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[87vetter]

Does anyone have any experience with these projecs for a 100 watt amp? Sounds interesting but I have not come across anyone that has built them. How do they sound ? 

[teemuk]

The power amp is the good part of that design (it’s better than most discrete power amps of even commercial amps).

The preamp is – sorry to say it – kind a pathetic. If you only like clean sound (and use pedals or rack gear for all effects) you might live with it assuming the tonestack response suits you (tweaking it is easy too) but anything deviating from that territory is a big bottleneck.

Personally, I’m pretty disappointed that a knowledgeable guy like Rod Elliot decided to go with the old-fashioned way of thinking that if folks need distortion let’s just slap a few clipping diodes to the signal path. It just doesn’t work like that. The preamp gain stages in that design have a very broad bandwidth (3dB point at approximately 40Hz is ridiculous for guitar amp) so you basically get clipping at the full bandwidth. It will sound fuzzy and farty and you definitely can’t do any modern lead/rhythm tones with that sort of circuit.

I also pretty much dislike all designs that try to marry the clean and OD channels. Those two tones usually need a separate voicing to work well. OD generally needs a smaller bandwidth (a great reduction of bass before clipping and then some high frequency reduction after it). Cleans usually benefit from a greater bandwidth. The tonestack voicing of both types of tones usually needs different settings too.

The preamp is way too limited in those regards. You can actually find way better designs even from those cheapish 10 – 15W practice amps and they usually don’t sound too great either due too much simplicity. Rod seems like a knowledgeable guy when it comes to HiFi designs and alike but guitar amp design obviously isn’t his main forte.

However, for Rod’s defence I must say that he seems to have designed the clipping diode thing – not as an OD channel – but more like as a rough preamp signal amplitude limiter that tries to prevent even harsher power amp overdrive. But nevertheless, this obviously isn’t a preamp that could provide decent hi gain – or even hard rockish – tones. If you need broader soundscapes than just clean tones – and want to achieve them with the amp – that preamp isn’t going to cut it. It’s a sterile preamp with fuzzy overdrive characteristics.

[87vetter]

Good information teemuk, this now raises the question what would be a good project Solid State Amp for home practice and maybe gigs ?

[ENGR BUGO aka DimebuGG]

I think the diodes are there to create an overdrive especially at high volumes. Yes it does. I think Rod was just lazy to create two channels and it is clearly stated that if a fuzz or overdrive is not needed, those clipping diodes can be omitted.

[J M Fahey]

Hi Friends.
Basically, yes, I agree with you in general.
Anyway, trying to get into Ron´s mind,what I see is that he does not want to get an Electronics "Nobel Prize", but rather, he´ll be very happy to see that people *actually* build his designs.
The added fact that he sells the PCBs, of which he tantalizingly shows component side pictures, but never the underside (much less the actual track artwork) seems to confirm this.
All his designs are minimalistic, but work.
I still can´t believe his compressor !!: 2 jacks, 1 lamp, 1 LDR ....!!!
His high quality HiFi amplifier? : 1/2 of a 5532 per channel, 1 LM3886 gainclone, 1 input selector, lonely volume pot.
Anyway I´m sure it works and sounds very good.
I think his guitar preamp is as basic as possible, with a tonestack ripped from classic Fenders, single clean channel, you-supply-the-pedals philosophy.
I agree that the output clipping diodes are not a "distortion" per se, but probably a way to *somewhat* mimic the effect of using the amplifier at high volume.
I think that building up front someting as simple as an MXR Distortion+ or a Rat will make it usable.
Bye.
J M Fahey

[troublerat]

I'm new to this forum but i am a member of diystompboxes. In defence of elliot sound products I ave actually built several of his designs. The clean pre-amp in question here being the most recent. It does clean very well [yes I tried the clipping diodes but was not the sound I was looking for]  I am not fond of just sticking some diodes on to the end of a circuit especially after having built some of the fet emulation circuits at arons site. Anyway I had the pre-amp in a case when I came across the 6watt sstpa1517 design. This will finish my 6watt practise amp. I am putting an effects loop after the pre- and before the power amp. The other projects include some of those parametric eq designs. But alas so many circuits so little time.

[imike24]

ok

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