Anybody know anything about Kinder harp amps and mods?

[Steve A.]

I just heard a harmonic player use their Anti-Feedback+ box the other day- it gave him a very exaggerated Paul Butterfield, et al sound. I'm asking about that box in the Effects forum, but am wondering if anyone here is familiar with the Kinder amps and mods? I get the impression that they are more than the normal harp mods (revoicing the gain stages, etc.) and possibly add anti-feedback circuitry:

http://www.kinder-instruments.com/

Thanks!

Steve Ahola

[MWJB]

I don't know what you mean by "more" than the "normal" harp mods? A lot of the guys that build/mod amps for harp have very different ideas about what works for them/the ideal harp tone. Other than bigger input loads (one well known builder doesn't even seem to bother with them), I'm not sure that there are that many "common mods" that you would find on harp amps from different builders/tweakers.

Players too can have pretty fixed ideas on what works for them. Someone who has predominantly been listening to players using fixed bias 4X10" amps might not be knockd out with a cathode biased amp for stage work...and vice versa.

There are some mods that Gerald Weber published, some of which I & other tweakers have found very useful, so thanks to being in the public domain, some of these are widely used (but generally a million miles from what Kinder is typically doing).

Kinder is very protective of his designs & not really one to share his ideas, then again his products are unique so why would he? I have seen posts where various people have theorised on what Kinder's AFB tricks are but I'm pretty sure that these are purely speculative.

However, from what little I do know about Kinder's amp mods (to existing models), he doesn't appear to majorly revoice with different cap values, altered voltages etc.- more tweaking the stock circuit for more crunch & less feedback, selected tubes etc.

Additional anti feedback circuitry as such is not a feature of his basic amp mods.

His Harpking 4x10" & 6x10" amps however are purpose built, with "anti-feedback" built in to the amp's circuitry.

The AFB+ box is an in-line device, designed to be used in front of any amp (within reason) to reduce feedback & thicken tone. I know a couple of guys who have them and are very impressed with them, they allow you to play pretty well as loud as you need (obviously it affects tone to some degree but that's to be expected) . At the end of the day, if you want one you may as well go to Kinder.

Most harp players I know use relatively subtly modded Fenders (no AFB), some will ONLY use stock Fenders. If you can't get the Butterfield sound with a 545 & a Super Reverb (loud enough for most live situations) you never will. Not that it's that easy to sound like Butterfield...

[Steve A.]

I don't know what you mean by "more" than the "normal" harp mods?

Just extra circuitry like the Anti-Feedback+ box. Would that be anything like the anti-feedback processors for PA's?

Thanks for all of the information about Kinder!

Steve Ahola

[Rob S]

Been in the sun Steve?

I remember a mate made something like this a few years ago for Paul Lamb, I'll ask him when I see him if it was something unique or a tried and tested 'frequency shifter'.

He made a few bob selling them to folk who loved the sound IIRC.

Rob.

[MWJB]

I really don't know what the in-line antifeedback box entails (for the price of the box you could get a pretty extensive mod to your amp to make it more harp friendly), I do know that it must work on a different principle to the Harpking's on-board antifeedack because of that circuit's placement in the amp, it's effect cannot be replicated by a device in front of the amp. I've got an HK on the bench at the minute but please don't ask me to divulge his secrets (not that I could easily anyway due to the PCB construction), whilst I believe in sharing info and I'll gladly bore anyone to tears with what I think makes a geat harp amp, I wouldn't be comfortable going behind Kinder's back knowing how protective he is. However I will say the on-board AFB specifically is probably not as complicated as people might think and once you set it to it's 'optimum' setting that's about it, the HK's volume is as much due to it's power supply & transformers. The 'mid bass cut' is a much more elaborate circuit, if you like what it does. I 'accidentally' built a broadly similar amp (without Mid bass cut & UB controls) years ago, based on a BF twin chassis.

Rob, I don't think that Paul (or another guy I know who owns one) uses that antifeedback device much anymore, not on domestic gigs with his own amps anyway (maybe abroad with pick up gear?). He's heading much more for a "stock" amp sound these days...he makes most of the sound himself through his technique, he gets a lot more volume out of an amp that most people can.

[Sock Puppet]

Rob, I don't think that Paul (or another guy I know who owns one) uses that antifeedback device much anymore

You may well be right there, he would swap you a six inch lead for a four inch one and used to change valves in the middle of a gig!

That went down well...

[Steve A.]

I really don't know what the in-line antifeedback box entails (for the price of the box you could get a pretty extensive mod to your amp to make it more harp friendly), I do know that it must work on a different principle to the Harpking's on-board antifeedack because of that circuit's placement in the amp, it's effect cannot be replicated by a device in front of the amp. I've got an HK on the bench at the minute but please don't ask me to divulge his secrets (not that I could easily anyway due to the PCB construction), whilst I believe in sharing info and I'll gladly bore anyone to tears with what I think makes a geat harp amp, I wouldn't be comfortable going behind Kinder's back knowing how protective he is. However I will say the on-board AFB specifically is probably not as complicated as people might think and once you set it to it's 'optimum' setting that's about it, the HK's volume is as much due to it's power supply & transformers. The 'mid bass cut' is a much more elaborate circuit, if you like what it does. I 'accidentally' built a broadly similar amp (without Mid bass cut & UB controls) years ago, based on a BF twin chassis...

I wasn't asking for any proprietary secrets, but just a general explanation of how the stand-alone or on-board AFB works, since I could find no technical details on the Kinder website.

Or is that information top secret, too?

Steve Ahola

[Enzo]

I don't know anything about these particlular amps, but anti feedbacks pretty much fall into several categories. Notch filters, active dynamic filters, and pitch shifters. SOme amps just have a few broad EQ switches to tame certain freq bands. I am seeing more and more box mixers with active anti feedback circuits.

