Tone compare vs Boogie please

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RichM
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Re: Tone compare vs Boogie please

Post by RichM » Fri May 15, 2015 10:04 pm

Well I tried comparing the Stu Pre into my Hellcat (NOS Tungsram) EL84 section vs the (NOS Sylvania) 6L6s on the Roadhouse and was quite surprised how different they sounded. I guess I kinda assumed the power sections would sound broadly similar but the EL84s have quite a bit less bottom end and more prominent upper mids - maybe this is the 'chimey' tone everyone talks about. Anyway, whilst I can fiddle with the 5 band on the Stu Pre to compensate, the more natural tone comes from the Roadhouse 6L6 power section which I guess is probably to be expected seeing as Marks run 6L6s in general.

Anyway whilst I am still really happy with the 'Cat, the Mesa is so flexible with the 5 band and you can dial in the main gain structure with the other controls and then just shape the EQ balance without messing with the tube OD - genius. I am tending to run the Treble near 10 (read that you should treat it more like your guitar's tone control), bass near zero to get the tightest bottom end - then boost the low end back again with he 5 band to balance the overall eq. Works really well.

R.

SabbadiusUSA
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Re: Tone compare vs Boogie please

Post by SabbadiusUSA » Thu May 21, 2015 7:42 pm

IMO, EL84's are best served to a NMV circuit. I really liked the Hellcat, but a lack of bottom-end in any MV amplifier is a no-go for me. In the past, EL84's haven't been the best choice for use in conjunction with a master volume circuit. That being said... Boogie, Guytron, and Diezel each make a great sounding EL84 MV amplifier. I still prefer NMV... :cool:

I loved my Hellcat at first, but then discovered that I missed that bottom-end bloom of large bottle valves... Golden Dragon EL34's are stellar in my RK100! I actually prefer them over my SED 6L6 and SED EL34's.

RichM
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Re: Tone compare vs Boogie please

Post by RichM » Fri May 22, 2015 7:28 am

Interesting - thanks.

Well my Hellcat isn't going anywhere - it provides something different to the StuPre->RH30 and now I know that both the StuPre->HC and the RH30 Pre->RH30 Pwr are less satisfying ... I have two great and unique setups!! I am still rather shocked at how good the Studio is - i think the HC design puts too much bass through the gain valves reducing the tightness and clarity a bit. The Petrucci (and everyone else) trick of setting bass near zero (and treble near 10) on the Studio then boosting some bass back on the graphic eq, gives noticeably better definition. I will dig out some circuit diagrams and compare at some point.

R.

RichM
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Re: Tone compare vs Boogie please

Post by RichM » Fri May 22, 2015 7:46 am

I'm no expert but taking a look the daigrams I have, the HC has the tone stack after V2 (with V1a/b and V2a/b providing the main gain stages) and before V3a/b that runs the FX-loop. By comparison, the Boogie has the tone controls between V1a and V1b so that V1b (shared) plus V3a and V3b (lead) and V2a or V2b (depending on channel) stages are all post EQ. Looks very different..... hmmm

R.

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Re: Tone compare vs Boogie please

Post by SabbadiusUSA » Tue May 26, 2015 12:43 am

RichM wrote:Interesting - thanks.

Well my Hellcat isn't going anywhere - it provides something different to the StuPre->RH30 and now I know that both the StuPre->HC and the RH30 Pre->RH30 Pwr are less satisfying ... I have two great and unique setups!! I am still rather shocked at how good the Studio is - i think the HC design puts too much bass through the gain valves reducing the tightness and clarity a bit. The Petrucci (and everyone else) trick of setting bass near zero (and treble near 10) on the Studio then boosting some bass back on the graphic eq, gives noticeably better definition. I will dig out some circuit diagrams and compare at some point.

R.
The excessive bass (bottom-end gain) comes from the 2.2uf cap across V1a cathode resistor. See schematic... Suspecting that Martin designed the Cornford circuits using a Fender Stratocaster loaded with single coil pickups, I asked Wally; "Is Martin primarily a Strat player?" Wally replied; "Yes, he is." The 2.2uf cap sounds fantastic using a Strat, but not so good (to my ears anyway) when using hotter humbuckers. The .1uf bass cap in the tone stack is excessive, but can be minimized by running the bass level at 0 (1) value.

