless, I would go with the value on the print. The V1a already has a lot of load on it. It has to run the loading from both the normal and drive pots.
Dropping the value to 100K makes your little Telefunken have to work all that much harder.
Go with the 250kn15A audio taper.
I would leave R9 and R41 alone. Lowering R9 would also load the tube more.
R41 could lower volume somewhat, but you would have to go up to like, 220K to make much difference. This would choke off the tone.
Changing R18 maintains the gain structure of the preamps and makes the gain change further downstream, where its less critical.

Earlier in your post, you described turning down the Bass control. This loads the delicate signals in the tone stack and dumps them to ground. If you need less bass, the best place to do it is the V1 cathode capacitor. I would change the C1 47uF electrolytic to a 2.2uF poly /50volt. This will help reduce bass response and focus the amps power toward the midrange.
If your midrange tone is riding on a big bass harmonic, it phase shifts the mids, causing them to distort, so cutting bass improves the quality of the mids.
It may not seem like much, but it makes a big difference.
I would also change C7 to a silver-mica if it hasn't been changed already. This cleans up the treble



You won't believe this Tim! I opend the back of my amp for preparing it for this weekend mod and discoverd that my tech has installed the Fromel kit which include a change in the MID pot from .022 to .015 and the BASS pot remains the same .1 but better quality orange drop (Xicon I think), well guess what! ................ my tech inverted this values in the installation of the kit so actually my amp has a .1 orange drop cap in the MID pot and a .015 millard 150M type in the BASS pot.

Do you think this has something to do with the harsh and ice picky sounds I'm complaining about? Could you tell in more technical language what has been happening her with this mistake?


I'm mad but at the same time happy because I think this weekend I'll have a very different sounding amp and all my PITA will dissapear : - )


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Wed May 24, 2017 8:15 am
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Certainly having the right parts is important to good tone. Check to see if the mid pot is still shorted. You've got good eyes to spot what your tech couldn't. Good on ya.
Either cap will work fine. Poly is faster than electrolytics and more accurate than ceramic. There is a minor difference in voice between the two, though iM not qualified to comment there.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Thu Jun 01, 2017 1:30 pm
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TimsAudio wrote:
Certainly having the right parts is important to good tone. Check to see if the mid pot is still shorted. You've got good eyes to spot what your tech couldn't. Good on ya.
Either cap will work fine. Poly is faster than electrolytics and more accurate than ceramic. There is a minor difference in voice between the two, though iM not qualified to comment there.



Hello Tim

Finally this last weekend a friend and me put the hands on the Hot Rod Deville and the amp is now a different beast!

- Change the A100K for a 15A250K in the volume pot (no more harsh or ice picky frequencies when volume goes up 4)


- The mid and bass caps were inverted as I spoted in the previous post. (That made a lot of difference now the amp has the right frequencies that cut like butter. I heard your advise and instead of putting the .015 mid cap (fromel mod) I restore the original value with a .022 Original Orange Drop SPRAGUE PS series.


- Change electrolytic 47uF in the C1 for a electrolytic 22uF 25V (still looking for the poly caps with values like 10uF, 2.2 uF or 0.68 uF for the 3 position switch). I found the bass not as predominant as before. And i really like that, actually I want to try a 10uF to see if I like it better.

- I removed the 330 ohms power resitors and installed the original ceramic ones, but soldered longer legs to them and intalled them in the pcb board very but very retired (would like to post some pics but dont know how to load them in this forum).


I'm extremely happy with the results. I'm so much greatful for all your support. Really all your guidance made me spot the mistakes in my amp.

What's next: Since I never use the Drive and master knobs (drive and more drive modes) I've been thinking in removing this pots and replace them with rotary knobs for vary the values of C1 (22,2.2 and 0.68 uF) and four values for R12 ( 54k, 86k 100k, 130k). What do you think about this? should I be careful with anything in particular?

Do you have any commets, recommnedations in general? Still more room to improve int this amp?

Very happy but still experimenting.

Thanks in advance


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Fri Jun 02, 2017 9:25 am
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I simple mod can be done to give you two normal channels and a different kind of More Drive.
It can be a switched thing, but if you NEVER use drive, just unsolder the coil of Relay 2.
It will prevent the extra gain stage V2b from switching in.
The drive control is your volume. The master doesnt work.
The second channel sounds a little thinner because C23 .015 passes higher frequencies than C18 .022.
Also,the bright switch effect is reduced and C3 250pF bleeds off treble at the grid of V2a.
You can tweak the values of C3 & C23 to get a custom tone.
Switching into More Drive increases the gain of V2a and thins it out a lot. Its an interesting tone.
I did this mod for surf rock players that wanted minimal tone changes, but a different volume.
It might work for you.


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