[bagwell359]

Get the speedball in and do the resistor mod with toggle switch the mod only cost about the same as a coffee to implement and the E80cc will sound even better running on the correct voltage.

I have that mod and it works great.

 

[bagwell359]

Excellent! Thank you.

Google 6BL7 - although I personally haven't used it, a couple plugged into an adapter in the 6080 spot is supposed to compare favourably to a 5998. It apparently lowers the output impedance in a similar way. There's probably some info in the thread even.

Promising but not at all a match with the E80CC which I'm never giving up. So it's back to the domino plate Tung Sol 5998 - which one is for sale outside of US right here on HF.

 

[Dawgfish]

The TS 5998 is one of my favorites for the BHC.

 

[steve468]

Promising but not at all a match with the E80CC which I'm never giving up. So it's back to the domino plate Tung Sol 5998 - which one is for sale outside of US right here on HF.

I'm curious what you saw that said the tubes don't match. Do the tubes' characteristics take the circuit too far off it's operating point? Does the mod to use the E80CC make the 6BL7 not work properly?

 

[bagwell359]

I'm curious what you saw that said the tubes don't match. Do the tubes' characteristics take the circuit too far off it's operating point? Does the mod to use the E80CC make the 6BL7 not work properly?

edited for clarity: Both of those tubes require the Speedball mod for best results - in fact I wouldn't use either without it.

Within that the resistor mod for the E80CC is 470 Ω, and the 6BL7 is 115 (or near that). Also a 6BL7 pair uses more power from the transformer than its spec'd for which could be an immediate issue for transformers near the edge, or long term issues later.

The correct pairing for best sonics would appear to be the 5998/421/2399 and either the E80CC (aka 6085) Tungsram best, Amperex also very good OR 6SN7.

One note on the E80CC it is more accurate with less HD than the 12AU7. I very much prefer the lively much more defined E80CC than the soporific HD drenched 12AU7. You would still never confuse the E80CC with an SS amp - more like a hybrid. The gain is higher so you can't use it IMO with the stock volume pot - you'll get the channel mistracking fighting very high gain at low settings.

The 6SN7 doesn't need the resistor mod just an adaptor. I reckon after I get the 5998 I'll have to try the 6SN7. With the 6SN7 the 6BL7 appears to be a good match (but more research needed to be sure).

BTW, verify for yourselves stuff I wrote here. Don't just go by my reading of the net. Only the E80CC and the 470 Ω resistor switch have I done myself - with a basic 6080.

 

[steve468]

edited for clarity: Both of those tubes require the Speedball mod for best results - in fact I wouldn't use either without it.

Within that the resistor mod for the E80CC is 470 Ω, and the 6BL7 is 115 (or near that). Also a 6BL7 pair uses more power from the transformer than its spec'd for which could be an immediate issue for transformers near the edge, or long term issues later.

The correct pairing for best sonics would appear to be the 5998/421/2399 and either the E80CC (aka 6085) Tungsram best, Amperex also very good OR 6SN7.

One note on the E80CC it is more accurate with less HD than the 12AU7. I very much prefer the lively much more defined E80CC than the soporific HD drenched 12AU7. You would still never confuse the E80CC with an SS amp - more like a hybrid. The gain is higher so you can't use it IMO with the stock volume pot - you'll get the channel mistracking fighting very high gain at low settings.

The 6SN7 doesn't need the resistor mod just an adaptor. I reckon after I get the 5998 I'll have to try the 6SN7. With the 6SN7 the 6BL7 appears to be a good match (but more research needed to be sure).

BTW, verify for yourselves stuff I wrote here. Don't just go by my reading of the net. Only the E80CC and the 470 Ω resistor switch have I done myself - with a basic 6080.

Thanks for that. I do remember that there's some great discussion of 6BL7 compatibility on the Bottlehead forums, from the main guys themselves (who are INCREDIBLY helpful, and know that circuit inside and out). I reread that after I asked that question, and their recommendations basically mimic yours. In essence - be careful with anything not stock!

 

[GPJ7]

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[bpiotrow13]

And the new story begins it has just arrived

 

[bagwell359]

FTR, today I soldered in some sockets on the speedball boards that allow me to easily plug in or unplug resistors from R1 on the small boards (old Speedball). Three different resistance values are used to run E80CC (470 ohm), 12BH7A (113 ohm), and 12AU7/6SN7 (235 ohm). I didn't have the exact values and so used a combination of 470 and 150 ohm resistors. I came across this socket method using a Vista Audio phono preamp and it worked great. Anyway, just wanted to provide an alternate method of dealing with these resistors. The transistors were changed to more robust ON MJE5731AG for use with 12BH7A.

https://www.amazon.com/dp/B01MTGHZMB?psc=1&ref=ppx_yo2ov_dt_b_product_details

Yes. Switches esp little ones to fit near the board are going to require turning the amp over to switch or wired to a spot where you can flick them easily.

I had a PS pre amp where you could change the resistor value for the cartridge gain. Very easy to use and needed for all MC and some MM cartridges. Thanks for reminding me.

Formula to combine resistors:

Parallel:

Rtot = R1 x R2 / R1 + R2

So your combo is 113.7 if the resistors have 0 error. That's right there.

Series:

Rtot = R1 + R2

 

[GPJ7]

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[bagwell359]

Digikey has a nice resistor calculator for series and parallel:

https://www.digikey.com/en/resource...rsion-calculator-parallel-and-series-resistor

Nice, but there are ones that just give the results without the commercial angle.

 

[GPJ7]

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[bpiotrow13]

Work in progress

I am satisfied with the result (especially given i am not a technically skilled person), though painting the transformer end bell is a bit challenging. I have ordered the black one

 

[jonathan c]

Work in progress



I am satisfied with the result (especially given i am not a technically skilled person), though painting the transformer end bell is a bit challenging. I have ordered the black one

Now that is a transparent amp!

 

[bpiotrow13]

Now that is a transparent amp!

Ha, ha i have always hated transparent sounding amps. I need to finish this BHC so that it is not so transparent