[MWJB]

Although Kinder describes his on-board antifeedback as "a Kinder exclusive circuit" it is in fact a circuit that already exists in almost every amp of this kind of power output, "AFB", with respect to the Harpking, is just a "Kinder exclusive acronym".

Any savvy tech/builder would at least build this facility into the amp as a fixed value, without even being aware that they were doing it! Turning the on-board AFB to "0" actully increases feedback over what may be considered a "stock" circuit. Once you set it to the optimum setting, you can't really go any higher due to degredation of tone...it is handy to have that kind of adjustment at your finger tips, though most seem to be able to live without it.

The outboard AFB may well incorporate one of Enzo's suggestions, but as far as the on-board version goes, once you call it "antifeedback" people's minds go into overdrive and they start 'overcomplicating' the issue.

Kinder seems reluctant to even share useful information with his customers!

The Kinder exclusive controls on the amp are useful if you need a little help, but set it clean and you can get a bell-like tone. In short you could build a pretty useful approximation of the amp simply by using the information that presents itself naturally by looking at the controls, speakers and transformer specs. Even without the Kinder exclusive controls you can aproach the Harpking's volume/tone. If you experimented a bit with OT's & speaker loads there are even improvements to be had.

A couple of tips for Harpking users:

ALWAYS give your amp a few minutes after throwing the power switch, before throwing the standby. KT88 & KT90 take a good while to start drawing current and there is very little headroom on the main & screen filters caps, throwing the standby to soon gives them a hammering.

The stock EH KT90s are not particularly great sounding tubes. My friend tried some EIs and immediately prefered the tone...unfortunately here in the UK, there is only one vendor selling the EIs and they have appalling matching & quality control issues. He's rejected 2 sets after as many gigs...well less as one pair failed mid set. So KT88s may be the best alternative for both models. Avoid the Sovtek (too dry/aggressive), EH are passable, Shuguang are OK, SED are OK. I haven't tried JJ but some owners have given good reports. The "power" quoted for both models is more of an "on paper" figure than a "real world" figure and you shouldn't suffer a noticeable power loss. In fact, you can even run 6L6/5881 if you make sure to check your bias - the Sovtek 5881 sounds good, but may struggle to push 6x10" (I've been testing with a 4x10" cab). If you upgrade the screen grid resistors to 1K 5W Sovtek 6550 WE would also be an option.

Set your primary tone/vol & presence controls then dial in the AFB gradually. Once you get to the point that gives you good volume & tone before feedback then think about maybe the UB and Midbass Cut. If you go too heavy handed with the AFB to begin with, you'll never be able to get fidelity no matter how much you adjust the other controls. You can tell when you've overdone the AFB - you get unpleasant additional harmonics, phasey sounds and the amp can "drag", almost like a slow vibrato, when hit hard. Once you've found the sweet spot you may as well keep it right there.

The Harpking has relatively little negative feedback, this helps make it cut and appear loud, but if you find your amp too aggressive and hard edged try piggy backing a 15K to 12K on to R41. If this makes the amp too dull, just snip it off again.

[Roberto Lasco]

You can tell when you've overdone the AFB - you get unpleasant additional harmonics, phasey sounds and the amp can "drag", almost like a slow vibrato, when hit hard.

hummm...sounds like an overbiased amp...
is that AFB a bias pot ??

[Chris / CMW amps]

Not really helpfull but:

While servicing his already modded ProReverb a customer did also bring his Kinder amp. Truly great for harp but no "put all controls on 5 or 6 to start with amp" in his opinion.

Only two Kinder amps in Europe afaik but I didn't get to chance to reverse-engineer it.

[MWJB]

I know of 4 Kinder Harpkings in UK & Switzerland alone.

I had the chance to draw up a schematic and apart from the midbass cut, there really aren't any "revalatory" features.

How far you can turn up the AFB will vary from amp to amp, some amps it will be 3, others it might be 7. Turn it too far and things stop working, you can't just dial in as much as you want (e.g. turn every amp up to 5 or 6).

All that said, they are easy to set up quickly and are punchy, a big benefit to harp players who are used to struggling with less than ideal amps.

[Chris / CMW amps]

Hi

The owner did tell me he did know about the one in Switzerland.

When he got the amp he did start playing without reading the manual and he told me that after reading the manual he did get better results.

No pun ment regarding Kinder in any way!!!

[dl5mhk]

I wasn't asking for any proprietary secrets, but just a general explanation of how the stand-alone or on-board AFB works, since I could find no technical details on the Kinder website.
Or is that information top secret, too?

Hi Steve,

i'm new here...are located in Germany. I had a phone talk with John about 6 months ago, and he wouldn't tell me the principles of the AFB circuit - but i asked him for giving me a direction to think. He said: 1. It's not a filter, and 2. i should think about the difference how a guitar and a harmonica produces their tone.

I found no conclusion, finally, and choosed another way for reducing feedback: In my Alligator amp i'm using low gain and big speakers surface - it's a 12AT7 for 2 gain stages and a 2nd 12AT7 for the PI, followed by a Vox-AC30-like power section (4x6BQ5 w/o NFB loop).
Speakers are 6x 8" ceramic Jensens.

Since then i never experienced feedback, even at really loud gigs. And even then i had friends telling me "your harp is too loud, man!".

There's a short sound sample an youtube:
http://www.youtube.com/watch?v=qzzzRtFIadI

Btw i modded my Peavey Classic 30 according to your files at the blueguitar website, sounds great now! No nfb, cathode bias, changed the overdrive channel to the Fender circuit, stripped the first preamp to Fender...really great now.

cu,
Ralf