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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Fri Jun 02, 2017 4:05 pm
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TimsAudio wrote:
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.


Ok this sounds even more interesting Tim. Just to get it right.

- Should I unsolder the coil Relay 2 in order to not use the gain of the DRIVE mode? so when I select the drive mode with the fender switching I dont get any aditional gain?

- I've been looking for Relay 2, but can't find it. It's not my purpose to drive you nuts but if you know the code or number of this part pleaese let me know for spot it.

- When you say the master doesn't work in this mod, it means I can replace it for another kind of pot for any other purpose?

All this thing is so so so much interesting for me and I'm having lot of fun. Can't wait to the reharsal with the band. All your help here is really invaluable for me.

I imagine setting the clean mode for the arpeggios, and the drive mode (that will be clean too) for the rhythms. Great!

Once more. Thanks in advance.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Sat Jun 03, 2017 8:57 am
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The relay, K2 is shown in the schematic in 3 sections.
It is a plastic box between V2 and the reverb IC.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Sat Jun 03, 2017 3:17 pm
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TimsAudio wrote:
The relay, K2 is shown in the schematic in 3 sections.
It is a plastic box between V2 and the reverb IC.



Thank you so much Tim.

I found K2 an U2. Are like chips color black. Thanks. I read a post from you in another topic of this forum you recommend to replace the U2 (reverb chip) for upgrading the quality of the reverb. Do you recommend to do this replacement along with the removing of the R103?


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Sun Jun 04, 2017 11:22 pm
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TimsAudio wrote:
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.


Tim

Hello, I think I found something really interesting referring to a Hot Rod Deluxe in another forum:

Now moving on to the negative feedback circuit… My new OT has 8, 4, & 2 ohm taps. Of course, the 8 ohm tap is connected to the 8 ohm speaker, but the schematic shows the 4 ohm tap connected to the NFB on the stock amp. I originally had the NFB connected to the 8 ohm tap and it was too sterile. Connecting the 4 ohm tap to the NFB was better, and switching to the 2 ohm tap was more better. I also lowered R68 to 3.8K and there was the happy medium. It now has much of the no–NFB feel, but with a little more high & low frequency control overall, plus, I still have use of the presence control. I put a SPDT in the second speaker jack-hole to switch between the 4 and 2 ohm taps for NFB.

What do you think? I really love the idea of finding another color of the amp with just the flip of a switch. If you need more info I have plenty of. This actually is the last post of the topic.

Very eager to hear your comments here.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Mon Jun 05, 2017 2:47 am
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algajgg, before you mod your amp to death, try some lower gain tubes first. Namely, a 5751 in V1 and a 12AT7 in V3. This will do wonders for the tone, and is way easier than all of the mods you are talking about, and is also easily reversible, unlike the mods. :wink:

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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Mon Jun 05, 2017 4:02 am
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[quote="shimmilou"]algajgg, before you mod your amp to death, try some lower gain tubes first. Namely, a 5751 in V1 and a 12AT7 in V3. This will do wonders for the tone, and is way easier than all of the mods you are talking about, and is also easily reversible, unlike the mods. :wink:[/quote ]

Hello Shimmilou

Jajjajaj you really made my day. I'm a new enthusisast with all this mods. Yes I have a Telefunken in V1, RCA 575I in V2 an a 12At7 in V3.

What do you think about eliminating the negative feedback in this amp Shimmilou? I have read from various guys and they insist in an improvement in tone. Some just cut R69 or put a switch in it. Anothers throw a pot. What do you think?


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Mon Jun 05, 2017 6:55 am
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No. Don't do that.
His first mistake is thinking his new ot is better than the factory one. Theres no fix for that.
The no-nfb bunch are playing at lower volumes than you describe.
Its a bouncy, punchy sound, but headroom disappears quickly. The Hrdv already has plenty of that.
The nfb also stabilizes the main stage from uncontrolled oscillation. It acts as a shock absorber for high volumes.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Mon Jun 05, 2017 12:47 pm
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TimsAudio wrote:
No. Don't do that.
His first mistake is thinking his new ot is better than the factory one. Theres no fix for that.
The no-nfb bunch are playing at lower volumes than you describe.
Its a bouncy, punchy sound, but headroom disappears quickly. The Hrdv already has plenty of that.
The nfb also stabilizes the main stage from uncontrolled oscillation. It acts as a shock absorber for high volumes.



