Buffers - what's going on?

Beexter

I've recently purchased the new Flashback 2 delay from TC Electronic and have come across an issue that I haven't before concerning buffers.

When I engage the pedal, there is a significant volume boost, even with delay level control at minimum. This was with the internal dip switch on the pedal set to true bypass.

I tested the pedal straight into a Yamaha THR10 with a 10ft cable from pedal to amp and a 3ft cable from guitar to pedal. I also ran the 10ft cable straight from guitar to amp as a comparison. The volume and tone sounded the same whether I went straight to amp or through the pedal with the pedal off. If I engaged the pedal, the volume was noticeably louder.

Switching the internal dip switch to buffered bypass keeps the volume levels the same whether the pedal is on or off but, even when the pedal is off, the volume is louder than plugging straight into the amp.

I checked this with TC customer support  ( who were quick to respond and gave a detailed reply) and they said this was normal and is all to do with impedance.

I always knew buffers had an impact on high-end tones but wasn't aware they impacted on volume too.

Is volume boost a fundamental part of buffer circuits or is it down to the design of the individual buffer circuit how much boost the designers build in?

Ro_S

yep, true bypass v's buffer affects impedance.  buffers don't all act the same.

Modulus_Amps

Ro_S said:

yep, true bypass v's buffer affects impedance.  buffers don't all act the same.

there are good buffers and there are bad buffers, but true bypass is not all its cracked up to be either

Sporky

In engineering terms a buffer is a unity-gain device with flat phase and frequency response that presents a very high impedance to the previous stage, and a very low impedance to the output stage.

So it shouldn't make things louder or quieter, and it shouldn't make things bassier or trebblier or middier. However, in an electric guitar setup a buffer first in the chain may well result in more treble making it from the guitar to the next stage.

ICBM

What TC said. It sounds like the amp's input is a bit too low an impedance and is lowering the volume when the guitar is straight in or the pedal is true-bypassed. The buffer will fix this.

Beexter

ICBM said:

What TC said. It sounds like the amp's input is a bit too low an impedance and is lowering the volume when the guitar is straight in or the pedal is true-bypassed. The buffer will fix this.

Interesting - I hadn't even considered the amp's input impedance. I'm going to try it into my valve amps now... (i don't usually run pedals into the THR)
Thanks to all for the comments. 

ICBM

Beexter said:

Interesting - I hadn't even considered the amp's input impedance. I'm going to try it into my valve amps now... (i don't usually run pedals into the THR)

At a guess it won't do it with the valve amps. Most valve amps have an input impedance of 1Mohm, which is high enough not to load the guitar significantly. The specs for the THR don't give the input impedance, but if it's only as low as 100K it will make a noticeable difference.

stickyfiddle

I wonder if this is partly why people often say the THRs aren't great with pedals?

professorben

stickyfiddle said:

I wonder if this is why people often say the THRs aren't great?

Ftfy

Beexter

Well, I've just tried it into my Mesa Express 5:25+ with both a Strat and Music Man Axis SuperSport and exactly the same issue as above - when the pedal is in buffered bypass mode, there is a noticeable volume bump compared to the signal straight into the amp whether the pedal is on or off. Stick it in true bypass mode and there is a noticeable volume bump when you engage the pedal. This is all at low bedroom volumes.
I s'pose it could eliminate the tap dance when it's solo time....
I'll have to experiment with it in a chain of pedals...

stickyfiddle

professorben said:

stickyfiddle said:

I wonder if this is why people often say the THRs aren't great?

Ftfy

Shut it Mr “low gain suxx”!  

stickyfiddle

^^ that was meant to be a tongue it smiley. Not mr grumpy plectrum. Hrmph

ICBM

Beexter said:

Well, I've just tried it into my Mesa Express 5:25+ with both a Strat and Music Man Axis SuperSport and exactly the same issue as above - when the pedal is in buffered bypass mode, there is a noticeable volume bump compared to the signal straight into the amp whether the pedal is on or off. Stick it in true bypass mode and there is a noticeable volume bump when you engage the pedal. This is all at low bedroom volumes.

If it's not the amp, it sounds like either the buffer is in fact giving a volume boost (ie is poorly designed) or there's a fault with the cable between the pedal and the amp which is acting as a lower impedance.

Unless the cable is definitely faulty, the best solution is just to use the pedal buffered.