Blackface Fender Amp Mod - Pulling V1 for more Gain?!?! Fact or Fiction
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- เผยแพร่เมื่อ 28 ส.ค. 2024
- If you have a Fender Blackface AB763 style amp you may have encountered a mod where you pull the V1 tube for a little more gain and oomph to your tone. It disables the Normal channel, but that's a small price to pay for tonal glory! In this video I try to walk through what exactly is happening in this mod and how it affects the amp. I also include some tone clips for comparison.
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You're technical explanations are excellent! Thank you!
Nice demo and explanation. I prefer V1 in, to me it sounds sweeter. This was my experience too every time I have tried it on my fender BF or SF amp.
just pulled the V1 from my Super Reverb, wow what a difference!
I pulled V1 and V5. Amp is much quieter. It is now a great pedal platform. If I desire vibrato I use a pedal. Now, no ticking or thumping. It is an early 80s DR with pull boost circuit but I don’t use the boost.
Instantly subscribed 1 minute into the video
It's okay middle pickup, you were with us in spirit.
Love this guys face when he’s playing haha
Thanks for this excellent video! The difference was subtle but clear.
I agree.
Well explained. But I have always preferred the NORMAL channel for tone.
I hear the bass boomier and the higher notes warmer with v1 out
A slight bit of a fuzzy edge with V1 out.
At 5:40 I need to clarify. The second gain stage on both the normal and vibrato channels share a single cathode bias resistor of 820 ohms. When both tubes are active the resistor passes twice the current, splitting its efficiency between both tubes. So each channel sees 1640 ohms of resistance. By pulling V1, the vibrato channel now sees the stock 820 ohms - which biases the tube hotter than normal.
Does doing this affect how "hot" things get in the power stage? (I.e. say one had a really hot bias and pulled v1, is this going to make the power stage tubes wear faster?)
@@slartbarg Hot bias can affect tube longevity. This mod mostly affects the preamp tubes, which are a fair bit more resilient in my experience. So overall I believe it is a relevant factor, but one with minor effect.
@@KleyDeJong that was my inkling too, thanks :)
well done sir :). great info vid
Honestly, I know everyone raves and SRV's tech, and on and on, but I just think this mod adds fizz, not so much the kind of gain I want and achieve with high output pickups.
Diaz was not what you think he was......he took a MAIL ORDER correspondence course on electronics as he lived on the island of PUERTO RICO......he didn't go to a real school with hands on learning. THINK MAIL ORDER PREACHER ! So when you research him and view his interviews and what he posted publicly ....he even mentions he took a mail order course .....so I am not making this up ! You have to keep in mind of the era......there was war time draft and peace time draft......Uncle Sam would have sent you to electronics school to service military equipment....and when you go out of your hitch of duty...you might just continue on in electronics or go on to do something else in civilian life. Thats one rational example....otherwise yes there were US mail based correspondence course AND RCA SCHOOL. There were other physical schools where you did hands on learning...meaning they exposed you to the meters and scopes and taught you how to use them and then apply that to work. SO visualize a MAIL COURSE and no tools or meters and scopes....& no hands on....BOOT CAMP ! >>>its a shame he is dead and I'm not trying to knock him......but he was bull crap.
To understand the BS.....if he was a trained electronics person...he would have gone in to the amp and did the proper thing which would be to separate the 2 channels where they do not share a common cathode resistor........that was a carry over from the 1950's tweed amp style as a cost cutting measure in building...meaning less parts and slightly less space in circuit board for those parts...a resistor and a capacitor bypass. In the tweed amps sharing the cathode resistor.....the 2 channels are interactive....and not fully separated......when they were supposed to be fully separated and independent. Fender circuits were not always perfect...there were some design defects that were electronic mistakes that slipped through. Leo wasn't an engineer nor a guitar player...he was a radio repairman that essentially took the amplifier section from radio's to repurpose to a PA amplifier for public presentations.....speech....., and then applied it to music performance. The early 1950's Fender amps had a microphone channel and an instrument channel......it was a band PA and not really a dedicated guitar amp
Have you experimented with changing the amp from being cathode biased to having fixed bias, and vice versa? Most tweed amps are cathode biased.