Solution...
Replace the 2.2uf bypass cap with a 1uf cap. This will increase clarity by lowering bottom-end, frequency specific gain. Replace the .1uf tone stack bass cap with .047uf MKT radial cap. Try the 1uf cap mod before replacing the bass cap... Taste with your ears! :thumbup:

The ideal mod: Dual cathode bypass cap select switch. 2.2uf for single coils / 1uf for humbuckers. You can also increase the cathode resistor value to 1.8 to lower the V1a biasing.

Image
Last edited by SabbadiusUSA on Tue May 26, 2015 12:54 am, edited 3 times in total.

SabbadiusUSA
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Re: Tone compare vs Boogie please

Post by SabbadiusUSA » Tue May 26, 2015 12:47 am

RichM wrote:I'm no expert but taking a look the daigrams I have, the HC has the tone stack after V2 (with V1a/b and V2a/b providing the main gain stages) and before V3a/b that runs the FX-loop. By comparison, the Boogie has the tone controls between V1a and V1b so that V1b (shared) plus V3a and V3b (lead) and V2a or V2b (depending on channel) stages are all post EQ. Looks very different..... hmmm

R.
Yes... Boogie amps are based on Fender topology.

RichM
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Re: Tone compare vs Boogie please

Post by RichM » Tue May 26, 2015 6:42 am

Very interesting ... so in terms of the bypass cap, what would you recommend as the mod - a pull switch on a control pot to put another 2u2 cap in series lowering the total to 1.1u maybe? Or would you switch between a 2u2/1.8k and the 1u/1.5k together? What caps would you recommend for this job ... seems pretty easy.

RichM
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Re: Tone compare vs Boogie please

Post by RichM » Tue May 26, 2015 4:49 pm

By the way ... I don't find the bass works with single coils ... if anything my singles have more low end thump and the reduced clarity is therefore more noticeable than my 'buckers. If this cuts bass through the gain circuit then feels more like a 'tight' switch... is your suggestion re the bass cap intended to add more bass back later??

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Re: Tone compare vs Boogie please

Post by SabbadiusUSA » Tue May 26, 2015 7:29 pm

RichM wrote:Very interesting ... so in terms of the bypass cap, what would you recommend as the mod - a pull switch on a control pot to put another 2u2 cap in series lowering the total to 1.1u maybe? Or would you switch between a 2u2/1.8k and the 1u/1.5k together? What caps would you recommend for this job ... seems pretty easy.
Set it up however you want... Experiment. Just make sure the caps are situated in proper polarity. I would go 2.2/1.8 or 1/1.5 so to switch to stock setting. You could even go 3-way using a .68uf capacitor. I would contact "Kell" for detailed technical Q&A.

SabbadiusUSA
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Re: Tone compare vs Boogie please

Post by SabbadiusUSA » Tue May 26, 2015 7:44 pm

RichM wrote:By the way ... I don't find the bass works with single coils ... if anything my singles have more low end thump and the reduced clarity is therefore more noticeable than my 'buckers. If this cuts bass through the gain circuit then feels more like a 'tight' switch... is your suggestion re the bass cap intended to add more bass back later??
The lowered V1a cap value cuts bottom-end gain in the preamp, with minimal, to no effect of the midrange and top-end. A .047 tone stack capacitor alters the audible mids/highs by lowering 0 (1) value setting audible bass. Both mods lift bass, which is why I mentioned that you should check the output before changing the tone stack capacitor. It is likely, you will not want to augment the bottom-end EQ of a Hellcat amplifier.

My mods are geared toward lifting bottom-end gain/bottom-end EQ from MK and RK circuits, but the same could apply to the HC as well. I've never felt that the HC needed gain-stage modifications. The only issue I have found in some HC amplifiers, was some instability in the reverb circuit, which created excessive compression. The reverb circuit runs in parallel, so pull the V5 value, and play your HC amp... Do you hear any improvement?

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