Thank you very much Tim. I'm planing my nest and final mod session. With this one I'll fine tune some details and leave the amp that way, its time to play a loooot.

I'll forget this crazy no negative feedback plan.
So you say no matter which OT for an upgrade (mercury or vintage tone) the tone won't get better?

I'll stick with the following mods for the next episode:

- Eliminate K2 and have a 2 clean modes. (your idea thanks again)

- Switch of 3 positions for the volume bright cap (position 1: desactivate bright cap. position2: activate cap 100pf. position 3: adds another 100 pf). I'll use this bright caps just with the clean mode an no pedals. With pedals this bright caps is no good.

- Switch on/0ff for the R103 reverb. Some people say with this resistor engaged has a brittle sound that is suitable for strats and teles, so I dont want to get rid of it at all.

- Switch for 3 positions C1. (22 uf electrolityc (installed right now), 2.2 uf poly, 0.68 poly) still looking for the polys.

- Switch 3 positions for C24 (stock .022, .001 uf, .0047uf) the author of the book How to Hot Rod a Fender amp in its page 113 talks about lowering the value of this cap for tighten the lows a bit and clarify the highs.

- Rotary for R12 $@!&# resitor (56k,82k,100k,130k) I think I could take more advantage of the amp in a box pedals i have playing with the Center frequencyes values.

- Reading about the Snubber circuit. Would like to know what do you think about it for this amp. Nicer cleans?

- You say in another post that a good upgrade for the U2 reverb will be the TL2072. I was looking for it but found that some are TLE2072IDR, CP, CDR, ID, CD. Which one should I get?

Tim once more very greatful with you. I dont want to drive you nuts, but all your guidance is gold for me, take your time to answer. I live in Venezuela, a country that is in a critical crisis right now, so I have no one could help me out in here. Good techs already leaved this country and I don't believe they have the notable expericence I've realized you have with this amp.

Please follow me up, I promise I'm about to achieve my perfect amp.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Tue Jun 06, 2017 8:48 am
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Do not remove the K2 relay. You need the NC contacts to complete the normal channel circuit. Just unsolder pins 1& 16 and be sure they don't touch the board.
You need to be careful with a lot of mods as they can cause unexpected interactions.
Cathode mods are low voltage and not directly in the signal path.
R12, however, is a plate resistor whose voltage can reach 300DC. So running these wires will cause crosstalk wherever they are routed. Also, the switch will pop and arc a little bit.
C24 and the bright caps are in the signal path and are very susceptible to picking up crosstalk. Unless shielded wire is carefully routed, oscillation may occur.
I would use 10pf, 47pf and 100pf for the bright cap
switch
The TLE2072CP is a good choice for the reverb IC. The I suffix is expanded temperature rating. You don't need that. If you use the Effects loop, a second one in U1 will improve the quality of your pedals.
There are 2 grades of these chips. The input offset current of one series is 5ua, the premium one, 3.5ua. This additional sensitivity is coupled with hand trimmed laser offset adjustment of their premium Excalibur series. They are 30% higher price.
The sensitivity can cause oscillation in some amp layouts, but in the HRDV it is stable.
The improvement in reverb quality will make the R103 switch unnecessary.
In general, fewer extra switches = fewer unpleasant surprises. Figure out your preferences and then hardwire them in.
In practice, the Deluxe is an excellent platform for modifications on the fly. That is, the circuit board can be pulled without disconnecting any wires. If you connect a jumper to the green ground lead, you can run it in that configuration and cut and try your component changes easily before installing a switch.
I guess this is the point we insist this can SHOCK THE LIVIN ¥₩€&% out of you if yer not careful to DISCHARGE.
C30 acts as a snubber here. Additional snubber circuits are unnecessary for a stable amp and don't improve tone. CR 4&5 act as safety dampers in the same capacity by absorbing reverse currents. This improves damping.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Wed Jun 07, 2017 8:21 am
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TimsAudio wrote:
Do not remove the K2 relay. You need the NC contacts to complete the normal channel circuit. Just unsolder pins 1& 16 and be sure they don't touch the board.
You need to be careful with a lot of mods as they can cause unexpected interactions.
Cathode mods are low voltage and not directly in the signal path.
R12, however, is a plate resistor whose voltage can reach 300DC. So running these wires will cause crosstalk wherever they are routed. Also, the switch will pop and arc a little bit.
C24 and the bright caps are in the signal path and are very susceptible to picking up crosstalk. Unless shielded wire is carefully routed, oscillation may occur.
I would use 10pf, 47pf and 100pf for the bright cap
switch
The TLE2072CP is a good choice for the reverb IC. The I suffix is expanded temperature rating. You don't need that. If you use the Effects loop, a second one in U1 will improve the quality of your pedals.
There are 2 grades of these chips. The input offset current of one series is 5ua, the premium one, 3.5ua. This additional sensitivity is coupled with hand trimmed laser offset adjustment of their premium Excalibur series. They are 30% higher price.
The sensitivity can cause oscillation in some amp layouts, but in the HRDV it is stable.
The improvement in reverb quality will make the R103 switch unnecessary.
In general, fewer extra switches = fewer unpleasant surprises. Figure out your preferences and then hardwire them in.
In practice, the Deluxe is an excellent platform for modifications on the fly. That is, the circuit board can be pulled without disconnecting any wires. If you connect a jumper to the green ground lead, you can run it in that configuration and cut and try your component changes easily before installing a switch.
I guess this is the point we insist this can SHOCK THE LIVIN ¥₩€&% out of you if yer not careful to DISCHARGE.
C30 acts as a snubber here. Additional snubber circuits are unnecessary for a stable amp and don't improve tone. CR 4&5 act as safety dampers in the same capacity by absorbing reverse currents. This improves damping.



