Fender HotRod Deluxe II

The Hotrod, my first real guitar amp is often disdained for its distorted sounds. These voices come across the net - but by looking closely, it comes clear that this amp is one of the most popular and most reliable amplifiers with a certain cult status.

This LTD Edition has a Celestion Vintage 30 speaker - which could be taken as an improvement. I liked it right away. The HRD gets loud very quick, clean sound works anyway and the drive channel with the linear master potentiometer is kind of hard to adjust. But you can also use it at home.

It is often said that you can play the power amp "hot" (turned up) with a volumebox (i.e. pedal) in the FX loop ... that is nonsense. The volumebox is just a log potentiometer, that "replaces" the master potentiometer in this case - therefore, you have a few OPs more in the signal path.

Attention in the plans, there are three versions of the HotRod - this is the Hot Rod II. The 1996 plan is no longer correct -. I have not found the right plans yet and the circuit differs significantly. But you can take the new plan from 2010 (Hot Rod III), which is online. They changed only 4 parts.

• Treblepoti changed in 2010 to 250k lin instead of 250kA30
• Since 2010 the Master is a 100k log instead of a 100k lin
• C23 was reduced in 2010 to 540p 0,0015u
• C11 was raised from 390pF to 1n in 2010.

My changes

Sometimes less is more. The result is highly appreciated by the test players. The clean sound is more transparent and can be controlled better, the overdrive crumbles no longer, but it's not Marshall.

1) C52-ended, so that I can test the Reverb Mod - C52 remains outside - sounds / regulates better now as hoped. I do not understand, why Fender has not changed this in version 3, the reverb was always a point of criticism in the recessions.

2) The capacitors are already the newer ones with smaller size - I think, they'll do. That's why I left them, just a little doubled. Less ripple and firmer tone should be the result, but I can not hear that. If someone asks, why I did not take the existing solder joints for the extension .. .they are serially provided as the 500V for the HotRod Deville are not sufficient.

3) Tone stack: C7 are now 390pF (250pF), C5 47n (100n) and C6 continues 22n, R12 is 100k (130k), the traditional Fender value.

The new C5 cuts the bass in the range below 50Hz to remove the unpleasant bass. The new C7 and the Slope R15 allow more mids. I left the mid potentiometer as it was - it's installed like in a Marshall or a Bassman. You can not just reduce R15 to 33k, in the Bassman / Marshall there is a cathode follower before the tone stack, which has far-reaching consequences.

Everything in the middle, the red line is the modification

http://www.duncanamps.com/tsc

Taking back the mids you have the curve almost as before, but without the deep bass that bothered anyway.

4) The two 5W resistors R78 / 79 are replaced and placed on top - for safety - here lurks a standard error of the HRD.

The clever trick with the 330 Ohm is wrong and has the opposite effect - also Fender does not recommend it (I read).

5) C1 has 47u standard. Everything passes, but the bass has to be a bit cropped to avoid "muffling". I have tested one coupled to the channel switching version, but that's not necessary. 10uF is a value that suits.

6) Poti 250k (15A) for master. Success as hoped. The master volume is now well adjustable and the sound has also changed, since the 390pF now swallows much more highs (corresponding to the 1n / 100k proportion in HotRod III). This is also a very important change.

7) C11 replaced by SilverMica with same value - Voodoo.

8) BIAS:
Fender writes in the diagram 60 mA (mV at 1 ohm). My amp was set to 66mA. On the Internet, the value 68mA is often called. According to my simple calculations, the favorable range is between 70 and 96mA. I'll take 80mA, which is enough. The blue bias potentiometer can be clearly seen - measuring point is on the board of the tubes the leftmost, front soldering spot - it's even labeled. At the output tubes (pin3), 430V at each should be present .
Good video: http://www.eurotubes.com/euro-Fender-HRDV.htm

9) reduced C23 to 1n. This affects the distortion sound. On the web, you can often find the advice to go higher, even to 22n to. More logical is to reduce the value, Fender goes down to even 540p with the new HotRod.

Preamp tubes:
In V1 a 5751 or even a 12AY7 is not wrong. A little less gain in the input might make the sound much more open. Otherwise I would not mess around. Be sure to check using the Input 2, if the guitar has strong pickups.