I have not tried that on this amp. I have a few other amps (5E3 cakepan, SE 7W Plexi) that are cathode biased. I tend to prefer running adjustable fixed bias as I prefer how it sounds and that I can dial in the bias exactly how I want more easily.
TBH it sounds weaker and flatter with V1 out
Just get a plexi!
why not make both channels sound better and more usable? in v2 i recommend an rca or a ge for an american tone and at v1 you can have a mullard i63 which will sound more like a bassman great for drive and single coils. enjoy!
Hey Kley!
I have a 1965 Vibrolux Reverb. When I’m playing the Vibrato channel with my Gibson R9 past 5 on the volume channel the bass gets lost and becomes flubby and I get some loud notes and crackles jumping from the speakers when playing at the higher frets(bass notes mostly). Ive tried different rooms, tubes and the voltages and speakers seems great. Is the character of the amp with humbuckers? How can I fix it?
Try putting an EQ or a tube screamer in front of your amp (to remove some of those subs that are overloading your amp).
where is heavy metal sound of increasing gain? i only hear lows increased
High gain tends to have several cascading gain stages and lots of eq filtering of both lows and highs. The tone stack tends to be more aggressive as well.
I think a lot of high gain album sounds have big low end because of how the bass is mixed. But I don't know a lot about metal production.
I have a Fender PA 135 I'm wanting to convert to a amp. I am a Metal player and I'm wanting to mod it to have a High Gain channel. How would I go about doing that?
you want this as a do it yourself situation or do you want it done for you ? A Fender PA amp is a great platform for conversion though you have the 135 model which is different than the 100 watt version. The 135 was the last incarnation when they went to the use of ultra-linear design which is ok for HiFi but not the same as the old amps which were known for the tone......the ultra-linear series amps use too high of a plate voltage for a 6L6.....though they work. It has to do with tube life and reliability. CBS era engineering interference ruined the designs and made them more HiFi which means clean and not the classic old tonality or the pre-CBS era which was much richer and gave up that special magic for a guitar. SO if you are playing metal....???
what is nice about a PA amp is that it has 4 channels but has basically the power and output transformers of a twin reverb which is 2 channel. If you are a Metal Head, the standard was the Marshall JCM 800 series amps. The 800's were still basically the old Marshall copies of the tweed bassman but the 2nd channel was not present as a feature on the front panel.....it remained internally as it was a cascaded situation in the pre-amp....the whole sound was based on the pre-amp. Pre-800 amps were being modified outside of Marshall to the One Wire MOD where they cascaded one channel into the other to significantly boost the gain of the guitar signal. The basic MOD in the old Marshalls was just running a jumper wire to connect the 2 channels which would have been in PARALLEL....cascading the 2 channels is a SERIES situation. The PARALLEL scenario means the power amp section of the amplifier is being hit with 2 signals at the same time and they are in phase with each other (which is important) and the result is a thicker response than just using a single channel...the amp will sound fatter and more robust. The series situation will boost the gain up sky high and its difficult to control it from going squealy and being UN-MUSICAL.....so the gain staging needs to be correct and you need good tubes in that part of the circuit. SO when you look at a JCM 800...it has a high gain input and a low gain input and you can't really use a AB box foot switcher to toggle back & forth as the jacks are switching jacks on the front panel of the Marshall JCM 800's.....
I hate to say it but the single simplest solution is to drive it with a good metal pedal. I understand Mesa and Dumble used fender amps as their starting points. If you really want to make it a metal amp, look into cascading gain stages. You may have to divide the output from one stage to the next to minimize blocking distortion. I think Duncan Amps gets into some good information. Another possibility is to find an amplifier you want to have yours sound like and get the schematic to use as a reference. I know this is maybe late I. The game but worth a thought. It is often much easier to purchase what you are after than to make it. There are also a ton of kits these days as well.
Dose this work with the reissues?
yes
this mod is safe for AA964 as well?
It won't work with a Princeton as it only has one channel.
@@KleyDeJong I have a Vibrolux
@@Matan2222222 Yes then that will work just fine.
@@KleyDeJong 👍🔥
will this make the amp louder?
Yes by a very small amount.
The tone was fatter with v1 out.