Hello Tim. thanks so much again. I've squeeze all what you wrote and will apply it all soon. You have no idea what this info meas to me. Pure gold.

Just to clear up.

I've been looking here in Venezuela for the TLE2072' but still no luck (I've opened all my pedals in order to see if there's that IC chip inside jijiji). What I've found here is the OPA2134 some people recommend as a replacement for the TL207. By chance have you tried OPA2134 in the fx loop of the Hot rod deluxe or deville? in case yes, which one do you prefer?

My amp has a U2 reverb IC BA4560 613H22 and U1 is a TL207.

When I'll change the old reverb IC chip for the new TLE2072ACP, wont be necessary to cut R103 (should I leave it after changing the IC) or indeed I should cut R103 with the IC chip change?

CR 4&5 are parts of my amp?

Thanks in advance


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Wed Jun 07, 2017 9:44 am
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The stock chip uses bipolar transistors. Any CMOS chip, such as the TL072 will sound smoother.
The object with the TLE2072 is their higher slew rate.
This ability to change their voltage more quickly allows them to track the complex reverb signal with better agility. The result is a more defined signal.
In general, bipolar audio ics have less than 10V/usec slew rates
TL072 run 16 and TLE2072 runs up to 32. A high speed mod is the analog equivalent of going from 8-bit to 36-bit digital. The increase in speed and agility is needed. Each spring of the reverb tank adds its own delayed signal to the dry. The ic has to handle twice the audio information as the dry signal running through the tubes. The tubes have a slew rate of 1000. So a good ic makes a difference .
The OPA series is a Burr-Brown design. They make the highest quality chips. They were bought out by TI, the maker of the TL series chips. The OPA2134 is a good choice if that's what is available.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Thu Jun 08, 2017 12:44 pm
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TimsAudio wrote:
The stock chip uses bipolar transistors. Any CMOS chip, such as the TL072 will sound smoother.
The object with the TLE2072 is their higher slew rate.
This ability to change their voltage more quickly allows them to track the complex reverb signal with better agility. The result is a more defined signal.
In general, bipolar audio ics have less than 10V/usec slew rates
TL072 run 16 and TLE2072 runs up to 32. A high speed mod is the analog equivalent of going from 8-bit to 36-bit digital. The increase in speed and agility is needed. Each spring of the reverb tank adds its own delayed signal to the dry. The ic has to handle twice the audio information as the dry signal running through the tubes. The tubes have a slew rate of 1000. So a good ic makes a difference .
The OPA series is a Burr-Brown design. They make the highest quality chips. They were bought out by TI, the maker of the TL series chips. The OPA2134 is a good choice if that's what is available.


Hello tim

After all your info I found the OPA2134 is 20 slew rate vs 40 slew rate TLE2072, so i decided to order for the TLE2072 and wait for the part. This is for the reverb IC

In the fx loop I always use an Line 6 M13 (reverbs, delays, modulations) so since you said the higher the slew rate the better, I guess if I find an IC for the fx loop with a higher slew rate will I achieve better quality fx? the fx in the Line 6 are already digital, so rising the slew rate of the fx loop IC will improve digital quality line 6 fx?


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Thu Jun 08, 2017 7:21 pm
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A good chip will improve the quality of the effects loop. The loop has a true bypass, but when active, it switches in the IC as a buffer.
So it will make everything routed through the loop sound more articulate .
I wouldn't use a faster chip than the TLE2072. Instabilities can arise with the sensitivity. The board and component layout becomes critical and oscillations can occur if its not perfect. You don't get much more bang for your buck. The prices go up quickly.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Sat Aug 12, 2017 2:30 pm
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TimsAudio wrote:
A good chip will improve the quality of the effects loop. The loop has a true bypass, but when active, it switches in the IC as a buffer.
So it will make everything routed through the loop sound more articulate .
I wouldn't use a faster chip than the TLE2072. Instabilities can arise with the sensitivity. The board and component layout becomes critical and oscillations can occur if its not perfect. You don't get much more bang for your buck. The prices go up quickly.



Hello Tim

I'm back, I've been busy making plans to leave this country. This country is falling into pieces literally......... But getting back to topic, this time cleared my mind for know what I'm looking for with the mods. I understood clearly the advantage of the higher slew rates in the TLE2072 either for the fx loop and reverb. I decided to wait for a cousin who will bring that IC for me. Meanwhile I soldered a pair of opamp sockets to make easier its installation when I'll receive the waited TLE2072. Again and again I'll repeat all my gratefulness for all your unconditional support. If you let me, in this time I will like to make you 2 questions, one is very very easy and the other is kind of complicated.

- You said in the previous post that the fx loop of this amp has a true bypass when its not active. So I could deduce that with the amp turned off I could remove the TL072 from U1 (leaving U1 without IC) and put it in place of the cheap U2 reverb IC, then turn on the amp without using the fx loop and benefit from the added agility of the TL072 and get a better reverb. That meanwhile I receive the TLE2072. I'am right, is that dangerous provided that I wouldn't use the fx loop?

- I'm turning my Hot Rod Deville in a chameleon. I have pedals to make it sound as a Marshall (Dirty Little Secret and Plexidrive), to sound as an Orange (Monarch), to sound as fender tweed (formula 5), and to sound as aVox (liverpool). As you know all this amps has different eq curves, some have a mid hump more pronounced, other are flatter. So here I go (I hope I could explain well). Since the Hot Rod series are known to have a mid hump instead of the scooped mids of other fenders, when I'll use for example the Monarch pedal (which meant to sound as and orange amp) this pedal will impart lot of mids to the sound and that with the mid hump my Hot Rod Deville already has that will be too much mids, same with marshall pedals kind of sound. Instead when I'll use the Liverpool pedal (which meant to sound as a Vox) this one will impart even mids, more neutral, but with the humped mids of my hot rod will make the final sound not as voxy. Ok, i hope I achieved to explained myself right. Ok here comes the complicated question.

If I tell you I want to put a toggle switch to my amp of 3 positions, position 1 to make the amp with scooped mids, position 2 to flatten mids and position 3 with the stock preamp since the Hot Rod has its natural humped mids. What will you tell me? that I'm crazy and will get all the guys of this forum crazy too :lol: or that will be possible? I know that technically that will require 3 different preamps, but at some extent within the limitations could playing with the slooope resistor R12 and mid pot C6 values get me close to my goal, or should I look somewhere else? maybe two toggle switches?


I hope you don't feel like wasting your time, because I have applied all your advices with great success.

P.D: I got perfectly your 2.2uF C1 recommendation and understood the importance of leveling the bass, I realized is way too pronounced, and your approach to achieve the more neutral bass at 6 in the knob make much sense, and even more for the goal I'm looking for, since I need a more control from a stock Deville to a flatter or neutral Deville.

Thank you once more.

Alberto Garcia
Caracas-Venezuela


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Sun Aug 13, 2017 8:29 am
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Yes, you probably can pull the effects loop ic. I'm not sure if there will be a hum from an open audio trace though.

Most of the voicing of the HRDX comes from the preamp. The main stage at the Power Amp in jack has a very flat response.

So instead of plugging into the input jack and compensating for the preamp voicing, plug into the Power Amp input with those pedals. That way, their true nature can come through. It will, of course, need that ic installed.
I think adding switches and lengths of wire on the tone stack circuitry would invite unanticipated problems.


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